Hydrocarbons of Biological Origin in Sediments about Two Billion Years Old

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Abstract
Normal paraffins in the C 16 to C 32 range and the saturated isoprenoid hydrocarbons, pristane and phytane, have been found in chert from the Gunflint iron formation (1.9 × 10 9 years old) of the north shore of Lake Superior. The distribution of n -alkanes shows two maxima, one at about C 18 to C 19 and the other at about C 22 with a minimum occurring at C 20 to C 21 . No predominance of odd- to even-carbon-number alkanes is observed within the C 16 to C 32 range. The results agree with micropaleontological observations made on the Gunflint chert and provide a chemical characterization of Precambrian life existing about two eons ago.