Sedimentary Facies and Trace Fossils in the Eocene Delmar Formation and Torrey Sandstone, California
Total Page：16
File Type：pdf, Size：1020Kb
Rice University SEDIMENTARY FACIES AND TRACE FOSSILS IN THE EOCENE DELMAR FORMATION AND TORREY SANDSTONE, CALIFORNIA by Jannette Elaine Boyer A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Master of Arts Thesis Director's Signature: Houston, Texas ABSTRACT SEDIMENTARY FACIES AND TRACE FOSSILS IN THE EOCENE DELM&R FORMATION AND TORREY SANDSTONE, CALIFORNIA Jannette Elaine Boyer The Delmar Formation and Torrey Sandstone were studied in sea- cliff outcrops at Solana Beach, about 15 km north of San Diego. There, they represent lagoonal and barrier bar or shoal deposits, respectively. Five subfacies were recognized in these outcrops, utilizing observations on sediments, physical sedimentary structures, body fossils and trace fossils. The Delmar exhibits three subfacies that formed as oyster reefs, tidal flats, and sublittoral tidal channels and ponds. The Torrey contains two subfacies, representing suba¬ queous dunes and tidal channels on a tidal delta or interior side of a barrier bar or s.hoal, and large, temporary channels generated by drainage of the lagoon after periods of high run-off or storms. Trace fossils contribute significantly to the description and interpretation of these subfacies. Their density and diversity indi¬ cate brackish to marine conditions. The abundant lebensspuren Ophiomorpha nodosa and Gyrolithes indicate deposition in littoral to inner sublittoral zones; Gyrolithes is especially common in brackish environments of the Delmar lagoon. Sandy, high-energy facies of the Torrey Sandstone are characterized by large, vertically- oriented dwelling burrows and by vertical locomotion traces generated by infauna migrating up and down in response to sedimentation and erosion. Muddy, more protected environments of the Delmar Formation exhibit lese robust, horizontally-oriented dwelling burrows and an abundance of feeding burrows constructed by animals mining the or¬ ganic-rich sediment for food. Sedimentation and physical reworking were very active in Torrey environments, so trace fossils there dis¬ tort but do not obliterate physical sedimentary structures and bedding characteristics. In contrast, much of the Delmar has been heavily bioturbated, indicating predominance of biological reworking over physical processes. 1 ACKNOWLEDGEMENTS Dr. John E. Warme suggested the project, supervised the research, made available his collection of books, journals and reprints, and offered valuable comments and criticisms on the text. His generous, unwavering support as mentor and friend are deeply appreciated. A grant to Dr. Warme by the Henry L. and Grace Doherty Charitable Foundation financed this research. Dr. Michael P. Kennedy of the California Division of Mines and Geology furnished copies of his geologic quadtangle maps of the San Diego area, imparted freely of his experience and knowledge, and introduced me to other workers in the field. Among them, Dr. C. R. Givens was especially helpful; Dr. Givens made available much un¬ published information about the molluscan assemblage in the Delmar Formation. Dr. William C. Elsik of Esso