Birds Member
Lithostratigraphy: Hunton Limestone Megagroup >>Wilhelmi Formation >>Birds Member
Chronostratigraphy: Paleozoic Erathem >>Silurian System >>Alexandrian 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
Name
Original description
The Birds Member of the Wilhelmi Formation (Willman, 1973, p. 13).
Derivation
Named for the railroad siding at Birds, 2 miles northwest of the type section.
Other names
History/background
Type section
Type location
The type section of the Birds Member is part of the Wilhelmi Formation type section, located in a railroad cut about 5 miles southwest of Wilhelmi Airport (SE SW SE 35, 35N-9E).
Type author(s)
Type status
Reference section
Reference location
Reference author(s)
Reference status
Stratigraphic relationships
The Birds Member overlies the Schweizer Member of the Wilhelmi Formation.
Extent and thickness
Lithology
The uppermost part of the member and its contact with the overlying Elwood Formation are exposed in a ravine half a mile northeast (NW NW SE 36, 35N-9E). The Birds Member consists of 10-20 feet of slightly to moderately argillaceous, slightly cherty, thin-bedded, medium-gray dolomite. It is distinguished by several thin beds of relatively pure, finely laminated, fossiliferous dolomite.
Core(s)
Photograph(s)
Contacts
Well log characteristics
Fossils
Age and correlation
Environments of deposition
Economic importance
Remarks
References
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
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