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Physicochemical characterization of sediment facies and paleoclimatic inferences, California Continental Borderland

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Physicochemical characterization of sediment facies and paleoclimatic inferences, California Continental Borderland

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Content PHYSICOCHEMICAL CHARACTERIZATION OF SEDIMENT FACIES AND PALEOCLIMATIC INFERENCES, CALIFORNIA CONTINENTAL BORDERLAND t>y Michael Eugene Mulhern A Thesis Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE (Geological Sciences) August 1976 UMI Number: EP58633 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Dissertation Pub! shnq UMI EP58633 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProOuest ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 U N IV E R S IT Y O F S O U T H E R N C A L IF O R N IA THE GRADUATE SCHOOL UNIVERSITY PARK LOS ANGELES. CALIFORNIA 90007 O. e ’ 77 M °>5fe This thesisj written by Mi c-hael - - Eugenes. .Mulhera....... under the direction of h.%&..Thesis Committee, and approved by all its members, has been pre sented to and accepted by the Dean of The Graduate School, in partial fulfillment of the requirements for the degree of M as te r. . of. .Sc i e nc e_. . £Gr e o 1 o gi c al. . Sc. i e n c e s ) Dean Date. Chairman CONTENTS PAGE INTRODUCTION Background of the investigation ............... 1 Previous work........................... 3 Purpose and scope .............................. 5 Review of Late Pleistocene and Holocene paleoclimatology ................. 7 Acknowledgments................................ 10 PHYSIOGRAPHY AND GEOLOGY OF THE CONTINENTAL BORDERLAND BASINS General bathymetry and structural geology . . . 12 General oceanography Currents and basin waters ................. 19 Biologic oceanography ................. 21 Sediments of the basins Sediment source ............................ 2k Transport mechanisms ....................... 26 Lithology.................................. 30 Age dating..................>............... 31 Sedimentology of the measured biogeochemical parameters ............... 33 ii PAGE Santa Barbara Basin Structural geology and sediments ...... 39 Oceanography ..... ..................... ^2 Yelero Basin Structural geology and sediments .......... W Oceanography ................................ ^ EXPERIMENTAL METHODS AND RESULTS Sample collection and preparation ............ A 5 Core description and radiography ............. ^8 Size analysis Methods ...... ....................... 58 Results..................... 59 Micropaleontologic analysis and dating .... 6l Organic nitrogen Methods.................................... 66 Results.................................... 67 Total and organic.carbon Methods ............................ 69 Results.................................... 70 Carbonate Methods.................................... 72 Results ..... ......................... 72 Clay mineralogy Methods.............. 7^ iii PAGE Results............................. 82 DISCUSSION Paleoclimatic correlations ................... 86 Sediment source and diagenesis ............... 94 Facies characterization ....................... 98 CONCLUSIONS...................................... 102 REFERENCES . 10 6 APPENDICES..................................... . . 113 I. Core and radiograph description........... 114 II. Size analysis ................... 119 III.Biogeochemical parameters ................. 123 IV. X-ray clay mineral analysis............... 130 iv ILLUSTRATIONS FIGURE PAGE 1. Core location and generalized bathymetry . . 1^ 2. Experimental data for AHF 11270 ^9 3. Experimental data for AHF 1 6 1 3 7 ........... 51 4. Experimental data for AHF 176^0 53 5. Experimental data for AHF 16830 55 6. Schematic X-ray diffraction pattern .... 77 7. Experimental data for Tanner Basin......... 89 TABLE 1. Core location and water depth ....... ^7 2. Micropaleontologic summary for Santa Barbara Basin ..... ................. 63 v ABSTRACT Determination of many physical and chemical para meters with depth (or time) in selected sediment facies is necessary to accurately determine the sedimentologic and diagenetic history of the California Continental Border land marine basins. Correlation of these parameters between basins of good control and deep sea sediment re cords allows large-scale climatic and oceanographic con ditions of the late Pleistocene and Holocene to be inferred. The largest variations with depth trace the last Wisconsin glacial cycle. Carbonate and coarse fraction records from Velero and Tanner Basins show the expected minima from detrital dilution at the height of glacial advance (about 17*000 yrs BP) and maxima during warmest times (7500 yrs BP). Organic content reaches a maximum prior to the 12,000 yrs BP acceleration in warming in "offshore" or more seaward Velero Basin, but the reverse holds in "intermediate" Tanner Basin. This suggests seaward shifting of sedimentation rates, bringing Velero Basin into the "intermediate" maximum organic sedimenta- vi tion basin category during this cool period; the then optimal burial rate preserved organic matter. Contempora neously, Tanner Basin became a "nearshore" basin with di lution of its organics by the terrigenous influx. Both organic content and carbonate increase as the 12,000 yr BP datum is approached, but the organic content then de creases to a relative minimum, apparently due to less detrital protection as warming and submergence reduced terrigenous input to Velero Basin. Thus, as the earth’s climatic zones shifted toward the equator and compressed during glacial periods, sedi mentologic zones paralleling the southern California coast were shifted seaward. Carbonate content records paleo- climates but organic content and sand fraction mirror-.'' topographically controlled sedimentation, closely related to but perhaps lagging behind sea level change. Cores from Santa Barbara Basin display the general cooling trend since 7500 yrs BP, and suggest increased coastal runoff compared to present rates. The generally lower carbonate values reflect increased dilution by terrigenous material in this "nearshore" basin. Less pronounced variations deeper in the cores are caused by diagenesis and facies change. In Velero Basin the rapid initial decrease of organics and higher C/N ratio with depth reflects the ready oxidation of organics and preferential loss of proteinaceous over carbonaceous vii substances in the longer burial times. Lower variation and one observed slight increase with depth of organics in reducing Santa Barbara Basin are due to less complete deamination. The high C/N there is probably due to con tamination by the ubiquitous local oil seeps, which hamper diagenetic study. Flood layers in Santa Barbara Basin most closely resemble local river mineralogy and contain the least organic content. In hemipelagic zones, homogeneous layers possess larger grain size and smaller nitrogen, carbon, C/N and carbonate content, as a result of passage of sedi ment through the digestive tracts of benthos. The vari ations exceed analytical precision limits, but are dwarfed by climatic, source, and diagenetic changes. X-ray diffraction analysis reveals no significant changes in clay mineralogy either with depth or facies in Santa Barbara Basin for the last 8000 years. Diagenetic changes or recrystallization in clays are not observed. The uniform vertical and horizontal distribution reflects the constant provenance of Santa Clara River suspended sediment with a secondary and variable contribution from iron-rich metamorphic rock suites from the north via the California Current. Weathering under the influence of a semi-arid climate in local igneous and sedimentary source terrain is indicated. viii INTRODUCTION Background of the Investigation One of the fundamental objectives of geologic research is the identification of ancient sedimentary environments. A knowledge of the precise physicochemical parameters of deposition is invaluable for natural re sources exploration, especially for paleoecologic and stratigraphic reconstruction. This information is nec essary, for example, to evaluate the possibilities of organic accumulation, types of diagenetic change, migra tion, and entrapment of fluid hydrocarbons in marine rocks. Environmental interpretation, as of core-hole samples, re quires additional study as to the identity and validity of the measured characteristics or "signatures" each environ ment leaves on the record. Thus, a knowledge of the topo graphic framework, lateral and vertical facies relation ships, and change with time of the biochemical parameters is important for exploration, and, of course, fundamental to all research-oriented stratigraphic correlation, historical reconstruction, and structural mapping. The most useful data regarding ancient environments 1 are obtained from observation of modern counterparts. Oil from structures in depocenters such as the Late Tertiary Los Angeles and Ventura Basins, originated from deposition in basins similar to those of the Continental Borderland off southern and Baja California (Emery, i960), which pro vide a unique opportunity to study present basin sedimenta tion. The Borderland basins exhibit a spectrum of sedi mentation rates, organic matter and mineralogic content, and physicochemical environments from those typical of the deep sea to nearshore anoxic basins. That the stratigraph ic and structural patterns of the presently-subaerial basins can be correlated with Tertiary events is shown by Emery (i960). He noted that owing to rapid filling of nearshore basins by sediments, sampling seaward across the basins is equivalent to studying a single basin at pro gressively earlier periods in its history. The outer sea ward basins receive the least terrigenous contribution at present and are analogous to incipient basin filling stages, whereas the inner basins, some of which are nearly filled because of the high detrital input, are equivalent to later stages of Tertiary basin filling. Assuming simi lar sedimentary processes in the past few million years in the Borderland, this study is an attempt to reaffirm that measurement of a parameter with depth in a core is equiva lent to studying its alteration with time. 2 Previous Work Past workers have assembled a broad data base of sediment size distributions, rates, content and aspects of diagenesis of organic matter and its components. A brief summary of general results, to be detailed later accord ing to topic, provides a useful background for this investigation. Sverdrup e j f c al. (19^1) delineated general circula tion patterns in the Pacific Ocean and summarized known chemistry and biology of the oceans. Temperatures, salin ity, oxygen content, and circulation for 2 years in the Santa Barbara Channel have been observed by Kolpack (1971). Diagenetic processes have been discussed by Trask (1932) and Degens (1967)• Emery and Rittenberg (1952) and Rittenberg, Emery and Orr (1955) studied diagenesis and nutrient regeneration. The latter study showed that deep water inflow replaces basin water at least every 2 years. They also noted pyrite forming in oxidizing sediments, suggesting reducing conditions in microenvironments, as in decaying tests. Compaction from weight of overburden for cing interstitial water upward, provides a means for solution and deposition of various elements. Emery and Rittenberg (1952) also noted decreasing organic matter and redox potentials and increasing pyrite with depth. The important role of bacteria in diagenesis was reaffirmed, 3 and it is noted that character of basin water, which in fluences diagenesis, depends upon basin sill and floor depth. Also observed was that pH is maximum and that sul fate decreases with depth in the upper portion of the core, owing to bacterial action. Emery (i960) summarized regional oceanography, geo logic setting, sedimentation, diagenesis, and biology of the Continental Borderland. Using sulfur isotope data, Kaplan (1962) confirmed biologic reduction of sulfate trapped interstitially in solution as the single most significant process in the sul fur cycle. The released sulfide forms hydrotroilite and then pyrite. A major terrestrial source of pyrite was ruled out by calculations of erosion and transport for the region. Silt-sized pyrite is the most abundant form of sulfur in both reducing and oxidizing conditions, although free and organic sulfur forms are continually forming and reacting. The source of iron is believed to be by bacte rial removal from the clays. Zobell (19^6) and Juge (197^) also developed patterns of bacterial activity. Investigating pore water chemistry, Booth (197^) concluded that the high variability indicates that the Borderland sediments have not attained chemical equilib rium. This is attributed to grain size (or surface area), membrane effects, contamination by connate water, and organic complexing. He observed no crystalline clays forming or being altered. + 2 Murray (1973) noted a decrease with depth of Ca in Santa Barbara Basin sediments, which in reducing water may be complexed to organic matter (Berner, 1971). This may be later precipitated as CaCO^ (Sholkovitz, 1972). Murray (1973) also agreed that diagenesis occurs rapidly (in the first 150 m) and that iron is not being replaced + 2 by Mg from collapsed clay structures. He concluded that in anoxic conditions iron oxide coatings on clays dissolve and increase available exchange sites on clay. Iron is re duced to sulfides and magnesium is removed from solution. Purpose and Scope This study was undertaken to increase the under standing of Holocene sedimentation history and correlation with Pleistocene events in the Borderland basins. More subtle patterns of sedimentation and diagenesis are needed to better fingerprint ancient environments. Building upon published and unpublished data of workers from the Sedi- mentology Research Laboratory at the University of Southern California, additional geochemical parameters were measured on selected cores at more closely spaced intervals and in carefully chosen facies. Santa Barbara Basin was selected as the model basin for the study because of the relatively 5 large amount of available samples and data (Hulsemann and Emery, 1961, Murray, 1973» Fleischer, 1972, and Drake, 197l)i a well-identified terrigenous source, and because it is the only Borderland basin and one of the few depo- centers in the world today that is anoxic. The oxygen- depleted bottom water does not favor burrowing benthonic organisms, so laminae or varves of organic-rich sediment are preserved. The other Borderland basins, as well as many laminated black shales of the geologic column, have in their histories experienced times of reducing conditions, depending upon interrelated patterns of water circulation, sea level change, and rate of organic and detrital sedimentation. Key experimental parameters were selected to elucidate the sedimentologic history of Santa Barbara Basin and to identify intervals of reducing conditions. The effects of diagenesis and bioturbation upon the sedi mentary "signature" and their importance with time or depth were observed. These tests were then applied to identify times of reduction (as well as paleoclimatic events) in other basins, even though original laminae may have been subse quently destroyed by burrowing organisms. It would be use ful to examine sediments in basins of different distance to shore at, above, and below zones of laminations as revealed by radiographs. Velero and Tanner Basins were chosen to 6 represent offshore and intermediate basins, respectively, and have proved to be good indicators of glacial cycles (Mulhern, 197^ > Gorsline et al., 1968, Gorsline and Prensky, 1975)• Review of Late Pleistocene and Holocene Paleoclimatology As measurement of the above parameters provides useful paleoclimatic information, further interpretations of the data may be made based upon recent work delineating climatic and resulting sedimentologic and oceanographic events. The purpose of the CLIMAP Program (Hays and Moore, 1973)» using microfossil, isotope, and mineralogic data, was to establish past (700,000 years) and future patterns. Although continental moraines, soil horizons, and faunal extinctions may be dated radiometrically, the con- tinous sedimentation and multiplicity of responding factors of the sea portray a more accurate record of climate change. Emiliani (1955) established a detailed curve of climate versus time using oxygen isotope data, and noted good correlation with known continental glaciation. Though later revised somewhat, the curves show the saw toothed character of major climate cycles, with gradual buildup of ice and abrupt deglaciations (lasting one-tenth of the cycle). Sancetta et al. (1973) date the following 7 events in a North Atlantic deep sea cores an abrupt inter glacial at 127,000 yrs BP with a temperature maximum at 124.000 yrs BP; a cooling at 109,000 yrs BP, correlated with CWurm glacial stage of Europe; a faster cooling at 73.000 yrs BP, beginning the last full Atlantic glacial regime; within this glacial period short warm events at 59.000 yrs BP, 48,000 yrs BP, and 31»000 yrs BP; the rapid termination or warming at 11,000 yrs BP; and the 6000 yrs BP hypsithermal and hypsisaline. Gorsline el: al. (1968) measured the local temperature maximum at about 7000 to 7500 yrs BP with later highs at 5000 yrs BP and 3000 yrs BP. The last peak in cold temperatures (10°C less than present) was about 20,000 yrs BP according to Sachs (1973)* World sea level curves based on magnetic and isotope stra tigraphy, are presented in Shackleton and Opdyke (1973)* The causes of the late Cenozoic glacial periods have been the subject of many theories , but the effects are better observed. Emiliani and Flint (1963) postulated albedo changes, perhaps associated with periods of oro geny, further enhanced by ice cover, which lowered world temperatures. Broecker and van Donk (1970) hold responsi ble changes in orbital parameters. Changes in the tilt of the earth's axis, with a period of about 41,000 years, pro duce glacial maxima in times of reduced contrast between seasonal insolation. Changes in the earth's precession 8 with a cycle of 21,000 years modulates the foregoing for a combined frequency of 90,000 years. The observed gla cial cycles approximate this figure. Sea level was about 125 m lower during the height of glaciality 18,000 to 20,000 years ago and perhaps sev eral meters above the present during the hypsithermal. Glacial effects included increased stream gradients, larg er areas of exposed shelves, banks and islands, decreased land vegetative cover (indicating arid to semi-arid con ditions) , more frequent and intense storms (recorded by the growth of large alluvial fans), and more rigorous oceanic circulation and upwelling due to increased thermal gradients from compression of climatic belts toward the equator. This resulted in faster sedimentation of all types, though proportions of each component varied with distance from source and topography. Arrhenius (1952) noted carbonate percentage peaks in deep sea cores during these times because of increased productivity. Emiliani and Flint (1963) measured increased clay sedimentation in the Atlantic; most glacial water drained into the Atlantic and the currents could then carry more suspended material. Gorsline and Prensky (1975) noted that during the last glacial period carbonate sedimentation doubled, but was overshadowed by a much larger increase in terrigenous in put. Present rates were attained about 7500 yrs BP. The 9 organic input curve has a smooth sine-wave cycle, while detrital input has a more peaked, cnoidal curve, though both are roughly in phase. Ruddiman and McIntyre (1973) confirmed the time- transgressive nature of both locality and faunal, isotope, and lithologic parameters during glacial retreats. They noted a northwesterly retreat in the North Atlantic; the dates are 6500 and 13»500 yrs BP for Greenland and Britain, respectively. Low latitudes displayed less dramatic response, to climate change. Indeed, Broecker et al. (1958) advanced the idea of increased insolation and evaporation in the Equatorial Pacific which increased precipitation at high latitudes, resulting in growth of ice sheets. Luz (1973) believes carbonate dissolution during transition to glacial times is produced by vertical ocean thermal structure rather than by surface temperature effects. The thermocline is inferred to shift upward and the central water mass was areally decreased during glacial periods, associated with intensified circulation. Acknowledgments For definition of the original idea, valuable ad vice on techniques employed, and criticism of the manu script, Dr. Donn S. Gorsline is gratefully acknowledged. Drs. R. 0. Stone and R. H. Merriam read the manuscript and 10 offered useful advice. Dr. B. W. Pipkin is thanked for his generous assistance with X-ray diffraction methods. Dr. I. R. Kaplan and Mr. T. O’Neil provided helpful com ments on geochemistry. Technical assistance on certain cores was provided by T. Demere and A. Price (paleontologic data), G. Pao and S. Limerick (total carbon data), and M. Palmer (typing the final manuscript). The efforts of the field crews of the R. V. Velero IV and the support and use of the facilities and samples of the Department of Geolo gical Sciences and Allan Hancock Foundation, University of Southern California are greatly appreciated. 11 PHYSIOGRAPHY AND GEOLOGY OF THE CONTINENTAL BORDERLAND BASINS General Bathymetry and Structural Geology A unique submarine province off southern and Baja California has been described by Shepard and Emery (19^1) as the "Continental Borderland.’!1 The roughly parallel series of elongate basins and ridges, banks, and islands trend northwest-southeast. This is also the dominant regional fault trend of the San Andreas system. Normal dip-slip4 faults are most abundant, and right lateral strike-slip faults are common, often in combination with the former (Emery, i960). The basin slopes are mostly late Miocene fault scarps or dip slopes of folds (Moore, 1969) and are offset by later east-west faults. Some of the basin slopes, however, are likely of sedimentary origin (Gorsline et al., 1968) and Vedder et al. (197^) note unbroken dipping strata on acoustic profiles where some faults had been inferred by topography. The bank tops, underlain by middle Miocene volcanic and Mesozoic Franciscan-like basement rocks, are largely areas of winnowing (Emery, i960). Low sedimentation rates 12 foster formation of authigenic minerals such as barite, glauconite, phosphorite, and magnanese oxide crusts here and on slopes, though these may be relict.^ The flat- floored basins and troughs preserve a relatively continu ous record of sedimentation, intercepting the terrigenous seaward flux from the continent. The outer boundary, the Patton Escarpment, reaching 4000 m in depth, is also a northwest-oriented fault zone offset periodically by east- west faults, and lacks an apron (Doyle, 1973)- The north ern limit of the Continental Borderland is Point Concep tion (and the Transverse Ranges) and the southern boundary is formed by Sebastian Viscaino Bay. To the southwest lies the abyssal volcanoes of the Baja California Seamount Province. Immediately east are the Peninsular Ranges, relatively young mountains of high relief extending from Los Angeles Basin to the tip of Baja California. The Borderland possesses relatively high topo graphic relief (Fig. 1), with basins reaching J000 m below sea level and island peaks 750 m above sea level. The relief from the top of Santa Cruz Island to the bottom of Santa Cruz Basin is 2713 m (Vedder et al., 197*0 • Santa ^Pasho (1973) believed most Borderland Phosphorites are erosionally-derived from shale beds, as they are often associated with coarse relict sands and gravels and shallow-water pholad burrows and possess oxidized rims and truncated internal structures. 13 Figure 1. Core locations with Allan Hancock Foundation Station numbers (black dots) and generalized bathymetry of the Continental Borderland. The dominant northwest trend of the basins is evi dent. Modified from U. S. Geological Survey Map MF 624 (Vedder et al., 1974) and U. S. Navy Oceanographic Office Chart BC 1206, 1968 (south of 32 N. latitude). 14 120° C:-. Ventura I I2 7 0 » C 16137 17640 ■25° Angeles 10615 10626 0 CORE LOCATIONS AND BATHYMETRY Contour interval 5 0 0 Meters scale 40 km Barbara Basin is bordered by highlands to the north and south. The Santa Rosa-Cortes Ridge is the largest sub merged high, extending southeast from Santa Rosa Island to Cortes Bank. It includes San Nicolas Island (300 m in elevation), Cortes Bank (5 m. below sea level), and is bounded by steep fault scarps (Uchupi, 1961). The flat ridge crest yields Eocene and Miocene gravels of igneous, metamorphic, and clastic detrital rocks (Uchupi, 1961). The Ridge and Tanner Banks are immediately west of Tanner Basin, and during times of glacially-lowered sea level, became a detrital source. Patton Ridge, to the west of Tanner Basin, is sub-parallel to it and Santa Rosa-Cortes Ridge, and extends about 110 km and is as shallow as 218 m (Vedder et al.. 197^0 • The latter workers also reported that whereas large, broad anticlinal structures are indi cated by acoustic profiling of the ridges, the fold pattern is complex, with abundant folds of differing sizes and orientation. Many folds are arranged en echelon. A few basins such as Santa Cruz and San Nicolas Basins are synclinal. Most folds postdate early Miocene and predate late Pleistocene times; the former are often truncated and and the latter beds show little disturbance. Some deforma tion, however, continues today, as indicated by local seismicity and elevated Pleistocene terraces on islands. The outermost basins may be tectonically younger in 16 development. The presence of Late Cretaceous, Paleocene, Eocene, Oligocene, and early Miocene rocks offshore indicates periods of submergence and continental margin deposition during those times. Miocene sediments are the most voluminous offshore and in the Ventura and Los Angeles Basins, indicating broad inundation then. Most recent theories of origin of this block- faulted Basin and Range Topography and volcanism cite vertical and horizontal movement at the downwarped leading edge of the North Pacific Plate. The pre-middle Miocene broad forearc basins and geosynclines were sheared after the initial collision with the North American Plate, about 4 million years ago (Doyle, 1973)* The resulting large northwest-oriented depressions were later fragmented into the checkerboard pattern by east-west faulting, which was often left-lateral and dilational. The latter are best represented by the Santo Tomas Fault (Doyle, 1973) south of the Santa Rosa-Cortes Ridge, the Malibu-Santa Monica Fault on the northern boundary, and the fault system associated with the Channel Islands. Basin subsidence, volcanism, and sedimentation peaked during late Miocene and Pliocene. Shearing and tension, however, continues to the present as the Pacific Plate moves northwest relative to the North American Plate. 17 A great unconformity separates the deformed plutonic and metamorphic basement complex (Triassic to earliest Late Cretaceous) and later sedimentary and volcanic rocks (Moore, 1969). The Patton Escarpment and Ridge may be re bound features of the deep water Franciscan rocks under thrust beneath the Late Cretaceous continent in a fault plane near the base of the continental slope (Moore, 1969). Contemporaneous with the initial lateral motion and shear ing, the Gulf of California opened. This was from spread ing centers of the East Pacific Rise. High heat flow in the entire region, evidenced by basaltic volcanism and granitic intrusions onshore, and relative weakness and resulting ease of deformation of the Borderland crust has been noted by Henyey and Bischoff (1973)* Although basement structure and lithology is not well known in detail, Doyle (1973)» using reflection pro files and dredge hauls, concluded that the whole Borderland is a single geologic province. Earlier workers (as Krause, 1965) divided the Borderland into various units. The deeper and more topographically-rugged southern half was considered a separate unit, but Moore (1969)» with de tailed fathograms, demonstrated that depth is largely a function of sediment filling and noted that the southern portion is farther removed from the important sediment sources. Moore (1969) divided the Borderland into 5 units, 18 however, and "believes the central en echelon folded zone has long "been a tectonically separate unit. The weaker basement rocks there did not resist folding, as did those of the inner zone. Doyle himself recognized 3 generalized subzoness (a) a high-angled block-faulted outer zone with a very thin sediment cover; (b) an anticlinorium of Terti ary sedimentary rocks for a central zone; and (c) a block- faulted inner zone. He also notes periodic gaps in the slope along the length of the Borderland (probably to 27° N. latitude), cited by Doyle as structurally con trolled. The trans-Borderland Santo Tomas Fault, for example, transects one gap which contains appreciable sediment fill. General Oceanography Currents and Basin Waters Emery (i960) described the dominant surface current over the Borderland as a 700-km wide southerly extension of the North Pacific Drift, beginning at ^0 to 50° N. lat itude from the Aleutian Current and termed the California Current. It is thus cool, with low salinity and high dissolved phosphate and oxygen content. As it sluggishly passes Point Conception above the Santa Rosa-Cortes Ridge area, the surface flow to the east takes the form of a counterclockwise eddy. East of this most of the water 19 flows southeastward along the coast. To the south, the California Current becomes less distinct due to mixing of warmer and more saline and nutrient-poor water. Along the coast, upwelling occurs due to easterly winds and topo graphic effects and seaward transport of water occurs due to entrainment of coastal water westward into the Calif ornia Current (Sverdrup et al., 19^2). The Davidson Current, a winter countercurrent, usually flows at depths below 200 m and more easterly. Abundant rainfall and discharge along the Washington coast forms a nearshore zone of low salinity water, which is held near the coast by southwesterly winds. The resultant between gravity pull from this dynamic "high" and the Coriolis Force forms the northward-flowing current. It has been observed that by October, coastal water begins to flow northward at irregular velocities, but by January, the countercurrent is well established, about 100 km wide at 36° N. latitude, flowing at about 0.2 to 0.5 knots. Oxygen is depleted by oxidation of sinking organic matter and respiration of plankton and bacteria. The later biologic control of oxygen causes the ocean's oxygen mini mum zone, the depth of which is critical to water composi tion of the basins. Emery (195^) showed that basin water is similar to overlying water in certain aspects, espe cially temperature and oxygen content. The former differs 20 little downward from sill depth (as most other parameters) and is 1 or 2 degrees centigrade warmer than open-ocean water of equal depth as a result of adiabatic effects. The nutrients silicon, nitrate, phosphate, and oxygen also differ slightly from basin to basin and from values of the open sea at basin sill depth. The fact that subsill wa ters are not stagnant requires a continuous circulation or mixing involving complete replacement in a matter of years (Emery, i960) with overlying waters. Oxygen content thus is controlled by sill depth relative to the oxygen minimum of the ocean. In Santa Barbara Basin, for example, water reaches less than 1 percent saturation for its bottom tem perature of about 6°C because the sill depth is within the oxygen minimum. This condition is also realized in the central Gulf of California, where diatomaceous laminated sediments are undisturbed in the poorly-oxygenated, water (Calvert, - 196^.) Biologic Oceanography The dominant contributors to organic matter pro duction are chlorophyll-containing phytoplankton. The yellow-green algae (Sverdrup et al., 19^2), especially diatoms, live in the sunlit epipelagic and neritic zones. They constitute most of the living biomass; less than one- tenth is converted eventually into animal tissue. The 21 rate of production over the Borderland is among the high est in the world, up to 8 percent of sediments is organic content, rivaled only by stagnant areas such as the Baltic Sea and some fjords. Ancient analogs include the Miocene Monterey Shale. High phytoplankton productivity is due in part to upwelling of nutrient-rich water. Another contri bution to sediment organics are excretions from living cell, local attached algae, and soil leaching and ter restrial organics. In aerobic basins, less than 1 percent of organic infall is buried fast enough for preservation (Zobell, 19^6). The remainder is returned to the photic zone by upwelling and vertical diffusion as inorganic nutrients, most importantly due to bacterial metabolism. Bacteria are present at all levels and rapidly, especially aerobic forms, degrade the unstable products of life, initiating diagenesis. Benthonic organisms aid their effect by churning and aerating the sediment. Bac teria also oxidize ammonia and nitrate, transform sulfur compounds, affect pH and Eh conditions, and may liberate carbon dioxide, methane, water, and ammonia. Zobell (19^6) observed production of hydrogen by certain bacte ria, especially in reducing conditions, from all types of organic compounds, although other bacteria oxidize hydro gen. Additional resulting products are certain organic acids and hydrogen sulfide. He believes methane is 22 produced by bacterial catalyzation of carbon dioxide and other single-carbon atoms with hydrogen. Other bacteria reduce amino acids and other organic acids, and some use inorganic carbon and nitrogen as nitrate and nitrite. Kaplan (1962), using isotope data, emphasized the important role of sulfate-reducing bacteria, particularly Desulfovivrio desulfuricans. At 10°C, he calculated “ "2 I.87 mg x 10~ /cell/hr sulfide forming; the rate is 5 times slower at 0°C. Kaplan (1962) found that free sul fur probably forms from oxidation of H^S, and may be oxi dized or reduced during metabolism. Organic sulfur is on ly a minor source of inorganic sulfides; organic detritus from algae contains about 1.15 percent sulfur, while ani mals contain an average of about O.89 percent (with a range of 0.30 to 3*3 percent). Kaplan (1962) concluded that sulfur is forming at all depths in sediments, probably from sulfide, and reacts with organic matter to form pyrite or intermediate compounds as pyrrhotite. The organics pro vide the sulfur and nutrients for bacterial sulfate reduc tion. Most basins have an abundant benthonic population, as their sills were below the oxygen minimum zone. Their p average biomass is about 10 g/m (Emery, i960) and contain burrowing polychaete worms, ophiuroids, holothurians, brachiopods, sponges, sea urchins, bivalves, gastropods, 23 and chitons. Some have hard parts for preservation, where as others record their activities by burrows or trace fos sils; small mounds of animal origin are common in photo graphs even in deep basins such as Tanner Basin (Emery, I960). Three basins, whose sills are within the oxygen minimum zone, experience further impoverishment of oxygen by the high rates of unoxidized organic matter reaching the bottom. Oxygen is thus depleted in interstitial water in Santa Barbara, Santa Monica, and San Pedro Basins, and hydrogen sulfide is produced by anaerobic sulfate-reducing bacteria in the first basin. Here, the benthonic biomass 2 is 2 g/m , and only a few species of clams, snails, worms, ophiuroids, and sponges are present (Emery, i960). Kaplan (1962) calculated that the anaerobic sulfate reduction is responsible for a 15 percent decrease in organic matter in the basin, as 2 atoms of organic carbon are consumed for every atom of sulfur. Sediments of the Basins Sediment Source The Borderland basins trap virtually all continen tal sediment, but rates, size distributions, and types are a function of many interrelated factors. Dominant sedi ment sources for the Borderland are streams issuing from _______ 2k Cretaceous and Quaternary granitic and sedimentary rocks of the Peninsular Ranges and the diverse rock types of the Transverse Ranges. Maps of drainage area adjacent to the Borderland show only an approximately 60 km-wide strip. Semi-arid climate and high relief produce a relatively immature detrital contribution. The less erodable rocks and smaller discharge adjacent to the southern Borderland results in less sedimentation. Islands, banks, and ridges, during times of lowered sea level, provide local elastics. Eolian dust (e.g. angular quartz silt), sea cliff erosion, chemical precipitates, and suspended California Current- borne sediment make minor contributions (Emery, i960; Fleischer, 1970). Basins separated from sediment source by other non-filled basins receive primarily fine hemi- pelagic-suspended sediments. Suspension is accomplished by storm agitation of the nearshore environment, stream- discharged lenses of fresh water containing terrestrial mud, and subsurface plumes of turbid water. Those basins either adjacent to land or separated by prograded, filled basins receive more prodigous and coarser quantities of bed-load detrital sediments, commonly in the form of turbidites. 25 Transport Mechanisms Several submarine canyons incise the narrow shelf adjacent to land. These, probably initiated or cut in part during times of lowered sea level (Moore, 1969), are important progenitors of turbidity currents (Emery, i960). The southeastward longshore drift (caused by storm swells from the North Pacific) brings sediment to the heads of canyons, from which the sediment slides seaward periodi cally as the masses become unstable. Given time, pro gradation builds a wedge or fan of chiefly distal turbidite sequences, fills basins (as the San Diego Trough), and spills over the lowest sill into the next basin (as Santa Catalina Basin). Such sequences are believed present in onshore Pliocene basinal strata (Emery, i960). Turbidity currents may erode the sill and canyon, lowering base level and entrenching the distributary system. Sediments are usually quartz-feldspathic sand, show some grading, and display basal scour features. Pleistocene periods of glacially-lowered sea level (Gorsline et al., 1968) cor relate with increased turbidite deposition. This resulted from greater exposure of shelf, islands, and banks (as Cortes Bank near Tanner Basin), increased stream gradient, and perhaps more rigorous oceanic circulation. Most sediments, however, reach their resting places 26 by a slower, less dramatic hemipelagic sediment rain. The earlier concept of a blanketing particle-by-particle deposition from current-borne suspended load has been questioned by recent work. Gorsline et al. (1968) pro posed some degree of topographic control of fines, similar to that experienced by turbidity currents. The suspended fines are believed to move slowly and continuously with lateral component of motion in deep currents and along thermoclines. Drake (1971) reported that in Santa Barbara Basin, currents below the sill depth of ^75 m reach 20 cm/sec and continually agitate a population of fine particles. This material is trapped within the Basin and the finer particles are deposited where transport power diminishes in topographic depressions. Coarser particles deposit more uniformly, as they are not as strongly influenced by turbulence. Moore (1969) cited minimal (less than 15 percent) contribution of hemipelagic deposition, emphasizing shelf- originating, low density, low velocity turbidity currents. These, however, may be important only associated with submarine canyons. Drake ejt al. (1972) measured par ticle concentrations as much too low (2 to 4 times) to initiate low density turbidity currents. Rather neph- 27 eloid layers'!- moving along the bottom and detaching along thermoclines moving seaward from the slopes, are observed in his studies of the Santa Barbara Channel. Even times of peak runoff did not produce sufficient quantities of sediments to overcome vertical thermal density stratifi cation, and an exponential seaward gradient of suspensate concentration at all depths was noted. The observations of Drake et al. (1972) of the winter 1969 record rainfall and flooding are useful in comparison with Fleischer's (1972) "gray layers." Drake cited that over 60 million tons of suspended sediment was discharged by the Santa Clara and Ventura Rivers (which terminate northeast of Santa Barbara Basin) in a month. These rivers, with the Santa Ynez and Santa Ana, are the major rivers emptying into the Borderland, and all are in the northern portion. The oxidized red-brown terrigenous input was easily distinguished from the olive-gray bottom sediments. Drake et al. (1972) documented that most of this suspended bed-load material was initially deposited on the shallow Ventura shelf, some as a 2 km-radius delta and bar of sand and most within 20 km from the river ^"Nepheloid" layers, defined by Ewing and Thorndike (1965) as multidepth low density, low velocity suspension of clay-sized particles, are capable of transporting large volumes of fines into deeper water and depositing them in thin layers of wide extent. 