Osman Monocline
Part of the La Salle Anticlinorium, Piatt (D, E-6, 7)
Location
Southwestern Champaign and Ford, and eastern Piatt and McLean Counties (D, E-7)
References
Clegg 1972
Description
The Osman Monocline is a west-facing monocline that has several domes along its upper limb. The southern end of the Osman Monocline is sharply offset about 6 miles (10 km) westward from the northern end of the Charleston Monocline in T18N, R7E, Champaign County. The relief is more than 1,000 feet (300 m) on pre-Pennsylvanian strata near the southern end of the flexure. It decreases northward toward Ford County, where the monocline gradually loses expression. Farther north a sinuous south-plunging anticline (unnamed), almost in line with the Osman Monocline, continues as far as southwestern Kankakee County. The Herscher Anticline is situated along this trend (plate 1).
The Osman Monocline shows clearly on Bristol and Buschbach's (1973) map of the top of the Galena (Trenton) Group (Ordovician) and on the Stevenson et al. (1981) map of the base of the New Albany Group (Devonian-Mississippian). The monocline also affects Pennsylvanian strata (Clegg 1972). Total relief on Pennsylvanian beds is undetermined because these rocks are eroded from the crest of the monocline.
