Lombard Dolomite Member

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Lithostratigraphy: Knox Dolomite Megagroup >>Eau Claire Formation >>Lombard Dolomite Member
Chronostratigraphy: Paleozoic Erathem >>Cambrian System >>Croixan Series >>Dresbachian Stage
Allostratigraphy: Sauk 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)

T. C. Buschbach


Original description

The Lombard Dolomite Member of the Eau Claire Formation (Buschbach, 1964, p. 32).


Named for Lombard, Du Page County.

Other names


Type section

Type location

The type section of the Lombard Dolomite Member is located 2 miles east of Lombard, DuPage County, and is at a depth of 1535-1640 feet (sample set 15,336) in the same boring as the Elmhurst Member.

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Lombard Dolomite Member overlies the Elmhurst Member of the Eau Claire Formation.

Extent and thickness

The Lombard Member is recognized in northeastern Illinois, where it ranges from a few to 150 feet thick.


The Lombard consists chiefly of grayish brown, glauconitic, partly sandy dolomite containing beds of greenish gray shale. It contains beds of limestone in Kane and DuPage Counties. Northward and westward it grades to sandstone, and southward it becomes more shaly.




Well log characteristics


Age and correlation

Environments of deposition

Economic importance



BUSCHBACH, T. C., 1964, Cambrian and Ordovician strata of northeastern Illinois: Illinois State Geological Survey Report of Investigations 218, 90 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation