Historical:Everett 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
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Lithostratigraphy: Ottawa Limestone Megagroup >>Platteville Group >>Plattin Subgroup >>Nachusa Formation >>Everett Member
Chronostratigraphy: Paleozoic Erathem >>Ordovician System >>Champlainian Series >>Blackriveran Stage
Allostratigraphy: Tippecanoe Sequence


H. B. Willman and T. C. Buschbach

Name Origin

The Everett Member of the Nachusa Formation (Templeton and Willman, 1963, p. 90) is named for Everett Street in Dixon, Lee County, near the type section.

Type Section

The type section of the Everett Member is located in the type section of the Nachusa (a quarry on the east edge of Dixon (SE SE SW 33, 22N-9E)) where it is 7.5 feet thick.

Other Names

The Everett is equivalent to the Watertown Member of the Chaumont Formation in New York.

Extent and Thickness

The Everett Member averages about 7 feet thick in the northern outcrop area, and is commonly about 20 feet thick in the southern area.


The Everett has the typical Nachusa lithology, differing from the Eldena Member in being more massive, very abundantly fucoidal, and generally purer. At the top of the member there is a distinctive bed of fine-grained, dense dolomite or limestone 3-8 inches thick that has a smooth, white-weathering surface and overlies a band of very large chert nodules. A thin bed of bentonite occurs 8-9 feet below the top in the southern outcrop area.


TEMPLETON, J. S., and H. B. WILLMAN, 1963, Champlainian Series (Middle Ordovician) in Illinois: Illinois State Geological Survey Bulletin 89, 260 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation