Biomarkers in the Molar Tooth (MT)-bearing limestones in the Jilin-Liaoning area of China

The origin of Molar Tooth(MT) carbonates has been argued for more than 100 years, which are a kind of Proterozoic carbonates especially composed of microsparite with ptygmatically folded and sheet-like structures. Biomarkers detected in the microcalcsparite from the Wanlong and Xingmincun formations in the Jilin-Liaoning area showed there are abundant normal alkanes, isoprenoids, hopanes, steranes, alkylmethylcyclohexanes, and alkylcyclohexanes, indicating a diversity of biological source: long-chain isoprenoids, the major components of chlorophyll, such as C^sub 19^, C^sub 20^, a kind of major biomarkers synthesized early by isoprenoid monomers; hopanes a type of characteristic biomarkers from prokaryote, such as archaebacteria and cyanobacteria; sterane a biomarker for eukaryote; and two kinds of alkanes with C^sub 17^, C^sub 18^ as the main peaks representing aquatic bacteria and with C^sub 23^, C^sub 24^ as the main peaks representing fungi, respectively. Biomarker analysis showed that MT is the result of bacterial and algal activities, which is a kind of organisms between aerobic and anaerobic bacteria, reproducing well in normal or slightly saline sea water under weak oxidation-reduction conditions, resulting in rapid deposition of calcite as microsparite due to some mechanisms.[PUBLICATION ABSTRACT]