A RECORD OF POST-GLACIAL RELATIVE LAKE LEVEL FLUCTUATION IN THE SENECA LAKE BASIN, NY

The post-glacial history of the Finger Lakes, NY has involved several changes in lake levels throughout the late Pleistocene and Holocene, resulting from the changing position of the retreating Laurentide ice sheet, river outlet position, post-glacial rebound, and hydrologic budget. We propose that isostatic rebound has played a larger role in changing lake level than previously recognized. To investigate this hypothesis, we collected a series of cores along a north-south transect in Seneca Lake and the marsh of the Catherine Creek Wetland area south of the lake. Open lake cores (2-5 m long) were collected using a piston corer and wetland cores were collected using a Russian peat borer (2.5 m long), vibra-corer (~4 m long), and truck-mounted hollow stem auger (~25 m long).

Cores were described, photographed, analyzed for magnetic susceptibility, and sampled for loss-on-ignition analyses, grain size analyses, and microfossil identification and quantification. Cores collected from the lake generally contain laminated silt or sand whereas those from the wetland preserve massive silt and sand overlain by peat beds. Cores were correlated using distinctive changes in the profiles of loss-on-ignition, magnetic susceptibility, and grain size. Microfossils preserved in the wetland cores provide a means of estimating water depth. The presence of oogonia (reproductive structures of the aquatic macroalgae Chara) and an abundance of Candona spp. ostracodes in the wetland cores indicate open fresh water with a depth of less than 5 m. If post-glacial isostatic rebound did drive lake level change, we anticipate finding evidence of a transgression in the southern end of the lake and the wetland without a corresponding increase in lake level near the outlet located at the northern end of Seneca Lake.