SEISMIC STRATIGRAPHY OF ONEIDA LAKE, CENTRAL NEW YORK, A REMARKABLE YET UNRECOVERED LATE QUATERNARY PALEOCLIMATE ARCHIVE

Oneida Lake is the largest inland lake in New York State and is generally accepted as representing the Holocene remnant of Glacial Lake Iroquois, the late glacial impoundment formed as the Ontario Lobe of the Laurentide Ice Sheet retreated into the St Lawrence Lowland approximately14, 500 years ago. It is surprising that little information has been brought forward regarding the paleo depth and sediment infill of Oneida Lake, in particular considering its role as an early catchment for Glacial Lake Iroquois. Preliminary studies using ultra-high frequency (200 to 80 kHz) echo sounders conducted over the last few years were encouraging, with resolution of several tens of meters of reflective strata revealed by simple "fish finding" instruments. To provide data more suitable for evaluating the deeper stratigraphy of the lake we conducted a surface towed CHIRP survey of the eastern half of Oneida Lake in the summer of 2013. Our results demonstrate a remarkable seismic stratigraphy which includes clear resolution of several seismic sequences including: a fluted and drumlinized glacial reflector (serving as acoustic basement), a crudely stratified but high amplitude package of draping reflectors, a very well stratified set of parallel and draping reflectors, a low amplitude and discontinuously stratified set of draping reflectors and a ponded, acoustically transparent sequence. Total sediment infill is well in excess of 100 m with loss of attenuation of all acoustic signals below this depth. Hence, the total thickness of sediment infill within the basin of Oneida Lake likely exceeds 150 m. We interpret the set of acoustic sequences with respect to the recession of the Ontario Lobe and associated glaciolacustrine sediment infill which produced a variety of draping sequences. The most recent, ponded sequence, represents establishment of modern, organic-rich sedimentation. Several of these sequences exhibit erosional truncation, thus indicating fluctuations in lake level during the glacial phase as well as unusual acoustic interbeds of transparent nature (these are not fully understood). Hence, Oneida Lake offers a new paleoclimate archive of exceptional preservation which contains a continuous time series from the late glacial up to and including the modern warming interval.