Early Tertiary Continental Borderland of Central California
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S·edimentation and Tectonics in the Early Tertiary Continental Borderland Of Central California \ GEOLOGICAL SURVEY PROFESSIONAL PAPER 925 mJJRl£A[21 Of r:.r~~l~~: !UBRARV £?OKANE, WASN. , !;;'·"'-' iQ 'll '1 ,t.gAJ!, :(~fA~£ R~~·. _·,,._\ [©1 Sedimentation· and Tectonics in the Early Tertiary Continental Borderland Of Central California By TOR H. NILSEN and SAMUEL H. CLARKE, Jr. GEOLOGICAL SURVEY PROFESSIONAL PAPER 925 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1975 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress catalog- card No.7 6-7 6 2 4 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Page Abstract 1 Lower Tertiary stratigraphic units-Continued Introduction _______________________________________________ _ 1 Southeastern area -------------------------------------- 24 Acknowledgments _____________________________________ _ 3 Cadon Pass area ---~-------------------------------- 24 Summary of Mesozoic tectonic history----------------------- 3 Orocopia Mountains -------------------------------- 24 Lower Tertiary stratigraphic units -------------------------- 4 Southwestern'area ______________________________________ 24 ~orthwestern area _____________________________________ _ 6 Ortega Hill, Pine Mountain, Santa Ynez Mountains, (}ualala area ---------------------------------------- 6 and Topatopa Mountains areas -------------------- 25 Point Reyes --.-------------------------------------- 7 Piru Creek area ------------------------------------ 29 Point San Pedro----------------------.-------------- 7 Las Lladas Canyon, Simi Hills, and Santa Susanna Santa Cruz Mountains------------------------------ 7 Mountains areas __________________________ --______ 29 San Juan Bautista area ---------------------------- 11 Santa Monica Mountains ____________________________ 30 PointLobos ---------------------------------------- 11 Elsmere Canyon and (}old Creek areas -------------- 30 ~orthern Santa Lucia Range------------------------ 11 Elizabeth Lake Canyon .and Valyermo areas __________ 30 Adelaida area -------------------------------------- 12 Channel Islands------------------------------------ 30 La Panza, southern Santa Lucia, and Sierra Madre Santa Ana Mountains and San Joaquin Hills -------- 31 San ~icolas Island __________________________________ 31 Ranges ------------------------------------------ 12 Pattiway Ridge area ---------------------------.,----- 12 Western Peninsular Ranges ---"'"-------------------- 32 Mount Pinos area -----------------------------'----- 13 Lake Elsinore, Lake Henshaw, and Jaccumba ~ortheastern area __ __ __ _ _ __ ____ __ ___ ___ __ __ _ _ _ _ _ __ __ _ __ 13 Valley areas-------------------------------------- 32 Sierra ~evada ___ __ _ __ __ _ _ _ _ ___ __ _ _ _ _ _ __ __ _ _ _ __ __ _ __ 13 ~orthern Bada California ____________________________ 33 Franciscan assemblage in the northern Coast Ranges__ 14 Early Tertiary history.of the San Andreas fault ---------.----- 33 Round Valley area---------------------------------- 14 Early Tertiary paleogeography ------------------------------ 36 Introduction ____________________________________________ 36 Rice Valley area------------------------------------ 14 Middle Mountain area ------------------------------ 15 Source areas ------------------------------------------ 36 Clear Lake area ------------------------------------ 15 Eastern nonmarine deposits ---------------------------- 39 Mount Diablo area and Sacramento Valley area ______ 15 Shallow marine shelf deposits -------------------------- 40 San Leandro Hills ---------------------------------- 17 Continental slope and ocean floor deposits---------------- 42 San Jose area-------------------------------------- 17 Introduction ________________________________________ 42 Tesla area__________________________________________ 18 Orestimba area -----------------------~------------ 19 Hemipelagic deposits ------------------------------ 42 Laguna Seca area ---------------------------------- 19 Deep-sea fans deposited east of the borderland and Bolado Park area ---------------------------------- 19 derived from eastern source areas __________________ 43 Vallecitos area ------------------------------------ 20 Continental borderland deposits ------------------------ 45 ~orthern Temblor Range, southern Diablo Range, Deep-sea trench deposits -------------------------------- 46 and adjacent San Joaquin Valley ------------------ 21 Sedimentology of the borderland deep-sea fans ________________ 47 San Emigdio and western Tehachapi Mountains and adjacent southern San Joaquin Valley ________ 22 Tectonic framework of borderland sedimentation ______________ 48 