THE GREAT GULLY GROUP: A TIME-STRATIGRAPHIC FRAMEWORK FOR LATE QUATERNARY EVENTS IN THE CENTRAL FINGER LAKES OF NEW YORK STATE

The Finger Lakes region of central New York has long been recognized as an iconic landscape most recently refined by the Ontario Lobe of the Laurentide Ice Sheet. The earlier record of glacial events and the actual age of formation of the Finger Lakes has been studied less and thus are not well known. Detailed geologic field mapping by the New York State Geological Survey as part of an ongoing STATEMAP and Great Lakes Geological Mapping Coalition project has provided the resources to investigate and establish a detailed lithostratigraphic and chronostratigraphic record for deeply buried sediment packages within Great Gully, an expansive east-west oriented gorge on the eastern flanks of the Cayuga Lake near the village of Union Springs in Cayuga County.

Identification of laterally continuous and distinct lithologic units observed from 16 exposures has allowed us to develop a comprehensive type section and confidently assign formal names at the formation and member level lithostratigraphic hierarchy. Newly collected continuous wire-line cores, 50 meters in depth, substantiate continuity and expand the stratigraphic and spatial range of preserved deposits.

Lithostratigraphic units are comprised of alternating packages of diamicton and fluvial\lacustrine facies. The fortuitous abundance of subtill organics provides a metric to establish a robust, internally consistent radiocarbon chronology and assess paleoenvironmental conditions. Strata older than the limits of radiocarbon are constrained by optically stimulated luminescence dating. Together the combined geochronology and lithostratigraphic information provide a unique basis for a chronostratigraphic record of glacial and non-glacial phases in the Finger Lakes spanning Marine Isotope Stages (MIS) 1-5 and possibly beyond.