NEOTECTONICS OF THE MCGREGOR FAULT, NY

The McGregor-Saratoga-Ballston Lake fault zone forms the southeastern margin of the Adirondack Mountains, marked by a distinct range front from north of Glens Falls, NY, to Saratoga Springs. The springs of Saratoga Springs are aligned with the Saratoga fault portion of the system. Previous studies suggested that the fault system may have undergone Neogene activation, although evidence is dated and largely inconclusive. This study uses aerial imagery/digital elevation models to analyze the tectonic geomorphology of the mountain front, combined with ground-penetrating radar (GPR), to confirm or deny whether the fault zone has produced significant Neogene and post-glacial tectonic activity. The steep, nearly linear mountain front that coincides with the location of the McGregor fault could be the result of Neogene uplift, with morphology analogous to mountain fronts in tectonically active areas like the western U.S. Alternatively, the morphology of the McGregor fault mountain front may be due to long-term glacial erosion of differentially resistant bedrock. I found that there are slight variations from north to south in the drainage basin areas of the streams draining the range front, as well as slight differences in both overall and lower slope change across the range front. Although much of the morphology is like that which is found in tectonically active mountain ranges, I could not distinguish obvious patterns conclusively indicating a tectonic control on topography. GPR lines gathered across the likely location of the Saratoga fault yielded visualization of subsurface deposits up to 20 meters in depth. I did not find significant changes in stratigraphy from my preliminary analysis that could be attributed to fault offsets, nor any direct imaging of a fault zone within these late-glacial and post-glacial sediments, and post-processing could further confirm this interpretation. Based on these current results and observations, I can say that tectonic deformation has not significantly impacted the glacial/fluvial sediments in the McGregor fault zone (and subsequently MSBL fault system).