28 mouth. The material was later resuspended and deposited on the outer shelf and towards Santa Barbara Basin by wave-generated currents. Particles were deposited gradu ally seaward in sheltered depressions (as near Montalvo Ridge), and in 3 months had reached depths greater than 500 m (Drake et al., 1972). Most particles traveled at a level within 10 m of the shelf, but at its edge detached and continued at about the same depth over the deep basin due to thermal stratification. Anomalously high suspended particle concentrations resulted from local eddies, cur rent agitation, and wave surges. Drake et al. (1972) also observed that some flood material had been mixed into the underlying sediment by burrowing organisms. One and one-half years later, the Santa Barbara Basin floor was covered with a 2 to 3 cm silt and clay, spongy layer, now yellow and gray in color. These results parallel the more generalized work of McCave (1972) on dynamics of fine-grained sediment trans port. He found that mud moves along the coast and direct ly over a shelf, mostly in a current-caused advective transport, though waves and tidal currents also caused movement. Areas of turbulence lead to high particle con centration, diffusing fines by repeated suspension to qui et areas. Equilibrium between incoming and seaward- transported material and local energy is attained. Much 29 debris is deposited on the slope of inner basins, commonly building fans. McCave (1972) listed possible transport mechanisms on the outer shelf as flow of cold water off the shelf, flow down submarine canyons, bottom Ekman layer transport under large ocean boundary currents, and low concentration turbidity flows. Lithology Emery (i960) proposed that the most frequently sampled sediment on Borderland basins is green mud or clayey silt. These dominantly hemipelagic beds (mean grain size is about 5 Mm) are intercalated periodically with layers of silt or sand. Fleischer (1970) notes that the composition of sediments in the northern basins re flects their provenance in the Transverse Ranges. The largely sedimentary terrain yields a quartz-feldspar- illite suite. The central Transverse Ranges yield an ig neous and metamorphic clastic chlorite-vermiculite-illite suite, while the granitic batholiths of the Peninsular Ranges and Baja California produce a quartz-feldspar suite. Doyle (1973) reported a Sonoran source area of Eocene Poway-type conglomerates and other Paleocene to Holocene sediments in dredge samples off Baja California. Currents act to mix the sediment types. The olive green color of the mud is from chlorite, glauconite, iron-rich 30 montmorillonite, and organic content. Fleischer (1970) also stated that because illite settles faster than mont morillonite, it is proportionally more abundant in near shore basins, even though illite may result from diagene sis of the latter. Lowered sea level will increase the montmorillonite/illite ratio because of this effect. Basin silts contain predominantly quartz and feldspar (Fleischer, 1970). The latter, especially quartz, increase during glacial stages because of increased detrital sediment ad ditions. Fine quartz also increases offshore, illustrating the increased relative importance of eolian deposition away from detrital sources. Other glacial effects noted by Fleischer (1970) are dilution of the plagioclase- chlorite-amphibole suite of Catalina Basin with volcanic sediments exposed on Santa Barbara Bank and the increase of kaolinite since the Pleistocene. He also believed that basin chlorite enrichment occurs because of transport by the California Current. Age^Dating Borderland workers have searched for reliable time markers in order to date and order events, and to aid in correlation. Radiocarbon dating of sediments was attempt ed by Emery and Bray (1962). The problem of measuring "zero ages" for the surface of about 2500 years stems from 31 contamination with* older carbon by the abundant oil seeps on the ocean floor. Also involved may be upward movement of older carbon by biqturbation (laminations indicate this is minimal in places) and interstitial water flow, or re working of relict tests. Bandy (i960) noted a reversal in coiling direction from right- to left-handed in the plank- tonic foraminifera Globerigina pachyderma as temperature drops below 8°C. Such a change has been dated at 12,000 years for the Borderland and makes a convenient time hori zon. Bandy (1971) correlated a left-coiled cool cycle with an upper Miocene Mohole section and uppermost Gilbert and possible lower Gauss magnetic events. This placed the Miocene-Pliocene boundary between 3 and million yrs BP, and reconciles radiometric and biostratigraphic time scales. Moore's (1969) volumetric and structural calcula tions of rates of sedimentation, 5 to 212 cm/1000 yrs, agrees with estimates of Emery and Bray (1962). Emery (i960) has compiled age dates and sedimentation rates for all basins (p. 25*0* Gorsline et al. (1968) used carbon ate as a chronologic indicator and measured total sedi- mentation rates, averaging about 10 mg/cm yr for Tanner Basin. The data indicate that carbonate input and Border land circulation has been relatively constant during the 32 . last 12,000 years. Prensky (1973) extended this record to 32,000 years, with a slight increase of carbonate during nonglacial times, although the center of upwelling shifted several hundred kilometers south during the glacial maxi ma. Exposure of ridges may affect local upwelling and change the path of the California Current. Sedimentology of Measured Biogeochemical Parameters Borderland carbonate content percentages are smal lest in the nearshore basins due to high detrital dilution, but, in the form of formaninifera and coccoliths, may com prise almost one-half of outer basin sediments. This ex plains the observed decrease in grain size seaward from land to the intermediate basins and an increase to the continental slope (Emery, i960). Detrital grains, ex pectedly, generally decrease progressively in size and abundance from shore. Solution in the undersaturated Pacific waters may be another factor, especially in the cooler, deep basins, but its effect on the above patterns is difficult to estimate. Berger and Soutar (1971) ob served a micropaleontologic change across the anaerobic- aerated boundary (or sill depth) of Santa Barbara Basin. Carbonate tests preferentially are lost in aerated envi ronments relative to siliceous fossils. Solution may be accomplished by carbon dioxide production by oxidation' of 33 organic matter or increased exchange of interstitial solu tions with bottom water by burrowers in the aerated versus quiet anaerobic basins. Emery (i960) discussed the role of carbonate as a pH buffer for biochemical reactions in sediments. Carbonate is a useful paleoclimatic tool, as peak relative percents in Borderland basins result during warmer times when terrigenous dilution is at a minimum. Glacial intervals, as discussed above, may result in 3 to 10 times the detrital input. Global climatic belts com press toward the equator during glacials. This increases the intensity of circulation and nutrient upwelling (centered south of the Channel Islands) and may promote carbonate productivity. Arrhenius (1952) reports carbon ate peaks for times of glacially-stimulated Equatorial Current system in deep sea cores. The latter effect probably is negated somewhat by temperature dependence of the planktonic organisms and increased solution. Organic content generally parallels sedimentation patterns displayed by carbonate (summarized by Emery, i960). Areas of moderate deposition of impervious fines protect the organics from bacterial, chemical, and thermal degradation, while high rates dilute or mask the contri bution. Thus, topographic control is again apparent; the northern and nearshore basins receiving turbidites show 3^ low values. The affinity of organics to fine grain sizes is well documented (Emery, i960 and Degens, 19&7) anc^ attributed to either similar settling velocities or chromatigraphic absorption on clays. The outer basins are also low in organic content owing to more complete deamin ation and oxidation during the longer surface exposure and burial times. Total organics are relatively high (up to 10 percent) and fecal pellets and bioturbation are in creased. Equally important as dilution and productivity is the amount of decomposition occurring in settling to the bottom, which depends upon bathymetry and oxygen con tent. Organic content usually decreases downward in a core, suggesting that bacteria and other degenerative pro cesses are active to some depth, although it decreases most rapidly in about the first meter. Emery (i960) pro posed that this often corresponds to the depth of first negative oxidation-reduction potential and decay is slower in the oxygen-depleted lower sediments. Below that level pyrite is free to form. Kaplan (1962) observed two forms of pyrite; micro crystalline pyrite dispersed in reducing silts and clays and coarse fragments forming around dead organisms. Both are believed to be authigenic. Degens (19&5) believed pyrite forms in the neutral or alkaline marine environ ment, whereas marcasite forms in acidic fresh and brackish 35 water. Various metastable, HCl-soluble-iron sulfides are intermediate stages. Berner (1971) postulated that the most important limiting factor for pyrite precipitation is the concentration of metabolizable organic matter, which controls the interstitial hydrogen sulfide concentration and thus the proportion of total iron converted to pyrite. Iron supply is limiting only if overlying waters contain hydrogen sulfide, and sulfate is able to diffuse into the sediments from above. Organic nitrogen is lost preferentially to organic carbon, as the proteinaceous compounds are less resistant than carbon-bearing compounds. Kjeldahl nitrogen repre sents that released from proteinaceous material, which dominates nitrogen-bearing compounds. Thus Kjeldahl and "organic1 1 nitrogen are essentially synonymous. Inorganic nitrogen, as dissolved N^, is usually unimportant. It is generally agreed that multiplying Kjeldahl nitrogen by a factor of 17 is a measure of total organic matter (Emery, I960). Trask (1932) reported that nitrogen does not de crease appreciably with age of core storage, although alterations of compounds may occur and that resistant nitrogen compounds comprise 17 percent of the organic mat ter and ^2 percent of nitrogen constituents. Trask (1932) first reported a relatively constant organic carbon to 36 nitrogen ratio in recent marine sediments, averaging 8.5 worldwide. The ratio increases with geologic age. He attributed the slightly lower ratio of the Channel Island area to the fine texture: organic matter, amount of clays (and thus depositional environment), and moisture content are positively related. Upwelling of nutrients in the area produces prodigous numbers of plankton, organic re mains of which deposit preferentially in protected basins. Trask (1932) estimated about one-half of the nitrogen is lost by diagenesis, especially just after burial. Bacteria split off amino and fatty acid groups, reducing the overall carbon, nitrogen, phosphorus, oxygen, and sulfur content. The average C/N ratio of mixed plankton is about 5-7 (Sverdrup et al., 1942). Emery et; al. (1964) observed that aminoid nitrogen near the surface comprises most of total Kjeldahl nitro gen, but the amount of amino acids decreases with depth faster than Kjeldahl nitrogen, indicating that most of the deep nitrogen exists in forms other than proteinaceous compounds. These could be either organo-clay complexes or high molecular weight organic products as kerogen. Degens (1967) stated that most proteins are bacterially- metabolized in oxidizing environments, and hydrolization is important under reducing conditions. Non-protein polymers incorporate most nitrogen with time, although 37 some have been found in sediments millions of years old. Degens believed most protein is derived from benthonics and microorganisms: the dominant sea water amino acids ornithine and serine may be changed to the observed arginine and lysine in sediments. He also reported that sulfur in the organic residue is proportional to the re dox potential at time of deposition. Also, carbohydrates are easily depolymerized by organisms in oxidizing envi ronments, while sugars may be absorbed by clays in re ducing conditions* Juge (1971) determined that the majority of the bacterial population per gram resides in areas of highest detrital sedimentation. Most organisms are simply carried in from the soil fauna, and outnumber the marine bacterial population,, although the former soon enter the spore stage. Juge (1971) demonstrated that terrestrial bacteria can survive for long periods, but the marine fauna are more numerous at the sediment-water interface. Her plots re vealed that the rate of decrease with depth of thermo philic bacteria is slower in Santa Barbara Basin than others, especially the offshore basins. She measured over 100 organisms/g wet weight of sediment at a depth of 650 m in the Santa Barbara Basin. Trends in Tanner Basin are similar, although the absolute numbers are an order of magnitude less, reflecting the reducing conditions in 38 Santa Barbara Basin. Santa Barbara Basin Structural Geology and Sediments Santa Barbara Basin is the most thoroughly studied of the Borderland basins and is unique because it is the only one sharing the structural grain of the Transverse Range and the similar adjacent Ventura Basin. The Basin does not possess the usual concentration of carbonate in finer sizes as do nearshore basins (Emery, i960), but it has an organic carbon age greater than carbonate near the surface. Emery (i960) attributed this to lesser reworked carbonate since the Basin lacks a submarine canyon,^ has gentle side slopes, the shelf to the north possesses very little carbonate, and reworked organic carbon (from oil seeps) is common. Harman (196*0 holds greater dilution by elastics and the breakdown of small tests by detritus- eating organisms responsible for the planktonic foraminifera-impoverished condition of the shelf. Berger and Soutar (1971) add as agents of decreased carbonate resuspension of tests by benthos and later settling into the quiet basin and ingestion and dissolution within ^"Moore (1969) described areas of channeling on the northern and western edges of the Basin, some with large aprons. 39 acidic guts by benthos. The water here is undersaturated with calcium carbonate below the top 100 m, with a slight decrease in undersaturation below sill depth (Emery, i960), which explains the increased dissolution above sill depth. In the aerated portion, burrowing activity and re sulting increased exchange between interstitial and bottom water and carbon dioxide production maintain undersatura tion. Organic coatings on tests inhibit dissolution from anaerobes. Santa Barbara Basin's maximum depth reaches below 625 m. Emery (i960) reported an average median diameter for bottom sediments at ^.5 >m, about 10 percent GaCO^ at the surface, and that carbonate data indicates uniform depositional rates in the top 3 m of most cores and is somewhat slower before then. Moore (1969) measured over 750 m of sediment fill in the smoothed Basin and notes that draping of strata from the Basin flanks indicates hemipelagic deposition and compaction. An anticlinal nose constitutes the Basin's northern edge. Hulsemann and Emery (I96I) divided the bottom sedi ments into four types: (1) laminated mud, consisting of alternating light varves from summer radiolarian and diatom blooms and dark varves from winter flood, which indicate the absence of burrowing benthos for their pre servation; (2) homogeneous sediments, which, since they ^0 contain fecal pellets and burrows and are more common in the shallower parts indicates bioturbation; (3) disturbed sediment, a brecciated stage intermediate between the above; and (4) turbidites. Turbidites are gray in color, display finer size (owing to a deficiency of biogenic particles >20 )m), possess lower organics and carbonate, occasional graded bedding, and decrease in size and fre quency to the southeast. They could be correlated (as opposed to such beds in other basins) by spacing and thick ness with silty layers throughout the Basin. Fleischer (1970), however, determined with drainage area calculations and statistical mineralogic fit that these sediments are suspended flood deposits, chiefly from the Santa Clara River, with an average periodicity of about 120 years.^ As noted earlier, Drakefs (1972) observations of sediment dispersal by wind-driven currents after the 1969 flood confirm this. His surface current maps show movement southeastward along the coast near the Santa Clara River and northeast movement toward Santa Barbara Basin in the center of the Santa Barbara Channel. Turbid loads and flood sediment thickness also branched westward. “ '"Non-flood sediments still show the River as chief source, but display increased dilution of westerly current-derived sources. 41 Oceanography Fleischer (1970) noted a westerly current of up to 0.5 knots paralleling the northern Santa Barbara shelf, blocking southerly escape of suspended particles, and Kolpack (l97i) depicted this flow returning easterly in the area between the coast and the Channel Islands. Kol pack 's drift card experiment shows that normal surface water circulation is the result of opposing currents enter ing each end of the Santa Barbara Channel and meeting be tween Santa Barbara and Santa Cruz Islands, plus wind and topographic effects. A complex eddy pattern is thus superimposed on the stable counterclockwise cell in the western portion of the Channel (powered by a current from the northwest) and the northeasterly flow in the eastern part. Drake et al. (1972) also observed a flow from the west below 250 m. As previously discussed, the oxygen content of the present current is 0.50 to less than 0.10 ml/L (Hulsemann and Emery, 1961) because water entering the western end with sill depth of 475 m coincides with the local oxygen minimum (^00 to 600 m in the North Pacific). Strongly reducing conditions result further from accumulation of unoxidized sinking organic matter; the surface water ex periences the highest organic productivity due to up- k2 welling. Kolpack’s (1971) cross-sections show bottom oxygen saturation less than 5 percent and that phosphate content ranges from 0.^0 jug-at/l at the surface to greater than 3-6 at the bottom (about 625 m) • Hydrogen sulfide (up to 0.^ ml/L), owing to sulfate-reducing bacteria, and ammonia are important interstitially (Emery, i960). Emery and Bray (1962) measured the highest sedimentation rate in Santa Barbara, up to 180 cm/1000 years in places. Sholkovitz and Gieskes (1971) observed an apparent rapid flushing of Santa Barbara Basin in May of 1970- From detailed vertical profiles, they recorded during this period of high upwelling an increase of oxygen content from 0.05 to 0.10 ml/L to 0.35 to 0.^5 ml/L, a temperature decrease of 0.1^ to 0.19°C, and a decrease in the rapid reduction of nitrate below sill depth. Conditions re turned to normal in the next 2 months\ calculations show that temperature increased 0.02 to 0.0^°C/month and the oxygen consumption rate was 1.3 ml/L-yr. Water from deep basins also has been observed in shallow water, displaying the dynamic nature of Borderland oceanography. k 3 Yelero Basin Structural Geology and Sediments Bottom characteristics of Velero Basin reflect its great distance from sediment source. Separated by unfilled basins from the already meager southern source, only light hemipelagic sedimentation occurs. Its rugged topography, including large fault scarps, as seen in seismic profiles (Moore, 1969), contrast with the smoothed, landward South San Clemente Basin. Velero Basin is the deepest of those basins studied, with a bottom depth of about 2600 m and sill depth approximately 2000 m (Emery, i960). Oceanography Water entering the Basin is derived from well below the local oxygen minimum zone and is well-aerated. Emery (i960) recorded a temperature of 2.5°C, salinity of 3^.5^ ppt, and an oxygen content of 2.0 ml/L. Current flow over the Basin is generally from the south-flowing Calif ornia Current. 