Organic Geochemistry of Precambrian Sedimentary Rocks

Organic geochemistry of impactites from the Haughton impact structure, Devon Island, Nunavut, Canada

“…Furthermore, Proterozoic (Summons et al, 1988), Neoproterozoic (Logan et al, 1997;Hö ld et al, 1999) sediments often contain n-alkanes with carbon numbers greater than C 23 . Heavy n-alkanes in rocks of this age could be derived from specific types of bacteria or algae, or possibly graptolites (Imbus and McKirdy, 1993). Studies of n-alkane distributions in sediment cores show that sediments become enriched in higher carbon number n-alkanes with depth (Rieley et al, 1991), and it is possible that this could lead to phytoplankton-derived organic matter becoming enriched in >C 20 n-alkanes.…”

Biomarkers (molecular fossils) as geochemical indicators of life

“…Cyclic and branched hydrocarbons, acids and other heterocompounds (e.g., terpenoids) are generally stable over longer geological periods and thus are useful indicators of biosynthesis in an older rock record. The utility of biomarkers as indicators of biological, paleoenvironmental and geochemical processes on Earth has been widely accepted (e.g., Brassell, 1992;Imbus and McKirdy, 1993;Johns, 1986;Mackenzie et al, 1982;Mitterer, 1993;Peters and Moldowan, 1993;Simoneit, 1998;Simoneit et al, 1986, and references therein). The commonly encountered compounds with the typical methods for their analysis have been summarized elsewhere (Simoneit, 2002).…”

A review of current applications of mass spectrometry for biomarker/molecular tracer elucidations

“…The utility of biomarkers as indicators of biogenic, paleoenvironmental, and geochemical processes on Earth has been widely accepted (Didyk et al, 1978;Mackenzie et al, 1982;Johns, 1986;Simoneit et al, 1986;Brassell, 1992;Imbus & McKirdy, 1993;Mitterer, 1993;Simoneit, 1998, and references therein). The detailed characterization of biomarker mixtures in terms of sources and degrees of alteration permits the assessment of: (a) extant life and major contributing species, and (b) extinct life, major contributing species and geo/hydrothermal alteration.…”