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Vertical sequence analysis of a deep-sea fan system, Santa Paula Creek, California.

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Vertical sequence analysis of a deep-sea fan system, Santa Paula Creek, California.

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Content VERTICAL SEQUENCE ANALYSIS OF A DEEP-SEA FAN SYSTEM, SANTA PAULA CREEK, CALIFORNIA by Bruce Alan Johnson 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, 1978 UMI Number: EP58655 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 Rubl sh*ng UMI EP58655 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 ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 UNIVERSITY OF SOUTHERN CALIFORNIA TH E GRADUATE SCHO OL U N IV E R S IT Y PARK LOS ANGELES. C A L IF O R N IA 9 0 0 0 7 This thesis, written by BRUCE ALAN JOHNSON 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 fulfillm ent of the requirements for the degree of d O r ......... Dean /7 q I ‘l D a t e . b l Q y ^ m h ^ r . . . ^ ? . j . . A S l f i TABLE OF CONTENTS Page LIST OF FIGURES...................... iv LIST OF TABLES............................ vii ABSTRACT . . .............. . 1 INTRODUCTION . 3 General statement * . . ......... 3 Structure, stratigraphy and paleoecology.......... 3 Previous work........ 6 Field work. ........... 9 ORGANIZATION OF SANTA PAULA CREEK SEQUENCE............. 10 Sediment types....................... 10 Fan facies associations.................. ......... 13 Member 1 - Midfan assemblage................. 13 Member 2 - Inner fan assemblage...... 13 Member 3 - Slope channel assemblage.......... 14 MIDFAN ASSEMBLAGE........... 14 Megasequence......................................... 21 Sequence I. .......................................... 22 Sequence IA: Megasequence........ 22 Sequence IB and IC: Interchannel......... 23 Sequence II........... 31 Sequence IIA: Megasequence. . . .............. 31 Sequence I IB: Megasequence................... 32 Sequence IIC, IID, and HE: Interchannel.... 44 Sequence III: Megasequence............... 49 Sequence IV;......... 57 Sequence IVA: Megasequence......... 58 Sequence IVB and IVC: Interchannel.......... 62 Sequence V........................................... 67 Sequence VA: Megasequence.................. 67 Sequence VB: Interchannel.................... 72 ii Page Sequence VI. . . . 75 Sequence VIA: Megasequence........ ..... 78 Sequence VIB: Megasequence.................. 79 Sequence VIC: Megasequence.................. 87 Sequence VII........... 101 Sequence VIIA: Megasequence........... 103 Sequence VIIB: Interchannel transition zone. 106 Deposition of midfan assemblage................... 114 INNER FAN ASSOCIATION.............. 119 Grain size, bed characteristics and structures.... 127 Sandstones and Siltstones . . . ..... 127 Mudstones....... 128 Channels............... . . . .................... .. 130 Deposition of inner fan assemblage................ 134 SLOPE CHANNEL ASSEMBLAGE................. 141 Conglomerate and pebble mudstones................. 143 Thick sands and turbidites. . . ..... .. 170 Deposition of slope channel ...... 175 PALEODIRECTIONS........ 182 Paleocurrents........ . 182 Slumps....... 187 DISCUSSION. .................... 187 CONCLUSIONS............ 193 ACKNOWLEDGMENTS. .... . 194 REFERENCES ...... . _____ 195 APPENDIX A: CHARACTERISTICS OF MEASURED SECTIONS..... 198 APPENDIX B: CLASS MAMMALIA LINNAEUS, 1758......... 200 iii ---1 LIST OF FIGURES Figure Page 1. Location and geologic maps of Santa Paula Creek.., 4 2. Stratigraphy and paleoecology of Ojai area, . . 7 3. Diagram showing fan facies associations....... 15 4. Deep-sea fan model.................... . ....... 17 5. Comparison of classification............... ......... 19 6. Detailed section of megasequence IA........ 25 7. Thick, facies C sandstones at base of mega- sequence IA....... 29 8. Vertical sequence analysis of megasequence IA..... 33 9. Detailed section of interchannel sequence IB...... 35 10. Shallow scour channel and mudstone clasts..... 37 11. Detailed section of interchannel sequence IC...... 38 12. Vertical sequence analysis of megasequences IIA, B 40 13. Detailed section of megasequence IIB......... 42 14. Laminated siltstone rip-up at the base of a medium- grained sandstone layer at 213 m . ....... 45 15. Photographs of layer at 227 m...... ...... . .. 48 16. Detailed section of megasequence III.............. . 50 17. Reverse grading and amalgamation in raegasequence III at 270 m. .......... ..... 53 18. Rip-ups in megasequence III at 265 m 54 19. Vertical sequence analysis of megasequence III.... 55 20. Detailed section of megasequence IVA......... 59 iv Figure Page 21. Convoluted layer in megasequence IVA at 490 m. . . . . 63 22. Vertical sequence analysis of mqgasequence IVA.... 64 23. Basal sandstone layers, facies , of mega sequence V. ..................... , J....... 68 24. Detailed section of megasequence VA.......... ...... 69 25.- Vertical sequence analysis of megasequence VA. . . . . . 73 26. Wavy laminations in lower fine-grained sandstone.. 76 27. Rapid rate of sedimentation....................... 77 28. Detailed section of megasequence VIB.............. 80 29. Scouring conglomerate layer at 645 m.............. 83 30. Thick layers of granuel conglomerate at 654 m 84 31. Vertical sequence analysis of megasequence VIB.... 85 32. Detailed section of megasequence VIC1. ........ 89 33. Pebble conglomerate at 673 m. ....... 92 34. Detailed section of megasequence VIC2, . 93 35. Thin ABCE turbidite at 685 m....................... 97 36. Medium-grained sandstone slump.................... 98 37. Vertical sequence of megasequence VIC1 and VIC2... 99 38. Thin distal turbidites and mudstones of facies D/G 102 39. Abrupt basal contact of megasequence VII at 886 m. 105 40. Base of conglomeratic sandstone layer............. 107 41. Photographs of thick sandstones of mega sequence VII...................................... 108 42. Detailed section at 1214 m........................ 110 43. Three types of amalgamated junctions.............. 115 44. Thin, distal turbidite and medium thick mudstone.. 120 v Figure Page 45. Detailed section of inner fan at 1329 m........... 121 46. Detailed section of inner fan at 1527 m........... 123 47. Detailed section of inner fan at 1577 m. ......... . 125 48. Shell concentrations along mudstone bedding planes at 1354 m. ....... 131 49. Detailed section of small channel at 1396 m. . 132 50. A. Scour and load disruption of the top of basal sandstone layer at 1397 m. B. IJndulose lamina tions and clay-rich zones at 1398 m....... ........ 135 51. Detailed section of small channel at 1565 m....... 136 52. Vertical sequence analysis of small channels at 1396 m and 1565 m,............................. 138 53. Rounded sandstone cobble supported in massive mudstone........................ ........ 145 54. Detailed section of slope channel assemblage...... 148 55. Conglomerate layer 3 at 1733 m.................... 166 56. Imbrication of large clasts near center of con glomerate 7 at .1746 m.. ............................ 168 57. Pebble mudstones 2 and 3 at 1747 m. ...... 169 58. Small faults at 1761 m............................ 171 59. Disrupted mudstone layers at 1743 m............... 173 60. Close-up of burrows at base of Figure 59.......... 176 61. Shells strewn along base of thick sandstone at 1760 m. ....................................... . 177 620 A. Thickness of conglomerate layers decreased upward. B. Pebble mudstones thickened upward...... 180 63. Rose diagram of paleocurrents and slump folds..... 185 vi LIST OF TABLES Table Page 1. Facies classification............................. 11 2. Key for detailed section diagrams................. 24 3. Deposits of the slope channel assemblage... 142 4. Conglomerates and pebble mudstones of slope channel assemblage.. ................ ......... ..... 146 5. Interbedded sandstone and mudstone of slope channel assemblage.... ...... ............ .......... 172 6 . Paleocurrent and slump measurements............... 183 7. Comparison of midfan assemblages at Santa Paula Creek and Apennines.... ........... ..... ... ... ..... 189 vii ABSTRACT The deep-sea sediments exposed at Santa Paula Creek, California form a continuous record of turbidite basin deposition. An 18 00 meter section was examined in this study. Foraminifera ecology studies have indicated that these layers were deposited in a shallowing marine basin. Water depth decreased from 1200 to 270 meters. The Pico to lower Santa Barbara (Middle Pliocene— Lower Pleistocene) sequence examined represents a progradational deep-sea fan system. The vertical facies associations change from midfan to inner fan to slope channel. The midfan assem blage is over 1200 meters thick and is characterized by seven channel fill sequences (megasequences). The mega sequences are composed of medium to very thick layers of sandstone and conglomerate. Thick suites of interchannel mudstone and distal turbidite deposition separate indi vidual channel fill sequences. The inner fan assemblage is characterized by massive medium thick intervals of mudstone which are frequently separated by thin to very thin distal turbidites. The 500 m thick monotonous section is inter rupted twice by small channels. The topmost 6 5 meters of measured section consist: of a sequence of interbedded debris flows and turbidites deposited in a channel cut into the lower slope. The debris flow deposits are muddy 1 conglomerates and pebble mudstones, 50 per cent of which show evidence of flow. Interpretation of paleccurrent measurements and tur bidite sequences indicates that deposition in the fan system was frcm northeast-southwest oriented channels. An average rate of sedimentation of 100 cm/1000 yrs is indi cated for the Pliocene Series. 2 INTRODUCTION General Statement The laterally extensive, rhythmically bedded turbidite sequences of the geologic record have suggested equally extensive basins of accumulation. Recent marine examina tions of the continental slope environment have been of immense help in defining physiographic as well as sedi- mentological elements necessary for an understanding of turbidite and associated resedimented beds. The recog nition of the sedimentary sequence, now known as the Bouma sequence, has taken a secondary position behind the sub division of turbidite facies and facies locations within a turbidite basin. Recent reviews detailing the morphology, sedimentology, and structure of deep-sea fans have prompted this examination of the deep-water section at Santa Paula Creek. Structure, Stratigraphy, and Paleoecology The Plio-Pleistocene section investigated at Santa Paula Creek forms part of the thick, conformable Upper Miocene, Pliocene, and Pleistocene sequence, situated on the north flank of the east-west trending Santa Clara trough (Fig. 1). The syncline is locally bounded on the north by the San Cayetano thrust fault and to the south by the Oakridge fault (Fig. 1). To the north of Santa Figure 1 Location and geologic maps of Santa Paula Creek locality (adapted from Crowell et al,, 1966, Fig. 1). 4 Santa Yno* y n Ez m t n s . OJA! SANTA io 45 FILLMOR£ ,Qjj SANTA PAULA; 55 Qt VINTURA 65 EXPtANATSON Ool Alluvium Qt 120' OXNARD "T""] Turret# Li deposits Formation PQs Qs 40' Oat Formation Mioc one Formations Eocene I — " I i Formations Qs iSANTA 11a 35 Qal 3 4 ' . . . . - A H9 Paula, the San Cayetano fault has thrust Eocene age rocks j over younger rocks of Miocene and Pliocene age. Steeply- dipping Miocene and Pliocene rocks have been overturned near the San Cayetano fault. The stratigraphy of the Santa Paula area is presented in Figure 2. The paleoeco- logy is adapted from Natland's (Natland and Kuenen, 1951; Natland, 19 57) study of Wheeler Canyon, located three miles west of Santa Paula Creek. Faunal collections gathered by Natland disclosed that there was a progressive increase in water depth until Early Pliocene (Repettian) time. Depths in excess of 1200 m (4000 ft) are indicated. Water depth had decreased to 600 m (2000 ft) during the initial deposition of mid-Pico sandstones and conglomerates and, by the end of the Wheelerian Stage, had decreased to less than 300 m (1000 ft). Fauna collected from the Santa Barbara Formation near Fillmore, 15 miles east of Santa Paula, imply a relatively shallow water environment. Com- positionally, the rocks of this formation indicate an in flux of detritus derived from the erosion of uplifted older formations to the northeast (Barker, 1976). Previous Work Santa Paula Creek was one of many sections examined by Natland and Kuenen (1951) in conjunction with their study of the sedimentary history of the Ventura Basin. Specific references were made to the deep-water thin bedded turbidite section exposed at the juncture of Santa Paula Figure 2 Stratigraphy and paleoecology of Ojai area, Ventura Basin, California (modi fied from Natland, 1957, PI, 4). 7 DE POSITIONAL ENVIRONMENT i n 600 DEPTH ? 300 1200 M 900 IA a . CL • o a. a c . n 25 turbidite section exposed at the juncture of Santa Paula and Mudd Creeks. This same section was reinvestigated by Crowell in 1957 and again in 1966. Descriptions of numerous sedimentary structures as well as layer textures included in those reports have helped establish the basis for classification of these thin bedded units. The strati- graphic column included in the 1966 publication has been incorporated into Plate 1. Field Work Field examinations of nearly 1800 meters (6000 ft) of partially lithified sediments of the Plio-Pleistocene deep-water section at Santa Paula Creek were conducted during the summer of 197 7. Measurement of the section |began 200 meters south of Bridge Road, a trestle bridge, where the high angle southward dipping turbidite section forming the eastern creek bank was truncated by horizontal gravel terrace deposits. The section was examined for orientation, bed regularity, grain size and the presence or absence of channels. Detailed measurements and obser vations were made on selected sections when any of the previously mentioned characteristics were observed to change. Diagrams depicting the texture and sedimentary structures of those sections, as well as the observations necessary for their interpretations are presented in the following descriptions. Samples of mudstone collected at numerous locations were found to be inadequate for paleo- 9 ecological evaluation. ORGANIZATION OF SANTA PAULA CREEK SEQUENCES Sediment Types The rocks forming the north flank of the Santa Clara trough comprise the thickest Plio-Pleistocene section in California. The series conformably overlays mudstones of Delmontian Age and forms a south dipping homoclinal sequence of conglomerate, sandstone, siltstone, and shale (Barker, 1976). Texturally, units forming the series range from thick bedded (>150 cm) conglomerate to massive mudstones with paper-thin laminations of clay. Classi fication of these turbidite and resedimented beds has i followed the scheme presented by Walker and Mutti (19 73) (Table 1). Development of individual facies as well as jtheir location will be presented in the descriptions of measured sections. Physically and Petrologically the rocks j are very similar. Mudstones and siltstones are brown, gray, and blue- gray, soft to firm. Mudstones are generally massive; the siltstones may show grading. Sandstones are light brown to buff, fine- to coarse-grained arkosic wackes, containing jgreater than 10 percent mud as matrix (Crowell et. aJL. , 1966). Soft to hard mudstone clasts, identical to asso ciated mudstones, are undoubtedly derived from underlying layers. Many sandstones show coarse tail grading, often 10 I TABLE 1 I I FACIES CLASSIFICATION USED IN THE PRESENT STUDY (AFTER WALKER AND MUTTI, 1973) BOUMA SEQUENCE NOT APPLICABLE Facies A: Coarse-grained conglomerate and sandstone A1 Disorganized conglomerate A2 Organized conglomerate A3 Disorganized pebbly sandstone A4 Organized pebbly sandstone Facies B: Medium-fine to coarse sandstone B1 Massive sandstone with "dish" structure B2 Massive sandstone without "dish” structure BOUMA SEQUENCE APPLICABLE Facies C: Interbedded medium to fine sand stone and mudstone, proximal turbidites Facies D: Interbedded fine to very fine sand stone, siltstone and mudstone, distal turbidites Facies E: Interbedded fine to very fine sand stone, overbank deposits BOUMA SEQUENCE NOT APPLICABLE Facies F: Chaotic deposits formed by down- slope mass movement Facies G: Mudstone, pelagic and hemipelagic deposits 11 through very fine sand and silt and into the clay range. Grading may continue through the clay size. Conglomerates are composed of clasts greater than 2 mm. Clasts, pri marily sandstone and shale, are also of chert, quartzite, and igneous rock. Fossiliferous sandstones are from Eocene sandstones; the shale is from the Monterey Formation (Barker, 1976) . Coarse tail grading is observed in some beds. Conglomerate layers occur in two associations: 1) as a thin to medium-thick (<40 cm) zone at the base of a sandstone layer; or 2) as a thick bed in sequences with other thick beds of sand and gravel. Sandstones and conglomerates are known to be lenti cular, though only minor fluctuations can be seen in the limited exposure of the creek banks. Natland and Kuenen (19 51) reported that the Repetto sandstones and conglo merates of the Wheeler Canyon section lense out to the west, south, and east, and therefore suggests a northerly