Variability in biomarkers of different saline basins in China |
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| Authors: | Ruiliang Wang Jiamo Fu |
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| Institution: | (1) Biogeochemical Laboratories, Department of Geological Sciences, Indiana University, 47405 Bloomington, IN, USA;(2) Organic Geochemical Laboratory, Institute of Geochemistry, Academia Sinica, 510640 Guangzhou, PRC;(3) Present address: Division of Energy Science and Technology, Department of Applied Science, Brookhaven National Laboratory, Building 801, 11973 Upton, NY, USA |
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| Abstract: | 42 samples (sediments and crude oils) from 5 different saline/hypersaline basins of China were examined using variety of geochemical
techniques. A pronounced even over odd distribution ofn-alkanes is observed for the Ejinur, Jianghan samples. Abundance of isoprenoid alkanes, dominated by phytane (C20 up to 20 per cent in EOM), and C25 and C30 components is another outstanding feature of these studied lacustrine hypersaline settings, indicating important contributuions
from archaebacteria. Gammacerane is a major component of some Eocene Jiangham samples and Cretaceous Taian sediments. Absolute
concentration of phytane and gammacerane appears to be linearly related to chlorine and residual (reduced) sulfur contents
of sediments from Jianghan basin, suggesting sulfur incoporation might have played an important role in the enhacement of
these biomarkers in the anoxic hypersaline, alkaline settings. Wide range of organic sulfur compounds in immature samples
of Jianghan Basin reflects a significant pathway for sulfur incorporation under hypersaline, extremely anoxic/reducing conditions,
although for some structures a direct origin from some sulfur archaebacteria can not be excluded. Brackish salt marsh sediment
and oil from Lenghu depression contain abundant lupane, strong OEP inn-alkane series, and predominance of C29 steranes, suggesting a markedly input from vascular higher plants. The marginal marine evaporate sediments from the hypersaline
Triassic Yangtze Platform is unique for its predominant, complete series of isoprenoid alkanes up to C36 (abundant) and C40 (trace). These long-chain isoprenoids are probably derived from phytoplanktons in addition to archaebacteria. The marked
difference in biomarker distributions from the various suites of samples support that application of these biomarkers to help
effectively characterize different saline basins. The molecular variation is, however, not only due to their discrepancy in
biological sources, but also the extension of sulfate reduction and the availability of metal ions during early diagenesis. |
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| Keywords: | biomarker palaeoenvironment salinity salt lake sulfur |
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