Quaternary Geology of the Detroit, Michigan Quadrangle and Surrounding Areas

A preliminary 1:24,000 scale surficial geologic map of the Detroit 7.5 minute topographic quadrangle, and surrounding areas, was produced to serve as a framework for future urban site assessment. The results show that the map area is a relict late Pleistocene glacial landscape on which is superimposed a Holocene system of streams, lakes and wetlands, and an Anthropocene landscape of manufactured land and artificial fill. Detroit city is built on subaqueous morainal deposits of the Detroit moraine, and the lakebed plains of glacial paleolakes Grassmere and Elkton. These landforms are largely obliterated by anthropogenic activity, hence urban geomorphic provinces were delineated based on the historic settlement and land use pattern of Detroit, which was controlled by: 1) the configuration of the Detroit River, and 2) the growth of the automobile industry following the geographic distribution of railroad lines. These cartographic delineations are hypothesized to have geologic significance in terms age and magnitude of human disturbance, thickness and type of fill, water table and groundwater flow characteristics, and type and amount of soil contamination. Surficial deposits are classified informally into “anthrostratigraphic units” (ASUs) using a lithostratigraphic approach modified to accommodate the presence of artifacts. An ASU is defined here as the surficial deposit lying directly beneath, and genetically related to, a constructional anthropogenic landform. ASUs are postulated to be the anthropogenic equivalent of a morphostratigraphic or allostratigraphic unit. Although the term “Anthropocene” has not been formally accepted by stratigraphers, it is useful for stratigraphic classification of ASUs in urban areas. ASUs were mapped as Manufactured Land, and nine types of Artificial Fill based on lithologic composition. During the 2012 field season, four students (Stanley Putnam, Ryan Schoch, Anthony Slusser, Steven Moorehouse) were involved in mapping, which focused on residential areas both east and west of Woodward Ave. During 2013, only Schoch was involved in mapping, which focused on industrial areas. OSL dates are still pending on four sand samples collected and submitted to the University of Illinois. Two radiocarbon dates obtained on wood and charcoal are consistent with archaeological artifacts and historic records suggesting anthropogenic fills dating from the mid-late 19 century are widespread in, and around, the Detroit riverfront. __________________________________________ Assoc. Prof. of Geology; [email protected]