Gimlet cyclical formation. [A name applied to a middle portion of McLeansboro formation (Pennsylvanian) of central western Illinois, based upon the rhythmic-cycle theory of sedimentation. Origin of name not stated.]

Source: US geologic names lexicon (USGS Bull. 896, p. 821).

Pg. 50 (fig. 22), 60, 116-117, 193, 194, pls. 2, 5. Gimlet cyclothem in McLeansboro group. Thickness of cyclothem 15 to 85 feet. Includes (ascending) Gimlet sandstone, Gimlet coal, and Lonsdale limestone. Gimlet sandstone has maximum thickness of 50 to 60 feet but is locally absent in some localities where higher Gimlet beds rest on Farmington shale; sandstone fills channels that cut from 50 feet above coal No. 7 to about 5 feet above Brereton limestone. Cyclothem is separated by erosional unconformities from Sparland cyclothem below and Trivoli and Exline cyclothems above. Age is Pennsylvanian. Origin of name given.
Named from exposure on Gimlet Creek, in SE/4 sec. 16, T. 12 N., R. 9 E., Marshall Co., IL.

Source: US geologic names lexicon (USGS Bull. 1200, p. 1511).

Pg. 52 (table 2), 55 (table 3). Gimlet cyclothem in Modesto formation (new) of McLeansboro group. Presentation of new rock-stratigraphic classification of Pennsylvanian strata in Illinois; cyclical classification is independent of rock-stratigraphic classification.

Source: US geologic names lexicon (USGS Bull. 1200, p. 1511).