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Distribution And Transport Of Suspended Matter, Santa Barbara Channel, California
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Distribution And Transport Of Suspended Matter, Santa Barbara Channel, California
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; l i i 72-17,466 DRAKE, David Edward, 191+3- DISTRIBUTION AND TRANSPORT OF SUSPENDED MATTER, SANTA BARBARA CHANNEL, CALIFORNIA. University of Southern California, Ph.D., 1972 Marine Sciences | University Microfilms, A XEROX Company, Ann Arbor, Michigan THTS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED DISTRIBUTION AND TRANSPORT OP SUSPENDED MATTER, SANTA BARBARA CHANNEL, CALIFORNIA by David Edward Drake A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (Geological Sciences) January 1972 U N IV E R S ITY O F S O U T H E R N C A LIF O R N IA T H E G R A D U A TE S C H O O L U N IV E R S IT Y PARK LOS A N G E LE S , C A L IF O R N IA 9 0 0 0 7 This dissertation, written by David. .MwarJ.. Drake............ under the direction of h.Xs... Dissertation Com mittee, and approved by all its members, has been presented to and accepted by The Gradu ate School, in partial fulfillment of require ments of the degree of D O C T O R O F P H IL O S O P H Y Dean Date L ^ FHSFX. . 1 . ? . 7 . ? . DISSERTATION COMMITTEE CONTENTS Page LIST OP ILLUSTRATIONS......................... vi ABSTRACT ..... ............................. 1 INTRODUCTION .................................... 5 General statement ......................... 5 Test a r e a ................................. 8 Acknowledgments ........................... 15 METHODS .................................. 16 General statement ............... ..... 16 Discussion of methods ..................... 24 HYDROGRAPHY.................................... 29 Borderland circulation ..................... 29 Santa Barbara Channel..................... 31 Surface temperatures and salinities . . 31 Surface water transparency ............. 53 Surface current velocities ............. 61 Subsurface circulation .... ........ 62 Vertical water movement and basin water recharge ..... ................... 63 Nearshore and shelf circulation .... 64 Wave-induced near bottom currents . . . 85 Summary of channel hydrography ............. 86 ii Page SOURCES OP SUSPENDED PARTICULATE MATTER .... 89 General statement ......................... 89 Cliff erosion............................. 90 Wind transport............................. 90 Biologic contribution ..................... 91 Stream contribution ....................... 92 Current transport into the Channel ........ 94- FLOOD SEDIMENT.................................. 96 General statement . . . ................... 96 Flood sediment magnitude „ ................. 98 Santa Clara R i v e r ..................... 99 Ventura River ......................... 99 Santa Ynez River and northern drainage systems ......................... 100 Northern Channel Islands ........... . . 100 South slope of the Santa Ynez Mountains 101 Flood sediment texture ..................... 102 Initial deposition of flood material .... 105 Flood layer distribution: May-August 1969 . 113 Flood layer distribution: February-June 1970 ...................................... 116 Flood layer distribution: July 1971..,* . . . 121 Flood layer and subsurface basin sediments . 125 iii Page DISTRIBUTION OP PARTICULATE MATTER ............. 135 General statement ......................... 135 Surface distribution: Preflood ........... 136 Suspended matter: January-February 1969 . . 138 Suspended matter: May 1969 144 Suspended matter: July-August 1969 .... 154 Suspended matter: November-December 1969 • 162 Suspended matter: February 1970 ........... 167 Suspended matter: October 1970 171 Summary or the surface distribution of suspended matter.......................» 182 SUBSURFACE PARTICULATE MATTER DISTRIBUTION . . . 185 General statement ......................... 185 Particle maxima and water stratification . . 187 Particle distribution: Insular ridge and mainland shelf ........................... 198 Central Channel profiles and Channel cross- sections ................................. 222 Near bottom particulate matter ............. 256 Combustible particulate matter near the bottom.............................. 275 Bottom nepheloid layer thickness .......... 280 TURBID LAYER PLOW AND THE ORIGIN OP THE BOTTOM NEPHELOID LAYER ........................... 288 iv Page General statement ......................... 288 Turbid layer transport ..................... 290 Origin of bottom nepheloid layer .......... 301 SUMMARY AND CONCLUSIONS ....................... 307 Hydrography ....................... 307 Suspended particulate matter ............... 311 REFERENCES...................................... 319 APPENDICES...................................... 329 Appendix A: Station locations ............. 330 Appendix Bs Flood sediment discharge . . . 3^0 Appendix C: Suspended sediment data .... 3^6 v LIST OP ILLUSTRATIONS FIGURE PAGE 1. Location and bathymetry of Santa Barbara Channel .................................. 9 2. Drainage basins near Santa Barbara Channel.................................. 12 3. Electrical schematic for the beam transmissometer ......................... 18 4. Optical schematic for the beam transmissometer ......................... 20 5. Scatter diagrams of percent transmission and total particulate matter concentra tion .................................... 22 6. Temperature and salinity to 200 m in 1954, Santa Barbara Channel............. 33 7. Surface temperatures in May 1969 .... 35 8. Surface salinity in May 1969 37 9. Surface temperatures In July 1969 .... 39 10. Surface temperatures In August 1969 . . . 41 11. Surface temperatures in November 1969 . . 43 12. Surface temperatures in December 1969 . • 45 13. Surface temperatures in February 1970 . . 47 14. Depth to 15° C Isothermal surface in November 1969 ........................... 49 15. Surface transparency in May 1969 .... 54 16. Surface transparency in November 1969 . . 56 17. Surface transparency in February 1970 . . 58 vi FIGURE PAGE 18. Dissolved oxygen along a vertical east- west section in May 1969 65 19. Distribution of phosphate in a vertical section in May 1968 ..................... 67 20. Temperature-salinity relationships in May, August and December of 1969 .... 69 21. Surface current patterns from drift card surveys of May-December 1969 73 22. Surface transparency in December 1968 . . 77 23. Transparency values at 50 m in February 1970 81 24. Transparency values at 90 m in February 1970 83 25. Flood layer thickness in March-April 1969 106 26. Surface transparency in January 21-23* 1969 109 27. Flood layer thickness in May-August 1969 114 28. Flood layer thickness in February-June 1970 117 29. Flood layer thickness in July 1971 . . . 123 30. Lithology of piston core 11270, Santa Barbara Basin ........................... 127 31. Surface transparency and suspended matter from January 30 to February 1, 1969 . . . 139 32. Vertical profiles of light transmission over Ventura Shelf on February 1, 1969 . 142 33. Suspended particulate matter at the surface in May 1969 ..................... 1^5 34. Phytoplankton productivity at the surface in May 1969 ............................. 1^7 vii FIGURE PAGE 35* Ash residue and inorganic particle weights at the surface in May 1969 . . . 149 36. Suspended particulate matter at the surface in July 1969 ................... 155 37. Suspended particulate matter at the surface in August 1969 . . ....... 157 38. Ash residue values at the surface in August 1969 ............................. 160 39. Noncombustible particle weights at the surface in August 1 9 6 9 ........... 163 40. Suspended particulate matter at the surface in December 1969 ............... 165 41. Surface transparency in October 1970 . . 172 42. Surface temperatures in October 1970 . . 174 • • «Mi. 43. Depth to the 12° C isothermal surface in October 1970 ........................... 176 44. Transparency values at 20 m in October 1970 .................................... 178 45. Transmissometer and temperature profiles, Santa Barbara Channel............. 189 46. Vertical section of light transmission in November 1969 ....................... 192 47. Transparency values at 60 m in November 1969 .................................... 194 48. Vertical east-west section of light transmission in July 1971......... 196 49. Vertical profiles of light transmission and temperature in November 1969 .... 200 50. Vertical profiles of light transmission and temperature over Ventura Shelf in February 1970 ........................... 202 viii FIGURE PAGE 51. Profile of light transmission over Ventura Shelf, February 1970 204 52. Profile of light transmission over Ventura Shelf, October 1970 ............. 206 53. Light transmission values in vertical meridional section over Ventura Shelf, November 1969 ........................... 208 54. Light transmission values in vertical meridional section, central Ventura Shelf, November 1969 ........................... 210 55. Light transmission values in vertical meridional section, Goleta to Santa Cruz Island, November 1969 ....................... 212 56. Light transmission values in vertical meridional section, central Channel, November 1969 ............................... 214 57. Light transmission values in vertical meridional section, Point Conception to the insular ridge, November 1969 .... 216 58. Light transmission values in vertical section, Ventura Shelf to south of Point Conception, February 1970 .................. 218 59. Profiles of light transmission, south- central Channel, October 1970 .............. 223 60. Profile of light transmission, central Channel, October 1970 ....................... 225 61. Profiles of light transmission, tempera ture and salinity, central Channel, July 1971 227 62. Light transmission values in vertical meridional section, Pitas Point to insular ridge, October 1970 ................ 236 63. Light transmission values in vertical meridional section, October 1970 .... 238 ix FIGURE PAGE 64. Light transmission values in vertical meridional section, Goleta to Santa Cruz Island, October 1970 240 65. Light transmission values in vertical meridional section, Gaviota to insular ridge, October 1970 ........................ 242 66. Light transmission values in vertical section, Point Conception to insular ridge, October 1970 ........................ 244 67. Light transmission values in vertical latitudinal section, Ventura Shelf to south of Point Conception, October 1970 . 246 68. Light transmission values in vertical section, eastern end of Santa Barbara Basin, July 1971 248 69. Light transmission values in vertical meridional section, Santa Barbara Basin, July 1971 ............................... 250 70. Light transmission values in vertical section, western end of Santa Barbara Basin, July 1971 252 71. Suspended particulate matter 1 m above the bottom, July 1969 .................. 259 72. Suspended particulate matter 1 m above the bottom, August 1969 ................ 261 73. Suspended particulate matter 1 m above the bottom, November 1969 ............... 263 74. Suspended particulate matter 1 m above the bottom, December 1969 ............... 265 75. Suspended particulate matter 1 m above the bottom, February 1970 ............... 267 76. Light transmission values 1 m above the bottom, October 1970 .................... 269 x FIGURE PAGE 77. Ash residue 1 m above the bottom, August 1969 276 78. Ash residue 1 m above the bottom, Febru ary 1970 278 79. Bottom nepheloid layer thickness versus depth.................................... 281 80. Depth to 9° C isothermal surface, October 1970 285 81. Temperature at the bottom in May 1969 . . 296 82. Temperature at the bottom in October 1970 298 xi TABLE PAGE I. Filter tests............................. 26 II. Flood sediment d a t a ..................... 103 III. <62u total mineral composition .......... 130 IV. <2u total mineral composition .......... 131 V. Water column stability ................... 283 VI. Turbid layer f l o w ....................... 293 xii ABSTRACT The Santa Barbara Channel was selected as a test area to determine the distribution of suspended particulate matter, its relationship to water structure and circula tion, and the processes and rates of transport of fine detritus near the continent. Beyond the mainland shelf, surface water circulation is dominated by currents entering the area through the western and southeastern passages. Northwest flow from Santa Monica Basin occurs during all seasons but varies in volume transport in response to the seasonality of the Anacapa Current. This relatively warm, clear, and nutrient-poor current sweeps northwest over the outer Ventura Shelf at a mean velocity of 0.5 knots and can be followed as a distinct surface current at least to Gaviota. Suspended sediment concentrations, beam transmissometer profiles, and plankton productivity data show that this current carries, on the average, less than 0.2 mg/l in organic particles and contributes relatively little to the plant production in the Channel. The importance of this flow lies not in a significant introduction of sediment to the area but, in its hydrologic blockage of the southeast passage to southward escape of locally contributed particulate matter. A second major current within the Channel is pro duced by an intrusion of cool, low salinity California Current water from the west and southwest. Inorganic sus pended sediment concentrations range from >1.0 mg/l in a nearshore, wind-driven turbid plume rounding Point Concep tion to approximately 0.2 mg/l in the southwest portions of the area. The confluence of these currents occurs in the central Channel with the development of a permanent counter-clockwise eddy. Surface temperature distributions suggest that net flow over the inner portion of the mainland shelf from Point Conception to Pitas Point is to the east and south east and is probably a resultant of prevailing westerly winds. Circulation over Ventura Shelf is dominated by north and northwest flow over the southern portion to the latitude of Ventura. Between Ventura and Pitas Point this northerly flow converges with southward shelf currents. 1 2 The convergence results In a wedge of slack water and the turning of current vectors to the west. A second con vergence between southward inner shelf currents and the Anacapa Current is commonly observed off Oxnard. Subsurface circulation to a depth of about 250 m involves flow into the area through the southeast and western passages with the probable development of a counter-clockwise eddy in the central Channel. Below 250 m Channel water is derived from the west. The sur face and subsurface eddies in the central Channel serve to markedly increase the residence time of water and sus pended matter and, in concert with the high productivity of surface waters and the large local sources of ter restrial detritus, produce the highest rate of hemi- pelagic sedimentation Within the California Continental Borderland. Suspended particulate matter is predominantly supplied by the Santa Clara River; a turbid, largely wind- driven, plume rounding Point Conception; and spring plank ton production. Contribution of eolian sediment totals between 50,000 and 120,000 tons/year and may produce a significant reduction (10-20 percent) of surface water transparency during fall Santana wind conditions. The northern Channel Islands and the south slope of the Santa Ynez Range are insignificant sources of suspended matter for the Channel. More than 60 x 10^ metric tons of suspended sedi ment were introduced by local streams during the 1969 winter floods. Of this total approximately 56 x 10° tons were introduced to the Ventura Shelf by Santa Clara and Ventura Rivers. Sand and coarser flood detritus was deposited rapidly to form river mouth deltas and bars whereas finer products were initially deposited in a west ward trending wedge beneath the shelf current convergence off Pitas Point. Greater than three-fourths of the flood material was retained on Ventura Shelf within 20 kms of the rivers and at depths of less than 50 m. Accumulation of fine silt and clay sizes over normally silty sands strongly suggests the formation of physical grain aggre gates and accelerated settling. Flood detritus in suspension over the shelf was principally contained in a surface turbid layer which extended to the depth of the seasonal thermocline (about 20-25 m) and a more concen trated near bottom turbid layer. Particle concentrations in the surface layer ranged from >10 mg/l near the Santa Clara River to<1.0 mg/l in the central Channel. Concen trations in the bottom nepheloid layer in February 1969 ranged from >50 mg/l off the rivers to <10 mg/l at the 3 southern edge of Ventura Shelf. Within six months after the floods surface concentrations seaward of a 5 to 7 km wide coastal band of turbid water had decreased to "normal" values of <0.5 mg/l. On the other hand, the bottom nepheloid layer over the shelf remained highly concentrated owing to continual resuspension of flood material by wave surge at depths of less than 30 m and seaward transport by Anacapa Current. Owing to thermal water stratification, resuspended particles beyond a near shore zone approximately 5 to 7 kms wide were confined to the bottom nepheloid layer and to mid-water turbid layers supplied principally by the near-bottom particulate matter. A close association of subsurface particle maxima and thermal discontinuities as small as 0.1°C was observed as material was transported from the Ventura Shelf to the central Channel. Temporal reduction of the shelf flood layer initial ly occurred at the rate of about 1 million tons/month. Erosion was rapid over the inner shelf with deposition of resuspended material in protected depressions in the middle and outer shelf and within the deep basin. The concentrations of particulate matter required to initiate downslope turbid layer density flow were never reached owing to rapid initial deposition of even the finest detritus on the inner shelf and the inability of near-bottom currents to produce concentrations exceeding 10 mg/l at the shelf edge. With the exceptions of the Insular shelf and Montalvo Ridge, a bottom nepheloid layer ranging in con centration from>3 mg/l to <0.5 mg/l was found on all surveys. The thickness of this layer ranged from <10 m to >100 m and was a direct function of water depth and stratification. The pattern of flood layer deposition, bottom nepheloid layer concentrations, and the texture of sediments covering the basin slopes combine to indi cate that a significant portion of the finest fractions swept from the mainland shelf and settling from inter mediate depth particle maxima is maintained in suspension by increased turbulence and transport power near the Channel floor. Beam transmissometer profiles demonstrate scour of the bottom at the western edge of the Anacapa Trough (250 m) and over a large sediment fan forming the mainland slope south of Point Conception. Resuspension of previously-deposited fine silt and lutite to augment particle concentrations in the bottom nepheloid layer is compatible with measured currents in excess of 0.7 knots at a depth of 300 m along the mainland slope. Therefore, the permanent bottom nepheloid layer in the Channel is 4 principally supplied by particles settling from above and resuspended by current action from the bottom. Particles entering the near-bottom zone are maintained in suspension by relatively strong vertical eddy mixing. Currents below sill depth (500 m) have been measured at velocities of up to 20 cm/sec and are suf ficiently vigorous to produce a permanent "reservoir" of fine particles. Nevertheless, this material cannot escape from the basin and must represent a dynamic equilibrium controlled by vertical eddy mixing, particle settling rates, and particle supply. Consequently, the relatively coarse particles will be less influenced by turbulence and will accumulate more evenly over the basin floor. Con versely, the settling and deposition of finer material (less dense) will be retarded until transport power de creases within protected topographic depressions. Hence, there is no need to invoice lateral gravity controlled flow of suspended matter in order to explain tne topographic control of sedimentation rates. Only approximately 1 cm of flood sediment was deposited on the large fan forming the slope to the south of Point Conception. Although the fan is presently aggrad ing, the rate of sedimentation is only approximately one- third of that in the basin, and not compatible with the size of this sediment body. It is concluded that the bulk of the sediment in the fan was contributed during periods of low sea level in the Pleistocene. Whereas flood sediment thicknesses were generally less than 1 cm on the basin slopes, a layer approaching 3 cm was deposited over the basin floor. Mineralogic analys es of the <62p fractions of the flood layer demonstrate a nearly undiluted Santa Clara River source. Furthermore, comparison of the 1969 flood layer mineralogy with the average mineralogy of subsurface basin sediments reveals that grey "silt" layers which were previously identified as turbidites are flood-year deposits which accumulate relatively slowly in the years following a major flood. Inorganic basin sediments deposited in non-flood years, although still predominantly supplied by Santa Clara River material washed from the Ventura Shelf, exhibit an increased dilution by other sources. Although these sources cannot be specified, it is probable that the dilutant is derived from the turbid surface and subsurface plumes rounding Point Conception and from currents flowing into the basin over the western sill. INTRODUCTION General Statement Although silt and clay particles comprise more than two-thirds of the sedimentary record and the overwhelming bulk of recent marine sediments, processes of suspended load transport are not well known. Undoubtedly, the dif ficulties encountered in sampling and quantitatively analysing minute amounts of material have impeded re search. Equally to blame is the belief that beneath the wind-driven surface layers of the ocean, currents are sluggish and largely incapable of accomplishing much geologic work. Within the past decade direct current measurements at abyssal depths and circumstantial evidence from the form and nature of bottom deposits have confirmed the existence of deep currents which, at times, must approach the velocities of surface waters (Heezen and Hollister, 1964; Kolpack, 1968). Complementing this evidence is the discovery that suspended particle concentrations increase markedly near the bottom in many oceanic areas (Jerlov, 1953a; Timofeyeva and Neuymin, 1968; Eittriem and others, 1969; Ewing and Connary, 1970; Pak and others, 1970a; 5 Carder and others, 1970). Turbulent energy must be ex pended to maintain such suspensions. Among the suggested causes of the bottom "nephe loid" layer are bottom sediment resuspension, "high" density turbidity currents, and "low-density" flow of near-bottom suspended matter from continental shelves to abyssal depths (Ewing and Thorndike, 1965; Eittriem and others, 1969; Spencer and Sachs, 1970; Moore, 1969). The last hypothesis is of considerable interest to marine sedimentologists in southern California in that Moore (1969) invoked this mechanism for fine sediment transport into the enclosed basins of the Borderland. In addition to the realization that considerable sediment reworking may occur at abyssal depths (see, for examples, Johnson and Johnson, 1970, and Le Pichon and others, 1971), sedimentologists are finding that transport processes cannot be fully reconstructed from analysis of the final deposits (Swift and others, in press). Pine particulate matter does not move directly from source to final deposition but follows a complex path involving stages of transport, deposition, erosion, and further transport before ultimate burial. During transport the detritus is commonly in the form of organic-inorganic and inorganic-inorganic aggregates (Parsons, 1963; Osterberg and others, 1964; Revelle and Shepard, 1939; Calvert, 1966); the size distributions, settling characteristics, and composition of these biological or physical aggre gates are, upon deposition, beyond recall. Recent interest in suspended matter in the sea has been spurred by marine geochemists and biologists involved in studies of the chemistry of particle-water interactions and the role of particulate detritus in the food chain (Parsons, 1963; Armstrong, 1958; Mackensie and Garrels, 1965; Spencer and Sachs, 1970; Menzel and Vaccaro, 1964). The research described herein was planned with the following considerations and objectives in mind: 1. An obvious gap exists between nearshore and estuarine work and research in the deep ocean. Since the continents are the ultimate source of nearly all inorganic detritus in the sea, it is felt that suspended sediment research logically should proceed from the continental shelf sea ward. In particular, little information is available on the paths followed by fine sedi ments moving across the continental shelf and especially the rates of transport. 2. The factors controlling the distribution of particles in the sea are poorly known. Con sequently, a principal objective is description of particle distributions and transport mechanisms. In this regard, the transport mechanism proposed by Moore (1969) received special attention. 3. Prom the pioneering work of Jerlov (1953. 1968) it appeared that much information on the hydro graphy of nearshore waters could be obtained using the natural tracer properties of sus pended matter. 4. It was hoped that a budget of suspended sedi ment could be developed for a portion of the Continental Borderland. Such a budget would yield needed information on sediment input, by passing, and deposition. Test Area The area selected for this research is Santa Barbara Channel at the northern end of the California Continental Borderland (Pig. 1). This area presents a number of attractive features which simplify study of the suspensate system. First, the Channel contains a variety of bathymetric features including mainland and insular shelves, basin slopes and basin floor, shallow and deep sills, and ridges and troughs. Secondly, the largest river along the southern California coast (in terms of mean annual runoff) terminates at the eastern margin of the Channel and provides an abundance of terrestrial detritus. Furthermore, the basin waters below 500 m are nearly anoxic and the bottom sediments are chemically Figure 1 Location map showing bathymetry of Santa Barbara Channel (after Environmental Sciences Service Administration Bathymetric Maps 1206N-15 and 1306N-20). 9 120 3 0 1 2 0*00' 119* 30' SANTA 34* 30' noutlcol ml. SANTA B A R B A R A # : ■ISO bothymttry In m tlsrs ^Sjftfctft-VEN TUR A .pt 100- -^■00'— — ' kJggM 11140s SANTA CRUZ ISLAND 34* 00’ 34* 00* so- SANTA ROSA ISLAND r-\ 120*30* 11 reducing. This situation prohibits the development of viable benthic communities of macro-organisms; in the ab sence of bottom burrowers an undisturbed record of sedi ment accumulation is preserved (Emery and Hulsemann, 1962). Finally, the presence of the Channel Islands Ridge greatly eases the task of "closing" the area and monitoring input and outflow of water and sediment. Channel bathymetry and the major land drainage systems are shown in Figures 1 and 2. Noteworthy bathy metric features are the mid-channel ridge trending 290°T toward the basin from the Ventura Shelf. Seismic re flection profiles demonstrate that this ridge is the topo graphic expression and seaward extension of the "Montalvo" anticlinal trend near Oxnard (Vedder and others, 1969). Following Weaver and others (1969) this ridge will herein be called Montalvo Ridge. The troughs formed to the north and south of this feature are of particular importance to sediment dispersal. A second anticlinal trend is topographically ex pressed by a low, narrow ridge extending west from Rincon Point to south of Santa Barbara where it terminates at a depth of about 60 m. Although this ridge is only a few meters above the general shelf surface, this is sufficient to prevent significant fine sediment accumulation. The fan-shaped rise forming the slope south of Point Conception should be noted. Seismic reflection Figure 2 Major drainage basins near Santa Barbara Channel. Area designations: SC = Santa Clara, V = Ventura, SY = Santa Ynez, SS = south slope of the Santa Ynez Mountains (after U. S. Geological Survey Water- Supply Paper, 1735). 12 I20°00' l!9o 00' 50 miles 35 o o 35 00 SY I s s ^ 34 0 0 34 0 0 14 profiles obtained in June 1970 demonstrate that this feature is largely sedimentary. Its origin will be dis cussed in forthcoming sections (see page 287). In this report reference to Santa Barbara Basin should be understood to mean that portion of the Channel below the western basin sill at 475 m. In addition, the mainland shelf between Santa Barbara and Oxnard is called the Ventura Shelf and the rectilinear valley forming the eastern sill is informally named the Anacapa Trough. The geology of the Transverse Ranges and the Channel has been adequately presented elsewhere (Bailey and Jahns, 1954; Weaver and others, 1969; Vedder and others, 1969) and will not be related here. Suffice it to say that the Channel is a thickly-filled, graben-like depression form ing the western extension of the oil-rich Ventura Basin. Although the depositional rate of non-turbidite detritus is the highest in the northern Borderland (Emery, I960), the majority of basin slope features are structurally controlled with just a thin sediment mantle (Moore, 1969). The Channel is seismically active (Hamilton and others, 1969) and tectonic displacements have, in many areas, kept pace with sediment smoothing. Even within the basin where Emery (i960) determined rates of sedimenta tion of about 90 mg/cm2/yr, depressions from 5 to 25 m below the general basin floor are present (Pig. 1). The distribution and characteristics of bottom sediments in the Channel are summarized by Stevenson and others (1959)» Emery (I960), Emery and Hulsemann (1962), and Wimberley (1964). Bottom materials are discussed in this report only when pertinent to the transport and deposition of detritus from suspension. Acknowledgments Many people provided assistance during the course of this study, from the initial formulation of the problem to the preparation of the final manuscript, and their efforts are sincerely appreciated. Special thanks are extended to Drs. Bonn S. Gorsline and Ronald L. Kol- pack of the University of Southern California for guidance, many fruitful discussions, and invaluable cooperation dur ing all phases of the study; Mr. M. Oguri of the University of Southern California, and Dr. Peter Barnes of the United States Geological Survey for assistance during the col lection of samples; and to Messrs. Paul Irving, Carl Philipi, and Captain P. Zeisenhenne and the officers and crew of the RV Velero IV. The manuscript was read critically by Drs. D. S. Gorsline, R. 0. Stone, G. J. Bakus, and R. L. Kolpack. Financial support pertaining to this research was provided by National Science Foundation Grants GA 13083 and GA 22842 and the Western Oil and Gas Association. Ship time was provided under NSF institutional Grant GB 8206. METHODS General Statement Three problems are encountered In any study of suspended particulate matter in natural waters. One must effectively describe the suspensate distribution, sample a large volume of water owing to the low particle concentra tions, and efficiently separate the finest detritus. A variety of methods have been reported (Jerlov, 1955; Banse and others, 1963; Ewing and Thorndike, 1965; Spencer and Sachs, 1970; Beardsley and others, 1970; Carder, 1970; Wildharber, 1966; Lisitzyn, in press; Swift and others, in press). In the present research the following instruments or techniques were used; 1. An in situ beam transmlssometer was initially borrowed and later a modified version was pur chased from the Visibility Laboratory, Scripps Institution of Oceanography, for the purpose of describing the spatial distribution of light attenuating substances. This instrument has been described in detail by Petzold and Austin (1968). Briefly, the instrument continuously 16 records the transmission of a current-regulated cylindrically-limited beam of light which is filtered optically for maximum sensitivity at 470 nm. Calibration is achieved in air by ad justing the current on the 20-watt tungsten lamp. Data are recorded in real-time on a deck mounted Hewlett-Packard X-Y-Y* graphic recorder A simultaneous temperature curve is recorded on the Y1 channel. Pigures 3 to 5 present the essential features of the transmissometer. Water samples were recovered using a poly ethylene bucket for surface water and 7-liter Van Dorn and 30-liter Niskin non-contaminating PVC bottles for subsurface samples. Van Dorn and Niskin bottles were modified to accuate within one meter of the bottom to sample the near-bottom waters. Mlllipore membrane filters and a Sorvall supercentrifuge were used to separate particu late matter and water. Suspended matter con centrations in this report are given in terms of weight/volume. General discussions of the use of membrane filters can be found in Banse and others (1963) and Strickland and Parsons (1969) in addition to the technical information supplied by filter manufacturers (Millipore Figure 3 Schematic of the electrical circuit for the beam transmissometer (after Petzold and Austin, 1968). 18 T R J M I S S O M E T E R C I R C U I T I SILICON | PHOTOVOLTAIC CELL WATER PATH1 CALIBRATE ADJUSTMENT AMPLIFIER INTERNAL REFERENCE PATH j f — LAMP U n d e r w a t e r h o u s in g J I I METER I I | READOUT POTENTIOMETER VOLTAGE SOURCE I I I l CURRENT REGULATED ADJUSTABLE — POWER SUPPLY Figure 4 Optical schematic of the beam transmisso- meter (after Petzold and Austin, 1968). 20 TRANSMISSOMETER OPTICAL SCHEMATIC FIELD STOP v FIELD LENS OBJECTIVE LENS & APERTURE PORRO PRISM f , ' / / LIGHT PIPE / SILICON /D E T E C T O R FIELD STOP OBJECTIVE LENS & APERTURE SHUTTER WATER PATH Figure 5 Scatter diagram showing the relationship be tween percent transmission and total sus pended particulate matter. A = Data of May 1969; B = Data of November 1969 and February 1970. The relatively more gently sloping curve and pronounced scatter shown in graph A are attributed to the presence of dis solved, light-absorbing substances in the surface waters during May 1969. All data are for the surface waters in Santa Barbara Channel. 