SALINA GROUP LITHOFACIES IN THE MICHIGAN BASIN: A REVIEW FROM A TO G

A series of newly archived cores at the Michigan Geological Repository for Research and Education have allowed the first detailed observations of the entirety of the Salina Group in southeastern Michigan. Prior to these acquisitions, due to the inclination of industry, the known curated cores available focused on the Salina A- and F-units. However, new cores have recently become available, which promise to drastically enhance our understanding of the Salina Group subsurface stratigraphy in Wayne County, southeastern Michigan. A series of stratigraphic test wells (the Delray #1, the Wynadotte cores) and engineering site evaluation wells (Gordie Howe International Bridge Project and the Rouge River CSO Tunnel Project) core from surface (Middle Devonian Dundee or Detroit River Group) to the lower Salina Group (A- or B-Unit).

The Salina Group were deposited during the Upper Silurian and represent a series of deposits in a restricted marine basin, punctuated by periods when the basin was connected to the open ocean. In the subsurface of the Michigan Basin, the Salina Group has been subdivided, on the basis of wireline log and cuttings data, into the A-0 through G units. Major evaporite units in the Salina Group include the A-1 and A-2 evaporites, the B-Unit, the D-Unit and the F-Unit. All of these units reached halite saturation and are characterized by interbedded dolomudstones, anhydrites and rock salts. In the central basin, the A-1 unit reaches sylvite saturation, and sylvinite deposits are found and have been economically exploited in the past. Thick shales with interbedded anhydrite and dolomite are found in the C-, E-, and G-Units. In the southernmost Upper Peninsula, the Salina Group undergoes lateral facies changes to the dominantly shale Pte. aux Chenes Formation.

An overview of the Salina Group lithofacies will be presented with review of their distribution in the subsurface of Michigan.