Geology of the Peaks of Otter area, Bedford and Botetourt counties, Virginia

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Virginia Polytechnic Institute


The Peaks of Otter area includes two-thirds of the fifteen-minute Peaks of Otter quadrangle in the Blue Ridge and Piedmont physiographic provinces of central Virginia.

The rocks of the area are mainly early Precambrian igneous, metasedimentary, and meta-igneous formations, which are cut by small Triassic(?) dikes and locally covered by Quaternary deposits. All the Precambrian formations are part of the Virginia Blue Ridge Complex. The Marshall Gneiss, believed to be the oldest formation, is in part metasedimentary but also has been extensively modified by granitization processes and intruded by granitic rocks. A few parallel bands or actinolite schist in the Marshall probably were basic flows, stills, or tuffs in the original sediment. The Lovingston and Moneta Formations, the second and third oldest formations, respectively, are mainly metasedimentary. The Pedlar Hypersthene Granodiorite is considered the youngest tonnation and consists chiefly of hypersthene granodiorite of igneous origin but includes rock types near its contacts which are probably hybrid varieties.

The formations crop out in parallel, northeast-trending belts located on the crest and southeast limb of the Blue Ridge anticlinorium. All the metasedimentary formations dip southeastward, possibly as a series or tightly folded, isoclinal folds, or as beds repeated by faulting, or as a homocline. The Peaks of Otter fault, striking northeast along the Blue Ridge, could be either reverse or normal, but reverse is favored. Another inferred reverse fault, the Suck Mountain fault, is believed to expose rocks of the Marshall Gneiss which were more deeply buried and granitized than those exposed elsewhere in the Piedmont of this area.

The metasedimentary formations were deformed and metamorphosed during the Precambrian. The Pedlar Hypersthene Granodiorite was emplaced relatively late after most of the deformation had ceased. A younger sequence of Precambrian formations is southeast of the area but presumably was either not deposited or has been eroded from this area. During the Paleozoic the Blue Ridge overthrust developed northwest ot the area and the Peaks of Otter and Suok Mountain reverse faults probably formed more or loss at the same time, Succeeding cycles of erosion and uplift caused the development of the Schooley peneplain, then the Piedmont peneplain, and, most recently, rejuvenation ot streams. Evidence of the peneplains in this area includes low-relief uplands in the Blue Ridge representing peneplain remnants and a gently-rolling surface in the Piedmont now being dissected by rejuvenated streams. Small ice caps or periglacial conditions may have existed in the Blue Ridge during the Pleistocene causing increased erosion and stream flow which resulted in the deposition or large, fan-shaped sedimentary bodies along the southeastern base of the Blue Ridge Mountains.

The only mineral resource or importance in the area is feldspar, which is quarried from both pegmatite and fine-grained, feldspathic dikes in the Suok Mountain area