22 % T R A N S M IS S IO N /M E T E R % T R A N S M IS S IO N /M E T E R 23 80 60 40 20 T T T T T 1 IT - T ~ 111 I I I I I I A-SUMMER, 1969 • • • • • • • • . • • • • •• • • *. o • • . . * • • • • • • n u l l ! i ii i i i i i i i 50 2 0 IO 0.5 0.2 TOTAL SUSPENSATE (mg./liter) 8 0 60 4 0 20 B-WINTER, 1969 • • 50 20 L O Q5 TOTAL SUSPENSATE (mg./liter) 02 24 Corporation, 1965). Discussion of Methods The transmissometer measures the total attenuation of light resulting from scattering and absorption (Jerlov, 1968). Light attenuation in the sea varies with the scattering and absorption of the water, suspended particles and dissolved substances. All of these factors are more or less wavelength dependent. Although a calibration of the transmissometer in terms of total suspended particulate matter would be highly useful, a simple relationship was not obtained (Pig. 5). The large amount of scatter shown in Figure 5A is produced by errors in particle weight determinations and the fact that beam attenuance is dependent upon the composition of the particles (refractive indices) and the content of light absorbing dissolved substances (not measured by filtration), and not merely the particle con centration. In this regard, greater success is achieved by measuring the light scattered out of the beam at 45° (Jerlov, 1968; Beardsley and others, 1970; Pak and others, 1971) but the problem of variation resulting from particle refractive indices changes still remains. Particulate matter concentrations are usually determined by weighing of filtered or centrifuged material separated from a measured volume of sea water. The most 25 commonly used method is membrane filtration. Such filters and Inexpensive, can be obtained in a variety of diameters with mean pore sizes to O.Ijji, and are soluble in acetone (Millipore Corporation, 1965). Furthermore, the MF series manufactured by Millipore is completely combustible at 4-50°C allowing organic matter analyses. While the membrane filters offer many advantages, there are definite pitfalls that should be avoided. Fore most among these is the possibility of significant losses of particles resulting from improper selection of filter pore sizes. An excellent example of this problem was reported by Wildharber (1966). In suspended sediment re search off the Palos Verdes Peninsula he observed deficiencies of montmorillonite relative to the bottom sediments when using 0.8p mean pore size filters. In order to establish the possible magnitude of fine particle passing by 0.8p filters, various concentrations of Pacific red clay and fine sediment from the Santa Cruz Basin were filtered through 0.8p, 0.45p, and 0 ,3ji Millipore filters (Table I). The results indicate that at suspensate con centrations above about 1.0 mg/l all filters trap greater than 95 percent of the detritus. However, below 0.5 mg/l the 0.8p filters show a significant loss in efficiency. The successful separations at the higher concentrations probably are the result of pore clogging with particles slightly larger than 0.8p. Since particle concentrations 26 TABLE I FILTER TESTS Sediment type Cone. ss/.i. Filter Pacific clay 1.5 0.8/1 Pacific clay 1.5 0.45/1 Pacific clay 1.5 0.3/1 Pacific clay 1.0 0.8/1 Pacific clay 1.0 0.45/1 Pacific clay 1.0 0.3/1 Pacific clay 0.4 0.8/1 Pacific clay 0.4 0.45/1 Pacific clay 0.4 0.3/1 Santa Cruz B. 1.0 0.8/1 Santa Cruz B. 1.0 0.45/1 Santa Cruz B. 1.0 0.3/1 Santa Cruz B. 0.4 0.8/1 Santa Cruz B. 0.4 0.45/1 Santa Cruz B. 0.4 0.3/1 Trials* 1 92% 2 96% 2 95% 4 97% 9*% 98% 97% 94% 9*% 95% 95% 98% 95% 95% 95% 90% 95% 98% 94% 94% 96% 97% 94% 94% 87% 82% 90% 86% 94% 92% 96% 92% 94% 97% 92% 95% 90% 91% 96% 94% 91% 94% 98% 92% 94% 95% 95% 97% 88% 84% 87% 91% 94% 92% 90% 96% 96% 95% 99% 97% * As percent of test concentration retained by filter 27 in the sea are typically below 0.5 mg/l» the 0.8ji filters should not be used. Unfortunately, weight determinations with Millipore MF filters are subject to large non-systematic errors. In the present work it was not uncommon to find that the filter plus particles weighed less than the clean filter. The weight loss is apparently due to the use of a "sizing" material during manufacture. This source of error was minimized by pre-filtering and using two stacked filters (the lower filter acting as a blank) during particle separations. Indeed, it is doubtful that reliable weights can be obtained without using two filters for each sample. With this method it was found that repeated filtrations of distilled water and a standard suspensate sample (0.5 mg/l) resulted in a reproducibility of ilO percent. Although systematic comparisons were not made, it appeared that weight determinations with Millipore PVC filters were more precise. In the great majority of cases the weight of the blank PVC filter after filtration was virtually identical to its pre-filtering weight. However, at present the PVC series is not available in pore-sizes smaller than 0.6p and, although soluble in acetone, it does not combust at 450°C. Whereas continuous-flow centrifugation offers certain advantages over filtration, it was found that com plete particle separation was a time-consuming process. 28 The large diameter filters available from Millipore Corporation offer the most efficient means for particle separations from large volume samples. The layer of oxidized terrestrial sediment result ing from the 1969 floods was sampled with a Shipek grab, Phleger corer, and modified Rieneck box core. It was found that the Shipek grab was unreliable at depths exceed ing 100 m owing to sediment washing. Therefore, the flood layer thicknesses in the Channel in 1969 through 1971 were determined using the Phleger core and the reliable box core wherever possible. Most of the values measured in 1969 are from Phleger cores whereas about 50 percent of those in February 1970 and all values in June 1970 and July 1971 are from box core sections. HYDROGRAPHY Borderland Circulation Since 194-9 the Marine Life Research Project of the California Cooperative Oceanic Fisheries Investigations (CCOFI) has Included surveys of water properties to a depth of about 500 m over the borderland. This information pro vides an excellent knowledge of general current patterns but, owing to the wide spacing of stations, affords little insight into the hydrography of individual basins. As determined by the CCOFI surveys, the general surface circulation over the borderland is dominated by a permanent cyclonic eddy, the Southern California Eddy, situated throughout most of the year to the west of or over Santa Cruz Basin (Emery, I960; Wyllie, 1966; Barnes, 1970). The eddy is formed as California Current water passes southward into the lee created by the eastward turn of the coast along the Transverse Ranges. It is characterized by a central core of relatively cool, saline, and nutrient-rich water extending from San Miguel Island to San Nicolas Island. Dynamic topographies and direct current measurements reveal an average surface current velocity of about 0.4 knots (Wyllie, 1966). To the east and southeast of the Southern Cali- 29 30 fomia Eddy, surface waters turn to the south and flow toward Mexico such that a second, less distinct eddy, rotating clockwise, forms off San Diego (Sverdrup and others, 1942; Swartzlose, 1970). The northern extent of this second eddy appears to he limited to the area south east of Los Angeles. To the northwest of Los Angeles, offshore surface currents on the eastern side of the Southern California Eddy generally are directed to the northwest throughout the year. Seasonal variability of the borderland surface circulation is well-documented (Reid and others, 1957; Emery, I960). In the spring and summer the North Pacific High Pressure Cell is well-established and generates con sistent northwest winds which tend to drive the California Current eastward toward the coast. In the fall and winter months, this high pressure cell degenerates and splits in to two smaller highs located off Baja California and over Nevada. Winds are variable and at times blow seaward at high velocities (Santana winds) (Stevenson, 1955)* In response to the wind change the axis of the California Current moves farther offshore allowing a coastal counter- current of warm water to develop. This current, called the Davidson Current or California Countercurrent, has been detected along the Pacific coast as far north as Oregon (Sverdrup and Fleming, 1940). Subsurface water over the borderland is character 31 ized' by temperature-salinity associations which show a gradation from 100 percent "northern” water at or near the surface to 100 percent "southern" water at depth (Emery, I960). Currents at and below 200 m are, at all times, directed to the north and northwest transporting relatively saline, nutrient-rich, water from equatorial regions (Wyllie, 1966). Since the borderland generally slopes to the southwest, basin sill depths increase in this direction with the result that Individual basins are filled principally by water flowing northward over the deepest southern sill. Santa Barbara Basin is an exception to this general rule in that its deepest sill is at its western end. Therefore, the waters below about 475 m (sill depth) in the basin are derived from the oxygen minimum layer of the northeast Pacific (400-600 m). Consequently, the inflow ing basin water has an initial dissolved oxygen content of about 0.5 ml/l which, in the highly productive Channel, is further reduced to values of 0.2 to 0.3 ml/l. Santa Barbara Channel Surface temperatures and salinities Surface temperatures within the Channel reflect seasonal solar radiation changes and changes in lateral and vertical water transport. Temperature ranges from a spring minimum of about 11°C to a maximum of about 19°C in 32 the late summer (Fig. 6). The low spring temperatures extend to at least 200 m and are associated with higher salinities at all levels. From the summer maximum of 19°0 temperature decreases to an average of about 14°C in the winter. The distribution of surface temperatures and salinities in 1969 suggests that the Channel can be divided into eastern and western sectors along the longitude of Goleta (Figs. 7 to 14). Surface water in the western sector is derived predominantly from the California Cur rent directly west of Point Conception and San Miguel Is land. Warmer water in the eastern sector at all times of the year reflects the northward transport of water along the eastern side of the Southern California Eddy. Based on the more complete Channel surveys of May, July, August, November, and December of 1969 and February 1970, the following surface temperature patterns are noted: 1. The coldest waters are always to the south of Point Conception or in the southwest corner of the Channel. 2. Relatively warm water enters the Channel through the southeast passage from Santa Monica Basin (Anacapa Current). 3. With the exception of the late summer surveys, surface water in a 10 km wide coastal band along Figure 6 Temperature and salinity values to 200 m in 1954, Santa Barbara Channel. Note the pro nounced influence of upwelling which begins in February and ceases abruptly in July. Salinity values at 200 m show that vertical water transport occurs to at least that depth (after Kolpack, 1971). 33 MONTH J M M J S N S T A T I O N 8 3 . 4 3 1 9 5 4 16- 10 20 3 0 5 0 13- 10- 100 — '"-2 0 0 D E P T H = M E T E R S T E M PE RA T UR E °C 3 4.5 34.2 - 33.9 - 33.6 - 33.3 - M i M i S T A T I O N 8 3 . 4 3 N . i 33.0 1 9 5 4 200 100 5 0 1 3 0 ‘20 0 10 D E P T H M E T E R S SALINITY %• C ALCOFI D A T A Figure 7 Distribution of temperature at the surface in May 1969. Areas of pronounced upwell- ing are located in mid-channel to the north of San Miguel Island and to the southeast of Santa Barbara (see Fig. 8). 55 120*30' I20*00‘ SURFACE TEMPERATURE M A Y , 1 9 6 9 SCALE 10 nautical mi. 20 25 kilometers 119*30' SANTA BARBARA y m j l 7 13.2' 12.6 VENTURA OXNARD 2.0 2.8 34* 00' SAN MIGUEL ISLAND SANTA CRUZ ISLAND ANACAPA IS S A N TA ROSA ISLAND < 120*30' 0\ Figure 8 Distribution of salinity at the surface in May 1969 (after Kolpack, 1971). The strip of cold and saline water extending from Point Conception to the northwest tip of Santa Cruz Island is the resultant of up- welling owing to Ekman transport of surface water to the south and southwest. 37 120*30' 120*00' SURFACE SALINITY M A Y , 1 9 6 9 SCALE 10 nautical mi. 34* 30' 25 kilometers 20 SANTA BARBARA V E N T U R A 3 3.82 O X N A R D 3* O t f 34* 00’ SANTA CRUZ ISLAND SAN MIGUEL ISLAND ANACAPA IS ' SANTA ROSA ISLAND ) . 120*30’ CO Figure 9 Distribution of surface temperatures in July 1969.^ The inflow of relatively cool California Current water to the west of Goleta is well defined. Further, in creased solar insolation results in the formation of a warm lens of water over the northern portion of the Ventura Shelf. The "Anacapa Current" is poorly developed in the summer months. 39 S U R F A C E T E M P E R A T U R E ( * C > SCALE J U L Y , 1 9 6 9 0 M E T E R S S A N T A B A R B A R A STATION LOCATION 1 9 .0 . V E N T U R A • 1 9 . 6 O X N A R D 3* 00 S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D A N A C A P A IS . l S A N T A R O S A IS L A N D ; Figure 10 Distribution of surface temperatures in August 1969. Note the well developed wind-driven tongue of cold water rounding Point Conception and the extensive intru sion of cool California Current water from the southwest. The convergence between this current and the warm water flowing west from the Ventura Shelf is reflected by an accumulation of particulate matter at the sea surface. 41 120° 30' 119* 30* - 0 . 5 — SUSPENSATE ( m g / l ) 17.0 20 25 Kilometers TEMPERATURE (*C ) 34' 30' 34* 30' M E T E R S A U G U S T , 1 9 6 9 SANTA BARBARA 19.0 19.0 0 . 5 VENTURA 0 . 5 17.0 16.5 15.0 16.0 15.6 15.0 . 18.6 T810. . . 34' 00‘ 34' 00' SANTA CRUZ ISLAND SAN MIGUEL ISLAND ANACAPA IS. SANTA ROSA ISLAND 120*30' 119*30' Figure 11 Distribution of surface temperatures in November 1969. Although stations are widely spaced, the small range of tempera ture within the Channel suggests that the relative simplicity of the observed pattern is real. Note that the warm Anacapa Cur rent is well-developed in agreement with the fall intensification of the Davidson Current. 43 120*00' S U R F A C E T E M P E R A T U R E SCALE 10 nouticol mi. N O V E M B E R , 1 9 6 9 2 0 I I 9 * 3rf S TA TIO N LO CATION SANTA BARBARA 1 6 . 5 o 1 6 . V E N T U R A 16.8 1 6 . 7 1 7 . 5 O X N A R D ,1 6 .5 o 1 7 .7 S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D A N A C A R A IS , S A N T A R O S A IS L A N D ■ lifjf Figure 12 Distribution of surface temperatures in December 1969. The oval patch of cold water north of San Miguel Island had a relatively low salinity (Kolpack, 1971) and, thus, was not produced by upwelling. Note the dominance of the.Anacapa Current in the eastern and northern portions of the Channel and the restriction of the counter-clockwise eddy to the southwest corner of the area. 45 120*30' S U R FA C E TEMPERATURE D E C E M B E R . 1 9 6 9 SCALE 34* 30* 20 23 kilometers S A N T A B A R B A R A V E N T U R A 5.8 15.6; O X N A R D S« oof S A N T A C R U Z IS L A N D S A N M IS U E L IS L A N D A n a c a p a IS . S A N T A R O S A IS L A N D 120*00' ON Figure 13 Distribution of surface temperatures in February 1970. Note the tongue of 14°C water extending southeast from Point Con ception and the recession of the warm Anacapa Current. Both aspects of the distribution are compatible with the typical increase in winds from the north west during the late winter and spring. 47 120*30* SURFACE TEMPERATURE SCALE JOnouticol mi. FEBRUARY. 1970 S A N T A B A R B A R A V E N T U R A C v \ 15.6 O X N A R D 14.0 14.8 114.8 15.6 SAN UISUEL ISLANO S A N T A C R U Z IS L A N D J , 00' ANACAPA IS, 1 8AN7A ROSA ISLAND. Figure 14 Depth to the 15°C isothermal surface in November 1969. The gentle gradients and low relief of this surface indicate that surface currents are relatively sluggish. The counter-clockwise eddy of the western sector is well illustrated. 49 1 2 0 * O t f DEPTH TO 15 *C ISOTHERM (meters) NOVEMBER, 1969 STATION LOCATION S A N T A B A R B A R A . V E N T U R A 30 O X N A R D <5 S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D A N A C A P A IS . t S A N T A R O S A IS L A N D 1 2 0 * 0 ? 51 the northern Channel margin was found to be slightly colder than water farther seaward. 4. Seaward of this coastal band, the water along the north central portion of the Channel was relatively warm in May, August and December of 1969 and February 1970. Following the general rule that, in the northern hemisphere, warmer water will lie to the right of the cur rent vector, a picture of surface currents within the area can be developed. Circulation in the western sector is dominated by a counterclockwise eddy trapped in the lee of Point Conception. Warmer water flows to the northwest through the Anacapa-Oxnard Passage sweeping over the outer Ventura Shelf, and at times, extending to Point Conception and beyond. The confluence of this current, which will informally be called Anacapa Current, and the cold Cali fornia Current water of the western sector generally occurs near the basin center between Goleta and Santa Cruz Is land. The narrow band of cold water along the north coast may be the resultant of upwelling driven by prevailing winds which blow either offshore or eastward parallel to the shore (Stevenson, 1959). The observed density dis tribution should produce a slow coastal current to the east and southeast. However, it should be noted that this ap parently is not the case during late summer months. Variations in the pattern outlined above are cor- related to seasonal changes in the Northeast Pacific wind regime and the California Current system. During the fall and winter, offshore migration of the California Current allows a broader northward counterflow along the coast. However, this current never totally blocked the inflow of cool California Current water in the southwestern portion of the Channel. The summary of CCOFI data by Wyllie (1966) indicates that the California Countercurrent (Davidson Current) is poorly developed in the late summer. This may explain the extensive intrusion of California Cur rent water into the Channel during August 1969 (Fig. 10). The temperature minimum and salinity maximum ob served in May 1969 were produced by extensive upwelling of nutrient-rich subsurface water (Kolpack, 1971). Northwest winds are strongest in the spring (Stevenson, 1959)» and within the Channel wind velocities at the sea surface in crease rapidly to the west of the lee created by the Santa Ynez Mountains. Thus, during May the linear distribution of surface isotherms between Point Conception and Santa Rosa Island reflects the importance of wind-driven upwell ing :ln the southwestern portion of the area. The resulting trough of cold, saline water probably has the effect of intensifying the cyclonic eddy. Indeed, CCOPI data indicate a more vigorous surface circulation in the spring throughout the borderland (Reid and others, 1958). 53 Surface water transparency Small scale current transport problems are commonly studied by tracing the movement of artificial dye re leases. Jerlov (1953a) pointed out that the inherent optical properties of water masses can be useful in large- scale transport and mixing problems. In the present investigation the precise measurement of light attenuation proved particularly well-suited to the study of nearshore circulation where natural sediment tracer is more or less continuously added. Surface water transparencies, in terms of percent transmission/meter, are shown for May and November of 1969 and February 1970 (Figs. 15-17). The patterns on all surveys are similar with generally clear water entering the Channel from the southeast and inflow of more turbid water from the northwest. Within the Channel, percent trans mission values beautifully delineate the two principal currents defined by conservative water properties. The lateral extent and relative clarity of the Anacapa Current in November 1969 are a resultant of the combined effects of the fall season intensification of the California Countercurrent and the lack of local river run off. In both May 1969 and February 1970 relatively "pure" California Current water occupies the Channel to the south west of an imaginary line connecting Point Conception and the eastern tip of Santa Cruz Island. However, in November Figure 15 Distribution of light transmission values at the surface in May 1969. The predominant two-current surface circulation system is well illustrated with relatively warm, clear, nutrient-poor water flowing into the Channel from Santa Monica Basin and a tongue of cool, turbid, nutrient-rich water intruding from the west. The current pattern is more clearly defined by transparency than by the conserva tive properties of temperature and salinity (see Figs. 7» 8). 54 #/o T R A N S M I S S I O N / M E T E R M A Y , 1 9 6 9 0 M E T E R S S T A T IO N L O C A T IO N SCALE 0 5 >0 nouhcol mi. 1 0 t5 20 ?5 kilomettrs 3 A * 30' 119*30’ SANTA BARBARA V E N T U R A <s V i O X N A R D S q V i . A N A C A P A IS S A N M IG U E L IS L A N D S A N T A C R U Z IS L A N D . S A N T A R O S A IS L A N D - I , 120*31? 119*30* VJT V j \ Figure 16 Distribution of light transmission values at the surface in November 1969. Pro nounced surface turbidity is restricted to a 5 to 7 km-wide nearshore zone with the notable exceptions of the wind-driven tongue off Point Conception and seaward deflection off Pitas Point. 56 120*30' 120*00' % t r a n s m is s io n / m e t e r NOVEMBER, 1969 0 METERS o— STATION LOCATION 5 10 15 2 0 2 5 K ilo m e te rs SANTA BARBARA # VENTURA OXNARD <4^ ANACAPA IS. SAN MIGUEL ISLAND SANTA CRUZ ISLAND . r i * i ' SANTA ROSA ISLAND • : 120* 3 0 ' 120* 0 0 ' 1 1 9 * 3 0 ' Figure 17 Distribution of light transmission values at the surface in February 1970. Fine grained detritus introduced by Ventura and Santa Clara Rivers during the 1970 rainy season did not move directly offshore but was transported south to be entrained by the swift Anacapa Current near Oxnard. In addition, a seaward deflection of low trans parency coastal water west of Ventura is compatible with westward currents within a shelf current convergence. 58 120* 30' TURBIDITY SURFACE % t r a n s m i s s i o n /m e t e r ,34*30* FEBRUARY. 1970 SCALE 10 n autical mi. 20 25 kilomtttrs JI9*3tf S A N T A B A R B A R A 80 50 80 V E N T U R A 70 \ 60 80 O X N A R D \ V 80 30 SAN M IG U E L IS L A N D S A N T A C R U Z IS L A N D ANACAPA IS. L S A N T A R O S A IS L A N D 120*00' 60 California Current water is limited to the southwest sector to the west of Santa Rosa Island. The eastward ex tent of California Current water within the area reflects seasonal changes in the wind regime and the waxing and waning of the California Countercurrent. Discussion of the interesting transparency pattern in the eastern Channel in February 1970 is deferred to a later section concerned with circulation over Ventura Shelf (see p. 64). In summary, the Inflow of water at either end of the Channel is particularly significant to the suspended sediment system. The trapped eddy in the western sector serves to partially ’ ’block" rapid escape of water flowing westward from the Ventura Shelf. Furthermore, the reduced light transmission of the cold water sweeping around Point Conception indicates a net addition of particulate matter from the coast to the north. Runoff and suspended sediment supply by streams to the south of Oxnard is always lower than local supply from the Santa Clara and Ventura Rivers (Rodolfo, 1970; Gorsline, 1968). Thus, the Anacapa Cur rent is generally relatively clear, does not add appre ciable quantities of particulate matter to the Channel, but has the important hydrologic effect of blocking the southern escape of Ventura Shelf detritus. The net effect of the current regime is to increase the residence time of water and suspended matter within the 61 Channel. For example, if a given parcel of surface water makes one complete rotation within the trapped western eddy, its residence time is increased by 4 to 6 days relative to direct transport out of the area (this calcula tion is based on an eddy diameter of 30 km and rotation velocity of 20 cm/sec.). Surface current velocities Although no direct surface current measurements were made during the present research, it is possible to esti mate the order of magnitude of surface velocities from the drift card experiments of Kolpack (1971) and the CCOFI data summarized in Reid and others (1958). These workers con clude that mean surface velocities are in the order of 0.3 to 0.5 knots over the borderland. These data are not suf ficiently detailed to define differences in the flow velocities of specific currents within the Channel. None theless, from a consideration of bathymetry one might ex pect the Anacapa Current to be relatively swift as it passes westward through the constricted passage to the north of Anacapa Island. Sandy bottom sediments composed, in large part, of authigenic minerals in the Anacapa Trough, support this conclusion (Kolpack, personal communi cation) . 62 Subsurface circulation Sverdrup and others (194-2) and Wyllie (1966) have shown that the water at 200 m throughout the borderland flows to the north and northwest during all seasons. It is therefore reasonable to assume that flow to the west through the Anacapa-Oxnard Passage occurs at all depths. Below the eastern sill depth (245 m) , Channel water must come from the west between Point Conception and San Miguel Island. If this conclusion is accepted, it is of interest to determine as precisely as possible from where this sub surface water is derived. Inspection of CCOPI station data to the west of the Channel (stas. 80.60 and 80.55) shows that the depth to 50 percent southern water is at all times 400 m or more. However, to the south along the seaward side of Santa Rosa-Cortez Ridge, CCOPI Station 83.55 reveals 50 percent southern water at approximately the same depth as within the Channel. Thus, it is prob able that the intermediate water between 250 m and the western sill is derived from the southwest through flow around the western end of the Channel Islands ridge. It will be shown in a later section (see p. 254) that the vertical distribution of particulate matter in the western passage strongly supports an inflow of intermediate water below 300 m. While water mass characteristics provide some indication of the sources of Channel waters, there is 63 little published information on subsurface currents within the area. Direct current measurements that have been made show appreciable velocities at all depths. For example, Berger and Soutar (1968) reported currents oJ f up to 20 cm/sec just above the bottom in the deepest part of the Channel and P. Fischer (personal communication) recorded velocities of up to 35 cm/sec at '300 m along the north basin slope. A complete understanding of subsurface flow patterns must await the analysis and publication of hydro- graphic data collected by Kolpack and his associates dur ing 1969 and 1970. Nonetheless, the particle distribu tions observed during this study permit some tentative conclusions regarding general patterns of subsurface flow. These data will be considered in forthcoming sections. Vertical water movement and basin water recharge During the spring of 1969, Kolpack (1971) and Sholkevitz and Gelskes (1971) recorded a sudden increase in the dissolved oxygen content of the deep basin water. Through subsequent months the oxygen concentration de creased from 0.5 ml/l to 0.2 ml/l. Rittenberg and others (1955) from a consideration of oxygen use in the basin waters, calculated that replenishment at least every two years was required. Axial profiles of the distributions of dissolved oxygen and phosphate within the Channel in May 1969 (Kol- I 64 pack, 1971) suggest that recharge of basin water is driven by upwelling along the western sill and entrainment of deep water at the eastern sill (Figs. 18, 19). Entrainment by westward flowing subsurface currents at the eastern sill would draw basin water to the east (Fig. 19) allowing up- welled water over the western sill to flow into the basin. The extent of spring upwelling in the Channel area is shown by the t-s diagrams reproduced in Figure 20. Relative to December, the depth to 50 percent southern water in May in the central Channel had moved vertically upward approximately 200 m to a depth of about 70 m. Salinity values at 200 m, monitored monthly, show that upwelling extends at least to this depth (Fig. 6). Further more, the model of Hldaka (1961) indicates that upwelling may effect the entire water column and data presented by Barnes (1970) for Santa Cruz Basin appear to support this conclusion. Thus, intense spring upwelling in the Channel, complemented by basin water entrainment near the eastern sill, may be an effective mechanism resulting In more or less complete annual replenishment of the basin waters. Nearshore and shelf circulation The largest sources of suspended inorganic matter to the Channel, the Ventura and Santa Clara Rivers, terminate at the east-central margin of the Ventura Shelf. Therefore, circulation over this shallow, relatively wide Figure 18 Distribution of dissolved oxygen along a vertical east-west section in Santa Barbara Channel. See Appendix for station locations (after Kolpack, 1971). 65 DEPTH (meters) S T A T I O N S 13026 12972 12980 12967 13008 13017 13019 13024 0 6.0 (00 200 300 4 0 0 M A Y OXYGEN 600 Figure 19 Distribution of phosphate along a vertical section in May 1969 (after Kolpack, 1971). See Appendix for station locations. 67 DEPTH (meters) S T A T I ON S 13026 12972 12980 12987 (3 00 6 13017 13019 13024 100 200 300 4 0 0 300 600 Figure 20 Temperature and salinity relationships in May, August and December of 1969 (after Kolpack, 1971). Envelopes in the right- hand graph show that salinities throughout the Channel are relatively high in May. 69 R A T U R E o o LU CL S UJ t- S A L I N ') ' * 1 I I ) I I f ' } ■ I - 33.4 33.8 34.2 %o 71 shelf is critically important to the initial marine trans port of river-borne sediments. Trask (1955), Johnson (1956), and Gorsline (1968) demonstrated that longshore drift from Santa Barbara to Oxnard is predominantly to the south. Short periods of reversal occur during the summer and fall in response to long swell from the south, but such reversals are not suf ficient to modify coastal sediment characteristic trends. Rates of drift along individual beach segments are related to coastline orientation, offshore kelp beds, and the resulting degree of exposure to swell and local wind waves (Ingle, 1966; Kolpack, 1971). Oarplnteria and Summerland beaches are, therefore, of lower energy rela tive to Hollywood beach (10 km south of Ventura). The latter area has no protection by offshore kelp and is more directly exposed to waves from the west. For example, during the period of July 1969 to February 1970, Kolpack (1971) determined that drift rates were on the average less than 25 cm/sec at the former beaches, whereas Holly wood beach had an average approaching 30 cm/sec. Although over short periods of time the littoral currents are highly variable, it safely can be assumed that they generally fall in the range of 15 to 30 cm/sec within the Channel. The work of Hjulstr’ om (1939) indi cates that such velocities are capable of transporting particles as large as 4 mm. Thus, the swift and practical 72 ly unidirectional longshore currents result in efficient southward transport of sand contributed by coastal sources. A large proportion of this material is ultimately inter cepted by Hueneme submarine canyon and routed to Santa Monica Basin (Gorsline and Emery, 1959; Ingle, 1966). The zone of significant littoral drift probably ex tends no more than 100 m offshore (Inman and others, 1971). Seaward of this narrow band, water movements are more com plex, have been less studied, and are less amenable to adequate quantitative measurement. Although no direct current measurements were made during this study, consider able qualitative data were obtained and the results of short-term direct current measurements conducted by Shell Oil in the summer of 1967 were made available by Peter J. Fischer. Qualitative information is available from the drift card experiments of Kolpack (1971), surface turbid ity measurements, surface temperature patterns, and the depositional pattern of shelf sediments. Drift cards provide a low cost means of gathering data on the gross patterns of surface currents. Kolpack found that for all surveys in 1969 there was a long and relatively narrow clockwise eddy centered over the Ventura Shelf between Goleta and Oxnard (Fig. 21). Recoveries of drifters at sea indicated average current velocities of approximately 0.25 knots. The drift card information Indicates the permanance of the northwestward current over Figure 21 Generalized surface water currents deter mined by drift card surveys of May through December of 1969 (after Kolpack, 1971). Circulation over the Ventura Shelf is dominated by a long, narrow anticyclonic eddy. However, these data do not resolve smaller eddies or the convergence off Pitas Point. 73 119 40 120 20' 34 40' 34 4 0 SURFACE CURRENTS DIRECTION 34 20 34 20' SANTA 34 00 34 00' CRUZ., SAN MIGUEL k SANTA ANACAPA ROSA 120 40 120 00' 119 20 ! I 75 the outer shelf hut falls to resolve smaller and more variable currents over the middle and inner Ventura shelf. The distribution of surface temperatures recorded during the several Channel surveys provide a more nearly synoptic view of the mass distribution over the shelf and the currents to be expected from this distribution. Basic ally two patterns of surface temperatures were observed. The first is characterized by a patch of warm water over the northern one-third of the shelf between Santa Barbara and Pitas Point and a relatively warm tongue of water mov ing over the southern one-third through the Anacapa-Oxnard Passage (Pigs. 9 and 10). The second pattern is simply a broad tongue of warm water entering the area from the Santa Monica Basin with a bordering coastal band of cooler water (Pigs. 11-13). The patterns are seasonal in re sponse to the fall and winter intensification of the cur rent from the southeast, and the summer warming of northern shelf water and recession of the northward current. In particular, during the summer months a lens of warm water forms over the northern one-third or one-half of the shelf and rotates anticyclonically owing to the mass distribu tion. To the south another anticyclonlc eddy at times may occupy the Anacapa-Oxnard Passage and extend well up over the shelf (Pig. 10). The temperature distributions in November and December of 1969 indicate northwestward flow over the 76 middle and outer shelf with a coastal counterflow of cooler water toward Oxnard (Pigs. 11 and 12). The complex current pattern suggested for February 1970 implies a re cession of the northwestward flow (Pig. 13). Surface water light transmission patterns are compatible with the circulation suggested by surface temperatures and serve to amplify certain interesting details. A striking similarity appears, more or less well developed, in all of the shelf patterns (Pigs. 16, 17, 22); a tongue of turbid water extending westward or south- westward from the shore between Pitas Point and Ventura. This tongue denotes the convergence between northern shelf water and the northwestward current sweeping across the shelf from Anacapa-Oxnard Passage. Its presence during all seasons indicates that it is a fairly permanent shelf circulation feature which may well be the result of coast line orientation but is Intensified by summer heating of the shelf water. An especially noteworthy transparency pattern was observed in February 1970. In February, turbid water transported south along the mainland coast from Ventura was entrained by the northwestward flow passing along the outer shelf. The resulting tongue of turbid, entrained water could be detected as far west as Gaviota, consider ably diluted, but easily traced (Pig. 17). Inspection of the surface temperature distribution in February (Pig. 13) Figure 22 Distribution of light transmission values at the surface in December 1968. 