McDonough Loess Member

Lithostratigraphy: Roxana Silt >>McDonough Loess 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

Name

Original description

McDonough Loess Member (Willman and Frye 1970).

Derivation

The McDonough Loess Member of the Roxana Silt is named for McDonough Lake on the Mississippi River floodplain in Madison County.

Type section

Type location

Its type section is the Pleasant Grove School Section (table 6) 1 mile southeast of McDonough Lake, SW NE SE Sec. 20, T. 3 N., R. 8 W.

Table 6 -- Stratigraphic Sections (partial)
The following stratigraphic sections describe exposures in Illinois and illustrate many aspects of Pleistocene stratigraphy, including type localities and analytical sample data.

• 
  Pleasant Grove School Section

Stratigraphic relationships

The McDonough Member, designated Roxana zone-Ib in previous Illinois literature, overlies the Chapin Soil and is terminated at the top by the Pleasant Grove Soil and the overlying Meadow Loess Member of the Roxana Silt.

The spatial relations are shown diagrammatically by figure 8.

• 
  Fig. 8 -- Diagrammatic cross section showing the relations of formations and members of Wisconsinan age in northern and western Illinois.

Lithology

The McDonough Loess is gray to tan, generally leached, but at a few places (e.g., Pleasant Grove School Section) it contains some etched fossil snail shells. The member is also described in the Chapin, Cottonwood School, and Gale Sections (table 6). Previously published sections that describe the McDonough Member (Roxana zone-Ib) include the De Pue, French Village, Fulton Quarry, Hillview, and Literberry Sections (table 7). Mineral compositions are listed in table 5.

Table 6 -- Stratigraphic Sections (partial)

• 
  Chapin Section and Cottonwood School Section
• 
  Cottonwood School Section (cont.) and Enion Section
• 
  Flat Rock Section (cont.), Gale Section, and Jubilee College Section

Selected analyses from stratigraphic sections (X-ray analyses by Illinois State Geological Survey).

• 
  Table 5 -- Continued.

References

The McDonough Member is in the midpart of the Altonian Substage of the Wisconsinan Stage.

ISGS Codes

ISGS Code and Symbol

Stratigraphic Code	Geo Unit Designation
0670	--