BUREPIV Of llti~N.ES U~~fo.~V ~BffiNfE. ~".1A$1J10 MAR1i 2 1982 l~~EASf ~rru~~ W U®~A~~ Suratigraphy, Paleontology, and Geoliogy CCfiR rtJllle Central Santa Cruz Mountains~ (California Coast Ranges CG lE ~ »JL «) ~G ll (~ A I.. S l T R V lE Y P R 0 JF 1E S § H 0 N A lL lF A lP IE. m. n n (fi § c/ I Stratigraphy, Paleontology, and Geology of the Central Santa Cruz Mountains, California Coast Ranges By JOSEPH C. CLARK GEOLOGICAL SURVEY PROFESSIONAL PAPER 1168 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1981 UNITED STATES DEPARTMENT OF THE INTERIOR JAMES G. WATT, Secretary GEOLOGICAL SURVEY Doyle G. Frederick, Acting Director Library of Congress Cataloging in Publication Data Clark, Joseph C. Stratigraphy, paleontology, and geology of the cen­ tral Santa Cruz Mountains, California Coast Ranges. (Geological Survey professional paper; 1168) Bibliography: p. 47-51 Supt. of ·Docs. no.; I 19.16:1168 1. Geology, Stratigraphic--Tertiary. 2. Geology-­ California--Santa Cruz Mountains. I. Title. II. Series. QE691.C42 551.7'8'097947 81-607048 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Pat;c Page Stratigraphy northeast of San Gregorio Fault-Continued Abstract ................................................................................................... Middle Miocene sedimentary sequence ............... ·.................. 18. Introduction ........................................................................................... 1 Lompico Sandstone ............................................................. 18 Geography ..................................................................................... 1 Monterey Formation ........................................................... 20 Procedure ....................................................................................... 2 Depositional environment of middle Miocene Previous work ............................................................................... 4 sequence ............................................................................. 24 Acknowledgments ....................................................................... 5 Upper Miocene to Pliocene sedimentary sequence ........... 25 Geologic setting ................................................................................... 5 Santa Margarita Sandstone ............................................. 25 Crystalline rocks ................................................................................. 5 Santa Cruz Mudstone ......................................................... 30 Northeast of San Gregorio fault ............................................. 5 Purisima Formation ........................................................... 33 Southwest of San Gregorio fault ............................................. 7 Depositional environment of upper Miocene to Stratigraphy northeast of San Gregorio fault ........................... 7 Pliocene sedimentary sequence ................................... 35 Paleocene sedimentary sequence ..................................... :..... 7 Stratigraphy southwest of San Gregorio fault ........................... 36 Eocene to lower Miocene sedimentary sequence ............... 10 Pigeon Point Formation ...................................................... ~ .... 36 Butano Sandstone ............................................................... 10 Vaqueros(?) Formation ............................................................. 37 Lower sandstone member ......................................... 10 Monterey Formation .............. ~ .................................................... 38 Middle siltstone member ........................................... 11 Purisima Formation ................................................................... 39 Upper sandstone member ......................................... 11 Quaternary deposits ........................................................................... 40 'l'hickness ................................................. :..................... 12 Marine terrace deposits ............................................................. 40 Age ................................................................................... 12 River terrace deposits ................................................................. 41 Butano(?) Sandstone ........................................................... 12 Landslide material ..................................................................... 41 San Lorenzo Formation ..................................................... 13 Alluvium ......................................................................................... 41 Twobar Shale Member ............................................... 13 Structure ................................................................................................. 42 Rices Mudstone Member ........................................... 13 San Gregorio fault ....................................................................... 42 Zayante Sandstone ............................................................. 14 Zayante fault ................................................................................. 44 Vaqueros Sandstone ........................................................... 15 Minor faults ................................................................................... 45 Lan1bert Shale....................................................................... 16 Folds ................................................................................................. 45 Depositional environment of Eocene to lower Fossil localities ..................................................................................... 46 Miocene sedimentary sequence ................................... 17 References cited ................................................................................... 48 ILLUSTRATIONS Page PLAn: 1. Geologic map and sections of the Ano Nuevo-Davenport area, San Mateo and Santa Cruz Counties .................... In pocket 2. Geologic map and sections of the Felton-Santa Cruz area, Santa Cruz County, California ........................................ In pocket FIGUHE 1. Generalized geologic map of the northern and central Santa Cruz Mountains ............................................................................. 3 2. Composite stratigraphic section of Tertiary rocks of central Santa Cruz Mountains northeast of San Gregorio fault ............................................................................................................................................................................................................... 8 3-13. Photographs showing: 3. Mudstone beds in lower part of Monterey Formation on north limb of Scotts Valley syncline ................................. 21 4. Siltstone beds in upper part of Monterey Formation on north limb of Scotts Valley syncline ................................. 22 5. Unconformable contact between Monterey and Santa Margarita Formations on north limb of Scotts Valley syncline ......................................................................................................................................................... 23 6. Crossbedded Santa Margarita Sandstone with thick gravel interbeds ............................................................................. 26 7. Astrodapsis beds in Santa Margarita Sandstone ................................................................................................................... 28 8. Astrodapsis beds in Santa Margarita Sandstone at USGS locality M5155 ..................................................................... 29 9. Santa Margarita Sandstone-Santa Cruz Mudstone contact on east side of Moore Creek canyon ........................... 29 10. Santa Cruz Mudstone capped by marine terrace sand at Natural Bridges Beach State Park near Santa Cruz ......................................................................................................................................................................... 30 11. Santa Cruz Mudstone overlain by Purisima Formation in sea cliffs below West Cliff Drive, Santa Cruz ................................................................................................................................................................................... 31 12. Mudstone member of the Purisima unconformable upon the Monterey east of Aiio Nuevo Point ........................... 39 13. Ai'io Nuevo fault east of Ai'io Nuevo Point ................................................................................................................................. 42 14. Contrasting stratigraphic sections across the San Gregorio fault in the central Santa Cruz Mountains ............................. 43 III IV CONTENTS TABLES Page TABLE 1. Paleocene megainvertebrates from the Locatelli Formation.............................................................................................................. 9 2. Terrigenous minerals of the Butano Sandstone .................................................................................................................................... 10 3. Megainvertebrates from the Vaqueros Sandstone................................................................................................................................ 16 4. Terrigenous minerals of the middle Miocene sequence.......................................................................................................................