Microfabric analysis of the Appalachian basin Williamson and Willowvale shales

Shale samples from the Williamson and Willovale formations (Upper Llandoverian, Silurian) were studied to determine the relationship of microfabric (particle orientation) to sedimentary environment and processes. The shales were sampled along a traverse from Utica to Rochester, New York in the Appalachian foreland basin. Samples were taken from proximal and distal parts of the basin and analyzed using a scanning electron microscope (SEM) and using thin sections to determine the relationship between microfabric and basin position. Results show samples taken from the proximal part of the basin contain large amounts of silt grains, random orientation of clay flakes, and a high degree of bioturbation. Basinward, the samples become less silty, less bioturbated, and have more preferred orientation of clay flakes. The samples at the basin axis show the highest degree of preferred orientation and contain no silt grains. It can be concluded that the shale fabrics vary basinward and microfabric analysis is useful in determining the relative position of samples within a sedimentary basin.