Evidence for detachment of the Cambro-Ordovician carbonate sequence in the central Appalachians
- Maryland Geological Survey, Baltimore, MD (United States)
- Univ. of Pittsburgh, PA (United States). Dept. of Geology and Planetary Science
Throughout the central Appalachians Cambro-Ordovician carbonate strata are commonly believed to conformably overlie Lower Cambrian clastic strata of the Chilhowee Group. A recently recognized interval of calc-mylonite, 3 to 15 m thick, within the lower Tomstown Formation near the base of the Cambrian carbonate sequence suggests that a structural break may exist. The calc-mylonite is a regional feature which may be recognized for at least 80 km along strike at a consistent stratigraphic level although it and adjacent strata are intricately folded and faulted. The interval includes very light gray to white marble with laminae of tan dolomite which exhibit pervasive mylonite foliation and an east-west stretching lineation. Asymmetric microstructures and detached isoclinal fold hinges suggest that this marble records a component of simple shear. Locally developed kinematic indicators record a top to the west sense of shear. A common mineral assemblage is dolomite + quartz + calcite + muscovite + epidote [+-] chlorite [+-] talc, suggesting that deformation occurred under greenschist facies conditions. Overlying the calc-mylonite is dark gray laminated mylonitic limestone 10--30 m thick, in which strain decreases stratigraphically upward. The calc-mylonite is interpreted as recording detachment of a rigid carbonate sequence from underlying clastic strata. The carbonates have moved westward an unknown distance from their original place of deposition. This detachment is an early structure that was subsequently folded and faulted with the Blue Ridge cover sequence.
- OSTI ID:
- 5935334
- 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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