Wall Member

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Lithostratigraphy: Ottawa Limestone Megagroup >>Galena Group >>Kimmswick Subgroup >>Dunleith Formation >>Wall Member
Chronostratigraphy: Paleozoic Erathem >>Ordovician System >>Champlainian Series >>Trentonian Stage
Allostratigraphy: Tippecanoe Sequence

Primary source

Willman, H. B., Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, and Jack A. Simon, 1975, Handbook of Illinois Stratigraphy: Illinois State Geological Survey Bulletin 95, 261 p.

Contributing author(s)

H. B. Willman and T. C. Buschbach


Original description

The Wall Member of the Dunleith Formation (Templeton and Willman, 1963, p. 123).


Named for Wall Street in East Dubuque, Jo Daviess County, near the type section.

Other names


Type section

Type location

The type section of the Wall Member is part of the Dunleith Formation type section (in an exposure in the Mississippi River bluffs on the north side of East Dubuque (SE 19, 29N-2W))(fig. O-2B), where the Wall is 9.7 feet thick.

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Wall Member of the Dunleith Formation overlies the Sherwood Member.

Extent and thickness

The Wall Member is commonly 10-12 feet thick.


The Wall Member is less argillaceous than the Sherwood below and more argillaceous than the Wyota above. The argillaceous zone at the top is not prominent, but the upper 1-3 feet commonly has more argillaceous mottling and thin, wavy shale partings than the beds below. A widespread bentonite bed as much as 4 inches thick occurs near the middle of the member. Chert nodules are common, and the beds above the bentonite are more cherty than those below.




Well log characteristics


Age and correlation

Environments of deposition

Economic importance



TEMPLETON, J. S., and H. B. WILLMAN, 1963, Champlainian Series (Middle Ordovician) in Illinois: Illinois State Geological Survey Bulletin 89, 260 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation