Pg. 62; Illinois Bull., no. 95, p. 225, 1975. McDonough Loess Member of Roxana Silt. Present in central, southern, and western Illinois; notably in thick loess deposits adjacent to major valleys. Consists of gray to tan loess, commonly leached. Thickness up to 5 feet. Overlies Chapin Soil or older deposits; [underlies and/or occurs within] Pleasant Grove Soil. Fossiliferous. Age is Pleistocene (Wisconsinan Age; Atltonian Subage).
Type section: Pleasant Grove School section, in borrow pits and roadcuts 1.6 km southeast of McDonough Lake, in SW/4 NE/4 SE/4 sec. 20, T. 3 N., R. 8 W., Madison Co., south-central IL. Named from McDonough Lake on the Mississippi River floodplain, Madison Co., south-central IL.

Source: Publication; Hdbk Illinois stratigraphy (Illinois Geol. Survey Bull. 95, p. 225); US geologic names lexicon (USGS Bull. 1520, p. 197).

The McDonough Loess Member and associated Pleasant Grove Soil are probably not valid units according to authors and are not recognized in this study. The lower Markham Silt Member, upper Meadow Loess Member, and an informal sandy-silt facies are recognized in the Roxana Silt. The Markham is composed of leached, pedogenically altered material. Contains a moderate amount of sand and traces of gravel. Contains more silt, vermiculite, and unweathered minerals than the underlying Glasford Formation. The Meadow Loess Member composes the uppermost 80 to 90 percent of the Roxana and consists of calcareous and oxidized massive silt loam. The informal sandy-silt facies composes the entire Roxana in eastern IL and though lithologically similar to the Markham, it is not temporally correlative.

Source: GNU records (USGS DDS-6; Reston GNULEX).