source area. Barker (1976), further states that "sand stone beds of the basal Middle Pico and Lower Pico pinchout or thin dramatically to surface outcrops in Santa Paula Creek. These Pico sands are potential reservoirs and may contain stratigraphic oil and gas accumulations in the area." The last sentence is particularly striking because of oil stains which were detected in the Lower Pico sands investigated in this study. Turbidite sequences can present a problem in the pre- 12J cise definition of a layer due to the common association of a sandy division and a pelitic or shale division. Most turbidites observed in this study have sharp contacts be tween the mudstone capping of one turbidite and the sandy division of the overlying turbidite. There is usually a gradation from the sand to mud within a particular turbi dite. Bed or layer will therefore specify the sand/mud couplet as a unit. Terms such as division, area, portion, etc., will be used in reference to the sand or mud separately. Fan Facies Association The stratigraphic section measured at Santa Paula Creek (Plate 1) has been subdivided into three members, i or fan facies associations, on the basis of layer thickness, regularity, and grain size. The three members are, in ascending order, member 1, 2, and 3. Member 1 - Midfan Assemblage— The first member forms the bottom 1221 meters and consists of interbedded thick sandstone and conglomerate layers of mutti facies B, C, and A. The layers form multistory sandstone bodies or megasequences (Ricci-Lucchi, 1975). Megasequences are separated from each other by thick suites of mudstone and interbedded mudstone and fine sandstone of facies D, E, and G. The assemblage accumulated in waters from 1200 to 450 m (4000 - 1500 ft) deep (ISLatland, 1957) . Member 2 - Inner Fan Assemblage— The second member I is 507 meters thick and consists of thin layers of fine sandstone and siltstone interbedded with thicker layers jof gray and brown mudstone. The facies represented are D and G. Water depth during deposition was between 6 00 and 270 m (2000 - 900 ft) (Natland, 1957). Member 3 - Slope Channel Assemblage— The third member is composed of thick beds of muddy conglomerate and pebble mudstone of facies F and A. These layers are separated by suites of thin- to thick- layers of sandstone and mud stone of facies D, C, E and B. This assemblage forms the topmost 65 meters of the measured stratigraphic section. Water depth exceeded 270 m (900 ft) during deposition of this unit. An evaluation of the facies, facies associations (Fig. 3) (Walker and Mutti, 1973), water depth and strati graphic position of each member has led to their interpre tation as midfan, inner fan, and slope channel accumula tions, respectively. A sketch of Mutti and Ricci-Lucchi1s (1972) fan model, used in this study, is presented in Figure 4. Figure 5 compares the terminology of this model (Ricci-Lucchi, 1975) with that used in previous studies (Normark, 19 70; Haner, 19 71; Ingersoll, Rich, and Dickinson, (9 77). MIDFAN ASSEMBLAGE The first member includes the Lower and Lower Middle 14 Figure 3 Diagram showing fan facies associations (modified from Walker and Mutti, 1973, Fig. 10). Cl BAS 1C FACIES G R O U P IN G S FACIES IN EACH G ROUP ENVIRONMENT CLASSIFICATION FACIES A S S IG N E D TO EACH ENVIRONM ENT PROXIMAL-EXOTIC PROXIMAL A| #A3 A2/A4,B, B2 i / v - , f SUI SLOPE CHANNELS inner fan BMARINE middle fan F,G SOME Al,A3 MIXTURE OF a 1^3,G SOME M C,D a3/a4 W ITH E T HINNING UP SEQUENCE C/E FANS outer fan fan fringe a4, b2, c * D,C D * G DISTAL THICKENING THICKENING UP SEQUENCE UP SEQUENCE BASIN PLAIN t D,G Deep-sea fan model used in the present study (modified from Ingersoll et_ elI. , 1977, Fig. 12; primarily after Ricci-Lucchi, 1975). CM = channelized midfan, F = fan fringe, FC = fan channel, IC = inter channel area, IF = inner fan, L = deposi- tional lobe, LS = lower slope, MF = midfan, OF = outer fan, OVB = overbank area, PS = passive or prograding slope, SA = slump accumulation, SC = slope channel, SS = slump scar, US = upper slope. ti i . 1 i LXi-t i INCISED CHANNEL O R BREAK IN SLOPE ■t > H i n VHCHANNEt LEVEE INACTIVE LOBE OR CHANNEL \ OF \ MF IS j . SLOPE v v > ^ , SS P S sc SHELF 18 Figure 5. Comparison of classification used in the present study, Ricci-Lucchi1s (1975), with that of other published fan classi fications (modified from Ingersoll et_ ad. 1977, Fig. 11). NORMARK (1970) C A N Y O N LEVEED VALLEY m-r r nT T Tn O N UPPER FAN DISTRI BUTARY C H A N NELS A R E A SUPRAFAN WALKER A N D M U T T I (1973) LEVEED CH ANN EL O N I N N E R FAN C H A N N E L IZE D SUPRAFAN SUPRAFAN DE P O S I- T tO N A L LOBES O U T E R FAN B A S IN P L A IN M U T T 1 A N D RICC I - LUCCHI (1975) DISTRIBUT ARY SYSTEM (CHANNEL IZ E D IN N E R FAN) SEAWARD O U T B U IL D IN G SYSTEM (OUTER FAN) B A S IN P L A I N RICCI- LUCCHI (1975) I N N E R F A N M I D F A N O U T E R F A N B A S I N PLAIN Pico Formation at Santa Paula Creek. The suite is dominated! by seven megasequences, six of which form thinning and fining upward multistory sandstone bodies of facies B, C, and A. Thick accumulations of at least 4 0 meters of fine-grained layers of facies D, E, and G separate.each megasequence and are sometimes found in thinner suites within individual megasequences. Consideration of the stratigraphic position, megasequence trends and fan facies assemblages has indicated a deep-sea midfan environment for the area of deposition of member 1. Megasequence The term "megasequence" has been suggested for the designation of thick sandstone accumulations which are commonly associated with turbidite basins. Ricci-Lucchi (19 75.) defines a megasequence as "a group of layers with bulk sand/pelite ratio higher than 1; it is mostly composed jof, and delimited by, thick to massive turbidites of facies A, B, and C." The identification of the distribution and I jtrend of megasequences are of use in establishing the physiographic provinces in the deep-sea fan model (Fig. 4). Trends may be obtained in field studies, and are useful •for vertical sequence analysis of turbidite basins. Plots of layer number versus layer thickness (L) or coarse jdivision number versus coarse division thickness (CD) are useful for vertical sequence analysis of turbidite basins. Plots of layer number versus layer thickness (L) or coarse 21 division number versus coarse division thickness (CD) are useful in establishing trends (Ricci-Lucchi, 1975). Thin ning upward sequences (termed positive) have been shown to reflect channel fill suites (Ricci-Lucchi, 1975). Thicken ing upward trends (negative) indicate prograding deposi- tional lobes. Sequence I Sequence I, with a thickness of at least 12 8 meters, forms the base of the section measured in this study. The sequence has been broken into three subdivisions which are designated IA, IB, and IC (Plate 1). IA is a thick bedded sequence of sandstone in which the sand/pelite ratio ex ceeds 1. Unit A is the first megasequence. Subunits B and C, with a sand/pelite ration <1, form interchannel deposits between megasequences I and II. Below unit IA, the section has been covered by recent alluvium. Vege tation and alluvium also partially cover the section above IA and IC. Sequence IA; Megasequence--The first megasequence is at least 15 meters thick. Almost 50 meters of section are covered above IA.« The basal 9 meters of the exposed section of sandstones are depicted in Figure 6. The quartz sandstones are stained dark brown to grayish-brown due to residual oil. The three thick basal sandstones (Fig. 7) are noticeably stained a darker brown than were succeeding layers. The beds also have a petroleum odor. 22 Grain Size and Bed Characteristics: Section IA is j i composed of coarse- to fine-grained sandstone, which is sometimes pebbly, facies B2 (Table 1). Pebbles are usually less than 3 cm, but range up to 8 or 9 cm. Most were sub rounded, laminated shale, or calcareous shale. The pebbles are frequently confined to the bottom half of the bed. All layers are coarse tail graded, usually from the base, to a capping gray mudstone. Ten per cent of the mudstones have red brown clay caps or interbeds. Laminations, B, or small scale cross-stratification, C, are very infrequent and almost always occur .in the very fine sand to silt re gion of graded layers. Bedding contacts are normally undulose, due to compaction and/or erosion. Structures: Undulating sandstone over mudstone con tacts are primarily the result of compaction and relief developed is usually less than 1 cm. However, 30 per cent of the contacts show minor scouring; relief rarely exceeded 4 cm. Amalgamation of the sandstone layers at 6.5 m is due to the erosion of a 4 cm brown claystone. Trend: The sandstone sequence is primarily constructed of Bouma AE couplets of facies C, proximal turbidites. Layers, thick at the base of the sequence, gradually thin upward. The thinning upward trend is excellently displayed in the CD and L diagrams (Fig. 8). This trend is continued into sections IB and IC. Sequences IB and IC: Interchannel— The continuous 23 TABLE 2 KEY FOR DETAILED SECTION DIAGRAMS A. STRUCTURES ~TJ~' Load form Scour Organic material, (vood, plant, charcoal) $ Shell "M" Bioturbation structure Lenticular, undulose or wavy bedding ~yi— Flame structure f\S\) Convolute lamination 22L Parallel lamination . Small-scale cross-stratification B. TEXTURE C. CONTACTS b Boulder — . Sharp, flat cb Cobble — —— Gradational P Pebble - -— ' Undulating g Granule D. COLOR ss Sand g Gray s Silt b Brown c Clay t Tan r Red-brown Figure 6 Detailed section of megasequence IA. Table 2 for list of symbols. i See i t 25 r • ST RUCTURES OLO C O L U M N 6 o CTIG.N AEA5U 26 OLOR ST RUCTURES TEXTURE * * C O L U M N r^4 C O L U M N TEXTURE 0! R 6c 28 Figure 7. Thick, facies C sandstones at base of megasequence IA; note gray color due to oil residue on sand grains. Meter stick is for scale. 29 suite in which sections IB and IC were recorded crop out for at least 65 meters. Grain Size, Bed Characteristics and Structures: Bed thickness as well as grain size continue to decrease above IA. Section IB (Fig. 9) is composed of thin to medium thick (4-30 cm) layers of sandstone and mudstone. The coarsest sandstone layer is medium-grained; most are graded or massive fine to very fine sand. Mudstone intervals were thicker than in the underlying section, and averaged around 20 cm. Most mudstones were formed of composite layers of gray and brown muds with thin silt- stone laminae. One 30 cm mudstone layer contained thin lenses of fine sandstone. Shallow scours were noted at the base of some graded sandstones (Fig. 10). The sand/shale ratio had dropped to below 0.5 in sec tion IC (Fig. 11). Bed thickness had also decreased. Tan fine sandstone and siltstones, and gray and brown mudstones, were common. The thin sand and silt units were graded or massive, frequently starting with B divi sions. C and D structures were also very frequent. Con tacts were predominantly flat with little compaction of mudstones. Trend: The thinning and fining upward trend displayed in IA continued through sections IB and IC. Bed thick nesses in the latter sections were all below 30 cm, and mudstone was much more common. The facies represented 30 are the thin turbidites and mudstones of D, E, and G. Sequence I is a channel fill suite deposited during a cycle of channel abandonment. The suite progresses up ward from coarse, high concentration channel flow deposits into a sequence of thin, fine-grained deposits of the interchannel environment. Sequence II The second sequence is subdivided into five units. Units IIA and IIB were located in the megasequence. IIC and IID, facies E and D/G, respectively, were mea sured in the fine-grained layers overlying megasequence II. The fifth, HE, records a return from the interchannel and pelagic mudstones to overbank or near channel sandier accumulations. Sequence IIA: Megasequence--The section between IC and IIA is almost completely covered by vegetation and alluvium. One 3-meter outcrop was measured at 175 m. Grain Size, Bed Characteristics and Structures: The suite measured consists of medium thick (10-40 cm) layers of amalgamated, coarse- to silty fine-grained sandstone of facies B2 and C. The sandstone beds are thinner than those at section IIB. Minor scour and fill channels, less than 3 cm wide and 5 mm deep, load casts, and soft gray mudstone pebbles (<6 cm) make up the range of struc tures observed. One 2 cm B interval and a 2 cm interval of convoluted laminations are the only traction structures. 31 Fifty percent of the sandstones show coarse tail grading, mostly in the upper third of the layer. Trend: Trend in this sequence is hard to assess due to the lack of information directly above and below. Schematic, sand percentage, and CD and L diagrams for IIA are given in Figure 12. The coarse division diagram indicates a possible thickening upward trend; the layer diagram a thinning upward trend. The only positive con clusion is that sequence IIA is part of a second megase quence . Sequence IIB: Megasequence— The interval between IIA and IIB is covered by vegetation and alluvium. Section IIB was measured 8 meters above the base of a thick bedded megasequence which crops out abruptly above thinner layers of IIA (Fig. 13). Grain Size and Bed Characteristics: Section IIB con sists of 90 percent hard, coarse to fine, sandstone and 10 percent gray graded siltstone (Appendix A). Layer thickness ranges between 18 to 95 cm, averaging about 50 cm. Like IIA, the series is composed primarily of amalgamated sandstones which show very little in the way of "classic" turbidite structure. Most amalgamated sand beds can be delineated by abrupt changes in grain size. Cut and fill structures along the base of some layers also aided in the recognition of individual stratum. Structures: The frequency as well as depth of 32 Figure 8. Vertical sequence analysis of megasequence IA. Partial stratigraphic column shows percentage of sandstone. Layered columns specify internal organization of mega sequence into sandstone (white) and pelite (black). 33 0 % send 100- • sissa 9.1 EffiMliaWil ZSkc&M C O no. of unit’s Ct>“ «Hfrs« tiiv. L 0 layer* thick, in cm CD 21 100 22- 100 Figure 9 Detailed section of interchannel sequence IB. 35 C O L U M N DIR. COLOR 5 P Tl P t l * IC h Tl t j i !E S -0 T A u E> 0. CT o» UR M M E « * V 260 t H m *77 Mm | 1 9 1 s s ..b" » 1 l l r ^ - 9 b 1 I k * ■ 7 i S 9 r m K 9 1 gS — b 9 ■1 r*,Sa 250 . H - * l ! F , ' * ' A - ----------------- a ■0 I V s ! ft® y ■ Ptt MM 75 5 | 1 pi t * r * jt '^ j i'i k j pa ? J3§ . Figure 10. Shallow scour channel and mudstone clasts at base of sandstone layer at 75m. 37 Figure 11. Detailed section of interchannel sequence IC. 38 STRUCTURES COLOR TEXTURE C O L U M N DIR. 104 gure 12. Vertical sequence analysis of mega sequences IIA and IIB. 100 % sand 250 3.5 IIB 200 C Dr coarse div. L~ layers thick, in cm CD 100 9 70$ CD To5 Figure 13. Detailed section of megasequence IIB. 42 ................ C O L U M N DIR. COLOR 5 6 TF R H tu 5 1 1C H TUE w IE S I N N J Q T -Q u E > flL C T o > URE 2 M L--------------------------- m M j j i - ■ * 1 -216 a ■ m - i l l b S3 HI hi N M 9 &0 • 9 " « * • O » o o » e o D # * * -215 t ” * 1 f U t i l l [ 1 ^ / J O I o V ^ » 4 0 ^ . . . - 214 t m J l ■ > & a t mm / M i W0 / J s A , I i i scouring in this section exceeds that observed in Se quence I or section IIA. Scours 5 cm deep are recorded in the convoluted sandy siltstone at 213 m (Fig. 14). Rip-ups of siltstone, some 40 cm in length, are strewn along the base of the overlying sandstone. Bent frag ments of siltstone suggest that the layer was still plas tic during the deposition of the succeeding sandstone. Pinch-outs of sandstone and rounded pebbles of red brown mudstone are also found within this section. Trend: CD and L diagrams (Fig. 12) both indicate thinning upward, again suggesting channel filling. The amalgamated thick sands lacking Bouma sequences and dish structure are of facies B2 . Sequences IIC, IIP and HE: Interchannel— The three sequences of IIC, IID and H E form a symmetric trend above the thinning sandstones of megasequence II. The relationship that appears to be represented is near channel deposition to upper channel fill in IIC; inter channel and pelagic open marine in IID; to a return of near-channel accumulation in IIE. An abrupt transition to channelized thick sand and gravel deposits, mega sequence III, is found above IIE. Grain Size, Bed Characteristics and Structures: Sandstone bed thickness as well as coarseness continue to decline between sections IIB and IIC. Sandstone thick nesses average 50 cm in IIB, but drop to half that 5 44 Figure 14. Laminated siltstone rip-up at the base of a medium-grained sandstone layer at 213 m. The sandstone layer is reverse graded at the base from medium- to coarse- grained sand. 45 10 CM meters above. At IIC, 10 meters above IIB, sandstone thicknesses are from 7 to 16 cm, and mudstones, of equal or lesser thickness, separate individual sandstones. Bouma sequences of AE, DE, and ACE are most frequently observed. Contacts are usually flat, but small undula tions indicate minor scouring. Wavy laminations and convoluted layers imply fluctuating currents (Fig. 15). Very few amalgamated sandstone layers are noted. Sandstones are almost nonexistent 15 m above IIB. Medium thick layers of gray mudstone, often punctuated by very thin laminae of siltstone or red brown shale, are common. Very fine sandstones, 2 to 7 cm thick, are usually massive or cross-stratified and separated by 1 0- 15 cm intervals of gray and brown mudstone. Sandstones comprise about 10 per cent of the section. Contacts between sandstones and mudstones are sharp and flat. Six meters prior to the thick layers of megasequence III, section IIE records an increase in the sandstone content of the interchannel deposits. The sequence at IIE is compsed of thin BCE and DE turbidites of facies D, and thin AE, ABE, and ACE turbidites of facies E. Sandstones are tan, fine-grained, and ungraded. Trend: The steady decrease in sandstone thickness coupled with the increase in mudstone partings indicates a withdrawal from the channelized deposits of megase quence II. The environment at IIC was probably near- 47 Figure 15. Photographs of layer at 227 m. A. Massive medium sandstone grades up ward into parallel to undulose lamina tions of fine sandstone. B. Close- up of overlying silty mudstone with isolated load pockets with convoluted interiors 48 channel overbank or upper channel fill. This is sug gested because of the common occurrence of thin fine- to medium-grained sandstones forming AE Bouma sequences. These have been interpreted by Ricci-Lucchi (1975) as tail deposits of large by-passing turbidity currents. The low percentage of sandstone and thick mudstones of IID suggest a greater retreat by active channels. The re surge of sandstone in IIE indicates the opposite trend of that observed in the sections below. The resurge must indicate a return of active channel sedimentation which is confirmed by the thick sandstones of megasequence III. Sequence III Sequence III: Megasequence--Sequence III consists of only one unit, the thick beds of sand and gravel which form megasequence III (Fig. 16). The thick layers begin abruptly above the overbank-interchannel deposits of unit IIE, and crop out for approximately 13 meters be fore being covered by alluvium. The sequence is the coarsest grained of megasequences yet observed and is filled with rip-up mudstone clasts, gravelly sandstones, and channelled contacts. The sequence appears to thin upward. Grain Size and Bed Characteristics: Section III is composed of gravelly coarse- to fine-grained sandstone with mudstone rip-up angular clasts and rounded pebbles, some up to 10 cm in length. Most layers show coarse tail 49 Figure 16. Detailed section of megasequence III 50 TEXTURE -alaJr* - L grading, especially near the margins of the layer. Twenty-five per cent of the sandstones are reverse graded at the base (Fig. 17). Siltstone areas are laminated and/or cross-stratified. Almost all layers near the base are amalgamated, but mudstone partings became more common upward. Many amalgamated beds show scouring to a small depth (<5 cm). Structures: Sandstone over siltstone contacts usually show disruption or rip-up of the siltstone layer (Fig. 18). Scours are generally of low relief, however some scours filled in by quartz granules or even small sandstone pebbles erode up to 10 cm. The larger scours are less than 15 cm wide. Claystone blocks and pebbles are quite common in the basal sandstone layers and the bottommost sandstone has a 5 cm thick mudstone layer at the top of which are small flame structures. The mudstone layer also contains small areas of fine sand which appear to have been injected from the underlying sandstone. Middle ton and Hampton (197 3) suggest that partial liquefaction of a very fine to fine sandstone may result from loading. Escape of water contained within the pores could have produced the sand "plumes" observed. Broken shells are noted in several layers. Trend: No trend is observed for the sequence of layers recorded at III (Fig. 19), however layer thick nesses do decrease near the top of the outcrop. Inter- 52 Figure 17. Reverse grading and amalgamation in megasequence III at 270 m. Lower sandstone layer reverse graded near base from siltstone to fine-grained sandstone. Amalgamated overlying sandstone displays thin zone of re verse grading. 53 Figure 18. Rip-ups in megasequence III at 265 m. Silty mudstone layer has been broken and bent by fine-grained sandstone. Current movement from left to right. 54 Figure 19. Vertical sequence analysis of mega sequence III. 55 % sand CD x CD: coarse div. L : layers thick, in cm beds of mudstone also become thicker upward. These ob servations indicate that the midfan megasequences are channel fills as suggested by Mutti and Ricci-Lucchi (1972). The facies represented is B2 or even up to A4 in the gravelly sandstones. More that 20 0 m of the overlying section are covered by alluvium and vegetation. One 10 m section was found on the far western bank of the present creek. The se quence consists of "shaly1 ^ interbedded very fine sand stone and mudstone of facies D/G. Sequence IV More than 200 meters of section, most of which is covered, separate the amalgamated gravelly sandstones at III from a similar section, megasequence IVA (Plate 1). At one location between them a short interval of thinly bedded mudstones and very fine-grained sandstone of facies D/G is exposed on the eastern creek bank. A larger section of similar characteristics also occurs on the western bank. These outcrops present evidence that at least one period of interchannel deposition took place between the channels represented in sections III and IVA. Sequence IV begins abruptly with thick beds of coarse sandstone at the base of megasequence IV. Section IV is divided into three subunits which define a thinning and fining upward sequence that records a progressive move from channel deposition (IVA), to near channel (IVB), 57 and then to interchannel mudstones (IVC). The thickness of each unit is approximately 10 m for A, 34 m for B, and 16 m for C. Sequence IVA: Megasequence— Section IVA is approxi mately 10 meters thick and consists of thick beds of coarse amalgamated sandstone of facies B and C. Layers thin and fine upward. Load deformation and the effects of current movement are the dominant structures expressed in these rocks. Grain Size and Bed Characteristics: Hard, thick (10-92 cm) pebbly coarse- to fine-grained brown sandstones abruptly project out of the alluvial cover at 484 meters (Fig. 20). The basal contact is undulose re sulting from compaction of the underlying covered material. The first three layers recorded at section IVA (Fig. 20) are thick (90, 92, 40 cm), amalgamated, facies B2 r coarse sands. Each grades upward to a very fine sand or coarse silt. Tops of each of the three layers show ex tensive development of load forms. Most overlying layers have flat contacts and mudstone partings. Mudstone and sandstone clasts are not common, but are up to 12 cm in diameter. Many areas of convolute and undulose lamina tions are often accentuated by wood and plant fragments, mica and gray mudstone partings. Structures: Load pockets and flame structures were developed along the tops of the basal sandstones. Load pockets containing coarse sand or small pebbles extend 58 Figure 20. Detailed section of megasequence IVA 59 STRUCTURES TEXTURE C O L U M N TEXTURE up to 40 cm into the overlying coarse sand. About 5 meters above the basal sands, convoluted bedding and un dulose laminations are found in a series of fine sands (Fig. 21). Crowell 'et al. (1966) reported that fluc tuating currents were responsible for similar assem blages found in the section above megasequence VII (Pi. 1). Mudstone and sandstone pebbles were also observed as were minor amounts of shell debris. Trend: Basal thick sandstone beds of facies B2 give way upward to fluctuating current deposits of facies C and D (Fig. 22). A complex thinning upward trend is indicated. Increase of mudstone in the overlying sections indicateds withdrawal and filling of the channel. Sequences IVB and IVC: Interchannel— Sandstone content decreases from IVA through IVB and into the fine grained beds of interchannel deposition recorded at IVC. Grain Size, Bed Characteristics and Structures: Layers in Section IVB are composed of medium thick (11- 40 cm), medium- and fine-grained sandstone intervals overlain by thicker massive mudstones (28-50 cm). Within this combination, couplets accumulating to thicknesses of over 50 cm are common. The mudstones in this suite do not appear to be composed of separate mud layers, but were probably deposited as one unit. Sandstones are poorly graded or massive and usually display a fairly sharp 62 Figure 21. Convoluted layer in megasequence IVA at 490 m. 63 Figure 22. Vertical sequence analysis of mega sequence IVA. 64 % sand sjiun | C * < 17- CD 1 4 x 100 100 CD:coarse div. L- layers thick, in cm transition to mudstone. Laminations and cross-strati fication are rarely found. Structures are also very in frequent, although one 3 cm deep scour is located at the base of a 29 cm sandstone. Section IVC is more typical of previously measured interchannel assemblages. Thin, massive fine sandstone or siltstone intervals usually show fair to good develop ment of B or C Bouma structures. BCE and CE turbidites are most commonly observed. Overlying gray and brown mudstone layers accumulated to thicknesses of 5 to 30 cm. Contacts are flat and sharp. One 3 cm fine sandstone was observed to pinch-out in the section measured. Trend: The thickness of the featureless AE couplets of section IVB imply channel or near channel deposition. Judging by their stratigraphic position above the channel fill sequence, however, has led to their interpretation as facies E levee deposits. The finer grained deposits above are facies D and G interchannel accumulations. Sequence IV provides and excellent example of a channel fill suite emplaced during lateral channel mi gration. Layers of the channel deposit recorded near the base of section IVA gradually thin and fine upward. In this case, channel agradation is due to lateral mi gration, and levee deposits formed along the migrated channel are deposited above the fill sequence. Finer interchannel deposits reflect an even more distant area 66 of accumulation from the active channel. Sequence V The fifth sequence begins abruptly at 541 meters (Plate 1). The sequence has been subdivided into two units, VA, which is the megasequence, and VB, which is an interchannel suite. Gradual channel filling, which has characterized previous sequences, was not displayed in VA but instead a rapid abandonment was indicated. The megasequence was 22 m thick; the interchannel suite was 64 meters. Sequence VA: Megasequence— Medium thick layers of silty medium-grained sandstone of the fifth megasequence abruptly overlie the fine sedimentation units of the interchannel environment at 541 meters. The basal con tact is shown in Figure 23. The section measured at 553 m, depicted in Figure 24, gives a good summary of structures and layer properties observed in this mega sequence . Grain, Size and Bed Characteristics: Tan to light brown, medium- to fine-grained sandstones with only thin mudstone partings are the dominant make-up of the layers in section VA. Bed thicknesses are quite variable, from 4 to over 100 cm, but most are from 30 to 60 cm. Thicke coarser sandstones usually have minor scour and/or load irregularities (Fig. 24) along the base. Most other con tacts are flat. Mudstones are massive to laminated mix- Figure 23. Basal sandstone layers, facies , of megasequence V abruptly overlying interchannel mudstones at 541 m. 68 Figure 24. Detailed section of megasequence VA 69 DIR. COLOR STRUCTURES TEXTURE ______“ °»° V " * C O L U M N STRUCTURES TEXTURE C O L U M N tures of gray and red brown muds and sometimes contain laminae of silt or very fine sand. Structures: Relatively few scour depressions were found and most are shallow and at the base of coarse sandstones. Pebbles of any type are much less commonly found than in other megasequences and wood laminae and shells are also notably absent. Trend: Although no particular trend is discernable in the CD and L diagrams (Fig. 25), the sequence is still interpreted as a channel fill suite. The basal sandstones of the sequence and the measured section at VA are generally amalgamated sandstones of facies B2 . Facies C and D turbidites, with their thin mudstone partings, are more commonly deposited near the top of the mega sequence . Sequence VB: Interchannel--Fine grained accumulations abruptly overlie the thicker sandstone units of VA and form a 64 meter thick interchannel suite between mega sequences. The five meters of section underlying the thick sandstones of VIA record a resurge in sand content. Grain Size, Bed Characteristics and Structures: The lowest fine grained layers are similar to previous suites of interchannel deposition. Thin zones of fine- or very fine-grained sandstones containing C and D Bouma divisions are overlain by thicker accumulations of mudstone. The top-most 5 m, however, has thicker and more frequent 72 Figure 25. Vertical sequence analysis of mega sequence VA. 73 thick, in cm nc. of units %sandl accumulations of sandstone, many of which have well developed traction features. Parallel and wavy lamina tions, cross-stratification, climbing ripples, and con volute bedding are present in this section (Figs. 26 and 27) . Trend: The increase in sandstone near the top of the interchannel deposits probably resulted from the incur sion of a new channel into the area. The abundant forma tion of the structures, especially climbing ripples and wavy laminations, indicate a relatively rapid rate of sedimentation. The convolute bedding observed may have formed due to this rapid influx (McKee, et al., 1962). Sequence V differs from previous sequences in its abrupt withdrawal from channel sedimentation. This rapid abandonment may have been a result of avulsion at some up-fan position. The suite of interchannel de posits overlying the channel fill also differs from most sequence in the development of a sandier section prior to the emplacement of a megasequence. Sequence VI Sequence VI is the thickest, coarsest, most debris laden megasequence exposed in the midfan assemblage. In a fashion suggestive of previous sequences, VI began abruptly with the deposition of thick, pebbly, coarse grained sandstones. Unlike the others, however, the pebbly sandstones are succeeded by thick beds of pebbly 75 Figure 26. Wavy laminations in lower fine grained sandstone layer and convo luted laminae in upper sandstone layer. Photograph taken in inter channel deposits 7 meters below megasequence VIA. 76 Figure 27. Rapid rate of sedimentation indicated by wavy laminations and climbing rip ples (A) and numerous cross-stratifi cation and laminations (B) in inter channel deposits at 624 m. 77 granule conglomerate. The conglomerates are overlain by thinner layers of coarse-grained sandstone and con glomerate . Sequence VI can be divided into four units, three of which are part of megasequence VI. Sequence VIA, the base of the megasequence, is a suite of thick amalgamated layers of pebbly sandstone. This unit is approximately 18 m thick. VIB, the granule conglomerate, is 17 m thick. Sequence VIC forms a complex series of layers of conglo merate, sandstone, and mudstone, 36+ meters thick. The section above the sequence VIC was hidden by alluvium. However, VID, a 20 meter outcrop below megasequence VII, indicates a return to interchannel deposition occurred. The location of each sequence is shown in Plate 1. Sequence VIA: Megasequence--The basal unit of se quence VI forms a suite of thick, friable silty sandstone layers, 18 meters thick. The contact with the underlying fine-grained deposits of sequence VB is sharp and moder ately flat. Scour and compaction have not greatly altered this underlying strata. The transition to the overlying pebbly conglomerate is not as abrupt. Grain Size and Bed Characteristics: Thick amalga mated layers of coarse- to very fine-grained sandstones are common in sequence VIA. Most layers show poor develop ment of coarse tail grading. Layer thicknesses are similar to those of the overlying conglomerates, ranging from 78 thick to very thick (50-150 cm). Some layers have thin developments of parallel laminations, or cross-strati fication in the very fine sandstone at the top of the bed. Sandstones are silty and not as well consolidated as previous megasequence sandstones. Structures: Shallow (<5 cm) scour and load depres sions were noted, however lenses of siltstone may indicate greater erosion. Pebbles of mudstone, less than 2 cm in diameter are uncommon. Trend: No trend in layer thickness was noted for these facies pebble sandstones. Sequence VIB: Megasequence— The conglomerate layers forming the second unit of the megasequence are the coarsest beds deposited in the midfan region. They form a sequence of graded and amalgamated layers which accumu lated to approximately 17 m. CD and L diagrams fail to define any trend in the conglomerate layers. Section VIB (Fig. 28) was taken near the center of the conglomerate unit. Grain Size and Bed Characteristics: The conglomerate layers are essentially poorly sorted sandstones which con tain more than 30 per cent clasts of granule and small pebbles of quartz and chert (Fig. 29). Larger pebbles of sandstone and mudstone, up to 8 cm in diameter, con tribute less than 5 per cent of the layers. Layers are medium thick to very thick (11 to 145 cm) Fig. 30), many 79 Figure 28. Detailed section of megasequence VIB. 80 0 00 CN C O L U M N DIR. COLOR !