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Variability in biomarkers of different saline basins in China

Research paper by Ruiliang Wang, Jiamo Fu

Indexed on: 01 Mar '97Published on: 01 Mar '97Published in: International Journal of Salt Lake Research



Abstract

42 samples (sediments and crude oils) from 5 differentsaline/hypersaline basins of China were examined using variety ofgeochemical techniques. A pronounced even over odd distribution of n-alkanesis observed for the Ejinur, Jianghan samples. Abundance of isoprenoidalkanes, dominated by phytane (C20 up to 20 per cent inEOM), and C25 and C30 components isanother outstanding feature of these studied lacustrine hypersalinesettings, indicating important contributuions from archaebacteria.Gammacerane is a major component of some Eocene Jianghan samples andCretaceous Taian sediments. Absolute concentration of phytane andgammacerane appears to be linearly related to chlorine and residual(reduced) sulfur contents of sediments from Jianghan basin, suggestingsulfur incoporation might have played an important role in the enhacement ofthese biomarkers in the anoxic hypersaline, alkaline settings. Wide range oforganic sulfur compounds in immature samples of Jianghan Basin reflects asignificant pathway for sulfur incorporation under hypersaline, extremelyanoxic/reducing conditions, although for some structures a direct originfrom some sulfur archaebacteria can not be excluded. Brackish salt marshsediment and oil from Lenghu depression contain abundant lupane, strong OEPin n-alkane series, and predominance of C29 steranes,suggesting a markedly input from vascular higher plants. The marginal marineevaporate sediments from the hypersaline Triassic Yangtze Platform is uniquefor its predominant, complete series of isoprenoid alkanes up toC36 (abundant) and C40 (trace). Theselong-chain isoprenoids are probably derived from phytoplanktons in additionto archaebacteria. The marked difference in biomarker distributions from thevarious suites of samples support that application of these biomarkers tohelp effectively characterize different saline basins. The molecularvariation is, however, not only due to their discrepancy in biologicalsources, but also the extension of sulfate reduction and the availability ofmetal ions during early diagenesis.