Thebes Anticline (Discarded)
Location
T15S, R3W, Alexander County
References
J. Weller and Ekblaw 1940, Pryor and Ross 1962
Description
The Thebes Anticline was defined on the basis of surface mapping of the bedrock uplands near Thebes. J. Weller and Ekblaw (1940) illustrated a structure section along the Mississippi River bluff and showed a series of anticlines and synclines cut by vertical faults . The largest upfold has Kimmswick Limestone (Upper Ordovician) exposed at the core and Silurian and Lower Devonian strata along the flanks. Pryor and Ross (1962) stated that the Thebes Anticline extends east-southeast several miles inland from the bluffs. The anticline is poorly delineated on their geologic map, which shows several faults striking north-northeast near Thebes.
The Commerce Anticlinorium (McCracken 1971) in Missouri is more or less in line with the Thebes Anticline; however, the axis of the Commerce structure strikes northwest.
New mapping in the Thebes Quadrangle (Harrison and Schultz 1992, and unpublished data) reveals a complex pattern of faulting at Thebes Gap. The most prominent faults strike northeast and exhibit right-lateral offsets, displacing units as young as the Mounds Gravel (Pliocene to early Pleistocene?). No structure resembling the Thebes Anticline is apparent on Harrison and Schultz's maps; therefore, the name Thebes Anticline should not be used.
Author's note: Because plate 1 was printed before final revisions to the text, the Thebes Anticline appears on plate 1 as it was described by J. Weller and Ekblaw (1940) and Pryor and Ross (1963).
Figure(s)
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