Lake Michigan water levels and the development of Holocene beach-ridge complexes at Two Rivers, Wisconsin: Stratigraphic, geomorphic, and radiocarbon evidence
Two beach-ridge complexes formed at Two Rivers, Wisconsin, on the west shore of Lake Michigan during the past 5700 yr. Auger drilling, closely spaced vibracoring, and subsurface geophysical profiling using ground-penetrating radar along two east-west transects across ridges and swales indicate that several facies of beach sediment are capped with dune sand. 14C ages were obtained from basal-peat deposits collected from swales between successive beach ridges. Associated lake levels were interpreted from the elevation of coarse foreshore deposits observed on the east (basinward) side of the next lakeward beach ridge. 14C ages, geomorphic relationships, and stratigraphic interpretations indicate that progradation and water-level drop followed a major transgression. Lake level fluctuated on a scale of 1.7–2 m during the past 3000 yr.