Supplemental Material: Quantifying shortening across the central Appalachian fold-thrust belt, Virginia and West Virginia, USA: Reconciling grain-, outcrop-, and map-scale shortening

Abstract

Plate 1. (A and B) Balanced (A) and restored (B) cross section A-A' extending from the eastern Great Valley westward to the Burning Spring anticline (Fig. 1). Total deformed length (274 km) and undeformed restored length (346 km) are measured from a pin line east of the extent of documented map-scale shortening on the Appalachian Plateau, resulting in 78 km (23%) total shortening. (C) As shown, shortening in Upper Devonian through Permian rocks assumes 10% layer-parallel shortening (LPS) in the Appalachian Plateau and across the Appalachian front (to thick vertical bar) and 25% LPS in the Valley and Ridge (region between thick vertical bars). Shortening in the Great Valley requires 35% LPS, compared to the >50% LPS measured in that region (Wright and Platt, 1982). Cross sections drawn with no vertical exaggeration; Circled numbers—duplex numbers; Fm–Formation; Gp—Group. Plate 2. Geologic cross section divided into 16 sequentially numbered intervals (circled numbers above the cross section) spanning from the western limb of the Burning Springs anticline eastward to the Great Valley. Locations of each of the 40 samples used to constrain grain-scale layer-parallel shortening (LPS) are shown as small white dots projected into the line of section; calculated LPS (as a percentage) are shown above each sample. Mean LPS values for each interval are summarized in Table 2. (A) Cross section constructed to minimize the amount of unit thickness variation in the Reedsville-Martinsburg Formations. Balancing this section requires 10% outcrop-scale shortening between the Elkins Valley anticline and the boundary between the Valley and Ridge and Great Valley. (B) Cross section constructed to minimize contributions from outcrop-scale shortening. Balancing this section requires 5% outcrop-scale shortening between the Elkins Valley anticline and the boundary between the Valley and Ridge and Great Valley. Cross sections drawn with no vertical exaggeration; circled numbers—duplex numbers; Fm—Formation; Gp—Group.