> s TF P n S IC 1 - T It JF* e s jh N a T A u E) o. ITURE O* 2 » W 1 o * 0 o o 0° -655 i 1 | \ i \ \ i i I 1 -654 1 i • —' K J W _L-fc D* -653 9 t sdofrii M 9 e o 0 D o 9 • o - ? « ¥ * ; * J } s a — -- --— ------ - -652 f I 9 " i X . :- d r ll , ! 1 I STRUCTURES DIR. COLOR TEXTURE C O L U M N Figure 29. Scouring conglomerate layer at 645 m. Note granule and small pebbles in sandstone matrix. Top to right. 83 Figure 30. Thick layers of granule conglomerate at 654 m. Figure 29 is a close-up of scour above meter stick. Top to right. 84 Figure 31. Vertical sequence analysis of mega sequence VIB. 100 %sand 700 650- 7.8 C-D VIB 600- GO 01 19- 100 CD 19- 100 1m C D - coarse div, L - layers thick, in cm of which grade upward to a fine-grained sandstone. Thin layers of sandstone, siltstone and mudstone separate at least 25 per cent of the conglomerates. These fine layers sometimes contain parallel or cross-stratified zones. Structures: The base of most conglomerate layers show evidence of scour. Relief of up to 25 cm was noted at conglomerate over mudstone or siltstone contacts. These latter layers contain very thin laminae of wood and plant fragments. A lense of cross-stratified sandstone incorporated into the matrix of one conglomerate layer testifies to the violent erosion connected with the em placement of these layers. Trend: The CD and L diagrams for section VIB show a complicated variation in bed thickness (Fig. 31). The conglomerate layers are interpreted as facies A2 , organized conglomerates, and are separated by relatively thin se quences of facies C and D turbidites. Sequence VIC: Megasequence--The third and final unit of the sixth megasequence is quite variable in both thickness and composition. Layers of pebble conglomerate alternate with pebbly sandstones, massive mudstone, and thin, laminated, and cross-stratified fine sands and silts. The series is composed of both the best and the worst sorted sandstones. Many contain large amounts of broken shell in addition to pebbles. Two sections were measured 87 in unit VIC, neither of which shows any well-defined trend. The only observation that can be made is that the layers of VIC are all thinner than the thickest beds of VIA or VIB. The top of the unit has been covered by recent stream alluvium so that information about the overlying section is sketchy. Grain Size and Bed Characteristics: Section VIC1, located 15 meters above VIB, is depicted in Figure 32. Bed thickness of coarse divisions average between 15 to 40 cm; mudstones between 3 and 15 cm. At least half of the sandstones are graded, from coarse or medium sand up into silt or mud. Sandstone, shale, and mudstone pebbles are very common in section VI, occurring in almost half of the layers. Most pebbles are less than 3 cm, but are up to 10 cm in diameter in the pebble conglomerate layers (Fig. 33). Contacts are almost always sharp and flat. Parallel laminations and cross-stratification are displayed in thin layers of fine-grained sandstone. Section VIC2 was taken 15 meters above VICl, (Fig. 34). This section shows bed thicknesses to be quite similar to that of VICl, however mudstone intervals are fewer and thicker. Amalgamation, seen in 50 percent of the layers, may suggest a more turbulent environment. Pebbles are not nearly as common as below, however mudballs up to 18 cm in diameter are found in a pebbly sandstone near the base of the measured section. Thin interbedded units 88 Figure 32. Detailed section of megasequence VICl 89 32a i C O L U M N DIR. COLOR !> 5 6 TS * 1 tii c H T X JF ' i PE i s H N ja T A w E > C L [T o» UR « * E 1u 1 fid 19 vs W . . . . . . . . . . ^ > • .j:* o o » ~ Y * -IT o < • ' e * 6 7 2 ? - & a j | § | 4 ® l i j T ^ w 9 \ - t m m w b ■ i H i - < | P < fe* ' m n \ M t J * * M jW ff ' + • * « 3 » ■ > — . ♦ -671 H fl H m / / p i i h M ^ '~1 r 9 t _ jfcr B S D if - 9 S# & ■ ^ 1 v*? . .vjjp ! _ i «n 1 * r -670 kR Ml --it / ■ V s i * ? $ Ml* - 9 » i i f t j j 1 ^ { 1 x * f t 4 *'h 1 • * 0 « O O O o . 0 e . . O ~ f 1 F & * C J W * » ' ,-W \ -6 6 9 9 IP ® M I i 1 I H i | T i i p i ■ i i .1 . STRUCTURES TEXTURE C O L U M N -6 7 5 1 -6 7 4 ✓ ^ Figure 33. Pebble conglomerate at 673 m; note poorly developed grading and large clast imbrication. Top to right, current top to bottom. Slump shown in Figure 35 to extreme right. 92 Figure 34. Detailed section of megasequence VIC2 93 DIR. COLORS STRUCTURES TEXTURE C O L U M N DIR. COLOR STRUCTURES TEXTURE C O L U M N 34b -6 9 0 2 30 of facies D turbidites, show well-developed ABE and ABCE sequences (Fig. 35). One crossbed developed in fine sand stone near the top of the section has a wavelength 30 cm long. Structures: Shallow depressions due to scours were noted at a few contacts including a 6 cm deep scour and fill at 670.4 m. The discontinuous mudstone at the top of the conglomerate layer at 674 m is also an indication of the erosional power of these proximal turbidites. How ever, the most unique structure in section VICl is the slump at 674 meters (Fig. 36). The slump is a 20 cm wide medium-grained sandstone "nose" surrounded by thin conformable layers of mudstone and sandstone. The whole assemblage has moved into a graded pebbly sandstone. Only minor scours were found at the base of coarser sandstones in VIC2. Pebbles and shells are not as common as in section VICl. However, reverse grading was observed at a number of locations. Trend: No trend could be interpreted from the CD and L diagrams for either C section (Fig. 37). The facies composing this seuqence are primarily facies C, proximal turbidites and B2 to A4 organized pebbly sandstones. Organized sandstones are indicated by coarse tail grading, which is shown by most conglomerate unites. Long axis imbrication is also suggested by the larger clasts (Fig. 33). 96 Figure 35. Thin ABCE turbidite at 685 m. 97 Figure 36. Medium-grained into sandstone top to bottom, sandstone slump emplaced layer. Current sense top of section to right. 98 Figure 37. Vertical sequence of megasequence VICl and VIC2. 99 100 % land 700 5.0 VIC2 650 600 VICl CDr coarse div. l~ layers thick, in cm 11 11 J . 1m 26- 23- 100 Megasequence VI is the coarsest channel fill sequence observed at Santa Paula Creek. The sequence exposed begins with layers of pebbly sandstone of facies B2 or which accumulate to a thickness of 18 meters. Gravels are introduced in the overlying layers, and thick accumu lations of pebbly granule conglomerates were deposited. The coarsening upward may be the result of lateral migra tion of the channel or possibly just due to transport of coarser material. Whatever the reason, bed thicknesses are relatively the same as those in the underlying sand stones. Almost as abruptly as the thick beds of con glomerate began, they end. Thinner layers, most under 50 cm, of graded sandstone, conglomerate, and mudstone compose the remainder of the exposed megasequence. Amal gamation, shells, and pebbles are all very common in the final sequence, the top of which is hidden beneath allu vium . The next outcrop of section, sequence VID, is a series of thin bedded clays and sands stratigraphically almost 160 meters higher (Fig. 38). The section was measured at 882 meters, just 4 meters below the base of megasequence VII, the final thick sandstone accumulation. Sequence VID records a period of interchannel deposition which took place between the channel deposition episodes. Sequence VII The seventh and last megasequence is at the juncture 101 Figure 38. Thin distal turbidites and mudstones of facies D/G, 5 meters below mega sequence VII. Top of section to left. 102 of Santa Paula and Mudd Creeks. This is the section that has received the most attention by other geologists. Crowell et aJ. (1966) measured 200 meters of section south ward, up section, from the concrete dam which is found at this location. The 42 meters of thick-bedded sandstone which was measured at the base of their section , plus another 30 meters north of the dam, combine for a total of 72 meters for the thickness of the final megasequence (Plate 1). This megasequence, as in the previous ones, shows an overall decline in the sandstone layer thickness toward the top of the megasequence. A thick and some times complicated assemblage of interchannel fine-grained layers overlying the megasequence marks the transition into the upper fan assemblage. Sequence VII has been subdivided into only two units: the megasequence, VIIA, which is 72 meters thick, and VIIB, the interchannel deposits. The latter unit forms a compli cated sequence primarily composed of fine-grained layers of facies D. However, thicker sandstone layers periodi cally disrupt the monotonous suite. The inner fan-midfan boundary has been arbitrarily picked as the top of the medium thick sandstones measured at 1221 meters. The interchannel suite of VIIB is essentially the trasition zone between the midfan and inner fan. Sequence VIIA: Megasequence— Megasequence VIIA forms the second thickest sandstone assemblage found in 103 Santa Paula Creek. It is approximately 72 meters thick and is composed of thick to very thick layers of pebbly sandstone. The layer thicknesses show an overall thinning upward trend, as in most of the previous megasequences. Load forms, convolutions and scour were commonly recorded. The suite was deposited abruptly over a thin bedded se quence of CDE turbidites of facies D/G (Fig. 39). No sections were measured by the author in the seventh sequence until 1129 m (Plate 1). The descriptions that follow will come primarily from the published litera ture concerning this sequence, particularly from the work of Crowell et_ aT. (1966). Those descriptions, plus field observations by the author, have facilitated a logical interpretation of this sequence. Grain Size and Bed Characteristics: Amalgamated, very thick (>2 m) layers of conglomeratic sandstone form the base of sequence VIIA (Fig. 40). Only infrequent medium thick zones of siltstone were observed separating layers. Crowell et al. (1966) reported layer thicknesses of between 0.5 and 2 m for the sandstones in the upper 42 meters of the megasequence (Fig. 41). Half of the layers are poorly sorted conglomeratic sandstones. Pebbles and cobbles of sandstone, shale, or mudstone are usually less than 10 cm in diameter but are up to 50 cm in length. Poorly sorted coarse to fine sandstone layers compose 40 per cent of the megasequence. Thin to 104 Figure 39. Abrupt basal contact of megasequence VII at 886 m. Very thick, conglomera tic sandstone layers of megasequence VII overlying interchannel mudstones. Top to left; ladder rungs approximately 30 cm apart for scale. 105 medium thick zones of mudstone and siltstone compose the remainder of the sequence. Structures: Load structures are commonly developed, especially at pebble sandstone over mudstone contacts. Crowell et al. (1966) reported that most were small struc tures, 3-5 cm wide and less than 2-3 cm deep. Small loads were noted at 940 m and larger structures up to 20 cm deep were reported at 932 meters. Scour is indicated by amal gamated sandstones as well as channels. Some channels are up to 30 cm deep (Crowell et_ al., 1966). Convolutions and flame structures are often developed in siltstones or mudstones, and rip-up mudstone clasts are often incor porated into the base of a scouring sandstone. A mudstone clast 50 cm long was found near the base of a pebbly sand stone at 921 m and imbricated mudstone slabs near 930 m (Crowell et al., 1966). Trend: A thinning upward trend was noted for the sandstone layers forming megasequence VII. The suite is composed of 72 meters of thick interbedded layers of facies E>2 , A^, and A2 ; amalgamated sandstones, pebbly sandstones and organized conglomerates, respectively. Thinner layers of facies C and D were deposited near the top of the megasequence. Sequence VIIB: Interchannel Transition Zone--The suite of thick layers of coarse sandstone of megasequence VII quickly change into fine grained interchannel deposits 106 Figure 40. Base of conglomeratic sandstone layer shown in Figure 39. 107 Figure 41. Photographs of thick sandstones of megasequence VII forming eastern creek bank at Mudd Creek juncture. Dam to extreme left; top of section to right; section shown approximately 35 meters thick. i —i o 00 at 958 m. The section described by Crowell _et al. (1966) was primarily centered around these interchannel distal turbidites. Unlike the previous monotonous inter channel sections however, sequence VIIB is periodically interrupted by coarser clastic deposits. This transport of coarser material into the section is probably the result of fluctuating currents associated with the transi tion from midfan to inner fan deposition. Grain Size and Bed Thickness: About 75 per cent of sequence VIIB is composed of thin fine-grained layers of facies D turbidites and G mudstones. Crowell ert al. (1966) reported that sandstones were fine- to medium- grained in layers averaging between 5-10 cm. Many of these display small-scale cross-stratification. Inter bedded mudstone, siltstone and claystone layers are esti mated to average between 1 or 2 cm (Crowell e_t al_. , 1966). The remaining 25 percent is composed of thicker layers of facies D, C, and infrequently B sandstones. The latter facies are concentrated in primarily two areas, at 1125 m and 1214 m (Plate 1). A measured section from the latter area is depicted in Figure 42. Medium thick sandstone intervals (10-50 cm) recorded at each location are commonly separated by equally thick mudstones. Grain size usually is from medium to fine sand, although 10 per cent of the layers at 1214 contains small pebbles. Mudstone clasts are common in disturbed beds around 1125 m 109 Figure 42. Detailed section at 1214 m. 110 TEXTURE COLOR STRUCTURES ____ TEXTURE n ~ - C O L U M N DIR. 42 b 1221 1220 1219 w 1218 (Crowell et_ a.1. , 1966). A section measured at 1124 m contains angular and rounded mudstone clasts, some of which are up to 15 cm long. Crowell et al. (1966) indicated that discontinuous conglomerate and pebble sandstone layers or lenses are infrequently interbedded with finer material between 1030 m and 1080 m. The lenses rarely exceed 10 cm in thickness. Two pebble mudstones, each less than 65 cm thick, were also reported from this same zone. Structures: Contacts in the interchannel area are nearly planar and relief rarely exceeds 3 cm (Crowell et al., 1966). Exceptions to this are found beneath the coarser sand layers in the areas previously mentioned. A 10 cm deep channel is located at the base of a medium sand at 1217 m. Other structures which were reported by Crowell jet al. (1966) are similar to those recorded in previous interchannel areas. They include graded bedding, cross-stratification, climbing ripples, convolute laminations, deformed bedding, shells, charcoal or car bonized fragments, and layers of woody material. Dis turbed beds and pebble clasts are particularly well dis played in the layers around sections 1125 m and 1214 m. Trend: The trend displayed by sequence VII is the same as observed in previous sequences. Very thick layers of conglomeratic sandstone of facies A give way to pebbly and amalgamated sandstones of facies B and 113 C, This thick bedded coarse sequence is immediately overlain by fine-grained thin bedded facies D and G layers. A fairly rapid rate of abandonment is indicated by the abrupt change. However, unlike previous sequences, interchannel layers of VIIB are infrequently interlaminated with conglomerate and pebble sandstone. These latter layers or lenses indicate vigorous current activity, probably connected with nearby channels. Two sandstone zones containing medium thick to thick layers of medium- grained to pebbly sandstone may represent aborted small channels or the edge of larger channels. Deposition of Midfan Assemblage Seven thick sandstone and conglomerate units, mega sequences, have been identified in the Lower and Middle Pico Formation exposed at Santa Paula Creek. Each unit is separated from the succeeding megasequence by a thin bedded mudstone and sandstone assemblage. Megasequences are commonly combinations of facies A, conglomerate and pebble sandstone; facies B, amalgamated coarse sandstones, and facies C, proximal turbidites. No special sequence of these facies was noted, however layers of coarser facies are usually found below less coarse. Many beds show poor to good development of coarse tail grading. Two or more coarse layers are often joined or amalgamated due to erosion or nondeposition of a mud stone interval. Three types of amalgamated junctions were 114 Figure 43. Three types of amalgamated junctions observed in the present study (modi fied from Walker, 1966). 115 observed, each of which is illustrated in Figure 43 (after Walker, 1966). 1. The sandstone junction is marked by an abrupt change in grain size. 2. Two sandstone layers are separated by a row of mudstone flakes which are probably a remnant of a mudstone layer. 