ERROR ANALYSIS OF DEPTH TO BEDROCK DETERMINATIONS FROM GRAVITY SURVEYS ACROSS THE GENESEE VALLEY, LIVINGSTON COUNTY, NEW YORK

Carved by glaciers and molded by modern fluvial forces, the Genesee Valley in Livingston County, New York offers a scenic environment for geophysical surveying to determine the elevation of Devonian aged bedrock below surficial Quaternary deposits. Surveying and calculations were performed with a Worden Gravimeter, a Bad Elf Flex^® Mini, and the software programs QGIS, Microsoft’s Copilot and Excel, and Python v3.12.4. Portions of Fowlerville Road, U.S. Route 20A, and Mount Morris Geneseo Road were chosen because they are oriented nearly perpendicular to the Genesee Valley. Forward modelling methods to determine the bedrock elevation were conducted in Python as well as in Excel using the Solver add-in, and the results were referenced against publications from the New York State Museum for accuracy. Comparison of Python and Excel indicates that the Python based results are more precise. Additionally, Python provided the opportunity to conduct statistical tests to study uncertainties within the model. Initial positional variations in latitude, propagated from the Flex^® Mini unit, and surface elevation, from Digital Elevation Models, were analyzed and the resulting 2σ confidence intervals were calculated for all data points along each survey route. This analysis suggests propagation of uncertainties in the 3D location of the gravity measurements resulting in 2σ confidence intervals for bedrock elevations of ±5.8 meters (Fowlerville Road), ±8.9 meters (Route 20A), and ±2.8 meters (Mount Morris Geneseo Road).