HR: 1340h
AN: ED43A-0845    [Abstracts]
TI: The Purisima Formation at Capitola Beach, Santa Cruz County, CA: A Deeper Examination of Pliocene Fossils
AU: White, L D
EM: lwhite@sfsu.edu
AF: San Francisco State University, Geosciences Department, 1600 Holloway Avenue, San Francisco, CA 94132 United States
AU: * Brooks, K
EM: cranberrychild@gmail.com
AF: Balboa High School, 1000 Cayuga Avenue, San Francisco, CA 94112 United States
AU: Chen, R
EM: st00pidbaka@gmail.com
AF: Balboa High School, 1000 Cayuga Avenue, San Francisco, CA 94112 United States
AU: Chen, T
EM: xspeciALTee@netscape.net
AF: Philip and Sala Burton High School, 400 Mansell Street, San Francisco, CA 94134 United States
AU: James, T
EM: Jamesgrndm9@aol.com
AF: Philip and Sala Burton High School, 400 Mansell Street, San Francisco, CA 94134 United States
AU: Gonzales, J
EM: sk8erjgonz@msn.com
AF: San Francisco State University, Geosciences Department, 1600 Holloway Avenue, San Francisco, CA 94132 United States
AU: Schumaker, D
EM: daveschumaker@gmail.com
AF: San Francisco State University, Geosciences Department, 1600 Holloway Avenue, San Francisco, CA 94132 United States
AU: Williams, D
ED43A-0845 AF: University of New Orleans, Department of Geology and Geophysics, 2000 Lakeshore Drive, New Orleans, LA 70148 United States
AB: Fossil samples from the Pliocene Purisima Formation at Capitola Beach in Santa Cruz County, CA were collected in July-August 2005. The Purisima Formation composes the bulk of the cliffs exposed at Capitola Beach and a rich assemblage of well-preserved fossils occur in gray to brown sandstone and siltstone. Erosion of the cliff face averages 0.3 meter/year and fresh cliff falls in the winter and spring months of 2005 provided an excellent opportunity to resample the Capitola Beach section of the Purisima Formation previously documented by Perry (1988). Organisms were identified from information in Perry (1988) and were compared with collections at the California Academy of Sciences. The most abundant fossils found are from the phylum Mollusca, classes Bivalvia and Gastropoda. Abundant bivalve taxa are: Anadara trilineata, Clinocardium meekianum, Macoma sp., Protothaca staleyi, and Tresus pajaroanus. Also common are the gastropods, Calyptraea fastigata, Crepdiula princeps, Mitrella gausapata, Nassarius grammatus, Nassarius californianus, Natica clausa, and Olivella pedroana. Less common invertebrate fossils are from the phylum Echinodermata ( Dendraster sp., the extinct fossil sand dollar) and from the phylum Arthropoda ( Crustacea), crab fragments ( Cancer) and barnacles ( Balanus). Because numerous fossils are concentrated as fragments in shell beds, Norris (1986) and Perry (1988) believe many were redeposited as storm beds during strong current events that promoted rapid burial. In contrast, whale and other vertebrate bones are common in certain horizons and their presence may be related to the conditions that promoted phosphate mineralization, such as episodes of low sedimentation rates and prolonged exposure on the seafloor (Föllmi and Garrison, 1991). The bone beds, together with the rich infaunal and epifaunal invertebrate assemblages, represent a community of invertebrate organisms that thrived in a shallow marine sea during the Pliocene epoch, approximately 3-5 million years ago.
DE: 4950 Paleoecology
SC: Education and Human Resources [ED]
MN: Fall Meeting 2005