Details

Autor(en) / Beteiligte

• Sak, Peter B.
• Gray, Mary Beth
• Ismat, Zeshan

Titel

Significance of the Deformation History within the Hinge Zone of the Pennsylvania Salient, Appalachian Mountains

Ist Teil von

• The Journal of geology, 2014-07, Vol.122 (4), p.367-380

Ort / Verlag

Chicago: University of Chicago Press

Erscheinungsjahr

2014

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Two competing models exist for the formation of the Pennsylvania salient, a widely studied area of pronounced curvature in the Appalachian mountain belt. The viability of these models can be tested by compiling and analyzing the patterns of structures within the general hinge zone of the Pennsylvania salient. One end-member model suggests a NW-directed maximum shortening direction and no rotation through time in the culmination. An alternative model requires a two-phase development of the culmination involving NNW-directed maximum shortening overprinted by WNW-directed maximum shortening. Structural analysis at 22 locations throughout the Valley and Ridge and southern Appalachian Plateau Provinces of Pennsylvania are used to constrain orientations of the maximum shortening direction and establish whether these orientations have rotated during progressive deformation in the Pennsylvania salient’s hinge. Outcrops of Paleozoic sedimentary rocks contain several orders of folds, conjugate faults, steeply dipping strike-slip faults, joints, conjugate en echelon gash vein arrays, spaced cleavage, and grain-scale finite strain indicators. This suite of structures records a complex deformation history similar to the Bear Valley sequence of progressive deformation. The available structural data from the Juniata culmination do not show a consistent temporal rotation of shortening directions and generally indicate uniform, parallel shortening directions consistent with the single-phase model for development of the Pennsylvania salient.