Abstract

New stratigraphic data suggest that the diachronous evolution of the Ordovician foredeeps in the southern and central Appalachians was remarkably similar. Stratigraphic features that characterize the Middle Ordovician Sevier basin in Tennessee and the Middle and Late Ordovician Martinsbuirg basin in Pennsylvania are in identical ascending order: (1) disconformity on the Knox Group–Beekmantown Group, (2) shelf carbonates, (3) slope deposits, (4) submarine fan turbidites, and (5) contourites and muddy turbidites.

We propose that diachronous attempted subduction of the North American craton beneath southeastern microplates and/or volcanic arcs resulted in uplift and erosion of the western shelf followed by its rapid subsidence. Basinward migration of eastern and northeastern terrigenous source areas and associated submarine fan turbidites resulted from continued convergence and filled the basins. Finally, tectonic stabilization and lowering of the source area is recorded by contourites and muddy turbidites.

The evolutionary model proposed for the Sevier and Martinsburg basins closely resembles present-day tectonics of the Timor foredeep and the adjoining Sahul shelf north of Australia. Similar comparisons have also been made for Ordovician basins in the northern Appalachians. Analogous tectonic mechanisms, therefore, appear to have operated diachronously along the eastern margin of North America from Tennessee to New England and possibly to Newfoundland during Ordovician time.

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