Okaw Group
Lithostratigraphy: Pope Megagroup >>Okaw Group
Chronostratigraphy: Paleozoic Erathem >>Mississippian Subsystem >>Chesterian Series >>Gasperian Stage
Allostratigraphy: Kaskaskia 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)
Elwood Atherton, Charles Collinson, and Jerry A. Lineback
Name
Original description
Okaw Group (S . Weller, 1913, p. 120; S. Weller and J. M. Weller, 1939, p. 12; Swann, 1963, p. 76).
Derivation
Named for the Okaw River, now the Kaskaskia River.
Other names
History/background
Type section
Type location
The type section of the Okaw Group consists of exposures along the river in Randolph County (T4, 5, and 6S, R7 and 8W).
Type author(s)
Type status
Reference section
Reference location
Reference author(s)
Reference status
Stratigraphic relationships
The name is used only in western Illinois for formations from the Beech Creek through the Glen Dean (fig. M-25) in an area where the clastic units of the Hardinsburg are poorly developed and it is difficult to assign many small limestone outcrops to the proper formation.
Extent and thickness
Lithology
Core(s)
Photograph(s)
Contacts
Well log characteristics
Fossils
Age and correlation
Environments of deposition
Economic importance
Remarks
References
SWANN, D. H., 1963, Classification of Genevievian and Chesterian (Late Mississippian) rocks of Illinois: Illinois State Geological Survey Report of Investigations 216, 91 p.
WELLER, STUART, 1913, Stratigraphy of the Chester Group in southwestern Illinois: Illinois Academy of Science Transactions, v. 6, p. 118-129.
WELLER, STUART, and J. M. WELLER, 1939, Preliminary geological maps of the pre-Pennsylvanian formations in part of southwestern Illinois: Illinois State Geological Survey Report of Investigations 59, 15 p.
ISGS Codes
Stratigraphic Code | Geo Unit Designation |
---|---|