Lacey Member

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Lithostratigraphy: Potsdam Sandstone Megagroup >>Mt. Simon Sandstone >>Lacey 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 Lacey Member of the Mt. Simon Sandstone (Templeton, 1950, p. 155).


It is named for Lacey School, De Kalb County.

Other names


Type section

Type location

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).

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Lacey Member overlies the Mayfield Member of the Mt. Simon Sandstone.

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).




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.
TEMPLETON, J. S., 1950, Mt. Simon Sandstone in northern Illinois: Illinois Academy of Science Transactions, v. 43, p. 151-159.

ISGS Codes

Stratigraphic Code Geo Unit Designation