Hydrocarbons of Biological Origin in Sediments about Two Billion Years Old

Abstract

Normal paraffins in the C₁₆ to C₃₂ range and the saturated isoprenoid hydrocarbons, pristane and phytane, have been found in chert from the Gunflint iron formation (1.9 x 10⁹ years old) of the north shore of Lake Superior. The distribution of n-alkanes shows two maxima, one at about C₁₈ to C₁₉ and the other at about C₂₂ with a minimum occurring at C₂₀ to C₂₁. No predominance of odd- to even-carbon-number alkanes is observed within the C₁₆ to C₃₂ 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.