44 EXPERIMENTAL METHODS AND RESULTS Sample Collection and Preparation The cores, from the archives of the Allan Hancock Foundation, were collected by the R/V Velero IV using a modified 5-cm diameter, 6-m long, plastic-lined Kullenberg piston core. The process of core collection destroys the top 10 to 20 cm of sediment. Some downbowing of sediment, as displayed by layers in several of the cores, may occur because of friction along the corer wall. The cores were cut into 1-m segments and extruded with a piston and rod and were then measured, labeled, and described, and still wet portions were sealed in plastic for storage. One-cm thick slices of the core were placed on plastic sheets and radiographed. Samples were taken at desired intervals, homogenized, split, ground to size, and oven-dried overnight before chemical analysis. An approximately 15-g portion of the sample was retained in the original wet state for pipette and X-ray analysis. All procedures are standard at the Sedimentologic Research Laboratory, Uni versity of Southern California. Core localities and water depths are shown on 45 Table I. Cores AHF 16137 and 17640 from Santa Barbara Basin were sampled by facies, not the usual 10-cm inter vals. The distinction between gray layers, homogeneous, and laminated zones was made by radiograph analysis, and allowed a more detailed, significant correlation. These two are thus test cores, with more detailed size and compositional analysis devoted to them. It was hoped also to minimize the large error inherent in geologic sampling procedures, so that only analytical error limited inter pretation. The regular, 10-cm sampling procedure is adequate for most purposes, as delineating gross size or chemical patterns with time, and correlation with the test cores is still useful, especially for paleoclimatic trends and where routine sampling was within a single defined facies. The test cores (and others) were chosen as typical of their areas of the Basin. Core AHF 11270 was used in Fleischer's (1970) mineralogic study, collected in November, 1966. Clay mineralogy and size data are used, and the biochemical parameters were made on his 10-cm interval samples. Core AHF 16830 from Velero Basin was bottled for Prensky's (1973) carbonate study; his values for this and sand fraction are used here and other parameters subsequently were undertaken (Mulhe.rn, 197*0 ■ 46 Table I. Location and water depth numbers, as displayed in of cores, with Allan Hancock Foundation Figure 1. (AHF) AHF Station Number Coordinates Basin Water Depth (m) Sill Depth (m) 11270 Lat.-34°l4'18"N Long.-120°02'01"W Santa Barbara 600 475 16137 Lat.-3^°13'07"N Long.-120°17'30"W Santa Barbara 570 ij-75 176^0 Lat.-34°l6'55"N Long.-119 59'10"W Santa Barbara 560 ij-75 16830 Lat.-31°25'05"N Long.-118025'00"W Velero 2^51 1870 • p - -0 Core Description and Radiography Appendix I contains the results of visual inspec tion of the wet core, aided by hand lens and Munsell Color Chart, freshly extruded and split in halves. These data are also represented with depth adjacent to analytical curves in Figures 2 through 5- Color, size variations, and gross structures as partings and burrows were observed. In many cases, the gray layers of Santa Barbara Basin cores were apparent. Radiographs were necessary to see most fine details as laminated portions and bioturbation. Radiographs brought out gray layers better, and were used for labeling a horizon as such. Slight differences in water content because of textural variations affect ab sorption of X-rays, and may thus distinguish silty from clay zones. Large sheets of commercial X-ray film, with 1- to 2-minute exposures in an industrial X-ray photo graphic unit were employed. Gray layers are most numerous in AHF 11270 and 17640 from central and eastern Santa Barbara Basin, respectively. This reflects the Santa Clara River to the east as source for the flood layers, as already discussed. The western core, AHF l6l37» received only distal portions of the larger floods. All cores from the Basin contain about three-quarters of their gray layers in the lower 48 Figure 2. Experimental data with depth for AHF 11270, Santa Barbara Basin, by facies. Samples for biogeochemical parameters were split from 10-cm intervals, so facies designation is not used. Exam ination of the core description reveals if sampling has been exclusively in one facies or is a mixture of both. Smoothed curves represent a running average of three adjacent values. Texture and clay mineralogy data from Fleischer (1970). k9 F I G U R E 2 11270 C/N 3 0 0 . . C h l o r i t e V e r m i c u l i t e D e p t h , Core cm D e s c r i p t i o n C l o y , S i l t , % C l d y Mineralogy, % CaCO @ o = G r o y L a y e r Fades Symbolsip _ Figure 3* Experimental data with depth for AHF l6l37» Santa Barbara Basin, by facies. A lessening of density of horizontal lines on core description (representing laminations) indicates fainter and less persistent laminae. Smoothed curves represent a running average of three adjacent values. 51 30CL- AHF 1 6 1 3 7 F I G U R E 3 1 0 0. 200. - 4 0 0 . . 500— 60Q__ l l l i t e S m e c tite M i x e d Layer K a o i i n i t e D e p t h , Core cm D e s c r i p t i o n C l a y , S i l t ,% S and.% 1 1 2 I 1 4 5 □ o 'Homogenous H « 'GrayLayer H * 8 L a m i n a t e d nrr CacOj ) 1012 C l a y M i n e r a l o g y , % Biogeochemical Parameters, % 5 2 Figure k \ Experimental data with depth for AHF 176^0, Santa Barbara Basin, by facies. A lessening of density of horizontal lines on core description (representing laminations) indicates fainter and less persistent laminae. Curved lines on core description indicate contorted laminae. Smoothed curves represent a running average of three adjacent values. 53 200 ioo_ 3CXL- 500 6 0 (L 40Q h = h e AHF 17640 F I G U R E 4 C/N C l a y S i l t Smectite 6 . + M i x e d Layer K a o l m i t e m r w i r e m m n bFtt N C/N 0 25 50 75 100 D e p t h , Core cm D e s c r i p t i o n C l a y , S i l t , % Facies Symbols; Sand, % [] o 'Homogenous g d :G r a y L a y e r H • 'Laminated 2 3 4 5 0 2 4 6 81012 C l ° y Mineralogy//* t CaCOj Biogeochemical P a ra m e te rs , % 5 4 Figure 5. Experimental data with depth for AHF 16830, Velero Basin. Samples for bio geochemical parameters were split from 10-cm intervals, so facies designation is not used. Examination of core de scription reveals facies sampled. Smoothed curves represent a running average of three adjacent values. Sand percent, microfaunal time horizons, and carbonate values from Prensky (1973)* 55 100. ? 0 ( L 300 400 5 0 0 . 600 F I G U R E 5 AHF 1 6 8 3 0 7 5 0 0 B P ' 1 2 , 0 0 0 B P - I 7 . 0 0 0 B P ? 3 0 . 0 0 0 B P T C / N D epth, Core cm D e s c r i p t i o n Sand, % 1 : i 4 5 C 5 6 1012 (^18 20 2 2 2 4 2 6 2 8 3 0 T i m e Datum □ o 'Homogenous F a c i e s Symbols:, 0 * laminated Biogeochemical Pgrametgrs 5 6 one-half of the core, including all the thicker layers. This implies more intense rainstorms and increased ter restrial erosion during the time represented there. The absence of bioturbated homogeneous layers in the central core, AHF 11270, reflects continuous euxinic conditions and/or diminished benthonic fauna at this depth. The less deep, flanking cores probably experienced more flushing by oxygenated water. Concentration of homo geneous zones near the bottom of AHF 16137 and 176^0 may indicate increased flushing activity of Santa Barbara Basin in the past. Much gradational and fainter lamina tion is visible toward the bottoms, however, suggesting * the phenomenon may be an artifact. It may reflect drying < of cores before photographying of laminae obscured by com paction processes. Homogeneous zones are also concentrat ed at the top of the cores. Of interest would be to ob tain longer cores penetrating older time horizons in Santa Barbara Basin in order to determine any correlation of these two facies with paleoclimates. Core AHF 16830 from Velero Basin displays laminated zones only at 126 to 131 cm and 206 to 213 cm, displaying abundant bioturbation throughout most of the depositional history. Lying far below the local oxygen minimum zone, ample oxygen was supplied to the benthos. The few lami nated zones present may represent a generally less abun- 57 dant fauna in the deep water or times of reducing condi tions . Owing to extensive vertical burrowing, the number of laminated zones represent a minimum of euxinic or bar ren periods. Churning by bottom currents is assumed to be insignificant. Size Analysis Methods Size analysis on core AHF 11270, including gray lay ers, was performed and described by Fleischer (1970) and on core AHF 16830 by Prensky (1973)- Size analysis was not undertaken on gray layers in the test cores; varia tions with composition in hemipelagic facies were sought. Sample splits were retained in their original moist state after the cores were opened to avoid clay alteration and aggregation. Standard pipette and sieve methods were used (Krum- bein and Pettijohn, 1938* P* 162 to l8l) to separate the clay, silt, and sand fractions. ’ ’Clay” is here used to refer to particles smaller than ^ jum diameter (Krumbein and Pettijohn, 1938); times of pipette sampling were cal culated from settling times according to Stoke's Law. The sand fraction (>62 jum) was carefully wet seived, washed and saved for microscopic analysis. All signs of flocculation 58 during analysis were eliminated by an acetone wash, three washings with water and overnight soakings in distilled water to remove salts and soluble organics. Centrifuging avoided loss of fines during decanting. In tests, Mara- sperse (0.05 g/500 ml of distilled water with sediment) proved a more reliable dispersing agent than sodium hexa- metaphosphate (Calgon). Duplicate runs on available sam- • • / I pies showed a precision of about 2 percent (-0.4 percent by weight). As for all the following analytical para meters , all glassware, pipettes, and vessels were rinsed carefully with distilled water to avoid contamination at all stages. An aliquot of the clay fraction was bottled for X-ray analysis just after all silt had settled out, yielding the spectrum of clay sizes. Results Examination of Figures 2 through 5 reveals no stri king variation in size, either as mean diameter (AHF 11270), sand percent (all cores), or clay/silt ratios (all cores) in Santa Barbara Basin. The cores contain about equal proportions of silt and clay. Core AHF 17640 from the eastern basin does exhibit, however, a slight coarsen ing of hemipelagic grain size (especially in sand percent) toward the bottom, probably reflecting the increased run off noted by frequency and thickness of gray layers in 59 the lower one-half. Closer proximity to source is re sponsible for the latter core's slight increase in average grain size. As most of the sand consists of foraminifer tests, increased percentage of sand may reflect biogenic input or preservation. Other parameters must be examined to establish the cause. As expected, higher carbonate values correspond to high sand zones. By facies, both test cores show silt-clay ratios greater in homogeneous zones than laminated, possibly ow ing to flocculation of clays in the alimentary canals of benthonic organisms. The difference is more pronounced in the eastern AHF 176^0 which has more homogeneous zones. The high sand percent at 503 to 50^ cm in AHF 176^0 is ex plained by the hard pressure of clumps of mud. This fur ther suggests organic flocculation, such as fecal pellets. It is also possible that the flushing with oxygenated water and later churning winnowed some fines from the homogeneous zones. Fleischer*s (1970) data for AHF 11270 show a slightly smaller mean diameter and better sorting for the gray layers as compared to hemipelagic laminated lutite, which is because of the lack of significant terrigenous sand in gray layers. Sand percent values from AHF 16830, Velero Basin (Prensky, 1973)» are more useful, as they span a much 60 longer time. A peak at the 12,000 yrs BP cold maximum re- fleets increased erosion of land related to glacially increased stream gradients and extensive exposure of the land. The generally smaller sand percent compared to the Santa Barbara cores reflects the greater distance from source of Velero Basin. Micropaleontologic Analysis and Dating Prensky (1973) established reliable time horizons to 30,000 yrs BP in AHF 16830 (Velero Basin) by coiling direction ratios of the planktonic foraminifera Globoro- talia (Turboratalia) pachyderma. Shifts indicating warmer temperatures correlated closely with carbonate (and coarse fraction) peaks at 7500 and 30,000 yrs BP (Fig. 5)* The erratic appearance of the 17*000 yrs BP horizon in other cores prohibits small scale correlation of late Pleistocene climatic events in the Borderland. The shifts are based on radiocarbon and oxygen isotope data (Gorsline and Prensky, 1975) and can be correlated with horizons deter mined in Tanner Basin by Gorsline ejb al. (1968). Such well-defined events are not observed in the cores from Santa Barbara Basin. Extrapolating from a nearby core radiocarbon dated by Emery and Bray (1962), the bottom of the central core, AHF 11270, is roughly 6000 to 8000 years old. The two flanking test cores are not 61 as long, but are in areas of slightly less sedimentation, so their bases are about the same ages. Thus, only the general cooling trend since the 7500 yrs BP hypsithermal is observed. Emery (i960) notes a decreased sedimentation rate in Santa Barbara Basin prior to about ^000 to 5000 yrs BP, which as discussed later, suggests a higher sea level. Micropaleontologic analysis of the coarse fraction (^=.62 jum-). , from Santa Barbara Basin cores was kindly pro vided by Mr. T. Demere. The faunas, summarized in Table II, reveal a major event at about 350 cm deep in all three cores. Below this horizon, a larger and diverse benthic fauna is observed. Numerous Bolivina argentea (common on basin slopes) and Uvigerina peregrina indicate a more oxy genated environment during these times. The event may re present the 7500 yrs BP horizon, but with radiocarbon dates by Emery and Bray (1962), this horizon probably was not penetrated. The event may signal return to poorly- oxygenated conditions as sea level fell and the oxygen minimum zone shifted relative to sill depth after the 7000 yrs BP high sea level stand. The higher sea level during that period may have been accompanied by increased coastal runoff. 62 Table II. Summary of dominant foraminifera in Santa Barbara Basin cores. Although sampling was at every 50 cm, species are listed only at horizons with sig nificant changes of fauna. Radiolaria, as Lamprocyrtis neoheteroporos and L. haysi, occur rarely in the sediments but suggest past circulation of Pacific water masses similar to that of present (A. Price, personal communi cation)., In AHF 11270 all samples contain about 10 percent of the plank- tonics Gl. eggeri, Glr. scitula, Glr. truncatulinoides, and the benthonics Bol. pacifica, Bol. seminuda, Bol. vaughani, and Sugg, eckisi. Abbreviations are: L, laminated; H, homogeneous; GL, gray layer; Bol., Bolivina; Gl., Globerigina; Glr., Globorotalia; Sugg., Suggrunda; Lox., Loxostomum. Interval (cm), Facies, and General Comments Species AHF 11270 0-10 (L) Low oxygen, plank- tonic fauna Gl. pachyderma, A; Gl. bulloides, C; Gl. quinque- loba, C. 200-210 (GL) More benthonic fauna Bol. argentea, A; Gl. pachyderma, C. 3^0-350 (GL) Flood layer Barren. 360-370 (L) Abundant benthonic fauna, well-oxygenated Bol. argentea, A; Gl. pachyderma, C. ^30-^0 (GL) Flood layer with basin slope fauna Bol. argentea, A.; Uvigerina peregrina, A. ON Table II. Summary of dominant foraminifera in Santa Barbara Basin cores. (Cont.) Interval (cm), Facies, and General Comments Species 610-620 (L) Benthonics Bol. argentea, A; Gl. pachyderma, C. AHF 16137 5-7 (L) Sparse, planktonic fauna, unkeeled, no costae Gl. pachyderma, A; Gl. bulloides, C; Gl. quinque- loba, C; Glr. hirsuta, C. 1^6-1^8 (H) Abundant plankton- ics, keeled, costae Gl. pachyderma, C; Gl. bulloides, C; Bol. argen tea, C. 185-178 (L) Sparse planktonic fauna Gl. pachyderma, C; Gl. quinqueloba, C; Bol. argentea, C. 36^-366 (L) Abundant benthonic fauna Bol. argentea, A; Gl. bulloides, A; Gl. pachy derma, C; Uvigerina peregrina, C. ^51-^53 (H) Sparse fauna Bol. argentea, A; Uvigerina peregrina, C; Gl. pachyderma, C; Gl. bulloides, C; Pyrite, C. o\ Table I I . Summary of dominant foraminifera in Santa Barbara Basin cores. (Cont.) Interval (cm), Facies, and G eneral C eminent s Species AHF 176^0 0-^ (H) Sparse, planktonic fauna, unkeeled, no costae Gl. pachyderma, C; Gl. quinqueloba, C; Bol. argentea, C. 103-105 (L) Planktonic flood, unkeeled, short costae Gl. quinqueloba, C; Gl. bulloides, C; Bol. argen tea, A; Bol. advena, C. 1^6-1^8 (H) Benthonic.flood, unkeeled, short costae Bol. argentea, A; Gl. quinqueloba, C; Gl. bul loides, C; Gl. pachyderma, C. 305-307 (H) Sparse fauna, longer costae, unkeeled Sugg, eckisi, C; Lox. pseudobeyrichi, C; Radio- laria, C. ^1^-^16 (L) More abundant thought juvenile fauna Gl. pachyderma, A; Sugg, eckisi, C; Gl. bul loides, C; Bol. spissa, C. ^75-^77 (H) Benthonic flood, keeled, costae Bol. argentea, A; Bol. advena, C; Uvigerina peregrina, C; Gl. bulloides, C; Gl. pachyderma, C; Lox. pseudoberrichi, C. 503-50^ (H) Keeled ON Bol. argentea, A; Uvigerina peregrina, C; Gl. pachyderma, C; Gl. bulloides, C. Organic Nitrogen Methods The micro-Kjeldahl method (Bradstreet, 1965» Chapters 1 through 4) was used to determine the aminoid nitrogen content. The terms Kjeldahl, aminoid, protein- aceous, and "organic" nitrogen are essentially synonymous. Measured are the -NHg groups (amines, amides, proteins and ammonium compounds). Azo (with N=N or N=0 bonds) or nitro compounds require special treatment and are geolog ically insignificant. Atmospheric nitrogen is lost during boiling. Blank runs revealed no measureable aminoid nitrogen in the reagents or apparatus. Approximately 20 percent of all analytical runs were standards of a known concentra tion of ammonium sulfate. This insured an accurate cor rection factor for calculation of absolute percent organic nitrogen and continually compensated for any variation in reagents. The powdered and weighted sample was boiled in 4 ml of concentrated sulfuric acid for 20 minutes and a few drops of 30 percent hydrogen peroxide were added dur ing digestion. Two pellets of selenized Hengars granules were added as catalysts. Complete deamination and oxida tion (to ammonium sulfate, carbon dioxide, and water for aminoid-, carbon-, and hydrogen-bearing organics, respec- 66 tively) was signaled by a white to yellow-gray solution. The solution was introduced into a distillation vessel, pH raised by adding sodium hydroxide, and the released ammo nia distilled into a boric acid-indicator solution. This was titrated with known hydrochloric acid. Duplicate samples were run, and if precision was not within 5 per cent (±0.01 percent N), more samples were run until this precision was obtained. Results Kjeldahl nitrogen is proportional to the total organic deposition and preservation. All cores display the usual nitrogen affinity for more clayey zones and the decrease with depth (Figs. 2 through 5)- This diagenetic destruction is less dramatic in the Santa Barbara Basin cores and reflects the rapid sedimentation rate and reduc ing conditions, and hence more protection from oxidation and hydration while on the sea floor. The slight increase in organic nitrogen in the central AHF 11270 may reflect either stronger reducing conditions or greater plankton production (especially the protein-rich zooplankton) in the past. The more rapid decrease of nitrogen with depth in Velero Basin is the result of more complete deamination of organic compounds in the slowly-accumulating, oxygen ated sediment. Nitrogen increases to a maximum as the 12,000 yrs BP horizon is approached from older times. This indicates more protection of organics with faster sedimentation