Age, stratigraphy, and correlation of the late Neogene Purisima Formation, central California coast ranges / C.L.Powell II et al. - Reston: U.S. Geological Survey, 2007. - iv, 32 p.: ill. (some col.), maps. - (Professional paper; 1740). - Ref.: p.17-22. - ISBN 978-4113-1848-9  Место хранения:   018 | Институт нефтегазовой геологии и геофизики им. А.А.Трофимука | Новосибирск | Библиотека

Оглавление / Contents

Abstract ........................................................ 1 Introduction .................................................... 1 Previous Work ................................................... 2 Geologic Framework .............................................. 4 Structural Blocks ............................................ 4 Santa Cruz Block .......................................... 4 Regional Stratigraphy .................................. 4 Purisima Formation Members ............................. 5 Age ................................................. 5 Depositional Environment of the Type Purisima Formation Members ................................... 6 Supplementary Reference Section ........................ 6 Age ................................................. 8 Southeast Santa Cruz County ............................ 8 Seal Cove Section ..................................... 10 Pigeon Point Block ....................................... 10 Stratigraphy .......................................... 10 Año Nuevo Section .................................. 11 San Gregorio Beach Section ......................... 11 San Gregorio Fault Offsets ......................... 13 Point Reyes Block ........................................ 13 San Francisco Bay Block .................................. 14 Chronostratigraphic Ages and Correlation of the Purisima Formation ...................................................... 14 Tephrochronology ............................................ 14 Mollusks .................................................... 15 Diatoms ..................................................... 15 Strontium Isotopes .......................................... 16 Tectonic Implications .......................................... 17 Conclusions .................................................... 17 Acknowledgments ................................................ 17 References Cited ............................................... 17 Appendixes 1. Diatom Floras From the Purisima Formation ................... 24 2. Locations of Tephra Samples From the Purisima Formation ..... 26 Pigeon Point Tectonic Block ................................. 26 Santa Cruz Tectonic Block ................................... 27 3. Tephra Layers in the Purisima Formation, West-Central California, and Correlative Units ........................... 28 A. Ash in the Purisima Formation, San Gregorio and Pomponio Beach areas ..................................... 28 B. Ishi Tuff (~2.5 Ma), Chico Monocline, eastern Sacramento Valley, and correlative tuff, Kettleman Hills, San Joaquin Valley ................................ 28 C. Ash in Purisima Formation, northeast of Santa Cruz (collected by E. Brabb) .................................. 28 D. Tephra of earliest (?) eruptions of Nomlaki Tuff and ash flows, northern Sacramento Valley .................... 29 E. Disseminated volcanic glass shards in Purisima Formation, between Pomponio and Pescadero Beaches, at the mouth of Long Gulch, west of the San Gregorio Fault .................................................... 29 F. Putah Tuff, proximal and distal localities ............... 29 G. Ash in basal Paso Robles Formation, Topo Valley .......... 30 H. Ash in Huichica Formation ................................ 30 I. Ash in Purisima Fm., west of Pt. Santa Cruz .............. 30 J. Upper ash in uppermost Pancho Rico Formation, beneath Paso Robles Formation, Topo Valley ....................... 30 K. Lower ash in uppermost Pancho Rico Formation, beneath upper ash, Topo Valley ................................... 31 L. Tephra layers in upper Etchegoin Formation, east of Kettleman Hills .......................................... 31 4. Sr Analysis of the Bivalve Mollusk Anadara trilineata (Conrad) in the Supplementary Reference Section of the Purisima Formation Along the Coast Between Point Santa Cruz and Rio del Mar, Northern and Eastern Monterey Bay, Central California .......................................... 32 Figures 1. Map of Purisima Formation outcrops and structural block map of the San Francisco Bay area ............................ 1 2. Supplementary reference section of the Purisima Formation around Santa Cruz ............................................ 3 3. Map showing location of the various parts of the Santa Cruz section ...................................................... 4 4. Correlation of stratigraphic sections in the Santa Cruz and Point Reyes tectonic blocks .................................. 7 5. Chronostratigraphic correlation of tephra layers in the Purisima Formation ....................................... 9 6. Purisima Formation exposures in plunging syncline, intertidal zone at Moss Beach ............................... 11 7. Generalized sea-cliff geology on south side of Point Ano Nuevo, San Mateo County ..................................... 12 8. Onset of increasing clastic sedimentation in coastal California .................................................. 16