Devonian stratigraphy of the Appalachians
Lower and lower Middle Devonian (below the top of the Onondaga and equivalent) strata in the Appalachian unmetamorphosed fold-thrust belt are relatively thin and are laterally variable in lithology, thickness, and age. South of Virginia, thickness is less than 100 m; in Virginia and farther north, thickness ranges from 100 to 450 m. Locally, rocks of this age are unconformably absent in Pennsylvania and in Virginia and farther south. Clastic rocks dominate the interval in places along the southeastern margin of the fold-thrust belt and near pinch-outs at unconformities. Elsewhere, the interval is dominated by carbonate rocks. In contrast, thick sequences of lower Devonian rocks are preserved in Appalachian metamorphic belts in New England and in Alabama. The stratigraphic distribution of upper Middle (above the top of the Onondaga and equivalent) and Upper Devonian rocks is dominated by the widespread semicircular Catskill clastic wedge, centered on southeastern Pennsylvania. Near the depocenter, the succession grades upward from deep-water black shale, through shallow-marine sandstones and mudstones, to deltaic and fluvial red beds. These facies prograde both northwestward toward the craton and southwestward along structural strike. Pelitic rocks dominate the distal part of the wedge. Distribution of the Catskill clastic wedge reflects sediment transport onto the earlier Devonian shelf from an Acadian orogenic uplift. Local basins in Maine were probably not interconnected and reflect fault-block uplifts and pull-apart basins associated with wrench faults.
- Research Organization:
- Univ. of Alabama, University (USA)
- OSTI ID:
- 6652795
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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