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Post Nipissing-phase strandplains of the Great Lakes reflect late-Holocene water levels that are linked to climate variability, glacial isostasy, and changes in basin hydrology. This study examines a strandplain sequence at Bailey's Harbor, Door County, Wisconsin, along Lake Michigan, which contains a record of water-level variations during the past 1000 years, following the separation of the Lake Michigan-Huron basin from the Lake Superior basin. Vibracores are used to define the current elevation of the foreshore facies in 25 preserved beach ridges. Optical ages for five individual beach ridges are compared with radiocarbon ages on basal peats from nine swales collected in a previous study. The optical chronology yields a ridge formation/preservation rate of 30 ± 2 yr/ridge similar to that of previous assessments. This study further demonstrates the efficacy of optical dating for deciphering late-Holocene beach-ridge sequences, providing multidecadal resolution. Lake level meets or exceeds, by at least 0.5 m, historic metrics at c. ad 1125-1225. The maximum water level after c. AD 1225 is comparable with that recorded by the instrumental data. There is a noticeable high lake level from c. AD 1560 to 1725. Dating of additional sites along Lake Michigan is required to establish local rates of glacio-isostatic adjustment, identify possible erosion of the outlets and to resolve lake-level records for individual lakes following the separation of the upper Great Lakes currently constrained to have occurred c. 2400 to 1200 years ago. [ABSTRACT FROM AUTHOR]

Aeolian sand in two small lakes within a Lake Michigan coastal-dune complex southwest of Holland, Michigan, provides a more detailed higher-resolution history of dune activity, during the later half of the Holocene, than do combined palaeosol and OSL ages from the dunes themselves. The sand signal from four cores within these lakes consists of visible sand laminae and invisible sand peaks within mud and sapropel units. Early in the history of dune growth the sand may have come from backdunes immediately adjacent to the lakes, but in the upper portions of the core aeolian sand is interpreted as having been transported from 30–40 m high parabolic dunes ∼200 m from the lakes. All but one episode of dune mobility suggested by radiocarbon-dated dune palaeosols or OSL-dated dune sand are represented by a peak in the radiocarbon-dated lacustrine sand signal. However, sand peaks occur in the lacustrine record that do not correspond to palaeosol or OSL ages, suggesting that the sand record from small lakes gives a more complete record of aeolian activity. Heterogeneity in sand deposition related to bathymetry suggests that the study of multiple cores from the same lake will yield the best results. No strong correlation between rising lake levels on the Lake Michigan relative lake level curve and aeolian activity was found, although such a correlation has been reported elsewhere. [ABSTRACT FROM AUTHOR]

Aeolian sand within lake sediment from Silver Lake, Michigan can be used as a proxy for the timing of high lake levels of Lake Michigan. We demonstrate that the sand record from Silver Lake plotted as percent weight is in-phase with the elevation curve of Lake Michigan since the mid-Holocene Nipissing Phase. Because fluctuations in Lake Michigan's lake level are recorded in beach ridges, and are a response to climate change, the aeolian sand record within Silver Lake is also a proxy for climate change. It appears that increases in dune activity and lake sand are controlled by similar climatic shifts that drive fluctuations in lake level of Lake Michigan. High lake levels destabilize coastal bluffs that drive dune sand instability, and along with greater wintertime storminess, increase niveo-aeolian transport of sand across lake ice. The sand is introduced into the lake each spring as the ice cover melts. [ABSTRACT FROM AUTHOR]