RHYTHMIC SEDIMENTATION IN ANCESTRAL LAKE ERIE: ESTIMATING DURATION ABOVE THE LAKE WARREN LEVEL, NW OHIO

Cores of ancestral Lake Erie sediment were collected from three locations in northwest Ohio to evaluate: 1) the duration of lake levels above Lake Warren; and, 2) test the hypothesis calling for the Ypsilanti low phase. While past water level histories between lakes Maumee and Warren involve numerous transgression and regression events, here we focus on just the history recorded in the sediments. The cores were collected at Stranahan Arboretum, Wildwood, and Oak Openings Metroparks located in the Toledo, OH region. At Stranahan Arboretum cores were collected using a hydraulically assisted Livingstone corer and by hand from cut bank exposures at Wildwood and Oak Openings Metroparks. In general, the cores consist of basal, massive diamicton overlain by ~2­­–4 m of glaciolacustrine sediment and capped by ~1.5–2 m of aeolian sand. The glaciolacustrine sediment consists of units of alternating clay/silt couplets with interbedded units of cross-laminated sand and silt at Stranahan, and at Wildwood, exposed ripple form sets and individual laminae are laterally traceable a minimum 10 m. Magnetic susceptibility, loss on ignition, and particle size analysis of the clay/silt couplets support a varve interpretation. Preliminary varve counts from the Stranahan and Wildwood cores are 137 and 234 varves respectively. Ongoing work will consist of varve counts for the cores collected at Oak Openings and assessing whether changes in lake level are recorded in the sediments. Sedimentation at the sites appears to be continuous without any evidence of a regional unconformity to support the Ypsilanti low phase hypothesis.