Publication Date
2014
Description
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 di.rection 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.
Journal
The Journal of Geology
Volume
122
Issue
4
First Page
367
Last Page
380
Department
Geology & Environmental Geosciences
Link to Published Version
http://www.jstor.org/stable/10.1086/675907
DOI
10.1086/675907
Recommended Citation
Sak, P.B., Gray, M.B., and Ismat, Z., 2014, Significance of the Juniata culmination in the deformation history of the Pennsylvania salient, Appalachian Mountains. Journal of Geology 122, 367-380