| Summary: | A 6012-foot Monterey Formation succession at Chico Martinez Creek, San Joaquin basin, is characterized at high spatial resolution by spectral gamma-ray data in 2- foot increments, 5-foot lithologic descriptions, and qualitative XRD and FTIR analysis. Based on these data, the 4 Monterey members–the Gould, Devilwater, McDonald and Antelope shales–are subdivided into 7 distinctive lithofacies. New paleomagnetic data, combined with industry-provided biostratigraphy establishes a chronostratigraphic framework and allows determination of linear sediment accumulation rates. Condensed sedimentation at the onset of McDonald deposition (~14 Ma) is also observed in correlative members in the Pismo, Santa Maria and Santa Barbara basins. This regional event is associated with eustatic regression from the Mid-Miocene highstand related to formation of the East Antarctic Ice Sheet and ongoing thermotectonic basin subsidence. A surge in linear sediment accumulation rates in the siliceous upper McDonald and Antelope (~10.4 Ma) is attributed to a regional increase in diatom productivity.
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