Paleoceanographic influences on compositional trends in the Monterey Formation, western Santa Barbara coastal area, California: Contrasts between banktop and distal slope settings

Conference · Wed Jan 01 00:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5935951

Miller, N R ^[1]

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1. Univ. of Texas, Dallas, TX (United States). Program in Geosciences

The modern ocean-atmosphere system, consisting of cold polar regions, strong latitudinal temperature gradient, and strong thermocline, evolved as a consequence of Miocene paleoceanographic and paleoclimatic transitions, which were contemporaneous with deposition of the organic-rich Monterey Formation. Deep sea records show mid-Miocene enrichment shifts in C-13 (ca17.5 to ca13.5 Ma), lagged by C-18 (beginning around 15 Ma), suggesting that reverse greenhouse cooling led to intensified cryosphere development. Graphic correlation of Sr isotope and biostratigraphic data indicates that the South Ellwood section contains a more continuous record of organic accumulation. At Naples, highest organic contents are associated with the hardground-bearing carbonaceous marl member, which is condensed between strata bearing Luisian and Early Mohnian benthic foraminifera. Duration of the condensed interval is unresolved by biostratigraphy and Sr isotope estimates over a wide time range (7.5 to 15.7 Ma), but ages younger than 13 Ma are generally inferred for timing of maximum organic carbon accumulation. In contrast, richest organic facies at South Ellwood occur within a 300 to 400 foot interval containing Relizian and Luisian fauna, spanning the 18 to 13 Ma interval. Stable isotope data from the South Ellwood section document a trend of C-13 enrichment on the order of 1% which closely follows, but slightly lags, deposition of richest organic strata. Distinct enrichment in [delta]O-18 begins near the peak of maximum carbon enrichment, and continues into the upper siliceous facies. Thus, the Monterey Hypothesis is supported by the more basinal South Ellwood record, while rejected in the Naples Beach banktop record.

• OSTI ID: 5935951
• Report Number(s): CONF-921058-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
GEOLOGIC FORMATIONS
GEOCHEMISTRY
MIOCENE EPOCH
PALEOCLIMATOLOGY
CARBON 13
DEPOSITION
GEOLOGIC MODELS
OCEANOGRAPHY
ORGANIC MATTER
OXYGEN 18
PALEONTOLOGY
STRATIGRAPHY
STRONTIUM ISOTOPES
ALKALINE EARTH ISOTOPES
CARBON ISOTOPES
CENOZOIC ERA
CHEMISTRY
DEVELOPED COUNTRIES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOLOGIC AGES
GEOLOGY
ISOTOPES
LIGHT NUCLEI
MATTER
NORTH AMERICA
NUCLEI
OXYGEN ISOTOPES
STABLE ISOTOPES
TERTIARY PERIOD
USA
580000* - Geosciences