Coggan Member
Lithostratigraphy: Hunton Limestone Megagroup >>Wapsipinicon Limestone >>Coggan Member
Chronostratigraphy: Paleozoic Erathem >>Devonian System >>Middle Devonian Series
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)
Charles Collinson and Elwood Atherton
Name
Original description
The Coggan Member of the Wapsipinicon Limestone (Norton, 1894, p. 23-24).
Derivation
Named for Coggan, Linn County, Iowa.
Other names
History/background
Type section
Type location
The type section of the Coggan Member is at the Illinois Central Railroad crossing of the Buffalo River near Coggan, Linn County, Iowa.
Type author(s)
Type status
Reference section
Reference location
Reference author(s)
Reference status
Stratigraphic relationships
The Coggan Member is at the base of the Wapsipinicon Limestone in Illinois.
Extent and thickness
The Coggan Member is not exposed in Illinois, but it occurs locally in subsurface and is as much as 20 feet thick in the area between Galesburg, Knox County, and Muscatine, Iowa.
Lithology
The Coggan Member consists of massive, buff, cherty dolomite. It also contains a thin bentonite that has been correlated with the Tioga Bentonite Bed, which occurs near the top of the Grand Tower Formation southeast of the Sangamon Arch.
Core(s)
Photograph(s)
Contacts
Well log characteristics
Fossils
Age and correlation
Environments of deposition
Economic importance
Remarks
References
NORTON, W. H., 1894, Notes on the lower strata of the Devonian Series in eastern Iowa: Iowa Academy of Science Proceedings 1, part 4, p. 22-24.
ISGS Codes
Stratigraphic Code | Geo Unit Designation |
---|---|