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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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Facies studies present a narrowing of the continental shelf during the Cretaceous-Paleocene transition in central California. Response to this changing environment was attended by accelerated evolution and proliferation of individuals prior to the extinction of many previous well adapted animal stocks, especially the ammonoids and the larger reptiles.
Evidence is lacking for the presumed unconformity between the Cretaceous and Tertiary sediments, and the often quoted Paleocene transgression is actually more regressive in character, with a considerable increase in red oxidized sandstones and associated tidal marsh leaf-bearing clastics.
The Late Cretaceous stratigraphic nomenclature is compromised with the increasingly continental trend of the Late Cretaceous deposits north of Los Banos Creek. For example, the Volta Member of the Garzas Formation northward grades from the medium-depth neritic foraminiferal marl of the Marca shale through the littoral calcareous sandstones of the "Mercy" Sandstone lentil to the brackish-water anauxitic sandstone member of the lower "Martinez" Formation.
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