77 119° 4 0 ' 1 1 9° 2 0 ' LIGHT TRANSMISSION DECEMBER, 1968 0 METERS SANTA BARBARA 34' 20' 34' 20' VENTURA 34' 34 -•100 SANTA CRUZ ISLAND 79 shows that the southwestward turn of the plume south of Gaviota Is in agreement with expected geostrophic currents. The entrainment of coastal water off Oxnard is critically important to the budget of suspended sediment in the Channel. Northwestward flow through the southeastern pas sage serves to block the escape of fine particles and in crease sediment retention in the Channel. Direct current measurements were obtained by Shell Oil Co. in 1967. A Hydro Products meter was suspended 6 m above the sea floor at a series of 15 stations along the outer mainland shelf, over Montalvo Ridge, and the upper basin slope in depths ranging from 20 m to 500 m. All data were obtained in the late summer and early fall of 1967. Current directions were predominantly northwest at 270° to 290° T over the Ventura Shelf and Montalvo Ridge during flood tide changing in a counterclockwise arc to southwest (210° T) during ebb tides. There was no con sistent trend in current speed with depth; speeds at 100 m were essentially the same as those recorded at 20 m. Average current speeds were about 0.5 knots with high velocities of 0.7 knots at flood tide and low velocities of 0.3 knots during ebb. These data indicate that the northwestward geostrophic current over the outer Ventura Shelf has an average velocity of 0.5 knots toward the northwest. The tide wave passes along the coast from south 80 to north and, therefore, when ebb flow is superimposed on the density current, water transport to the southwest re sults. During flood tides current velocities rise to 0.7 knots (35 cm/sec) and must, in concert with wave surge, produce significant shear stresses along the bottom. Material resuspended during flood tides will be trans ported to the southwest during ebb flow and, in part, deposited in deeper water as the current falls to 0.3 knots (15 cm/sec). Currents recorded along the northern shelf between Santa Barbara and Point Conception show a directional change to nearly due west with a further change in the mean flow to southwest near Point Conception. These data are in agreement with the qualitative information presented earlier and strongly suggest that circulation determined at the sea surface in the Channel may be extrapolated to depths of 100 m without introducing large error. Trans parency patterns for February 1970 at the surface, 50 m and 90 m generally support this conclusion in the eastern and northern sections of the area. However, to the south of Point Conception it should be noted that the plume of 70 percent water present from the surface to 50 m is missing at 90 m and the deep pattern suggests flow to the south west (Pigs. 23 and 24). It is reasonable to presume that the driving force for the turbid plume moving around the point to the southeast is, in part, wind stress. North- Figure 23 Distribution of light transmission values at 50 m in February 1970. The pattern de fines a number of large and small eddies but is basically similar to the turbidity distribution at the surface (Fig. 17). 81 120*30* 120*00' T R A N S M I S S IO N / M E T E R F E B R U A R Y , 1 9 7 0 5 0 M E T E R S SCALE 10 nautical mi. 20 25 kilometers •• DEPTH (METERS) STATIO N LO C A TIO N •50- SANTA BARBARA 5 0 - , . 6 5 80 fa J o „ 50 V E N T U R A 6 0 6 5 O X N A R D 60 a n A c a 'p a i s . S A N M IG U 'E k S S L A N ^ S A N T A C R U Z IS L A N D 00' '.S A N T A R O S A IS L A N D 00 120*30* Figure 24 Distribution of light transmission values at 90 m in February 1970. 83 T R A N S M I S S IO N / M E T E R F E B R U A R Y . 1 9 7 0 9 0 M E T E R S SCALE >0 nouticol ml. _20 25 kilometer* 119* 30* o— STATION LOCATION o 6 5 S A N T A B A R B A R A V E N T U R A O X N A R D ° 8 4 •o vv o 7 2 3* O f f S A N M IG U E L IS L A N D S A N T A C R U Z IS L A N D A N A C A P A IS, S A N T A R O S A IS L A N D ! 85 west winds are consistently brisk in this area but appear to influence flow only to a depth of about 50 m. It is probable that when the seasonal thermocline is well- developed considerable shear occurs as the temperature discontinuity acts as a floor to wind drift currents. Wave-induced near bottom currents Oscillating currents due to surface wave advance into shallow water can attain significant magnitudes over the continental shelf (Bagnold, 1965; Johnson and Eagle- son, 1966). It is commonly reported that the sediment in water shallower than 30 m off southern California is well- sorted sand whereas below 30 m the surface is covered in creasingly with silt and clay (Emery, I960). Some idea of the theoretical water particle velocities due to surface waves can be obtained using the equations presented by Sverdrup and others (194-2). The relevant equation is v = (2fr/T)ae“2ffZ//L where T is the wave period, a is the open water amplitude, z is water depth, and L denotes wavelength. Long waves in the Channel typically have periods ranging from 9 to 15 seconds, amplitudes of about 1 m, and computed wave lengths of 100 to 300 m. Taking an average wave train of 12 second period, 225 m wavelengths, and 1 m amplitude, the theoretical water particle velocities can be computed for various shelf depths. At bottom depths of 100 m, 50 m, 86 and 30 m the water particle velocities would be approxi mately 3 cm/sec, 13 cm/sec, and 22 cm/sec, respectively. It is concluded that below a depth of about 50 m wave surge could maintain fine particles In suspension but would not affect appreciable resuspension of deposited detritus. With decreasing depth and particularly in water shallower than 30 m wave surge becomes a highly significant energy source for possible bottom scour. In addition to water motion produced by free sur face waves, the motions of internal waves at subsurface density discontinuities can produce significant horizontal flow near the bottom (Sverdrup and others, 194-2; LaPond, 1963)* Since meaningful study of internal waves requires specialized equipment and a rather large expenditure of ship-time, their study was not undertaken. It is possible to presume from the work of LaPond (1963) and Emery (I960) that they are probably present within the Channel. Further more, LaPond reported that net flow at the bottom due to internal waves should be directed seaward across the shelf. Research to better define the magnitude of these currents would be of great interest to sedimentologists. Summary of Channel Hydrography The temperature, salinity, dissolved oxygen and nutrient contents of the surface waters change in response to spring upwelling, summer heating, and the fall and early 87 winter intensification of the Anacapa Current. Upwelling in the spring is driven by the consistent northwesterly winds generated by the North Pacific High Pressure Cell and produces exceptionally fertile surface waters in the western sector of the Channel. Surface waters flow into the Channel through the western and southeastern passages. Consequently, although the waters in both currents are of "northern*1 origin, the water from the southeast is always somewhat warmer and more saline. Surface circulation in the western portion of the Channel is dominated by a permanent, trapped cyclonic eddy. In all seasons a relatively warm current flows through the Anacapa-Oxnard Passage becoming broader in fall and winter months. Circulation over the northern Ventura Shelf is dominated by a clockwise eddy. Nearer the southeastern pas sage currents are more complex; at times water character istics suggest anticyclonic eddying over the southern portion of the shelf whereas at other times northwestward flow simply sweeps across the outer shelf turning westward at the latitude of Ventura. Current velocities are on the order of 0.25 to 0.5 knots with flood tide maxima of about 0.7 knots along the northern Channel margin. Prom approximately 80 m to 250 m the Channel water represents a mixture of "northern" and "southern" water types. Below about 250 m the water is, for all practical purposes, 100 percent southern water. Oonstriants im posed by the sill depths of 245 m and 475 m imply that the Channel water below 245 m must come from the west. Emery (1954) has shown that the basin water below 475 m is de rived from the west. Intense spring upwelling drives a vertical water movement of as much as 200 m in Santa Barbara Channel and appears to result in annual basin water recharge. Accord ing to Emery (I960) internal wave activity near sill depth may also produce some degree of continuous basin water replenishment but it is doubtful that this mechanism is as effective as the spring upwelling. SOURCES OP SUSPE NDED PARTICULATE MA T T E R General Statement In January and February of 1969 southern California experienced two heavy rainstorms. Average precipitation for the South Coastal Drainage area during these two months totalled 55 cm, approximately 40 cm above normal. Although this rainfall set no new records, it occurred with such intensity that flooding was widespread throughout central and southern California. For a detailed analysis of the 1969 floods the reader is referred to the climatolog- ical data summaries of the U. S. Department of Commerce. The tremendous runoff which followed the heavy rains produced record discharges of water and suspended sedi ment by coastal drainages (K. Kroll, U. S. Geological Survey, personal communication). Since the present work was initiated in November 1968, little pre-flood informa tion had been collected. Clearly, the occurrence of the floods early in this research obviated any planned attempt to determine the "typical” suspended sediment budget with in Santa Barbara Channel. Consequently, the research ef fort was primarily devoted to study of the fate of the new material in the Channel. Indeed, the fortuitous 89 90 introduction of vast quantities of fine detritus greatly- facilitated the study of suspensate transport processes. However, the reader is cautioned that the data presented in this report (particularly during the early part of 1969) represent "atypical*1 conditions within the Channel. A detailed discussion of the flood magnitude is presented in a following section. At this point it is worthwhile to place the 1969 floods in perspective by briefly discussing the major sources of suspended matter and their "typical" contributions to the Channel. There are five possibly significant sources: rivers, wind, biologic, cliff erosion, and introduction by currents entering the area. Cliff Erosion Although much of the Channel coast is cliffed, the cliffs are generally fronted and protected by sand or gravel beaches and man-made seawalls. Furthermore, the work of Emery (I960) indicates that cliff erosion proceeds so slowly as to be a negligible source of detritus. Cliff erosion is probably a more significant source around the Channel Islands but, even here, relative to other sources it can be neglected. Wind Transport Babcock (1957) estimated the annual contribution of 91 q eolian detritus to the borderland to be about 1.5 mg/cm . This converts to an annual contribution of about 70 thousand metric tons of eolian detritus to the Channel. The fact that the bulk of this is contributed on the few days (perhaps 5 to 10/year) when strong Santana winds blow seaward indicates that the wind-borne sediment may have a marked effect on surface water transparencies and suspended sediment concentrations during such periods. This con clusion is demonstrated by data presented in a later section. Biologic Contribution The biologic contribution of suspended matter is made primarily by planktonic organisms (Emery, I960). In particular, the magnitude of this source can be approxi mated through an estimate of primary plant production. Oguri and Kantor (1971) investigated the rates of C14 fixation by surface water plankton during four surveys of the Channel in 1969-70. Using their data, a depth factor of four, a photosynthetic day of 10 hours, and a weight conversion factor of 2.6 (Emery, I960), the total annual g dry phytoplankton contribution is between 0.7 and 1 x 10 metric tons. Despite the great uncertainty of the factors entering this calculation and the chance that 1969 may not have been typical, this range agrees reasonably well with 92 estimates by Holmes (1957) and Emery (i960) of about 1 to 2 million metric tons. Stream Contribution Precipitation in southern California is highly variable from year to year and in any given year the bulk of the rainfall comes in Just a few days or weeks (Revelle and Shepard, 1939; Emery, I960; Gorsline, 1968). Con sequently, estimates of the mean annual stream contribu tions of sediment require statistical treatment of data collected over relatively long periods of time. Unfor tunately, such data are not available. Nevertheless, Emery (i960), Moore (1969)» and Rodolfo (1970) have attempted to estimate average annual river contributions from the southern California watershed. Emery approached the problem using rates of in organic sediment accumulation in the Borderland to arrive at a total stream-borne contribution of about 10 million metric tons/year. Moore (1969) used seismic reflection profiles to estimate an average annual river contribution of 7.4- million metric tons. This value is based on an assumed age of 1 million years at the base of "undeformed" Pleistocene and Holocene basin fill. There is, of course, considerable debate over the duration of the Pleistocene (Bandy and others, 1971) and, therefore, Moore's time estimate is open to question. 93 Rodolfo (1970) monitored suspended sediment con centrations near the mouths of the Los Angeles-San Gabriel- Santa Ana drainages over one rainy season. These data combined with water discharge data of the U. S. Geological Survey yielded a total watershed contribution of 7.7 million metric tons. Of this total, approximately 4.2 million metric tons is believed to be transported as bed load (Handin, 1951)* and 3.5 million metric tons as suspended sand, silt, clay and colloids. The value determined by Rodolfo, based on the most recent data, can be used to develop an estimate of sedi ment contributed by Santa Clara River. Rodolfo found that 717*000 tons of suspended matter was transported in the 194,185,000 m-^ of the Los Angeles-San Gabrlel-Santa Ana average annual runoff. Santa Clara River discharges an average of 1.61 x 10®m-Vyear. Assuming a similar suspend ed load, one arrives at a suspended sediment contribution of about 0.6 million tons/year by Santa Clara River. Handin (1951) placed the bed load transport of this river at 0.6 million tons, yielding a combined total of 1.2 million tons/year. This type of estimate by analogy to known drainage systems is uncertain. Large rivers with nearly equal discharges commonly transport far different suspended and traction loads. The great number of vari ables controlling runoff and sediment load in a drainage 94 system have, thus far, defied simplification (Meade, 1969). Current Transport into the Channel A surprisingly large amount of suspended sediment is introduced to the Channel by the currents entering the eastern and western passages. Figures 15-17 and 23 show that a turbid surface plume may round Point Conception and enter the Channel during most of the year. The transmis- someter data of November 1969 and February 1970 and October of 1970 indicate a large degree of variability in the magni tude of this inflow. However, if one assumes that the plume defined in February 1970 is typical of conditions during six months of the year (coinciding with the rainy season of November to April along the north Pacific coast), it is possible to obtain a crude estimate of the amount of particulate matter annually introduced to the Channel. In February the turbid plume was approximately 50 m thick, 20 km wide and carried an average of 0.5 mg/l of inorganic detritus. The assumption of a mean inflow of 10 cm/sec gives a water transport of about 1 x 10^ m V sec and a flux of 0.7 x 10^ tons of particles per year. This is about 50 percent of the mean annual contribution of Santa Clara River. Data to be presented later indicate that the strong current entering the Channel through the Anacapa-Oxnard 95 Passage Is always relatively clear and free of particles. These data suggest an average inorganic suspended load of about 0.1 mg/l. Nevertheless, if one assumes an average northwestward current of 20 cm/sec through a cross- section of 20 km by 100 m (2 x 10^m^), it may be calculated that approximately 4000 tons of material are carried into the Channel each day. This is nearly 1.5 x 10 tons/year. Mineralogic analyses of the <62p size fractions of Santa Barbara Basin sediments by Fleischer (1970) demon strate that the Santa Clara River is the principal source of inorganic detritus in the Channel. Thus, although the potential extra-Channel supply is large, only a subordinate fraction is retained. This conclusion is compatible with petrographic microscope grain size analyses of suspended matter carried in the Point Conception plume and the Anacapa Current. Two surface samples from each current yielded average inorganic particle sizes of &bout 8p for the former and less than 4ji for the latter current. For all practical purposes the contribution from the southeast can be neglected, whereas it is likely that deposition of detritus from the Point Conception plume becomes signifi cant during times of low runoff from local streams. This tentative conclusion is supported by the work of Fleischer (1970) and is discussed in detail in the following section. FLOOD SEDIMENT General Statement It would be of considerable interest to be able to establish a precise budget for the sediment involved in the 1969 floods in the Channel area. In particular, one would wish to know how much material entered the ocean and how, where, and in what volumes this material was sub sequently moved. Although the movement of sediment along the major stream drainages was well-monitored, the river mouth delta of the Santa Clara was precisely surveyed pre- and post-flood, and the author conducted an extensive off shore flood layer sampling program; a rigorous budget analysis is not justified. Problems which obviate an accurate flood sediment budget are: 1. Movement of 50 x 10^ tons of suspended matter by the Santa Clara River was measured at Sati- coy, California by the U. S. Geological Survey (Appendix B). Most of the river's discharge occurred on just two days with peak flows of 74,300 cfs and 92,300 cfs. The difficulty of retrieving integrated depth samples of rivers at flood stage means that under the best of 96 circumstances the suspended load estimates are only approximate. No estimate of bed load transport could be obtained. In addition, Saticoy is about 10 km from the mouth of the river. One must therefore make some perhaps questionable assumptions concerning sediment transport between Saticoy and the ocean. For example, as the river widens downstream and the gradient decreases, how much and what sizes of particles were deposited before reaching the sea? Casual observations near the coast sug gested that the river bed had aggraded after the floods. Furthermore, in February the river diverted its course near the mouth and flowed with destructive force through the Ventura Marine. Charles Holt (personal communication) stated that portions of the marina had collected a layer of silt and sand over 3 m in thickness, sufficient to bury some cabin cruisers. On the other hand, a considerable amount of wash load may have been added during peak flow as the river traversed the agricultural lowlands down stream of Saticoy. In this regard, the work of Meade (1969) demonstrated the difficulty of estimating stream loads in areas which are 98 strongly effected by the activities of man. 2. Since the Channel is not a closed system, it is not valid to attempt to establish the initial river contributions from offshore flood layer sampling. While these limitations restrict budget analysis, it seems likely that the actual Santa Clara River suspended load was somewhat greater than that measured at Saticoy. In addition, it will be shown that it is reasonable to assume that a negligible amount of detritus reached the Ventura Shelf from sources outside the Channel. If this premise can be satisfactorily established, it should be valid to relate temporal and spatial modification of the offshore flood layer to energy conditions and current pat terns within the Channel. This treatment is permitted by the fact that after April 1969, essentially no significant additions of stream-borne detritus were made by coastal drainages until the onset of the 1970 rainy season. Flood Sediment Magnitude Sources of flood detritus which must be considered of possible significance over the entire Channel are the following: the Santa Clara and Ventura Rivers, the Northern Channel Islands, the intermittent streams drain ing the south slope of the Santa Ynez Mountains, and river systems terminating along the coast to the north of Point 99 Conception. Rivers south of the Channel are discounted as important sources because they are either relatively small or too distant. The first major drainage system to the south, the Los Angeles River, is more than 110 km from Ventura. Santa Clara River Hourly information on water discharge and suspended load, gathered by the Water Resources Division of the U. S. Geological Survey, shows that this river transported ap- proximately 50 x 10 tons of material past Saticoy. Dis charge peaked at 92,500 cfs with a mean daily suspended load of 22 x 10^ metric tons (February 25). More than 70 percent of the total flood discharge occurred on two days, January 25 and February 25 of 1969. Ventura River The uncontrolled drainage area of this system is approximately one-eighth the area of Santa Clara River. Although the U. S. Geological Survey gauging station on this river was destroyed, discharge was estimated and suspended sediment samples were recovered near the river mouth on 22 days during the one month flood period. These data indicate a suspended sediment contribution of about 6.5 x 10 tons by Ventura River. It is noteworthy that a similar figure is obtained based solely on direct compari son to the drainage area and well-established suspended 100 load of Santa Clara River. Santa Ynez River and northern drainage systems Since both littoral and offshore currents move southward along the Pacific coast, it was felt that detri tus introduced north of Point Conception might influence sedimentation in the Channel. The common plume of particulate matter rounding the point has been discussed in a previous section (see p. 57). Unfortunately, esti mates of the discharge of suspended material by Santa Ynez River (Pig. 2) must be based entirely on a drainage area comparison to the monitored streams because this river is not gauged and was not adequately sampled. Using an un- p controlled area of 1000 km , it is calculated that this river contributed between 10 x 10^ and 20 x 10^ tons of suspended matter. Thirty km to the north of Santa Ynez River is the next large river, the Santa Maria. This stream was gauged and sampled during the floods; the re cords show that approximately 6 million tons of suspended matter was transported to the sea by this river. This load is relatively small compared to the Santa Maria drain age area and no doubt reflects the lower elevations and decline in storm intensity to the north. Northern Channel Islands San Miguel and Anacapa Islands are considered too small to be significant sources of suspended matter. 101 Furthermore, circulation patterns around San Miguel and Santa Rosa Islands indicate that the little sediment contributed by these land areas will be swept to the south. The area of Santa Cruz Island suggests that it may have supplied as much as 4 to 6 million tons of suspended detritus during the floods. However, aerial photographs during the floods (February) showed only small plumes of turbid water at the mouths of the islands intermittent streams and measurable flood sediment layers were found on the insular shelf only within well-protected coves. South slope of the Santa Ynez Mountains Although the south slope of this range has an area of about 500 km2, the steep topography, poor soil develop ment and lack of integrated drainage systems probably limited suspended load discharge to less than 7 x 10^ tons. Data to be discussed indicates that a flood sediment layer of about 1 cm was deposited on the shelf between Santa Barbara and Point Conception immediately following the floods (see p.107). If this layer was supplied exclusively by the Santa Ynez Mountains (an unreasonable assumption), it would indicate a total contribution of about 8-10 million tons. This is considered the maximum possible from this watershed. In summary, the total suspended sediment carried to the coast of Santa Barbara Channel during the 19^9 floods was approximately 65 to 75 million tons. This assumes 102 that the suspended load measured for the Santa Clara River at Saticoy was low by 5 x 10^ tons and that all of this material reached the ocean. The foregoing discussion of this estimate should alert the reader to the possible error. The total stream-borne suspended sediment poten tially available for deposition in the Channel was ap proximately 85 million tons. This is in the order of about 50 times the amount of fluvial detritus supplied during a "typical" year. Flood Sediment Texture The texture of suspended river detritus and material deposited on the Ventura Shelf was determined by the U. S. Geological Survey and R. L. Kolpack (Table II). The dif ficulty of obtaining representative samples of flooding rivers produces a large degree of variation in the textural data. Loss of the coarse particles concentrated near the river bed constitutes the principal source of error. Ow ing to the large data variation and known sample bias, we only can estimate the percentages of sand, silt and clay carried in suspension during peak flow. Using data from 10 samples recovered from Santa Clara and Ventura Rivers at flow rates of more than 10,000 cfs, these ratios are 15-20 percent clay, 40-50 percent silt, and 30-40 percent sand. Combining these data with suspended load estimates, TABLE II FLOOD SEDIMENT DATA Suspended Load (Tons) Santa Clara 50 x 10^ t 10 x 10^ Ventura 6.0 x 10^ t 2 x 10^ Santa Ynez 10-20 x 106 ± 5 x 106 Smaller Streams 8-10 x 10^ i 2 x 10^ Shelf Sediment (May 1969) Station Color AHF 12820 Red AHF 12821 Red AHF 12829 Red Drainage Area (miles ) Texture 1011 15-20$ clay 40-50$ silt 30-35$ sand 131 Same 400 Same 200 Same Texture 37$ Clay 63$ Silt <1$ Sand 8$ Clay 45$ Silt 46$ Sand 10$ Clay 86$ Silt 4$ Sand H o one can calculate the approximate amounts of flood sedi ment in the >62p and <62^1 size fractions. Bearing in mind the uncertainty of the basic data, this calculation indi cates that between 35 and 45 million tons of <62jU particles were introduced by Santa Clara and Ventura Rivers. The remaining 12 to 22 million tons were in the >62jU fraction. The 62)x division represents a natural break in the settling characteristics of the particles (Krumbein and Pettijohn, 1939; Inman, 1949) with the finer fractions being transported largely as suspended load and the coarser detritus as bed load in the nearshore zone. As pointed out by many workers the platy habit of the bulk of silt and clay particles favors suspension and transport offshore. Sand and gravel should be confined to a narrow nearshore band in the zone of littoral drift. This as sumption is substantiated by the textural analyses of flood sediments deposited on the Ventura Shelf immediately after the floods (Table II). A sample 1.5 km off Pitas Point contained nearly 50 percent sand, whereas at a dis tance of 4 km, less than 2 percent sand was found (AHF 12820, 12821). Sediments 2 km off the coast midway between Pitas Point and Ventura contained about 1 percent sand. At a distance of 6 km southwest of Ventura, in an area of normally medium-grained sandy bottom sediments (Wimberley, 1964), only about 5 percent sand was present in contrast to nearly 80 percent silt (AHP 12829). 105 Thus It is concluded that particles larger than about 62jx were confined to a coastal strip extending at most 1 to 1.5 km from the beach. The more mobile fine fractions were free to move in the littoral drift zone or diffuse offshore into the area of shelf currents. Initial Deposition of Flood Material Initial deposition of flood detritus from the Santa Clara and Ventura Rivers occurred on the Ventura Shelf within 20 km of the coast (Fig. 25). Both rivers trans ported vast quantities of sand and coarser material to the coast. However, only the sediment load of Santa Clara River was sufficient to construct a significant sand delta. Aerial photographs and precise bathymetric survey data, both pre-flood and post-flood, were kindly released by Charles Holt of the U. S. Army Corps of Engineers. These show that the subaerial portion of the delta extended 0.7 km offshore whereas detectable submarine shoaling occurred to about 2 km from the river mouth. Using a density of 1.5 gm/cm^ for the newly deposited material, between 12 and 20 million tons of sediment was present in the delta during April 1969. Data with which to estimate the amount of sand moving downcoast In littoral drift are not avail able. As discussed in the section on Channel hydrography, average littoral drift rates along the Ventura coast are Figure 25 Flood layer thickness in Santa Barbara Channel determined by bottom samples re~ covered in March and April of 1969. 106 120* 30’ i2o*oo‘ F L O O D S E D I M E N T T H I C K N E S S M A R C H - A P R I L , 1 9 6 9 SCALE lOnouticol ml. 20 ( C M ) P - P R E S E N T S A N T A B A R B A R A V E N T U R A O X N A R D S* 00 S4" 00’ S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D A N A C A P A IS . . S A N T A R O S A IS L A N D 1 2 0 ' 0 0 ' O 108 approximately 20-30 cm/sec. In this respect this coastal segment should be considered high energy; a condition re flected by the observed rapid attrition of the Santa Clara delta. Aerial photos made in August 1969 show that the delta had been reduced to a river mouth bar. The sub merged portion of the deposit probably suffered somewhat less, but still appreciable, erosion and transport to the southeast. Distribution of flood sediment offshore and the textural analyses discussed in the previous section, show that the <62fx fractions were transported to the northwest and west forming a triangular deposit between Pitas Point and Ventura. Flood sediment 5 km off Pitas Point contained nearly 25 percent clay and more than 45 percent fine silt. This pattern of transport of the fine fractions of suspended material introduced by the major rivers is entirely compatible with the distribution of light at tenuating substances in December 1968 and January 1969 (Figs. 22 and 26). The identity of surface water and bottom deposit patterns demonstrates that surface and near-bottom shelf circulation patterns also are similar. ■ z Assuming an average bulk density of 1.4 gm/cm for the rapidly deposited flood sediments, then between 35 and 40 million tons of predominantly <62p detritus was on the Ventura Shelf in March and April of 1969 (Fig. 25). This estimate is based on a wet weight water content of 60 per- Figure 26 Distribution of light transmission values at the surface during January 21-23, 1969. T R A N S M IS S IO N / M E T E R J A N U A R Y , 1 9 6 9 SCALE >0 nautical mi. 0 M E T E R S 027 027 o48 >33 o34 o43 S A N T A B A R B A R A S T A T IO N LO C A TIO N o7 10 o21 Nn°2 o5 V . ' 014 X ■ __o3 ^ 0 2 T '' °1 V E N T U R A O X N A R D o75 o71 o70 «71 o78 A N A C A P A IS , S A N M IG U E L IS L A N D S A N T A C R U Z IS L A N D I S A N T A R O S A IS L A N D l E O ' J t f Ill cent, shown by Emery (i960) and Gorsline and others (1968) to be a typical water content of surficial borderland basin sediments. In addition, one must assume a uniform layer thickness increase to 0.7 m at a distance of 1.0 km from the Santa Clara and Ventura Rivers. Combining the offshore layer and delta volumes, a total Ventura Shelf flood layer of from 47 to 60 million metric tons existed. Since the water flowing to the north west through the Anacapa-Oxnard Passage is always rela tively clear, it is assumed that addition of fine sediment from southern sources was minor. Furthermore, the Santa Ynez and other Pacific coast drainages are too remote to have appreciably influenced early deposition in the eastern portions of the Channel. This leaves the input of the Santa Clara and Ventura Rivers and the south flank of the Santa Ynez Mountains as potential suppliers of the Shelf flood layer. If the total contribution from these sources was in the order of 67 x 10 tons, the shelf layer represents about 70 percent (minimum) or 93 percent (maxi mum) retention of the flood material. Even taking the lower figure as more nearly correct, it still indicates a high retention by the eastern Channel. High retention of the 1969 flood material is interpreted to be the result of two factors. First, the fine particles probably formed larger floccules upon enter ing the less agitated salt water (Whitehouse and others, 112 I960; Ippen, 1966). Secondly, circulation in the eastern Channel favors high retention of particles introduced be tween Santa Barbara and Oxnard. As shown earlier, long shore drift transports material toward Oxnard where it is, in large part, entrained and turned back into the Channel (Pig. 17). Aerial photographs taken during and im mediately following the floods showed that a large amount of suspended matter was moving to the southeast in a near shore zone, extending a few hundred meters from the beach. This observation is in agreement with the work of Man- heim and others (1970) which showed predominant transport of of suspended matter in the longshore drift zone along the eastern United States seaboard. At the time, the present author believed that the bulk of the river-borne flood material would be transported to the southeast and lost around Point Mugu or down Hueneme submarine canyon. However, current patterns and the change in coastline trend south of Point Mugu combine to prevent great sedi ment losses. Traces of fine silt and clay were first recorded at depths greater than 500 m in late March and April of 1969, implying a particle settling rate of 7 to 10 m/day. This is about 10 times the Stokes Law settling rate of the average particle (4pi) in the bottom sediments at these depths (Hulsemann and Emery, 1961). The increased settl ing rates can best be attributed to formation of silt-size 113 floccules. In this regard, it will be seen that the path followed by fine river-borne particles to the basin floor is particularly favorable to the formation of rapidly settling grain aggregates. Flood Layer Distribution: May-August I 9 S9 The initial flood layer may now be treated as a well-established mass of predominantly <62ju detritus which subsequently supplied particles to other parts of the Channel. This is permitted because no additions to the layer were made after April 1969. Changes in the magnitude and areal distribution of the shelf layer can be related directly to shelf processes. The pattern of red sediment deposition on the shelf in late summer (Fig. 27) is similar to the pattern of initial deposition with the important exception that a second lobe of material had developed to the south of the primary lobe. This second lobe must represent a true re distribution of detritus on the shelf. The following interpretation of this temporal change is offered: 1. A portion of the particles resuspended near the coast over the primary lobe were transported in a near-bottom turbid layer toward Oxnard. 