SUBGLACIAL LAND SYSTEM EVOLUTION: INSIGHTS FROM NORTHERN CAYUGA COUNTY, NEW YORK

Long recognized as an exemplary locality for drumlins, northern Cayuga County in central upstate New York contains a plethora of equally spectacular glacial landforms whose context has not adequately been studied. Current geologic mapping investigations by the New York State Geological Survey in conjunction with LiDAR terrain models of the Montezuma Wetland Complex has revealed new insights into the landform distribution, subglacial processes and chronology associated with the development of the sediment-landform assemblages present.

During the Late Wisconsin the Ontario Lobe of the Laurentide Ice Sheet crossed the Ontario lowlands and developed a suite of subglacial landforms that rise southward toward the northern edge of the Alleghany Plateau and Finger Lakes in central New York. These well preserved subglacial landforms include tunnel channels, drumlins and well developed eskers. Drumlins display a wide array of morphology and range from less than one kilometer in length to more than eight and range in height from ten to fifty meters. Broad poorly defined channels ranging from one-half kilometer to upwards of two kilometers in width are interpreted to represent tunnel channels. Eskers present occur as continuous and beaded segments five to twenty meters high and extend for lengths of up to fifteen kilometers.

The majority of tunnel channels, eskers and drumlins have experienced erosional modification and or burial by either younger proglacial lake processes or deposits, or discontinuous ice marginal deposits of the Ontario Lobe. Cross-cutting relationships suggest initiation of drumlins appears to have occurred previously or contemporaneously with tunnel channel formation. Micro-fabric and macrofabric on diamictons comprising the drumlins strongly suggests that drumlin formation occurred under deforming bed conditions.

Northeast to southwest orientation of eskers oblique to drumlins are interpreted to represent a shift in subglacial hydrology associated with the Ontario Lobe as a result of changing ice dynamics. Further, LiDAR terrain models display well developed glaciofluvial fans at the terminus of esker segments that showcase ice marginal recession in a landscape dominated by streamlined landforms.