DEPTH TO BEDROCK FROM A 3D GRAVITY SURVEY OF A PALEO-VALLEY, GLACIAL LAKE GENESEO, LIVINGSTON CO., NY

Much of western New York’s landscape has been shaped by the Pleistocene glacial advance and retreat of the Laurentide Ice Sheet, which carved the Finger Lakes within the region. The Middle and Late Wisconsin glaciations from ~35,000-12,000 years ago have since filled in some of these lakes, including Glacial Lake Geneseo (previously the region’s westernmost Finger Lake), with glacial till and sediment fill from the Genesee River. Glacial Lake Geneseo was a proglacial lake dammed by the Fowlerville Moraine to the north in Avon and bounded by bedrock valley walls in Dansville to the south. The lake spanned 35 km in length, with a total area of 135 km² at its 189 meter highstand. The less consolidated glacial till and fluvial sediment filling this paleo-valley has a lower density than the surrounding shale and limestone. This density contrast creates a local gravitational anomaly, which was measured using a Lacoste and Romberg gravimeter. The buried paleo-valley is clearly visible in the preliminary analysis of the Bouguer anomaly with a total range up to 35 mGals displaying relative highs along the west and east valley walls, and the lows characterizing the center of the valley. Terrain correction of these data will provide an opportunity to quantitatively estimate the depth of the bedrock valley and sparse well logs can be used to test these model results. A valid structure contour map of depth to bedrock will be useful for hydrologic processes in the largely agricultural community, as well as assistance in the planning of local mining efforts.