3. The junction between the sandstone layers is perfectly annealed and identification of the separate layers is only possible by laterally tracing them into two distinct layers. In many situations where thick sandstones are sepa rated by thin mudstone partings, the contact is undula- tory due to compaction and/or erosion of the mudstone. Relief developed at such contacts is usually less than 4 cm. The megasequences are separated from each other by tens or hundreds of meters of interbedded mudstone, silt- stone and sandstone. These latter sequences are usually composed of thin, less than 10 cm layers of facies D, distal turbidites. Directly above some megasequences, facies E, overbank deposits are identified, and very thin, less than 1 cm thick, red brown pelagic mudstones of facies G are sometimes developed at the top of gray mudstones. The thin sandstones, medium- to very fine grained, are commonly graded and often show development of 117 BCE, CE, CDE Bouma sequences. Recent articles, particularly Mutti and Ricci-Lucchi (1972), Walker and Mutti (1973), and Ricci-Lucchi (1975), have indicated that sequences such as those described are characteristic of deep-sea fan environments. Two areas are particularly favorable as possible sites of accumu lations: 1 ) channels of the inner and middle fan, and 2 ) depositional lobes of the outer non-channelized fan (Ricci-Lucchi, 1975). Abrupt basal contacts, concentra tion of coarse layers near the base, and an overall thin ning and fining upward trend has identified the lenti cular megasequences are channel fills, rather than deposi- tional lobes. In keeping with the terminology suggested by Mutti and Ricci-Lucchi (1972), the channels are mid fan deposits. The thick sequences of mudstone and thin sandstone turbidites separating individual megasequences are interchannel deposits. Emplacement of the thick sandstone and conglomerate layers are assumed to be by one or more of the sediment gravity flow types described by Middleton and Hampton (1973). The common occurrence of grading, the large amount of silt in the matrix, and the lack of fluid formed structures such as dish, convolute bedding, and fluid escape pipes, suggest deposition was largely a combination of turbulence and grain interaction. The interchannel deposits, on the other hand, suggest deposition from low density turbulent flows, resulting from overbanking of 118 concentrated channel flow. Foraminif era. collected by Nat'land indicate that the depth of water near Santa Paula Creek decreased during deposition of the megasequences (Fig, 2). Megasequence I was probably emplaced at bathyal depths of over 1 2 0 0 m (4000 ft). A continued high rate of sedimentation coupled with a slower rate of basin subsidence had decreased the water depths to upper bathyal by lower Wheelerian time (Natland, 1957). Water depths between 600 and 450 m (2000-1500 ft) are indicated for deposition of megasequence VII . INNER FAN ASSOCIATION The sequence of layers of the second member, the inner fan association, accumulated to a total thickness of approximately 500 meters (PI. 1). No definite lower boun dary can be established due to the nature of the tran sitional inner-mid fan zone. Mudstone is the dominant lithology represented in the inner fan region and occurs as both separate layers and in thin units interbedded with thin sandstones and siltstones (Fig. 44), The suite formed is quite similar to the interchannel deposits recognized in member one; the major difference is the lack of thick channel sequences. This deficiency in channels has been interpreted as a result of the greater confine ment of channels in the inner fan environment, 119 Figure 44. Thin, distal turbidite and medium thick mudstone layers of inner fan section at 1600 m. Top to right; graduate student Tom Hartnett for scale. 120 Figure 45. Detailed section of inner fan at 1329 m. 121 C O L U M N Dl R. COLOR !> 5 TS i L I 51 c H TUB t t f (E 5 N N J O t T E > ■°la» U * * ■ C T » UR * « * £ * w r g ■ 1 t 1 a « q j I P - r 9 " r n J m m m s — g— J K M T K -1328 ■ ■ l A n * * * . S . : •« fl .5 1 i -----*— — 1 l U H I T «= > «=== r_ ■ M W - H 1 “1327 0 I s i | ----- r ae~. ... ..... * ■ ; 1 L - * . ! i"' «JK ------ ------------- -— g 81 — S m - o » - 1326 i 9 Wfi ei i 1 1 | 1 ! i 1 ! Figure 46. Detailed section of inner fan at 1527 m 123 STRUCTURES inn TEXTURE C O L U M N 1528 124 i Figure 47. Detailed section of inner fan at 1577 m. 125 STRUCTURES TEXTURE C O L U M N The sand/shale ratio throughout most of this mudstone member fluctuates around 0.07. An example of section with this ratio, measured at 1329 m, is depicted in Figure 45. Some intervals are substantially sandier. The structures and bed thicknesses typically developed in these areas are depicted in Figures 46 and 47. These examples are from measured sections at 1527 m and 1577 m. Sand/shale ratios are 0.13 and 0.31 respectively. Grain Size, Bed Characteristics and Structures Sandstones and Siltstones--Sandy intervals are usually less than 4 cm thick, though in some cases they were ob served to reach up to 25 cm. Amalgamation of sandy inter vals was almost never observed, and contacts are normally flat and sharp. Sedimentary structures which are typi cally associated with the thin sand intervals are those displayed by the "distal” turbidite of facies D. Thin laminations B and/or D, are most commonly developed. Laminations, the result of interbedding of very thin laminae of buff silt and gray mud, are also quite common. Small scale cross-stratification, C, is sometimes found in association with parallel laminations but most often is developed alone. Typically, cross-stratification is only one or two cross strata thick, less than 1 cm, and often merges into massive sandstone. Black organic debris and thin gray clay partings sometimes accentuate 127 the parallel laminations and cross-stratification. Small mudstone pebbles derived from interbedded layers and discontinuous layers indicate at least some scouring during deposition of the thin turbidites. Pebbles seldom exceed 5 mm, however, in one 4 cm coarse silt layer at 1577 m a pebble of mudstone 7 cm in length extends upward into the overlying mudstone, Mudstones--Mudstone accumulations are much greater in thickness than the associated sandstones, Thicknesses between 10 and 30 cm are most common, though the range extends from 1 to over 100 cm. The thickest mudstone units, those greater than 50 cm, are almost exclusively limited to the section immediately below the slope channel facies, member 3, Mudstone intervals are sometimes composed of separate layers of turbiditic and pelagic muds. The turbiditic muds, normally gray to chocolate brown in color, represent the settled-out fines of turbidite flows. The associated sand couplet may or may not be present. The pelagic mud, a normal marine clay, is usually red brown to brown in color. The turbiditic, gray mudstone is always much more abundant than the pelagic mud. Accumulations of pelagic mud are somewhat thicker and more frequent in member 2 than in either member 1 or 3. Thicknesses of pelagic clay of up to 4 cm were noted at a section mea sured at 1640 m. Often the pelagic clays are found 128 forming separate, though not necessarily sharp, layers within a massive gray mudstone. In areas where turbidites are composed of the normal sand/shale couplet, the pelagic muds usually form as a diffuse layer at the top of the gray mudstone. Overthrust and bent thin sandstone zones found in association with down-slope abrupt changes in mudstone thickness indicate that slumping or sliding was an active process in the inner fan association. Slides (slumps?) were noted in two, 1474 and 1624 m, of the sections mea sured in member 2. Both involved only one sandstone layer and sliding was confined within a 45 cm thick region. The sequence of mudstone layers approximately 100 m thick, which formed the section underlying the slope channel assemblage has a development of unusually thick layers. Most layers exceed 40 cm, some of which are up to 150 cm. Layering of structures is indistinguishable in these mottled massive dark gray to dark brown mudstones. The layers could be slump deposits or bioturbated layers, both of which are found in the overlying member 3. A pebble-like weathering pattern, such as observed in many of the overlying mudstones, suggests lack of internal st ructuring. Two small faults, with 3 cm offsets, were also found at 1474 m. One fault crosses four beds, a combined thick ness of 43 cm, before ending in a thick mudstone. 129 Shell fragments were found localized along bedding contacts rather infrequently in the inner fan assemblage. An unusually heavy concentration, however, is found at 1354 m (Fig. 48). Fragments of cranium and vertebrae of a Gray whale (Balaenopteridae) were collected at 1502 m. A complete description may be found in Appendix B. Channels--Two thick accumulations of sandstone inter rupted the monotonous mudstone member. The first pebbly sandstone was at 1396 meters; the second was at 1565 meters (PI. 1) . The first sandstone abruptly and conformably overlay a thick sequence of facies D layers (Fig. 49). The basal sandstone bed is 110 cm thick, slightly graded, and dis plays a 1 cm thick zone of reverse grading at the base. The medium sandstone grades upward to a clayey coarse siltstone. Angular mud pebbles, less than 4 cm in length, form a thin zone 40 cm above the base of the bed. The topmost 3 cm of clayey silt contains organic rich clay layers, broken and convoluted due to scouring and loading by the overlying sand layer (Fig. 50). The medium sand stone, 138 cm thick, grades upward to a very fine sand stone. Mud pebbles, localized along the base, do not exceed 1 cm in diameter. A silty clay rip-up, 50 cm in length, extends diagonally across the exposed sandstone body. Mud balls, up to 30 cm in diameter, were found in the fine sand near the top of the bed. The sand is over- lain by a 10 cm interval of undulating laminations of 130 Figure 48. Shell concentrations along mudstone bedding planes at 1354 m; note orien tation of long shell dimension parallel to bedding plane. Current sense from left to right. 131 gure 49. Detailed section of small channel at 1396 m. 132 STRUCTURES TEXTURE C O L U M N 1399 1398 fine sand and organic rich silt and clay (Fig. 50). Two thin turbidites, BCE and ABCDE, overlie the laminated sandstones. Eight AE turbidites preceed the deposition of a thick basal conglomerate layer in the second thick sandstone (Fig. 51). The eight turbidites accumulated to 155 cm, 66 of which were partially eroded by the 90 cm thick conglomerate layer. The conglomerate is composed of rounded sandstone and shale clasts up to 25 cm in dia meter, dispersed in a sand matrix. The conglomerate is overlain by 24 cm of massive gray fine sand punctuated by two thin clay layers. Overlying the massive sand are three layers of graded medium- or coarse-grained sand with gravel zones at the base of each. The three layers are 67, 39, and 6 cm thick, respectively (Fig. 51). Interchannel, D facies, deposits overlie the 6 cm layer. Both channel sequences display thinning upward trends on CD and L diagrams (Fig. 52). Deposition of Inner Fan Assemblage The mudstone section is characterized by two facies, D and G. Facies D distal turbidites typically display well-developed basal cut-out sequences of BCE, CDE, and CE. Thin, very fine- to fine-grained, massive or laminated sandstones are often found at the base of thick mudstones. The lack of Bouma sequence structures probably reflects lack of sufficient current for their development. These 134 Figure 50. A. Scour and load disruption of the top of basal sandstone layer at 1397 m. B. Undulose laminations and clay-rich zones at 1398 m. Laminae are accen tuated by black organics. 135 Figure 51. Detailed section of small channel at 1565 m. 136 STRUCTURES TEXTURE C O L U M N Figure 52. Vertical sequence analysis of small channels at 139C m and 1565 m. 138 139 0 100 % sand 1600- 2.0 1565 T550- 2.8 1400 1396 2 CD= coarse div. c L= layers «*• o o’ c thick, in cm CD 100 12- 100 1 m CD 5 a. 100 100 layers represent sedimentation on the distal edges of tur bidity currents (Walker, 1966) and have been interpreted as facies D. Red brown mudstone, or pelagic shale, is extensively developed in this section. Individual layers, some up to 4 cm thick, are often found interbedded with the more voluminous gray muds. The greater amount of red brown clay indicates longer periods of accumulation and/or greater preservation. Both cases suggest quiet areas of deposition, removed from the influence of concentrated turbidite flows. The two thick sandstone sequences which interrupt the quiet water accumulations resemble the thicker mega sequences. The abrupt transition to thick beds, concen tration of coarse material near the base, and the occur rence of more than one coarse layer, suggests that these too are channel accumulations. Similar small channels were reported in slope deposits by Ingersoll, et aJL (1977) and in the midfan by Piper, et al. (1978). The lack of more frequent and deeper channels undoubtedly indicates a change from the laterally migrating channel environment prevalent in the midfan association. A significantly reduced rate of sedimentation is indicated, if basin sub sidence is held constant, in the Santa Paula area, accord ing to Natland’s (1951, 1957) foraminiferal studies. Depth of deposition for member 2 is from 600 to 270 m (2000- 140 900 ft). However, continued rapid basin filling in the west suggests that transport of sediment was through the inner fan region. The lack of channels, in this case, reflects greater confinement of a few channels as has been observed in recent deep-sea fan systems (Hess and Normark, 1976; Nelson and Kulm, 1973). Confinement within the channel walls, however, was not so great as to prevent the deposition of over 500 meters of overbank deposits at Santa Paula Creek. SLOPE CHANNEL ASSEMBLAGE The third fan facies association forms the topmost 65.2 meters of the section measured at Santa Paula Creek An abrupt transition from the underlying mudstones is marked by the deposition of a 43 cm sandy cobble conglo merate. The following 65,2 meters contain the coarsest and most poorly sorted layers measured in the Plio-Pleis tocene sequence. These layers, the conglomerates and pebble mudstones, are predominately matrix supported debris flows. A suite of sandstone and mudstone layers, developed between the coarse-grained layers, form recog nizable units of facies D, C, E, and . A listing of the contribution of each form of mass flow is given in Table 3. The stratigraphic location of this member, between midfan channels and shallow water sandstones, suggests TABLE 3 DEPOSITS OF THE SLOPE CHANNEL ASSEMBLAGE DEPOSIT FACIES THICKNESS (M) PERCENTAGE Conglomerates A, F 7.58 12 Pebble Mudstones F 13.30 20 Sandstones and Pebble Sandstones B 3. 70 6 Thick Mudstones Bouma E 4.05 6 Turbidity D,C,E 36. 57 56 TOTAL 65.20 100 142 inner fan or slope deposition. The mixed assemblage of facies, abrupt basal contact, overall fining upward trend, and abundant pebble mudstone layers suggest channel fill in an area of measurable slope, The sequence of layers which constitute member 3 undoubtedly record a period of upper fan or lower slope channel deposition. Conglomerate and Pebble Mudstones Layers in member three containing clasts coarser than 2 mm have been separated into two main categories, con glomerate and pebble mudstone, Classification followed the scheme presented by Folk (1974) and was based on visual estimations of the relative percentages of gravel, sand, and mud. Layers containing greater than 30 percent gravel attain the textural class of conglomerate. Clasts are composed primarily of shale and sandstone, most of which are rounded, although some are broken. Matrix supported clasts, some showing imbrication, and the com paction of the mudstone matrix beneath some cobbles indi cates that the matrix and clasts were deposited as a unit (Gig. 53), Characteristics of individual conglomerate and pebble mudstone layers may be found in Table 4„ De tailed description of most of the mass flows will follow. Six conglomerate layers out of the ten identified are located in the basal 10,5 meters of member 3 (Fig. 54). Conglomerate layers 1 and 2 were sandy cobble conglomerates both of which showed a poorly developed upward decrease 143 in clast size. Layer 1 is matrix supported; layer 2 is grain supported. The remaining four conglomerates are clayey sandy pebble conglomerates. The fourth, conglo merate 4, displays coarse tail grading. Areas of both conglomerate 3 and 4 show clustering of clasts (Fig. 55). In these zones, the cobbles and pebble form a grain supported framework with sand and mud situated in the intersticies. In areas of less clustering, the matrix supports the clasts. Layers 5 and 6 are almost wholly grain supported and clasts range up into the bounder size. Situated atop conglomerates 1, 2, 4, and 5 are sizable thicknesses of massive gray mudstone (Fig. 54). These mudstones constitute 44 per cent of the basal 10.5 m. The contact between the mudstone and conglomerate is usually flat and sharp. Conglomerate over mudstone con tacts are normally undulose due to compaction and/or scouring by the conglomerate. These massive mudstones probably represent deposition from a silt and clay satu rated suspension. Approximately 6 meters of interbedded sand, silt, and mud separate conglomerate layer 6 from the base of conglmerate 7. Descriptions of these more thinly bedded sequences can be found in the following section. Conglomerate 7 is a muddy sandy cobble conglomerate containing some of the largest boulders observed, up to 50 cm in length. No grading was observed, however the 144 Figure 53. Rounded sandstone cobble supported in massive mudstone. Cleavage in mud stone matrix follows the surface of the clast, indicating simple compac- t i on , 145 TABLE 4 CONGLOMERATES AND PEBBLE MUDSTONES OF SLOPE CHANNEL ASSEMBLAGE A. CONGLOMERATES NO. BASE LOCATION THICKNESS (CM) FACIES ^CLASS IFICATION --------- CLAST SUPPORT O rgan ization 1 1729.7 43 A2 sG matrix c.t.g. 2 1732.4 64 a2 sG grain c.t.g. 3 1733.4 121 F msG mat /gm c.g.t.? 4 1734.7 94 F msG mat /gm c.g.t.? 5 1737.3 170 A1 msG grain none 6 1739.6 81 A1 msG grain none 7 1745.7 71 F msG mat /gm imbri. 