UNDERSTANDING NEW YORK STATES BEDROCK TOPOGRAPHY AND DRIFT THICKNESS THROUGH FIELD AND DIGITAL TECHNIQUES

The New York State Museum/Geological Survey’s mission is to expand knowledge of our natural history. To this end, field work accompanies wireline soil coring to collect samples to improve the understanding of New York’s Quaternary stratigraphy. In 2019, we were tasked to map the bedrock topography of the entirety of the state by the Great Lakes Geologic Mapping Coalition. Previous mappings of the bedrock topography were conducted at the county scale over 30 years ago as a means of studying aquifer potential for municipal water supplies spurred from increased urbanization and population. Regional scale maps have not been attempted due to lack of bedrock depth data and complex drift thicknesses across the many ridges and valleys across each region. We began in the Finger Lakes Region due to coincident mapping efforts that had begun in 2009 in Cayuga County up to today in Tioga County. Through the past 14 years of mapping efforts, we have accumulated an abundance of field points of bedrock outcrops and our own exploratory stratigraphic bore hole data to help quantify the bedrock topographic surface. These point data became the backbone for assembling this map. A workflow was developed converting all point data, oil and gas, water, engineering and exploratory stratigraphic well and field stations, into a standardized format. These data points were then converted into a raster and subsequently contoured at 50-foot intervals. Hand adjustments to each contour was required to ensure geological consistency and to correct topological errors using our knowledge of the geology and comparison of the contours to hillshade maps based on LiDAR elevation data. Upon completion of this map, it was abundantly clear that computer modeled topography was grossly inaccurate compared to that of the 100’s to 1,000’s of hours of hand adjustments to the contours. Despite the time investment in manual editing, the complexity of the bedrock surface of the Finger Lakes Region remains enigmatic.