Glacial Meltwater in Lake Huron during Early Postglacial Time as Inferred from Single-Valve Analysis of Oxygen Isotopes in Ostracodes

Abstract

δ 18O measurements of benthic ostracodes are used to reconstruct the δ 18O history of Lake Huron and Georgian Bay water between 10,600 and 7600 14C yr B.P. This δ 18O record was calibrated using a comparison of the δ 18O values of modern ostracodes and Lake Huron water, where a fractionation of 1.0358 was measured between the oxygen isotope ratios of the most isotopically positive ostracode Candona subtriangulata and lake water. The most positive shell δ 18O value was used because it is precipitated in the cold (0° to 2°C) water common to both deep and shallow environments. The δ 18O of Lake Huron water reflects a large glacial meltwater component for much of its history before 7600 14C yr B.P. Times of low lake level correlate with the highest ratio of glacial meltwater to local precipitation in the basin (most negative δ 18O values). Georgian Bay water was more negative in δ 18O than Lake Huron water of the same age; this reflects a higher proportion of glacial meltwater in Georgian Bay and its separation from Lake Huron during times of low lake level.