FRACTURE ORIENTATION AND STRUCTURAL ANALYSIS OF THE CHAUMONT LIMESTONE

The Chaumont limestone is of Ordovician age and is characterized by its calcium carbonate content (98%) and its formation of limestone pavements in Jefferson County, NY. The limestone pavements are unique to the area and are known for their large fracture sets. This study focuses on the origin of those fractures. Studies previously done in the area attributes the fractures to be only of glacial origin. These studies claim that glacial unloading created enough stress for fractures to form and that they widened due to dissolution. However, there are pop-up ridges, or chevron folds, in the limestone which indicate compressive tectonic forces were once active on the limestone. These forces may be responsible for the initial formation of fractures, not just glacial unloading. In this study we located three outcrops, measured fracture orientation and dip, and utilized ground-penetrating radar (GPR) to estimate fracture depth. Ranges of glacial load were used to perform a stress-strain analysis to determine the angle of fractures that would form under glacial conditions. These angles were compared with measured field data. Samples of the limestone were cut and polished in order to examine mircrofractures. Thin sections were also analyzed for presence of microstructures that may have formed from glacial unloading and shear stress.