Southern Tehachapi Mountains ______________________ 23 Summary and conclusions ---------------------------------- 52 El Paso Mountains __________________________________ 24 References cited ___ ___ __ __ __ ___ _____ ____ __ ___ ___ ___ ____ __ ___ 54 ILLUSTRATIONS Page FIGURE 1. Index map of California showing mador geomorphic and tectonic provinces, mador faults, and informal geographic divisions___ 2 2. Index map of California showing outcrops of lower Tertiary sedimentary rocks----------------------------------------_ 4 3. Index map of the western Transverse Ranges showing outcrops of lower Tertiary,sedimentary rocks--------------------_ 26 4. Diagram showing inferred history of offset along the San Andreas fault in central California -------------------------~ _ 34 5. Schematic maps showing Mesozoic and Cenozoic plate relations in the western Pacific Ocean -------------------------- _ 35 6. Diagrammatic sketch showing the early Tertiary tectonic development of central California____________ ----------------_ 37 7. <1eneralized paleogeographic map of early Tertiary California--------------------------------------------------------_ 38 8. <1eneralized map showing tectonic activity within the early Tertiary continental borderland of western California -------- 50 III IV CONTENTS TABLES Page TABLE 1. Lower Tertiary megainvertebrate and foraminiferal stages in California------------------------------------------------ 5 2. Sedimentary structures and features reported from inferred deep-sea fan deposits of the early Tertiary continental bor derland and adjacent areas of California__________________________________________________________________________ 8 3. Comparison of thicknesses and depositional intervals of inferred deep-sea fan deposits of the early Tertiary continental borderland and adjacent areas of California ---------------------------------------------------------------------- 10 SEDIMENTATION AND TECTONICS IN THE EARLY TERTIARY CONTINENTAL BORDERLAND OF CENTRAL CALIFORNIA By ToR H. NILSEN and SAMUEL H. CLARKE, JR. ABSTRACT tracted the attention of many geologists during recent We infer that the most prominent early Tertiary paleogeographic years (fig. 1). These rocks form sequences as much as features of central California were the Sierran landmass to the east 25,000 ft (7 ,600 m) thick in some areas. The rocks con and the Salinian island area or peninsula to the west, both underlain sist primariiy of thickly bedded to massive, medium- to by granitic crust, and a trough-shaped deep marine basin which coarse-grained sandstone with subordinate amounts of separated the two, underlain by oceanic crust. These elongate ele conglomerate, siltstone, and mudstone. Ungraded ments trended approximately north-south, parallel to the edge of the North American continent. Clastic sediment from erosion of the Sier sandstone beds as much as 75 ft (23 m) thick or more ran landmass was transported westward and deposited in adjacent have been noted; other thick beds may be reverse fluvial, nearshore, shallow marine, and deep marine environments. graded in the lowermost part or normally graded in the The Salinian area was probably detached from the Sierran landmass uppermost part, with sandstone grading sharply up by pre-Eocene right-lateral faulting along its eastern edge; it formed a ward into thin siltstone or mudstone layers. These continental borderland consisting either of irregular island uplands separated by deep marine basins or a very irregularly shaped penin sandstones typically lack internal structures except for sula. large irregularly shaped mudstone clasts, diffuse paral Detritus eroded from the borderland was deposited primarily as lel laminations, and dish structures, which were first submarine fans at bathyal to abyssal depths within the borderland recognized in these rocks by Wentworth (1967). basins and on the sea floor to the east and west. These early Tertiary The origin of these sandstone sequences has been the submarine fan deposits are similar throughout the central Coast Ranges and contain assemblages of proximal and distal turbidites, subject of considerable controversy, and in the past they deep-sea conglomerates, grain-flow deposits, and hemipelagic shales. have been interpreted as shallgw marine transgressive They differ from most modern deep-sea fan deposits and typical flysch and regressive shelf deposits, deltaic deposits, a type of sequences in that they are very thick but limited in areal extent, and flysch, a type of turbidite, grain-flow deposits, and more consist mostly of coarse terrigenous detritus. The conglomerates recently, as deep-sea fan deposits. The few megafossils commonly contain clasts as large as boulders, are very thickly and irregularly bedded, and are