Sedimentary Hydrocarbons, Biomarkers for Early Life

Molecular biological markers, or biomarkers, are natural products that can be assigned to a particular biosynthetic origin. For environmental and geological studies, the most useful molecular biomarkers are organic compounds with high taxonomic specificity and potential for preservation. In other words, the most effective biomarkers have a limited number of well-defined sources; they are recalcitrant against geochemical changes and easily analyzable in environmental samples. Accordingly, biomarkers can be proxies in modern environments as well as chemical fossils that afford a geological record of an organism’s activities. One of the first significant outcomes of biomarker research was Treibs’ (1936) recognition of unquestionable biological signatures in sedimentary organic matter. Subsequent research (Eglinton and Calvin, 1967; Eglinton et al., 1964) pursued the concept that biomarkers can provide information about the nature of early life in the absence of recognizable fossils and that petroleum is composed of biological remains (Whitehead, 1973). As of early 2000s, thirty years of accumulated facts about sedimentary organic matter are clearly commensurate with the aforesaid and falsify the hypotheses (e.g., Gold, 2001) about the primordial origins of petroleum and natural gas. Largely as a result of efforts to understand the detail of the transformation of biogenic organic matter into petroleum (Hunt, 1996; Tissot and Welte, 1984) and individual chemical fossils, geochemists began to appreciate the value of biomarkers as tools for environmental research (e.g., Brassell et al., 1986) and their potential for elucidating biogeochemical processes (e.g., Hinrichs et al., 1999; Kuypers et al., 2003). The structural and isotopic information.