in the glacially-controlled climate. Nitro gen decreases with warming. By facies, nitrogen is slightly higher in laminated (average is 0.307 and 0.299 percent) versus homogeneous zones (0.289 and 0.276 percent) in both Santa Barbara Ba sin test cores. This may be explained by partial diges tion of proteinaceous substances by churning benthonic organisms or resulting increased exposure to bacterial decomposition. Gray layers, as expected from influxes of terrigenous sediment, possess low nitrogen values (average is 0.209 and 0.203 percent). As with all biogeochemical parameters in gray layers, the values are probably maximum due to contamination with organics from adjacent facies, either while cutting out thin gray layers or from inter stitial migration of organics into gray layers with time. For the biogeochemical parameters, certain samples, indicated appropriately in Appendix III, were separated and dried approximately 6 years ago. These were analyzed for two reasons: (1) for 315 to 333 cm in AHF 16137 these were all that were available, and (2) for selected gray layers in both pilot cores the separated splits were analyzed to determine any systematic change in values with 68 the length of time of dry storage. Unfortunately, sampling errors exceed analytical uncertainties. While several of the duplicates show much less nitrogen in the previously-dried samples (as 50 to 52 cm and 443 to 445 cm in AHF l6l37 and 52 to 53 cm and 467 to 468 cm#in AHF 17640), others show little difference (as 221 to 222 cm in AHF 16137 and 24 to 25 cm and 499 to 500 cm in AHF 17640). Some older splits even display a small increase in nitro gen (124 to 125 cm and 296 to 297 cm in AHF 17640), indi cating that inclusion of small amounts of surrounding lutites while splitting the gray layers greatly affects nitrogen content. Total and Organic Carbon Methods Total carbon content was determined by induction furnace combustion of carbon compounds to carbon dioxide, absorption into potassium hydroxide solution, and gaso- metric measurement in the LEC0 apparatus (Kolpack and Bell, 1968). Steel rings of known carbon content were used as standards. The most reliable method of deter mining organic carbon was found to be subtracting total carbon from carbonate carbon, also determined gasomet- rically on the same machine (see below). Precision was about 10 percent, and values are minimal due to possible 69 incomplete combustion. Results Carbon compounds are the major and most stable components of organics and a reliable indicator of bio logic input and preservation. The patterns of organic carbon with depth, distance from shore, time of dry stor age, and with facies parallel those of organic nitrogen. The more pronounced decrease in organic carbon in homo geneous (average is 2.429 and 2.408 percent) versus lami nated zones (average is 2.895 and 3*029 percent) suggests selective digestion of carbon complexes over nitrogen compounds. The more biologically-useful of the latter are probably exhausted rapidly during early diagenesis, leav ing only more refractory nitrogen compounds. The significantly larger C/N for laminated (9*518 and 11.002 percent) versus homogeneous (8.307 and 9*628 percent) facies in both Santa Barbara Basin pilot cores appears to confirm the preferential abstraction of carbon compounds over organic nitrogen compounds during benth- onic churning. Another use of the C/N ratio is to deter mine if low organic readings are due to decreased produc tivity or to diagenetic destruction, because nitrogen compounds are less stable in diagenesis. The rather con stant or, with AHF 11270, increasing, ratio with depth 70 indicates that selective destruction of nitrogen had not progressed far. Constant productivity in the overlying waters and benthonic churning are suggested. The average C/N for AHF 16830, Velero Basin, slightly exceeds the world average of 8.5 for marine sediments (Trask, 1932) and suggests more complete deamination due to oxidation during the longer burial times. The ratio increases noticeably down the Velero Basin core. The still larger ratio averages (up to 11.002; individual value reaches 16.0^7) for reducing Santa Barbara Basin are perplexing; with fast sedimentation and non-oxidizing conditions, the C/N ratio should be smaller. Biologic productivity for the two basins may be different. Santa Barbara Basin may receive more carbon-rich phytoplankton and soil organics and Velero Basin more nitrogen-rich zooplankton. The abundance of carbon, however, is most likely related to contamination of the sediments by small bits or emulsions of floating tar or oil from the natural seeps in and near Santa Barbara Basin. A small, black, tarry droplet was found in the beaker in which the sample 0 to 4 cm, AHF 17640, was drying in the oven. These bitumens, also con tain minor amounts of nitrogen, and impair study of dia- genetic change. 71 Carbonate Methods Samples were digested in 2N hydrochloric acid and the resulting carbon dioxide from carbonates absorbed in potassium hydroxide solution and measured gasometrically, as with total carbon. This was tested as more accurate than wet chemical means, as all evolved gases except carbon dioxide are scrubbed out before measurement. Oven- dried reagent grade calcium carbonate was used as a stand ard. Multiplying the carbonate carbon values by 8.33 yielded calcium carbonate percent. Precision was about 8 percent. Maximal values result from digestion of other minor carbonate minerals and perhaps some inert carbon or poorly crystallized clays present. Results Calcium carbonate, while introduced in small quantities from detrital sources (Fleischer, 1970), is chiefly an indicator of biologic productivity (values parallel nitrogen and carbon) and paleoclimates. Assuming a relatively constant productivity for the periods studied, variations in carbonate percent reflects dilution by a varying terrestrial source. During periods of glaci- ality, the latter input may increase an order of magni 72 tude, while organics and carbonate increase 2- or 3-fold. The carbonate curve (as well as the coarse fraction) shows a minimum at the height of glaciality (about 17,000 yrs BP) and maximum during the warmest times around 7500 yrs BP. The lower values for Santa Barbara Basin reflect dilution from the massive nearshore terrigenous influx in spite of greater surface productivity and possibilities of reworked shelf carbonate. The climatic trends observed in Velero Basin are not visible in the Santa Barbara Basin cores, as the latter represent only about 8000 years. Only the slight cooling from the 7500 yrs BP temperature optimum (Gorsline et al.. 1968) is observed. A slight increase with depth, especially in the central AHF 11270, may signify greater productivity. Increased solution since the 7500 yrs BP hypsithermal is also possible. By facies, homogeneous zones possess slightly lower carbonate values. The churning action of the benthos may resuspend smaller carbonate tests and the biologic inges tion of organics may be accompanied by increased solution of carbonate. Differing (though generally low) carbonate content in gray layers again reflects the difficulty in completely isolating these detrital influxes from the surrounding lutite. 73 Clay Mineralogy Methods The clay mineral (here defined as structurally layered hydrous aluminum silicates) percents in Figures 3 and 4 were determined by X-ray diffraction analysis. An aliquot of the jum fraction obtained from pipette analy sis was decanted to the proper slurry concentration, and homogenized by shaking to prevent concentration of finer particles at top. The slurry was sedimented upon porous, unglazed, nitric acid-washed ceramic tiles. Tiles were cut to 27x^6x3 mm to fit the Norelco wide-range goniometer holder. Sufficient clay was added to cover the tile in the irradiated area; no attempt was made to insure a standard thickness of clay. This preparation emphasizes diffraction of X-rays along (OOi.) reciprocal lattice nodes and minimizes that from other crystallographic orienta tions. Sedimentation on porous tile, high slurry density, and complete homogenization of the JUm fraction at all stages of transfer and analysis minimized segregation by size (or settling time) of clays, as noted by Gibbs (1965)* The slurries were dried in a desiccating oven at 50°C for a few hours. Samples were never allowed to dry before sedimentation and were retained at room temperature to preclude alteration of the clays. Interfering peaks of 7^ calcite or organics were not a problem so treatments with hydrochloric acid or hydrogen peroxide were omitted. The dispersant Merasperse and acetone, however, were used in size analysis. Two oriented tiles and 5 diffractograms were pre pared for each sample. One tile was analyzed untreated and then after heat treatment. Heating at 200°C for at least 2 hours collapsed the expandable components and the interstratified expandable smectite layers within illite- smectite mixed-layer clays. Heating at 600°C for 2 hours changed kaolinite to amorphous metakaolin, irreversibly collapsed smectite structures, and enhanced the chlorite (001) peak. Heated samples were irradiated immediately after removal from the oven and at a fast scanning speed to minimize rehydration of the expandable clays. A second oriented tile was saturated with magnesium ions by mixing 2 drops of 0.1 N MgCl^ with the clay slur ry, which filled cation exchange sites and reduced varia tion thereof for determination of the expandable clays. After irradiation, expansion of basal spacings of the smectite-type minerals was accomplished by exposing the tile to an elevated vapor pressure of glycerol (Brunton, 1955) and storing in a glycerol-filled vessel until ir radiation (usually within hours). All diffractograms were obtained using a Norelco 75 X-ray recording diffractometer with a copper target tube (^=1.5^18 A) at 50 kV and 30 ma tube power with a 1° div ergence and antiscattering slit, a 0.006-inch receiving slit, and a Ni filter. Heat-treated tiles were scanned at 2° 2-theta through the angular range 2° to 15° 2-theta; others were scanned at the same speed through 2° to 38° 2-theta. Instrument settings included a rate meter of 10-^ operated on the linear mode, a time constant of 1.0, multiplier of 5 using a Geiger-Muller detection tube. The clay-covered portion of the tile was visually centered in the axis of rotation of the goniometer to effect maximum reflection in the beam path. A correction factor from a blank tile to monitor changes in X-ray intensity proved unnecessary for the level of accuracy desired. A typical diffraction trace is presented in Figure 6. Peak areas at characteristic d-spacings were meas ured after the background curve was smoothed with a French curve. Illite was identified from its basal reflections beginning at 10 Angstroms (A), which is unaffected by all treatments. Tailing off of the 10 A 001 peak toward the low angle side indicates interlayering of expandable units here. The sharp peaks indicate good crystalliza tion. Fleischer (1970) assumes most is dioctahedral, perhaps with minor amounts of biotite, glauconite, and mixed-layer clays. The sequence 001^003': i , 00^ of peak 76 Figure 6. Schematic X-ray diffraction pattern (AHF 176^0, 11 to 14 cm) using Ni- filtered Cu radiation. Abbrevia tions: I, illite; K f kaolinite; S, smectite; M, mixed layer clays; Ch, chlorite; Q, quartz; F, feldspars (undifferentiated); Pf pyrite; and C, calcite. Reflections of clg.y minerals are first order (001) unless otherwise marked; non-clays are not as such distinguished. 77 ML 03), 003 ) ( 002) - 3 00 30 28 26 24 22 20 1 8 16 1 4 1 2 10 8 6 4 2 Oriented intensities suggest high ferric iron content. Smectite (montmorillonite) is defined here as the group of (p°f) -expandable clays, which lose interlayer water and collapse to 10 A upon heating. The observed peaks from d(00l) = 1^.5 A to 15*^ A indicate at least partial Mg-saturation in the untreated condition. The shift of the peak towards 15*^ A with Mg-treatment shows this operation is complete. The small area and incomplete shifting to 17*7 A indicates incomplete glycolization of smectites. This is likely due in part to disruption of orientation or wrinkling during glycolization and result ing peak areas but also indicates some random mixed- layering with illite. The lack of normal strong second order reflection at 7 A indicates random interstratifica tion of structural types. Coulumbic attraction of the hy drated cation and silicate network may bond the layers strongly, inhibiting expansion. The variability of peak area, the difficulty in establishing a base line due to the low 2-theta angle, and the broadness of peaks did not allow use of the 17*7 A peak in quantifying smectite. Rather, the increase in 10 A peak area on the 600°C tile, due to the collapse of expandable and mixed-layer clays (interstratification of several structural types with dif fuse 10 A to 17 A peaks) was used. This method includes smectite plus undifferentiated mixed-layer minerals, as 79 vermiculite, which add to the 10 A peak with heat treat ment. The mixed-layer clay is mostly smectite, as indi cated by at least partial expansion to 17-7 A on glycerol- saturated tiles and no other spacings attributable to mixed-layering after heating to 600°C was noted. Fleisch er (1970) established the presence of beidellite with Li- saturated samples. Smectite plus mixed-layer clays/illite ratios were therefore determined by: (10 A-600qC peak area) - (10 A-untreated peak area) (10 A-untreated peak area). This accounts for the approximately 25-percent increase in smectite over values of Fleischer (1970). The contri bution to the 10 A (001) illite peak was about one-fourth or more of the scattering at 17 A, indicating a signifi cant proportion of mixed-layers. The green color, turning orange at 600°C, suggests considerable iron content. Moderately well-crystallized kaolinite was recog nized by sharp peaks at 7.13 A (00l), 3*5 A (002), and 2.^ A (003). Persistence of the 7*13 A peak at 200°C and glycerolization showed this was not a second order smec tite reflection. The sequence disappeared with destruc tion of kaolinite at 600°C, precluding confusion with a chlorite (002) 7 A peak. Fleischer (1970) interpreted the low shoulder to 8 A on the glycerol-saturated tile as from partly-expanded halloysite. The polymorphs of 80 kaolinite were not distinguished here. Due to interfer ence at 3*3 A with illite (003)t comparison with the 3*5 A kaolinite (002) peak was not possible. Chemical treat ments to remove one component was avoided. Illite/ kaolinite ratios were determined from: (10 A-untreated peak area) (7«13 A 200°C peak area) (1.15). The 200°C tile was used to preclude second order smectite reflections; the form-factor of 1.15 compensates for the rapid decrease in the Lorentz and polarization factors from the 2-theta angles corresponding to 10 A to 7*13 A. The ratios of the three major clays were recast to approximate relative percent of each component in the clay mineral assemblage. Precision was about 5 percent and relative changes observed are probably valid, though accuracy is difficult to establish. Diffraction and sedi mentation methods, sampling techniques, chemical treat ments, calculation methods, degree of clay crystallinity and hydration, chemical composition, and laboratory humid ity vary, as do results. Fleischer’s (1970) technique is similar to the one employed here. Kaolinite values are close, but the approximately 25-percent increase over his montmorillonite values here reflect the present grouping of mixed-layer clays with the smectites and perhaps due to the present use of peak areas rather than heights. 81 Chlorite was present in amounts too small for quantification, although the 13.4 A (001) peak at 600°C and ^,7 A (003) peak were visible. Fleischer (1970) measured 1 to 3 percent for Santa Barbara Basin. This was also the concentration range for vermiculit'e, here just visible at about 14 A on glycerol-saturated tiles and included in the 10 A tail for heated samples. Quartz peaks occurred at 3.3 A (101) and 4.26 A (100), feldspars are weakly visible on some tiles at 6.4 A (020) and 3-2 A (040), those of pyrite at 3*1 A and 2.44 A, and calcite at 3*03 A (which disappears with combustion to CO2 at 600°C). Zeolites, common in continental sediments from weathering of volcanic ash, are not present in Holocene Santa Barbara Basin. Results Looking at the smectitefmixed layer/illite/kaolin- ite ratios in the test Santa Barbara Basin cores, no sig nificant variation in proportions with depth or facies are apparent. Smectite is most common, reflecting semi- arid weathering of the varied parent rocks (especially feldspar- and mica-rich granitic and sedimentary rocks) with lack of leaching of mobile cations such as magnesium. These conditions, with an alkaline environment, inhibits kaolinite formation. The dominance of smectite is thus 82 related to parent rock composition. Volcanic-derived smectite does not completely collapse to 10 A, which occurred in these samples. Minor enrichment by size- related mechanisms, as its selective transport by wind to the sea or its lower settling velocity and suscepti bility to flocculation with small changes in salinity compared to larger clays, may be operating. Fleischer (1970) noted an offshore increase of smectite relative to illite due to differential settling. Illites are common in the regolith of most ter rains 5 this also arrives as detritus. Grim (1968) re ported that degraded illite picks up potassium, magnesi um, and calcium upon contact with seawater and develops interstratification. The mixed layers are also common in the regolith. Grim (1968) believes illite, smectite, and perhaps chlorite slowly form diagenetically at the expense of kaolinite. Increases of the former are not observed here or by Fleischer (1970), Booth (1973)1 or Correns (1938) in recent marine sediments, especially if care is taken to minimize chemical treatment. Such changes prob ably require greater time, temperature, and pressure. The chlorite present comes from schists, gneisses, and iron-bearing sediments on land. Some leaching and formation of vermiculite may have occurred in transport, although the latter is common in the regolith from alter- 83 ation of biotite and phlogopite. Chlorite may form from absorption of Fe or Mg by degraded illite or smectite, but such has a low thermal stability, which is not ob served in the heat-treated tiles. All clays thus appear to be detrital in origin, with probably no more than simple cation exchange and development of interstratifi cation during halmyrolysis, and show no sign of diagene sis at the depths sampled. Drake e_t al. (1972) show by computer fit the dominance of the Santa Clara River as source. Local flood layers correspond most closely, with increased contribu tion from outside sources seen in the hemipelagic sedi ments. Fleischer (1970) measured chlorite in the latter twice that of the flood layers. The California Current derives chlorite from metamorphic sources to the north (the Santa Ynez River, for example, has a chlorite con tent of suspended sediment of almost 5 percent, Fleischer, 1970). The abundance of fine colloidal smectite may be due to this effect in part, but its relatively uniform cation composition minimizes this possibility. Basinal chlorite and vermiculite exceed that of the Santa Clara River by factors of 2 to 10, suggesting either a northern source or, as mentioned in the foregoing section, formation during transport by cation absorption. The even higher chlorite content of seaward basins, where current-borne 84 fines are more important (Fleischer, 1970), indicates the former possibility. 