Penobscot and Taconic events in the central Appalachian Piedmont, northern Virginia-Maryland
Conference
·
· Geological Society of America, Abstracts with Programs; (United States)
OSTI ID:6888057
- Geological Survey, Reston, VA (United States)
The central Appalachian Piedmont between the Occoquan River in Virginia and Liberty Reservoir in Maryland is characterized by tectonic motifs of precursory melange-thrust sheet pairs. In Virginia, the lowest tectonic motif (Indian Run-Melange-Annandale Group) (IA) is overlain by the Sykesville melange-Mather Gorge formation tectonic motif (SM), which is overlain by the Yorkshire melange-Piney Branch Complex tectonic motif. The Piney Branch is a tectonic melange of ultramafic and mafic rocks. The thrust sheets were deformed and metamorphosed prior to emplacement above their melanges. Hornblende from second generation amphibolite within the Mather gorge Formation cooled beneath 500 C isotherm at about 490 Ma. The assembled tectonic motifs were folded before emplacement of the Falls Church Intrusive Suite (481 Ma) and Occoquan Granite (479 Ma) that constitute part of a magmatitic arc in the area. In Maryland, the SM is tectonically underlain by the Laurel melange-Loch Raven Schist tectonic motif (LL), which appears to be more proximal in origin. These tectonic motifs are, in part, separated by a shear zone that experienced early sinistral strike slip and later dextral strike slip. Both tectonic motifs are intruded by the Kensington Tonalite (543 Ma), which experienced both the sinistral and dextral shear. This shear zone separates the LL from the IA, and their relation is unknown. All the motifs are interpreted to have been assembled during the Penobscot orogeny in an oceanic trench an unknown distance from the Laurentian margin.
- OSTI ID:
- 6888057
- Report Number(s):
- CONF-9404221--
- Conference Information:
- Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 26:4
- Country of Publication:
- United States
- Language:
- English
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