A brief review of ground‐water conditions in Michigan

The State of Michigan makes up about one‐half of the area of the great Michigan Synclinal Basin, the remainder of which embraces Lakes Michigan and Huron and small parts of Wisconsin, Illinois, Indiana, Ohio, and Ontario [see 1 (p. 7) of “References” at end of paper]. The Basin has characteristics of both a geosyncline and a major structural basin. The geosynclinal origin is indicated by the facts that the Basin has been progressively downwarped, the beds thicken markedly into the central area, the outline of the course of the outcropping rocks is roughly oval, and the minor structures within the Basin are mostly parallel to the longer diameter of the downwarp. Evidence of several periods of isolation and evaporation and the absence of thick series of coarse clastic sediments in the post‐Cambrian rock‐column are features that are more characteristic of structural basins.