The late quaternary oxygen-isotope composition of Southern Lake Huron

Meltwater events that affected Lake Huron during the last 12,000 years using the oxygen-isotope records provided by ostracodes have been identified. Three sediment cores were collected from Lake Huron; two from the Goderich Basin and one from the southern Manitoulin Basin. At certain times, these regions were isolated from each other and from other basins in the lake. The oxygen-isotope values obtained for the ostracodes indicate large variations in the composition of lake water, as has been reported elsewhere in Lake Huron. Lake Huron was inundated at least three times by water with very low delta O-18 values (similar to-20 versus similar to-7.5% for modern Lake Huron water). This low-O-18 water originated from the retreating Laurentide ice sheet. It was likely derived from proglacial Lake Agassiz, and may have been released during very short intervals of time. Other periods were characterized by lake water with much higher delta O-18 values, reaching a maximum of -6.1%. Overall, the oxygen-isotope compositions of early Lake Huron water and its precursors are characterized by extreme variations, which arose both from changing sources and regional climate change.