DUNES IN A TRANSITIONAL ZONE: USING MORPHOLOGY AND STRATIGRAPHY TO DETERMINE THE RELATIVE AGES OF GREEN POINT DUNE COMPLEX AND ELBERTA DUNES

Dune morphology, soil development, and stratigraphy can provide valuable insight into the stabilization and activation history of dune complexes. The Green Point Dune Complex (GPDC) and Elberta dunes, found near Frankfort Michigan, lie at a latitudinal transition point between perched dunes to the north and lake-plain dunes to the south. GPDC consists of seven separate parabolic lake-plain dunes while the Elberta dunes, approximately 6 km north, consist of 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 dunes within these two dune complexes by examining stratigraphic relationships and soil development (including horizonation, pH, clay content, and Fe activity ratios). We found that soil profiles (typically A/E/B/ horizonation) at the dune crests reveal slight variances which can be used to determine relative ages between dunes. Additionally, intersections between parabolic dune arms were useful in determining relative migration histories of adjacent dunes. Dunes at GPDC are found to have seven unique ages relative to each other, although the intervals between dune migration periods appear to be relatively short. Dune-axis orientation ranges from east-west to northeast-southwest, showing differences in environmental conditions (i.e., wind direction) during formation. The Elberta dunes, all oriented northeast-southwest, have four distinguishable migration periods and appear to be younger than GPDC. 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. This improved chronology will help us to understand the causes of dune stabilization and activation by comparing neighboring perched and coastal lake-plain dunes.