Buckhorn Member
Lithostratigraphy: Ottawa Limestone Megagroup >>Galena Group >>Kimmswick Subgroup >>Dunleith Formation >>Buckhorn Member
Chronostratigraphy: Paleozoic Erathem >>Ordovician System >>Champlainian Series >>Trentonian Stage
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 T. C. Buschbach
Name
Original description
The Buckhorn Member of the Dunleith Formation (Templeton and Willman, 1963, p. 119).
Derivation
Named for Buckhorn Corners, Stephenson County, 2 miles east of the type section.
Other names
The Buckhorn is called the "Blue" in the lead-zinc district.
History/background
Type section
Type location
The type section of the Buckhorn Member of the Dunleith Formation is located in a quarry at Buena Vista (NW SW NE 15, 28N-7E), where the member is 8.3 feet thick.
Type author(s)
Type status
Reference section
Reference location
Reference author(s)
Reference status
Stratigraphic relationships
The Buckhorn Member is the basal member of the Dunleith Formation.
Extent and thickness
The Buckhorn Member is commonly 5-8 feet thick but is generally absent in southwestern Illinois, where it is overlapped by the St. James Member.
Lithology
The Buckhorn consists of argillaceous, medium to coarse, blue-gray dolomite heavily speckled with black, particularly at the top. It contains green shale partings and in the northwestern area is slightly sandy. It locally contains several very thin layers of bentonite.
Core(s)
Photograph(s)
Contacts
Well log characteristics
Fossils
Paucicrura [Dalmanella] rogata is especially common in the Buckhorn Member.
Age and correlation
With the overlying St. James Member, it is equivalent to the Ion Member at the top of the Decorah in the region northwest of Illinois.
Environments of deposition
Economic importance
Remarks
References
TEMPLETON, J. S., and H. B. WILLMAN, 1963, Champlainian Series (Middle Ordovician) in Illinois: Illinois State Geological Survey Bulletin 89, 260 p.
ISGS Codes
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