Internal Architecture of the Tolleston Beach using Ground Penetrating Radar

Status Start Date End Date Locations
completed May 20, 2019 Dec 31, 2019 Porter, Lake, LaPorte
Director: Todd Thompson
Other Researchers: Erin Argyilan
Funding: Indiana University - Indiana Geological & Water Survey
Issue: The Tolleston Beach is the most lakeward of three large dune and beach complexes that arc across northwestern Indiana. The Tolleston Beach records long-term patterns of shoreline and dune behavior associated with variations in climate and concomitant lake-level and wind-pattern changes from about 6,000 years ago to the present. These behaviors are expressed in the variety of landforms that occur in the area, but also in the sediments and sediment distribution within the Tolleston Beach. Starting in the mid-1980s, geologists for the Indiana Geological and Water Survey at Indiana University Bloomington began examining the internal architecture of the Indiana Dunes area with a focus on the Tolleston Beach because of its implications for understanding modern shoreline, dune, and lake-level behavior. These studies used exposures and vibracores to recover sediments within the Tolleston Beach to determine the landforms internal architecture. The work was largely successful, but the scattered distribution and short length (3-5 m) of the vibracores coupled with the thick (10s m) eolian sediment cap on the Tolleston Beach resulted in an incomplete picture of the landform’s sediment distribution and development.
Objective: Additional subsurface tools are needed to understand the architecture of the Tolleston Beach. Ground penetrating radar (GPR) that images the subsurface to depths of 10s of meters, is portable, non-invasive, and less expensive. It can be used to build cross-sections of the landform.
Approach: This study collects transects of GPR across the eastern part of the Tolleston Beach, primarily from Dune Acres to Michigan City. The majority of this area is with the Indiana Dunes National Park and the Indiana Dunes State Park. The transects will be roughly south to north oriented using existing roads and trails, although it is possible to collect GPR in areas not developed. The GPR data needs to be corrected for topographic change. Lidar collected of northwestern Indiana during 2018 will be available in early 2019 that can be used to obtain extremely accurate elevation data along the transects.
Products: The result will be a series of cross-sections and 3D models, illustrating the distribution of sediment inside the Tolleston Beach and readily publishable in international earth science journals.
Benefits: 1. Knowledge of the long-term shoreline behavior related to a lake-level rise and fall 2. Detailed internal stratigraphy for environmental planning 3. Data for national and state park educational outreach.