Historical:Canadian Series

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Handbook of Illinois Stratigraphy
Series Bulletin 95
Author H. B. Willman, Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, Jack A. Simon
Date 1975
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Chronostratigraphy: Paleozoic Erathem >>Ordovician System >>Canadian Series
Allostratigraphy: Sauk Sequence


H. B. Willman and T. C. Buschbach

Name Origin

The Canadian Series (Dana, 1874, p. 214), is named for exposures in eastern Canada.

Extent and Thickness

The Canadian Series is represented in Illinois by the Prairie du Chien Group, which chiefly consists of as much as 2500 feet of cherty dolomite that contains some beds of sandstone.

Stratigraphic Position

The Canadian Series unconformably overlies Cambrian dolomite (Eminence) throughout most of Illinois, but in northwestern Illinois it overlies Cambrian sandstone (Jordan). The series, in turn, is overlain unconformably by Champlainian sandstone (St. Peter), except in the southernmost part of the state where it is overlain by sandy dolomite (Everton) (fig. O-4). The lower Ordovician strata in Illinois have been included in the Canadian Series since 1963 (Templeton and Willman). They were called the Lower Magnesian (Owen, 1840) until the early 1900s, at which time they were named the Prairie du Chien or Lower Ordovician Series (fig. O-6).


Canadian strata contain few megafossils, and preservation of the fossils is generally poor. Gastropods, cephalopods, and algal mounds are the most common evidences of the life from the Canadian seas.


DANA, J. D., 1874, Reasons for some of the changes in the subdivisions of geological time in the new edition of Dana's Manual of Geology: American Journal of Science, v. 8, p. 213-216.
OWEN, D. D., 1840, Report of a geological exploration of part of Iowa, Wisconsin, and Illinois in 1839: U.S. 28th Congress, 1st session, Senate Executive Document 239, 161 p.
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