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.
