Lycopane
Lycopane (C40H82; 2,6,10,14,19,23,27,31-octamethyldotriacontane), a 40 carbon alkane isoprenoid, is a widely present biomarker that is often found in anoxic settings. It has been identified in anoxically deposited lacustrine sediments (such as the Messel formation and the Condor oil shale deposit). It has been found in sulfidic and anoxic hypersaline environments (such as the Sdom Formation). It has been widely identified in modern marine sediments, including the Peru upwelling zone, the Black Sea, and the Cariaco Trench. It has been found only rarely in crude oils. Biological origins The pathway for production of lycopane has not been conclusively identified. There are several theories for its origins/production. Methanogenic archaea Some of the earliest theories for the biosynthesis of lycopane center around it being anaerobically produced by methanogenic archaea. Lycopane has been observed in recent marine sediments in contexts where methanogenic activity is occurring. In older sediments, methanogenic activity is harder to conclusively determine, as methane can migrate from other layers and not necessarily be a product of that geological time. It is possible that isoprenoid alkanes such as lycopane serve as biomarkers for methanogenesis and methanogenic archaea. Lycopane has not yet been directly isolated in any biological organism, so its linkage to