8 1758.2 49 F mG mat/grn none 9 1777.6 27 F mG matrix c.t.g. 10 1783.3 38 F msG matrix none 1. Folk(1974) classification; G = conglomerate, m = mud, s = sand 2. c.t.g. = clast grading, imbri. = imbrication of large clasts 146 TABLE 4 (cont.) B. PEBBLE MUDSTONES NO. BASE LOCATION THICKNESS (CM) FACIES LARGEST CLAST (CM) O rganization 1 1732.3 12 F 4 thr. 2 1746.9 54 F 30 thr. 3 1748.0 110 F 40 base, imbri. 4 1749.4 160 F 10 thr. 5 1751.3 110 F 9 base 6 1761.6 60 F 8 thr. 7 1765.7 45 F 23 base 8 1766.9 64 F 8 thr. 9 1771.5 78 F 20 thr. 10 1774.9 216 F 90 mid. 11 1779.4 144 F 15 thr. 12 1787.5 130 F 25 base 13 1791.3 142 F 15 base 1. thr. = pebbles throughout matrix, base = pebbles concentrated near base, imbri. = imbrication of large clasts, mid. = pebbles con centrated in the central section of the layer. 147 Figure 54. Detailed section of slope channel assemblage. 148 54a i STRUCTURES TEXTURE C O L U M N MEM®! -1732 -1730 ' 4r^> i -1729 54 b C O L U M N DIR. COLOR }> s & Tf P 1 11 S 1C H TUJIE i s N N jQ TEXTURE •? a - » 2 < • « -1736 ivI 'J a ° • • • » o H B 9 ^ O o q ° 0 05 ) cr> ^ f e “ 1735 ■ r* I — 1 1* / ° ' O o " • - t " ^ § ) * s s < S ( < r / J i k * y ' ‘P*j 5 ^ •“1734 g 1 F f r^ fe .1 **». 4 .^ f / •*- V i i * v N <' * -, ' V i, * ^ / p -1 -.li V V i < ? < > - 4 & 3 W " I f i M ^ J , i | f ’ j jl* O f c > O P o * © o O ° ° ° o J-"! v'V^' / \ ^ j -1733 t — / ^ i i ' 2 * } r * n \ ^ 4 S \ T -» o ^ o — - I * L l • i ' :i> ' ■ y " V j 150 54c C O L U M N DIR. COLOR ! > s E TF iH sue 5 !H r i.» s s 5 ] m m -Y a THXTUR? w W » z « * M o i r ■ m J . 6 S J ■■ 3 r j § | -J J T 7 ---------- T 1 ^ ---v mfo I M O £ p 8 ^ -1740 Pi 1 1 ! S f I i m i § y§ 9 B j j . y * w f i & < 2 WM I m W M O -1739— — 1 f -1738 » 5*» > .’ / * . *, 1 # ' >V* , ^ * “ H ■ " * » - „* * ' j | r ^ " g 9 i I I | - m % i i ‘ . — — — . 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COLOR 5 TFIL c H TUF ft I E h JQ T J 3 u E > O L CT 9 UR «• E « V p M ■ $ j s 4 f s i m m W t i -1768 1 1 JW m 1 E B W 1 IT .. . . m J [ --r 3 | w ° % D o m ° W l o < » > 5 5 1 1 m / -1 767 1 — • * s ~ - * * - | y / / , f t .*** t * m I M i -1766 3 [ |l fe a r 9 •^p J j i i f i 2 i o y " gal H 1 / ,r& fviSH ;;-il 2ocy m / fjM U0- 210 / V ’ M — i 1 1 r* f2 . & w > “1765 9 ■ — .1 1 158 54k C O L U M N DIR COLOR !> s ■B TS $ tu 5] c H T 1 U 5 E 1 S H N -Q r _Q E> a. IT o» URE m m w 1 0 3 ° ^ i ^ s ____ o -1772 1 < * i t m p & i t t N 1 * o <3 b ■ | —ism % — 1 77'! ■ A i l l | S I ) ! f 1 i i i I ( s 1 1 1 ! ! i ‘ I ;i n 1 w m s * ^ 3 i I i \ i -1770 m m m m -n h ^ j u ^ |m n U N 1 m mm « ! " j l [ I HW i% " i f f m -1769 £ 5 K l E J m i s Wr * • 3 r 1 1 t ..._ Ba m ! < r :~ “ t m I i i i . DIR. COLOR TEXTURE aJa» 2 m C O L U M N DIR. COLOR STRUCTURES TEXTURE C O L U M N >7- 7 9- 161 DIR. COLOR STRUCTURES MgfflilHftiim TEXTURE AS o-U 2 - C O L U M N DIR. COLOR S T R U C T U .lt kr!tol<<u?!4ic: C XTUi?£ C O L U M N 1787 163 DIR. COLOR STRUCTURES MBKHilHKiiiHlN TEXTURE C O L U M N 1790 folds COLUMN DIR. ICOLOR STRUCTURES IWHMiWN TEXTURE TOP OF ME ASURED SECTION covered -1794 Figure 55. Conglomerate layer 3 at 1733 m; note clast clustering. Top is to right. 166 largest clasts, especially platy shaped ones near the base, display a rough upcurrent imbrication (Fig. 56), This orientation is also seen along the base of pebbly mudstone 3. This type of imbrication has been reported by others (Davies and Walker, 1974; Walker, 1975) in "deep water turbidite-likeM conglomerate beds. Pebble mudstones 2, 3, 4, and 5 fill most of the 6 meters between 1747 and 1753 m . Pebble mudstones 2 and 3 contain boulder size clasts between 20 and 30 cm in length, though most clasts are smaller. Clasts are distributed throughout layer 2 , although the size of the gray hard mud pebbles declines near the top. Layers 3 and 5 con tain most of their large indurated clasts in a narrow zone near the base of the bed, some of which are imbricated (Fig. 57). Mudstone 4 contains less than 5 percent soft mud pebbles, very few of which exceed 10 cm. Muddy pebble conglomerate 8 at 1758 m contains rounded quartzite pebbles up to 7 cm in diameter. One large broken boulder, 40 cm in length, was also found. Blocks of friable sandstone, some up to 12 cm thick, have slumped into the upper 20 cm of the layer. A small fault splits a slump block of massive sandstone and extends upward into the overlying mudstone, a distance of 20 cm, A 2 cm thick clayey silt in the fault contains thin laminations paralleling the fault, indicating injection of the clayey mixture. The overlying sandy series of beds also contains 167 Figure 56. Imbrication of large clasts near cen ter of conglomerate 7 at 1746 m. Top is to right; current sense from top to bottom. 168 Figure 57. Pebble mudstones 2 and 3 at 1747 m. Clasts in mudstone 2, left of meter stick, are distributed throughout layer. Clasts in mudstone 3 are concentrated near base and platy large clasts show up-current imbrication. Top to right, current top to bottom. 169 two small faults, with offsets of less than 3 cm (Fig. 58), and pebble mudstone 6 is transversed by an injection dike of siltstone (Fig. 54), The siltstone filler is laminated and identical to the underlying siltstone layer. Sequences of thin turbidites and thicker massive pebble sandstones separate the remaining conglomerate and pebble mudstone layers. Most of the clasts in mudstones 7, 12, and 13 are located near the base of the layer. Pebbles and cobbles in 8 , 9, and 11 are randomly distri buted throughout the layer, Individual clasts in all of the mudstones are generally less than 8 cm in diameter. Pebble mudstone 10, however, contains many clasts which exceed 13 cm. Boulders, some between 60 and 90 cm in length, are scattered throughout the center of the layer. Some of the clasts are broken, and individual pieces can be found in close proximity. The conglomeratic central section is situated between two relatively clast-free mudstone regions. Three fold axes measured near the top of mudstone 12 indicate slumping oblique to the general current flow. Thick Sands and Turbidites The largest percentage of member 3 is composed of medium thick sandstone layers of facies B and thinner layers of a mixture of facies C, D, and E (Table 5). Sequences of these four facies, from 24 to 588 thick, separate individual conglomerate or pebble mudstone layers. 170 Figure 58. Small faults at 1761 m with offsets of less than 3 cm. 171 ■■D TABLE 5 INTERBEDDED SANDSTONE AND MUDSTONE OF SLOPE CHANNEL ASSEMBLAGE BASE POSITION T (CM) SAND SHALE % SAND FACIES 1731.6 70 2.6 70 D 1740.4 528 2.3 64 D,C-E,B 1746.4 50 1 . 2 46 D 1747.5 41 -- — E or D 1749.1 32 .8 28 D 1751.0 24 — 100 A3 1752.3 588 1.9 56 D, C-E 1758.7 286 1.9 42 D, C 1762.2 353 3.8 61 C , D , B 1766.2 65 1.8 65 C 1767.5 397 .84 39 D, C 1772.3 258 1.5 50 D 1777.0 56 1.0 46 D 1777.9 153 3.0 68 C-E , D 1780.8 250 1.7 58 D,C 1783.7 97 1.2 53 C,D 1784.9 109 — 100 B2 >A4 1786.0 157 2 . 0 59 D 1788.9 244 5.5 77 D ,B2 1792.7 102 .21 19 D 172 Figure 59. Disrupted mudstone layers at 1743 m. Mudstone layers at top and bottom have burrows developed in underlying sand stone. Center of photo is 50-50 mud- stone-sandstone layer; underlying graded sandstone layer has two zones of mud clast concentrations. Current sense from left-to-right. 173 Thin, fine- to very fine-grained sandstones are either massive or contain good to poorly developed B, C, and/or D structures. At least 50 per cent of these layers are graded and most have a thin capping of gray mudstone. Brown pelagic mud is found in less than 25 per cent of the layers. Medium- to coarse-grained sandstones and pebble sandstones generally occur in poorly graded thicker layers, some of which are amalgamated. Typically, se quences are predominately composed of layers of facies D turbidites with one or two thicker sandstone layers of facies C or B. Contacts, in most cases, are sharp and flat. Low relief scours, less than 1 cm, in mudstones and small mud clasts near the base of several sandstones demon strate the erosive power of the currents that deposited the thin turbidites. Angular mudstone chunks in three separate layers at 1743 m point to more violent current drag. Entire mudstone layers have been disrupted. How ever, the angular clasts could not have been transported far before deposition took place, An alternative inter pretation of these "missing” layers is that the mudstones were broken up by burrowing organisms (Fig, 59). Small depressions, resulting from differential loading, were only infrequently observed. Bioturbation structures were noted at several loca tions in member 3. The section above conglomerate 6 , 174 1743 m, shows two exceptional areas of burrows (Fig. 60). Individual burrows extend as much as 17 cm into the sand stone layer. A horizontal burrow, 4 cm long and filled with fine sandstone, is located near the top of a gray mudstone at 1765 m. Shallow, less than 1 cm depressions along the top of the mudstone may be a result of surface digging by organisms (Reineck and Singh, 1975, pg. 141). Identical mud surface depressions are again associated with horizontal burrows in a mudstone at 1772 m. Similar circular as well as elliptical horizontal burrows were found with a near vertical burrow in a mudstone at 1769 m. Transported near shore and terrestrial debris is much more common in this slope canyon assemblage than in any other previous section (Fig. 54). Whole and broken shells (pelecy?) are strewn along many sandstone contacts (Fig. 61). Shells arc predominanLly oriented with the long dimension parallel to the contact. Wood and plant fragments are also often oriented in this manner. Thin organic laminae sometimes accentuate laminations or cross-stratification in turbidite sequences. Hard, glossy, and punky pebble size accumulations of coal and charcoal are found in a number of beds (Fig. 54). Undoubtedly, the charcoal and coal have been transported from a terres trial source. Deposition of Slope Channel The sequence of deposits exposed in member 3 are a 175 Figure 60. Close-up of burrows at base of Figure 59; note scour and mud pebbles at base of overlying sandstone. 176 Figure 61. Shells strewn along base of thick sandstone at 1760 m. Wood and shell lamina in laminations near top of layer. 177 reflection of a series of jumbled modes of deposition, of which the end members are turbidity currents and debris flows. Grain support is provided by turbulence in the turbidity currents (Middleton and Hampton, 1973). However, grain support is by matrix strength in the muddy conglo merates and pebble mudstones (Middleton and Hampton, 1973). The turbidity currents show some development of basal cut-out and thin massive sandstone under mudstone sequences which are interpeted as facies D. These layers represent deposition by weak, low concentration turbidity currents on distal edges of more powerful flows. The more central sections of these flows would be expected to carry the coarser elastics, and as suggested by Middleton and Hampton (1973), would deposit layers of proximal turbi dites or even resedimented conglomerate, i.e., facies C and A. Segregation of grains is indicated by the grading and imbrication observed in some conglomerates. The mud stone clasts, pockets of sand, contorted mudstone, slide blocks, and folds observed in various pebble mudstones suggest that these are slump structures, the debris flow of Middleton and Hampton (1973). The stratigraphic position of member three, between the deep-sea turbidites of the lower and middle Pliocene and the shallow water deposits of the upper Pleistocene, suggests an inner fan to slope environment. Associations of diverse subaqueous deposits such as those observed at 178 Santa Paula have been reported in submarine canyons on the upper fan or slope by Nelson and Kulm (1973). Evidence of channelization is suggested by (1 ) the abrupt, though not necessarily erosional, contact between conglomerate layer 1 and the underlying mudstone; (2 ) the concentration of 70 percent of the conglomerate layers in the lowest quarter of the sequence; and (3) the thinning-up trend displayed by the conglomerate layers (Fig. 62). The frequency of pebble mudstones also decreases upward, although a thickening upward trend was observed for indivi dual layers (Fig. 62). The overall fining upward sequence and the common occurrence of pebble mudstones in the top half of the sequence suggest that this slope channel was being filled by gravity slumps or slides. The fold axes observed in mudstone 12 indicate that at least that slump was to the south, oblique to the south-westward flow suggested by cross-stratification measurements. Perhaps some of the pebble mudstones were deposited as semicoherent slumps from northeast-southwest oriented channel walls. However, massive mudstone matricies, which in 6 cases feature pebble imbrication or basal clast concentrations, indi cating organization was by flow, suggest that most were deposited in the form of a debris flow. A slumping mecha nism such as suggested by Crowell (1957) seems justified for the conglomerate-over-mudstone sequences observed near the base. Figure 62. A. Thickness of conglomerate layers decreased upward. B. Pebble mudstones thickened upward. 180 Layer No. Ln. O- 3 \yr O o L a y e r N o . >< o • O •o M W > ' IcSl PALEODIRECTIONS Paleocurrents Measurements of small scale cross-stratification are summarized in Table 6 and Figure 63. In the field, the plunge of the current structure was measured and then note made of the sense of movement perpendicular to the struc ture. Pitch of the current direction was computed and the pre-tilting direction found by rotating this line around the strike line into the horizontal. Many of the cross-stratification structures observed were so small or faint that correct measurement of current direction was impossible. In the current rose (Fig. 63), paleo- currents have been separated into the environment from which the measurement was made, channel or interchannel. Paleocurrent measurements taken in channel environ ments indicate flow was to the southwest, which implies northeast to southwest transport of sands and gravels. Natland and Kuenen's suggested northern source for the conglomerate lenses is supported by these few observa tions. Interchannel paleodirections are more variable but indicate a westerly flow. Current directions taken by Crowell et aJL. (1966) in the interchannel mudstones above megasequence VII showed a similar spread, but also implied westward flow. Both channel and interchannel paleocurrent directions imply a northeast to southwest 182 TABLE 6 PALEOCURRENT AND SLUMP MEASUREMENTS A. PALEOCURRENT LOCATION DEPOSIT DIRECTION,° 76 Interchannel 260 76 Interchannel 250 255 Interchannel 270 255 Interchannel 240 255 Interchannel 250 255 Interchannel 220 556 Channel 240 625 Interchannel 260 689 Channel 220 689 Channel 230 886 Interchannel 310 886 Interchannel 290 1525 Interchannel 190 1525 Interchannel 270 1526 Interchannel 2 2 0 1529 Interchannel 230 1765 Channel 210 1765 Channel 200 1765 Channel 210 183 TABLE 6 (con.) B, SLUMP LOCATION FOLD AXIAL DIRECTION DIRECTION 1788 1 0°; , S40W 130 ; 310 1788 2 CO 0 , N84W 190;010 1788 3 H- o 0 , S77W 170;350 184 Figure 63. Rose diagram of paleocurrents and slump folds. 