Romeo Member

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Lithostratigraphy: Hunton Limestone Megagroup >>Joliet Formation >>Romeo Member
Chronostratigraphy: Paleozoic Erathem >>Silurian System >>Niagaran Series
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 Elwood Atherton


Original description

The Romeo Member of the Joliet Formation (Willman, 1973, p. 22).


Named for Romeo, Will County, where part of the member is exposed at the top of quarries now largely filled with water.

Other names


Type section

Type location

The type section of the Romeo Member is in the National Stone Company quarry, 6 miles south of Romeo, on the southwest side of Joliet, where it is part of the type section for the Joliet Formation, and is 20.2 feet thick.

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Romeo Member is the top member of the Joliet Formation.

Extent and thickness

The Romeo Formation ranges from 18 feet in Rock Creek Canyon along the Kankakee River to 34 feet thick in a quarry at Elmhurst in Du Page County.


The member consists of light gray to white, gray-weathering, pure, vesicular, thin- to medium-bedded dolomite, commonly with tight stylolitic bedding surfaces. It locally has pink mottling. It contains silicified fossils and several bands of chert nodules in the type locality, but in many exposures it exhibits little or no chert.




Well log characteristics


Corals are common and locally abundant in the Romeo Member.

Age and correlation

Environments of deposition

Economic importance



WILLMAN, H. B., 1973, Rock stratigraphy of the Silurian System in northeastern and northwestern Illinois: Illinois State Geological Survey Circular 479, 55 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation