Compressional geologic structures in Devonian shales of Lake Erie lakeshore bluffs, western New York скачать в хорошем качестве

Compressional geologic structures in Devonian shales of Lake Erie lakeshore bluffs, western New York

This is a talk that was presented on March 30, 2025 in the Geological Society of America meeting in Erie, Pennsylvania. The talk title is "Thrust faults and folds interpreted as post-glacial pop-ups in Devonian strata of lakeshore bluffs along Lake Erie, western New York State, USA." A compressional structure well exposed and publicly accessible at Ripley Beach, New York may be a structure that was documented and studied by famous American geologists James Hall in 1843 and G.K. Gilbert in 1892. This talk shows cross-sections of small compressional structures in lakeshore outcrops that are interpreted to have formed shallow, after Pleistocene glaciers retreated. In addition, comparisons and contrasts are made with compressional structures in Devonian shale bedrock that are thought to have been formed by shear beneath glaciers (sometimes called "glacial push") or thrust faults and folds that likely formed during deep burial and Alleghanian orogenic compression. The talk shows a published example of stream valley pop-up anticlines in Devonian shale bedrock of Allegany County, New York. An example of a possible stream anticline pop-up fold in Pennsylvanian siltstone of the unglaciated plateau is also shown. That structure crops out in Fall Run Park, Shaler Township, Allegheny County Pennsylvania which is near Pittsburgh. A summary slide suggests common features and recognition criteria for pop-up structures that formed in quarries or in shales at or near the surface of incised stream valleys or open fields of the plateau area. Common features of shallow-formed pop-ups are compared with features of compressional structures that were formed by sub-glacial shear and structures that formed during deep burial, through orogenic compression.