Production Research studied pollen in several samples from my field area. Dr. Elsik furnished lists of identified pollen and spores and provided valuable paleoclimatlc information; I appreciate his help and his wonderful enthusiasm. I am especially grateful to Dr. J. Philip Kern (California State University, San Diego) and Claudia Kern, who cheerfully provided housing for one field season and helped me with the field work. I appreciate very much the advice and comments of Drs. J. L. Wilson (Rice), Cortez Hoskins (Union Oil Research), and R. J. Moiola (Mobil Oil Research). Drs. R. E. Casey and John J. W. Rogers of Rice University served with Dr. Warme as my thesis committee; both read the manuscript critically. il Mr. Michael L. Johnson of Rice kindly ran an oxygen isotope survey on an Ostrea valve. I enjoyed and benefited from discussions with several other past and present graduate students at Rice. Ms. Mary Hodge typed part of the manuscript when I thought there wasn't a typist left in Houston; Dr. Pat Rudd finished it in the wee hours of the morn. I also want to thank my family for welcoming without comment my all-too-short, usually working vacations at home and at the farm, and for their unwavering emotional and financial support. lii TABLE OF CONTENTS Page INTRODUCTION SIGNIFICANCE OF FACIES STUDIES UTILIZING TRACE FOSSILS 1 SCOPE AND AIM OF THIS STUDY 2 PREVIOUS WORK 5 - GEOLOGIC SETTING 8 SAN DIEGO AREA 8 LOCAL SETTING, DELMAR FORMATION AND TORREY SANDSTONE 12 SELECTION OF OUTCROPS 14 DESCRIPTION OF THE DELMAR FORMATION 17 STRATIGRAPHY AND GENERAL DESCRIPTION 17 PALEONTOLOGY 19 Microfossils 19 Macrofossils 23 SEDIMENTS 28 Composition 28 Texture 28 Depositional processes affecting texture 29 PHYSICAL SEDIMENTARY STRUCTURES 33 Interbedded sand and mud 33 Depositional processes affecting interbedded sand/mud 33 Micrograded beds 40 Thicker mud beds 40 Laminated sand 40 Cross-stratification 43 Sedimented shell beds 44 Bored claystone beds 45 BIOGENIC SEDIMENTARY STRUCTURES 47 DESCRIPTION OF THE TORREY SANDSTONE 52 STRATIGRAPHY AND CENERAL DESCRIPTION 52 PALEONTOLOGY 54 Microfossils 54 Macrofossils 54 SEDIMENTS 55 Composition 55 Texture 56 iv PHYSICAL SEDIMENTARY STRUCTURES 58 Trough cross-bedded sandstone 58 Large channels 60 Wedge-sets of cross-bedded sandstone 61 Interbedded sandstone and mudstone 61 BIOGENIC SEDIMENTARY STRUCTURES 63 DESCRIPTION AND INTERPRETATION OF SUBFACIES 66 GENERAL SETTING 66 SUBFACIES 67- Subfacies A: Oyster beds 68 Subfacies B: Flaser-bedded sequences 71 Subfacles C: Fining-upward sequences 73 Subfacies D: Large-scale trough cross-bedded sandstone 75 Subfacies E: Large channels 77 SIGNIFICANCE AND USEFULNESS OF TRACE FOSSILS IN THIS STUDY 81 CONCLUSIONS 85 REFERENCES CITED 87 APPENDIX I. TRACE FOSSILS 98 METHOD OF STUDY 98 DESCRIPTIONS OF TRACE FOSSILS 100 Domichnia 102 Ophlomorpha Lundgren and Thalassinoidea Ehrenberg 102 Gyrolithes Saporta 107 Fat, mud-lined burrows 114 Vertical burrows with sprelten 115 Borings in claystone 116 Fodinichnla 119 Ardella Chamberlain and Baer 119 Phycodes Richter 122 Small horizontal and vertical burrows 130 Dendritic burrows 130 Replchnla 133 Conostlchus 134 Vertical movement paths 139 Palaeophycus Hall 142 Cublchnla 145 