2. South of Oxnard this coastwise counterflow was entrained and turned back along the shelf edge by northwestward current flow (Anacapa Current). Figure 27 Flood layer thickness in Santa Barbara Channel determined by bottom sampling in May and August of 1969. 114 120*30' F L O O D S E D I M E N T T H I C K N E S S M A Y - A U G U S T , 1 9 6 9 SCALE 10 nouticQl ml. 2 0 25 kilometers 34*30' ( C M ) 119* JO' P - P R E S E N T S A N T A B A R B A R A V E N T U R A O X N A R D 5* oo S A N M IG U E L IS L A N D S A N T A C R U Z IS L A N D A N A C A P A IS S A N T A R O S A IS L A N D 116 3. As the turbid water moved along the shelf edge, deposition of the secondary lobe occurred. Although there are indications of pattern changes over the northern portion of the shelf, sample coverage is not sufficient to permit detailed discussion. Appreciable, but not quantitatively measurable, amounts of oxidized detritus were present in the troughs north and south of Montalvo Ridge. Current action over this ridge is able to prevent deposition. Two gravity cores at depths of about 500 m southeast of Gaviota (Pig. 27) recovered red layers 1 cm thick. The location of this deposit to the west of the trough north of Montalvo Ridge suggests the path followed by particulate matter from shelf to basin. The mechanics of this transport will be discussed in a later section. Flood Layer Distribution: Pebruary-June 1970 One and one-half years after the floods, approxi mately 40 percent of the 1969 shelf layer had been trans ferred from the shelf (Pig. 28). The bulk of the material forming a measurable surface layer had been transported close to the edge of the shelf 20 km southeast of Ventura* to the troughs north and south of Montalvo Ridge, and into the deep basin. The north trough aligned beneath the pre dominant axial trend of the Anacapa Current, received and acted as the conduit for the major portion of the flood Figure 28 Flood layer thickness in Santa Barbara Channel determined by bottom sampling in February and June of 1970. 117 120*00' F L O O D S E D I M E N T T H I C K N E S S F E B R U A R Y - J U N E . 1 9 7 0 SCALE 10 n autical mi. ( C M ) 2 0 P - P R E S E N T S A N T A B A R B A R A A - A B S E N T V E N T U R A O X N A R D 34 ocr S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D A N A C A P A IS , S A N T A R O S A IS L A N D 0 0 119 detritus. The oblong lens of sediment 20 km west of Oxnard at depths of 50 to 150 m was situated beneath the north westward flowing current. Pre-flood shelf sediments in this area were sandy silts and silty sands with less than 5 percent clay (Wimberley, 1964). Flood particles either were moved directly to the middle and outer shelf and upper slope or followed the indirect path outlined by the turbidity pattern of February 1970 (Fig. 17). A triangular wedge of flood sediment with a maximum thickness of about 10 cm remained off Pitas Point 1| years after the floods. In fact, a slight addition to this deposit may have been made in the winter of 1969-70. This accumulation demonstrates the existence of a permanent cur rent convergence in this area. Deposition of fine particles confirms a significant loss of transport power as currents from the south converge with northern shelf water and turn westward. As mentioned above, approximately 40 percent or 16 million tons of fine detritus had been removed from the shelf in the one and one-half years following the 1969 floods. This is in the order of one million tons/month. Beam transmissometer data discussed in detail later (see p. 185) show that transport of this sediment occurred al most exclusively in a near-bottom "nepheloid" layer with an average thickness of 20 m. Assuming an average current 120 of 20 cm/sec moving off the shelf edge (about 40 km in length), It is calculated that the nephelold layer con tained about 2.5 grams/meter^. Of course, if one intro duces a faster current the suspended load is decreased. This estimate is only a crude approximation since it was found that with time the concentration of the near-bottom layer decreased in response to continuous source reduction. Furthermore, the concentration is no doubt sensitive, on a short-term basis, to variation in bottom surge owing to long period swell. It is conservatively estimated that between 40 and 45 x 10^ tons of fine-grained «62jx) red flood sediment was deposited in the Channel during the 1^ years following the floods. In February-June 1970 a 2 to 3 cm layer of silt and clay covered large portions of the basin below about 500 m. Best described as a "sponge-like" surface mat, the initially red-brown particles had changed to yellow and gray at the surface of the reducing basin deposits. The porous consistency of the layer indicated a high water content and is reminiscent of the texture assumed by extremely flocculated material. The total flood sediment tonnage within the Channel in 1970 does not include any correction for material mixed into older sediments by benthic organisms. Studies report ed by Griggs and others (1969) and Barnes (1970) show that almost complete bioturbation occurs to a depth of 5 to 7 cm 121 with possible mixing to 25 cm. Unquestionably this factor influenced flood layer measurements on the shelves and basin slopes but to an unknown ex tent. The surprisingly large amount of sediment within the Channel in 1970 is interpreted to be a resultant of two factors. First, the hydrography of the area, controlled to a great extent by the coastline orientation, creates a distinct low pressure lee in both the atmosphere and the surface waters. Cur rents entering the Channel from its opposite ends tend to funnel suspensate into the area and, to an important degree, block escape of locally introduced sediments. The Santa Barbara Channel, in addition to being an area of high plankton productivity and being near large sources of terrigenous detritus, is an excellent sediment trap. Secondly, fine particles transported southward around Point Conception probably account for some of the sedi ments recovered from the deep western parts of the basin. The mineralogy of the <62ji fraction of the basin deposits (considered in the following sections) argues strongly for dilution of a predominant Santa Clara River as semblage by one or more other sources. Flood Layer Distribution: July 1971 In July 1971, two and one-half years after the floods, a series of box cores were taken on the southern portion of Ventura Shelf and off Pitas Point in order to 122 Investigate possible changes in the major flood deposits defined in February-June 1970 (Figs. 28, 29). Although bioturbation had occurred, the oxidized flood material was still distinct and easily measurable. The lens of sedi ment previously deposited along the southern edge of the shelf had been markedly thinned presumably by scour and particle resuspension associated with the Anacapa Current. The thickest deposits were measured over the middle shelf at depths of 30 to 70 m along the southern side of the shelf depression trending to the west toward the deep basin. Furthermore, a 7 cm layer was found within 5 km of Pitas Point emphasizing the permanence of fine sediment accumulation off this promontory. Deposition of fine-grained detritus containing an abundance of sand-sized terrestrial plant fragments within the middle shelf depression demonstrates the important in fluence of apparently small changes in shelf morphology upon current energy. In sum, the distribution of sediment on Ventura Shelf is controlled by the interaction of topography and shelf water circulation. It is noteworthy that large changes in current strength can be produced by subtle changes in shelf morphology or circulation patterns. Therefore, the commonly expressed conclusion that sedi ments covering continental shelves are not in equilibrium with present conditions must be carefully documented with Figure 29 Flood layer thickness on Ventura Shelf in July 1971. Values are in centimeters and were obtained using a modified Reineck box core. 123 FLOOD SEDIMENT THICKNESS JULY , 1971 SANTA BARBARA DEPTH IN METERS 5 0 34 VENTURA • 5 •8 •0 34 detailed studies of the shelf current field. 125 Flood Layer and Subsurface Basin Sediments During the course of the flood layer sampling program, it became clear that the oxidized detritus was slowly and continuously collecting in the deep portions of the basin and that it was, in fact, changing color after deposition. The earliest recoveries of flood material below sill depth in the basin showed small blobs of red- brown clay and silt scattered about the surface of box cores. After one year (February 1970) a layer up to 2 cm in thickness had accumulated in the deeper parts of the Channel. The layer consisted of a "spongy" surface mat with high water content. Of extreme interest is the fact that the sediment had changed color to yellow at the sur face and gray below. This led the author to speculate that similar gray layers in piston cores collected by Hulsemann and Emery (1961) and Fleischer (1970) were in reality ancient flood layers. The subsurface gray "silt" </ layers were attributed to turbidity currents by Hulsemann and Emery (1961). While the flood layer study was in progress, Dr. Peter Fleischer was completing an investigation of the silt and clay mineralogy of continental borderland basin sediments. He kindly agreed to extend his study to in clude a detailed analysis of four of the 1969 flood layer 126 samples. He had previously analysed a 6.4 m long piston core from 620 m in the basin. The details of his analyti cal methods can be found in his dissertation (Fleischer, 1970). The piston core contained 34 distinct layers of gray silt and clay intercalated with green "homogeneous" mud and laminated green sediment (Fig. 30). Emery and tt Hulsemann (1962) determined that the laminated sediment represents seasonally-controlled deposition of biogenic- rich (diatoms) and biogenic-poor sediment layers. One couplet thus represents a year's accumulation and is a kind of varve. Further, they considered the homogeneous green mud to be laminated material disrupted and homogenized by occasional invasions of burrowing organisms from the basin slopes. Their conclusion that the gray layers are turbid- ites was based on indications of graded bedding and a numerical increase in gray layers toward the northern slope of the basin (presumably the only possible source area). Of the 34 gray layers in the 6 m core, 23 are less than 2 cm thick, 3 are from 2 to 10 cm thick and 4 are be tween 10 and 12 cm thick. Only the thickest layers show slight indications of normal grading. Analyses of 11 gray layer samples and 15 green sediment samples (both homo geneous and laminated) reveal the gray sediments to be finer-grained, better sorted, and contain only 25 percent as much carbonate (2.5 percent by weight). The smaller Figure 30 Lithology of piston core 11270 in Santa Barbara Basin (after Fleischer, 1970). 127 o e p t h , cm CORE LITHOLOGY 128 SANTA BARBARA BASIN 11270 Or— 100 200 900 400 soo 600 CATALINA BASIN 11343 SANTA CRUZ BASIN 11267 TANNER CONTINENTAL BASIN RISE 11340 11275 BMAWVVNmM > vwmm awmwyrita U M M M M M '.'SSA'r ( y - I S SAND MUO HOMOGENEOUS A « 7500 b.p B « 12,000 b.p. 1 ^ 3 r l LAMINATED MOTTLED fS^CLAY rG B l GRADED BEDDING MISSING 47 129 mean grain size and better sorting reflect a deficiency of particles larger than 20ji in the gray layers (Fleischer, 1970). The low carbonate value is similar to that of the shelf sediment off Santa Barbara (Emery, i960) and sug gests that the deficiency of larger particles is the re sult of a deficiency in calcareous biogenic debris. A proposed provenance and depositional history for the gray layers must explain their better sorting, low carbonate and organic matter contents, numerical increase toward the mainland coast, color, and near absence of coarse silt and complete absence of sand. It appeared clear from discharge records and from the temporal changes of the 1969 flood layer that the Santa Clara River was the predominant source of the flood material in the deeper portions of the basin. The mineralogic data of Tables III and IV confirm this con clusion. The mineral composition of Santa Clara River suspendeds (collected during peak flow of February 25 at the river mouth) and four samples of the red flood layer in the Channel are virtually identical. Fleischer deter mined that Santa Clara River is the only major source of low chlorite sediment in the southern California water- g shed. By adding the sediment of Ventura River (6.5 x 10 tons), one arrives at a total-sediment chlorite content of 2.5 percent; the percentage of chlorite in the 1969 flood layer. Inspection of the data for other minerals leaves TABLE III < 6 2 j j TOTAL MINERAL COMPOSITION (after Fleischer, 1970) RANK REL. SAMPLE KAOL. CHLOR. ILL. MONT. VERM. QTZ. PLAG. ORTH. AMPH. SCORE f h Flood Layer* 8.9 2.2 39.0 20.5 2.1 22.2 3.9 1.3 0.09 Gray Layers+ 11.2 2.3 33.5 22.6 1.9 22.0 4.5 1.5 0.0 Green Layers** 12.9 3.5 27.5 25.6 4.2 20.9 4.3 1.4 0.08 Santa Ynez River 16.1 3.9 34.6 15.8 8.3 14.7 4.2 1.7 0.7 13 2 Gaviota Creek 11.3 0.0 25.7 16.0 0.4 29.2 15.1 2.2 0.10 12 3 Ventura River 6.6 4.6 31.1 10.3 8.3 30.3 6.9 1.9 0.0 7 4 Santa Clara River 9.1 0.5 38.0 18.8 7.2 18.5 6.2 1.6 0.16 22 1 * » average of 4 samples + = average of 11 samples ** = average of 15 samples TABLE IV <2p MINERAL COMPOSITION (after Fleischer, 1970) Sample Kaolinite Chlorite Illite Mont. Verm. Flood Layer* 9.4 0.8 34.7 52.7 2.4 Gray Layers+ 10.2 1.6 37.6 47.5 3.1 Green Layers** 10.4 3.1 35.9 46.6 4.0 Santa Ynez River 14.2 3.1 52.1 24.1 6.5 Gaviota Creek 7.7 3.0 47.0 37.4 4.9 Ventura River 10.2 2.4 52.8 30.3 4.4 Santa Clara River 15.0 0.3 33.5 50.8 0.4 * = average of 4 samples + = average of 11 samples ** = average of 15 samples 131 132 no question that Santa Olara River was the predominant source of the deep basin flood layer. Comparison of flood, gray and green sediment mineralogies (Tables III, IV) indicates that both size fractions (<62ji and<2ju) for all three deposits are similar. Values for the gray layers are intermediate be tween the 1969 flood layer and the green layers for most minerals in both fractions. All three deposits show best agreement with the mineralogy of Santa Clara River (com pared with other Channel area sources). To make this more visible, Fleischer developed a ranking system to Indicate relative agreement. The nine mineral species in each type of basin deposit were compared to the assemblages of the four rivers (Santa Clara, Ventura, Gaviota, and Santa Ynez; see Fig. 2 for locations). Differences for each mineral were ranked by absolute value and the rankings summed for each river. For all three basin sediments the Santa Clara River shows the highest score and, thus, is the assemblage in best relative agreement with the basin material. The strong similarity between the flood layer mineralogy and the gray layer mineralogy, particularly the chlorite percentages, argues for similar provenance and depositional histories for the two sediments. Both indi cate a relatively rapid influx of large amounts of only slightly diluted Santa Clara River detritus. The well 133 documented slow but continuous transfer of 1969 flood material from the Ventura Shelf to the deep parts of .the basin, the slmlliarlty of flood layer thickness and gray layer mean thickness, and the observed color change of the flood sediment to yellow and finally gray demonstrate a flood-year origin for the subsurface gray layers. The increase of gray layers toward the mainland slope (Hulsemann and Emery, 1969) is a logical consequence of the path followed by the flood detritus in transport from the shelf through the trough to the north of Montalvo Ridge and into the deep basin; transport was primarily af fected by the Anacapa Current. The lack of sand in the gray layers is one of the strongest evidences against a turbidite origin (Fleischer, 1970). It clearly indicates the low energy mode of transport Involved in the flood layer and gray layer movement and deposition. Low carbonate and organic matter contents are commensurate with the relatively undiluted Santa Clara River source. The dilution of the primary Santa Clara River assemblage during non-flood years shows that current transport into the area (principally within the turbid plumes rounding Point Conception) is an important com ponent of the Channel suspensate system. However, it should be stressed that even during such periods the proximity of the local source (Santa Clara River) results in continued predominance of locally-derived sediments. 134 In this respect, the path followed by terrestrial particles from the river to the deep basin (as defined by the temporal changes in the flood layer) is an indirect route involving stages of deposition, resuspension, and transport before final accumulation in the basin or with in depressions in the shelf and slopes. Since resuspended particles will almost assuredly be in the form of multiple grain aggregates (Ippen, 1966), it follows that the material swept from the shelf will settle at a relatively rapid rate with the resultant being a significantly in creased retention within the Channel. DISTRIBUTION OF PARTICULATE MATTER General Statement Previous work on the distribution of suspended particles in the ocean has defined three fundamental and recurring patterns; 1. The surface distribution is controlled by- source input and advective and convective water motion. Although inorganic material comprises between one-third to more than two-thirds of the particulate matter in all parts of the ocean (Parsons, 1963), surface concentration vari ability is, in the open ocean, caused by varia tions in plankton production (Jerlov, 1953b). Hence, the barren surface waters of the Sargas so Sea are nearly devoid of particles, whereas the equatorial divergences contain abundant suspended particles. Approaching the continents, the surface dis tribution is increasingly effected by the magnitude of terrestrial sources and the more variable production of plankton (Jerlov, 1968; Pak, 1970; Manheim and others, 1970). 135 2. There exist important maxima in the vertical distribution of particles. Theoretical argu ments have been advanced to explain the maxima (Jerlov, 1959; Riley and others, 194-9; Moore, 1969). Later these will be discussed in de tail (see p. I85). 3. It has been known, but not fully appreciated, that particle concentrations commonly increase sharply near the sea floor. Furthermore, this increase is not restricted to shallow water but has been observed at abyssal plain depths in the Atlantic and Pacific Oceans (Jerlov, 1968; Ewing and Thorndike, 1965; Eittriem and others, 1969; Pak and others, 1970). In light of the above information, the present re search was organized to provide data on the surface and subsurface distributions of particles and their relation ship to water stratification and circulation patterns. In the following sections, these data will be discussed chronologically beginning with surface waters and con cluding with the near-bottom information. Surface Distributions; Preflood Preflood information on the patterns of surface turbidity over Ventura Shelf is available for December 1968 (Fig. 22) and from the southern California shelf 137 survey conducted In 1959-60 by the Allan Hancock Founda tion for the State of California (Allan Hancock Fnd., 1965). Unfortunately, particle concentrations were not directly determined in either survey but can be approxi mated from the transparency data. Mean secchi disc transparency patterns in 1959 show that the shelf water between Point Conception and Oxnard attains maximum clarity in late fall and early winter and is generally most turbid in the spring. In all seasons turbidity increases toward shore with the most pronounced increases occurring off Carpinterla and Ventura. Of significance is the transparency pattern recorded in October and November of 1959• The pattern depicts a sur face plume extending westward from the coast near Santa Clara River; essentially identical to the pattern ob served in December 1968. Furthermore, a nearshore band of turbid water approximately 5 km in width was present round ing Point Mugu, apparently moving southeast, and turning seaward at Point Dume in 1959- Although surface water temperatures are not shown in the Hancock report, it is probable that the turbid coastal water coincided with a zone of relatively cold water as shown in November and December of 1969 (Figs. 11 and 12). The density distribu tion resulting from the presence of a nearshore band of cool water with warmer water to seaward should result in a southward coastal countercurrent. The importance of this 138 conclusion is that southward flow over the inner Ventura Shelf probably prevailed during the record floods of 1969. Whereas the westward trending plume off Ventura demon strates entrainment of turbid coastal water and retention within the Channel, the coastal countercurrent offers an effective escape route for river-borne detritus. This pattern and the possible loss of material downcoast must be reconciled with the previously discussed flood layer data showing remarkably high retention on the Ventura Shelf. Suspended Matter: January-February 1969 During the survey of January 19-23, 1969, the in tense rainfall leading to the flood runoff of January 25 began. The rains coincided with the passage, in one week, of four weather fronts from the northwest. With each came high winds and the development of short, steep waves. Un fortunately, the near gale force winds and high seas limited data collection to a nearshore zone within the lee of the Santa Tnez Mountains (Appendix A). All stations along the mainland coast were occupied on January 22-23; the last of this series off the Santa Clara and Ventura Rivers. By the 23rd these rivers had contributed a combined total of about 6 million tons of suspended detritus, the bulk of this, approximately 5 million tons, occurring on the 21st. Figures 26 and 31 Figure 31 Distribution of light transmission and sus pended particulate matter at the surface during the survey of January 30 to Febru ary 1, 1969. 139 •U TRANSMISSION / METER PARTICULATE MATTER (mg/I) J A N . - F E B . 1 9 6 9 0 M E T E R S o — S T A T IO N L O C A TIO N S A N T A B A R B A R A 0 1 2 . 44 °29 1 . 6 o57 o64 as . V E N T U R A o6S 07 068 °*o66 0 7 gQQ o5 o65 0 6 O X N A R D o7 o7 35 844 0 8 oG8 o10 o63 o44 0 5 0 6 ’ 20 o70 o52 1. 2 S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D A N A C A P A IS . t S A N T A R O S A IS L A N O . 120*00* 0*1 show the surface distributions of light transmission and total particulate matter for January 22-23 and January 30 to February 1. In the 48 hours after the January 21 dis charge of 3 million tons, turbid water had extended at least 15 kms from the Ventura coast. Figure 26 reveals a surface plume of 10 percent transmission water extending due west from the flooding rivers. Although sample cover age is not complete, it can be estimated from the light transmission values (see Fig. 5) that the surface water to a depth of about 10 m over the shelf contained an average of 3 mg/l of suspended matter. In the subsurface shelf waters beam transmissometer profiles (Fig. 32) show that a near-bottom turbid layer approximately 10 m in thickness covered the shelf whereas intermediate shelf water was relatively clear. The near-bottom layer contained at most 5 times as much particulate matter as the surface plume. Assuming mean particle concentrations of 3 mg/l and 15 mg/l for the two shelf layers, it is calculated that no more than 150,000 tons of detritus was in suspension over the Ventura Shelf on January 23. Clearly, the bulk of the 6 million tons of river material either settled rapidly to bottom or moved to the southeast in a very narrow near shore zone that was not sampled. The latter explanation is definitely not consistent with the pattern and volume of flood material deposition on the shelf in March-April 1969 (Fig. 25). The sediment budget discussed in an earlier Figure 32 Vertical profiles of light transmission over the Ventura Shelf recorded on February 1, 1969. 142 DEPTH (m eters) % TRANSMISSION/METER % TRANSMISSION/METER 0 5 0 100 0 5 0 100 10 i i | i i i i 10 " ”i • • ■ _ t j i i i i 10 20 \ - 20 20 30 J 30 ‘.i. • ~ r 7 : 30 4 0 AHF 12654 4 0 ■“BOTTOM AHF 12655 ~ 4 0 5 0 - BOTTOM I I I I I I I I I 5 0 i i i i I i ..i i— i — 5 0 1 1 1 1 1 1 I I ! I I i I 10 AHF 126 5 8 _ 10 ^ ^ r Z : ' r ' AHF 12659 - 10 20 r ■ • 20 — Q X ^BOTTOM — 20 3 0 - BOTTOM i i i i i i i i . i 30 i i i i i i i i r 30 144 section (p.105) demonstrated that at most only 30 percent of the flood detritus could have escaped to the southeast. One must conclude that the overwhelming bulk of the flood sediment was moving through the nearshore zone to be rapidly deposited over the inner shelf. Suspended Matter: May 1969 The first complete coverage of the Channel was ob tained in May l-7» 1969 (Appendix A). Comparison of the distributions of surface water transparency, phytoplankton productivity values (Oguri and Kantor, 1971), particulate matter concentrations, and surface temperatures and salinities reveals the following relationships (Pigs. 33- 35): 1. The distribution of surface temperature and salinity demonstrates large-scale upwelling of nutrient-rich water in the southwestern sector of the Channel with a less extensive patch of upwelled water to the southeast of Santa Barbara. Vertical water transport between Point Conception and the Channel Islands is re quired to replace surface water driven south west by strong persistent northwest winds off Point Conception. It is likely that the smaller patches of upwelling along the coast from the Point to Santa Barbara are also the resultant Figure 33 Distribution of suspended particulate matter at the surface in May 1969. All samples were processed with 0.45p mean pore-size Millipore HA filters. 145 1 20’00' 1*. 00 ^ 0 ^ 0 ^ ^ * kilometers PARTICULATE MATTER (mg/l.) MAY, 1969 0 METERS S T A T IO N LO CA TIO N o'*___^1.0 — SCALE 0 5 IO n autical ml. 30’ 1 19*30' SANTA BARBARA V E N T U R A O X N A R D * 0 J Y‘ • o / - - A v * - • S A N T A C R U Z IS L A N D ' SAN MIGUEL ISLAND ANACAPA IS . SANTA ROSA ISLAND 120*10 _ J_ _ 1 2 0 * 0 0 ' 119*10' - P - 0\ Figure 34- Distribution of phytoplankton productivity values at the surface in May 1969. Values are based on the uptake of Cl4 (after Oguri and Kantor, 1971). 147 1 2 0 " o t f PHYTOPLANKTON PRODUCTIVITY mg C/hr/m3 S C A LE (OnautiCQl ml. MAY. 1969 0 METERS 14.51 *v,o20.47 S A N T A B A R B A R A 10.89 '38.82 11.69 >19.63 24.93 20 82.92 29.26 o2.41 39.7 . V E N T U R A 3.58 35.85 o 29.73, o5.61 O X N A R D ’9.62 39.82 o 27.78 16.71 29.37 24.53 39.95 3 * oaf S A N M IG U E L IS L A N D S A N T A C R U Z IS L A N D A N A C A P A IS . t S A N T A R O S A IS L A N D . 00 Figure 35 Distribution of ash residue and inorganic particle values at the surface in May 1969. Ash residues are reported as percentages of the total suspended particulate matter con centrations. 149 120*30' 120*00* ASH RESIDUE (% ) INORGANIC PARTICLES(mg/l) SCALE 10 nautical ml. MAY, 1969 0 METERS o60 0.8 SANTA BARBARA «70 0 . 4 o85 1 .8 « 7 6 1.2 o83 0 . 4 0 . 5 13 o33 V E N T U R A o37 03 o67 0.5 o19 0. 1 o67 02 O X N A R D , 6 7 OS , 93 0.3 , 68 0.4 ,90 03 , 69 0.7 °64 0.4 o 6 7 0 .1 q 9 5 0 . 3 ,75/0.5 s « * 00' SAN MIGUEL ISLAND SANTA CRUZ ISLAND . ANACAPA IS. t . SANTA ROSA ISLAND V j l O 1 2 0 * 0 0 ' of seaward transport of surface water by- westerly winds. With the possible exception of the water over Ventura Shelf, there is a nearly perfect cor relation between phytoplankton productivity values and the transparency of the surface waters. Both parameters clearly reflect the two-current surface water circulation system in the Channel. Although plankton productivity values were high in the southwestern portion of the Channel and there occurred an obvious association be tween water fertility and transparency, this direct correlation is not reflected by in organic and organic particulate matter concen trations. Figure 35 shows a slight Increase in organic particle content (mg/l) associated with the fertile, upwelled water north of San Miguel Island; however, the observed concentration is not sufficient to explain the large transparency reduction. Similarly, the highest concentra tions of organic (combustible) particles were found in the central Channel and a generally poor correlation between this parameter and productivity values was observed in other parts of the area. It is concluded that, whereas a portion of the transparency decrease in the southwest sector can be attributed to the trans port of fine terrestrial detritus around Point Conception, approximately 10 to 20 percent of the transmission reduction must be a resultant of Increased concentrations of dissolved light absorbing substances. Jerlov (1953b) reported a common association of relatively high con centrations of dissolved “yellow" substances and highly productive surface waters in the equatorial Pacific. It follows that the excel lent correlation between surface water trans parency and productivity in May was, In part, caused by the distribution of dissolved organic materials. The surface accumulation of combust ible particles in the central portion of the Channel is compatible with transport of plank ton to a zone of convergence along the southern edge of the clear Anacapa Current. Relatively low concentrations of noncombustible detritus in the central area (Pig. 35) probably are due to hydrologic “shielding" from the turbid Ventura Shelf water by Anacapa Current. Transparency values and particle concentration data define a gradual particle increase across A the Ventura Shelf toward Pitas Point. Non- combustible material comprised approximately 75 to 80 percent of this turbid surface plume demonstrating that the particles were principal ly derived from previously-deposited flood sedi ment or directly from river discharge. The latter possibility can be ruled out since river runoff in the week prior to the May survey contributed only 450 metric tons of suspended detritus (U. S. Geological Survey, Appendix B). Transmissometer profiles over the shelf showed that the surface turbidity extended to a depth of about 10 m. Using 3 mg/l as an average particle content of the water, a total suspended load of approximately 15»000 tons can be cal culated. The majority of this material must have been supplied by flood detritus resuspend ed nearshore (probably within a few hundred meters of the shore), retained above the shallow thermocline, and diffused seaward. Particle concentrations at the seaward edge of this shelf plume were approximately 0.6 mg/l. Clear water sweeping to the northwest over the outer shelf entrained some of this turbid shelf water resulting in a particulate matter increase of about 0.3 mg/l and a light transmission de crease of 10 percent (Pigs. 15» 33). Surface water transparency values and particle concen trations in the Anacapa-Oxnard Passage show that northwestward flow blocks the southward escape of Ventura Shelf turbid water. Suspended Matter: July-August 1969 Surface water particulate matter data for the late summer months are characterized by relatively low concen trations in all parts of the Channel (Pigs. 36, 37). Con centrations range from 0.1 mg/l in the central portions of the area to 0.8 mg/l at a distance of 2-3 km from the mainland coast. Although the expected shoreward increase was observed, absolute concentrations, relative to May 1969* were lower by more than an order of magnitude over the inner Ventura Shelf. This decrease was caused by one or more of the following factors: 1. Wind speed and wave height data collected by the U. S. Army Corps of Engineers and summariz ed by Kolpack (1971) show a decrease in the magnitudes of both parameters during the months of July and August. Average wind speeds were among the lightest observed in 1969 and wave heights at the beaches were, on the average, only 0.4 m. The diminished wave energy no doubt resulted in reduced resuspension of near shore flood material. Figure 36 Distribution of suspended particulate matter at the surface in July 1969. Samples were processed with 0.45^ mean pore-size Millipore HA filters. 155 120* 30' 1 2 0 * 0 0 ’ PARTICULATE MATTER ( m g/i.) JULY, 1969 scale >0 nautical mi. 3 4 * 30’ 0 METERS 0.8. SANTA BARBARA •STATION LOCATIONS o 0 .5 o0.1 oO.S o0.3 o 0 .3 o 0 .4 o 0 .2 VENTURA o 0 .4 o 0 .5 Q2 o0.1 o 0.4 a 0.1 o0.1 o 0 .4 o G 3 OXNARD o0.1 o0.3 o 0 .5 o 0 .3 o0.3 o 0 .4 0 . 1 34* 00' SAN MIGUEL ISLAND SANTA CRUZ ISLAND oof ANACAPA IS. t SANTA ROSA ISLAND >20*00' Figure 37 Distribution of suspended particulate matter at the surface in August 1969. Samples were processed with 0.45p mean pore-size Millipore HA filters. 157 1 2 0 * 0 0 ’ 120* 30* PARTICULATE MATTER (mg/l) AUGUST, 1969 S C A LE 10 noulicol ml. METERS 2 0 STATION LOCATION SANTA BARBARA 0-5 0.3 0.2 0.5 0.7 VENTURA 0.5 0.4 0.3 % OXNARD 0.3 0.3 0.3 0.5 0.5 34* 00' SAN MIGUEL ISLAND SANTA CRUZ ISLAND ANACAPA IS SANTA ROSA ISLAND LA 00 2. Since there was no river supply of terrestrial detritus in May, it is probable that the quantity of fine sediment available for re suspension in the nearshore zone was signifi cantly smaller. 3. STD profiles in August (Kolpack, 1971) and the mainland shelf hydrographic survey conducted by the Allan Hancock Foundation (1965) show that the Ventura Shelf water mass attains its high est degree of vertical stability in the late summer. Near-bottom suspended sediment data, to be discussed in detail later, revealed particle concentrations in excess of 10 mg/l over the inner shelf off Pitas Point. Owing to the high vertical stability of the water, little if any of this detritus was stirred into the surface layers. Conversely, in May local upwelling along the mainland coast may have resulted in vertical diffusion of near bottom suspensate into the surface water. Ash residues of surface particulate matter in August range from greater than 80 percent off Pitas Point to less than 30 percent south of Gaviota (Fig. 38). Dis tribution of ash residue values and total particle con centrations closely reflect surface water circulation as defined by surface temperatures (Fig. 10). The narrow zone Figure 38 Distribution of ash residue values at the surface in August 1969. Values were ob tained by combustion at 450°c of particles separated with 0.45yu pore-size filters and are presented as percentages of the total particulate weight recovered. 