A comparative study of the sedimentary organic matter of the Monterey Formation in two different basins by compound-specific isotope analysis
- Netherlands Institute for Sea Research, Texel (Netherlands); and others
An organic geochemical study of two time-equivalent sections of outcrops [Naples Beach (NB) and Shell Beach (SB)] of the Monterey Formation from different basins was undertaken. A similar difference in C-content of the S-bound C{sub 35} hopane (cyanobacteria) and cholestane (algae) was found in the SB section compared to the time-equivalent part of the NB section. This indicates that the differences in the carbon isotopic composition of these compounds is caused by a general phenomenon (an influx of cool, CO{sub 2}-rich bottom waters in the Miocene Pacific ocean) and not by local changes. The carbon isotopic composition of dinorhopane in SB sediments varies in a similar manner as that of the dinorhopane of NB sediments though in different time-sections, indicating different bottom water conditions in the two basins at different time intervals. Compounds derived from diatoms in SB sediments are isotopically very different compared to those in NB sediments indicating the presence of different species with different physiological behavior. The carbon number predominance and the carbon isotope data of the free n-alkanes suggests a terrestrial source in NB sediments in contrast to SB-sediments indicating that the terrestrial input in SB sediments was low. The results demonstrate that the depositional environments of two Monterey basins were affected in the same way by global climatic changes but that significant differences in organic matter input occur.
- OSTI ID:
- 425854
- Report Number(s):
- CONF-960527--
- Country of Publication:
- United States
- Language:
- English
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