GLACIER-STRIATION ANALYSES FROM TALCVILLE, WESTERN ADIRONDACKS, NY: EVIDENCE OF AN EARLY WISCONSIN GLACIER ADVANCE?

Early Wisconsin glacial advance data are uncommon across North America due to subsequent weathering, erosion and covering by retreating ice. Thanks to prospecting of Gouvernuer talc deposits in the late 1980’s, approximately 0.3 hectares of freshly exposed, striated talc-tremolite schists are available for analyses. The Talcville pit, geologically, is part of the greater Frontenac Axis, which geomorphologically represents a hectometer-scale northeast-southwest ridge-and-valley system. 305 negative, streamlined forms (Type-2 striations) and 54 joints were measured on six polished whalebacks or medium-scale stoss-and-lee structures. Using Stereonet 8 and EZ-ROSE programs, these data were analyzed using circular statistics for uniformity. Based on Kuiper, Watson and Rayleigh tests, both striation and joint data were non-uniform and unimodal at the 99% confidence level with mean vector orientations of 018° and 054°, respectively. A total of 202 striation-widths were measured along 1-meter sections for each main exposure. Of these data, 98% are between 1-9mm in width with the remaining 2% >10mm. Interpretation of the striation vector reveals that glacier flow was to the south and at an acute angle to both bedrock topography and joints (~36° offset); thereby, suggesting that ice flow across this portion of the Adirondacks was not bedrock controlled at the hecto-meter scale. Based on regional geology hardness estimates, we also extend the striation-flow estimate “up ice” to an approximately 10° wedge. This wedge could source striators hard enough to form a striated and polished surface atop this tremolite schist; therefore, supporting southerly flow out of the St. Lawrence River valley between Canton and Colton, NY. Regarding basal-debris, up to 14% of the basal ice was functioning striators. Provenance tracing and the lack of local topographic control suggest that these striations were the result of an early Wisconsin ice advance during a healthy, full-glacial mode. Thanks to mineral prospecting, minor deflection of ice advance around the Adirondacks has been supported; moreover, elusive early Wisconsin data are out there – just covered by later, retreat materials.