160 120*30* 1 2 0 * 0 0 ’ F IL T E R A S H ( 5 0 0 ° C ) °/o IN T O T A L S U S P E N D E D M A T T E R A U G U S T , 1 9 6 9 s c a l e 10 nouiicoi mi. 20 25 kilomtfars 119*30' 0 M E T E R S S A N T A B A R B A R A o— STATION LO C ATIO N 70 7 0 . V E N T U R A 6 0 4 0 7 0 8 0 6 0 — . & O X N A R D 50 S A N M IG U E L IS L A N D S A N T A C R U Z IS L A N D A N A C A P A IS . t S A N T A R O S A IS L A N D Os 1 2 0 * 0 0 ' 162 of relatively high particle concentrations extending due west from Pitas Point (Pig. 37) marks the convergence of warm water along the northern Channel and cold California Current water entering the area from the southwest. Al though ash weights in the western end of this plume are low (high organic matter content), the productivity values of Oguri and Kantor (1970) are also quite low indicating that the majority of the suspensate here is organic detri tus swept into the convergence from the north and south. Multiplying the ash weight percentage by the total suspended load at each station in August yields the sur face distribution of the noncombustible fraction of the particulate matter (Pig. 39). Beyond the Ventura Shelf particle concentrations are exceptionally uniform at 0.1 to 0.3 mg/l. This range is taken as the normal inorganic suspended load transported into the Channel and the southern California Borderland in the surface layer of the California Current in late summer. The inorganic particle content of this current and the Anacapa Current appear to vary little with the seasons. Suspended Matter: November-December 1969 The transparency and suspended load data in November and December of 1969 reflect the fall and early winter intensification of the Anacapa Current (Pigs. 16, 40). Patterns of surface turbidity in both months are nearly Figure 39 Distribution of the "inorganic" (non- combustible) fraction of the total sus pended particulate matter at the surface in August 1969. 163 120*30* 120*00* INORGANIC SUSPENDED MATTER (mfl/l) AUGUST, 1969 SCALE 10 nautical ml. 20 25 kllomatan ,34* 30' 0 METERS STATION LOCATION S A N T A B A R B A R A .17 25 O o.7 0.1 25 o j . V E N T U R A 25 o . 1 .15 O X N A R D o . 3 ,25 ,25 ,25 26 25 3« o a r S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D A N A C A P A IS . , S A N T A R O S A IS L A N D w Figure 40 Distribution of total suspended particulate matter at the surface in December 1969. Samples were processed with 0.45^i pore-size Millipore HA filters. 165 120*30' 120*00' PARTICULATE MATTER ( mg/I) DECEMBER, 1969 SCALE 10 nautical mi. 2 0 .34*30' 0 METERS o — S T A T IO N LO C A T IO N o0.3 SANTA BARBARA ^°-6 0.2 0-2 °0.3 V E N T U R A 0.2 0.3 i O X N A R D » 0.1 0 . 1 0. 1 S A N M IO U E L IS L A N D S A N T A C R U Z IS L A N D A N A C A P A IS . S A N T A R O S A IS L A N D identical indicating the persistence and simplicity of the winter current regime. As in most other months the counterflow from the southeast contains little particulate matter and other light attenuating substances. During both surveys small turbid plumes were observed rounding Point Conception, off Santa Barbara Point, and extending westward from Ventura. The plumes off Point Conception and Santa Barbara probably represent turbid nearshore water driven to the south and east by westerly winds, whereas the surface plume off Ventura is interpreted as a resultant of shelf water entrainment by the Anacapa Cur rent. Since it is well established that the Davidson Cur rent flows to the north along the Pacific coast, the particulate matter in the Point Conception plume probably is derived from material transported southward in the littoral zone. As shown by the temperature distribution in August of 1969» southward water transport around Point Con ception is a permanent surface circulation feature. The amount of suspended matter in this current is a function of seasonal rainfall and river runoff along the northern and central California coast. Suspended Matter: February 1970 Station density was the highest of any of the Channel surveys in February 1970 (Appendix A). It is likely that fine current structure revealed by surface 168 temperature In February is present during other months but simply not resolved by the more widely spaced station grids. Although the larger number of stations defines many small eddies and current meanderings, the surface circulation is basically the same as that observed at other times in the Channel. Comparison of surface temperature pattern and the surface transparency (Figs. 13» 17) reveals a striking similarity in the distribution of these parameters. This remarkable association lends considerable support to the use of either of these water characteristics for surface current analyses. The total rainfall at Oxnard in January and Febru ary of 1970 was 16.25 cm; "normal'* for this station during these months. Assuming a negligible residual ef fect from the 1969 floods, it is of some interest to determine the pattern of transport of river-borne material under more typical conditions. Although seaward deflec tions of transparency isopleths occurred off Gaviota, and off Oxnard, high turbidity water is principally confined to a coastal zone approximately 5 kms in width. Surface water temperature distributions during fall and winter months indicate a downcoast (southward) drift of inner shelf water (see section on shelf currents). Particulate detritus introduced by local streams is, therefore, transported south toward Oxnard. Figure 17 169 demonstrates that as this coastal current reaches the Anacapa-Oxnard Passage it is entrained by the relatively swift California Countercurrent. The relatively high velocity of the northwestward current is suggested by the narrowness of the entrained turbid plume between the pas sage and Montalvo Ridge. As this current reaches the longitude of Santa Barbara, it begins to lose velocity and spread laterally. It is noteworthy that the plume shows little evidence of current direction changes which could be related to tides. Light transmission patterns at the surface, 50, and 90 m combined with surface temperature Information demon strate that the turbid plumes off Gaviota and south of Point Conception are a resultant of wind-driven surface currents. The transparency data show that the plumes ex tend only to about 50 m. At 90 m off Gaviota there is a shoreward deflection of clear water indicating subsurface flow toward Gaviota to replace surface water blown sea ward. Upwelling south of Gaviota is confirmed by a 0.4°C temperature decrease at the surface. Similarly, the turbid plume rounding Point Conception extends only to about 50 m and is associated with cold surface water driven into the Channel by the persistent northwest winds off this promon tory. Surface transparency and suspended load information for May, August, November, and December of 1969 and Febru ary 1970 suggest that the lateral extent of this cold water 170 current is controlled by seasonal variation in wind velocity off Point Conception; that is, relatively well developed in the spring and summer and poorly developed in the fall and early winter. On the other hand, the particulate matter content of the plume is a function of precipitation along the California coast and the competence of downcoast nearshore currents. Combining these factors, one may conclude that conditions are most favorable for introduction of suspended matter to the Channel in the late winter and spring (from February through May). The cold surface water north of the Channel Is lands had an average light transmission of 85 percent/m indicating a suspended sediment concentration of from 0.1 to 0.3 mg/l. Although suspended sediment concentrations were abnormally high in the early months of 1969» parti cle concentrations in July, August, November and December of 1969 and February 1970 in the two principal currents entering the Channel did not vary significantly. In other words, it may be tentatively concluded that the "offshore” California Current water (seaward of the turbid coastal water sweeping around Point Conception) and the California Countercurrent transport approximately 0.2 mg/l of parti cles at the surface throughout the year. Light trans mission profiles in November 1969 and February 1970 sug gest that this average surface value also is representa tive of suspended matter concentrations to the depth of I 171 the first sharp temperature decrease (in most instances this is the seasonal thermocline). Below this layer, particle concentrations decrease to approximately 0.1 mg/l. Suspended Matter: October 1970 Distribution of suspended matter in the surface waters of the Channel in October 1970 is of considerable interest because for two days prior to this survey (October 27- October 29) a strong Santana wind condition prevailed. U. S. Weather Bureau stations at 600 m on South Mountain (16 km east of Ventura) and 1000 m on Laguna Peak (at the west end of the Santa Monica Mountains) recorded winds from the north and northeast at a mean velocity of 60 kph gusting to more than 80 kph. Such off shore winds generally diminish rapidly seaward. However, on the 28th of October the winds measured at Santa Cruz Island were still averaging 32 kph. The strong Santana condition lasted about 2 days, diminishing rapidly on October 29. Surface temperature and light transmission data show that the strong winds produced a complicated system of small eddies in the eastern Channel and a general sur face water transparency decrease of about 20 percent throughout the area (Pigs. 41, 42 and 441. Temperature profiles over the Ventura Shelf reveal a wind-mixed layer extending to a maximum depth of 10 m; the wind transport Figure 41 Distribution of light transmission at the surface in October 1970 following a two-day Santana dust storm. 172 120* 50* I20-001 TRANSMISSION / METER OCTOBER. 1970 SCALE 1 0 n a u tic a l m i. O METERS o55 S A N T A B A R B A R A »47 39 STATION LOCATION 50 52 o44 52 58 76 o43 o57 V E N T U R A 70 o41 68 .62 .60 .40 .48 43 .72 .4 7 .7 0 .47 °45 •78 O X N A R D .46 .43 56 55 42 •55 ,27 65 S A N M IG U E L IS L A N D S A N T A C R U Z IS L A N D A N A C A P A IS . t S A N T A R O S A IS L A N D 120*00' Figure 42 Distribution of surface water temperatures in October 1970. The relatively cold water between Ventura and Santa Oruz Island is probably the result of local upwelling caused by strong land breezes. The small range of temperature throughout the area is compatible with the fall predominance of the Anacapa Current. 174 S U R F A C E T E M P E R A T U R E < * C ) ; • , O C T O B E R , 1 9 7 0 ,34® 30' o — STATION LOCATION SCALE 34® 30’ 2 0 SANTA BARBARA 1 5 . 0 VENTURA ■ 1 4 .5 ’ OXNARD 1 4 . 5 34 00 34* 00' SANTA CRUZ ISLAND SAN MIGUEL ISLAND ANACAPA IS, l SANTA ROSA ISLAND 175 Figure 43 Depth to the 12°0 isothermal surface in October 1970. 176 120*30' 120*00' DEPTH TO 1 2 *C ISOTHERM (meters) OCTOBER, 1970 SCALE ■ 0 nautieol 2 0 34*30' -S T A T IO N L O C A TIO N S A N T A B A R B A R A 35 25 40 o S _ - . V E N T U R A 45 SO O X N A R D 43 34 00 34* 00' S A N M IG U E L IS L A N D S A N T A C R U Z IS L A N D A N A C A P A IS . t S A N T A R O S A IS L A N D 1 20*00' Figure 44 Distribution of light transmission at 20 m in October 1970. The permanent counter clockwise eddy is well-defined in the western sector of the Channel, whereas the small, random eddies in the eastern sector probably are due to the strong Santana winds. 178 T R A N S M I S S IO N / M E T E R O C T O B E R . 1 9 7 0 2 0 M E T E R S SCALE o — S T A T IO N LO CA TIO N S A N T A B A R B A R A ©0 6 5 5 5 6 5 O X N A R D 4 0 6 0 ©o. 3 4 * o o ' 3 * O t f S A N T A C R U Z IS L A N D .. S A N M IC U E L IS L A N D A N A C A P A IS S A N T A R O S A IS L A N D 120*00* 180 of surface water probably only effected the upper 5 to 20 m of the water column. This conclusion is supported by the relative simplicity of the 12°C isothermal surface shown in Figure 43. Light transmission profiles demon strate that the 20 percent transparency reduction extended to a mean depth of 20 m throughout the Channel; this depth generally was the depth of an abrupt temperature decrease of from 1 to 2°C; the main seasonal thermocllne. Further more, the vertical profiles show that a strong particle maxima was formed at 10 to 20 m and that concentrations in this layer decreased seaward (Figs. 62-66). There is little doubt that the abnormal turbidity of the surface waters was the result of wind-blown detri tus. Microscopic analysis of the particles in five sur face samples from the central Channel revealed an abundance of quartz, feldspar, and mica with an average median diameter of 22^a. Since the October survey immediately followed the Santana condition, and it may be assumed that most of the eolian sediment had not yet settled through the seasonal thermocllne, an estimate of the amount of eolian detritus contributed to the Channel can be deter mined. Millipore filtration of 10 surface samples from a representative selection of stations yielded a mean parti cle concentration of 0.8 mg/l; approximately 0.5 mg/l above normal surface concentrations. Inspection of sur face transparency values indicates an average light trans 181 mission of 55 to 60 percent which corresponds to a parti cle content of 0.7 to 1.2 mg/l (Fig. 5). Thus, using an average concentration of 0.5 mg/l of eolian detritus in a surface layer 20 m thick, it is calculated that about 46,000 tons of wind-blown sediment settled into Channel waters during the two-day Santana storm. This estimate is based on firmer data than that used by Babcock (1957) and Emery (I960) and suggests that previous estimates were low by a factor of 2 or more (based on the assumption that Santana winds occur an average of 5 days/year). Vfeather Bureau statistics show that the 5 days1 estimate is predictable. Therefore, the data of October 1970 suggest that eolian contribution to the Channel may be as high as 100,000-120,000 tons/year. Although this is, on the average, only 10 percent of the annual stream contribution, during some dry years it may equal or exceed contributions from terrestrial runoff. An excellent example is provided by the 1968 discharge data for Santa Clara River collected by the U. S. Geological Survey (K. Kroll, personal communication). During water year 1968 Santa Clara River introduced Just 75*000 tons of suspended sediment. Other local drainage systems may have added another 25*000 tons for a total of about 100,000. Consequently, during a year or sequence of years of low river runoff the relatively coarse-grained eolian detritus may be detectable in the bottom sediments of Santa Barbara 182 Basin. It would be of some interest to attempt to isolate eolian particles in order to determine the quantity and texture of the material retained by the Channel. Summary of the Surface Distribution of Suspended Matter 1. Surface light transmission and particulate matter concentration distributions closely reflect the predominant two-current surface circulation system in Santa Barbara Channel. Relatively clear water carrying approximately 0.1 to 0.3 mg/l of particulate matter enters the area from Santa Monica Basin. As this flow sweeps to the northwest over Ventura Shelf nearshore suspended particles are entrained resulting in a 5 to 10 percent transparency reduction. A relatively turbid surface plume supplied with particles from the central California coast rounds Point Conception during most of the year and reaches its maximum extent and particle content in the spring. Seaward of this plume, the cold California Cur rent water has an average transparency and particle con tent that is essentially the same as that observed in the Anacapa Current. 2. Under non-flood conditions pronounced surface turbidity is largely confined to a near coast zone ap proximately 5 to 7 km wide. Over the inner Ventura Shelf stream-borne detritus introduced near Ventura moves to the 183 southeast within the littoral zone and within southward inner shelf currents. However, entrainment by Anacapa Current tfff Oxnard results in transport of most of this material bach into the Channel. Additionally, it is reasonable to assume that the southward inner shelf drift from Ventura to Oxnard is related to the entrainment occurring off Oxnard. 3. During flood conditions river discharge of turbid, fresh water is able to break through the littoral zone. Fine detritus transported seaward of the southward inner shelf current is carried to the northwest to be deposited beneath the shelf current convergence off Pitas Point. 4. Santana winds may contribute as much as 0.12 million metric tons of silt- and clay-sized material to Santa Barbara Channel each year. 5. Combustible suspended sediment comprises a highly variable fraction of the total load in both time and space. The highest concentrations (}80 percent) were measured in May in the nutrient-rich, upwelled water north of the western Channel Islands. Ash weight data for the surface waters in May and August of 1969 and February 1970 show a range of from 80 percent in upwelled waters during spring to less than 10 percent near the large coastal streams in February. As the distance from the coast in creases, variations in particle concentrations are : creasingly related to the production or presence of organic material. SUBSURFACE PARTICULATE MATTER DISTRIBUTION General Statement Analysis of the factors which combine to produce the subsurface distribution of particles is a complex problem involving the nature of the fluid and the fluid motion, the settling characteristics of the non conservative detritus, and the possibility that the suspended matter may control its own lateral transport (Jerlov, 1959; Moore, 1969). Jerlov (1959) discussed the formation of particle maxima in the ocean and points out that their presence requires that at least one of the following conditions be fulfilled: 1. Particle settling is retarded or stopped within the maximum and eddy diffusion increases below the maximum. The maximum is closely cor related with an increase in water column stability. 2. Lateral transport of fine detritus winnowed from topographic highs may produce particle maxima which may or may not be associated with water stratification. 3. Vertical variation in the supply and/or loss of 185 particles through biologic processes may produce particle maxima. For example, Riley and others (194-9) have shown, assuming a con stant settling rate and no vertical change in eddy diffusion, that a particle maximum should occur near the bottom of the euphotic zone simply in response to the vertical change in plankton production. Although the last mechanism is interesting in theory in practice it has been demonstrated that particle maxima in surface waters generally coincide with the shallow thermocllne and wave-mixed layer. This seasonal thermo- cline may or may not correspond to the bottom of the euphotic zone. Regarding the first two mechanisms, Jerlov (1959) shows, in the open ocean, that particle maxima commonly are found in the cores of water masses and that the rela tive abundance of particles at depth generally reflects particle abundance in the surface waters. In the vicinity of topographic highs, turbid maxima are sometimes observed which show no direct correlation to water masses and water stratification. It may be tentatively assumed that near the continents lateral transport of sediment from topo graphic highs will be of considerable importance. More than 350 vertical profiles of light trans mission and temperature were obtained during 1969, 1970 187 and 1971 In Santa Barbara Channel. In the sections to follow representative profiles from the central portion of the Channel, the insular ridge, and the mainland shelf are presented and interpreted with regard to sources of suspended particulate matter and the formation of turbid layers. This is followed by an integrated picture of the subsurface distribution of light attenuating substances provided by a series of Channel cross-sections. The im portance of the near-bottom zone warrants discussion in a separate section. However, it will be clear that the near-bottom turbid layers are closely related to turbid plumes at intermediate depths; separate discussion is merely an organizational convenience. Particle Maxima and Water Stratification Continuous vertical profiles of salinity and temperature as a function of depth in the Channel were ob tained using a Bissett-Berman STD (Model 9060) in May, August and December of 1969 and July 1971 (Kolpack, 1971). The salinity and temperature curves for all months are similar (Pig. 20). Salt content ranges from about 33.4 0/00 at the surface to 34-.4 0/00 in the nearly iBohaline basin waters. Salinity generally increases relatively slowly from the surface to 60 to 80 m where there occurs a more or less abrupt increase in gradient. The steeper gradient continues to a depth of approximately 240 m. 188 From 240 m to the deepest part of the Channel salinity in creases only 0.1 o/oo. Temperature curves reveal a relatively abrupt decrease from the wave-mixed surface water to a depth of about 50 m; below 50 m temperature continues to fall but at a considerably lower rate to approximately 200 m where the gradient again increases. The temperature gradient remains steep from 200 m to 460 m where it becomes marked ly gentler in the uniform waters below the sill depth (470 m). In detail, the temperature gradient consists of a large number of small, steep gradients separating nearly isothermal layers ranging in thickness from a few meters to more than 20 m. The origin of this "step-like" thermal microstructure has not been clearly established and is presently the subject of considerable research (Turner, 1967; Howe and Tait, 1970; Zenk, 1970). In any case, the presence of the temperature steps Is of great importance to the formation of particle maxima in the Channel. Figure 45 reproduces a representative selection of beam transmlssometer and temperature profiles from Santa Barbara Channel. In all the examples Illustrated and, in fact, in all profiles obtained during this research there is a striking association of turbidity maxima with temperature gradient changes. Although this strong positive correlation demonstrates the importance of re tarded particle settling within layers of relatively high Figure 45 Representative beam transmissometer and temperature profiles, Santa Barbara Channel, 1969-70. Note the good correlation between thermal gradients and particle maxima. How ever, the magnitude of the gradient increase is not directly related to the intensity of particle maxima. 189 P R O F I L E S O F L I G H T T R A N S M I S S I O N A N D T E M P E R A T U R E S A N T A B A R B A R A C H A N N E L 50 100 AHF 14793 40 100 50 AHF 14819 100- 12 20 AHF 13543 I II l I I 20 J___L t — i— r AHF 15862 J I L 10 14 100 100 50 AHF " 13583 30 100 50 AHF 13574 50 100 AHF 13565 50 20 vertical stability, it should not be assumed that sub surface maxima are the result of particle settling from surface waters. For example, whereas the shallow thermo- cline produces the highest degree of water column stab ility, it is not uncommon to find the most intense parti cle maxima below this thermocline and associated with a temperature step of only 0.1-0.2°C (Fig. 45). Further more, many examples of more or less abrupt temperature gradient increases which are not the loci of particle accumulations can be presented (Figs. 45, 51). These latter aspects of the subsurface particle distribution suggest that while retarded settling at thermal dis continuities is clearly important, of equal importance is lateral transport of detritus from topographic highs. Indeed, it will become evident that the particle distribu tion at a given locality within the Santa Barbara Channel depends upon both the structure of the water column and the recent history of the advectlve currents. Excellent instances of the Importance of current interaction with the bottom and the lateral spread of suspended matter are provided in Figures 46-48. Both examples deal with the clear countercurrent flowing northwest through the Anacapa- Oxnard Passage. Direct current measurements 6 m above the bottom over the outer Ventura Shelf record peak velocities in excess of 0.7 knots during flood tide. Light trans mission data demonstrate that such currents will erode Figure 46 Distribution of light transmission values in a vertical section in November 1969. Refer to Appendix A for station locations. For clarity, values below 60 percent in the bottom nepheloid layer over Ventura Shelf are not contoured. However, values im mediately above bottom are Indicated. 192 1 3 5 7 6 1 3 5 7 2 1 3 5 6 8 1 3 5 5 9 1 3 5 6 6 1 3 5 5 0 1 3 5 4 1 1 3 5 4 5 * — 1 I I 1 3 5 5 4 7 0 7 5 8 0 7 0 5 0 7 0 7 0 - - 7 5 - 7 0 . 60' 7 5 r-' P R O F I L E 6 • / . T R A N S M IS S IO N N O V E M B E R . 1 9 6 9 7 5 D E P T H IN M E T E R S 193 Figure 47 Distribution of light transmission values at 60 m in November 1969. The plume leaving Ventura Shelf is narrow as it passes to the north of Montalvo Ridge. This diagram il lustrates the primary path followed by fine grained suspended matter from the eastern shelf to the central basin. 194 120* 30* 120*00’ 31 00 • / • T R A N S M I S S I O N / M E T E R N O V E M B E R , 1 9 6 9 6 0 M E T E R S S T A T IO N LO CA TIO N SCALE 0 5 10 nautical ml. 54*30 119*30’ S A N T A B A R B A R A V E N T U R A • j . OXNARD S A N T A C R U Z IS L A N D ................... ANACAPA IS. S A N T A R O S A IS L A N D SAN bUdXlEU'-tSLA^D 120*30* _ J_ _ 120*00’ I - 119*30’ vO Figure 48 Distribution of light transmission values in a vertical section from the eastern end to the western sill of the Channel in July- 1971. The turbid, near-bottom tongue of water at stations 15872-15874 was associated with an abrupt temperature decrease with no salinity change. Anacapa Trough is located between stations 15873 and 15876. Refer to Appendix A for complete station locations. 196 Or 100- 200- 300- 4 0 0 - 5 0 0 - 15872 15867 15865 15859 15854 15850 15873 15874 15875 15876 15877 6 0 5 0 8 5 8 0 • ---------- 8 5 80 , 8 5 — 'e£z - 8 5 • 7 5 75 PROFILE 1 TRANSMISSION / METER 3 0 1 8 5 ■ 8 0 JU LY , 1971 8 5 DEPTH IN METERS 7 5 . 198 fine sediments from the shelf and eastern sill (Fig. 48). The resuspended particles are then transported with the geostrophic current to produce mid-water turbid maxima in the central portion of the Channel. The great predominance of horizontal diffusion over vertical water mixing is ap parent in Figures 46 and 47. Whereas the particle maxima at 60 m has spread from the shelf to cover an area of about 150 km2, the “core” of the plume is at essentially the same depth and material has diffused vertically less than 10 m. This agrees with recent experiments indicating that in most oceanic areas horizontal diffusion exceeds vertical dif fusion by a factor of from 102 to 10® (Bowden, 1962; Revelle and others, 1955)* Particle Distribution; Insular Ridge and Mainland Shelf Transmissometer profiles over the northern portion of the Channel Islands shelf in January, May, November of 1969 and February and October of 1970 reveal a simple and persistent distribution of suspended matter consisting of a surface maxima, clear water below the thermocline, and a variable but small increase near the bottom. The weakness of the near-bottom turbid layer even during the 1969 floods shows that the islands are a negligible source of fine detritus. This is compatible with the reports of Scholl (1959), Emery (i960), and Booth (1970) which reveal that 199 the shelf is thinly covered by predominantly sand and gravel with a generally high content of shell debris. The small amount of fine detritus washed from the islands is rapidly transported off the exposed, high-energy, narrow shelf. A representative selection of transparency records and cross-sections over the mainland shelf are reproduced in Figures 49-58. All profiles and cross-sections reveal the presence of a near-bottom turbid layer ranging in thickness from 5 to 20 m. Over the inner shelf at depths of about 15 m and less, the surface and near-bottom turbid layers appear to merge as long swell mixing, destroys vertical stratification and the water column becomes nearly homogenous (Figs. 53, 54). Surface wave action in the nearshore zone and to depths of approximately 15 m stirs fine material from the bottom and into the surface waters. However, unless this detritus is transported sea ward by surface currents, it apparently settles to the bottom rapidly, albeit in somewhat deeper water. Turbulence resulting from long swell and other shelf currents, while probably sufficient to maintain a near-bottom turbid layer over the middle and outer shelf, is not capable of homogenizing the water column at depths greater than 15 A stratification of the shelf water column appears which has two important effects. First, particulate matter settling from the surface or introduced Figure 49 Vertical profiles of light transmission and temperature in November 1969. AHF 13580, located at the eastern end of the Anacapa Trough, illustrates the relative clarity and uniformity of light transmission in the Anacapa Current before this water sweeps across the Ventura Shelf. AHF 13573 is located over the Ventura Shelf. Note the excel lent correlation between water structure (as defined by temperature) and the turbid maxima. The isothermal- turbid layers between 30 and 60 m probably were produced by current scour and near-bottom turbulence at shallower depths on the shelf. AHF 13548 is located over the main land shelf near Point Conception. The thick (10 m) iso thermal layer just above the bottom indicates significant levels of turbulence; however, the relative clarity of the near-bottom layer suggests that the generally coarse sediments covering this portion of the shelf yield little detritus to suspension. 200 D E P T H (meters) % TRANSMISSION / METER % TRANSMISSION/METER % TRANSMISSION / METER 100 100 AHF 13 573 NOV., 1969 ' AHF 13548 NOV., 1969 AHF 13580 NOV., 1969 T(°C)------1 150 ' B O T T O M TEMPERATURE (°C) 100 TEMPERATURE C C ) TEMPERATURE CO) Figure 50 Profiles of light transmission and tempera ture over the Ventura Shelf in February 1970. Note the association of particle maxima and thermal microstructure and the fact that the most pronounced transparency reductions are not present at the main thermocline. Refer to Appendix A for station locations. 202 % TRANSMISSION /METER % TRANSMISSION / METER % TRANSMISSION / METER 100 100 100 AHF 13923 FEB., 1970 AHF 1 3 9 2 4 FEB., 1970 AHF 13925 FEB., 1970 £ Q > Qj 6 T(°C) 50- 5 5 BOTTOM B O TTO M 1 0 20 30 10 20 30 30 20 TEMPERATURE ( °C) TEMPERATURE ( °C) TEMPERATURE ( ’C) 203 Figure 51 Profile of light transmission over the Ventura Shelf in February 1970. The pronounced bot tom nepheloid layer is closely associated with a rapid temperature decline and isothermal water layer. 204 205 % TRANSMISSION / METER £ Cb -*-o Cb £ & Q 100 0 AHF 13805 FEB., 1970 50 BOTTOM 1 0 30 20 TEMPERATURE ( °C) Figure 52 Profile of light transmission over the Ventura Shelf in October 1970. The absence of a well- defined isothermal bottom layer and the rela tively small transparency decrease near the bottom suggest that near-bottom turbulence and current scour were not significant at this station. 206 207 % TRANSMISSION/METER 0 50 100 20 AHF 14785 OCTOBER, 1970 T(°C) < / ) <b <b E 100 £ & Q 180 BOTTOM 1 5 10 5 TEMPERATURE ( °C) Figure 53 Distribution of light transmission values in a vertical meridional section across the Ventura Shelf in November 1969. Refer to Appendix A for profile location. 208 13586 13585 13582 13583 13584 13581 ■ y PROFILE 1 NOVEMBER, 1969 30 8 0 ° A 209 Figure 54- Distribution of light transmission values in a vertical meridional section across the central Ventura Shelf in November 1969. Refer to Appendix A for profile locations. 210 0 1 3 5 8 0 13579 13578 13577 13576 13575 5 0 PROFILE 2 NOVEMBER, 1969 DEPTH IN METERS 8 0 100 Figure 55 Distribution of light transmission values in a vertical meridional section from Goleta to Santa Cruz Island in November 1969. Refer to Appendix A for profile loca tions . 212 13561 13557 13558 13559 13560 13562 8 0 8 0 50 75 75 70 80 85 PROFILE 3 NOVEMBER, 1969 85 100 Figure 56 Distribution of light transmission in a vertical meridional section across the central Channel in November 1969. Refer to Appendix A for profile locations. 214 13552 13553 13551 13554 13555 0 13556 . 8 0 50 8 5 - l80 80 ‘ PROFILE 4 NOVEMBER,1969 DEPTH IN METERS \ -8 5 100 Figure 57 Distribution of light transmission in a vertical meridional section from Point Con ception to the insular ridge in November 1969. Refer to Appendix A for profile locations. 216 13540 13539 13538 13537 13536 Or 75 70 70 70 100 PROFILE 5 X NOVEMBER, 1969 % TRANSMISSION / METER DEPTH IN METERS I 217 Figure 58 Distribution of light transmission values in a vertical section from Ventura Shelf to south of Point Conception in February 1970. Refer to Appendix A for profile locations. 218 DEPTH, METERS 220 laterally is retarded within vertically stable layers to form turbid maxima. Furthermore, an upper limit is imposed on the near-bottom turbid layer. Figures 49-51 show that the transition from the bottom layer to the overlying clear water is commonly very sharp (occurring within 1 to 2 m) and coincides with an equally abrupt temperature in crease. In the absence of water stratification, near bottom turbulence should result in an exponential decrease of particles away from the sea floor (Sverdrup and others, 1942; Vanoni, 1946). Stratification imposes a "ceiling" on the turbulence; the abruptness of this ceiling is a function of the degree of water column stability (which is, of course, dependent on the vertical gradients of tempera ture and salinity). The transparency records reveal two significant as pects of the subsurface particle distributions over the middle and outer portions of the mainland shelf which are a direct result of the above factors. First, the near bottom turbulence produces a water layer which is both turbid and vertically isothermal. Since the production of an isothermal layer must involve vertical eddy diffusion, the temperature at the bottom of the layer will be slightly higher than that at the same level in deeper water. It follows that as this layer is transported across the shelf and moves into deeper water, relatively sharp and steep thermal gradients at both the upper and lower boundaries of the turbid plume should be present. This is exactly the situation illustrated in Figure 49. Moreover, it is common to find a Mstacking" of mid-water turbid layers over the outer portions of the shelf (Figs. 46, 58). The trans parency minima are associated with increases in the temperature gradient and are interpreted as the resultant of lateral transport of detritus from the near-bottom turbid layer generated over shoaler portions of the shelf. This interpretation is confirmed by the distribution of particles shown in the transmissometer crossr-sections of November 1969 and February 1970 (Figs. 46, 58). In re sponse to the bouyant force provided by the thermally- induced water viscosity Increase with depth and the trans port of the near-bottom turbid layer seaward, the turbid layer becomes detached from the sea floor at any slight increase in the slope of the shelf. That the material forming the subsurface, turbid, shelf layers Is primarily inorganic sediment of relatively fine texture is shown by the absence of downward spikes In the light transmission curves within these layers (denoting an absence of large organic detritus) and the high ash weight residues of the particulate matter sampled 1 m above the shelf surface (Figs. 77, 78). Central Channel Profiles and Channel Cross-sections 222 Continuous vertical profiles of light transmission and temperature in the deep, central portion of the Channel were obtained in October 1970 and July 1971. In addition, continuous profiles of salinity and temperature versus depth were recorded at each station in July using a Bissett- Berman Model 9060 STD. Representative examples of these data are reproduced in Figures 59-61. AHF 14815 and 14816 (Pig. 59) are located in the south-central Channel approximately 10 km north of the in sular shelf (Appendix A). AHP 14799 (Pig. 60) is more nearly in the center of the basin. The transparency curves at 14815 and 14816 are similar and define the presence of four significant turbid maxima; at 0-40 m, 50-110 m, 190-320 m, and from sill depth (480 m) to the bottom. The most pronounced transparency reductions occur near the surface and at the bottom; this is also the case on many light-scattering records taken over the continental slope and rise in the eastern North Atlantic (Eittreim and others, 1969). It is seen that all turbid maxima are cor related with more or less pronounced increases in the temperature gradient. For example, detailed inspection of AHP 14815 shows that below the abrupt thermocline at 30 m, the thermal gradients and associated water transparencies Figure 59 Profiles of light transmission in central Channel in October 1970. Appendix A for station locations. the south- Refer to 223 22** AHF 14816 AHF 14815 • / . TRANSMISSION 20 40 60 80 100 • X . TRANSMISSION 40 40 40 80 80 80 120 120 120 160 160 160 200 200 200 TCC)— TCC)- 240 240 240 C / > 280 280 280 320 320 320 360 360 400 400 400 440 440 440 SILL..PEPTH SILL DEPTH 480 480 480 520 520 520 560 560 BOTTOM 560 580 560 BOTTOM 5 10 15 TEMPERATURE CC) 20 20 5 10 15 TEMPERATURE CC) Figure 60 Profile of light transmission in the central Channel in October 1970. Refer to Appendix A for station location. 