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ABSTRACT: Cambrian/Early Ordovician Sequence Stratigraphy and Mt. Simon Sandstone Petrology--Michigan Basin

Jeffrey T. Cottingham

Rocks of Cambrian and Early Ordovician age are well known in Wisconsin and other areas surrounding the Michigan basin, but because of burial depth ranging from 3000 to 16,000 ft, relatively little is known about these rocks in Michigan. Core and cuttings examination demonstrate that similar stratigraphic sequences exist between the central Michigan basin and surrounding regions. Basinal lithofacies are similar to their outcrop counterparts in Wisconsin and are correlated on the basis of sediment types, sedimentary structures, and the concept of sequence stratigraphy.

The Mount Simon Sandstone in Michigan correlates with that observed in Indiana, Illinois, Wisconsin, and Iowa. Isopach data throughout the Midwest indicates a single depocenter in northeastern Illinois, with an arm extending into the central Michigan basin. Sedimentary structures and lithology indicate a subtidal marine environment that may be a transition to a shoreward nonmarine fluvial to eolian environment.

Observed diagenetic facies are influenced primarily by depth of burial. The deep facies (below 14,250 ft) exhibits extreme physical and chemical compaction of quartz grains. Quartz cement is predominant, with less than 1% porosity present. The shallow facies (above 8900 ft) exhibits pervasive dolomite and quartz cements and authigenic clays. Secondary porosity developed from dissolution of carbonate, quartz, and K-feldspar.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990