Paleogeographic and paleoecologic model as a predictive tool for Late Miocene accumulation of biosiliceous sediments in the Monterey Formation of the San Joaquin basin, California

Conference · Fri Mar 01 04:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5862831

Bulter, T H ^[1]; Dumont, M P ^[2]

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1. ARCO Oil and Gas Co., Plano, TX (United States)
2. ARCO Oil and Gas Co., Bakersfield, CA (United States)

The marine ecology of diatoms in the Pacific Ocean can be invoked to explain late Miocene diatom population trends. The impact of seafloor physiography on diatom productivity in the modern ocean was compared with mappable biosiliceous trends in the Monterey Formation of the San Joaquin basin, California. A depositional model is proposed to explain the significance of paleogeography on variations in the biosiliceous content of the Monterey Formation. Diatoms thrive where nutrient-rich bottom waters flow upslope to replace the surface waters moved basinward by atmospherically induced circulation. Organic-rich siliceous material settles through the water column beneath the upwelling region. Oxidation of organic matter within the water column below the areas of intense upwelling creates an oxygen-depleted layer and limits bioturbation at the sediment-water interface. The resultant sedimentary rocks are laminated siliceous shales characteristic of the Monterey Formation. Forty-two Monterey well penetrations form a variety of locations in the San Joaquin basin were analyzed for biosiliceous content. Biosiliceous facies trends were established by relating the quantity of siliceous material to depositional environment and paleobathymetry. Lithofacies trends were then modeled using the paleogeography of the San Joaquin basin during the late Miocene. According to the model, the rocks with the highest content of biogenic silica are expected in a slope setting. This model also suggests that slop angle controls the intensity of upwelling and subsequent diatom productivity.

• OSTI ID: 5862831
• Report Number(s): CONF-910403--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Journal Volume: 75:3
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALGAE
BATHYMETRY
BIOLOGICAL MARKERS
CALIFORNIA
CENOZOIC ERA
CHROMOPHYCOTA
DEPOSITION
DEVELOPED COUNTRIES
DIATOMACEOUS EARTH
DIATOMS
GEOLOGIC AGES
GEOLOGIC FORMATIONS
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
MIOCENE EPOCH
NORTH AMERICA
ORIGIN
PLANTS
SEDIMENTARY BASINS
SEDIMENTS
TERTIARY PERIOD
USA