PALEOENVIRONMENTAL INTERPRETATIONS BASED ON MOLLUSK SHELL MORPHOLOGY ALONG THE SOUTHERN MARGIN OF THE LAURENTIDE ICE SHEET, WESTERN NEW YORK

A mollusk community from Western New York provides insights into the aquatic paleoenvironment along the southern margin of the Laurentide Ice Sheet. The Glacial Lake Tonawanda basin lies between the Lockport and Onondaga escarpments in Western New York, spanning a region nearly 60 miles across, and draining westward into the Niagara River. Tonawanda sources are interpreted as being from proglacial and periglacial tributaries from the retreating Laurentide Ice Sheet sheet. Lacustrine sediments consist of a basal till, overlain by approximately one to three meters of clay, grading into a marl that is overlain by up to 8 meters of peat. Lacustrine, riverine and terrestrial mollusk species have been identified within the Lake Tonawanda sediments. Gastropods have been identified to the species level from plates of type specimens and definitive texts. Morphometric variations indicate sensitivities for some species, and provide interpretations of habitat and water chemistry preferences. Many of the identified species persist in the modern Great Lakes region, allowing for comparisons with modern environments. In many cases, modern species indicate migration of environments with climate warming, revealing the relationships between hydrologic and biologic factors. A few species are sensitive to water chemistry, including Helisoma anceps, which is a pioneer species that requires carbonate-rich waters for shell production. Shell mutations indicate the onset of stressed conditions, including high sedimentation, oxygen depletion, and decline of food source in Glacial Lake Tonawanda. The general trends of appearance and disappearance of species within the lacustrine sediment record provide interpretations of lake shallowing and ultimate eutrophication.