REVISED BEDROCK MAP OF WAYNE COUNTY, MICHIGAN: AN OPPORTUNITY TO REASSESS THE NATURAL RESOURCES OF WAYNE COUNTY

The Michigan Geological Survey through the US Geological Survey Statemap Program has constructed a revised bedrock map of Wayne county, Michigan. Previous maps by Sherzer (1911) and Mozola (1969) were hampered by lack of well control in northern and western Wayne County.

Wayne county is densely urban through much of the eastern and southern portions of the county, with over 1.8 million people living in the area. Current revitalization programs and extensive renovation of many of the major highways has led to recognition among the city planners and administrators that natural resources are key components to infrastructure programs. Wayne county has historically produced sand (glass, injection molds, construction fill), clay (ceramics), rock salt (road de-icer), brine and sulfur (various chemical applications), and oil and gas. The Detroit Salt Mine produces 2-3 million tons of rock salt a year from underground mines below Detroit.

Infrastructure planning has promoted new geological investigations that have yielded a wealth of subsurface bedrock samples and data. Michigan Department of Transportation projects as well as a proposed combined sewer overflow system in northern Wayne county yielded more than 100 cores in the past decade. Several quarries in southeastern and southern Wayne County provided access to samples and estimates of the bedrock surface elevation beneath thin glaciolacustrine deposits. Combined with historical drilling, a revision of the Wayne county bedrock map has become feasible.

The revisions to the published map include refinements of the contacts between Devonian and Mississippian bedrock units in northern and central Wayne county. Access to both historical and modern cores has provided valuable materials for revising descriptions of the rock units in the area – some of which have not been described in decades. Mozola (1969) did not attempt to subdivide the Detroit River Group or Traverse Group into formations. The new cores show that these formations are mappable through the county.