225 226 AHF 14799 % T/M 5 0 100 150 200 250 i- 350 40 0 4 50 500 550 10 15 2 0 Figure 61 Representative profiles of light transmis sion, temperature and salinity distributions in the central Channel in July 1971. Refer to Appendix A for station locations. The transparency trace is identified by numerous "spikes." Salinity curve is the unmarked continuous trace. The salinity scale is in divisions of 0.1 o/oo along the upper hori zontal axis. 227 228 9 Ajd£_15S52 ° /o T/M AHF 15848 °/o T/M >0 40 60 e ■4V 1 1 / AHF 15849 °lo T/M 34.4 34.I 34.I 50 50 100 100 150 150 200 200 T(°C)— t(°c; 250 H 250 300 350 350 400 400 450 20 500 550 20 20 °C 229 are as follows: 1. The average gradient from 40 to 120 m is 0.025° C/m, but the curve reveals three nearly iso thermal layers separated by relatively steep- gradient temperature "steps.” 2. Between 120 and 160 m the gradient decreases to a uniform 0.005° C/m. This gentle gradient is correlated to uniformly high transparency water. 3. The temperature gradient in the interval from 160 to 260 m gradually increases to an average value of 0.01° o/m. Light transmission de creases closely reflect the gradient changes within this layer. Note that attenuation shows a slight increase at 140 m corresponding to the slowly increasing thermal gradient, a more or less abrupt increase at about 200 m as the gradient continues to steepen, and finally a gradual decrease as the gradient becomes more gentle in the layer below. 4. Prom 260 to 460 m the average gradient of temperature is constant and relatively gentle at 0.004° C/m. Furthermore, the curve is com posed of a series of 5 or 6 layers ranging in thickness from 20 to more than 40 m within which the temperature change is very nearly zero. With the exception of a few minor reductions in transparency which appear to be associated with the small steps separating the nearly isothermal layers, light transmission gradually increases to greater than 90 percent at 440 m. 5. The sharp light transmission decrease of 8-10 percent at about 450 m (AHP 14815) clearly seems to be correlated to the equally sharp 0.2°0 temperature decrease at 460 m. The numerous "spikes" within this layer suggest retarded settling of relatively large, low density organic particles. The data of AHP 14816 sup port this conclusion. 6. At the sill depth of Santa Barbara Basin (480 m) there is a marked decrease in the temperature gradient corresponding to the upper boundary of the nearly isothermal (and iso- haline) basin water mass. Surprisingly, at 480 m light attenuation increases abruptly and continues to increase to the basin floor. AHP 14816 shows a similar gradual increasewhereas 14799 reveals a gradual Increase to 540 m fol lowed by a sharp attenuation jump of about 20 percent at the upper boundary of a 30 m thick turbid layer immediately above the basin floor. With the notable exception of the basin water, these data demonstrate a good correlation between water trans parency and stratification as defined by temperature gradient changes. The conclusion of Jerlov (1959) that the presence of a turbid maximum requires retarded particle settling and an increase in eddy diffusion below the maximum appears to be supported. The importance of verti cal variation in eddy diffusion receives especially strong support from the distribution of light attenuating sub stances revealed in AHP 14799 (Pig. 60). At this station the usual intense transparency reduction was observed above the most pronounced thermocline at about 25 m. It was shown in a preceding section (p. 171) that the bulk of the material in the wave-mixed surface layers In October was eolian detritus supplied by Santana winds. Whereas particle settling is retarded at the thermocline, there is no reason to believe that settling is any less retarded (by water viscosity changes) in the layers below. Nevertheless, the clearest water recorded at AHP 14799 is between 60 and 80 m near the base of the thermocline. This can only mean that eddy diffusion increases rapidly near the base of, and below, the thermocline. Similarly, the clear (>90 percent) water recorded on all profiles between 400 and 480 m also is nearly iso thermal. This association suggests vertical variation of eddy diffusion with relatively rapid diffusion within layers exhibiting gentle thermal gradients. The exceptional increase in attenuation within the 232 basin water merits special attention. The general as sociation of clear water and gentle thermal gradients at intermediate depths is reversed below sill depth. The possibility that the optical character of this water is due to factors other than an increase in particle content can be dismissed since water samples taken above and below sill depth in July 1971 revealed a nearly three-fold in crease in particulate matter (from>0.1 to <0.3 mg/l). Since the basin waters are essentially isothermal and iso- haline (see Pigs. 59» 61) there can be no retardation of particle settling owing to water viscosity increases. Therefore, the only fundamental difference between the basin and intermediate depth environments is that the water and particles within the basin are topographically trapped. It follows that as particles are continuously added, a reservoir of turbid water is formed. The particle content of this reservoir and the texture of the suspended matter depends on the nature of the detritus supplied and the magnitude of vertical turbulent motions to offset gravity settling. In order.to obtain an esti mate of the turbulent energy expended to maintain the basin turbidity, it is necessary to know the particle sizes and their in situ densities. Since the suspended matter is probably in the form of aggregates, special methods which were not available to the author are re quired. Visual examination of the particles sampled 1 m I 233 above the basin floor (with a polarizing microscope) showed that the bulk of the material is inorganic fine silt and clay. This agrees with ash weight data which show that combustible particles make up less than one-third of the total suspended matter in the basin nepheloid layer. Particle size distributions were determined for three samples obtained in February 1970 using a light microscope. All samples contained greater than 80 percent clay size detritus. Berger and Soutar (1968) report current velocities of up to 20 cm/sec in the deepest part of the basin. Thus, it may be presumed that the turbulent energy necessary to retard settling of this material is present. Twenty transmissometer profiles were obtained in the central Channel in July 1971* Three of these are re produced in Figure 61 along with subsurface temperature and salinity data. All profiles define a particle distribu tion similar to that recorded in October of the previous year. Hence, the observed pattern and its relationship to water structure as defined by conservative water pro perties can be considered to be typical of the central Channel. Changes in the vertical gradients of both salinity and temperature are associated with more or less pronounced changes in water transparency. However, the general ab sence of abrupt changes in the gradient of the halocllne results in predominant control of the distribution of 234 particle maxima by the thermal gradient (Pig. 61). Many of the STD profiles show a more or less abrupt change in the gradients of salinity and temperature at about 200 to 250 m. Comparison of these data with the T-S mixing diagrams for northern and southern water types pre sented by Emery (I960) indicates that the water below 200 m in July (and in most other months as shown by the STD re cords of Kolpack (1971)) was 100 percent "southern” water and that the gradient changes at this level denote the transition to mixed northern and southern waters above. The fact that this transition to pure southern water occurs at about 200-250 m in the Channel is interpreted to be the resultant of circulation constraints imposed by the eastern sill of Santa Barbara Basin. These data are com patible with the conclusion that the water below approxi mately 240 m is derived from the west, whereas shallower intermediate water may be derived from either end of the Channel. Below the sill depth of the basin July transmis someter profiles as represented by AHP 15859 show a com paratively thin but sharply defined basin nepheloid layer (Pig. 61). This distribution is similar to that observed at AHP 14799 in October 1970, but whereas the explanation for the thinness of the layer was not clear in the earlier data, it is evident in July that the thickness variation is directly related to thermal stratification of the basin 235 water column. The temperature curve at AHF 15859 demon strates the presence of two Isothermal layers below 500 m separated by a slight, but definite, gradient increase at 535 m. The basin nepheloid layer is associated with the deepest isothermal layer. STD and beam transmissometer profiles obtained in October 1970 and July 1971 revealed a similar water column structure which resulted in similar distributions of light attenuating substances in the central Channel. It was concluded that water stratification and particle distribu tions are strongly correlated whereas the bulk of the light scattering material probably was supplied ulti mately by lateral transport from topographic highs. This interpretation is supported by transparency cross-sections of the Channel (Figs. 48, 62-70). All light transmission decreases of more than 5 percent are produced by the spread of turbid water covering the shelf and basin slopes. Analyses of near-bottom particulate matter in February 1970 and August 1969 demonstrated that the detritus in the bottom nepheloid layer contained a maximum of about 20 percent combustible material. Thus, it may be assumed that the light transmission cross-sections provide a reasonably accurate picture of the subsurface distribution of inorganic particles. Granting this assumption, one can obtain an estimate of the subsurface particle concentra tions at all depths by referring to the calibration curves Figure 62 Distribution of light transmission values in a vertical meridional section from Pitas Point to the Channel Islands ridge in October 1970. Refer to Appendix A for pro file locations. 236 14773 14777 14776 14774 14775 6 0 40 50 -8 0 PROFILE 60 % TRANSMISSION/METER OCTOBER, 1970 100 DEPTH IN METERS 150 200 Figure 63 Distribution of light transmission values in a vertical meridional section in October 1970. The turbid maxima at 105 m was associated with an isothermal layer and abrupt temperature gradient increase. Transparency values below 60 percent in the bottom nepheloid layer over the shelf are not contoured; values just before bottom contact are noted. 238 14781 14780 14785 14787 0 20 80 80 100 PROFILE 2 45 85 TRANSMISSION / METER OCTOBER, 1970 200 DEPTH IN METERS io U3 VO Figure 64 Distribution of light transmission values in a vertical meridional section from Goleta to Santa Cruz Island in October 1970. Refer to Appendix A for profile locations. 240 13561 13557 13562 13558 13559 13560 8 0 8 0 8 5 -) 50 75 .-t" \ 75 70 80 85 Yr PROFILE 3 NOVEMBER. 1969 100 Figure 65 Distribution of light transmission in a vertical meridional section from Gaviota to the insular ridge in October 1970. Refer to Appendix A for profile locations. 242 14802 14803 14807 14804 1 4 8 1 5 75 6 0 70 70 65 75 9 0 ------ 80 100- * B5, 200 .- 9 0 300 400 P R O FILE 4 % T R A N S M IS S IO N / M ETER O CTOBER, 1970 500 to D E P T H IN M E T E R S Figure 66 Distribution of light transmission values in a vertical meridional section from Point Conception to the insular ridge in October 1970. The subsurface turbid plumes extend ing south from the mainland shelf are a typical feature of the suspensate distribution in this area. Note the high transparency of the waters immediately below the main thermo- cline and the general increase in suspended matter below 200 m. 244 14810 14811 14812 14814 14813 80 75 75 85 90 90 100- N. 90 200 PROFILE 5 ‘ /o TRANSMISSION 85 OCTOBER, 1970 85 300 80 DEPTH IN METERS no 40 0 Figure 67 Distribution of light transmission values in a vertical latitudinal section of the Channel from the Ventura Shelf to south of Point Con ception in October 1970. Refer to Appendix A for profile locations. In particular, note the tongues of turbid water entering the area from the west at depths of about 300 m and 380 m. 246 100 200 3 0 0 4 0 0 500 14813 14806 14804 14805 14799 14795 14790 14791 14783 14782 14781 25 65 85 85 9 0 — 9 0 8 5 P R O F I L E 6 Vo T R A N S M I S S I O N / M E T E R O C T O B E R . 1 9 7 0 --------8 5 • 8 5 8 5 D E P T H IN M E T E R S 8 0 8 5 9 0 7 0 85 Figure 68 Distribution of light transmission values in a vertical meridional section across the eastern end of Santa Barbara Basin in July- 1971. Refer to Appendix A for profile loca tions . 248 1 5 8 4 8 15 849 1 5 8 5 0 15851 -4 0 90 85 100 8 0 200 85 8 0 85 3 0 0 85 4 0 0 8 0 80 5 0 0 80 75 VO Figure 69 Distribution of light transmission values in a vertical meridional section across Santa Barbara Basin in July 1971. Refer to Appendix A for profile locations. 250 15861 15860 15859 15858 15857 ■20 50 -70 85 100 200 85 85 3 0 0 85 4 0 0 80 85 5 0 0 80 Figure 70 Distribution of light transmission values in a vertical meridional section across the western portion of the Santa Barbara Basin in July 1971. Refer to Appendix A for pro file locations. 252 1 5 8 6 6 1 5 8 6 3 1 5 8 6 5 15862 1 5 864 ■80 85 100 85 200 3 0 0 •80 4 0 0 80 5 0 0 75 254 presented earlier in this report (Pig. 5)* Since the transparency cross-sections are generally self-explanatory, they will not be discussed individually. However, the following aspects of the subsurface distribu tion of particles which bear on problems of water circula tion and the origin of lntermediate-depth and bottom nepheloid layers should be noted, namely: 1. The bulk of the water within the Channel has a transparency exceeding 85 percent and, thus, contains less than 0.2 mg/l of particulate matter. Particle maxima recorded on individual transmissometer profiles are closely cor related to changes in the vertical thermal gradient whereas the magnitudes of the trans parency reductions within the mid-water and bottom nepheloid layers increase toward the mainland and insular shelves, and thus demon strate that the turbid layers are locally generated. In particular, the cross-sections show that the most pronounced particle maxima occur over the Ventura Shelf and above the basin slopes adjoining this portion of the mainland shelf. This pattern is in agreement with the predominant control of basin sediment composi tion by material ultimately derived from Santa Clara River. An especially noteworthy exception to the above generalization is illustrated in cross- sections 5 and 6 (Pigs. 66, 67). The layers of <80 percent transmission water at 300 m and 380 m in section 6 were not obviously con nected to the mainland or island slopes. Therefore, it is concluded that particles with in these layers were not locally-derived but were being transported into the Channel within eastward flowing currents below about 250 m. Although eastward flow into the area is indi cated by the tongues of suspended matter, distribution of particles within the central Channel in October 1970 does not clearly define the advective currents. However, sections 1 and 2 recorded in July 1971 show that the turbid plume generated by vigorous westward flow with in the Anacapa trough (Pigs. 48, 68) does not continue directly west through the central Channel but turns to the north and flows along the mainland slope (Pigs. 68-70). If eastward subsurface flow into the Channel from the open Pacific is a typical feature of the intermediate depth circulation system, it follows that the subsurface advective circulation pattern is essentially the same as that observed at the 256 surface; a large cyclonic eddy. This conclu sion is of great importance to the retention of fine particles swept from the Ventura Shelf. It means that a considerable portion of the particles settling from the surface and intro duced by lateral transport from the bottom nepheloid layer will become involved in the cyclonic eddy. The resulting increase in resi dence time within the Channel is in agreement with and, in fact, is required to explain the high retention of 1969 flood detritus. Near Bottom Particulate Matter A decrease in light transmission occurs near the bottom in all parts of the Channel and the strongest reductions are over the mainland shelf and slope. The magnitude of the transparency decrease in 1969-70 is un doubtedly related to the tremendous influx of terrigenous debris early in 1969. Nevertheless, transmissometer pro files over the Ventura Shelf and within the Anacapa- Oxnard Passage in December 1968 reveal bottom nepheloid layers of varying attenuation. Therefore, increases in particle content near the bottom are typical and not dependent upon extraordinary sediment supply. Although an insufficient number of near bottom samples were obtained during and in the week following the 257 peak flood of January 25 to define the distribution of particles over the Ventura Shelf, critical samples were recovered five days after peak flow 2 km from the Santa Clara River and at the edge of the shelf. Two water samples 1 m above the bottom at a depth of 18 m off the river yielded an average of 53 mg/l of suspended silt and clay. Samples recovered along the southern edge of the shelf at approximately 50 m and 70 m contained 5 and 8 mg/l, respectively. These concentrations are in agreement with transmissometer data which show that transparency ap proached zero at the bottom near the shelf break (see Pig. 5). Whereas these few samples by no means adequately describe the particle concentrations over the shelf, it is striking that they contained an unexpectedly small amount of detritus. For example, if one assumes a concentration of 50 mg/l in a 10 m thick bottom nepheloid layer over the entire Ventura Shelf (800 km ), this layer would contain about 500,000 tons of suspended matter. This is less than 5 percent of the amount contributed by Santa Clara River alone prior to January 30 (Table II, Appendix B). The actual concentrations near the shelf edge demonstrate that even this small quantity is far too high. The "missing" 22 million metric tons of detritus must have been on the bottom or restricted to a narrow nearshore zone that was not sampled. Aerial photographs taken during the floods show that a considerable amount of fine material is, in fact, restricted to the littoral zone within a kilometer of the beach. However, the high retention of flood detritus on Ventura Shelf discussed in a previous section proves that this was a temporary situation and that the bulk of the river-borne sediment moved rapidly through the littoral zone. Therefore, the low concentrations of sus- pensate over the shelf immediately after the first period of flooding (January 25) strongly suggests that particles were rapidly settling near the river mouths. These data agree well with the pattern of flood sediment deposition determined in March and April of 1969. It follows that a balance was quickly reached between the influx of silt and clay, deposition, and transport or resuspension; the "balance*' was strongly tipped in favor of deposition of silt and finer detritus over normally sandy bottom sedi ments (Allan Hancock Foundation, 1965). The author has dwelled on the above relationships because it is critical to the following discussion of Moore's (1969) hypothesis of turbid layer transport. Subsequent to the floods particulate matter concen trations a meter above the bottom throughout the Channel were obtained in July, August, November and December of 1969 and February 1970. In addition, the transmissometer data of October 1970 give approximate concentrations for the bottom waters (Figs. 5» 71-76). Figure 71 Distribution of suspended particulate matter 1 m above the bottom in July 1969• Values were obtained by Millipore filtration of water samples recovered with a bottom- accuated 7-liter Van Dorn bottle. 259 liO'Stf IZO'Otf PARTICULATE MATTER (mg/l) ONE METER ABOVE BOTTOM SCALE JULY, 1969 SANTA BARBARA 2.6 o 0 . 7 o 1 .2 0O . 8 •STATION LOCATION 0.6 o 1 .4 o1.0 o 1 9 o10 . VENTURA o1.0 OXNARD o 4 . 3 o0.1 0.6 o0.2 o 4 .1 e0.6 0.5 e0.5 SANTA CRUZ ISLAND SAN MIOUEL ISLAND ANACAPA IS. SANTA ROSA ISLAND 260 Figure 72 Distribution of total suspended particulate matter 1 m above the bottom in August 1969. 261 120* 30' 120*00' 341 0 0 ' S U S P E N D E D S E D I M E N T (mg/l) O N E M E T E R A B O V E B O T T O M A U G U S T , 1 9 6 9 • - S T A T I O N L O C A T IO N SCALE 10 nautical mi. a 1 ^ ______ kilo m e te r* 3 4 *3 0 119*30 S A N T A B A R B A R A V E N TU R A O X N A R D S A N M iG U E L IS L A N D SANTA CRUZ ISLAND ANACAPA IS. S A N T A R O S A IS L A N D 120*30' K > O t N > Figure 73 Distribution of total suspended particulate matter 1 m above the bottom in November 1969. 263 PARTICULATE MATTER (mg/!) ONE METER ABOVE BOTTOM scale 2 ° NOVEMBER. 1969 S A N T A B A R B A R A •STA TIO N LOCATION 0O .4 0O .8 V E N T U R A o0.7 o3.7 o0.4 o0.9 2A O X N A R O S4* 00' S A N T A C R U Z IS L A N O S A N M IG U E L IS L A N O A N A C A P A IS . t S A N T A R O S A IS L A N D Figure 74- Distribution of total suspended particulate matter 1 m above the bottom in December 1969. 265 120* 3tf ' 120*00 PARTICULATE MATTER (m g/l) ONE METER ABOVE BOTTOM DECEMBER. 1969 54* SO’ STATIO N LOCATION S A N T A B A R B A R A 0.5 V E N T U R A . O X N A R D V M 0 0 S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D A N A C A P A IS . S A N T A R O S A IS L A N D 120*00* 266 Figure 75 Distribution of total suspended particulate matter 1 m above the bottom in February 1970. 267 PARTICULATE MATTER (mg/1) . FEBRUARY . 1970 V ONE METER ABOVE BOTTOM ^V34*30' ^ S J ' 3 * 3 0 ' SCALE >0 neutlcQl m l. 3 4 * 3 0 ' 2° STATIO N LOCATION S A N T A B A R B A R A 0.8 0.6 0.4 o > 0.2 0.6 V E N T U R A 0.2 0. 6- - 0 . 8 0 . 6 ’ ■^T\ v I I n ' O X N A R D ft. 6} 0.4 3 « * 00' s« o o r S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D A N A C A P A IS , S A N T A R O S A IS L A N O } I2 0 '0 0 Figure 76 Distribution of light transmission values at the bottom in Santa Barbara Channel in October 1970. Refer to Figure 5 for approxi mate values of suspended particle concentra tions . 269 1 2 0 * S 0 ‘ 120* 00* 3 4 O t f •/• TRANSMISSION/METER ONE METER ABOVE BOTTOM 34* 30' OCTOBER, 1970 30* O STATIO N L O C A T IO N SCALE 10 nouticoi ml. SANTA BARBARA \ VENTURA fl I OXNARD SANTA CRUZ ISLAND SAN MIGUEL ISLAND ANACAPA IS SANTA ROSA ISLAND 120*30* 1 2 0 * 0 0 ' II9*30: 270 271 All surveys show the highest concentrations over the Ventura Shelf and the lowest concentrations over the insular ridge, Montalvo Ridge, and within the hasin (Figs. 71-76). Concentrations typically ranged from lows of about 0.3 mg/l to highs approaching 30 mg/l over the inner shelf off Ventura. Following initial flood sediment deposition on the inner portion of the Ventura Shelf and cessation of addi tional river input in May, the concentrations and distri butional patterns of the bottom nepheloid layer over the shelf were a function of near-bottom turbulence, shelf current patterns, and the nature of the bottom material. In this regard, the distributions observed in July and August of 1969 and February 1970 indicate that the magni tude of near-bottom turbulence is inversely proportional to shelf depth. Such a relationship supports the conten tion that the energy to erode the bottom sediments was supplied by wave surge related to the shoreward passage of long period surface swell. Water particle velocities should begin to reach the velocities required to re suspend fine detritus (25-33 cm/sec) at depths of about 25 to 30 m. Once in suspension the distribution in August shows that the material over the inner shelf is dispersed seaward principally within the shelf current convergences off Pitas Point and to the west of Oxnard. In August, near bottom concentrations decreased from 10 mg/l over the 272 middle shelf to approximately 2 mg/l at the shelf break. This decline is unquestionably related to particle deposi tion over the middle shelf at depths exceeding 30 m as shown by the flood layer pattern in February-June 1970 (Fig. 28). However, in addition to losses due to vertical settling the concentration gradient must be further in creased through supply of detritus from the bottom nepheloid layer to form mid-water turbid layers. The abrupt decrease in particle concentrations coinciding with the edge of the Ventura Shelf is compatible with the de tachment of the bottom nepheloid layer from the sea floor at the shelf-slope juncture (Figs. 47, 58). Distribution of particles near the bottom in November and December of 1969 is noteworthy. Both surveys show that the highest concentrations are not over the inner shelf but rather are at depths of 30-50 m over the middle shelf. This pattern is not related to a major de cline in wave energies nearshore (Kolpack, 1971) but to the temporal decrease in the quantity of fine material available for resuspension. Thus, by late 1969 the most easily eroded fractions of the flood layer had been trans ported from the inner shelf to the middle shelf and beyond. The return to a pattern showing the highest concentrations near the major rivers in February 1970 is not in disagree ment with this conclusion. On the contrary, it reflects additional supply of terrestrial detritus during the 1970 273 winter rainy season. Precipitation records show that rainfall was “normal" for most stations in Ventura and Santa Barbara Counties during January and February of 1970; for example, Oxnard recorded a total precipitation of 16.2 cm, exactly normal for this station. To summarize, during flood conditions shelf trans port mechanisms are overwhelmed with the result that fine silt and clay particles are deposited rapidly nearshore. Nevertheless, wave surge at depths of less than about 30 m In concert with seaward transport within shelf convergences effects a relatively rapid transfer of fine detritus to the middle shelf and beyond. Indeed, it is reasonable to postulate that during normal periods of river discharge the bulk of the slowly-settling, fine particles are trans ported directly to depths exceeding 30 m. However, a notable exception to the above generali zation occurs off Pitas Point. Box cores recovered within 3 km of this promontory in June 1970 and July 1971 con tained homogeneous clay silt throughout the total length of the cores (30 cm). Thus, the deposition of from 8 to 10 cm of flood material in this area is not an abnormal or temporary occurrence. Whereas sand and gravel introduced by Santa Clara and Ventura Rivers settles in the littoral zone and is subsequently transported south, silt and finer fractions are, in large part, carried to the northwest along the nearshore edge of the Anacapa Current. Off Pitas 274 Point this current converges with southward shelf currents resulting in a triangular wedge of slack water and rapid deposition. It should be noted that the shelf sediment type off Pitas Point is incorrectly reported to be sand by the Hancock study (Allan Hancock Fnd., 1965). Particle concentrations 1 m above the mainland basin slopes ranged from 2-3 mg/l at the shelf break to 0.5 mg/l at the base of the slope. Values at the base of the insular slope were similar but nevdr exceeded 1.0 mg/l along the island ridge shelf break. Although a firm conclusion is not Justified by the number of samples ob tained, there was little variation in the above ranges through 1969 and 1970 suggesting that such concentrations are typical. Suspensate contents never exceeded 1.0 mg/l above the basin floor and the average was approximately 0.4 mg/l. Thus, a continuous decrease in material suspended near the bottom occurs from the shelf edge to the deepest parts of Santa Barbara Basin. This conclusion appears to be in compatible with beam transmission data recorded in October 1970 (Pig. 76); however, the discrepancy serves to illus trate the influence of decreasing particle size upon light attenuation. Thus, the slightly Increased attenuation ob served in the basin nepheloid layer relative to that at the base of the slopes is not caused by higher particle concentrations (in terms of mg/l) but, rather, reflects an 275 increase in light scattering by abundant clay-sized detritus. Combustible Particulate Matter Near the Bottom The distributions of non-combustible particulate matter suspended near the bottom in August 1969 and Febru ary 1970 are presented in Figures 77 and 78. With the ex ception of one value of 42 percent ash determined for a sample on the insular ridge in August, the content of non combustible particles in all samples exceeded 66 percent. Although analysis of the August samples is not complete, the available data suggest a significant decrease in the percentage of combustible particles in February 1970. This difference is compatible with the strongly seasonal produc tion of plankton in the surface waters of the Channel (Oguri and Kantor, 1971) and the laminae of organic-rich and organic-poor sediments in the basin (Hulsemann and Emery, 1961). Emery (i960) reported that the sediments of Santa Barbara Basin contain, on the average, 6 percent organic matter. Therefore, the low contents of organic matter suspended Just above the basin floor in February support a conclusion that the bottom nepheloid layer is not produced by resuspension of basin sediments but is supplied by particles settling from shoaler areas. Figure 77 Distribution of ash residue values (450°C) 1 m above the bottom, August 1969. 27 6 • / . F IL T E R A S H { 5 0 0 * C ) O N E M E T E R A B O V E B O T T O M A U G U S T . 1 9 6 9 SCALE 1 0 nouticol m l. S A N T A B A R B A R A o89 o79 o75 o90 o70 o80 o85 o88 O X N A R D o89 o92 «86 690 o67 685 76 c78 o90 *42 5 « * 00‘ S A N M IG U E L IS L A N O S A N T A C R U Z IS L A N O A N A C A P A IS l .. S A N T A R O S A IS L A N D . ! "0 «o* s o ' Figure 78 Distribution of ash residue values (450°C) 1 m above the bottom, February 1970. 278 F I L T E R A S H ( 6 0 0 * 0 O N E M E T E R A B O V E B O T T O M F E B R U A R Y , 1 9 7 0 SCALE 10 AQVtiCQl *fllL 20 PS hilom*t«r« S A N T A B A R B A R A o94 o99 o90 o94 ' «94 o99 o95 . VENTURA o89 «99 •90 o90 •89 O X N A R D o85 o99 e98 •97 o75 o93 S A N M IG U E L IS L A N O S A N T A C R U Z IS L A N O A N A C A P A IS . V S A N T A R O S A IS L A N O 120* id/ 120*00' Bottom Nepheloid Layer Thickness 280 Whereas the light attenuation values Immediately above the bottom are not directly related to depth in the Channels a graph of bottom nepheloid layer thickness versus depth reveals a fair correlation (Pig. 79); the nepheloid layer comprises about 10 to 20 percent of the total water column. This relationship cannot be a resultant of varia tion in particle supply, but is more reasonably attributed to the limiting influence which vertical stability exerts upon near-bottom turbulence. Values of vertical water column stability (Table V) show a gradual decline with depth in the Channel and, with this decline, there is a commensurate decrease in the energy required to vertically displace a given water parcel. Large deviations from the general trend of the curve (Pig. 79) are interpreted to indicate that the "balance" between transport, deposition and erosion has shifted. An excellent example of such an anomalously thick nepheloid layer was recorded in October 1970 at a depth of 400 m over the fan south of Point Conception (Appendix A; station AHP 14812 ). The distribution of light transparency values at the bottom in October (Pig. 76) shows that the anomalously thick turbid layer also was markedly less clear than surrounding near-bottom waters. The conclusion that erosion of surface fan sediments was occurring is Figure 79 Scatter diagram of bottom nepheloid layer thickness (BNL) versus depth in the Santa Barbara Channel. Data are from the October 1970 survey. The apparently anomalously thick layer (110 m) at a depth of 400 m was recorded over the Point Conception fan. 281 BNL THICKNESS (m ) 120 100 8 0 6 0 4 0 20 0 1 1 1 1 1 " ~ r 0 A V o — o o — o — o o — o o — o o o o o o o o -- o © -- o -O A O o oft ° o° 0 o o o o 1° 1 1 1 1 L 100 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 D EPTH ( m e t e r s ) 282 283 TABLE V WATER COLUMN STABILITY Depth (m) Vertical Stability* December 1969 July 1971 0 1294 1280 50 1160 614 100 472 200 150 528 154 200 354 134 250 158 84 300 98 120 350 76 148 400 96 138 450 26 80 500 10 44 550 # 10^ Sverdrup and others, 1942. I 284 supported by the subsurface distribution of temperature (Pig. 80). The southward slope of the 9° 0 isothermal surface over the fan shows relatively strong inflow of water is associated with the thick bottom nepheloid layer. The gentle southward slope of the 9° 0 surface in the eastern portion of the basin and within the Anacapa Trough in October indicates sluggish, probably meandering subsurface flow. This agrees with the southward movement of particle maxima within the trough and the presence of vigorous eastward currents south of Point Conception. On the other hand, the subsurface distribution of light at tenuating substances in July 1971 demonstrates relatively strong westward flow into the Channel through Anacapa Trough (Pig. 48). Thus, the inflow of subsurface water may alternate between the eastern and western passages; however, the duration and possible periodicity of such flow variations cannot be determined with the available data. In sum, the distribution of near-bottom suspended matter generally conforms to Channel bathymetry. Highest concentrations are present over the mainland shelf in creasing as one approaches Ventura. Conversely, the lowest concentrations are in the basin and over topographic highs swept free of fine particles by vigorous currents and located in areas removed from large sediment supply. The broad fan-shaped rise forming the slope south of Point Conception is an exception to this rule. On all surveys a Figure 80 Depth to the 9°C isotherm in Santa Barbara Channel in October 1970. Depths are shown in meters. 