Surface depress ions 145 Other trace fossils 148 Collapse structures 148 V APPENDIX II. GRAIN-SIZE ANALYSIS OF SEDIMENTS 153 TABLE OF CHARACTERISTICS OF SAMPLES FROM THE DELMAR FORMATION 154 TABLE OF CHARACTERISTICS OF SAMPLES FROM THE TORREY SANDSTONE 155 CUMULATIVE CURVES, SAMPLES FROM THE DELMAR FORMATION 156 CUMULATIVE CURVES, SAMPLES FROM THE TORREY SANDSTONE 157 APPENDIX III. CARBON AND OXYGEN ISOTOPE ANALYSIS 159 PLATES 160 ILLUSTRATIONS Figure Page 1 INDEX MAP, SAN DIEGO COASTAL AREA 3 2 GEOLOGIC COLUMN, SAN DIEGO COASTAL AREA 9 3 SCHEMATIC COLUMN AND FACIES DIAGRAM, DEL MAR QUADRANGLE 10 4 GEOLOGIC MAP, DEL MAR QUADRANGLE 13 5 LOCATIONS OF MEASURED SECTIONS 16 6 MEASURED SECTIONS (in pocket) 7 COMPOSITE STRATIGRAPHIC SECTION, DEIMAR FORMATION 18 8 PALYNOMORPHS 21 9 FLORA REPRESENTED BY PALYNOMORPHS 22 10 AGE OF FLORA 22 11 MOLLUSCS IN THE DEIMAR FORMATION 26-27 12 HISTOGRAMS OF SAND FRACTIONS 30 13 FLASER BEDDING AND RIPPLE CROSS-LAMINATION 36 vl 14 OCCURRENCES OF FUSER, WAVY, AND LENTICUUR BEDDING 38-39 15 MICROGRADED BEDS 41 16 LAMINATED SAND 42 17 TERMS EXPRESSING REUTIVE DENSITY OF BIOGENIC STRUCTURES 48 18 COMPOSITE STRATIGRAPHIC SECTION, TORREY SANDSTONE 53 19 URGE-SCALE TROUGH CROSS BEDDING 59 20 WEDGE-SETS OF CROSS BEDDED SANDSTONE 62 21 SUBFACIES A: OYSTER BEDS 69 22 SUB FACIES B: FUSER-BEDDED SEQUENCES 72 23 SUBFACIES C: FINING-UPWARD SEQUENCES 74 24 SUB FACIES D: URGE-SCALE TROUGH CROSS-BEDDED SANDSTONE 76 25 SUB FACIES E: URGE CHANNELS 78 26 CHARACTERISTICS OF SUBFACIES 80 27 DISTRIBUTION OF ETHOLOGICAL CUSSES OF TRACE FOSSILS 83 28 OPHIOMORPHA NODOSA GRADING INTO THAUSSINOIDES 103 29 OPHIOMPRPHA NODOSA (URGE FORM) 104 30 WALL STRUCTURE OF OPHIOMORPHA NODOSA 105 31 DIMENSIONS AND MORPHOLOGIC TERMINOLOGY OF GYROLITHES 109 32 GYROLITHES 111 33 GYROLITHES 112 34 GYROLITHES 113 35 VERTICAL BURROWS WITH SPREITEN 117 vil 36 ARDELIA 120 37 INTERNAL STRUCTURE OF PHYCODES 123 38 MORPHOLOGIC TERMINOLOGY OF PHYCODES 124 39 PHYCODES 126 40 HYPOTHETICAL ORIGIN OF PHYCODES 129 41 DENDRITIC BURROWS 131 42 MODERN PROGENITORS OF CONE-IN-CONE STRUCTURES (CONOSTICHUS) 136 43 CONOSTICHUS 137 44 CONOSTICHUS 138 45 VERTICAL MOVEMENT PATHS 141 46 PALAEOPHYCUS 144 47 SURFACE DEPRESSIONS 147 48 COLLAPSE STRUCTURE 150 49 COLLAPSE STRUCTURE 151 50 COLLAPSE STRUCTURE 152 Plates 1 FOSSILS IN THE DEIMAR FORMATION 160 2 SUBFACIES IN THE DEIMAR FORMATION 161 3 SEDIMENTS AND SEDIMENTARY STRUCTURES IN FLASER- BEDDED UNITS, DEIMAR FORMATION 162 4 MEDIUM-SCALE CROSS-BEDDING IN THE DEIMAR FORMATION 163 5 BORED CLAYSTONE BEDS AND CLAYSTONE CLASTS, DEIMAR FORMATION 164 viii 6 RELATIVE DEGREES OF BIOTURBATION 165 7 DUELLING BURROWS IN THE DEIMAR FORMATION 166 8 OPHIOMORPHA NODOSA (SMALL FORM) IN THE DEIMAR FORMATION 167 9 FEEDING BURROWS IN THE DEIMAR FORMATION 168 10 LARGE-SCALE TROUGH CROSS-BEDDED SANDSTONE, TORREY SANDSTONE 169 11 BOUNDARY BETWEEN DEIMAR AND TORREY FACIES 170 12 LARGE CHANNELS IN THE TORREY SANDSTONE 171 13 LARGE CHANNEL IN THE TORREY SANDSTONE 172 14 TRACE FOSSILS IN THE TORREY SANDSTONE 173 15 TRACE FOSSILS IN THE TORREY SANDSTONE 174 SEDIMENTARY FACIES AND TRACE FOSSILS IN THE EOCENE DELMAR FORMATION AND TQRREY SANDSTONE, CALIFORNIA INTRODUCTION Significance of Facies Studies