Lithostratigraphy: Potsdam Sandstone Megagroup >>Mt. Simon Sandstone >>Lacey Member
Chronostratigraphy: Paleozoic Erathem >>Cambrian System >>Croixan Series >>Dresbachian Stage
Allostratigraphy: Sauk Sequence
T. C. Buschbach
The Lacey Member of the Mt. Simon Sandstone (Templeton, 1950, p. 155) overlies the Mayfield Member. It is named for Lacey School, De Kalb County.
The type section of the Lacey Member of the Mt. Simon Sandstone is located 2.5 miles west of Lacey School, De Kalb County. The member is 1880-2070 feet deep in McQueen No. 1 boring (SW NE NE 27, 42N-3E) (sample set 1466).
Extent and Thickness
The Lacey Member is 176-230 feet thick.
The Lacey Member is principally conglomeratic sandstone, although beds of fine-grained sandstone occur in the middle part and locally in the lower part. Beds of red shale are more common in the Lacey and higher members than in the lower members. Only the Lacey and higher members of the Mt. Simon are differentiated in northeastern Illinois (Buschbach, 1964).
BUSCHBACH, T. C., 1964, Cambrian and Ordovician strata of northeastern Illinois: Illinois State Geological Survey Report of Investigations 218, 90 p.
TEMPLETON, J. S., 1950, Mt. Simon Sandstone in northern Illinois: Illinois Academy of Science Transactions, v. 43, p. 151-159.
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