Sparta Shelf

Location

Southwestern lliinois, southeastern Missouri (fig. 2)

References

Meents and Swann 1965, North 1969, Nelson and Lumm 1985

Description

The name Sparta Shelf is applied to the southern part of the western shelf of the Illinois Basin. The Sparta Shelf lies west of the Fairfield Basin and northeast of the Ozark Dome. Its east margin is the Du Quoin Monocline. The southern border generally is described as following the Cottage Grove Fault System and Ste. Genevieve Fault Zone, whereas the western and northern limits are indefinite.

Little is known about the early Paleozoic history of the Sparta Shelf because of the lack of data. An ancestral Du Quoin Monocline may have existed during deposition of the Mt. Simon Sandstone (Upper Cambrian) and intermittently thereafter (Whitaker and Treworgy 1990). The shelf emerged during the Middle Devonian Epoch when faulting took place along its south margin. The sea reoccupied the area during the Late Devonian Epoch and the Mississippian Period; the Sparta Shelf then was not sharply differentiated from adjacent areas on the west flank of a broad embayment. Principal uplift on the Du Quoin Monocline began early in the Pennsylvanian Period and continued throughout the Pennsylvanian. Thus, the slowly subsiding Pennsylvanian Sparta Shelf was clearly separated from the more rapidly sinking Fairfield Basin to the east. Post-Pennsylvanian movement along the Du Quoin Monocline and Cottage Grove Fault System completed the evolution of the Sparta Shelf.