Publication Date


Document Type


First Advisor

Odom, J. Edgar

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Geology




The Coon Valley Member of the Jordan Formation is a sequence of dolomitic sandstones and sandy dolostones that stratigraphically occur between the Van Oser Member of Jordan Formation and the overlying Oneota Dolostone. Detailed study of selected outcrops near LaCrosse, Wisconsin indicates that the rocks composing the Coon Valley were deposited in shallow marine environments ranging from lower shoreface to intertidal. These environments were transitional between a dominantly clastic littoral environment (Van Oser) and a shallow, tidal dominated carbonate platform environment (Oneota). The lower portion of the Coon Valley Member consists of dolomitic sandstones that were deposited in lower shoreface to offshore environments, seaward of the littoral environments represented by the Van Oser Member. The basis for this interpretation is a decrease in grain size and sorting; an influx of carbonate; a change in bedding style, especially cross-bedding; and the mode of burrowing in the Coon Valley sandstones. The depositional environments of the upper portion of the Coon Valley vary from offshore to the intertidal environment of a carbonate platform. These environments are indicated by a further decrease in clastic sedimentation and by the occurrence of oolites, intraclasts, grapestones and algal stromatolites.


Includes bibliographical references.


130 pages




Northern Illinois University

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