Sedimentary processes and sequence stratigraphy of Lake Michigan, United States

Lake Michigan is the world’s sixth largest freshwater lake and has many features in common with oceanic settings, albeit at a smaller scale. All of the constructional features typical of ocean coasts can be found along the shore of Lake Michigan, and it has a shelf-slope system where coastwise rectification of currents, coastal downwelling jets, Coriolis veering of lake currents, benthic nepheloid layer, and density currents have been observed. Unlike ocean coasts, however, the wave climate is predominantly mild, and only a very small lunar tide exists, although other (quasi) periodic water-level fluctuations such as seiches and edge waves do occur. Another significant difference is the occurrence of quasicyclical climatically induced lake-level fluctuations of as much as 2 m (6.6 ft) that greatly influence the way that coastal sediments accumulate. Lastly, the Lake Michigan coast during the late Wisconsin and Holocene experienced multiple noncyclic transgressive and regressive events. Lake levels have been as much as 18 m (60 ft) higher and 60 m (200 ft), or more, lower than present, and changes have commonly occurred at rates several magnitudes greater than the most rapid eustatic sea level changes. In this chapter, we will show how hydrodynamic processes, cyclic and noncyclic lake-level changes, and the way in which sediments are supplied to the lake have interacted to shape the architecture of sedimentary deposits along the coast and in the deep basins. We will summarize the results of our own work, but we are also indebted to many researchers whose work is included in this narrative.