Biomarker variations in relation to paleogeography in the Saltos Shale member of the Monterey Formation, Cuyama basin, California

Conference · Tue May 01 04:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6667380

Lillis, P G ^[1]

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1. Geological Survey, Denver, CO (USA)

The Miocene stratigraphy of the Cuyama basin provides an excellent opportunity to correlate geology with molecular organic geochemistry (e.g., biomartker compounds) because the paleogeography and paleobathymetry of the basin are well constrained by surface and subsurface geologic mapping and detailed micropaleontology. The Monterey Formation is composed of biogenous and terrigenous sediments that accumulated in a deep marine borderland basin adjacent to a Miocene shoreline. the lower member, the Saltos Shale, is predominately terrigenous sediment interbedded with impure carbonates that consist of foraminifera and calcareous nannofossils. The upper member, the Whiterock Bluff Shale, is composed of highly biogenous (siliceous and carbonate) sediments. The biomarker composition of the Saltos Shale is dependent on the relative contributions of planktonic and benthonic organisms, bacteria, and terrigenous organic matter transported from the nearby landmass. A general trend in biomarker distribution is observed in relation to paleogeography (i.e. proximity to shoreline). Pristane/phytane ratios, hopane/sterane ratios, oleanane/hopane ratios, and diasterane/sterane ratios are higher near the shoreline (to the east) because of increased terrigenous input. The more distal western basin sediments contain biomarkers that were predominately derived from marine phytoplankton and bacteria. Submarine fan sediments in the Saltos Shale were deposited in the eastern basin east of the penecontemporaneous Cox fault. Ponding of terrigenous organic matter at the base of slope is reflected by high ratios of pristane/phytane (2.7), oleanane/hopane (0.79), C{sub 29}/C{sub 27} {alpha}{alpha}{alpha}2OR steranes (1.56), and relatively large amounts of waxy n-alkanes (C{sub 27}, C{sub 29}, C{sub 31}). In contrast, the prefan and postfan sediments contain lower concentrations of these terrigenous biomarkers.

• OSTI ID: 6667380
• Report Number(s): CONF-900605--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Journal Volume: 74:5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
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& Exploration
58 GEOSCIENCES
580000 -- Geosciences
CALIFORNIA
CENOZOIC ERA
CHEMISTRY
FEDERAL REGION IX
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FORMATIONS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGY
HYDROCARBONS
MATURATION
NORTH AMERICA
ORGANIC COMPOUNDS
ORGANIC MATTER
ROCKS
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SHALES
STRATIGRAPHY
TERTIARY PERIOD
USA