The history of dune growth and migration along the southeastern shore of Lake Michigan: A perspective from Green Mountain Beach

 

Ed Hansen, Alan F. Arbogast and B. Yurk

 

          Mapping of paleosols exposed on dune faces has been combined with radiocarbon ages from these soils and optically stimulated luminescence (OSL) ages from sand below the modern surface in order to reconstruct the geomorphic history of the dune complex at Green Mountain Beach, 10 km southwest of Holland, Michigan. The first eolian deposition formed low, broad dunes about 5500 B.P. that roughly coincided with the Nipissing I high in Lake Michigan water levels. A period of eolian deposition over a broad area, extending at least a kilometer inland, ended about 4,000 B.P. with the stabilization of the modern surface of the backdunes. This dune building activity coincided with the rise to and then the fall from the Nipissing II high in lake-levels. After this time dune growth and migration were confined to a narrower zone closer to shore. The geometries of paleosols in the massive parabolic dunes indicate that this activity involved the inland migration of parabolic dunes during a period of net beach recession. Early dune growth and migration in the massive parabolic dunes is represented by the soils of The Lower Entisol (A/C horizonation) Series. These are overlain by a paleo-Inceptisol with a better developed A/E/Bs/BC/C horizonation that represents a period of extended stability in the dunes. This period of stability appears to have begun and ended at somewhat different times in different places within the Green Mountain Beach dune complex but lasted at least 1,500 years. The geometry of the paleo-Inceptisol indicates that by the beginning of this period the massive parabolic dunes had reached essentially their present height (up to 60 m above current lake levels). The paleo-Inceptisol was buried during a period of remobilization that began as early as 1,000 B.P. in some places but did not begin until 500-300 B.P. in most areas. The soils of the Upper Entisol Series represent brief periods of stability during this period of dune mobility that continues today.