Provenance Dates and Feldspar Fractionation in Late Wisconsin Till of the Cuba Moraine, Ohio

Late Wisconsin till of the Cuba Moraine in Ohio consists of sediment contributed by local Paleozoic bedrock and by the igneous and metamorphic rocks of the Canadian Precambrian Shield. Feldspar in this till is derived predominantly from the Grenville and Superior structural provinces of Canada which are 1.07 b.y. and 2.70 b.y. old, respectively. Rb-Sr provenance dates of feldspar in the — 18 +35 mesh fractions of till range from 1.21 b.y. to 2.01 b.y. and confirm that the feldspar is a mixture of grains from these 2 provinces. The K-feldspar/plagioclase ratio of the — 18 +35 mesh fraction is consistently greater than that of the —120 +250 mesh fraction. This relationship also was seen in the till of the Powell Moraine of Ohio and in Cenozoic till of Antarctica and may be caused by preferential grinding of plagioclase during transport at the base of the ice. The feldspar in the — 18 +35 mesh fraction is enriched in K-feldspar by about 25% compared to feldspar in the — 120 +250 mesh fraction of till in the Cuba Moraine. OHIOJ . SCI. 83 (4): 177-182, 1983