Pg. 8 (fig. 1), 26 (fig. 4), 27, 28-31, 44 (table 1), pl. 1, geol. sections. McCormick group. Lowest group in Pennsylvanian of Illinois. Includes Caseyville and Abbott (new) formations. As thus defined, includes strata formerly included in Caseyville group and lower part of Tradewater group. Underlies Kewanee group (new). Group is characterized by prominence of thick commonly massive relatively pure quartz sandstones that constitute 50 to 60 percent of strata; sandy shale and siltstone normally make up 40 percent or more of section. Coals are characteristically thin and limited ta continuity; limestones uncommon to rare, although fossiliferous sandy beds or sandy limestones are present locally. Age is Early and Middle Pennsylvanian. Presentation of new rock-stratigraphic classification of Pennsylvanian of Illinois. Cyclical classification retained but is independent of rock-stratigraphic classification.
Type locality: vicinity of McCormick, northwestern part of Pope Co., IL.

Source: US geologic names lexicon (USGS Bull. 1200, p. 2292).

Pg. 2 (fig. 1), 3-4, pl. 1. †McCormick Group of Kosanke and others (1960) abandoned. Rocks reallocated to Raccoon Creek Group. See Raccoon Creek. Classification proposed in this report agreed upon by State Geological Surveys of Illinois, Indiana, and Kentucky.

Source: Publication.