Carbonaceous Rocks of the Soudan Iron Formation (Early Precambrian)

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Science  25 Jun 1965:
Vol. 148, Issue 3678, pp. 1713-1716
DOI: 10.1126/science.148.3678.1713


Carbon-rich rocks more than 2.7 billion years old, from the Soudan Iron Formation of northeastern Minnesota, contain pyrite balls in which are found microstructures of possible biologic origin. The C13/C12 and S34/S32 ratios and minor element composition of this rock are consistent with such an interpretation. Hydrocarbons of presumed vital origin are also present, although it is not certain that they are endemic to the rock.