185 N ■INTERCHANNEL -*-w -C H A N N E L S LU M P O C C U R R E N C E S W S 186 channel orientation, Paleocurrents from channels are lateral from the basin margin toward the trough axis, while interchannel deposits indicate variable flow associated with flow laterally away from the channels (Ingersoll et al. , 1977),. Slumps Three axial orientations were taken from folds located in the top of pebble mudstone 12. The field measurements were plotted on a stereographic projection and rotated to pretilt orientation (Table 6 ). Directions perpendicular to the axes indicate slumping was southerly, or obliquely downstream for a northeast to southwest oriented channel. DISCUSSION The section measured at Santa Paula Creek provides an example of a prograding deep-sea fan suite (Ricci- Lucchi, 1975) developed during an interval of rapid deposition in the Ventura Basin. The progression of fan facies associations represented in this sequence is midfan- inner fan-slope. The measured sequence is overlain by a series of conformable layers of sandstone and shale which culminate in non-marine deposits of the Saugus Formation. Underlying the measured sequence are conglo merate, sandstone, and shale layers of the Repetto Forma- 187 tion. The Repetto is known to represent deep-water sedimentation. From the interpretation of the section measured, it is predicted that the Repetto sediments were deposited in depositional lobes in an outer fan setting. The midfan facies association at Santa Paula Creek is characterized by coarse-grained, channelized sandstone sequences which are separated by tens or hundreds of meters of fine-grained interchannel deposits. The thick development of these latter assemblages precludes develop ment of the extensive sand sheets of Normarks' (1970) suprafan and therefore suggests that outerfan and midfan associations are quite distinct (Ingersoll et. _al. , 1977). A comparison between the megasequences measured at Santa Paula Creek and midfan channel fill sequences measured by Ricci-Lucchi (1975) in turbidite formations of the northern Apennines is presented in Table 7. Large scale relationships are very similar; megasequences of from 2 to 1 0 Ts of meters in thickness are separated by 1 0 rs of meters of fine-grained interchannel deposits. The greater separation between megasequence III and IV, and between VI and VII, may have resulted from lack of transportable coarse elastics. The most obvious reason, however, would be that midfan channels were actively transporting material in another area of the fan. There is a marked difference in the average thickness 188 TABLE 7 COMPARATIVE STUDY OF MIDFAN CHANNEL FILL SEQUENCE APENNINES SANTA PAULA SEPARATION OF MEGASEQUENCE 10-80 m 40-210 m (?) AVERAGE LAYER THICKNESS 500-40 cm 56-25 cm THICKNESS OF MEGASEQUENCE 2.5-62.0 m 2.0-72+ m SAND/SHALE 1.5->50 3.6->50 189 of layers forming individual megasequences. The thinner layers of grain size at Santa Paula suggest that transport of sediment to the deep-sea fan was by smaller and/or more frequent gravity flows. Narrow shelf margins and/or a direct deltaic feed of sediment to the head of a canyon could conceivably satisfy these conditions. A similar combination of transport to a deep-sea fan was reported by Stanley and Unrug (1972). The interchannel sequence developed above megase quence VII has been interpreted as a midfan-inner fan transition zone. Ingersoll et, aT. (1977) reported that overbank deposits of the inner fan were often observed to be transitional to midfan interchannel deposits near an area of channel widening and braiding. Presumably, the juxtaposed conglomerate lenses and thin distal tur- bidite sequences may reflect just such a transition. The tentatively identified aborted small channels would tend to support this conclusion. Another transition zone which deserves some attention is the inner fan-slope channel zone. The featureless, pebble-free, thick mudstones which preceded the slope channel assemblage differed from the inner fan mudstones by their noticeable lack of thin distal turbidites. The pebble-like weathering pattern of these mudstones suggested there was little in the way of stratification in the layers. This implies either rapid deposition or disruption of 190 initial structuring. Bioturbation was suggested, however no structures or burrows were noted. It is therefore suggested that these mudstones were either emplaced rapidly from overbank flows from a large channel, or as mud slumps. The former is considered the more likely since the thicker sequences are often observed to inter bedded with thinner mudstone zones overlying distal turbidit es. Flow features observed in half of the conglomerates and pebble mudstones in the slope channel have indicated that emplacement of these deposits was by debris flow. Variations in mudstone and pebble content were noted between flows. The sequence may reflect lateral or longi tudinal variations from a single debris flow, or alterna tively, may indicate variation in the initial source material. Longitudinal evolution of a slide or slump would proceed in a manner as described by Middleton and Hampton (1973). Thus, deposition of a conglomerate or pebble mudstone layer would primarily reflect the amount of water incorporated and degree of reworking of the slump. On the other hand, the observed sequence may reflect lateral variations of one flow. Slope canyons in present day comparable slope environments have been reported to be on the order of 1 to 3 km in width (Nelson and Kulm, 1973). Active channels have been noted to meander within 191 confining canyon walls (Nelson and Kulm, 1973).; Concei vably, coarser layers, such as the conglomerates, may represent closer proximity to an active channel. Pebble mudstones would form closer to margins. Lateral variations such as this were observed by Piper et aJL. (1978), however they felt that the trend reflected "multiple episodes of flow" rather than segregation within a single flow. They also suggested lateral variations in source material, such as from a delta distributary, as a possible explanation for the observed lateral change. A rough depositional rate for the Pliocene series at Santa Paula Creek may be computed for comparison with other deep-sea fan environments. The Pliocene series in the Santa Paula area is 3700 m (12,000 ft) thick (Jennings and Troxel, 1954). Assuming a 20 per cent compaction for the variable sequence (Weller, 1959) gives an average rate of sedimentation of 100 cm/100 0 years. (3700m + 3700 m(.20))/4.5 x 106 years = 100 cm/1000 years. This rate is identical to that estimated by Mutti, Nilsen and Ricci-Lucchi (1976) for outer fan depo sits in an Apennine turbidite basin. A 200 cm /1000 yr rate has been estimated as an overal rate of sedimentation in the present Alaskan trench axis (von Huene, Kulm, et al. 1971). The paleogeographic picture of the Plio-Pleistocene environment that emerges from this study is that of a 192 rapidly prograding deep-sea fan. Rivers, draining the mountains to the north, supplied sediments to a narrow basin margin. Deltaic fans, possibly similar to the one reported by Baldwin (1959) in the Fillmore area, funneled coarse elastics to a northeast-southwest oriented submarine canyon. The elastics were transported down the canyon be debris flow and with increasing fluidity dispersed on the fan through a system of shallow midfan channels. The coarsest materials were generally confined to the channels while fine sands and muds accumulated to great thicknesses between channels. CONCLUSION The PIio-Pleistocene sequence measured at Santa Paula Creek records deposition in a deep-sea fan system. Three fan facies associations were represented m the measured stratigraphic section. The midfan association, 12 21 meters thick, was composed of seven channel fill sequences. Thick accumulations of interchannel deposits separated individual channel fill sequences. The inner fan association was composed of 509 meters of overbank deposits. A 65 meter thick sequence of slope channel deposits abruptly overlaid the inner fan sequence. 193 ACKNOWLEDGMENTS I am grateful to Dr. D, Gorsline for suggesting the field area and for his helpful comments throughout this work. I wish to thank Dr. R. Bourrouilh for his advice and persistence in the field investigation, and Drs. W. Easton and R. Merriam for kindly reviewing earlier versions of the manuscript. My special thanks goes to my many friends who have assisted me in all phases of my thesis work. 194 REFERENCES Baldwin, E. J., 1959, Pliocene turbidity current deposits in Ventura Basin, California: unpub. M.S. Thesis, Univ. of South. Calif. Los Angeles, Barker, C. T., 1976, Pliocene geology and the Santa Paula oil field area: Pacific Section, Am. Assoc. Petroleum Geologists and Coast Geol. Soc. Spring Field Trip Guidebook, 18 p. Crowell, J. C., R. A. Hope, J. E. Kahle, A. T. Orenshine and R. H. Sams, 1966, Deep-water sedimentary struc tures, Pliocene Pico Formation, Santa Paula Creek, Ventura Basin, California: Calif. Div. Mines., Spec. Rept. 89, 40 p. Crowell, J, C., 1957, Origin of pebbly mudstones: Geol. Soc. America Bull., v. 6 8 , p. 993-1010. Davies, I. C. and R*. G. Walker, 1974, Transport and depo sition of resedimented conglomerates: the Cap Enrage Formation, Cambro-Ordovician, Gaspe, Quebec: Jour. Sed. Petrology, v. 44, p. 1200-1216. Folk, R. L., 1974, Petrology of Sedimentary Rocks: Hemphill Publ. Co., Texas, 182 p. Hess, G. and W. R. Normark, 1976, Holocene sedimentation history of major fan valleys of the Monterey fan: Marine Geol., v. 22, p. 233-251. Ingersoll, R. V., E. I. Rich and W. R. Dickinson, 1977, Great Valley sequence, Sacramento Valley: Cordilleran Section, Geol. Soc. America Field Trip Guidebook, 72 p. Jennings, C. W. and B. W. Troxel, 1954, Ventura basin: Calif. Div. Mines Bull. 170, v. 2 guide no. 2, 63 p. McKee, E. D., M. A. Reynolds and C. H. Baker, 1962, Laboratory studies on deformation in unconsolidated sediment: U. S. Geol. Survey Prof. Papers 450-D, D151-D155. 195 Middleton, G. V. and M. A. Hampton, 1973, Sediment gravity flows: mechanics of flow and deposition Ln Middle ton, G. V., and A. H. Bouma, (eds.) Turbidites and deep water sedimentation, S.E.P.M. Pacific Coast Section, Los Angeles, p. 1-38. Mutti, E., T. H. Nilsen and F. Ricci-Lucchi, 1976, Sedi- mentology of outer fan depositional lobes of upper Miocene-Pliocene Laga Formation, east-central Italy. (Abst;.): Amer. Assoc. Petroleum Geologists Bull. , v. 60, p. 701. Mutti, E. and F. Ricci-Lucchi, 1972, Le torbiditi dell' Appennino settentrionale: Introduzione all'analisi de facies: Soc. Geol. Ital. Mem., v. 11, p. 161-199. Natland, M. L., 1957, Paleoecology of west coast Tertiary sediments: In. Ladd, H.S., (ed. ) Turbidity currents and the transportation of coarse sediment into deep water: S.E.P.M. Spec. Publ. 2, p. 76-107. Nelson, C. H. and L. D. Kulm, 1973, Submarine fans and deep-sea channels: In. Middleton, G. V., and A. H. Bouma, (eds.) Turbidites and deep water sedimentation: S.E.P.M. Pacific Coast Section, Los Angeles, p. 39-78. Normark, W. R., 1970, Growth patterns of deep sea fans: Am. Assoc. Petroleum Geologists Bull., v. 54, p. 2170-2195. Piper, D. J. W., A. G. Panagos and G. G. Pe, 1978, Con glomeratic Miocene flysch, western Greece. Jour. Sed. Petrology, v. 48, p. 117-126. Reineck, H. E. and I. B. Singh, 1973, Depositional sedi mentary environments: Springer-Verlag, New York, 439 p. Ricci-Lucchi, F., 1975, Depositional cycles in two turbi- dite formations of northern Apennines (Italy): Jour. Sed. Petrology, v. 45, p. 3-43. Stanley, D. J. and R. Unrug, 1972, Submarine channel deposits, fluxoturbidites, and other indicators of slope and base-of-slope environments in modern and ancient marine basins: Ln Rigby, J. K., and W. K. Hamblin (eds.) Recognition of ancient sedimentary environments: S. E. P. M. Spec. Pub. 16, p. 287-340. von Huene, R. E., L. D. Kulm, et slI,, 1971, Deep-Sea drilling project Leg 18: Geotimes, v. 16, p. 12-15. 196 Walker, R. G., 1975, Generalized facies models for resedi- mented conglomerates of turbidite association: Geol. Soc. America Bull., v. 86, p. 737-748. Walker, R. G., 1966, Shale Grit and Grindslow Shales: transition from turbidite to shallow water sediments in the Upper Carboniferous of northern England: Jour. Sed. Petrology, v. 36, p. 90-114. Walker, R. G. and E. Mutti, 1973, Turbidite facies and facies associations: In Middleton, G. V. and A. H. Bouma, (eds.) Turbidites and deep water sedimentation: S.E.P.M. Pacific Coast Section, Los Angeles, p. 119- 159. Weller, J. M., 1959, Compaction of sediments: Am. Assoc. Petroleum Geologists Bull., v. 43, p. 273-310. 197 APPENDIX A CHARACTERISTICS OF MEASURED SECTIONS All sections measured at Santa Paula Creek are listed in the following section and are identified on Plate 1, the stratigraphic column. For each section, the following data are specified: 1. Section location, identifed as base of measured section; 2. Thickness measured in meters; 3. Sandstone percentage; 4. Sand/shale ratio; 5. Component facies (see Table 1), in order of decreasing frequence. SAND SECTION T(M) %SS SHALE FACIES 0 9.1 61 3.6 C D 74.2 3.0 35 0.6 D E 103.1 1.6 24 0.5 D G 175.1 2,7 71 28.8 C B 213.1 3.5 90 39. 9 B 226.1 0.6 38 2 . 3 E D 232.7 1.5 11 0.1 D G 254 . 2 1.4 40 0.7 D E 260.6 3.9 94 >50. 0 B A , D, C 484 .1 8.1 70 5.0 B C 510.0 2.4 24 0.4 E D 538.0 3.3 14 0.2 D G 552 . 7 9.0 69 5.2 B C, D 582 . 2 1.9 22 0.3 D G 623 . 9 1.1 26 0.6 D 651.4 7.8 86 15. 0 A B , C , D 668.8 6.5 72 4.2 C B , D , A 198 APPENDIX A (cont. ) SAND SECTION T(M) %SS SHALE FACIES 685.4 5.1 68 4.6 B C, D 885.3 1.1 15 0.3 D G 1121.6 1.3 59 1.9 C D 1151.9 2.5 17 0.2 D G 1182.7 3.2 38 0.9 D C, G 1214.1 7.2 34 0.7 D C,G 1325.8 3.0 6 <0.1 D G 1351.3 3.1 26 0.4 D G 1294.9 1.0 6 <0.1 D G 1395.9 2.8 94 32.8 B D 1398.7 2.0 20 0.3 D G 1443.0 2.8 7 <0.1 D G 1470.3 4.1 7 <0.1 D G 1500.5 1.8 7 <0.1 D G 1510.4 5.0 18 0.2 D G 1523.6 4.0 22 0.3 D G 1541.7 3.1 9 0.1 D G 1560.3 3.4 10 0.1 D G 1563.7 1.6 52 0.1 E 1565.3 2.0 99 <50.0 A B 1567.3 0.9 19 0.3 D G 1573.8 11.1 10 0.1 D G 1623.0 3.3 1 <<0.1 G 1638.3 5.7 1 <<0.1 G D 1663.8 7.0 <1 <<0.1 ? 1684.0 1.9 1 <<0.1 D ? 1708.7 1.6 8 0.1 D G 1726.7 68.2 — — ALL 199 APPENDIX B CLASS MAMMALIA Linnaeus, 1758 Order CETACEA Brisson, 1762 Suborder MYSTICETI Flower, 1864 Family Balaenoptenidae Gray, 1864 Referred specimen. LACM 115233, left squamosal and part of basicranium, left half of cervical vertebrae, rib fragments, found by Bruce Johnson and Robert Bourrouilh, collected by David H. Spitzer and Lawrence G. Barnes of LACM and Ramon Juncal and Chad Slattery, Museum volunteers on 4 May 1977; field number L.G. Barnes 1794, LACM accession No. A.6439.77.11. Locality. LACM 4285, Santa Paula Creek, Rafferty Ranch, Santa Paula, Ventura County, California. Pico Formation, Pliocene. Description. The zygoma, lie width of the skull when complete may be estimated at 100 to 110 cm. Extrapolation with skull and body proportions of Recent Balaenoptera boreal is (Sei whale) and Megaptera novaeangliae (Humpback whale) gives an estimated total skull length of appro ximately 220 cm, and an original body length of approxi mately 880 cm (= 30 feet +). The skull has a large temporal fossa slightly over hung by the occipital shield, large posteriorly directed occipital condyles, a laterally projecting squamosal, and 200 a nearby flat supraoccipital shield. The zygomatic process of the squamosal is directed anteriorly and is relatively slender and elongate. The glenoid fossa is wide and open on the lateral margin. The postglenoid pro cess is large, flattened, and projects posteroventrally beneath the area of the external auditory meatus. None of the cervical vertebrae are fused. Their centra are not greatly compressed anteroposteriorly. The ribs are not greatly curved, and are squared in cross sectional shape at about midlength on the bone. Discussion. The specimen is a member of the family Balaenopteridae (including modern rorquals). It differs from Balaenidae (right whales and bowheads) by having unfused cervical vertebrae and by not having the glenoid part of the squamosal positioned ventrally on the skull. It differs from Eschrichtiidae by having an elongate zygo matic process of the squamosal. It apparently differs from extinct Cetotheriidae by having the overhung lateral wall of the cranium, a long zygomatic process of the squa mosal, and a longer, flatter, more posteriorly directed postglenoid process. Among the Balaenopteridae, the specimen resembles most closely Recent Megaptera novaeangliae (Humpback whales) and extinct Magaptera miocaena, Kellogg, 1922, and Plesio- cetus in the length of the zygometic process of the squamo sal. The size and position of the postglenoid process of 201 the squamosal, however, is larger than on fossil specimens 0- ^ Plesiocetus (Van Beneden and Gervais, 1868-1879: pi. 16, fig. 17; Barnes, 1973: fig. 4), and is more like Megaptera and Balaenoptera in this regard, In overall morphology, LACM 115233 is closest to the late Miocene humpback whale, Megaptera miocaena, from the Sisquoc Formation at Lompoc and to the ubiquitous fossil Plesiocetus spp. It may lie near the evolutionary divergence of modernized rorquals and Megaptera from primi tive balaenopterids such as Plesiocetus. The only named fossil balaenopterids from the west coast of North America are Megaptera miocaena from the diatomites at Lompoc and "Balaenoptera" ryani (Hanna and McLellan, 1924) from the Monterey Formation at Monterey. Both of these species are late Miocene in age (= 10-12 m. years). Barnes (1976:330) has questioned the generic alloca tion of the latter species. An essentially continuous fossil record of balaenopterids is usually recognized elsewhere in the world, extending back about 10 to 12 million years to late Miocene time (Simpson, 1945:105; Romer, 1966;393; Lipps and Mitchell, 1976:fig. 1), and Barnes (1976) has documented a similar fossil record on the west coast of North America. At the present level of our knowledge of taxonomy and distribution of fossil balaeropterids, no more precise an age determination than latest Miocene or Pliocene may be 202 made based upon the single specimen LACM 115233. Its morphology is, however, consistent with similar fossils of Pliocene age from Cedros Island (Barnes, 1976:table 5) and the San Diego Formation (Barnes, 1973: fig. 4). 203 REFERENCES Barnes, L. G., 1973, Pliocene cetaceans of the San Diego Formation, San Diego, California, p. 37-43. In : A. Ross and R. J. Dowlen (eds.). Studies on the Geology and Geologic Hazards of the Greater San Diego Area, California. San Diego Association of Geolo gists, San Diego, California, 152 p. Barnes, L. G., 1976, Outline of eastern North Pacific fossil cetacean assemblages. Syst. Zool., 25(4): 321-343. Hanna, G Dallas, and Mary E. McLellan, 1924, A new species of whale from the type locality of the Monterey Group. Proc. Calif. Acad. Sci., Ser. 4, 13 (14): 237-241, pis. 5-0. Kellogg, A. Remington, 1922, Description of the Skull of Megaptera miocaena, a fossil humpback whale from the Miocene diatomaceous earth of Lompoc, California. Proc. U.S. Nat. Mus. , 61(14) :1-18. pis. 1-4. Lipps, Jere H., and Mitchell, Edward D., 1976, Trophic model for the adaptive radiations and extinctions of pelagic marine mammals. Paleobiol., 2(2):147-155. Romer, Alfred Sherwood, 1966, Vertebrate Paleontology, 3rd. ed. Univ. Chicago Press, Chicago and London, i-viii + 1-468 pp. Simpson, G. G., 1945, The principles of classification and a classification of mammals. Bull. American Mus. Nat. Hist., 85:i-xvi, 1-350. Van Beneden, P.J., and P. Gervais, 1868-1870, Osteographie des c'etac'es vivants et fossiles. Paris, Arthus Bertrand, 634., pis. 1-64 in atlas. 