Bivalve - Panopea generosa?
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ITEM# TRACE-California-0003
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Miocene/Pliocene - 7 - 2.6 mya
Purisma Formation
Santa Cruz County, California
ITEM# TRACE-California-0003
These trace fossils are from the Purisima Formation near Davenport, California. This large multiple specimen does NOT still contains remnants of the bivalves.
The Purisima Formation is an important upper Miocene and Pliocene stratigraphic unit in central California, cropping out from the coast at Point Reyes north of San Francisco to more extensive exposures in the Santa Cruz Mountains to the south. The fine-grained rocks in the lower parts of the Purisima Formation record a latest Miocene transgressive event, whereas the middle and upper parts of the formation consist of increasingly clastic-rich siltstones and sandstones resulting from uplift of adjacent coastal regions and the Sierra Nevada during Pliocene transgressive and regressive sea-level events.
Exposures of the Purisima occur in three different, fault-bounded, structural blocks—the Santa Cruz, Pigeon Point, and Point Reyes tectonic blocks—that complicate correlations and regional age assignments. We summarize and compare published and new biostratigraphic and geochronologic data for various exposures of the Purisima Formation on the basis of mollusks, diatoms, radiometric dating, magnetostratigraphy, tephrochronology, and strontium isotope dating. On the basis of these data, we conclude that the Purisima Formation ranges in age from the latest Miocene (about 7 Ma) to the late Pliocene (about 2.6 Ma).
Purisma Formation
Santa Cruz County, California
ITEM# TRACE-California-0003
These trace fossils are from the Purisima Formation near Davenport, California. This large multiple specimen does NOT still contains remnants of the bivalves.
The Purisima Formation is an important upper Miocene and Pliocene stratigraphic unit in central California, cropping out from the coast at Point Reyes north of San Francisco to more extensive exposures in the Santa Cruz Mountains to the south. The fine-grained rocks in the lower parts of the Purisima Formation record a latest Miocene transgressive event, whereas the middle and upper parts of the formation consist of increasingly clastic-rich siltstones and sandstones resulting from uplift of adjacent coastal regions and the Sierra Nevada during Pliocene transgressive and regressive sea-level events.
Exposures of the Purisima occur in three different, fault-bounded, structural blocks—the Santa Cruz, Pigeon Point, and Point Reyes tectonic blocks—that complicate correlations and regional age assignments. We summarize and compare published and new biostratigraphic and geochronologic data for various exposures of the Purisima Formation on the basis of mollusks, diatoms, radiometric dating, magnetostratigraphy, tephrochronology, and strontium isotope dating. On the basis of these data, we conclude that the Purisima Formation ranges in age from the latest Miocene (about 7 Ma) to the late Pliocene (about 2.6 Ma).