|
Mary Beth Gray
Associate Professor of Geology
|
|
Pedogenic slickensides, indicators of strain and deformation processes in redbed sequences of the Appalachian foreland
Mary Beth Gray, Department of Earth and Environmental Sciences, University of Rochester, Rochester NY 14627 Richard Nickelsen, Department of Geology, Bucknell University, Lewisburg, PA 17837
Abstract Pedogenic slickensides are convex-concave slip surfaces that form during expansion/contraction in expansive clay soils such as Vertisols. In the central Appalachians, they occur near the tops of fining-upward cycles in Paleozoic redbeds such as the Bloomsburg, Catskill, and Mauch Chunk Formations. Pedogenic slickensides are found in association with other pedogenic (or paleosol) features such as clay-skinned peds, in situ calcareous nodules, and root impressions. Repeated movements along these shear planes during pedogenesis produce strongly aligned clay particles adjacent to pedogenic slickensides; as a result, they are preserved as discrete fractures throughout diagenesis, compaction, and superimposed tectonic deformation. During whole-rock deformation, pedogenic slickensides segregate penetratively deformed rocks into independent, foliated packets and serve as discontinuities that are followed by later structural features. Because the original morphology of pedogenic slickensides is known, they can be used as crude strain markers.
| |