Eldena Member

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Lithostratigraphy: Ottawa Limestone Megagroup >>Platteville Group >>Plattin Subgroup >>Nachusa Formation >>Eldena Member
Chronostratigraphy: Paleozoic Erathem >>Ordovician System >>Champlainian Series >>Blackriveran 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


Original description

The Eldena Member of the Nachusa formation (Templeton and Willman, 1963, p. 89).


Named for Eldena, Lee County, 6 miles southeast of the type section.

Other names


Type section

Type location

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

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

Extent and thickness

The Eldena Formation is commonly 5-10 feet thick in the northern outcrop area and in Calhoun County, but south of there it thickens to 14 feet in Ste. Genevieve County, Missouri, and to 40 feet at Cape Girardeau, Missouri.


The Eldena Member has the typical Nachusa lithology, except that the lower part has thin partings of blue-gray to gray-green or brown shale, and it is slightly more argillaceous than the Everett Member. In the southern area it contains finely conglomeratic and pseudo-oolitic beds, and a bentonite as much as 6 inches thick occurs at or near the top.




Well log characteristics


Age and correlation

The Eldena Member is equivalent to the Leray Member of the Chaumont Formation in New York.

Environments of deposition

Economic importance



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