Ostracod faunas in a large Late Pleistocene ice-dammed lake, southern Ontario, Canada
Abstract In the Lake Ontario Basin of mid-continent North America, near Toronto, Canada, a low diversity micro-crustacean (ostracod) community dominated by Candona caudata and Candona subtriangulata occurs in several poorly-sorted pebbly mud (diamicts) units (Sunnybrook, Seminary and Meadowcliffe “Tills”). The diamicts were deposited in an ancestral ice-dammed Lake Ontario, with a level at least 90 m above the modern lake, during the early and middle phases of the Wisconsin glaciation (25,000–75,000 yr B.P.). Poorly-sorted sediments accumulated by ice-rafting and mud deposition from meltwater plumes and are separated by shallower water deltaic facies. Comparison of the modern habitat ranges of ostracods, specifically their water depth, temperature and dissolved oxygen preferences, provides important palaeolimnological data regarding Late Pleistocene ice-dammed lakes.