DEGLACIAL TO HOLOCENE SEDIMENTATION AND SURFACE PROCESSES IN ONEIDA LAKE: PRELIMINARY SEISMIC STRATIGRAPHY

Oneida Lake is the largest inland lake in New York and served as a depocenter for proglacial Ontario Lobe sediments during the mid-last deglaciation. We present results of a preliminary CHIRP high-resolution seismic reflection survey of the Oneida Lake subbottom as part of an ongoing detailed stratigraphic study of deglacial to late Holocene Oneida basin deposits. Of primary interest in these data is a diversity of thick, layered sediments cut by abundant channels. Above a high-relief acoustic basement, which we interpret as drumlinized subglacial till, high-amplitude draping reflectors demonstrate crude to excellent stratification and locally high-continuity. These sediments likely represent the early stages of a growing Glacial Lake Iroquois, when proglacial melt delivered seasonally varying grain sizes. Both vertical-walled and lenticular channels dissect this material. Channel location and orientation commonly parallel the modern subaerial drumlin field adjacent to the lake. Above this deglacial sequence, low-amplitude, stratified draping reflections transition into acoustically transparent ponded sediments. We interpret this to signify the shift from distal proglacial sedimentation to organic-rich, Holocene accumulation. Spatially variable erosional truncation is observed in all sequences below the acoustically transparent unit, likely due to fluctuations in Glacial Lake Iroquois volumes according to varying meltwater influx. Accordingly, Oneida Lake stratigraphy possesses exemplary potential for high-resolution (annual to decadal scale) reconstruction of Ontario Lobe ice margin behavior, in addition to a continuous record of deglacial to late Holocene sedimentation.