Historical:Romeo Member

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Handbook of Illinois Stratigraphy
Series Bulletin 95
Author H. B. Willman, Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, Jack A. Simon
Date 1975
Link Web page
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Lithostratigraphy: Hunton Limestone Megagroup >>Joliet Formation >>Romeo Member
Chronostratigraphy: Paleozoic Erathem >>Silurian System >>Niagaran Series
Allostratigraphy: Tippecanoe Sequence


H. B. Willman and Elwood Atherton

Name Origin

The Romeo Member of the Joliet Formation (Willman, 1973, p. 22), the top member, is named for Romeo, Will County, where part of the member is exposed at the top of quarries now largely filled with water.

Type Section

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.

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.


Corals are common and locally abundant in the Romeo Member.


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