RI-41 Bottom Sediments and Organic Geochemical Residues of Some Minnesota Lakes

Abstract

Holocene lake sediments of Minnesota are represented by six facies: I) northeastern-allogenic littoral sand and gravel, and profundal clay and copropel, in Precambrian crystalline rocks, with low to high total carbohydrates, high and variable amino acids, low to moderate hydrocarbons, and low to high pigments; II) northwestern-mixed allogenic clastics, and authigenic copropel and marl, in calcareous glacial drift and Pleistocene lake beds, with moderate carbohydrates, low amino acids, and stratigraphically variable pigments; III) north-central-authigenic marl, copropel, and allogenic sediments in thick calcareous glacial drift, with moderate carbohydrates, low amino acids, and stratigraphically variable pigments; N) east-central-authigenic copropel, marl, and allogenic clastics in calcareous and noncalcareous glacial drift, with high carbohydrates and amino acids, high hydrocarbons and polar lipids, high pigments, all stratigraphically variable; V) west-central and southwestern-allogenic silt, marl, and sapropel in calcareous glacial drift and gypsiferous Cretaceous shale, with high carbohydrates and amino acids, stratigraphically variable, high aromatic hydrocarbons; and VI) southeastern-allogenic fine clastics and copropel in Paleozoic clastic and carbonate rock and pre-Wisconsin drift, with known organic residues similar to those in Facies IV.