McClure Anticlinal Nose (Discarded)

Location

Northwestern Alexander County

References

J. Weller 1940

Description

J. Weller (1940) reported a southeast-plunging anticlinal nose in the Mississippi River bluffs east of the village of McClure. His geologic map indicates that Silurian rocks come to the surface at the crest of the structure in Section 12, T14S, R3W, and that uppermost Silurian-Lower Devonian Bailey Limestone crops out on the flanks. Remapping of the McClure Quadrangle (Devera et al. 1994) confirms the presence of a structural high in the area indicated by J. Weller. This high brings the Sexton Creek Limestone, St. Clair Limestone, and Moccasin Springs Formation (all Silurian) into view along the Mississippi River bluffs for a lateral distance of about 1.5 miles (2 km). These formations are overlain by the Bailey Limestone (Silurian-Devonian) and dip beneath Quaternary alluvium to the north and south. The high point of the structure is north of the mouth of Dongola Hollow near the center of Section 12. The base of the Bailey here is about 100 feet (30 m) above the floodplain. A small northwest-trending fault has been mapped near the apex. Dips on the flanks are 1° to 3°. No fold axis is apparent.

The northwest part of the McClure structure is concealed by alluvium and no subsurface data are available. This could be either the nose or the flank of the anticline or dome. Pending better definition, the feature should be unnamed.