Franconian Stage

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Lithostratigraphy: Knox Dolomite Megagroup
Chronostratigraphy: Paleozoic Erathem >>Cambrian System >>Croixan Series >>Franconian Stage
Allostratigraphy: Sauk 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)

T. C. Buschbach


Original description

Franconian Stage (Howell et al., 1944, chart 1).


Other names


Type section

Type location

The type section of the Franconian Stage is based on the type section of the Franconia Formation at Franconia, Chisago County, Minnesota.

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Franconian Stage includes the strata from the Elvinia Zone (at the base) to the top of the Dikelocephalus postrectus Zone. Some stratigraphers prefer to place the top of the stage lower in the Franconia, at the top of the Ptychaspis-Prosaukia Zone of Bell et al. (1956)-- the Prosaukia Zone of Lochman-Balk and Wilson (1958). These faunal zones have not been differentiated in Illinois, but the Ironton and Franconia Formations are at least approximately equivalent to the type Franconia Formation and are included in the Franconian Stage.

Extent and thickness





Well log characteristics


Age and correlation

Environments of deposition

Economic importance



BELL, W. C., R. R. BERG, and C. A. NELSON, 1956, Croixan type area-upper Mississippi Valley, in El Sistema Cambrico, su paleogeografia y el problema de su base-symposium, Part 2: 20th International Geological Congress, p. 415-446.
HOWELL, B. F., et al., 1944, Correlation of the Cambrian formations of North America: Geological Society of America Bulletin, v. 55, p. 993-1003.
LOCHMAN-BALK, CHRISTINA, and J. L. WILSON, 1958, Cambrian biostratigraphy in North America: Journal of Paleotology, v. 32, p. 312-350.

ISGS Codes

Stratigraphic Code Geo Unit Designation