ABSTRACT
The Appalachian basin is a typical foreland basin that has subsided episodically under the loads of successive thrust sheets. The dynamics of basin subsidence and upwarping of basin-margin arch systems reflects the flexural properties of the lithosphere. Quantitative models of the lithosphere depend on assumed rheological properties. This study attempts to test these geodynamic models in a part of the Appalachian basin.
Mississippian deposition is correlated with waning Acadian tectonism. Orogenic quiescence coincided with basin overdeepening and uplift of the Cincinnati arch or forebulge. Although the foreland basin was mudstone dominated, shoaling along the crest of the basin-margin arch system resulted in reworking and wedges of unconformities. In contrast, the onset of Alleghenian orogenesis during the Pennsylvanian is reflected in a thick wedge of terrigenous clastic sediments. The Pennsylvanian basin fluctuated between underfilled (restricted marine) and overfilled (nonmarine) conditions. Rapid response of the basin to thrust-sheet loading is inferred. These characteristics of Mississippian and Pennsylvanian deposition support a viscoelastic model of the lithosphere.
