Document Type
Thesis
Abstract
The early Cambrian Antietam Formation in the western Blue Ridge province of Virginia is a well-folded unit of quartz arenite. The purpose of this study is to determine a kinematic model for a mesoscale fold of quartz arenite by conducting a three dimensional strain analysis across the hinge and limbs. The Antietam formation is a medium-grained, well sorted quartz arenite, and is uniform in composition across the fold. Skolithos is common in the fold as well, but serves only as a 2 dimensional strain marker perpendicular to the tubes. The fold is about 150 meters in length, with asymmetric exposed limbs, a sub-angular hinge, and an amplitude of about 100 meters. The microstructures displayed pressure solution, microfractures, deformation bands, and undulose extinction. Strain analysis was conducted using the Rfф and center-to-center methods on quartz grains from the sample thin sections. These strain values give the orientation of the X, Y, and Z axes, as well as the strain ratios between each plane. Most of the samples plotted in the field of apparent flattening, with K values between 0.1 and 1.05. When plotted against volume change, there was a strong linear relationship between K value and volume change. Samples with smaller K values had significantly more volume loss than samples that experienced less flattening. Strain increased away from the hinge of the fold, indicating that a flexural flow model best describes the fold geometry.
Date Awarded
2014
Department
Geology
Recommended Citation
McGrath, Casey, "Kinematic analysis and strain partitioning in a mesoscale fold, Antietam Formation, Blue Ridge Province, Virginia" (2014). Geology Senior Theses. William & Mary. Paper 323.
https://scholarworks.wm.edu/geologyseniors/323
