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Characteristics of biomarkers in the Recent sediment from Qinghai Lake, northwest China

Authors
Journal
Journal of Asian Earth Sciences
0743-9547
Publisher
Elsevier
Publication Date
Volume
5
Identifiers
DOI: 10.1016/0743-9547(91)90019-t
Disciplines
  • Chemistry
  • Earth Science

Abstract

Abstract The occurrence of biomarker hydrocarbons in the Recent sediment of Qinghai Lake was investigated. It was found that the distribution of these biomarkers in Qinghai Lake, a semi-saline water lake, is unusual. The distribution of n-alkanes is predominated by high carbon-numbered alkanes with a high OEP (CPI) value. Two series of bicyclic sesquiterpanes derived from micro-organisms, e.g. algae or bacteria, were detected. The occurrence of tricyclic and tetracyclic terpenoids is characterized by the input of the organic matter from aquatic organisms. The conversion from hopenes existing in bacteria and blue-green algae into hopanes is put forward in this paper. C 27C 29 regular steranes, 4-methylsteroids, diasteranes, pregnanes, norsteroids and secosteranes were found in abundance in the sedimentary samples. Another important contribution of this paper is towards the geochemistry of amino acids in the Recent sediment of Qinghai Lake. The composition, distribution and evolution of the amino acids in the lacustrine sediments will be discussed in detail. It was found that several ratios of different amino acids have a clear diagenesis trend in the two cores studied. The racemization reaction of amino acids and their application in the geochemistry will also be discussed. The racemization of alanine and leucine were employed in this study to calculate the age of the sediment samples, with satisfactory result.

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