Paper No. 20
Presentation Time: 9:00 AM-6:00 PM
GEOMORPHOLOGY, OSL AGES AND VOLUME ESTIMATES OF A NIPISSING BEACH RIDGE/DUNE COMPLEX NEAR KANGAROO LAKE, DOOR PENINSULA, WI
BRANECKY, Carolyn, Department of Earth Science, Rice University, 6100 Main Street, Houston, TX 77005, CHAVEZ, Natalia, Department of Geology, Sonoma State, 1801 E Cotati Ave, Rohnert Park, CA 94928, OIEN, Rachel, Department of Geology, University of Illinois Urbana-Champaign, 307 S. State Street, Apt 21, Champaign, IL 61820, RUIZ, Jacob, Department to Geological Sciences, El Paso Community College, P.O. Box 20500, El Paso, TX 79998, RAWLING III, J. Elmo, Geography/Geology, University of Wisconsin Platteville, 1 University Plaza, Platteville, WI 53818, HANSON, Paul R., Conservation and Survey Division, School of Natural Resources, Univ. of Nebraska, 102 Nebraska Hall, Lincoln, NE 68588-0517 and HART, David J., Wisconsin Geological and Natural History Survey, University of Wisconsin-Extension, 3817 Mineral Point Rd, Madison, WI 53705, cmb6@rice.edu
This study focuses on the geomorphology and geochronology of a beach ridge/dune complex near Kangaroo Lake, on the Door Peninsula of Wisconsin. These features are located on a strand-plain ~800m inland from the present day level of Lake Michigan (~177 m) at the Nipissing highstand shoreline (~184 m). Within the Nipissing strand-plain complex, smaller beach ridges and dunes are closer to Lake Michigan and have up to ~6 m of relief, while the largest ridge is furthest from Lake Michigan and is covered with parabolic dunes that have up to 25 m in relief. These are separated from a series of lower elevation dunes (likely Algoma or younger in age) by 0.3 kms of the strand-plain. Our investigation focused on eolian sand and included optically stimulated luminescence (OSL) dating, particle-size analysis (PSA), GIS analysis of a LiDAR-based DEM, and ground penetrating radar (GPR).
Our subsurface investigations showed the eolian sediments are composed of fine to medium sand that directly overlies coarse gravelly sand. The depth of the coarse sediment was used to create a surface for volume calculations, the average elevation of which is 182 m. This calculation revealed that approximately 122,000 m³ of sediment was transported to this region by littoral and eolian processes during the Nipissing phase. This portion of the strand-plain accumulated four times the amount of sediment compared to the nearby Algoma portion of the strand-plain, which contains ~32,000 m³ of sediment.
Preliminary OSL ages from eolian sand at Kangaroo Lake indicate that dunes were active between around 6.6 and 3.7 ka. Previous research conducted at Clark Lake, located ~11 km to the southwest of our study site, indicates that dunes were active multiple times in the late Holocene from ~7 to 1 ka. Unlike the results from Clark Lake, there is little evidence suggesting that dunes were reactivated in the late Holocene at Kangaroo Lake. Therefore, factors other than regional climate variability, such as sediment availability, may have influenced the differences in eolian activity at these two sites. This research was conducted by the Dune Undergraduate Geomorphology and Geochronology (DUGG) project, funded by the National Science Foundation Research Experience for Undergraduates program.
