Duncan Mills Member

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Lithostratigraphy: Glasford Formation >>Duncan Mills Member
Chronostratigraphy: Cenozoic Erathem >>Quaternary System >>Pleistocene Series

Primary source

Willman, H. B., and John C. Frye, 1970, Pleistocene Stratigraphy of Illinois: Illinois State Geological Survey Bulletin 94, 204 p.

Contributing author(s)

H. B. Willman and John C. Frye


Original description

Duncan Mills Member, Glasford Formation (Willman and Frye 1970).


The Duncan Mills Member 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

Type location

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.

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

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.




Well log characteristics


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.

Environments of deposition

Economic importance



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