USING SOIL DEVELOPMENT AND STRATIGRAPHY TO DETERMINE THE RELATIVE AGES OF GREEN POINT DUNE COMPLEX AND ELBERTA DUNE COMPLEX

Soil Development and stratigraphy can provide valuable insight into the stabilization and activation history of dune complexes along the northeaster shoreline of Lake Michigan. The Green Point Dune Complex (GPDC) and Elberta Dune Complex (EDC), found near Frankfort Michigan, lie at a latitudinal transition point between perched dunes to the north and coastal lake-plain dunes to the south. Examining dunes at this transition point allows for comparison between the two dune types. GPDC consists of seven separate parabolic lake-plain dunes while the EDC, approximately 6 km north, comprises five parabolic dunes perched on a glacial bluff. Both sites are characterized by stabilized dunes with overlapping arms which indicate non-concurrent periods of migration. Here, we attempt to determine the relative ages of these two dune complexes through stratigraphic relationships, field mapping, and soil development (including horizonation, pH, clay content, and Fe activity ratios). Soil profiles (typically A/E/B/ horizonation) at the dune crests reveal slight variances that can be used, along with dune arm stratigraphic relationships, to determine relative ages between dunes. Dunes at GPDC have seven unique ages relative to each other, with slight disagreements between field and lab ages. Calibrated ages, as compared with Lichter’s (1998) regional dune chronosequence, show that all of the dunes in the complex formed within the last 2500 years. Dune-axis orientation ranges from west to southwest, showing differences in environmental conditions (i.e., wind direction) during formation at GPDC. Dune at EDC are all oriented in a southwestern direction, have four distinguishable migration periods, and are interpreted to be younger than GPDC based on soil horizonation. Our future work in the area will focus on optically stimulated luminescence (OSL) dating of the dunes with the goal of further constraining the timing of dune migration and further comparisons with Lichter’s chronosequence. This improved chronology will help us to understand the causes of dune stabilization and activation by comparing nearly adjacent perched and coastal lake-plain dunes.