Paper No. 8
Presentation Time: 10:40 AM
THE RECORD OF EOLIAN ACTIVITY IN THE SEDIMENTS FROM A SMALL LAKE WITHIN A COASTAL DUNE COMPLEX, SOUTHEASTERN SHORE OF LAKE MICHIGAN
Radiocarbon ages on paleosols and OSL ages below modern surfaces have been the chief means of reconstructing chronologies of dune activity along Lake Michigan. Sediments in small lakes within dune complexes could potentially serve the same purpose. We have compared the record of eolian activity preserved in a lake downwind of a well-dated eolian complex. A 3-meter core was obtained with a vibracorer from Gilligan Lake (0.06 km2 in area) which is 0.8 km from Lake Michigan in the coastal dune complex southwest of Holland. Thirteen lenses of fine-grained windblown sand occur within the peat and clay of the core. Eight, AMS, 14C ages obtained from seeds, wood and leaves were used to date the lenses. Seven lenses deposited between 5650 and 4500 cal. YBP occur in the lower 80 cm. Paleosols and OSL ages in the surrounding dunes indicate that this was a period of vigorous eolian activity associated with the fall from Nipissing lake levels. Dune growth occurred in a broad zone including the area immediately around Gilligan Lake. By roughly 4000 cal. YBP, dunes around Gilligan Lake had stabilized and eolian activity was confined to the large parabolic dunes adjacent to Lake Michigan. Except for 4 closely spaced lenses deposited around 3000 cal YBP, this period of dune growth is not represented by sand lenses within the core, indicating that large amounts of windblown sand were not transported from massive parabolic dunes approximately 500 meters upwind. A period of relative dune stability began at roughly 2000 cal YBP and ended with a major remobilization within the last 500 years. This remobilization is marked by 2 sand lenses in the upper 25 cm of core. The chronology of eolian activity obtained from the Gilligan Lake core is consistent with the chronology obtained from the surrounding dunes, suggesting that sediments from small lakes may contain useful proxies for periods of dune growth and migration.