Reelfoot Basin

Location

See text below

References

Schwalb 1969, 1971, 1982, Bond et al. 1971, Atherton 1971

Description

Schwalb (1969) introduced the term Reelfoot Basin for a Cambrian- Ordovician center of deposition that existed in the area of the present northern Mississippi Embayment. At that time, Schwalb was unaware of the existence of the Reelfoot Rift, but he recognized that the Cambrian-Ordovician succession is substantially thicker in the northern embayment area than in the surrounding region. Schwalb (1969) further envisioned the Reelfoot Basin as ancestral to the Eastern Interior (Illinois) Basin.

The definition of the Reelfoot Basin becomes unclear in Schwalb (1982), which refers to Pennsylvanian deposition in the Reelfoot Basin. The 1982 paper also fails to distinguish clearly between the Reelfoot Basin and the Illinois Basin and it does not suggest geographic limits for either.

I recommend that the name Reelfoot Basin be restricted to the paleogeographic depression that developed above the Reelfoot Rift and Rough Creek Graben after the cessation of active faulting in the rifts.

Faulting apparently ceased during or shortly after deposition of the Mt. Simon/Lamotte Sandstone in the St. Croixan (Late Cambrian) Epoch. The Reelfoot Basin subsided very rapidly in the St. Croixan and Canadian (Early Ordovician) Epochs, and it gradually lost expression during the Champlainian and Cincinnatian Epochs (Middle and Late Ordovician). The Reelfoot Basin covered part of western Kentucky, southern Illinois, southeastern Missouri, and northwestern Tennessee. It lay above the Reelfoot Rift and Rough Creek Graben, and it extended an indefinite distance onto flanking areas that had been subaerially exposed prior to Mt. Simon /Lamotte sedimentation. Although evidence is obscure, the Reelfoot Basin probably connected with the developing Ouachita geosyncline. No definite basin existed in the Reelfoot area after the Ordovician Period. The name Vincennes Basin has been applied to a trough that developed somewhat north of the older Reelfoot Basin during the Silurian Period.

Although names such as Reelfoot Basin may cause confusion, they are useful reminders that the Illinois Basin is largely a product of post-Pennsylvanian structural movement and that it did not exist as a depositional basin during most of the Paleozoic Era. Some researchers have chosen to use nongeographic terms such as proto-Illinois Basin to express the same idea.