Bituminous and Other Organic Substances in Precambrian of Minnesota

Samples of fine-grained Precambrian sedimentary rocks in northern Minnesota have yielded by extraction small quantities of probable hydrocarbons, asphaltenes, and other bituminous substances. Early Precambrian (Knife Lake) Thomson slate yielded approximately 200 ppm of bitumens, nearly all of which is colorless oil possibly consisting of hydrocarbons. Later Precambrian (Animikie) Rove argillite contains 180 ppm of bitumens which in large part remain adsorbed on alumina in chromatography and are mainly non-hydrocarbons; Rove graywacke, however, yielded 450 ppm of bitumens, possibly including hydrocarbons. Animikian Cuyuna ferruginous and manganiferous argillite has 380 ppm of bitumens, low in presumed hydrocarbons and with more asphaltenes than the other samples. Elemental sulfur was present in one of the Cuyuna chromatographic fractions, but was not detected in the other samples. Hydrochloric acid and sulfuric acid extracts and hydrolyzates of samples of Rove argillite and Thomson slate were separated by paper chromatography and were found to contain substances related to amino acids and aldehydes, the latter probably representing sugar degradation products. Similar material is present in humic acid. Discussion is given of possible source materials and subsequent changes that may have taken place in the organic matter.