LANDFORMS AND SURFACE GEOLOGY OF EASTERN ONEIDA LAKE AND ONEIDA COUNTY, NEW YORK: NEW INSIGHTS FROM MATCHING BATHYMETRY WITH LIDAR TOPOGRAPHY

Oneida County contains a rich archive of diverse landforms and lake bottom morphology which provide an improved understanding of Late Quaternary paleoenvironments. Lidar topography and a dense grid of digital echo sounding data from Oneida Lake reveal broadly sculpted glacial surfaces of streamlined hills and a reticulate pattern of ground moraine, which are cored with massive diamicton (till). The reticulate pattern of polygonal hills with centric depressions is most similar to basal crevasse fill patterns, which are interpreted as representing late glacial surging of the Ontario Lobe of the Laurentide Ice sheet. Grounding line moraines mark glacial lacustrine conditions (prior to Glacial Lake Iroquois) contemporaneous with crevasse landforms. Esker fan and esker deposits formed along the periphery of the Ontario Lobe as it abutted the southern edge of the Tug Hill. Extensive eolian dune deposits (Rome Sand Plains) developed upon these terraces which were later dissected by incised channels that spread into sandy alluvial fans, within the alluvial plain of the Fish Creek. Beach ridges and capping shoreline dunes developed early on, upon the underlying till surface, and began a series of prograded shorelines that march westward into the modern basin of Oneida Lake. A meandering alluvial plain succession developed in step with the prograding shoreline and records significant changes in discharge and avulsion during the Holocene. A major lowering of lake level is recorded by a disconformity between early shoreline ridges (Glacial Lake Iroquois) and subsequent Oneida Lake shorelines which record renewed inundation of the basin and resumption of shoreline progradation. This is recorded in the lake floor bathymetry by a relict channel which meanders across the lake floor and development of a foreshore sand wedge, that buries the connection between the modern Fish Creek Channel and it’s offshore antecedent. These mapped relationships are constrained by radiocarbon dating of buried logs in the alluvial plain of Fish Creek and uncompromised shell dates from beach deposits. Complementing this are optically stimulated luminescence dates on sand deposits. Additional constraints will be provided by cosmogenic exposure age dating of boulder moraines discovered along the southern perimeter of the Ontario basin and the regional cuesta of Silurian bedrock.