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Kinematic and temporal history of brittle deformation in the Blue Ridge province, north central Virginia
Cox, Mary Catherine
Cox, Mary Catherine
Abstract
The Blue Ridge province in Virginia is a subset of the Appalachian Mountains situated between the Valley & Ridge to the west and the Piedmont to the east. The bedrock of the province includes a Mesoproterozoic granitic basement and Neoproterozoic to Cambrian cover sequence of metavolcanic and siliciclastic rocks. These rocks record several ductile deformation events in the Proterozoic and Paleozoic that are well documented in Blue Ridge literature as well as less examined brittle deformation. In order to quantify and temporally place brittle deformation in the region, we measured brittle fractures during field mapping in the Elkton East 7.5' quadrangle in Virginia and compiled fracture measurements in the region made by previous William & Mary students. Stereograms and rose diagrams were constructed from these data at the outcrop-scale and unit-scale. The basement complex exhibited a varied fracture pattern, but the cover sequence units contained two main fracture sets: a NW-SE striking set and a NNW-SSE striking set. The NW-SE set is interpreted to be late Alleghanian in age due to its similar orientation with a set of that age in the Valley & Ridge province to west. The NNW-SSE set crosscuts older structures and is parallel to a suite of Jurassic diabase dikes in the region and is interpreted to be contemporaneous with these dikes. A linear breccia zone in quartz arenite was also found closely associated and parallel to Jurassic extension fractures and is interpreted to be a dilation breccia that likely formed during Jurassic extension.
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2011-01-01
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Geology