85 DISCUSSION Paleoclimatic Correlations The sedimentary record from Velero Basin (AHF 16830) spans approximately 30,000 years and displays late Pleistocene and Holocene climatic variations. Dates and sedimentation rates were confirmed by radiocarbon measure ments, microfaunal assemblage data, and oxygen isotope data on approximately two dozen Borderland cores (Gorsline and Prensky, 1975) and comparison with parallel patterns described in deep sea sediments (Broecker e_t al. , 1958, and Broecker and van Donk, 1970). In the core, carbonate (and foraminiferal-dominated coarse fraction) minima occur at 17,000 yrs BP and 30,000 yrs BP. These correspond to times of glaciality, when peak terrigenous rates occurred, up to an order of magnitude greater than present (Gorsline and Prensky, 1975)• Tbe quantity of detrital sediments increased due to increased storm frequency and intensity (though possibly in a more nearly arid environment), de creased terrestrial plant cover and increased stream gradients owing to lowered sea level. Abundant large fluvial valleys in California and northwestern Baja 86 California attest to higher rainfall in the past, though most recent work suggests seasonal storms in a still arid to semi-arid climate (L.D. Carter, personal communica tion) . Greater quantities of more immature sediments were transported to the continental slopes, to be trans ferred to basins by mass movement, turbidity currents or increased nepheloid flow. More rigorous oceanic circula tion is postulated, corresponding to compression of the earth’s climatic belts toward the equator (Gorsline and Prensky, 1975)» which increased productivity. With deglaciation following 17»000 yrs BP, and especially 12,000 yrs BP, carbonate content in Velero Basin sediments is observed to increase. It reaches a maximum at the 7500 yrs BP hypsithermal when high sea levels and decreased stream channels trapped sediment on the shelves and flood plains and increased vegetal land cover diminished the detrital dilution of carbonate. The observed decrease since 7500 yrs BP reveals a cooling trend. Variation in organic nitrogen and carbon in the Velero Basin core displays less amplitude than carbonate. This may be a result of the lower concentration of organ ic sediments and the difficulty in distinguishing fine details. Organics also increase following the 17»000 yrs BP glacial maximum up to a factor of ^ because of less 87 detrital dilution, though display generally constant sedi mentation rates (Prensky, 1973)* Organics in Velero Basin then decrease from about 12,000 to 7000 yrs BP, in opposi tion to carbonate. Organics then increase to the surface, also as opposed to carbonate. The latter anomaly may be explained by diagenetic processes; organics are biologi cally lost with increasing time of burial, while carbonate is preserved. The former anomaly requires further inves tigation before an adequate explanation is possible. Generalized correlation of large-scale climatic events may be made by comparison with basins where good control exists. The intermediate (distance from shore) Tanner Basin sediments also display the late Wisconsin glacial cycle (Fig. 7> Gorsline et al., 1968). Tanner Basin cores exhibit a carbonate and organic carbon minimum near 12,000 yrs BP. This is expected considering the sub aerial exposure of the adjacent Santa Rosa-Cortes-Tanner Banks system; turbidity currents from incised submarine canyons to the north and east accelerated sedimentation. Values of carbonate and organic carbon increase in both directions from that time with decreased detrital input as the banks submerged, allowing only input of finer sus pended detritals. Since the cores are from opposite sides of the basin, the basin as a whole probably re ceived a relative maximum of detritals prior to 12,000 88 Figure 7- Experimental data with depth for cores in Tanner Basin from Gorsline et al. (1968). The 12,000 yrs BP horizon, indicated by a horizontal line, is from coiling directions of Globerigina •pachyderma. Radiocarbon ages for AHF 10^26 are in years BP. 89 AHF ! 0 6 1 AHF IQG28 — 50 - <r !00 ▼ 7560 200 12000 B.R 0 0 6 2 6 ) >50- 12740 3 0 0 - ' V ; < 4 0 0 - 450 - 500 -i 550 -4*sSL-30Q0C + 600- - .1C 20 20 40 4.0 MEAN DIAMETER MICRONS ORGANIC NITROGEN .CoCO 3 ORGANIC CARBON Depth in Cm. 90 yrs BP. At that time, Tanner Basin may he considered to he a "nearshore" or coastal hasin, with a concommitant de crease in organic percentage. The presently "offshore" or distant Yelero Basin prohahly became an "intermediate" hasin, shown hy the organic nitrogen and carhon maxima just prior to 12,000 yrs BP. The lower organic percent age in the presently nearshore and intermediate (Tanner) hasins at 12,000 yrs BP was due to increased land exposure and terrigenous input. The reverse was achieved in off shore Yelero Basin. Increased sedimentation rates 12,000 years ago allowed increased preservation (with higher pro ductivity from increased upwelling) of organic matter, which had heen more oxidized owing to the slow sedimenta tion rate in times of higher sea level. The Yelero Basin core shows a relative maximum in coarse fraction sym metrically disposed ahout the 12,000 yrs BP horizon, an increasing carbonate curve, and one of only two laminated intervals just below, supporting the hypothesis. The low organic values at 17.000 yrs BP mark either overcompensa tion of burial and masking in Yelero Basin or a lag in sedimentation with climate. Maximal organic values here occur between 17.000 and 12,000 yrs BP, during the slow * warming. Sanders and Friedman (1969) suggested that the warmest ■ > Quaternary climates may not correspond to highest 91 sea levels, as the northernmost position of the carbonate/ noncarbonate boundary does not quite record the highest emerged marginal marine deposition of the Atlantic. If this boundary is a good indicator of Quaternary climates, the curves suggest a slight lag in sedimentation. The organic minima near 7000 yrs BP thus reflects the sudden deglaciation and long exposure times on the sea floor when sea level was highest. Carbonate thus appears to faithfully record pale- oclimates, but the organics and sand fraction from Velero and Tanner Basinsseem to mirror topographically-controlled sedimentation, closely related to, but perhaps lagging be hind climate change. The high organic content due to higher depositional rate in Velero Basin prior to the 12,000 yrs BP rapid increase of temperature, suggests top ography as the dominant control. Dilution to "nearshore" basins after 17,000 yrs BP was equivalent to allowing an "offshore" basin's depositional rate to approach that of an "intermediate" basin's preglacial values and more rap idly bury the oxidizing organic matter. The expansion of the Borderland's zone of upwelling to the south during the period of glaciality (Prensky, 1973) also may explain the higher organic and coarse fraction contents. Minimal organics and maximal carbonate occur when Velero Basin returned to an "offshore" basin status, with minimal 92 dilution of carbonate and preservation of organics. Rela tive rates of deposition are more in phase; both almost triple during glacial time. As the earth's climatic zones were shifted toward the equator and compressed during gla cial times, the sedimentologic zones paralleling the southern California coast were shifted seaward. The three Santa Barbara Basin cores, owing to their time span of roughly 6000 to 8000 years, are limited in their usefulness in paleoclimatic correlation. The pro nounced irregularities in the curves described above are absent in all facies. The parameters generally reflect the cooling trend since 7500 yrs BP. With time, the det- rital influx may explain the decreasing organic content upward in the core in AHF 11270. The noted increased frequency of flood layers and decreased mineralogic fit with the Santa Clara suite (as a single source) in the lower one-half of the cores suggests increased runoff during the warmer times. Fleischer (1970) theorized a lowered sea level for the lower one-half of AHF 11270, which is not supported by either the biogeochemical an alysis or dates involved. He ascribed this to more abun dant shelf sediment available during a lowered sea level, but increased coastal runoff in general could account for the effect. 93 Sediment Source and Diagenesis Changes of the measured parameters down the core may be explained by a changing source, transport mechan ism, change in sedimentary environment, or diagenesis. This prompted sampling at small discrete layers and re lating mineralogy or source to facies in the control ba sin. As discussed earlier, the larger variations, espe cially in carbonate, are explained by a changing sedi mentary environment (i.e., glacial cycles and changing sea level). Fleischer's (1970) mineralogic and drainage area data for Santa Barbara Basin identify the Santa Clara River as the dominant source of sediment. The River source has been relatively constant during the times studied, although becomes less important in the lower half of AHF 11270. As already postulated, this probably re flects increased coastal runoff. Fleischer (1970) also observed that basin sediments are higher in smectites and chlorite and lower in illite than the river sediments. Smectite abundance is expected from the weathering envi ronment, and minor enrichment may occur because of selec tive transport by wind or lower settling velocity relative to larger clays. Gray layers approximate most closely the River sediments, whereas hemipelagic clays exhibit a 9A higher chlorite content owing to contribution by the California Current. X-ray diffraction data from this study corroborates these results. For both Santa Barbara Basin facies, smec tite coupled with mixed-layer clays make up about 65 per cent, illite 18 percent, and kaolinite about 16 percent of clay minerals. The slight increase in smectite toward the bottom of the western core AHF 16137 possibly may be explained by segregation by settling time with higher sea level and more distant source. The opposite trend is observed in the eastern core, which is closer to the source area, but the trends are only suggestive for the level of accuracy involved. In any case, the semi-arid weathering in local source terrain is verified by high smectite content over kaolinite. The uniform cation com position of smectite negates outside sources. Transport mechanisms for the samples examined are assumed constant for Yelero and Santa Barbara Basins. For Tanner Basin, increased turbidite action due to ex posure of adjacent ridges reveals changes in related source and transport. The glacial patterns of size and composi tional parameters do not appear affected by varying trans port mechanisms. The high productivity of the Borderland is mirrored in the overall high values for organic nitro gen and carbon. Similar values in all basins indicate 95 uniform production and/or dispersion by currents of the semi-buoyant organics. Diagenetic changes are responsible' for further variation observed. The sediment curves in all basins display the affinity of organics to finer sediments and the initial decrease in organic content with depth owing to bacterial decomposition, especially offshore basins. For Santa Barbara Basin, these trends are not pronounced, and nitrogen in AHF 11270, the central and perhaps the core which has undergone the most reduction, increases slightly with depth. This reflects the nearshore basin's rapid sedimentation rate and reducing conditions acting to preserve organic matter with burial. The slight increase with depth may reflect stronger reducing conditions in the lower one-half of the core (no homogeneous zones are pre sent in the entire core), may be either an experimental artifact, or may represent greater plankton production (especially protein-rich zooplankton) in the past. The larger values of organic nitrogen in Tanner Basin (from top to base in AHF 10615 and 10626 it is 0.555 to 0.377 percent and 0.530 to 0.317 percent, respectively) indicate an optimum between preservation and dilution with detritals. Increased upwelling near the Santa Rosa- Cortes Ridge also may be a factor. The smaller amounts of detrital-carried bacteria (Juge, 1971) in the offshore 96 basin may permit higher organic values. The more rapid decrease in nitrogen with depth in Velero Basin portrays the more ready oxidation of organics in non-reducing conditions. The increased C/N ratio with depth reflects the preferential destruction and loss as ammonia of the proteinaceous substances over the more re fractory carbon-bearing compounds. The average C/N slightly exceeding Trask*s (1932) worldwide average of 8.5 for recent marine sediments indicates somewhat more com plete deamination owing to oxidation during the longer burial times. In addition, Trask’s values are for near surface samples. The still-greater C/N ratio for Santa Barbara Basin (average is roughly 8.3 to 11.0) is postulated as related to inclusion in sediment of hydrocarbons from abundant local tar and oil seeps. Such contamination casts doubt upon accurate studies of diagenesis and identification of facies with organic nitrogen and carbon. No evidence for diagenesis or recrystallization of clay minerals is observed. All clays are detrital and only simple cation exchange or development of interstrati fication during halmyrolysis occurred. Perhaps more so that the organics, clay diagenesis requires more time and greater temperatures and pressures. Duplicate runs on horizons sampled and dried 97 in previous years confirm Trask’s (1932) observation that organic nitrogen does not appreciably decrease with time of dry storage. More significant are errors in completely isolating a facies for analysis. The higher carbonate values in Yelero as contrasted to Santa Barbara Basin hemipelagic sediments, neglecting glacial peaks, do not suggest active solution phenomenon (Berger and Soutar, 1970). Oxygenated floors selectively dissolve calcareous tests, which also may be returned to suspension by benthonic churning; in reducing conditions interstitial water becomes saturated with carbonate. Det- rital dilution in Santa Barbara Basin apparently masks the effect for the two basins. Facies Characterization No striking trends between facies with size, bio geochemical parameters, or clays are apparent except for low values for the gray layers. The erratic high values show that contamination from adjacent organic-rich layers during sampling or with interstitial water migration is almost unavoidable. Immediately above certain thick gray layers in AHF 11270 (as 380 to 392 cm and ^30 to ^ 0 cm) organic content is greater than the values below. This would suggest interruption of the decreasing sequence of organics with depth by this pulse of sediment and super 98 position of another sequence above. For grain size, both Santa Barbara Basin test cores have greater silt/clay ratios in homogeneous (49/50 per cent and 52/48 percent) than laminated (45/56 percent and 46/53 percent) zones. This difference is attributed to flocculation of clays in the digestive tracts of benthos and the formation of fecal pellets (observed often as large clumps) in homogeneous zones. The difference is greater in eastern AHF 16137 which has more homogeneous zones. For organic nitrogen, laminated facies average O.307 and 0.294 percent for laminated and O.289 and 0.276 percent for homogeneous zones in the cores. This may be explained by partial digestion of nitrogen-bearing com pounds by the churning benthos or from resulting increased exposure to bacterial decomposition. The more pronounced decrease in organic carbon in homogeneous (2.429 and 2.408 percent) than laminated (2.895 and 3.029 percent) zones indicates selective di gestion of carbon-bearing complexes over nitrogen com pounds. The latter may already be diminished by bacteria. The larger C/N ratio for laminated (9*518 and 11.002 per cent) versus homogeneous (8.307 and 9*628 percent) con firms preferential abstraction of carbon over nitrogen compounds during benthic churning. 99 For carbonate, homogeneous zones possess lower values (7.815 and 6.^07 percent) than laminated (7-999 and 8.399 percent). The effect is most apparent in the east ern, more homogeneous core. Benthonic churning may resus pend finer carbonate tests to settle in less disturbed areas or biologic ingestion may dissolve carbonate. This study shows that the churning and ingestion of bottom lutite by benthonic organisms leads to an in crease in grain size and decrease in organic matter (by roughly 6 percent for nitrogen, 20 percent for carbon), C/N ratio (by 1^ percent), and carbonate content (by 2 to 28 percent). Although the numerical differences between the facies are significantly larger than the precisions of size and organic analysis methods and marginally so for carbonate, it would be impossible to quantify the ef fects for other parts of the ocean without data from each locality. Relative differences and approximate ratios between facies should be observed elsewhere, but the aver age percent change calculated in the foregoing would have to be modified for local environment. Certain localities, for example, may experience different sedimentation rates or source, a higher rain of nitrogen-rich zooplankton than carbon-rich phytoplankton, or tar seeps may hamper quantitative studies of C/N ratios. Thus, quantification of facies variation requires more data from the particular 100 depocenter. It is probable that climatic, source, trans port, and diagenetic changes overwhelm environmentally- caused variations in the Borderland. ' 101 CONCLUSIONS Determination of textural and biogeochemical para meters in selected facies and at closely-spaced intervals, when correlated with previous work and between several ba sins, allowed the following conclusions regarding the sed- imentologic and diagenetic history of the Continental Borderland to be made: 1. The variations of largest magnitude in the cores reflect paleoclimatic fluctuations of the late Pleistocene and Holocene glacial cycles. Carbonate content recorded paleoclimates while organic content and coarse fraction traced topographically controlled sedimentation, closely related to but perhaps lagging behind sea level change. During glacial periods, sed- imentologic zones paralleling the southern Cal ifornia coast shifted seaward. Yelero Basin then became an intermediate basin, as the in creased detrital influx preserved normally oxi dized organic matter. Tanner Basin became a nearshore basin, with the detrital influx di luting or,masking organic content during the 102 glacial maximum 12,000 years ago. Santa Barbara Basin cores displayed only the cooling and low ering sea level trend since the 7500 yrs BP hypsithermal, and the generally low carbonate values reflect increased dilution by terrigen ous material in this nearshore basin. 2. The rapid diagenetic loss of nitrogen with depth in Velero Basin portrays the ready oxidation of organics in non-reducing conditions. Increas ing C/N ratio with depth reveals preferential loss as ammonia of proteinaceous versus carbon- bearing substances. A less pronounced decrease with depth in Santa Barbara Basin reflects pre servation of organics in the faster sedimenta tion rate and reducing conditions. An optimum balance between preservation and dilution by detrital influx of organics is attained in intermediate Tanner Basin. The large C/N ratios in Santa Barbara Basin are due to contamination by local tar and oil seeps. 3. No evidence of diagenesis or recrystallization of clay minerals is observed and only simple cation exchange and development of interstrati fication during halmyrolysis occurred in Santa Barbara Basin. The Santa Clara River as sediment source for _______ 103 Santa Barbara Basin has been essentially con stant for the past 8000 years. The abundance of smectite over kaolinite indicates weathering in semi-arid conditions and uniform cation com position in smectite confirms local source. Segregation by settling time (or particle size) is suggested by a slight relative increase in smectite in the western core. The difference is more pronounced in the lower one-half of the core, corroborating other evidence of higher sea level about ^000 years ago. 5. The studied facies displayed significant (rela tive to analytical error) differences of size and composition. The most striking were be tween Santa Barbara Basin hemipelagic lutite and flood layers. The latter most closely ap proximate Santa Clara River mineralogy and pos sess the smallest organic and carbonate con tents. Erratic values indicate frequent con tamination from adjacent organic-rich layers during sampling or from interstitial water migration. 6. Comparing hemipelagic facies revealed depocen- ter environment. Laminated zones were depos ited in reducing conditions. Periodic influxes 104 of oxygenated water allowed benthonic organisms to chum the sediment. The resulting homogene ous zones have greater silt/clay ratios (49/50 percent and 52/48 percent) than laminated zones (45/56 percent and 46/53 percent), attributed to clay flocculation in the alimentary canals of benthos and the formation of fecal pellets. Benthonic injestion decreased organic matter (by roughly 6 percent for nitrogen, 20 percent for carbon), C/N ratio (by 14 percent), and carbonate content (by 2 to 28 percent) in homo geneous zones. 