Differentiating compressional structures formed in Devonian shales as shallow pop-ups, by sub-glacial shear, or through orogenic compression in western New York, western Pennsylvania and northern Ohio
Thursday, October 23, 2025
Presented by:
Dr. Fred Zelt
Abstract: Field work along Erie lakeshore cliffs south of Buffalo led to rediscovery of small thrust faults and folds in Devonian shales that are well exposed in cross section. Some of the lakeshore structures were described by Hall (1843), Gilbert (1892), and Grabau (1898). Comparison of these with other contractional structures in Devonian shales in western New York, western Pennsylvania and northern Ohio led to development of criteria to differentiate pop-up structures that formed shallow due to removal of overburden versus structures formed by shear beneath a glacier or that formed through orogenic compression. Shallow-formed pop-up structures occur in shales in post-glacial areas, excavations, and bottoms of incised streams and rivers. Examples discussed in this talk will include stream and river valley pop-up structures in Pennsylvanian strata of the Pittsburgh area.
Agenda:
5:00 pm Social Time
6:00 pm Dinner Buffet
6:300 pm Speaker Presentation
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