Modesto Anticline (Discarded)

Location

Northern Macoupin County

References

Easton 1942, Ball 1952

Description

A subtle east-trending anticlinal nose was mapped on the basis of sparse subsurface data from the Herrin Coal Member. Abundant, newly available well records indicate that an anticline is indeed present in the Herrin Coal in the northeast part of T12N, R7W (Nelson 1987b). The long axis of the fold trends northeastward and closure is about 30 feet (9 m). The anticline that I mapped differs substantially in trend and extent from the Modesto Anticline of Easton (1941) and Ball (1952). No anticline is evident on any mapped horizons below the Herrin Coal Member. The high on the coal, like most such features in west-central Illinois, is probably a product of differential compaction of the Pennsylvanian rocks that contain numerous sandstone lenses. I do not regard such minor nontectonic structures worthy of naming.