285 120*30’ 120*00' DEPTH TO 9°C ISOTHERM scale OCTOBER, 1970 10 nautical mi. 34* 30' 20 25 kilom eters O STATION LOCATION S A N T A B A R B A R A o 1 4 5 o 1 9 0 . V E N T U R A o 1 7 0 O X N A R D o 1 8 5 S A N M IG U E L IS L A N D S A N T A C R U Z IS L A N D A N A C A P A IS . l S A N T A R O S A IS L A N D 120“ 30' 1 20*00' 287 small Increase In particle concentrations was noted over the fan surface. The increase can be attributed to the southwest shift of currents in this area, the settling of material from surface and subsurface turbid layers round ing Point Conception, and the demonstrated, but probably infrequent, resuspension of detritus by vigorous eastward currents. The accumulation of a few millimeters of red flood material of fine texture shows that, on balance, there is a slow net deposition on the fan. Nevertheless, It Is clear that this rate of sedimentation would not be sufficient to build the fan above the rapidly-aggrading basin floor. Therefore5 the fan must be classified as a relict feature. Although speculative, it seems reasonable to presume that the transport of sediment around Point Arguello and Point Conception from the central California coast would be considerably greater during low sea level stands in the Pleistocene. It Is tentatively concluded that the fan was constructed, for the most part, during Pleistocene glacial stages. TURBID LAYER PLOW AND THE ORIGIN OP THE BOTTOM NEPHELOID LAYER General Statement The near bottom zone is of particular interest to sedimentologists. In all aqueous media it is within this boundary zone that the opposing forces of water motion and particle settling interact to determine the form and pro perties of sediment bodies. In this regard, the discovery and description of a "permanent1 ' bottom nepheloid layer ranging up to more than a kilometer in thickness along the continental margin of the North American Basin (Jerlov, 1953a,b; Eittreim and others, 1969) and a perhaps similar layer in the Pacific (Pak and others, 1970; Ewing and Con way, 1970) has given rise to a mild controversy. The un answered questions which fuel the controversy are the source of the particles and the mechanism which maintains the turbid layer. Three origins have been suggested for the particles: 1. Turbidity currents (Eittreim and others, 1969). 2. Continuous, low-density turbid layer flow down the continental slope (Ewing and Thorndike, 1965; Eittreim and others, 1969). 288 289 3. Resuspension of previously deposited sediments by benthic organisms or turbulent bottom cur rents (Derek Spencer, personal communication; Eittreim and others, 1969). At present, these suggested sources are purely speculative. Essentially no data are available with which to begin to make an evaluation. For example, Eittreim and others (1969) favor a turbidity current origin for the bottom nepheloid layer in the Atlantic. However, their conclusion seems to be little more than a guess since they present no data with which to eliminate the other possible sources. In order to attempt an evaluation of these various hypotheses, it was obvious that we needed a large amount of reliable data on particle concentrations in the bottom nepheloid layer. Furthermore, a test area in which one or more of the possible sources could be eliminated at the outset was required. It was with these considerations in mind that Santa Barbara Channel was selected for the present research. The advantages offered are as follows: 1. There are no large submarine canyons incising the basin slopes. Consequently, turbidity cur rents can be neglected. The absence of this transport mechanism in the Channel is confirmed by the properties of the basin sediments and the discovery that certain sediment layers which were previously thought to be turbidites are, 290 in fact, flood-year deposits. 2. There are no benthic macro-organisms below the basin sill owing to the reducing condition of the bottom sediments. Therefore, particle re- suspension over the basin floor by burrowing organisms can be eliminated. 3. Ventura Shelf sediments are the finest along the southern California nearshore shelf (Emery, I960) and it was expected that the highest con centrations of suspended matter would be present here to facilitate testing of the low-density flow hypothesis. Of course, the fortuitous timing of the record 1969 floods provided the best possible conditions; conditions which probably will not be duplicated for many years. Consequently, a concerted effort was devoted to sampling during 1969 the waters immediately above the bottom in all parts of the Channel. Turbid Layer Transport In a recent paper Moore (1969) concluded that in order to adequately explain the distribution of fine grained sediments within the enclosed basins of the Cali fornia Borderland, a transport mechanism involving gravity flow was required. A large portion of his paper was devoted to development of the hypothesis that fine 291 particles resuspended at shelf depths will form a near- bottom turbid layer which by virtue of its excess density will begin to flow downslope to ultimately deposit material in topographic depressions in the basins. This is es sentially a "low-density" turbidity current and is similar to a mechanism termed "auto-transport” proposed by Bagnold (1963). According to Bagnold, if a suspension of particles is maintained by upward directed turbulent water motion, the grains will impart an excess density to the fluid which will depend on the average particle density and concentra tion. Further, if a sloping interface between the turbid fluid and the overlying clear water is maintained, the turbid water will begin to flow downslope at a rate deter mined by the excess density and the slope. Although Bag nold does not consider the effect of vertical increases in water density in the sea, it is clear that to initiate downslope auto-transport in the ocean, the excess density of the suspension must exceed the vertical density gradient of the water. Therefore, the increase in water density with depth dictates the minimum particle concentration needed to maintain a flow between two vertically separated points. If this concentration is somehow reached, a flow should ensue provided the particles are kept in suspension by turbulent mixing. It is a simple matter to compute the density 292 excesses and corresponding suspended loads required to maintain such a flow in Santa Barbara Channel (Table VI). Included in Table VI are the theoretical velocities ob tainable by a given suspension on a 2° slope computed from the general equation for geostrophic flow: V = 4 P' ~ 1 -tan 0 f P, where p^ = density of nepheloid layer, p = density of clear water., f = Coriolis parameter, tan0 = slope of interface, and g = acceleration due to gravity. A number of interesting points emerge in this table: 1. The suspended load needed to drive a flow from the Ventura Shelf break (100 m) to the basin floor (600 m) is approximately 0.4 grams per liter; provided no settling or other dilution occurs. 2. As the water density gradient and vertical stability decrease to nearly zero below sill depth, the requisite particle concentration falls to 2-3 mg/l. Furthermore, this decrease is aided by the fact that the density change of water for a given temperature change decreases with decreasing temperature. As an example, 293 TABLE VI TURBID LAYER FLOW Required Depth Water Density# Density Excess* Velocity** 0 1.026566 1.0 g/1 285 cm/sec 50 1.027257 0.4 g/1 115 cm/sec 100 1.027376 0.3 g/1 85 cm/sec 150 1.027416 0.25 g/1 70 cm/sec 200 1.027480 0.2 g/1 55 cm/sec 250 1.027531 0.15 g/1 42 cm/sec 300 1.027559 0.13 g/1 39 cm/sec 350 1.027594 0.1 g/1 28 cm/sec 400 1.027635 0.05 g/1 14 cm/sec 450 1.027662 0.025 g/1 7 cm/sec 480 1.027679 0.008 g/1 2 cm/sec 520 1.027684 0.003 g/1 1 cm/sec 560 1.027687 0.001 g/1 0.3 cm/sec 586 1.027687 — _ * Tabulated in terms of the suspended sediment con centration required to produce a turbid flow from that depth to the basin floor at 586 m. ** Computed for a 2° slope. # Data courtesy of R. L. Kolpack, Univ. So. Calif., Los Angeles. the suspended load which will overcome the density increase produced by a 1° C decrease at 25° C is>200 mg/l, whereas at 10° C the sus pended load need be only 100 mg/l. The critical question is whether the particle con centrations indicated in Table IV are within the typical range observed near the bottom in the Channel. The data presented in the previous section demonstrate that, even during a period of record introduction of fine-grained terrestrial detritus, near-bottom concentrations of particulate matter were at all times from 5 to 100 times too low. Thus, the transport mechanism proposed by Moore is not supported in Santa Barbara Channel. Specifically, the evidence to confirm this conclusion is as follows: 1. Fine river-borne sediment settles rapidly sea ward of the littoral zone but within a few kilometers of the coast. Particle resuspension occurs at a rate which is controlled by the magnitude of near-bottom turbulent energy. Al though a tremendous quantity of fine material was available for resuspension following the floods, near-bottom particle concentrations decreased rather rapidly to an average of about 10 mg/l in a shelf nepheloid layer 10 to 20 m thick. In agreement with theoretical expectations, bottom nepheloid layers transported across the Ventura Shelf became detached from the sea floor at the shelf break spreading into the slope and basin water column along isopycnal surfaces. Intermediate depth turbid layers generated in this manner commonly were maintained by retarded particle settling at thermoclines of only 0.1° to 0.3° 0. If downslope turbid layer flow were to occur one would expect to observe relatively warm, low salinity water along the bottom or within mid-water turbid layers that moved some dis tance down the slope and then spread along a density discontinuity. In more than 175 STD casts in May, August and December of 1969 (Kol- pack, 1971), no temperature or salinity in versions were found near the bottom. Similarly, nearly 200 transmissometer and temperature pro files obtained in all parts of the area in November 1969, February 1970 and October 1971 showed that the temperature near the bottom gradually or abruptly decreased but never in creased (Figs. 81, 82). In this regard, Moore (1969) cautiously argued that as a turbid layer moved downslope its temperature might change, Figure 81 Water temperature at the bottom in May 1969 (after Kclpack, 1971). Data are from Bissett- Berman Model 9060 STD. 296 120*30’ BO TTO M TEMPERATURE MAY. 1969 SCALE >0 nautical ml. 20 10.0 SANTA BARBARA 7.0 VENTURA OXNARD 6.6 3* otf SAN MIGUEL ISLAND SANTA CRUZ ISLAND 00' ANACAPA IS SANTA ROSA ISLAND ro vo IHO’ OO* Figure 82 Water temperature at the bottom in October 1970. Data are from the transmissometer temperature probe and are accurate to t 0.1°C. 298 IZO'SO1 120*00' B O T T O M T E M P E R A T U R E ( * C ) O C T O B E R , 1 9 7 0 SCALE >0 nauiicol ml, 20 ^ 4 * 3 0 ' STATION LOCATION S A N T A B A R B A R A 8.8 8.0 7 . 2 6.4 6 . 4 V E N T U R A O X N A R D 3 * otf 34* 00' S A N M IG U E L IS L A N D S A N T A C R U Z IS L A N D A N A C A P A IS S A N T A R O S A IS L A N D 1 120*30? 300 presumably through conduction, to that of the surrounding water. Even if the unlikely pos sibility that a 10 to 20 m thick layer could lose heat at a sufficiently rapid rate is granted, one is still faced with the problem of producing an equally great increase in salt content. The only mechanism through which such a salinity change could be effected is physical mixing. Obviously, eddy mixing would dilute the particle suspension with a resulting decline in excess density and loss of driving force. 4. The slow accumulation of flood sediment in the deep basin is compatible with a sediment trans port model involving continuous particle settl ing from mid-water turbid layers. Furthermore, the fine textures of the basin flood layer and the ancient gray layers precludes a high velocity (turbulent) transport mechanism. It must be admitted that Moore (1969) believed that turbid layer flow is confined largely to submarine canyons incising the nearshore slopes along southern California. The transport of fine particles in canyons has not been studied adequately and remains an attractive area for re search. In particular, the distribution, concentrations, and textures of suspended matter should be studied along with canyon hydrography. 301 It Is this writer's opinion that the canyon cur rents reported by Shepard and Marshall (1970) will emerge as important agents of sediment dispersal from the shelf to the nearshore basin floors. Available data on sus- pensate concentrations within submarine canyons are meager. They exhibit the expected increase near the bottom but the highest values (about 10 mg/l) fall far short of those re quired to drive a density flow (Beer and Gorsline, 1971; Felix and Gorsline, 1971). Origin of the Bottom Nepheloid Layer It has been demonstrated that "low-density" turbid layer transport downslope did not occur following the re cord floods of 1969 in the Santa Barbara Channel. There fore, it can be confidently concluded that during years of more normal runoff, this proposed transport mechanism can be dismissed. Furthermore, high excess density turbidity currents are unimportant, if not totally lacking, in the Channel. Thus, the bottom nepheloid layer must be pro duced by either bottom scour or retarded settling of particles introduced from above, or both. It is worthwhile at this point to summarize the most important, typical aspects of the particle distribu tion near the bottom of the Channel, namely: 1. A bottom nepheloid layer is present in all parts of the area with the exceptions of the insular shelf and the crest of Montalvo Ridge. Highest particle concentrations were measured during all surveys over the Ventura Shelf. There appears to be a correlation, at shelf depths, between the concentration of the bottom nepheloid layer and the texture of bottom sedi ments; coarser sediments, such as those cover ing the insular shelf, the mainland shelf south of Point Conception, and the eastern portion of the Anacapa Trough, are associated with rela tively weak transparency reductions near the bottom. The bottom nepheloid layer generally thickens and becomes less concentrated with increasing depth. Although transparency reductions with in the basin waters may be, in part, the re sultant of an increase in dissolved substances, the nepheloid layer is a permanent feature ranging in thickness from <40 m to>l40 m. Resuspension of previously-deposited sediments on the Ventura Shelf was demonstrated. Never theless, much of the particulate matter in the bottom nepheloid layer was eroded at depths of less than 30 m and subsequently transported to other parts of the shelf and Channel. Thus, a large deposit of fine silts and lutlte was retained on the shelf (July 1971) in a broad depression which is too deep to be affected by wave surge and is not directly exposed to the swift Anacapa Current. Those portions of the Channel deeper than 50 m which are demonstrably undergoing periodic scour are: the southern edge of the Ventura Shelf, the Anacapa Trough, and the Point Conception fan. The first two areas are exposed to the Anacapa Current as it flows through the narrow passage bounded by the insular ridge and the mainland shelf. Velo cities at flood tide within this current exceed 0.7 knots and erosion of loosely deposited fine sediments at such velocities is in agreement with the recent work of Postma (1967) and Southard and others (1971). The fine texture of surface sediments on the Point Conception fan (Kolpack, in preparation) indicates that scour and particle resuspension are infrequent. However, erosion of surficial detritus was strongly suggested by the anomalously thick bottom nepheloid layer over the fan in October 1970. Periodic scour by inflowing currents is compatible with the relatively thin layer of flood sediment on the fan. Although resuspension of bottom sediments by 304 benthic organisms doubtless occurs, the presence of a permanent bottom nepheloid layer within the barren Santa Barbara Basin shows that such a mechanism is not a neces sity. Indeed, the strong dependence of erosional "critical velocity" on sediment water content (Postma, 1967) suggests that the importance of the benthos may lie in its maintenance of high water content in surficial sedi ment layers. In sum, the data indicate that the bottom nepheloid layer in the Channel is produced by both particle erosion and retarded settling of detritus introduced from above. At shelf depths and within the constricted Anacapa Trough resuspension and retarded settling combine to generate generally high and variable particle concentrations. Al though the rate of sedimentation on the basin slopes is relatively slow, the presence of a measurable layer of flood sediment denotes that the slopes are sites of net deposition. Thus, It Is concluded that the bottom nepheloid layer over the basin slopes is supplied prin cipally with particles settling from above and slowed in their descent by increased near-bottom turbulence. How ever, the measurement of currents in excess of 35 cm/sec at a depth of 300 m and at 6 m above the mainland slope near Gaviota (P. Fischer, personal communication) strongly suggests that current scour of loosely-deposited fine detritus may significantly augment particle concentrations 305 above the bottom. The ease with which particles are eroded is strongly influenced by the texture of the sedi ment and the water content, both of which control the co hesion of the grains (Postma, 1967). Although recent contributions by Heezen and Hollister (1964) and Southard and others (1971) indicate that mean current velocities on the order of 15 to 35 cm/sec are capable of erosion of silt and clay, in the absence of more complete current information in the Channel, the relative importance of current scour cannot be firmly determined. The permanent particle maxima observed within Santa Barbara Basin is definitely a resultant of retarded settling of the finest particles introduced by gravity settling from intermediate-depth particle maxima. This conclusion is strengthened by the preservation of fine laminae, reflecting the seasonal influx of plankton re mains and terrestrial detritus, within the basin. It is doubtful that such laminations would remain if currents were actively scouring the basin floor. The correlation between bottom nepheloid layer thickness, depth, and the vertical stability of the water column (as indicated by the gradients of temperature and salinity) suggests that the bottom nepheloid layer thickness in deep-sea areas may be a function of water column structure. In particu lar, the thermal gradient in the waters immediately above the bottom in the Channel was found to impose a limit upon the upward mixing of suspended matter. Thus, the conclusion of Eittreim and others (1969) that changes in the thickness of the bottom layer along the margin of the North American Basin are related to changes in the supply of particles is open to question. Additionally, their conclusion that the bottom nepheloid layer in the Atlantic is supplied with particulate matter by turbidity currents is difficult to reconcile with the apparent permanence of the layer. In this regard, the recent measurements of near-bottom currents as great as 26 cm/sec along the New England Continental Rise (Zimmerman, 1971) and the experi mental sediment erosion data of Southard and others (1971) strongly suggest that the Atlantic bottom turbid layer may be supplied with particles scoured from the bottom as well as those settling from above. SUMMARY AND CONCLUSIONS Hydrography The surface distributions of particulate matter, transparency patterns and temperatures and salinities de fine the following currents within the Channel: 1. Northwest flow from Santa Monica Basin through the Anacapa-Oxnard Passage occurs during all seasons but varies in volume transport in re sponse to the seasonality of the "Anacapa” Current. This current sweeps to the northwest across the outer portion of the Ventura Shelf at a mean velocity of 25 cm/sec and can be followed as a distinct surface current along the northern margin of the Channel at least to Gaviota. Suspended sediment samples and beam transmissometer data show that this current is always relatively clear and carries, on the average, less than 0.2 mg/l of inorganic particles. Ash residues are consistently relatively high and are compatible with low values of primary productivity and inorganic nutrients. The importance of this current lies 307 not in a significant introduction of detritus to the Channel but rather in its hydrologic blockage of the passage to southward escape of locally contributed particles and its influence on the shelf circulation. The second major current within the Channel is produced by an intrusion of cool, low salinity California Current water from the west and southwest. In response to seasonal changes in winds and the position of the California Cur rent, the intrusion is at a maximum in the spring and summer and generally restricted to the southwest corner of the area in the fall and winter months. Suspended sediment concen trations range from >1.0 mg/l in a nearshore wind-driven turbid plume rounding Point Con ception to approximately 0.2 mg/l in the south west portion of the Channel. The water in this current is relatively nutrient-rich and, during spring upwelling, plant production commonly exceeds 30 mgC/mV^r. Nevertheless, a large transparency reduction within the high product ivity waters in May was not wholly the result of increased light scattering by organic particles but was probably caused by increased absorption by dissolved organic substances. The confluence of this current with the Anacapa Current results in a permanent counter clockwise eddy in the central Channel south of Gaviota. Surface currents over the mainland shelf are increasingly influenced by local wind stress and heating variations and, thus, are more variable in time and space. Surface tempera tures, however, suggest that net flow along the shelf segment from Point Conception to Pitas Point is to the east and southeast throughout most of the year. This highly variable east ward drift is probably a resultant of prevail ing westerly winds. Lateral gradients of sur face temperature over Ventura Shelf are generally gentle and indicate that currents here are also sluggish (probably <20 cm/sec) except along the southern edge of the shelf which is exposed to the swift Anacapa Current. Circulation over Ventura Shelf is dominated by north and northwest flow over the southern portion to the latitude of Ventura. Between Ventura and Pitas Point this northerly flow converges with a southward flowing current. The convergence results in a wedge of slack water and the turning of current vectors to the west. A second convergence between southward flowing inner shelf currents and the Anacapa Current commonly is present off Oxnard. Subsurface circulation is not well-defined but ap pears to conform to the following patterns: 1. The Anacapa Current extends to the depth of the eastern sill (240 m) with little decrease in mean velocity. Sediments covering the eastern portion of the sill are fine to medium sands containing abundant glauconite. To the west the sill gradually deepens and bottom sediments contain greater proportions of silt and clay. However, at times current velocities are suf ficiently high (perhaps 30-40 cm/sec) to erode fine detritus from the western edge of the sill. 2. Direct current measurements and patterns of surface and subsurface transparency indicate that surface current directions are little changed to a depth of at least 100 m in all parts of the Channel. 3. Subsurface circulation in the western portion of the area involves eastward flow from the open Pacific below about 250 m and to the depth of the western sill (475 m). The distribution of light attenuating substances in July 1971 suggests that currents at 200-250 m describe a counter-clockwise eddy in the central Channel. Santa Barbara Basin water is derived from the low oxygen zone in the Pacific. Recharge of the basin water may occur annually in response to vertical water motion during spring periods of intense upwelling. Currents immediately above the basin floor have been measured at up to 20 cm/sec, and perhaps are driven by inter nal wave motions or tides. Suspended Particulate Matter The floods of January and February of 1969 resulted in a local river contribution of about 70 million tons of suspended sand, silt, and clay. Approximately 56 million tons were introduced to Ventura Shelf by the Santa Clara and Ventura Rivers. Sand and coarser flood detritus was deposited rapidly to form river mouth deltas and bars whereas finer products were initially deposited in a westward-trending wedge beneath the shelf current convergence off Pitas Point. The bulk of the river-borne material (>45 million tons) was retained on the Ventura Shelf within 20 kms of the river mouths and at depths of less than Flood detritus in suspension over the shelf was principally contained in a surface turbid layer which extended to the depth of the season al thermocline (about 20 m) and a more concen trated near bottom turbid layer. Particle con centrations in the surface layer ranged from >10 mg/l near the Santa Olara River to <1.0 mg/l in the central Channel. Concentrations in the bottom nepheloid layer in February 1969 ranged from > 50 mg/l off the river mouth to <10 mg/l at the southern edge of Ventura Shelf. Six months after the floods, surface concentra tions seaward of a 5 to 7 km-wide coastal band of turbid water had decreased to ' ’normal" values of<0.5 mg/l. On the other hand, the bottom nepheloid layer over the shelf remained highly concentrated owing to continual re suspension of flood material by wave surge at depths of less than 30 m and seaward transport by the Anacapa Current. Owing to thermal water stratification, resuspended detritus beyond a nearshore zone approximately 5 to 7 kms wide was confined to the bottom nepheloid layer and to mid-water turbid layers supplied principally by the near-bottom particulate matter. Material resuspended by wave surge at depths of less than 30 m was transported to the west and northwest within the current convergence off Pitas Point and by the Anacapa Current. Deposi tion of the resuspended silt and clay occurred over the middle shelf (30-70 m) within a broad depression bounded to the north by the Rincon Anticlinal trend and to the south by Montalvo Ridge, and within the deep basin to the west. Accumulation of fine silt and clay off Pitas Point is presently occurring in response to the decline in transport power within the shelf current convergence. A measurable flood layer began to form in the deep basin 4 to 6 months after the floods. Mineralogic analyses of the <62jj size fractions of this material demonstrated a nearly un diluted Santa Clara River source. Moreover, comparison of the 1969 flood layer mineralogy with the mineralogies of subsurface basin sedi ments reveals that grey "silt" layers which were previously identified as turbidites are, in fact, flood-year deposits predominantly supplied by the Santa Clara and Ventura Rivers. Inorganic basin sediments accumulating in non flood years, although still predominantly supplied by Santa Clara River material washed from the Ventura Shelf, reveal an increased dilution by other sediment sources. Although these sources cannot be specifically identified, it is probable that the bulk of the dilutant is derived from the turbid surface and subsurface plumes rounding Point Conception and from cur rents flowing into the basin over the western sill. The concentrations of particulate matter re quired to initiate downslope turbid layer density flow were never reached owing to rapid initial deposition of even the finest detritus on the inner portions of the mainland shelf and the inability of near-bottom turbulence to produce concentrations exceeding 10 mg/l at the shelf edge. The bottom nepheloid layer became detached from the sea floor at any increase in the shelf slope. In this manner a series of "stacked" mid-water turbid layers were formed as currents swept to the northwest over the middle and outer Ventura Shelf. A close association of particle maxima and thermoclines as small as 0.1° C developed as detritus spread laterally along isopycnal surfaces. 315 8. The subsurface distribution of particles is predominantly controlled by the lateral spread of material from the bottom nepheloid layer and variation in particle settling rates resulting from vertical changes in thermal gradients and eddy diffusion. All beam transmissometer pro files show a striking association of particle maxima with increases in the thermal gradient. Thus, detritus settles in a step-like manner; temporarily slowed within steep-gradient layers and diffusing more rapidly within gentle- gradient layers. 9. The pattern of flood sediment deposition, near bottom turbid layer concentrations, and the texture of sediments covering the basin slopes combine to indicate that a significant portion of the finest fractions of material swept from the mainland shelf and settling over the slopes is maintained in suspension by increased turbulence and transport power near the bottom. Furthermore, demonstrated scour of the bottom at depths of up to 380 m combined with measure ments of current velocities exceeding 35 cm/sec at 300 m suggest that particle concentrations in the bottom nepheloid layer are, at times, in creased by erosion of previously-deposited fine 316 detritus. Thus, the texture of sediments on the basin slopes are intermediate between those on the adjoining shelves and basin floor. In addition, the rate of sedimentation is rela tively slow owing to the continuous by-passing of much of the fine silt and clay. 10. Currents below sill depth in the Santa Barbara Basin are sufficiently strong to produce a "reservoir" of fine silt and clay particles. Nevertheless, this material cannot escape from the basin and must represent a dynamic equili brium controlled by vertical eddy diffusion, particle settling rates, and particle supply from intermediate depth particle maxima. Con sequently, the relatively coarse-grained particles are less effected by the turbulence and accumulate more evenly over the basin floor. On the other hand, the settling and deposition of finer lower density particles will be re tarded until transport power decreases within protected topographic depressions. There is no need to invoke lateral gravity-controlled flow of suspended matter in order to explain the topographic control of sedimentation rates. 11. Only approximately 1 cm of red flood sediment was deposited on the large fan forming the 317 slope to the south of Point Conception. Al though the fan is presently aggrading, the rate of sedimentation is only about one-third of that on the basin floor and, thus, is not compatible with the size of this sediment body. The fan is a relict of the Pleistocene. It is tentatively proposed that, during glacially- lowered sea level stands, fine and coarse grained particles introduced by streams to the north of Point Arguello could move unimpeded to the south resulting in a considerably higher rate of sedimentation below the relatively slack water produced by converging currents from the north and east in the immediate lee of the promontory. 12. The preparation of a suspended sediment budget for the Channel was not feasible owing to the "atypical" flood discharge. However, from data collected prior to the flood and more than one year after the flood, it is probable that the magnitudes of the important fine particle sources are within the following ranges: a. Local river contribution is dominated by the Santa Clara River and totals between 1 and 1.5 million tons annually. However, the discharge in any given year may deviate above or below this mean by a factor of about 50. Phytoplankton production within the Channel occurs principally in May and June when most of the approximately 0.6 to 1.0 million metric tons of biogenic material contri buted each year is generated. This source is considerably less variable than stream supply. Eolian material is introduced principally by the fall Santana winds and totals from 50,000 to more than 100,000 tons/year. Transport of suspended matter by the two major currents entering the Channel at its opposite ends may total more than 3 million metric tons annually. However, particle sizes of the inorganic detritus carried by these currents suggests that only the turbid plume entering the area from the northwest is a significant source of sediment. This is in agreement with mineralogic data show ing that Santa Clara River exerts pre dominant control over the composition of all lithogenous Channel sediments. REFERENCES CITED 319 REFERENCES Allan Hancock Foundation, An Oceanographic and Biological Survey of the Southern California Mainland Shelf, Publ. No. 27, Calif. State Water Quality Control Board, Sacramento, Calif., 232 p., I965. Armstrong, F. A. J., Silicon, in: Chemical Oceanography, vol. 1, p. 409-^32, J. P. Riley and G. Skirrow, editors, Academic Press, 1965. Babcock, B. A., Analysis of wind blown sediment, unpubl. report, Dept. Geol., Univ. So. Calif., 16 p., 1957. Bagnold, R. A., Mechanics of marine sedimentation, in: The Sea, vol. 5 , M. in. Hill, editor, Interscience, New York, p. 507-528, 1963. Bailey, T. L., and R. H. Jahns, Geology of the Transverse Range Province, southern California, Bull. 170, Calif. Div. Mines, San Francisco, 1954. Bandy, 0. L., R. E. Casey, and R. C. Wright, Late Neogene planktonic zonation, magnetic reversals, and radio- metric dates, Antarctic to the tropics, in Antarctic Oceanology I, edited by J. L. Reid, Antarctic Res. Series, 15, Amer. Geophys. Un., Wash., D. C., 1971. Banse, K., C. P. Falls, and L. A. Hobson, A gravimetric method for determining suspended matter in sea water, using Millipore filters, Deep-Sea Res., vol. 10, p. 639-642, 1963. Barnes, P. W., Marine geology and oceanography of Santa Cruz Basin, California, unpubl. Ph.D. thesis, Univ. So. Calif., Los Angeles, 1970. Beardsley, G. F., Jr., H. Pak, K. Carder, and B. Lundgren, Light scattering and suspended particles in the eastern equatorial Pacific Ocean, J. Geophys. Res., vol. 75, 2837, 1970. Beer, R. M. and D. S. Gorsline, Distribution, composition, and transport of suspended sediment in Redondo Sub marine Canyon and vicinity, California, Marine Geol., v. 10, p. 153-176, 1971. 