Sedimentary melanges of the central Appalachian

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6644686

Drake, Jr, A A

Crystalline thrust sheets in the central Appalachian Piedmont typically overlie precursory sedimentary melanges forming tectonic motifs. The melanges have quartzofeldspathic matrices, contain an assortment of exotic olistoliths including ultramafic rocks, and each is characterized by a debris of the immediately overlying thrust sheet. The olistoliths are foliated, many are polydeformed, and were polymetamorphosed before the inclusion in the matrix. Subsequently the melange was metamorphosed and deformed again. Olistoliths are rectilinear to lensoid range from small chips to blocks as long as 1.5 km, and lie parallel with the matrix foliation. These melanges have been recognized from Trenton, New Jersey, to northern Virginia, on all sides of the hypothetical Baltimore Gneiss microcontinent, a probably window, and serve as markers for individual thrust sheets. The melanges seem to be large subaqueous slide deposits that were triggered by the advancing thrust sheets that now overlie them. Similar modern deposits occur on trench slopes where this is sufficient sediment for their construction. With continuing deformation, the debris was overrun by the thrust sheet forming a motif. The process continued until deformation ceased resulting in a stack of motifs. The rocks have a mixture of deformational fabrics resulting from both gravitational and tectonic processes, but the boundary between each melange and its overlying thrust sheet is tectonic, commonly a retrograded shear zones.

• Research Organization: Geological Survey, Reston, VA (USA)
• OSTI ID: 6644686
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
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580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
DEFORMATION
FEDERAL REGION II
FEDERAL REGION III
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC MODELS
GEOLOGIC STRATA
GEOLOGIC STRUCTURES
GEOLOGY
LITHOLOGY
METAMORPHIC ROCKS
NEW JERSEY
NORTH AMERICA
PETROLOGY
ROCKS
TECTONICS
USA
VIRGINIA