7. Facies differences exceed analytical precisions, but it is impossible to quantify the effects to apply to other parts of the ocean without data from each particular locality. The persistent relative differences between facies shown in this study identified times of reducing condi tions, but other depocenters may experience dif ferent sedimentary source, rates, proportions of the components, transportation, or types of contamination. Facies or environmental differ ences (up to 28 percent) are dwarfed by clima tic (up to 1000 percent), source type, distance to source, and diagenetic (up to 100 percent) variations in the Borderland. 105 REFERENCES 1 0 6 REFERENCES Arrhenius, G. , 1952, Sediment cores of the East Pacific: Swedish Deep-Sea Expedition (19^7-19^8) Reports, v. 5» fasc. 1, 89 p. 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W., 1973 > Character and origin of marine phos phorites: M.S. thesis, Univ. Southern Calif., 182 p. Prensky, S. E., 1973» Carbonate stratigraphy and related events, California Continental Borderland, M.S. thesis, 110 Univ. Southern California, 207 P- Rittenberg, S. C., Emery, K. 0. and Orr, W. L., 1955, Regeneration of nutrients in sediments of marine basins: Deep-Sea Research, v. 3, P« 23-^5* Ruddiman, W. F. and McIntyre, A., 1973» Time-transgres- sive deglacial retreat of polar waters from the North Atlantic: Quat. Research, v. 3» P- 117-130. Sachs, H. M., 1973» Late Pleistocene history of the North Pacific: Evidence from a quantitative study of radio- laria in core V21-173* Quat. Research, v. 3» P* 89- 98. Sancetta, C., Imbrie, J. and Kipp, N. G., 1973» Climatic record of the past 130,000 years in North Atlantic deep-sea core V23-82: Correlation with the terrestri al record: Quat. Research, v. 3> P* 110-116. Sanders, J. A. and Friedman, G. M. 1969* Position of the regional carbonate/noncarbonate boundary in nearshore sediments along a coast: possible climatic indicator: Geol. Soc. America, v. 80, p. 1789* Shackleton, N. J. and Opdyke, N. D., 1973* Oxygen isotope and paleomagnetic stratigraphy of Equitorial Pacific Core V28-238: oxygen isotope temperatures and ice volumes on a 105 year and 10° year scale: Quat. Research, v. 3» P« 39-55* Shepard, F. P. and Emery, K. 0., 19^1» Submarine topo graphy off the California coast: canyons and tectonic interpretation: Geol. Soc. America Spec. Paper 31- 171 P. Sholkovitz, E. R., 1972, The chemical and physical ocean ography and the interstitial water chemistry of the Santa Barbara Basin: Ph.D. dissertation, Univ. of Calif., San Diego, 176 p. _______ and Gieskes, J. M., 1971» A physical-chemical study of the flushing of the Santa Barbara Basin: Limnol. and Oceanography, v. 16, p. ^79-^89. Sverdrup, H. U., Johnson, M. W. and Fleming, R. H., 19^2, The oceans, their physics, chemistry and general biol ogy: Prentice-Hall, New Jersey, IO87 p. Trask, P. D., 1932, Origin and environment of source sediments of petroleum: Gulf Publishing Co., I l l Houston, ch. 1-5* Uchupi, E., 1961, Submarine geology of the Santa Rosa- Cortes Ridges Jour. Sed. Petrology, v. 31, p. 53^- 5^5* Vedder, J. G., Berger, L. A., Junger, A., Moore, G. W., Roberts, A. E. , Taylor, J. C. and Wagner, H. C. , 197^. Preliminary report on the geology of the Continental Borderland of southern California: U. S. Geol. Survey Misc. Field Studies MF-624, 3^ P« Zobell, C. E., 19^6, Marine microbiology: Chronica Bot- anica, Waltham, Mass., 240 p. 112 APPENDICES 113 Appendix I. Wet core and radiograph descriptions (from the files of the Sedimentology Research Lab oratory, University of Southern California). Data for AHF 11270 from Fleischer (1970) and for AHF 16830 modified from Prensky (1973)• 1 1 ^ AHF 11270 (Santa Barbara Basin) Depth Wet Core Depth Radiograph (cm) Description (cm) Description 0-665 5Y3/2 (olive gray) 0-665 Laminated, punctuated at top grading to by gray layers (light 5Y5/2 (light olive er than surroundings gray) below 200 cm* on radiograph nega Punctuated by gray tive) layers* 20- 21 N5 (medium gray) 22- 23 layers 33- 34 55- 56 92- 94 112-114 123-124 125-127 136 138 144-145 195-198 204-205 208-212 220-222 231-232 247-248 254-258 290-292 314 322-328 340-350 365-366 380-392 392 - sand parting 403-409 430-440 (vague) 479-480 485-486 525-526 535-545 558-559 569-570 631-635 115 AHF 16137 (Santa Barbara Basin) Depth Wet Core Depth Radiograph (cm) Description (cm) Description 0- 40 5Y5/6 (light olive 0-10 Homogeneous and bio- brown), dark laminae turbated, with faint visible (organics?) contorted laminae 40- 81 5Y4/4 (moderate olive 10- 33 Laminated brown), laminated, 33- 42 Homogeneous, with odor to 328 cm very faint laminae 81- 95 10Y4/2 (grayish olive), 42-145 Laminated homogeneous 145-147 Homogeneous, with 95-448 10Y4/2 (grayish olive), faint laminae laminated 147-320 Laminated, becoming 448-454 10Yr/2 (grayish olive), very faint at 260-271 homogeneous cm 320-330 Homogeneous, with 188 Gray layers and laminae faint laminae 220-221 N5 (medium gray) 330-348 Laminated, faint 253.5 348-359 Homogeneous 263 359-400 Laminated, grading 319-320 into homogeneous zone 339-342 below 357 400-454 Homogeneous, with 377.5 traces of laminae ex 400 cept at 440-454 cm 423-426 432.5- 20- 22 Gray layers 433.5 50- 53 217-219 220-222 319-320 330-332 391 415 423 443-447 116 AHF 17640 (Santa Barbara Basin) Depth Wet Core Depth Radiograph (cm) Description (cm) Description 0- 80 5Y4/4 (medium olive 0- 6 Homogeneous brown)• Soupy to 6- 16 Lamina ted, fine 40 cm 16- 23 Homogeneous 80- 85 5Y4/4 (medium olive 26- 51 Homogeneous, with brown) with stringers faint laminae in of 5YR2/1 (brownish places black) 54- 68 Homogeneous 85- 92 5G6/1 (greenish gray) 69- 85 Laminated, very 92-221 5Y4/4 (medium olive faint at top brown) 85- 92 Homogeneous 221-222 5G6/1 (greenish gray) 92-112 Laminated, faint 222-320 5Y4/4 (medium olive 114-144 Laminated brown) 144-150 Homogeneous 320-344 Alternating 5Y4/4 150-190 Laminated, bivalve (medium olive brown) at 178 cm and N5 (medium gray) 190-200 Homogeneous 344-516 5Y4/4 (medium olive 200-212 Laminated brown) (punctuated 212-220 Homogeneous with gray layers) 221-250 Laminated 250-258 Homogeneous 52- 54 N5 (medium gray) layers 258-294 Laminated, contorted 92- 94 296-302 Laminated 112-114 302-308 Homogeneous 183-184 308-357 Laminated, contorted 188-200 at top, becoming very 269-270 faint at bottom 294-296 357-365 Homogeneous 354-358 365-435 Laminated 365-367 435-442 Homogeneous 391-393 442-467 Laminated, very faint 425-427 at 455-460 cm 441-443 468-483 Homogeneous 453-454 484-497 Laminated, faint 467-469 501-509 Homogeneous 483-484 509-516 Laminated, faint at 487-489 bottom, burrow at 497-501 513 cm 23-26 Gray layers 51- 54 68- 69 85- 86 112-114 125-126 183-184 11? Depth (cm) Depth (cm) 0- 2 2- 40 40- 81 81- 99 99-340 358-409 AHF 17640 (Santa Barbara Basin) (continued) Wet Core Depth Radiograph Description (cm) Description 220-221 Gray layers (con- 294- 296 tinued) 326-327 332-333 336-336*5 342-343 354-355 365-367 425-427 442-443 453-454 467-468 483-484 487-489 497-501 AHF 16830 (Velero Basin) Wet Core Description 5Y5/6 (light olive brown) 5Y5/2 (light olive gray) 10Y4/2 (grayish olive) 5Y5/2 (light olive gray, bioturbated at 90-99 cm 10Y4/2 (grayish olive) gray), bioturbated at 35-358 cm 10Y4/2 (grayish olive), homogeneous (as above) with a few worm tubes Depth Radiograph (cm) Description 0-118 Homogeneous, bio turbated with large worm tubes 118-126 Homogeneous, change in density (?) 126-131 Laminated 131-206 Homogeneous, slight change in density marked layer at 148- 206-213 Laminated 213-217 Homogeneous, change in density 217-380 Homogeneous, bio turbated somewhat to 313 cm, highly at 313-380 cm 380-409 Homogeneous, with giant laminae, bio- turbation, and fine vertical "scratchy” worm tubes 118 Appendix II. Tabulation of pipette and sieve size analysis, in percent dry weight of sediment. Sand is coarser than 62^um, silt between 62 and 4jum, and clay particles are finer than 4 jum. Pre cision is about 2 percent (-0.4 percent by weight). Data from core AHF 11270 is from Fleischer (1970) and from AHF 16830 from Prensky (1973)* Facies are included for quick reference (H is homogeneous, L is laminated, GL is gray layer). 119 AHF 11270 (Santa Barbara Basin) Depth Interval (cm) Mean Phi io Clay % Silt % Sand 0-5 (L) 20-21 and 8.49 50.67 48. 73 0.60 22-23 (GL) 9.04 61. 64 38.31. 45.63'* 0.05 45-50 (L) 8.69 53-58 0. 78 92-94 (GL) 9.26 64. 31 35-65 0.04 95-100 (L) 8.37 48.50 50.54 O.96 125-127 (GL) 9.19 63.00 36.91 0.09 150-155 (L) 8.39 49.49 49.43 1.08 195-198 (GL) 8.54 51.05 48.89 0.06 200-204 (L) 8.72 56.46 42.93 0.61 208-212 (GL) 8.93 56.14 43.77 0.09 250-255 (L) 8.66 52.10 47.37 0-53 255-258 (GL) 8.54 50.11 49.84 0.05 3OO-305 (L) 8. 63 52.66 46.66 0. 68 342-347 (GL) 9.00 58. 61 41.37 0.02 350-355 (L) 8.80 55.92 43.70 O.38 383-388 (GL) 8.51 48.82 51.10 0.08 395-400 (L) 8.74 56.40 43.09 0.51 403-408 (GL) 9.01 58.72 41.19 0.09 445-450 (L) 8. 70 53.23 ^5-75 1.02 505-510 (L) 8.60 50.66 48.93 0.41 538-542 (GL) 8.61 50.35 49.61 0.04 555-560 (L) 8.65 52.48 46. 84 0.68 608-613 (L) 8.51 51.29 48.21 0.50 631-635 (GL) 8.71 53.70 46.27 0.03 660-665 (L) 7.67 51.22 48.27 0.51 Average Gray Layer 8.85 56.04 43.90 0.06 Average Laminated 8.54 52.48 46.86 0.66 120 AHF 16137 (Santa Barbara Basin) Depth Interval (cm) % Sand % Silt % Clay 5-7 (H) 0.8 53.0 46.2 20-22 (L) 0.7 54.4 44. 9 83-85 (D 0.4 43.2 56.4 146-148 (H) 0.4 40.4 59.2 185-18? (L) 0.5 44. 7 54.8 275-277 (L) 0.4 40.6 59.0 364-366 (L) 0.7 40.0 59.3 451-453 (H) 0.2 54.5 45.3 Average Laminated 0.5 44.6 55.9 Average Homogeneous 0.5 49.3 50.2 AHF 17640 (Santa Barbara Basin) 0-4 (H) 0.1 57-2 42. 7 11-14 (L) 0.4 44.8 54.8 83-85 (D 0.1 46.8 53.1 103-105 (L) 0.5 44. 0 55.5 146-148 (H) 0.7 50. 6 48. 7 197-200 (H) 0.3 52.7 47.0 218-220 (H) 0.4 48.3 51.3 265-267 (L) 0.7 49. 8 49.5 305-307 (H) 1.0 63.9 35.1 373-375 (D 0.8 50.5 48.7 414-416 (L) 0.5 42. 6 56.9 475-477 (H) 0.9 49.0 50.2 503-504 (H) 1.8 42.9 55.3 Average Laminated 0.5 46.4 53.1 Average Homogeneous 0.7 51.7 47. 6 121 AHF 16830 (Velero Basin) Depth Interval (cm) % Sand 0-10 (H) 0.1 10-20 (H) 0.1 20-30 (H) 0.2 30-^0 (H) 0.2 ^0-50 (H) 0.3 50-60 (H) 0.3 60-70 (H) 0.3 70-80 (H) 0.7 80-90 (H) 0.5 90-100 (H) 0.7 100-110 (H) 0.6 110-120 (H) 0.3 120-130 (L) 0.3 130-1^0 (H) 0.3 1^0-150 (H) 0.2 150-160 (H) 0.1 160-170 (H) 0.1 170-180 (H) 0.1 180-190 (H) 0.1 190-200 (H) 0.2 200-210 (L) 0.7 210-220 (H) 1.0 220-230 (H) 0.7 230-2^0 (H) 0.5 2^0-250 (H) 0.7 250-260 (H) 0.6 260-270 (H) 0.3 270-280 (H) 0.3 280-290 (H) 0.^ 290-300 (H) 0.5 300-310 (H) 0.5 310-320 (H) 0.2 320-330 (H) 0.^ 330-3^0 (H) 0.6 3^0-350 (H) 0.^ 350-360 (H) 0.5 360-370 (H) 0.^ 370-380 (H) 0.7 380-390 (H) 0.7 390-^00 (H) 0.5 ^00-^09 (H) .0.3 122 Appendix III. Tabulation of averaged biogeochemical data (displayed in Figs. 2 through 5) with depth, per dry weight of sample. N org is organic nitrogen, C tot is total carbon, C org is organic carbon, and C/N is organic carbon/ nitrogen ratio. Organic carbon is from total carbon minus carbonate carbon; CaCCU is from carbonate carbon times 8.33* Fa cies abbreviations are H for homogeneous, L for laminated, GL for gray layer, and starred facies were from splits which had dried for several years. For AHF 16137 (315 to 333 cm), these were the only sam ples available; elsewhere (especially du plicates) , they indicate loss with storage time. Carbonate from AHF 16830 from Prensky (1973)1 total carbon on AHF 16830 and AHF 11270 measured by G. Pao and S. Limerick, respectively. 123 AHF 11270 (Santa Barbara Basin) Ten cm interval ending at: % Norg. % Ctot. 7 o Corg. 7 o C/N 7 o CaCO^ 10(L) .264 3.694 2.751 10.42 7.855 20(L) .277 8.122 30(GL) .247 3.410 2.634 10.66 6.464 40(GL) .231 6.331 50(L) .263 4.065 3.553 13.51 4.265 60(GL) .253 1.609 70(L) .242 3.560 2.796 11.55 6.364 80(L) .266 6.631 90(L) .227 3.543 2.819 12.42 6.031 100(GL) .209 4.423 110(L) .245 3.700 3.001 12.25 5.823 120(GL) .200 4.956 130(GL) .172 2.765 2.281 13.26 4.018 140(GL) .245 6.429 150(GL) .210 2.780 2.169 10.33 5.090 160(L) .220 7.099 170(L) .205 3.100 2.392 11.668 5.894 180(L) .220 6.563 190(L) .166 2.575 2.117 12.75 3.482 200(GL) .185 6.697 210(GL) .143 1.965 1.649 11.53 2.632 220(L) .198 4.865 230(GL) .187 3.260 2.549 13.63 5.923 240(GL) .198 6.706 250(GL) .198 3.310 2.615 13.21 5.789 260(GL) .156 3.948 270(L) .185 2.950 2.318 12.53 5.265 280(L) .235 6.181 290(L) .160 1.820 1.567 9.79 2.107 300(GL) .198 5.131 310(L) .211 3.245 2.582 12.23 5.523 320(GL) .216 6.706 330(GL) .132 1.770 1.548 11.73 1.841 340(L) .211 1.974 350(GL) .205 2.345 2.108 9.99 1.974 360(L) .211 5.056 370(GL) .255 2.625 2.154 8.45 3.920 380(L) .320 5.323 390(GL) .170 1.485 1.389 8.17 0.800 400(GL) .184 2.399 410(GL) .241 2.375 2.119 8.79 2.132 420(L) .272 4.790 430(L) .296 3.105 2.352 7.95 6.272 124 AHF 11270 (Santa Barbara Basin) (continued) Ten cm interval ending at: % Norg. % Ctot. % Corg. % C/N to CaCO, 3 440(GL) .272 4.523 450(L) .279 2.675 2.172 7.79 4.182 460(L) .289 6.081 470(L) .271 3.150 2.585 9.50 4.706 480(GL) .306 5.023 490(GL) .292 3.150 2.460 8.43 5.748 500(L) .323 6.872 510(L) .252 2.865 2.222 8.82 5.356 520(L) .255 4.498 530(GL) .286 2.870 2.274 7.95 4.965 540(L) .146 tr 550(L) .252 2.265 1.951 7.74 2.616 560(GL) .303 4.790 570(GL) .309 3.380 2.517 8.15 7.189 580(L) .286 6.872 590(L) .326 3.200 2.510 7.70 5.748 600(L) .255 8.988 610(L) .337 3.475 2.628 7.80 7.056 620(L) .323 7.139 630(L) .282 3.325 2.540 9.01 6.539 640(GL) .238 6.081 650(L) .289 3.265 2.512 8.69 6.272 660(L) .340 6.081 665(L) .292 3.125 2.395 8.20 6.014 125 Depth interval (cm) AHF 16137 7. Norg. (Santa Barbara Basin) % % Ctot. Corg. C/N % CaC03 5- 7 (H) .373 4.240 3.253 8.721 8.218 15- 17 <L) .376 3.939 2.948 7.936 7.955 20- 22 (L) .374 4.260 3.280 8.770 8.165 35- 37 <L) .331 4.251 3.276 9.897 8.118 50- 52 (GL) .230 2.258 2.000 8.696 2.145 50- 52 (GL*) .160 2.230 1.989 12.431 2.006 73- 75 (L) .326 4.371 3.453 10.592 7.647 83- 85 (L) .358 3.890 3.025 8.450 6.456 105-107 (L) .331 4.295 3.393 10.251 7.516 125-127 (L) .348 4.500 3.165 9.045 11.121 146-148 (H) .349 4.176 2.774 7.948 11.670 159-161 (L) .316 3.766 2.734 8.652 8.597 185-187 (L) .296 3.821 3.138 10.601 5.689 203-205 (L> .293 3.591 2.618 8.935 8.104 217-219 (GL*) .156 1.903 1.636 10.487 2.224 220-222 (GL) .195 2.172 1.871 9.697 2.340 221-222 (GL*) .182 1.411 1.125 6.181 2.379 233-235 (L) .300 3.913 2.846 9.452 8.889 252-253 (L) .272 3.418 2.464 9.059 7.949 275-277 (L) .304 3.961 2.696 8.868 10.536 285-287 (L) .283 3.609 2.664 9.413 7.872 315-317 (GL*) .288 3.453 2.543 8.830 7.580 326-328 (H*) .263 3.280 2.295 8.726 8.205 330-333 (GL*) .251 3.770 2.691 10.721 8.986 355-358 (H) .255 3.042 2.066 8.102 8.131 364-366 (L) .290 3.664 2.543 8.769 9.338 373-375 (L) .241 3.215 2.388 9.909 6.889 383.5-384 (L) .292 4.070 3.317 11.360 6.263 390-391 (GL) .254 3.870 2.981 11.736 7.403 400-402 (L) .240 3.391 2.546 10.608 7.040 415-416 (GL) .261 4.741 3.746 14.352 8.284 423-424 (GL) .212 3.477 2.587 12.203 7.414 443-445 (GL) .226 3.650 2.780 12.301 7.249 443-445 (GL*) .150 1.809 1.505 10.033 2.535 445-447 (GL) .157 1.925 1.586 10.102 2.821 451-453 (H) .122 1.209 0.908 7.567 2.502 462-464 (?) .243 3.450 3.100 12.757 7.081 Average Laminated .307 3.863 2.895 9.518 7.999 Average Homogenous .289 2.822 2.429 8.307 7.815 Average Gray Layer .209 2.821 2.235 10.598 4.874 126 AHF 17640 (Santa Barbara Basin) Depth (cm) JO Norg. /o Ctot* Corg. C/N CaCO^ 0- 4 H) .314 3.468 2.528 8.051 7.830 11- 14 L) .288 3.262 2.159 7.467 8.580 23- 25 GL) .158 1.778 1.518 9.608 3.860 24- 25 GL*) .152 1.975 1.776 11.684 7.658 30- 34 H) .331 3.217 2.494 7.535 6.023 52- 54 GL) .384 3.948 2.969 7.732 8.155 52- 53 GL*) .145 2.377 1.656 11.421 6.006 63- 65 H) .286 3.148 2.509 8.773 5.323 68- 69 GL*) .242 3.540 2.751 11.368 6.572 83- 85 L) .214 2.203 1.881 10.223 2.668 85- 86 GL*) .188 2.702 2.341 12.452 3.010 90- 91 GL*) .218 1.760 1.570 7.202 1.583 103-105 L) .268 3.905 2.936 10.955 8.068 112-114 GL) .263 2.925 2.226 8.464 5.823 113-114 GL*) .184 2.672 2.228 12.391 3.266 123-125 GL) .140 1.890 1.561 11.150 2.739 124-125 GL*) .167 1.779 1.417 8.485 3.016 133-135 L) .317 4.207 3.230 10.189 8.138 148-148 H) .248 3.340 2.380 9.597 8.138 156-159 L) .320 3.899 2.738 9.066 9.671 175-178 L) .288 4.007 2.869 9.962 9.480 183-184 GL) .258 4.157 3.104 12.031 8.185 183-184 GL*) .244 2.721 2.017 8.266 5.864 197-200 H) .215 2.507 2.094 9.740 3.440 203-205 L) .288 3.725 3.096 10.750 5.435 218-220 H) .222 2.599 1.848 8.324 6.164 220-221 GL*) .195 2.533 2.052 10.523 4.007 221-222 GL) .264 3.620 2.708 10.258 7.594 233-236 L) .302 3.548 2.600 8.609 7.899 256-258 H) .297 4.086 3.142 10.579 7.864 265-267 L) .258 4.399 3.186 12.349 10.104 277-279 L) .293 3.340 2.421 8.263 7.658 294-296 GL) .193 2.672 2.224 11.523 3.734 296-297 GL*) .282 3.746 2.867 10.167 7.322 305-307 H) .260 3.150 2.635 10.135 4.290 315-317 L) .278 3.431 2.845 10.234 4.883 326-327 GL*) .210 2.605 2.015 9.595 4.915 332-333 GL) .153 1.811 1.402 9.163 3.404 342-343 GL) .211 2.532 2.004 9.498 4.398 343-345 GL*) .279 3.982 2.923 10.477 8.821 365-367 GL) .174 2.575 1.750 10.002 7.270 127 AHF 17640 (Santa Barbara Basin) (continued) Depth interval (cm) % Norg. % Ctot. % Corg. C/N % CaC03 365-366 GL*) .195 2.725 2.051 10.518 5.616 373-375 L) .268 4.191 3.131 11.683 8.828 391-393 GL) .233 3.140 2.223 9.541 7.639 391-392 GL*) .252 3.703 2.903 11.520 6.664 414-416 L) .262 3.445 2.895 11.050 4.585 425-427 GL) .125 1.540 1.204 9.632 2.797 426-427 GL*) .098 1.901 1.553 15.847 2.897 432-435 L) .257 2.468 1.860 7.237 5.065 442-443 GL) .188 2.215 1.766 9.394 3.739 442-443 GL*) .169 2.350 1.358 8.036 8.265 453-454 GL) .316 3.917 3.060 9.684 7.156 467-468 GL) .294 3.575 2.760 9.388 6.789 467-468 GL*) .170 2.226 1.557 9.159 5.571 475-477 H) .298 3.657 2.811 9.433 7.046 487-489 GL) .240 2.553 1.614 6.725 7.824 497-500 GL) .176 2.130 1.692 9.614 3.649 499-500 GL*) .186 1.921 1.107 5.952 6.778 503-504 H) .285 4.978 4.023 14.116 7.955 512-514 L) .276 5.405 4.429 16.047 8.130 Average Laminated .299 3.583 3.029 11.002 8.399 Average Homogenous .276 3.415 2.408 9.628 6.407 Average Gray Layer .203 2.624 2.023 9.511 5.348 128 10 cm interval begin ning at: % Norg, AHF 16830 (Velero Basin) % % Ctot. Corg. C/N % CaC03 0(H) .280 3.70 2.08 7.43 13.52 10(H) .266 3.70 1.88 7.07 15.15 20(H) .231 4.02 1.88 8.14 17.80 30(H) .238 4.10 1.70 7.14 20.01 40(H) .191 4.44 1.70 8.90 22.82 50(H) .200 4.77 1.65 8.25 26.04 60(H) .197 4.82 1.53 7.77 27.42 70(H) .240 5.06 1.52 6.33 29.49 80(H) .215 4.55 1.71 7.95 23.69 90(H) .203 4.65 1.83 9.01 23.51 100(H) .266 4.90 2.33 8.76 21.44 110(H) .250 4.50 2.27 9.08 19.29 120(H) .266 4.12 2.23 8.38 15.72 130(L) .244 4.09 2.35 9.63 14.51 140(H) .287 3.71 2.36 8.22 11.29 150(H) .237 3.60 2.25 9.49 11.25 160(H) .209 3.24 2.03 9.71 10.08 170(H) 2.53 1.81 6.02 180(H) .214 2.74 1.84 8.59 7.54 190(H) .211 2.85 1.82 8.63 7.71 200(H) .206 2.63 1.74 8.45 7.38 210(L) 4.41 1.62 23.26 220(L) .200 2.61 1.72 8.60 7.38 230(H) 2.80 1.74 8.42 240(H) .200 3.00 1.78 8.90 10.19 250(H) 3.51 1.81 14.19 260(H) .223 3.60 2.00 8.97 13.34 270(H) 3.12 1.93 9.88 280(H) .229 3.19 1.85 8.08 11.20 290(H) 3.34 1.84 12.53 300(H) .220 3.49 1.81 8.23 13.99 310(H) 3.95 1.91 16.96 320(H) .211 3.25 1.68 7.96 13.07 330(H) 3.51 1.78 14.43 340(H) .200 3.41 1.62 8.10 14.93 350(H) 4.01 1.63 19.44 360(H) .197 3.31 1.86 9.44 12.08 370(H) 2.98 1.73 10.39 380(H) .203 2.80 1.70 8.37 9.20 390(H) .220 3.10 1.84 8.36 10.52 400(H) .191 2.42 1.76 9.21 5.54 129 Appendix IV. Tabulation of X-ray diffraction clay (A^ jum) mineral analysis of AHF 16137 and 176^0, in relative percent of clay minerals quanti fied. Precision is about 5 percent. Facies are included (H is homogeneous, L is lamin ated) . 130 AHF 16137 (Santa Barbara Basin) Depth Interval % Mixed-layer Clays % (cm) plus Smectite Illite Kaolinite 5-7 (H) 65 19 16 20-22 (L) 57 27 16 83-85 (L) 67 20 13 146-148 (H) 64 19 17 185-187 (L) 64 19 17 275-277 (L) 66 17 17 365—366 (L) 66 18 16 451-453 (H) 70 16 14 Average Homogeneous 66 18 16 Average Laminated 64 16 16 AHF 17640 (Santa Barbara Basin) 0-4 (H) 70 16 14 11-14 (L) 65 20 15 83-85 (L) 63 22 15 103-105 (L) 67 17 16 145-148 (h ) 68 18 •14 197-200 (H) 70 18 12 218-220 (H) 68 20 12 265-267 (L) 64 22 14 305-307 (H) 65 22 13 373-375 (L) 65 22 13 414-416 (L) 65 20 15 475-477 (H) 63 25 12 503-504 (H) 62 18 20 Average Homogeneous 66 19 15 Average Laminated 64 20 16 131