204 l .: ..,z o..z Oc -'::c "'u z c ... .. ... z z I I I I z c ... 1794.9,-------r--- r:-:-.: . . . . . . . . . . . f:::::: =- = =..:::-_-_-:._ . . - - - - - ~ .-.-: -------- --:- .-.-::- .- .-.. -.'":""'.-. -· - - -- .. . . . ..... . ==- -.::. = =-~ ::::: -.. ' .... ' ... ............ . . .. ;,, .· -· ......... .. Chaotic zone: Interbedded sequence of conglomerates (12%), very thick (30-170 cm); pebble mudstones (20%), very thick (12-216 cm); sandstones and pebble sandstones (6%), medium thick (10-40 cm); massive mudstones (6%), medium to very thick (26-160 cm); thin interbedded sandstones and mudstones (56%). . · ....... -~ ·.·.·• ~ ~:.. 1726.7'--j-~---'-"=:,-----t--------------------------------------------------------------- - -- - 1708.7- - -::.. - - - 1700----i - - - ---- ---- 1684.Gl- - - - -·- - - - - --- -- )bb'3.8- - - - - - - - 1638.3- - - - ~ -- - - - - -- --- - - - lb23.•- -- 1600--<-_- - - -- - - - . ....:... . :- -.: Massive Mudstones: 93% gray and brown mudstone and claystone, massive (to 2.0 m), containing thin (1-3 cm) lenses of buff siltstone; 7% brown to tan siltstone and sandstone, thin (~-3 cm) beds, laminated and cross-stratified. • 573 · 8 -i~·~·~·E·~~--~;~-·2·~.-~:~~t=:~--~C~o~n~g~l~om~e~r~a~t~e~a~n~d~s~a~n~d~s~t~o~n~e~:~300~%~b~r~o~wn:.,~t~h~il:c~k~(f:6~6~c~m:)~,:h~a~red~,:c~o~b~b~l~e~t~o~p~e~b~b~l~e~~c~o~n~g~l~o:m~e~r~a~t~e~,::c~o~a~r~s~e~l~y~g~r~a~d:e~d~t~o~~-- - 1560.3- - -- · ~~ pebbly sandstone, scours; 70% gray to tan s,andstone, thick ( 1. 0 m), graded near base from pebbles to fine sand; _ ----::_._ -=------: ................. .......__!m~i~n~o~r~t~h;;i':n';;;;(:;,-"3~-;:c'im~)-;:m;;;;u;;-d-;-st.,_ofn~e~s"-;-;. ;-;;---;~r;;--.;;--;;~,,-;;-;;:-;:;:-,-;c;;-tc:-.,.,-;=c---,:;c.::c-;:-::--===-::c===o-c---c""~=~~~~,-===--- 1 s41.7_ _ Sandstone and mudstone: 52% tan, thin to medium thick (6 22 cm), fine to medium sandstone, slightly graded, minor ...::::. ..- ---- laminations; 48% gray and minor brown, thin (4-18 cm) mudstone, minor laminations near top. 1523.6- - -~ - - -- - 15104- -~-=-- -- - -- -- -- 1500----<I ---~ :::: --:..o=: - - -- - - -:.. - - - - -- 1470.3- :__· - .. --· ·__:. . .. ·.....:....· ... _ -- 1443.0- Mudstone: 90% gray mudstone and claystone, thin (3-15 cm), massive to fissil; 10% buff to tan fine sandstone, thin ( 5 cm),with laminations and small-scale cross-stratification, some graded. - --- --·- -- - - - - - 1400--;,;:;::~--;-cii'~~~--~~~~~~~~:;-'99;t;o~:;;;;;~;;:~d';~~;;;;~~~:hl::;J;"'(5-:;Q~);"~;;de:d;"~;;-;:;;~;;a.;;--;~~~-;;;:;g,;J~-;;;:;~:;;;;;~;;--~- l394.9 .·.·. · - .. ·...•.... Sandstone: o amalgamated gray sandstone, thick (5-70 cm), graded, reverse graded at base, angular and rounded ---=-~--=_---~ ~~~--....._ mud pebbles 30 cm, rip-up mudstone layer, scours, undulose and parallel laminations and cross-stratification, _-_-_-___ __ .....__~_o_r~g~a_n_i_c_s_;~6_%_,_t_h_1_'n_~(_5_c_m~)~g~r_a_~y_m_u_d_s_t~o_n_e~·------------------------------------------ -- 1351.3-l-~-==~~-=-=i 1325.8- ~ ----- - - - - - ---- - - - --- 1300--1·.-_ Mudstone: 94% gray and brown mudstone, thin (2-25 cm), contains minor thin (1-2 cm) lenses of buff siltstone, minor shell; 6% brown, fine to silty sandstone, thin ( 4 cm), laminated and cross-stratified, minor shell • -- - --==- -- - - . . - -==--- - /---:-:-:-:---~~-:-;-;----:;~:---~~~~~~~~~~-:--:--~~~-;;---;--~-:---;--:-~~~~ . . .--: . .·. ·. ·.. /,.... Mudstone and pebbl;~ sandstone: 66% gray mud stone and siltstone , medium thick (4-40 cm), most graded, parallel -·--'-- .. :=:.:.-~---'---:--/ laminated, minor shell and wood fragments; 34% graded sandstone, medium thick (2-30 cm), pebble to silt, scour 1214.i---::"=--::' =· =-=--· _._"-'-!- -------ia;i'n';'d'i-;:-l~o:':a~d~,,diieiif~o"'rm-;;:a:Ct;;'i;'o':n;;::c;';o~mm;:;;:o:;-n;:--'-' _mS:u:id::;-'p-7e"bC'b'-il'ie~s'.J'SlC'am;"'Oiijn~ai't"C10"' o:Cn::--'' ;;-s:CaO:n;o:'d.,.;l:;eC:n"=s'Oi:Cn"g'O';,,,-..-;-c====.,,------------------- - - - -- _ Mudstone: 80% 2:ray mudstone, thin (3-15 cm); 20% tan very fine to silty sandstone. 1200--- _ -= - Mudstone and sandstone: 62% gray mudstone, thin to massive (4-34 cm), shell and wood fragments; Joto medium to r-;- . . _ ~ ---~ fine sandstone, pebbles ( 3 cm), amalgamated, depression filling, 1182.71'-::·:C· ,:;--~--=-"·-:C--'i·':·-::·-:j::-:0:{".=-------- Mudstone: 83% gray and brown mudstone, thin to massive (3-22 cm), some lamination, tan lenses of siltstone and I-__ =~-.:: pinch-outs of fine ~andstone; 17% tan sandstone to siltstone, thin ( 5 cm), lamination and cross stratification. ·= ---=--=- / Sandstone and mudstone: 50% gray, thick (lb-SO cm) sandstone beds, many disturbed layers with shale clasts, a ~~ -:-..=-~:....:....:--:=· few graded, some with laminations and carbon fragments; 50% mudstone, gray, fairly massive, with laminated silt- ll51.9~.:-- ~- _ - _ __..s'-'t'-'o'-'n~e~a~n~d"-cc'Cl";a;;-y~s~t~on=e~·-:c;-,----,------,---;---,----c-c-o----=----,--=-----c-c-c----o-o--o--oco--o--,---c-o----~-o-------- I -;_.:..-~...:...:.. :-.=_ __.:. v/ / Mudstone: 70% gray siltstone and claystone, fairly massive (to l m), interbedded with laminations and layers, 1121.6- .. -: ·.·_ ,_· •. -_-_,_·:.·:.· . .-_·.·.: / / ./ containing thin (2-3 cm) claystone; 30% thin (1-2 cm). gray sandstone beds, mostly ungraded. Unit to west of fault. ~ /'" Sandstone and mudstone: 55% gray and brO"wn sandstone layers, thin ( 5-20 cm), very fine to very coarse, lamination, ,....//' graded bedding, superposed grading; 45% mudstone and gray siltstone, some graded, convolute lamination,abundant -- ----· -- .....:_ . ..:__. __:.. ._ - :... __ Fo~~minifera. Most of this unit is east of near-vertical fault of unknown slip with a SE strike. ,.//"'" Mudstone and pebbly mudstone: 70% thin, massive, gray, interbedded siltstone anG claystone with lenses of pebble /J/ conglomerate (10%0; pebbly muds tone with shule clasts (20%), discontinuous ,distorted, 1-amin.e.ted, rrcudstone 1-ayers; shells, disturbed bedding~~~bles (10 cml_. ---,--,-~--------,--,--,---------,-----~--~----,-~-- Muds tone and conglomerate: 65% gray siltstone and claystone interbedded with many sandstone and conglomerate beds, many Foraminifera, pelecypod, and carbon fragments; 35% conglomerate and sandstone, (to 20 cm), graded at base but ungraded above. Bas~ with many_~s~h~a~l~e~c~l~a~s~t~s_..a~n~d~g~r~a~v~e~l=-l~e=n=s~e~s~·-occ-cc---c-c---c--o:--c---~o-----~~------ Vi.assive mudstone: 95% gray, laminated, massive mudstone and interbedded, thin ( 2 cm), siltstone and claystone with shell lavers· interbedded with 2-5% thin ( 2 cm) cross-stratified sandstone ln .. ers. VIII ::-: ~:.::-; .~:~~=-<~ Mudstone and shale-clast beds: 80% siltstone with some claystone, gray, thin, and typically interbedded with (20%) graded sandstones containing small shale clasts, carbon fragments, some pebbles, lamination without small scale cross-stratification visible Forams. and shells. Some defonned load pockets. ------- t:· ~.-.: .. 7·::-~-:·.:.+_ 1000--+'-~_-7'77:-~~-~-~ .. +.. .......... _:;:-:.-;--; . .:..-=: ~ -:-; -:""-:=-~ Mud stone and sandstone: 55% gray, thin clays tone and siltstone interbedded with thin sandston.e beds; 40% thin, commonly graded, 50% red to brown, 50% gray sandstone beds; 5% conglomerate at bottom of graded beds. Unit more massive than elsewhere, more resistant to weathering. Contains convolute lamination, disturbed bedding, - - -::'---:...--:.-=. "~ shale clasts and load forms. ~--~_;..._·~.-:(~o:~~~: __ ~- "',,~ M 4 u 0 d%stoned and sandsdtodnef: 60%. g 1 ray, thin, interbeddedd s 1 i1 5 t 0 stoneh~nkd clayst~ne, 1 s 0 ma 2 1 0 1-scale 5 cr 1 o 1 ss-st 1 ratification; ~ san stone gra e ram si t to very coarse san , - cm t ic averaging - cm. ma -sea e cross- ...;. ....:.. _. ~,:;. :...· ~ ~.. , strati£ ication, pull-aparts. disturbed bed.9.0cic.n,.,g~·~c~o~n~v~o~lu=t~e~l~a~m~i~n~a~t~i~o"n"--'-. -------~-~~-------------- , · · .\ Mudstone: 80% interbedded, thin (to 10 cm), gray siltstone and claystone, very thin bedded to laminated, inter- VllA -·.-.::..._.__._ ... ..::.":--· " --'b'-'e'-'d"d"e"'d=t ... o,,_,,l"am"-i"n"'a"t"e°'d",=i"n"t"-e'-r-"b..,e..,d""d"e~d=wi"·"t-'Oh'O--s"a'Cn-=dces'-t-"o"n~e~s-=;=2-=0~%=s~a~n~d~s~t=on=e-,=t-h-=i~n=(~t'-o-2_0_c_m_l~,~g-r_a_y_a_n_d_b_r_o_wn_.~_c_r_o_s~s--_•_t_r_a_t_-___ _ , \_ ification and lamination, some graded from coarse sand to silt or clay. VID VIC2 VI Cl VIB VIA . .. . . . . . . . ; .. ·.:: . . ~ ......... . 900,--.., ... . . . -. . . . . . . . . . . . . .· Sandstone and mudstone: 50% bedded (2-15 cm) gray and brown sandstone, some graded, cross-stratification common, some sandstones laminated , poorly sorted, carbon fragments commonly in laminations near tops; 45% mudstone, thin (2-8 cm), gray, lamination, convolute lamination, and disturbed bedding common; 5% pebble conglomerate, thin (8-10 cm) discontinuous to ungraded, poorly sorted. 88 53- . - - ..., -:--~ Pebble sandstone: 50% gray to brown, thick to very thick (0.5- 2.0 m), hard, cobble to pbble conglomerate, ~~--;_~";..-:_--.:._::~ commonly graded to sandstone, poorly sorted, many load forms; 40% gray, hard, coarse to fime sandstone with minor siltstone, commonly graded and poorly sorted, some mudstone clasts SO cm long, ungraded coarse sandstones I sometimes contain concretions; 10% gray interbedded mudstone, siltstone and shale with minor sandstone layers, convolutioL and flame structure common rare load forms. '--~1"'tu"do;.s"t"o'"n"e":=I~n"t"e"r"b-'ec:d~d"'e"'d'-,=t"'h~i~n=o(~S~cm~) =g~r=aLy~s~i"l'-t-~s~t~o~n~e~,=g=r~a~y-an-;-d-b""r_o_wn--c~l""a_y_s-ct-o_n_e_ -and very fine sands tone ( 15 % ) / beds with lamination and cross-stratification. ----------------------- / I 800--~ ' I I 700---1-_-_ -. ~-- .. -.---¥ . . . ;-... . • • • . • • :-- .• -;-c- •. 685~_j:..;..:_:..:_ :.:....:.:_:__ '-. c.:_:..;:,:,..i-- .. . ...... . .. . . . . . . . . . . . COVERED Pebbly sandstone: 68% tan, pebbly sandstone, medium thick (3-55 cm), most graded to silt or fine sand, ama~gamated, mudstone pebbles to 18 cm, most under 6 cm, undulose contacts, minor shell and lamination; 17% graded siltstone with lamination and cross-stratification; 15% gray mudstone, massive, some with silt lenses. 6b8.8- Pebble sandstones and conglomerate: 57% tarJ, pebbly sandstone, medium thick (2-54 c.m), most graded, ~ome pebhly at base, some sl1ell, lamination and cross·-stratification; 15% conglomerate, thick (30-70 cm), cobbles (to 10 cm), some graded to fine sand, slump; 28% gray mudstone and graded siltstone, lamination and cross-stratification, minor brown clavstone. . . . .:_· +----~~~~~~~=~-;;;;-;:;;---;:M;:t:(]"wt;~Y-;;;;;;;;:--;;;;;;;:-;;n;:;;;--;=,;;;;;;--;:;;=;;:;;-;i;;;;--;:;;-=;;:--;==~ :.-;.·--~.-·.:•_.,·· •.• ·.~ •• _~-.~.·:._:_:~_ Conglomerate: 71% conglomerate, veryd:hick (dll-lb4b5 1 cm) ,( mos 8 t ov)er 1 50 cm,fundulose con7af~tsd duedto scour 23 ,%grading 6514 _ in scm.e layers near top, reverse gra ing, mu co es to cm , ense o cross-strati ie san stone; o tan [':.~_7_~-~-~-~-~-~:~:~:~:~::t-~~~~~-~s~a~n~d~s~t~one and siltstone, wood fragments; 6% gray mudstone, differentially compacted. .. : · : · ·. . . . . Pebble sandstone: 86% tan to brown pebbly sandstone, very thick ( 150 cm), undulose contacts, graded from coarse J ~·::::·=·-=·::-:·::=:·-:::·::-:t----~--Jt~oLJs~1h'l~tt:__,__s~o£m"'!'e..1l~a~m~i~n~a~tJi~o~n~, . .__!n~o~t~a~se_£cQo~a~r~s~ec_;;a~sc_;;a~b~o~v~e~-c__Jl~4~%l,~m~u~d~s~t~oQn!l!le_1!aBn~d~s~iJl~t~sUt~o~n~e~-·L.JR~r~a~d~e~d~·!t~o'l'._o~o~f'--!s~a~n~d~s~t~oQn~e~s~.l~a~m,,;!i~n~a~t~i~o~n~.~ 623.9- - -- -. ~ Mudstone and sandstone: 76% gray mudstone and siltstone, thin (1-10 cm), graded, laminated and cross-stratified; :: ~ __ --.;;:-_ 24% tan sandstone, thin ( 9 cm), graded from medium of fine sand to mud. VB 600--; ---::_ ::-::-=-- VA IVC IVB IVA Ill "' llD llC 118 llA IC IB IA - - -· 582.2- -:-:-.---:.-:-. :-.:-.-.:-- ------ -- 538.0- - -- - - - --:_ --=- _-;:-_-_--= - - - -- 510.0- =:._=-=------:-::- .=-.--:--=-~: 500---1= _-_-_-:_-_-: : ' . . . ..... . Sandstone: 69% tan to brown sandstone, thick to very thick (2- 120 cm), most greater than 20 cm, many amalgamated, graded from coarse to clay, laminated fine sandstone, undulose contacts; 31% gray and brown mudstone and graded Qrav siltstone. thin ( 20 cm) laminated and cros?-stratified 2 microfault, minor wood fragments. Mudstone: 86% gray and brown mudstone and graded brown siltstone, thin (5-30 cm), laminated and cross-stratified; 484.J ·· .. · .... ·.·: .·.· ... I~ 14% tan sandstone. thin (1-8 cm). 2raded from fine to silt, laminated and cross-stratified, some pinch-outs. Mudstone and sandstone: 76% gray and dark brown mudstone and graded brown siltstone, medium thick (34-60 cm)~--- minor lamination in siltsone; 24% tan sandstone, thin (5-20 cm) , thicket layers than above, graded, load def ormation. Sandstone: 70% tan sandstone, thick (10-90 cm), graded, some reverse graded, amalgamated, cobbles up to 12 cm, load forms, scours, convoluted and laminated bedding, carbonized plant fragments and shell; 30% gray mudstone and siltstone, medium thick ( 40 cm), convoluted and parallel laminated siltstone. ~=~====~-~~~~'~--------------- 400---1 300---+ ... ...-:_; . . . . . . . . . '. · .... : : · .. _..:.,;. ·_ ·. -. 260.~,,_.;.,._ 7. :,c.:..:.:..:_:.c,~=v 254.2•-<f'-c-,CC· -=~·~==~-~:_,.. ,.= --::~ ~:::: --------- 232.1~;=_- - - - - - 226.l- - ....... - - . . . . . . . . . . . . . . . 213.1~ ·- ........... . 200-- >< COVERED -----------------~-------- --·---------~---------- Granule sandstone: 94% tan gravel sandsto' e, thick ( 50 cm), rounded to a11gular rip-up clay clasts, clast.s 1.coc than 10 cm, scours, graded granule to silt, minor shell; 6% graded siltstone and rnudstone. laminated. Mudstone and sandstone: 60% mudstone, red brown and chocalate brown, thin (2-10 cm) some containing tan silt lenses; 40% brown sandstone, thin (2-18 cm), graded, laminated and cross-stratified. ~~~~~-"-i-o:-=-'-=i~o--'-~-~~~~~------ Mud st one: 89% mudstone, gray and brown, thin to medium thick, massive, (1-42 cm), laminated; 11% fine to very fine sa4dstone, thin ( 7 cm), interla.minated with gray clavstone • Mudstone and sandstone: 62% gray siltstone and mudstone, thin ( 17 cm), graded, laminated and cross-stratified; 38% graded sandstone. thin ( 16 cm), laminated. Sandstone: 90% tan and brown sandstone, thick (14-95 cm), amalgamated, graded, coarse to silt, undulose contacts due to scour, rip-up clasts to 40 cm in length,laminated; 10% graded siltstone, laminated with carbonized wood, minor gray claystone . ----~---------------------------- ---- ----------. 175.l X ..... ,·., .·.• ·' -~· ~;:-~~~.~--i~~~~:o~~~~~[~~n-e--a-n_d_s_i_l_t_s_t_o_n __ e_:_7_1_%_t_a_n __ s_a_n_d;·-t-o-n-.e-,-t-h-.1-·n_t_o_m_e~d-i_u_m_t_h_i~c~k-7 (3"-~3-~-c-m7 )-,-a-m_a_l_g_a_ma_t_e_d_,_c_l_a_s_t_s __ t_o_1_8_c_m_,_l_o_a_d ____ _ and scour depre"'sions lensing of sandstone· 29% siltstone, brown, thin (3-23 cm), convoluted, laminated and "-.....,~_c_r_o_s_s_-_s_t_r_a_t_i_f_i_e_d~•~w_o_o_d_,_f_r_a_g~m_en_t~s~·-----·-·-------------------------------------- COVERED 100 103.1 -- - - , .. ---= .--·_.-_-::. - . - :._ ..: -- - -. -- - 1'1udsto-n"ec--::a=n'd-c:sc:a"n'd"s::t:-:o:-n:-:e:-::--7;c6"%",-g"r"a--::y:::-"a"n'd-,b_r_o_w_11.-n:-u'd""s"t_o_n_e_a_n_d-:--s-1 7 '"°l"t-s7 t_o_n_e_,_m_e_d"'i"'u_m_t"h""1""·c-k.---;('l'l--'1"'8c--c-m')-,-g-r_a_d;-e-d;-,-l;-a-m-,i_n_a_t_e_d-,---- and cross-stratified, thin ( 2 cm) sand lenses; 24% yellow and tan sandstone, medium thick (8-13 cm), graded, fine to clay, siltstone rip-ups to 10 cm, wood fragments. Muds tone and sandstone: 65% gray and brocwn"-c-,;-. n~t=e"r"b"e~d'd"e'dcccmc-u:-:dc:s:-:t:-:o:-:n:--e:----, -t::-h;:-,in:::--;('1~3"0;--c-m')"",-m-1;-. n-o-r-f'1 7 ' n-e--s-a-n"d~l-e_n_s_e_s_a_n_d~---- lamina t ed siltstone; 35% tan sandstone, medium thick (6-18 cm), graded, laminated,minor load and scour, wood fragments and mud pebbles less than 1 cm. COVERED ~g-.;_-;d-;to-;e·:lnd siltsto·n;;--6i% gray and tan sandstone: thick-(1-114-cm), most greater than 20 cm, graded, coarse ~ to clay, abundant scour and rip-up pebbles, pebbles to 9 cm,arnalgamated layers, load deformation; 22% graded : ~/ siltstone, grading from sandstone, laminated and cross-stratified; 17% laminated claystone, gray and red-brown. :~ Petroleum odor to lower sands, stained grains. f"- __ ,_.....,_ ~'""'-:~.,,.....~,.~.v ,/ -------- . ·.·."·.' ·-~··: .. ··~,~ .. BASE Of MEASURED SECTION PLATE I. Measured Stratigraphic Section at Santa Paula Creek

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University of Southern California Dissertations and Theses

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Asset Metadata

Creator Johnson, Bruce Alan (author)

Core Title Vertical sequence analysis of a deep-sea fan system, Santa Paula Creek, California.

Degree Master of Science

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

Tag Marine Geology,OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c30-83429

Unique identifier UC11225334

Identifier usctheses-c30-83429 (legacy record id)

Legacy Identifier EP58655.pdf

Dmrecord 83429

Document Type Thesis

Rights Johnson, Bruce Alan

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