Paleoecology of middle and late Miocene Monterey Formation, Upper Newport Bay, Newport Beach, California
The Miocene Monterey Formation exposed along the cliffs of Upper Newport Bay represents a lower calcareous facies dominated by foraminifera and coccoliths, indicating warm climate and low nutrient waters, and a siliceous facies consisting of diatomaceous rocks, which records high productivity as a result of climatic deterioration and intensified upwelling. Using the distribution and preservation of foraminifera in the California continental borderland basins as a modern analog, they interpret the effect of changing environmental (climatic and oceanographic) conditions during the middle and late Miocene on the distribution and preservation of foraminifera, calcareous nannofossils, radiolarians, diatoms, and sediments. Two stratigraphic sections were sampled: (1) middle Miocene (Luisian) section 1, and (2) late Miocene (upper Mohnian) section 2. Section 1 best correlates with the middle Miocene Sphenolithus heteromorphus nannofossil zone. Benthic foraminifera indicate deposition in upper bathyal to upper middle bathyal depths. Poor preservation of calcareous tests is generally associated with homogeneous sediments, whereas better preservation is correlated with indistinctly laminated rocks. Stratigraphic section 2, which accumulated in upper bathyal depths, covers parts of the early late Miocene (upper Mohnian) Denticulopsis hustedtii-D. lauta and D. hustedtii diatom zones. Foraminifera and nannofossils are generally more abundant and better preserved in well laminated sediments than in sediments with homogeneous to indistinct laminations. Benthic foraminifera favoring low oxygen conditions have low diversities in rocks with poorly preserved laminations, but have higher densities in well laminated intervals.
- Research Organization:
- Univ. of Southern California, Los Angeles
- OSTI ID:
- 5187151
- Report Number(s):
- CONF-8608105-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 70:7; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
ANIMALS
CALIFORNIA
CARBONATE ROCKS
CENOZOIC ERA
DEPOSITION
FEDERAL REGION IX
FORAMINIFERA
GEOLOGIC AGES
GEOLOGIC FORMATIONS
INVERTEBRATES
MICROORGANISMS
NORTH AMERICA
PALEONTOLOGY
PROTOZOA
ROCKS
SARCODINA
SEDIMENTARY ROCKS
TERTIARY PERIOD
USA