Tectonic geomorphology of the south-central Appalachians: The influence of Triassic extension
- La Trobe Univ., Bundoora, Victoria (Australia). Geology Dept.
- Virginia Dept. of Mines, Minerals and Energy, Blacksburg, VA (United States). Division of Mineral Resources
During the final phase of the Alleghanian Orogeny, which ended probably in the mid-Permian, intense thrusting created a high mountain range with relief of up to 4.5 km and a width of 250--300 km. The drainage divide presumably lay within the Piedmont or Blue ridge Provinces, and probably ran subparallel to the present-day mid-Atlantic coastline. In the Middle and Late Triassic this mountain range was disrupted by the initial phases of rifting between the African and North American Plates. Many of the Alleghanian thrusts were reactivated as listric normal faults, creating a series of long, narrow asymmetric half grabens, and resulting in extensive delamination and thinning of the crust, particularly in the eastern Piedmont. South of the Salisbury Embayment the western limit of the Triassic basins steps consistently eastward, mirroring the offset of the ocean floor anomalies south of the Bermuda Fault Zone. The offset is also reflected by the easterly displacement of the present-day Appalachian drainage divide in southern virginia. This strongly suggests that the divide is largely inherited from the Triassic faulting episode. Rivers flowing westwards from the present-day Appalachians, including those like the New River crossing the Valley and Ridge Province, have retained more or less their pre-Triassic orientation, when they flowed down the western flanks of the Alleghanian mountains. The Triassic basins were separated by coast-parallel ranges with as much as 1 km of relief; these were largely eroded in the mid-Jurassic, so that by the Early Cretaceous the south-central Appalachians had more or less their present appearance. Subsequent erosion has probably resulted in westward retreat of the drainage divide.
- OSTI ID:
- 6786568
- Report Number(s):
- CONF-9404221-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 26:4; Conference: 43. annual meeting of the Southeastern Section of the Geological Society of America, Blacksburg, VA (United States), 7-8 Apr 1994; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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