Historical:Lombard Dolomite Member
Lithostratigraphy: Knox Dolomite Megagroup >>Eau Claire Formation >>Lombard Dolomite Member
Chronostratigraphy: Paleozoic Erathem >>Cambrian System >>Croixan Series >>Dresbachian Stage
Allostratigraphy: Sauk Sequence
T. C. Buschbach
The Lombard Dolomite Member of the Eau Claire Formation (Buschbach, 1964, p. 32) overlies the Elmhurst Member and is named for Lombard, Du Page County.
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.
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.
BUSCHBACH, T. C., 1964, Cambrian and Ordovician strata of northeastern Illinois: Illinois State Geological Survey Report of Investigations 218, 90 p.
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