Sedimentary 12-n-Propylcholestanes, Molecular Fossils Diagnostic of Marine Algae

Science  19 Jan 1990:
Vol. 247, Issue 4940, pp. 309-312
DOI: 10.1126/science.247.4940.309


Certain C30-steranes have been used for identifying sedimentary rocks and crude oils derived from organic matter deposited in marine environments. Analysis of a C30-sterane from Prudhoe Bay oil indicates that these C30-steranes are 24-n-propylcholestanes that apparently are derived from precursor sterols 24-n-propylidene-cholesterols and 24-n-propylcholesterol. These widely occurring sterols are biochemically synthesized in modern oceans by members of an order (Sarcinochrysidales) of chrysophyte algae. These data thus imply that C30-sterane biomarkers in sedimentary rocks and crude oils have a marine origin. Screening of a few organic-rich sedimentary rocks and oils from throughout the Phanerozoic suggests that these C30-steranes first appeared and, therefore, their source algae evolved between Early Ordovician and Devonian.

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