GRAIN-SCALE STRAIN ANALYSIS OF THE WHALEBACK ANTICLINE, BEAR VALLEY STRIP MINE SHAMOKIN, PENNSYLVANIA: PRELIMINARY RESULTS
Both methods yield finite strain ellipses in the plane of bedding that are generally elongate sub-parallel to the fold axis. In the bedding plane, bulk rock and grain strain ratios range from 1.05 ± 0.02 to 1.24 ± 0.03 and 1.05 ± 0.03 to 1.38 ± 0.06, respectively. Normal to the fold axis, bulk rock and grain strain ratios range from 1.04 ± 0.02 to 1.21 ± 0.03 and 1.08 ± 0.03 to 1.47 ± 0.06, respectively. At the Whaleback anticline, the shape matrix eigenvector method produced more systematic strain patterns than the normalized Fry method. This could be partly due to differences in deformation mechanisms in the sand grains and matrix, matrix heterogeneity, and differences in the precision of sand grain shape approximation. In fold-axis normal profiles, finite grain strain ellipses appear to be sheared towards the hinge of the fold. Our preliminary study of strain patterns on the Whaleback anticline suggests that flexural flow occurred during folding.