AAPG Bulletin, V. 84, No. 7 (July 2000), P. 975-996.

High-Resolution Sequence Stratigraphic Analysis of the St. Peter Sandstone and Glenwood Formation (Middle Ordovician), Michigan Basin, U.S.A.¹

G. C. Nadon,² J. A. (Toni) Simo,³ R. H. Dott, Jr.,³ and C. W. Byers³

©Copyright 2000. The American Association of Petroleum Geologists. All rights reserved. 
¹Manuscript received August 20, 1998; revised manuscript received August 18, 1999; final acceptance November 15, 1999.
²Department of Geological Sciences, Ohio University, Athens, Ohio 45701.
³Department of Geology and Geophysics, University of Wisconsin, 1215 W. Dayton St., Madison, Wisconsin 53706.
This paper stems from research of basin compartments and seals funded by the Gas Research Institute under contract 5089-260-1810. The project could not have been completed without the foresight of W. B. Harrison, Western Michigan University, in collecting the numerous St. Peter cores and his generosity in allowing access to this core repository. Our thanks to Shell Resources, Unocal, and Marathon Oil companies for access to core, the colleagues and students at the University of Wisconsin, and the other universities that participated in this project for numerous discussions and critiques. The reviews of P. Catacosinos, P. Daniels, and J. May helped sharpen the focus of the paper. 

ABSTRACT

The Middle Ordovician St. Peter Sandstone and Glenwood Formation (Ancell Group) represent a significant target for gas exploration at the base of the Tippecanoe sequence in the Michigan basin. Core and well log data show that the St. Peter-Glenwood interval contains numerous carbonate units that provide the basis for both regional correlation and subdivision of the section into at least 20 high-frequency sequences. The temporal resolution afforded by these sequences allows a detailed analysis of sediment partitioning as the basin evolved. The spatial distribution of the basal sequences illustrates the pronounced east-to-west onlap of the Wisconsin arch. An abrupt increase in sequence thickness upsection indicates that a major episode of basin-centered subsidence began during middle St. Peter deposition and continued through the deposition of the Glenwood Formation. The upper sequences show a significant beveling of the Glenwood Formation and the top of the St. Peter Sandstone in the north, south, and southeast areas of the basin prior to deposition of the overlying Black River carbonates. Although eustatic sea level changes were undoubtedly operating at several scales, the facies distribution of this mixed clastic/carbonate system also documents significant changes of local and regional tectonics.