Date of Award
This study presents a balanced geologic cross section through the Juniata Culmination of the central Appalachian fold-thrust belt. The transect spans 318 km along a northwest trending line from the southern Valley and Ridge physiographic province to a pin line along the southern shore of Lake Erie in the undeformed foreland. This section only balances when grain-, outcrop- and map-scale shortening are considered. Bulk finite strain is quantified for 35 samples along proposed transect using the normalized Fry method to record the magnitude and orientation of the principle axes of the strain ellipsoid. Bulk finite strain results suggest 13% Layer Parallel Shortening (LPS) in the cover sequence of the Appalachian Plateau above the Salina salt décollement and 19% LPS in the Valley and Ridge. Restoration of the section indicates shortening of 107 km in the cover sequence and 108 km in the carbonate sequence. Line length calculations show that a cross section through the Juniata Culmination balances when incorporating calculated values of shortening at a range of scales in the Valley and Ridge and Appalachian Plateau. When restored to an unreformed state, there is a 1 km difference between the line lengths of the cover and carbonate sequences. This cross section combined with other balanced sections through the Appalachian mountains creates an advanced model for the structure and sequence of shortening in the Appalachian fold-thrust belt.
Fisher, James, "Quantifying Shortening in the Juniata Culmination, PA: Insights from a Balanced Cross Section Incorporating Observations at the Grain-, Outcrop- and Map-Scale" (2018). Dickinson College Honors Theses. Paper 305.