Paleoclimatic Implications of Late Pleistocene Marine Ostracodes from the St. Lawrence Lowlands

Abstract

Marine and brackish-water ostracods are common in upper Pleistocene post-glacial Champlain Sea deposits of the St. Lawrence Lowlands of Quebec, Ontario, New York and Vermont. Using modern zoogeographic data and inferred temperature ranges for Champlain Sea ostracod species, bottom water paleotemperatures were estimated for 3 phases of deposition of this inland sea. At least 5 Champlain Sea species are today restricted to frigid/subfrigid climatic zones; at least 2 other species are restricted to cold-temperate zones. The temporal distribution of these and other environmentally diagnostic species in Champlain Sea deposits reveals a significant local climatic change in the Champlain Valley from frigid/subfrigid to cold-temperature marine conditions about 11,000-10,600 yr B.P. In more northern and western regions of the Champlain Sea, closer to the Laurentide ice margin, frigid to subfrigid conditions persisted for slightly longer. Oceanographic changes in the Champlain Sea are correlated with major deglaciation events recorded in the North Atlantic. The taxonomy of Champlain Sea ostracods is described to serve as a systematic base for future study of Quaternary North American faunas. Species [35] are illustrated in scanning electron photomicrographs.