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An analysis of sedimentation rates and cyclicity in the laminated sediments of Santa Monica Basin, California Continental Borderland.

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Carbonate surface sediments of Tanner and Cortes Banks, California continental borderland

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Animal-sediment relationships on Tanner and Cortes Banks, California continental borderland

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Sedimentation in Sebastian Viscaino Bay and vicinity, Baja California, Mexico

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The effects of biological activity on transport of dissolved species across the sediment-water interface of San Francisco Bay

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Depositional systems of the mid-Tertiary Gene Canyon and Copper Basin Formations, eastern Whipple Mountains, California

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Facies and depositional environments of Guadalupian strata (Brushy Canyon and Cherry Canyon Formations), northwestern Delaware Basin, west Texas

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Stratigraphy and sedimentation patterns Upper Miocene Puente formation (Mohnian-Delmontian) northwestern Puente Hills, Los Angeles County, California

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Petrology and diagenesis of the early Miocene Skooner Gulch and Gallaway Formations, Point Arena, California

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Refinement of euxinic biofacies models: California continental borderland

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Engineering properties of Southern California borderland sediments

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Fourier grain-shape analysis of quartz sand from the eastern and central Santa Barbara littoral cell, Southern California

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Sedimentology of the Beck Spring Dolomite, eastern Mojave Desert, California

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Silica dissolution and reaction kinetics in Southern California Borderland sediments

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Pliocene lacustrine stromatolites of the Furnace Creek formation, Death Valley, California

Asset Metadata

Creator Mulhern, Michael Eugene (author)

Core Title Physicochemical characterization of sediment facies and paleoclimatic inferences, California Continental Borderland

Degree Master of Science

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag OAI-PMH Harvest,Paleoclimate Science,Sedimentary Geology

Language English

Contributor Digitized by ProQuest (provenance)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c30-118016

Unique identifier UC11225680

Identifier usctheses-c30-118016 (legacy record id)

Legacy Identifier EP58633.pdf

Dmrecord 118016

Document Type Thesis

Rights Mulhern, Michael Eugene

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions 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...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA