T. C. Buschbach
The type section of the Franconian Stage is based on the type section of the Franconia Formation at Franconia, Chisago County, Minnesota.
The Franconian Stage (Howell et al., 1944, chart 1) 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.
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.
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