320 321 Berger, W. and A. Soutar, Planktonic foramlnlfera: Field experiment on production rate, Science, vol. 156, p. 1495-1497, 1967. Booth, J. A., Sediment dispersion in the Northern Channel Islands Passages, California, unpuhl. M.S. thesis, Univ. So. Calif., Los Angeles, 1971. Bowden, K. F., Turbulence, in: The Sea, vol. 1, p. 802- 825, edited by M. N. Hill, Interscience Publ., 1962. Calvert, S. E., Accumulation of diatomaceous silica in the sediments of the Gulf of California, Bull. Geol. Soc. Amer., vol. 77, p. 569-596, 1966. Carder, K., G. F. Beardsley, Jr., and H. Pak, Light scat tering vectors, particle size distributions, and oxygen profiles in the eastern equatorial Pacific, 'The Ocean World,1 Joint Oceanography Assembly, Science Council of Japan, 166, 1970. Eittreim, S. L., M. Ewing, and E. M. Thorndike, Suspended matter along the continental margin of the North American Basin, Deep-Sea Res., vol. 16, p. 613-624, 1969. Emery, K. 0., Source of water in basins off southern California, Jour. Marine Res., vol. 13» p. 1-21, 1954-. Emery, K. 0., The Sea off Southern California, J. Wiley and Sons, Inc., New York, 366 p., I960. Emery, K. 0. and J. Hulsemann, Relationships of sediments, life, and water in a marine basin, Deep-Sea Res., vol. 8, p. 165-180, 1962. Ewing, M. and E. M. Thorndike, Suspended matter in deep ocean water, Science, vol. 147, p. 1291^1294, 1965. Ewing, M. and S. Connary, Nepheloid layers in the North Pacific in: Geological Investigations of the North Pacific, GSA Memoir, edited by J. Hays, Geol. Soc. Amer., New York, 1970. Felix, D. W. and D. S. Gorsllne, Newport submarine canyon, California: an example of the effects of shifting loci of sand supply upon canyon position, Marine Geol., vol. 10, p. 177-198, 1971. 322 Fleischer, P., Mineralogy of hemipelaglc basin sediments, California Continental Borderland, unpubl. Ph.D. thesis, Univ. So. Calif., Los Angeles, 1970. Gorsline, D. S., Marine geology of the California Con tinental Borderland, Report No. USC 68-1, Univ. So. Calif., Los Angeles, 1968. Gorsline, D. S. and K. 0. Emery, Turbidity current deposits in San Pedro and Santa Monica Basins off southern California, Bull. Geol. Soc. Amer., vol. 70, p. 279-290, 1959. Gorsline, D. S., D. E. Drake, and P. W. Barnes, Holocene sedimentation in Tanner Basin, California Continental Borderland, Bull. Geol. Soc. Amer., vol. 79, p. 659- 674, 1968. Griggs, G. B., A. G. Carey, Jr., and L. D. Kulm, Deep-sea sedimentation and sediment fauna interaction in Cascadia Channel on the Cascadia Abyssal Plain, Deep- Sea Res., vol. 16, p. 157-170, 1969. Hamilton, R. M., R. F. Yerkes, R. D. Brown, Jr., R. 0. Burford, and J. M. DeNoyer, Seismicity and associated effects, Santa Barbara Region, in: Geology, Petroleum Development, and Seismicity of the Santa Barbara Channel Region, California, Prof. Paper 679, U. S. Geol. Survey, p. 1-13, 1969. Handin, J. W., The source, transportation, and deposition of beash sediment in southern California, Dept, of Army, Corps of Engineers, Beach Erosion Board, Tech. Memo. 22, 113 p., 1951. Heezen, B. C. and C. D. Hollister, Deep-sea current evidence from abyssal sediments, Marine Geology, vol. 1, p. 141-174, 1964. Hidaka, K., Calculations of upwelling: Records of Oceano graphic works in Japan, vol. 6, p. 11-15, 1961. Hjulstrom, J., Transportation of detritus by moving water, in: Recent Marine Sediments, pp. 5-31, P. Trask, editor, Spec. Publ. No. 4, Soc. Econ. Paleontol. and Mineralogists, Tulsa, Okla., 1939. 323 Holmes, R. W., Surface chlorophyll A, surface primary production, and zooplankton volumes in the north eastern Pacific Ocean: Symposium on Measurement of Primary Production in the Sea, Conseil International pour ^Exploration de la Mer, Bergen, 1957. Howe, M. R. and R. I. Tait, Further observations of thermohaline stratification in the deep ocean, Deep- Sea Res., vol. 17, p. 963-972, 1970. Hulsemann, J. and K. 0. Emery, Recent sediments of Santa Barbara Basin, Jour. Geol., vol. 69, p. 279-291, 1961. Ingle, J. 0., Jr., The Movement of Beach Sand. Elsevier Publ. Co., Amsterdam, 221 p., 1966. Inman, D. L., Sorting of sediments in the light of fluid mechanics, Jour. Sed. Petrol., vol. 19, p. 51-70, 1949. Inman, D. L., R* J. Tait, and 0. E. Nordstrom, Mixing in the surf zone, J. Geophys. Res., vol. 76, p. 3493- 3514, 1971. Ippen, A. T., Sedimentation in estuaries, in: Estuary and Coastline Hydrodynamics, p. 648-672, A. T. Ippin, editor, McGraw-Hill Book Co., New York, I966. Jerlov, N. G., Particle distribution in the ocean, Rept. Swedish Deep-sea Exped., 3, p. 73-97, 1953a. Jerlov, N. G., Influence of suspended and dissolved matter on the transparency of sea water, Tellus, vol. 5» p. 59-65, 1953b. Jerlov, N. G., Maxima in the vertical distribution of particles in the sea, Deep-Sea Res., vol. 5» p. 178- 184, 1959. Jerlov, N. G., Optical Oceanography. Elsevier Publ. Co., New York, 194 p., 1968. Johnson, D. A. and T. C. Johnson, Sediment redistribution by bottom currents in the central Pacific, Deep-Sea Res., vol. 17, p. 157-171, 1970. Johnson, J. W., Dynamics of nearshore sediment movement, Bull. Amer. Assoc. Petrol. Geologists, vol. 40, p. 2211-2232, 1956. 324 Johnson, J. W. and P. S. Eagleson, Coastal Processes, in: Estuary and Coastline Hydrodynamics, p. 404-492, A. T. Ippen, editor, McGraw-Hill Book Co., New York, 1966. Kolpack, R. L., Oceanography and sedimentology of Drake Passage, Antarctica, unpubl. Ph.D. thesis, Univ. So. Calif., Los Angeles, 1968. Kolpack, R. L. (editor), Biological and Oceanographical Survey of the Santa Barbara Channel Oil Spill, Vol. II. Physical, Chemical and Geological Studies, Allan Han cock Foundation, Univ. So. Calif., 1971. Krumbein, W. C. and P. P. Pettijohn, A Manual of Sedi mentary Petrography, Appleton-Century-Crofts, Inc., New York, 549 p., 1938. LaFond, E. C., Internal waves, in: The Sea, vol. 1, p. 731-751» edited by M. N. Hill, Interscience Publ., 1962. Le Pichon, X., S. L. Eittreim, and W. J. Ludwig, Sediment transport and distribution in Argentine Basin, 1. Antarctic bottom current passing through the Falkland fracture zone, Phys. Chem. Earth, 8, 1971. Lisitzyn, A. P., Distribution and composition of suspended material in the sea and ocean, in: Proceedings of Conference on Recent Sedimentation in the Sea and Ocean, Moscow, 1961. Lisitzyn, A. P., Sedimentation in the Ocean, SEPM, Spec. Publ., in press. Mackensie, F. T. and R. M. Garrels, Silicates: re activity with sea water, Science, vol. 150, p. 57-58, 1965. Meade, R. H., Errors in using modern stream-load data to estimate natural rates of denudation, Bull. Geol. Soc. Amer., vol. 80, p. 1265-1274, 1969. Manhelm, F. T., R. H. Meade, and G. C. Bond, Suspended matter in surface waters of the Atlantic Continental Margin from Cape Cod to the Florida Keys, Science, vol. 167, P. 371-376, 1970. Menzel, D. W. and F. F. Vaccaro, The measurement of dis solved organic and particulate carbon in sea water, Limnol. Oceanog., vol. 9» p. 138-142, 1964. 325 Millipore Corporation, Filters and associated apparatus, Catalog MF-64, 1965. Moore, D. G., Reflection profiling studies of the Cali fornia Continental Borderland: Structure and Quaternary Turbidite Basins, Spec. Paper 107, Geol. Soc. Amer., 142 p., 1969. Ogurl, M. and R. Kantor, Primary productivity in the Santa Barbara Channel, in: Straughan, D. (ed.), Bio logical and Oceanographical Survey of the Santa Barbara Channel Oil Spill, University of Southern California, Los Angeles, p. 17-48, 1971. Osterberg, C., A. G. Carey, and H. Curl, Acceleration of sinking rates of radionuclides in the ocean, Nature, vol. 200, p. 1276-1277, 1964. Pak, H., The Columbia River as a source of marine light scattering particles, unpubl. Ph.D. thesis, Oregon State University, Corvallis, 1970. Pak, H., G. F. Beardsley, Jr., and W. Plank, Near bottom nepheloid layers in the eastern equatorial Pacific Ocean, 'The Ocean World,1 Joint Oceanographic Assembly, Science Council of Japan, 164, 1970a. Pak, H., G. F. Beardsley, Jr., and W. Plank, The bottom nepheloid layer in the Northeast Pacific Ocean, Trans. Amer. Geophys. Union, 51» P» 766, 1970b. Pak, H., J. Ronald V. Zaneveld, and G. F. Beardsley, Jr., Mie scattering by suspended clay particles, J. Geo phys. Res., vol. 76, p. 5065~3069, 1971. Parsons, T. R., Suspended matter in ocean water, in: Progress in Oceanography, v. 1, edited by M. Sears, p. 205-239, Pergamon Press, 1963. Petzold, T. H. and R. W. Austin, An underwater transmisso- meter for ocean survey work, Tech. Rep. Scrlppts Inst. Oceanogr., Ref. 68-9, 5 p., 1968. Postma, H., Sediment transport and sedimentation in the estuarine environment, in Estuaries, edited by G. H. Lauff, American Association for the Advancement of Science, Publ. 83, p. 158-179, 1967. 326 Reid, J. L., Jr., G. I. Roden, and J. G. Wyllie, Studies of the California Current system, California Co operative Fisheries Investigations, Calif. Dept. Fish and Game, p. 27-56, 1958* Revelle, R. and F. P. Shepard, Sediments off the California coast, in: Recent Marine Sediments, edited by P. Trask, Spec. Publ. No. 4, Soc. Econ. Paleontologists and Mineralogists, Tulsa, Okla., p. 245-282, 1939. Revelle, R., T. R. Folsom, E. D. Goldberg, and J. D. Isaacs, Nuclear Science and Oceanography, Proc. 1st Intern. Conf. Peaceful Uses of Atomic Energy, U. N., New York, v. 13, p. 371-380, 1955. Riley, G. A., H. Stommel, and D. F. Bumpus, Quantitative ecology of the plankton of the western North Atlantic, Bull., Bingham Oceanog. Coll., vol. 12, p. 1-169, 1949. Rittenberg, S. C., K. 0. Emery, and W, L. Orr, Regenera tion of nutrients in sediments of marine basins, Deep- Sea Res., vol. 3, p. 23-45, 1955. Rodolfo, K. S., Suspended sediment in southern California waters, unpubl. M. S. thesis, Univ. So. Calif., Los Angeles, 135 p., 1964. Rodolfo, K. S., Annual suspended sediment supplied to the California Continental Borderland by the southern California watershed, Jour. Sed. Pet., vol. 40, p. 666-671, 1970. Scholl, D. W., Geology and surrounding recent marine sedi ments of Anacapa Island, unpubl. M.S. thesis, Univ. So. Calif., 105 pp., 1959. Shepard, F. P. and N. Marshall, Currents in Scripps and La Jolla Submarine Canyons, Science, vol. 165, p. 177-178, 1970. Southard, J. B., R. A. Young, and C. D. Hollister, Experi mental erosion of calcareous ooze, J. Geophys. Res., vol. 76, p. 5903-5909. Spencer, D. W. and P. L. Sachs, Some aspects of the dis tribution, chemistry, and mineralogy of suspended matter in the Gulf of Maine, Marine Geol., vol. 9, p. 117-136, 1970. 327 Stevenson, R. E., The marine climate of southern Cali fornia, in; Oceanographic Survey of the Continental Shelf Area of Southern California, p. 2-58, Publ. No. 20, Calif. State Water Quality Control Board, Sacra mento, Calif., 1959. Stevenson, R. E., E. Uchupi, and D. S. Gorsline, Some Characteristics of sediments on the mainland shelf of southern California, in: Oceanographic Survey of the Continental Shelf Area of Southern California, p. 59- 109, Publ. No. 20, Calif. State Water Quality Control Board, Sacramento, Calif., 1959. Strickland, J. D. H. and T. R. Parsons, A practical hand book of seawater analysis, Fisheries Res. Board Canada, Bull. 167, 311 p., 1968. Swartzlose, R. A., Surface Currents off Southern California, Calif. Cooperative Oceanic Fisheries Investigations, 33rd Ann. Conf., Indian Wells, California, 1970. Sverdrup, H. U. and R. H. Fleming, The waters off the coast of southern California, March to July, 1937, Scripps Inst. Oceanogr., Bull., vol. 4, p. 261-378, 1941. Sverdrup, H. U., M. W. Johnson, and R. H. Fleming, The Oceans, Prentice Hall, 1087 p., 1942. Swift, D. J. P., J. R. Schubel, and R. E. Sheldon, Size analysis of suspended fine sediments, Jour. Sed. Petrol., in press. Timofeyeva, V. A. and G. G. Neuymin, Theoretical and experimental work on marine optics in the Soviet Union, Izv., Atmos. Oceanic Phys., vol. 4, p. 1305, 1968. Trask, P. D., Movement of sand around southern California promontories, Dept, of Army, Corps of Engineers, Beach Erosion Board, Tech. Memo. 76, 60 p., 1955. Turner, J. S., Salt fingers across a density interface, Deep-Sea Res., vol. 14, p. 599-611, 1967. Vanoni, V. A., N. H. Brooks, and J. F. Kennedy, Lecture notes on sediment transportation and channel stability, Report No. KH-R-1, Keck Laboratory of Hydraulics and Water Resources, Calif. Inst. Tech., 1961. 328 Vedder, J. G., H. C. Wagner, and J. E. Schoellhamer, Geologic framework of the Santa Barbara Channel region, in: Geology, Petroleum Development, and Seismicity of the Santa Barbara Channel Region, California, U.S.G.S., Prof. Paper 679, p. 1-11, 1969. Weaver, D. W., D. P. Doerner, and B. Nolf, Geology of the northern Channel Islands, Spec. Publ., Am. Assoc. Petrol. Geol., 200 p., 1969. Whitehouse, U. G., L. M. Jeffrey, and J. D. Delbrecht, Differential settling tendencies of clay minerals in saline waters, Clays and Clay Minerals, 7th Conf., Pergamon Press, New York, p. 1-80, i960. Wildharber, J. L., Suspended sediment over the continental shelf off southern California, unpubl. M.S. thesis, Univ. So. Calif., Los Angeles, 1966. Wimberley, C. S., Sediments of the southern California mainland shelf, unpubl. Ph.D. thesis, University of Southern California, Los Angeles, 1964. Zenk, W., On the temperature and salinity structure of the Mediterranean water in the Northeast Atlantic, Deep- Sea Res., vol. 17, p. 627-631, 1970. Zimmerman, H. B., Bottom currents on the New England Continental Rise, J. Geophys. Res., vol. 76, p. 5865- 5876, 1971. APPENDICES A P P E N D IX A S ta tio n L o ca tio n s 330 120* 30* 34- o o 1 STATION LOCATIONS JANUARY, 1969 SCALE O 5. iO nautical m i 1 0 1 5 ____ 20 25 kilometers 34*30* 119*30' 12618 ^ ‘627 636 637 °638 645 SANTA BARBARA 642 °643 644 0 648 °646 =649 650 °651 652 °653 v'vYENTURA 655 658 604 » o \ OXNARD 659 o 9 6 0 6 ° 6 03 SAN MIGUEL ISLAND 0 12614 12612 o 1 2 6 1 1 o610 o609 SANTA CRUZ ISLAND SANTA ROSA ISLAND 660 602 °601 »661 o600 ANACAPA IS. . 34* 00’ 120*30* 120*00' 119*30* 120*30’ 120*00* STATION LOCATIONS MAY . 1969 S C A LE ■ 0 nautical mi. ,34*30* 12983 S A N T A B A R B A R A .12968 o13013 12984 12970 12982 .13025 13031 013030 13011 12985 1 3 0 3 2 12971 13026 12981 v V E N T U R A 13014 12986 ,13010 12980 .13015 12972 13027 12987 13009 O X N A R D 12973 .13028 1 3 0 1 6 13005 .13008 1 3 0 22 1 3 0 2 0 O 12974 13017 013023 13006 ,12978 ,13007 13029 o 1 3 0 2 4 o 13018 ,12975 12977 3 * o t f S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D A N A C A P A IS . t S A N T A R O S A IS L A N D .12976 120*30' 120*00' 120*00* STATION LOCATIONS S C A LE lO nouficol mi. 20 34*30* JULY , 1969 JI9- 30' S A N T A B A R B A R A ° 1 6 0 °161 °1 6 2 1 3 1 49 1 3 1 59 13170 ’1 6 3 1 3 1 5 0 1 3 1 5 8 1 3 1 6 8 1 3 1 6 4 13151 V E N T U R A 13171 •1 3 1 8 4 13172 „ 1 3 1 8 3 1 3 1 73 0 1 3 1 82 •1 3 1 7 4 • 1 3 1 7 5 13181 1 3157 1 3 1 6 7 13152 1 3 1 6 5 1 3 1 5 6 O X N A R D 13153 1 3 1 5 5 1 3 1 66 1 3 1 8 0 1 3 1 5 4 o 1 3 1 9 3 1 3176 1 3 1 9 4 1 3 1 79 13177 1 3 1 9 5 1 3178 A N A C A P A IS . 341 O t f S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D t . S A N T A R O S A IS L A N D 120*30' 1 2 0 * 0 0 ’ STATION LOCATIONS AUGUST. 1969 S C A LE ■ 0 nautical mi. IS kilometers 3 4 *3 0 ' 13334 13320 S A N T A B A R B A R A 13333 13351 13347 13332 13321 1 3 3 4 8 1 3 3 5 0 13335 0 1 3 3 4 9 13346 1 3 3 6 4 13336 13322 13331 V E N T U R A 1 3 3 6 5 1 3 3 6 3 o 1 3 3 6 6 13345 13323 13330 13337 ,13344 1 3 3 7 3 13338 13324 13329 o 1 3 3 5 5 . 1 3 3 5 7 ,13343 13371 1 3 3 5 7 o 1 3 3 5 6 1 3 3 7 4 1 3 3 7 0 13339 13342 1 3 3 6 0 1 3 3 2 7 13341 o 1 3 3 6 8 0 1 3 3 6 9 ,13328 1 3 3 5 9 13340 ,13326 3 4 O t f S A N T A C R U Z IS L A N D S A N M IG U E L IS L A N D A N A C A P A IS . S A N T A R O S A IS L A N D 1 19*30’ 120*30' 120*00' S T A T IO N LO C A TIO N S SCALE 10 nautical mi. 34* 3 0' NOVEMBER, 1969 20 25 kilom eters ,3 4 *3 0 ' JI9* 30' 013551 013552 SANTA BARBARA 13548 o543 13536 o13562 013561 o13560 13547 o542 13553 013563 013564 013565 13544 13546 13537 013569 13570 13541 13545 o13550 o13554 13571 013572 13576 13538 13575 . VENTURA 13559 013568 013566 5 8 6 V O o' 5 8 5 587 013567 13539 13573 13574 13577 013578 13555 13558 o 5 8 8 \ 5 8 4 o \ o583 589 \ o582 o590 OXNARD 13540 13579 13556 013557 13593 13580 13591 13581 013592 ANACAPA IS. 34* 00' SAN MIGUEL ISLAND SANTA CRUZ ISLAND SANTA ROSA ISLAND 120*00* 119*30' 120*00* S T A T IO N LOCATIONS SCALE (0 nautical mi. 34- 30* 2 0 34-30' DECEMBER, 1969 SANTA BARBARA 13656 13651 13648 • 13673 o674 13688 o675 o 6 4 4 o 6 4 6 6 4 3 6 4 5 6 8 7 13657 13649 13647 13652 13672 13685 13653 13650 s . ’- VENTURA 13658 13689 13684 13671 13686 o690, 13663 13659 13683 13654 13670 OXNARD 13679 o13691 13682 13660 13681 13655 13569 13664 13680 13696 13692 13678 13666 °13667 13662 13668 13695 o13676 13665 o13677 SANTA CRUZ ISLAND SAN MIGUEL ISLAND ANACAPA IS. V SANTA ROSA ISLAND L j J ON 120*00' 120* 30' I 120*00' STATION LOCATIONS FEBRUARY, 1970 13832 13836 13861 13860 13824 13829 13862 13863 13864 13871 13870 13869 1 3 8 6 8 13823 13872 13883 13873 13884 13874 13885 13859 13865 1 3 8 6 7 13866 13875 13886 13876 SCALE 0 5. 10 nautical m i 20 25 kilometer* 34*30 119*30' SANTA BARBARA 13821 13800 13801 13815 13802 13929 o13805 VENTURA o 13810 13916 013811 o13804 OXNARD 13881 013816 13192 o13901 013853 13852 13840 o 1 3 9 0 2 13838 13839 13842 O13930 o13912 o13850 013849 o938 34 o o f " SAN MIGUEL ISLAND SANTA CRUZ ISLAND SANTA ROSA ISLAND 013857 0 9 3 2 937 848 ANACAPA IS. 9 0 4 931 o13903 . 34* 00' 120*30' I __ 1 2 0 * 0 0 ' I_ 119*30' VJ -o 120*30' S T A T IO N L O C A T IO N S SCALE tO noulicol mt. O C T O B E R , 1 9 7 0 2 0 14802 S A N T A B A R B A R A 14801 14810 14793 14809 14800 14811 14792 14803 14781 14794 14812 14782 14791 14783 VENTURA 14790 014780 14804 14773 14805 win 14795 14784 14774 14789 14808 14779 14798 14796 14815 O X N A R D 14785 14772 14814 14775 14786 14817 14778 14797 14776 14806 14787 14788 14807 14777 14770 3 * O t f 34* 00' S A N M IG U E L IS L A N D S A N T A C R U Z IS L A N D A N A C A P A IS . t S A N T A R O S A IS L A N D 34* O t f " 120*30* I 1 2 0 * 0 0 ' SCALE ■0 nauticol m i. STATION LOCATIONS JULY, 1971 (3) 15857 15856 (2) (4) T 1 5 848 15866 | / ? 4RORD 15855 / 1 5 8 5 8 • 158' 4 g 15867 I T J 5 8 6 5 I arr r a I j J £ 8 5 9 _ 3 ? £ l_ _ 1 5 8 5 0 15864 15^ 6 0 15853 f - I ? • 15851 15863 I | 15861 15Q52 15862 SAN MIGUEL ISLAND . 8 4 7 "15872 1 5 kilom eters 34*30' 119*30' SANTA BARBARA VENTURA OXNARD • 8 4 5 844 * 8 4 2 ^ 3 4 . 8 4 3 * 8 4 1 _ . * 8 3 5 . 8 3 0 8 4 0 £ 3 6 . 8 2 9 * 8 2 4 p o q * 8 2 8 . 8 2 5 * 8 3 7 • 8 2 7 » 8 2 6 5874 *838 ANACAPA IS. SANTA CRUZ ISLAND SANTA ROSA ISLAND 34* 00' 120*30' 1 2 0 * 0 0 ' 339 A P P E N D IX B Flood sediment discharge data for Santa Clara and Ventura Rivers. These data were kindly provided by Mr. Karl Kroll of the U. S. Geological Survey, Garden Grove, California. 3^0 DAILY SU SPEN D ED SEDIM ENT 3*U SANTA CLARA AND VENTURA RIVERS SANTA CLARA RIVER January- Mean Discharge (cfs) Mean Concentration (mg/1) Load (tons) 18 0 -- 0 19 1700 4550 55200 20 5630 12100 243000 21 32100 44000 4850000 22 5680 15500 244000 23 2480 5330 37900 24 5630 13900 247000 25 74300 61300 14300000 26 25800 24500 1940000 27 7350 7200 151000 28 3770 5450 56100 29 2530 4350 30000 30 1710 2690 12500 31 1110 1730 5260 TOTAL 169790 -- 22171960 February 1 770 1100 2290 2 740 690 1380 3 710 430 824 4 704 260 494 5 698 160 302 6 10200 41500 1340000 7 2930 14900 126000 8 1800 3300 16000 9 1710 2100 9700 10 1660 2000 8960 11 1550 2000 8370 12 1440 2100 8160 13 1410 2160 8220 14 1160 2100 6580 15 1330 3640 14700 16 1090 5090 15500 17 946 3750 9580 18 946 3500 8940 19 946 3540 8810 20 864 3400 7930 21 853 3900 9390 22 1740 11400 53800 F eb ru ary (continued) M ean D isch a rg e (cfs) M ean C oncentration (m g/1) Load (tons) 23 10400 29900 1330000 24 23500 35800 2750000 25 92300 69200 20400000 26 19900 18300 1060000 27 11800 9700 313000 28 10700 8790 262000 TOTAL 204797 -- 27780930 March 1 1300 960 3370 2 1100 750 2230 3 900 660 1600 4 650 824 1350 5 530 940 1350 6 440 1110 1320 7 410 1820 2010 8 390 470 495 9 380 300 308 10 370 2050 20,50 11 360 2400 2330 12 330 2510 2240 13 270 3360 2450 14 220 3800 2260 15 195 1200 632 16 170 1100 505 17 150 2970 1200 18 140 3200 1210 19 130 3100 1090 20 110 2970 882 21 105 800 227 22 100 700 189 23 98 2570 680 24 98 2450 605 25 96 2700 700 26 94 2820 716 27 93 2600 653 28 92 2390 594 29 95 800 205 30 98 600 159 31 100 1900 513 TOTAL 9636 -- 36558 3^3 April Day M ean D isc h a r g e (cfs) 1-15 16-30 TOTAL 1386 933 2319 M ean C oncentration (m g/1) Load (tons) 3814 1436 5252 VENTURA RIVER January 18 19 20 21 22 23 24 25 26 27 28 29 30 31 TOTAL 0 1590 893 6800 1500 500 2000 20000 13000 5000 2800 2000 1300 900 58283 5070 2470 3200 500 5600 3500 2500 1900 1300 900 0 65000 15600 460000 13000 675 30200 2200000 770000 47300 18900 10300 4560 2190 2657725 February 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 600 500 450 400 600 3500 1700 1100 600 350 200 150 130 128 127 126 125 660 500 420 440 900 6000 1500 1300 1300 1300 1300 1300 1100 900 700 600 500 1070 675 510 475 1460 56700 6890 3860 2110 1230 702 527 386 311 240 204 169 F eb ru ary (continued) Day M ean D isc h a r g e (cfs) M ean C oncentration (m g/1) Load (tons) 18 122 500 165 19 119 500 161 20 117 400 126 21 115 400 124 22 113 640 195 23 2000 -- 42000 24 14000 -- 1100000 25 17000 --- 1600000 26 5000 7600 103000 27 2300 3000 18600 28 1500 1600 6480 TOTAL 53172 -- 2948370 March 1 9080 5330 131000 2 6380 4600 79200 3 4920 4300 57100 4 4000 4050 43700 5 3290 3800 33800 6 2800 3510 26500 7 2340 2610 16500 8 2170 2000 11700 9 1940 1680 8800 10 1780 1650 7930 11 1670 1800 8120 12 1620 2160 9450 13 1590 1820 7810 14 1440 2060 8010 15 1240 1800 6030 16 1110 1220 3660 17 1050 1300 3690 18 1040 1700 4770 19 1120 1800 5440 20 1180 1710 5450 21 1180 1780 5670 22 1100 2100 6240 23 1010 2500 6820 24 967 2620 6840 25 981 2100 5560 26 953 1650 4250 27 932 1300 3270 28 1010 1500 4090 29 876 1000 2370 F eb ru ary (continued) M ean D isch a rg e (cfs) M ean C oncentration (m g/1) Load (tons) 18 122 500 165 19 119 500 161 20 117 400 126 21 115 400 124 22 113 640 195 23 2000 -- 42000 24 14000 -- 1100000 25 17000 -- 1600000 26 5000 7600 103000 27 2300 3000 18600 28 1500 1600 6480 TOTAL 53172 -- 2948370 March 1 9080 5330 131000 2 6380 4600 79200 3 4920 4300 57100 4 4000 4050 43700 5 3290 3800 33800 6 2800 3510 26500 7 2340 2610 16500 8 2170 2000 11700 9 1940 1680 8800 10 1780 1650 7930 11 1670 1800 8120 12 1620 2160 9450 13 1590 1820 7810 14 1440 2060 8010 15 1240 1800 6030 16 1110 1220 3660 17 1050 1300 3690 18 1040 1700 4770 19 1120 1800 5440 20 1180 1710 5450 21 1180 1780 5670 22 1100 2100 6240 23 1010 2500 6820 24 967 2620 6840 25 981 2100 5560 26 953 1650 4250 27 932 1300 3270 28 1010 1500 4090 29 876 1000 2370 M arch (continued) Day M ean D isch a rg e (cfs) M ean C oncentration (m g/1) Load (tons) 30 869 800 1880 31 848 600 1370 TOTAL 62486 - - - 527020 April 1-14 7777 - - - 7576 15-30 903 - - - 717 TOTAL 8680 8293 APPENDIX C Suspended particulate matter filtration data. JANUARY 20-24, 1969 Station Depth Sample Vol(l) Wt./I(mg) Ash % Pilte: 12600 0 3.85 1.1 _ 0.3u 12601 0 3.74 0.56 - 11 12602 . 0 3.70 1.0 - it 12602 22 3.40 4.3 - 11 12603 0 3.56 1.3 - it 12603 18 3.90 5.9 - ti 12604 0 3.85 15.3 - 11 12605 0 3.90 1.2 - it 12605 18 3.52 12.1 - 11 12606 0 3.82 0.8 - 11 12606 23 3.80 5.9 - 11 12607 0 3.90 0.9 it 12610 0 3.98 0.4 - 11 12610 30 3.00 1.1 - 11 12611 0 3.94 0.3 - 11 12612 0 3.00 1.6 - 11 12613 0 3.98 - n 12614 0 2.50 0.4 - n 12615 0 2.50 0.6 - it 12616 0 2.55 1.8 - 11 12617 0 2.50 3.2 - ti 12618 0 2.20 2.1 - it 12619 0 1.50 1.5 - ti 12622 0 2.00 2.6 - 11 12622 24 1.95 4.6 - n 12625 0 1.90 1.9 - ti 12627 0 1.80 2.4 - n 12636 0 2.00 4.2 - 11 12637 0 2.20 3 *3 — 11 12638 0 2.50 2.0 - n 12639 0 2.20 2.0 - •1 12640 0 2.30 1.4 - n 12641 0 2.30 2.8 — 11 12642 0 2.20 3.9 - it 12643 0 1.90 2.3 - it 12644 0 2.00 3.2 - it 12645 0 2.50 7.7 - it 12646 0 1.80 3.3 - ti 12647 0 2.30 3.5 - 11 12648 0 1.80 4.1 - ti 12649 0 2.40 2.5 - n 12650 0 2.30 3.6 - 11 12651 0 2.05 4.3 - ti 12652 0 1.90 2.1 - ti 12653 0 2.00 6.1 - ti 12654 0 1.90 3.1 - 11 12655 0 1.80 4.4 - it 12656 0 1.80 3.9 - it 3^8 MAY 1969 Station Depth(m) Sample Vol(l) Wt/1(: 12968 0 4.0 0. 78 12968 100 3. 90 1.8 12969 0 4.0 1.2 12970 0 3. 95 0.23 12970 0 3.60 1.5 12971 0 4.0 0. 27 12972 0 3.95 2. 8 12973 0 4.0 0. 35 12974 0 4.0 0. 98 12975 0 3. 7 0.43 12976 0 3. 90 0.5 12977 0 3. 95 1.4 12978 0 3.90 0.5 12979 0 3. 95 0.45 12980 0 3.90 0. 7 12981 0 3. 95 0. 23 12982 0 3.90 0. 87 12983 0 3.90 0. 82 12984 0 4.00 0. 50 12985 0 4.00 0.4 12986 0 4.00 0.5 12987 0 4. 00 0.4 13005 0 3. 95 0. 6 13006 0 3. 30 0. 7 13007 0 3. 95 0. 7 13008 0 3. 90 1.0 13010 0 3. 95 0.2 13011 0 3. 90 0. 5 13012 0 3.90 1.2 13013 0 3. 95 2. 2 13014 0 3. 90 6. 1 13015 0 3. 90 2. 8 13016 0 2. 00 0. 8 13017 0 3. 90 0. 6 13018 0 3.95 0.5 13019 0 3. 95 0. 1 13020 0 3. 95 0. 1 13021 0 3.60 0.4 13022 0 3. 95 0.2 13023 0 3.95 0. 1 13024 0 3. 90 0. 2 13025 0 3. 95 0. 3 13026 0 3. 90 0. 6 13027 0 3.90 0. 7 13028 0 3.90 0.7 13029 0 3.90 0.6 13031 0 3. 90 1.2 Ash % Filter 0.45 3^9 MAY 1969 (continued) S ta tio n D ep th (m ) S a m p le V o l( l) W t/l(m g ) 13032 0 3. 95 1.3 JULY 1969 13149 0 4. 00 0.42 13149 2. 60 2.6 13149 3. 95 2.3 13150 0 3. 95 0. 3 13150 4.00 0.25 13150 4. 00 0.6 13151 0 3.60 0.25 13151 3. 95 3.2 13151 3. 90 0.64 13152 0 4. 00 0. 50 13152 4. 00 2.2 13152 3. 90 1.4 13153 0 4. 00 0. 1 13153 255 3. 90 0. 1 13153 245 4.00 0. 05 13154 78 3. 95 0. 25 13154 83 3. 90 0. 31 13155 0 3.90 0. 3 13155 4. 00 1.50 13155 3. 95 0.25 13156 0 3. 95 0. 1 13156 460 3. 90 0.25 13156 470 3. 10 0.5 13157 0 3. 95 0.4 13157 430 3. 90 1.0 13157 420 3.65 0. 93 13158 0 3.95 0.2 13158 338 3. 10 5.2 13158 333 3. 10 1.2 13159 0 4. 00 0. 5 13159 205 2. 30 0. 6 13159 215 3. 60 0. 96 13160 0 4.00 0. 8 13160 33 3. 70 3. 0 13160 28 3.50 0.4 13160 23 3.50 1.3 13161 0 4. 00 0.5 13161 54 3. 65 0. 7 13161 49 3. 90 0. 7 13161 44 3. 85 0.9 13162 0 4. 00 0. 1 13162 80 3.50 1.2 Ash % Filter 0.45 Statio 13162 13162 13163 13163 13163 13163 13164 13164 13164 13164 13165 13165 13165 13165 13166 13166 13166 13166 13167 13167 13167 13167 13168 13168 13168 13169 13169 13169 13169 13170 13170 13170 13170 13171 13171 13171 13171 13171 13172 13172 13172 13172 13173 13173 13174 13174 13175 3 5 0 JULY 1969 (continued) D epth(m ) S a m p le V o l( l) W t/l(m g ) A s h % F ilt e r 75 3.90 1.1 0.45 70 4.00 0.2 " 0 3.90 0.3 " 425 3.85 0.8 1 1 430 2.60 0.5 " 436 3.90 0.8 0 4 .0 0.4 " 545 2.0 0.3 1 1 530 3.80 0.3 " 525 3.95 0.9 " 0 3.90 0.15 " 580 Contaminated Sample 565 3.70 0.3 " 560 2.50 0.5 1 1 0 3.90 0.2 " 197 3.91 0.46 " 192 3.70 0.3 " 187 3.20 0.45 " 0 3.95 0.25 " 192 3.70 2.2 " 187 3.70 2.1 " 182 2.80 2.2 " 0 3.90 0.18 " 77 3.90 1.4 " 72 3.92 0.3 " 0 3.90 0.26 " 59 3.90 1.4 " 54 3.95 1.4 " 49 3.85 0.6 " 0 3.95 0.27 " 48 3.50 5 .4 " 43 3.94 4.1 " 38 3.90 3.1 " 0 3.94 0.3 " 35 2.00 19.4 30 3.60 4 .9 " 25 3.90 0.66 " 20 3.20 0.6 1 1 0 3.92 0.2 " 48 3.25 10.1 " 38 2.90 0.3 " 33 3.91 0.2 " 0 3.60 0.4 62 3.82 7.4 " 0 3.94 0.38 " 92 3.50 2.7 " 0 3.94 0.3 " JULY 1969 (continued) S tation D ep th (m ) S a m p le V o l( l) W t /l( m g ) A s h % F ilt e r 13175 150 3. 95 1.5 13176 0 3. 90 0. 5 13176 220 3. 80 4. 1 13177 0 3. 95 0. 25 13177 112 3. 90 0. 64 13178 0 3. 82 0. 1 13178 59 3. 60 0. 3 13179 0 3. 95 0.25 13179 220 3. 80 0.5 13180 0 3. 91 0. 33 13180 115 3.90 0. 6 13181 50 3.70 4. 3 13182 0 4. 00 0. 1 13*182 30 3.70 14. 6 13183 0 3. 97 0.2 13183 25 3. 93 15.4 13183 20 3. 95 1.5 13184 0 3. 90 0. 8 13184 20 3. 90 19. 1 13184 15 3. 95 0. 3 13193 0 3. 92 0. 3 13194 0 3. 95 0. 3 13194 95 3. 95 0. 6 13195 0 3. 94 0.4 13195 190 3. 75 0.45 13196 0 3. 94 0. 33 13196 170 3. 96 0. 9 13197 0 3. 90 0. 3 13197 345 3. 80 0.3 13198 0 3. 93 0.2 13198 150 3. 75 4. 9 AUGUST 1969 13320 0 3.90 0.2 63 13320 95 2. 50 0.4 80 13321 0 3. 85 0. 3 13321 285 C ontaminate d 13322 0 3.90 0. 13 80 13322 245 3.45 0. 8 13323 0 4.0 0. 3 36 13323 240 3. 0 0.27 - - 13324 0 3. 90 0.28 45 13326 0 3.90 0. 33 77 13326 34 2. 50 0.43 73 13327 0 3. 92 0. 35 71 0.45 352 AUGUST 1969 (continued) S ta tio n D ep th (m ) S a m p le V o l( l) W t/l(m g ) A s h % F ilt e r 13327 62 3.70 13328 0 3.90 13329 0 3.80 13330 0 3.90 13331 0 3.90 13331 560 3.80 13332 0 3.92 13333 0 3.94 13333 47 2.65 13334 0 3.90 13334 71 3.74 13335 0 3.40 13335 318 3.90 13336 0 4.0 13336 412 3.93 13337 0 3.95 13338 0 3.80 13339 0 3.97 13339 80 3.10 13340 0 3.92 13340 35 2.80 13341 0 3.87 13341 62 3.75 13342 0 3.82 13342 89 3.90 13343 0 3.95 13343 400 3.90 13344 0 3.93 13344 387 3.90 13345 0 3.95 13345 400 3.90 13346 0 3.95 13346 154 4.00 13347 0 4.00 13347 44 3.85 13348 0 3.93 13348 63 3.85 13349 0 3.95 13349 55 3.93 13350 0 3.90 13350 22 3.85 13351 0 3.95 13351 13 3.80 13352 0 3.90 13352 44 3.90 13353 0 3.90 13353 95 3.80 0.91 76 0.45 0.54 71 » 0.31 83 " 0.25 40 " 0.51 50 " 0.16 70 " 0.25 61 " 0.5 74 " 2.6 87 " 0.23 -- " 1.5 -- " 0.7 -- " 0.84 91 " 0.7 -- " 0.83 -- " 0.36 -- " 0.4 -- " 0.45 50 " 0.6 67 » 0.3 46 0.67 42 " 0.5 50 " 0.72 -- " 0.6 52 " 0.53 68 " 0.35 95 1.0 78 " 0.2 - - " 1.1 88 " 0.5 50 " 0.8 - - " 0.4 67 " 0.7 75 " 0.45 68 " 4 .9 89 0.27 73 " 3.8 1.5 61 " 2.4 0.76 73 " 3.2 79 " 0.75 77 " 3.6 85 " 0 .4 63 " 1.25 0.53 67 " 3.2 85 " 353 AUGUST 1969 (continued) Station Depth(m) Sample Vol(l) Wt/l(mg) Ash % 13354 0 3. 90 0.6 54 13354 175 3. 90 0.5 90 13355 0 3. 93 0. 3 73 13355 220 3. 80 2.9 85 13356 0 3. 90 0. 3 13357 0 3. 90 0.51 51 13357 260 3. 95 1.4 13358 0 3.00 0.66 40 13358 90 3. 95 0.6 78 13359 0 3. 95 0. 35 50 13359 80 3. 50 0. 31 13360 0 3. 90 0.51 40 13360 205 3. 70 0. 5 -- 13361 239 3. 75 0.45 -- 13362 198 3. 90 4. 3 86 13363 0 3. 90 0.92 89 13363 56 3. 90 16. 8 -- 13364 0 3. 90 0.92 72 13364 30 3. 10 7.9 90 13365 0 3. 95 0. 8 71 13365 25 3. 90 13.7 13366 0 3. 90 0.43 47 13366 34 3. 90 3. 5 13367 0 3. 90 0.43 42 13367 60 3. 90 2. 5 89 13368 0 3. 95 0.6 91 13369 0 3. 94 • 0.27 •» -« <55 13369 180 3. 90 0.41 -- 13370 0 3. 90 0.23 89 13370 30 3.50 1.7 13371 0 3. 90 0. 33 92 13371 20 3. 70 25.6 92 13374 0 3. 93 0. 33 38 13374 i9 3. 90 4. 5 90 13375 0 3. 95 0.4 50 13375 43 3. 90 1.0 85 NOVEMBER 1969 13536 77 3. 90 0.2 13537 275 3.93 0.25 13538 460 3. 90 0.4 13539 450 3. 92 0. 6 13540 116 3. 90 0.2 13541 329 3. 94 0.2 13542 105 3. 90 0.4 Filte r 0.45 NOVEM BER 1969 (continued) Station Depth(m) Sample Vol(l) Wt/l(m; 13543 57 3. 93 0.2 13544 225 3. 95 0. 2 13545 335 3. 92 0. 13 13546 300 C ontaminate d 13547 305 3. 92 13. 8 13548 75 3. 90 0. 5 13549 280 3.93 0.4 13550 410 3. 90 0. 54 13551 50 3. 93 0. 87 13552 67 4. 00 0. 3 13553 155 3. 91 14. 3 13554 600 3. 92 0.5 13555 620 3. 90 0. 3 13556 520 3. 89 0. 15 13557 80 Contaminated 13558 400 3. 94 0.4 13559 300 3. 91 0. 7 13560 86 3. 90 -- 13561 68 3. 90 0.4 13562 47 3. 92 1.2 13563 57 3. 96 1.9 13564 75 3.92 1.0 13565 80 3.91 0.5 13566 190 3. 92 0.4 13567 190 3.94 0. 35 13568 97 3. 91 2. 8 13569 44 3. 90 0. 5 13570 24 3.93 0.4 13571 60 4. 00 2.2 13572 70 3. 92 0.5 13573 75 3.89 0.9 13574 85 C ontaminate d 13575 22 3. 80 0. 8 13576 30 3. 93 3. 7 13577 36 3. 92 3.7 13578 45 3. 91 3. 6 13579 119 C ontaminate d 13580 234 3.90 0. 16 13581 200 3.90 0.2 13582 32 3. 92 3. 7 13583 20 3.93 0.9 13584 No Sample 13585 20 3. 94 0. 1 13586 18 3. 95 0. 7 13587 14 3.90 2.4 13588 23 3.93 0. 16 13589 34 3.91 0.5 Filter 0.45 355 N OVEM BER 1969 (continued) Station Depth(m ) Sam ple V o l(l) W t/l(m g) A sh % F ilte r 13590 20 3. 96 1.4 13591 60 C ontaminate d 13592 225 3. 90 0. 16 DECEMBER 1969 13648 0 3. 95 0.4 13648 100 3. 90 1.46 13649 0 3. 90 0.5 13649 280 3. 97 0. 6 13650 440 3.72 0. 3 13650 0 3. 90 0. 3 13651 0 3.70 0. 3 13651 115 4. 00 0. 6 13652 0 3. 78 0. 3 13652 330 3. 92 0.9 13653 0 3. 92 0. 2 13653 480 3. 70 1.0 13654 0 3. 90 0. 3 13655 0 4.00 13655 490 3. 94 1.4 13656 0 3. 80 0.4 13656 62 3. 84 0.4 13657 0 3. 90 0.2 13658 0 3.82 0.2 13658 580 3. 90 0.2 13659 240 3. 90 0. 1 13660 0 3. 90 0. 12 13660 117 3. 72 0. 31 13662 0 3. 80 0. 2 13662 95 3. 88 0.43 13663 0 3. 80 0. 3 13663 590 3.75 0.52 13664 0 4. 00 0. 35 13664 Contaminated 13665 0 3. 89 0.4 13665 55 3. 94 0. 74 13667 0 3.50 0.5 13667 80 3. 92 0.98 \ 13668 0 3. 85 1.0 \ 13668 145 3. 90 0.23 \ 13669 0 3. 90 0.2 \ 13669 Contaminated \ 13670 0 3.70 0. 13 \ 13670 310 3.75 0.4 \13671 315 3.00 0. 64 0.45 356 DECEM BER 1969 (continued) Station Depth(m) Sample Vol(l) Wt/l(mg) 13672 C ontaminate d 13673 0 4. 00 0. 8 13673 30 3. 90 2.5 13674 0 3. 90 0. 8 13674 55 3. 90 1.61 13675 0 3. 64 1.5 13675 25 3. 90 0.5.4 13676 0 3. 90 0.2 13676 92 3. 70 0. 32 13677 0 3. 65 0.2 13678 0 3. 82 0.21 13678 245 3. 92 1.24 13679 0 3.92 0.6 13679 140 4. 00 0. 72 13680 0 3. 75 0.08 13681 0 3. 90 0. 19 31682 0 3. 91 0. 11 31683 0 3. 89 0. 78 13684 0 3. 87 0.27 13685 0 3. 81 0.32 13686 0 3.82 0.39 13686 95 3. 95 1.7 13687 0 3. 75 0. 18 13687 69 3. 60 4. 7 13688 0 4. 00 0. 57 13688 28 3.65 0. 79 13689 0 3. 91 0. 37 13689 26 3. 90 1.1 13690 0 3.90 0.61 13690 26 3. 92 9. 35 13691 0 3. 85 0. 22 13691 52 3. 90 2.68 13692 245 3. 85 0.29 13693 0 3.92 0. 11 13693 95 3. 85 0. 1 13694 0 3.72 0.08 13694 310 4.00 0.22 13695 160 3. 93 0.47 FEBRUARY 1970 13854 400 3.92 0.15 13856 580 3.92 0.38 13858 585 3.87 0.16 13859 120 3.90 0.06 13860 428 4.00 0.43 Filter 0.45 357 FEBRUARY 1970 (continued) Station Depth(m ) S am ple V o l(l) W t/l(m g) A sh % F ilte r 13861 428 4.00 0. 32 94 13862 400 3.92 0. 81 99 13863 478 3.92 0. 38 - - 13864 441 3.91 4. 32 89 13865 110 3. 90 0. 15 13866 86 3.89 0. 1 99 13867 470 3.97 0. 15 99 13868 480 3.90 0.07 90 13869 395 4. 00 0. 1 99 13870 290 3.93 0.08 99 13871 170 3. 94 0.06 98 13872 340 3. 90 0.44 94 13873 410 3. 97 0. 15 99 13873 0 4. 00 0. 22 50 13874 0 3. 94 0. 16 - - 13874 525 3.91 0. 15 13875 0 3. 93 0. 07 - - 13875 480 3. 92 0. 10 13876 0 3. 94 0.05 - - 13876 90 3. 88 0. 23 - - 13877 75 3. 93 0. 14 - - 13879 482 3.75 0. 13 13880 530 3.90 0.05 13882 504 3. 68 0. 07 13884 0 3.90 0. 11 65 13886 445 3. 91 0. 26 82 13889 574 3. 90 0. 18 - - 13890 548 3. 96 0. 12 -- 13891 500 3. 98 0.43 94 13892 320 3.92 1.91 95 13894 180 3. 90 0. 10 99 13895 350 3. 90 0.49 96 13901 137 3. 94 0.09 90 13903 520 3. 87 0. 33 13905 460 3. 92 2. 30 93 13906 175 3. 86 6. 37 95 13907 35 3. 91 0.27 75 13907 0 3. 91 0.60 - - 13908 212 3. 92 0.20 99 13909 172 3. 90 0. 22 95 13910 24 3.90 6. 71 95 13911 16 4. 00 1.53 85 13912 57 3. 93 4. 10 - - 13913 24 3. 94 0. 16 -- 13913 0 3. 92 0. 80 13914 0 3. 93 0. 77 13914 102 3. 97 1. 75 85 0. 45 358 FEBRUARY 1970 (continued) Station Depth(m) Sample Vol(l) Wt/l(mg) Ash % 13915 200 3. 90 1.40 89 13915 0 3. 94 0.59 13917 24 3. 90 0.53 13919 27 3. 94 3. 12 90 13919 0 3. 92 0.77 83 13920 -- --- 13920 26 3. 92 9.33 95 13921 0 3. 94 0. 35 99 13921 41 3. 93 2.0 96 13922 0 3.93 0.27 63 13922 52 3. 92 2. 32 96 13923 0 3. 92 0.43 78 13924 97 3. 90 0. 15 99 13925 122 3. 95 0.51 90 13926 63 3.94 0. 78 90 13927 45 3. 90 0.29 94 13928 28 3. 97 1. 84 90 Filter 0.45
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Asset Metadata
Creator
Drake, David Edward
(author)
Core Title
Distribution And Transport Of Suspended Matter, Santa Barbara Channel, California
Degree
Doctor of Philosophy
Degree Program
Geological Sciences
Publisher
University of Southern California
(original),
University of Southern California. Libraries
(digital)
Tag
OAI-PMH Harvest,physical oceanography
Language
English
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Gorsline, Donn S. (
committee chair
), Bakus, Gerald J. (
committee member
), Stone, Richard O. (
committee member
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The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...
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physical oceanography