Historical:Duncan Mills Member

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Pleistocene stratigraphy of Illinois
Series Bulletin 94
Author H. B. Willman and John C. Frye
Date 1970
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Lithostratigraphy: Glasford Formation >>Duncan Mills Member
Chronostratigraphy: Cenozoic Erathem >>Quaternary System >>Pleistocene Series


H. B. Willman and John C. Frye

Name origin

The Duncan Mills Member of the Glasford Formation is named for Duncan Mills, Fulton County.

Other names

The Duncan Mills Member has previously been called Jacksonville-Buffalo Hart deposits (Wanless, 1957).

Type section

The type section is from exposures in the Enion Section (table 6) 4 miles south of Duncan Mills, NW SW SE Sec. 32, T. 4 N., R. 3 E. It is also described in the Cottonwood School, Lewistown, and Tindall School Sections (table 6).

Table 6 -- Stratigraphic Sections (partial)
The following 21 stratigraphic sections describe exposures in Illinois and illustrate many of the aspects of Pleistocene stratigraphy. These sections contain the type localities for 21 rock-stratigraphic units, 4 soil-stratigraphic units, and 3 time-stratigraphic units and include paratypes for several other units. The sample numbers preceded by "P" are the numbers used in the Illinois State Geological Survey collections. Analytical data on many of these samples are on file at the Survey. The sections are arrange alphabetically by name.

Stratigraphic relationships

It is bounded by the Hulick Till Member above and the Kellerville Till Member below, and is recognized as a member only when it is contained between these two bounding till units.

Extent and thickness

The Duncan Mills Member is as much as 30 feet thick.


In the type section the Duncan Mills Member consists of glacially derived sand, and sand and gravel with some silt, generally deeply weathered. Clay mineral composition is given in table 5.

Age and correlation

The Duncan Mills Member locally contains deposits in both the Monican and Liman Substages of the Illinoian Stage. It contains outwash of the retreating Kellerville glacier and deposits of the advancing Hulick glacier.


WANLESS, H. R., 1957, Geology and mineral resources of the Beardstown, Glasford, Havana, and Vermont Quadrangles: Illinois Geological Survey Bulletin 82, 233p.

ISGS Codes

Stratigraphic Code Geo Unit Designation