Elucidating aeolian dune history from lacustrine sand records in the Lake Michigan Coastal Zone,USA

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.