Relationships between deformation and metamorphism in the western Inner Piedmont, North Carolina
- Univ. of Tennessee, Knoxville, TN (United States). Dept. of Geological Sciences
Geologic mapping conducted in a 700 km[sup 2] area of western NC has revealed the presence of three dominant lithotectonic units of the western Inner Piedmont (IP). These units include in ascending structural order: (1) the Henderson Gneiss (HG), a mylonitic granitic gneiss; (2) the Poor Mountain Formation (PM), which includes biotite gneiss amphibolite, quartzite, and pelitic schist; and (3) the Mill Spring formation (MS) containing biotite gneiss, amphibolite, and pelitic schist intruded by granitoid. Each unit is bordered by a ductile thrust fault, has a fold-nappe style geometry, and was stacked from NW to SE. Metamorphic conditions, as indicated by the presence of sillimanite and muscovite in the pelitic schists of the MS and the PM are upper amphibolite facies. While no pelitic schists occur in the HG, the textural evidence also indicates that metamorphic conditions are upper amphibolite facies. This contrasts with the western Piedmont of SC were metamorphic conditions in the PM and the HG were upper greenschist to lower amphibolite facies. An episode of retrograde metamorphism is indicated by the presence of chlorite in widely scattered parts of the MS and the PM and is not associated with any tectonic fabric. The study area has undergone one major episode of deformation that was contemporaneous with metamorphism and emplacement of thrust sheets. The wide separation arc shown by the analysis is due to a change in transport direction indicated by the change in orientation of lineations and shear-sense indicators from E-W toward the SE to NE-SW toward the NW. This change in the lineations and shear-sense indicators is related to synmetamorphic combined westward thrusting of IP thrust sheets and early or middle Paleozoic dextral motion on the Brevard fault zone.
- OSTI ID:
- 5591115
- Report Number(s):
- CONF-921058-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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