SUBSURFACE IMAGING OF A HOLOCENE BARRIER, LONESOME POINT, MI

The research investigates the spatial and temporal subsurface stratigraphy of a Holocene barrier located at Lonesome Point, Michigan along the southeastern shore of Lake Superior. The objective was to collect, collate, process, and analyze multiple ground penetrating radar (GPR) lines perpendicular and parallel to the coast. Our goal was to image this geomorphic environment to understand the depositional processes that formed this unique Holocene Barrier on Lake Superior’s shoreline. Our location was chosen based on earlier reconnaissance datasets that were collected on roads that allowed for easy access with the GPR equipment. The data collected was non-invasive and non-destructive and resulted in visualizing subsurface stratigraphy well below the targeted barrier system. The GPR system used for this study was a pulseEKKO 100/PRO with a range of antennae frequencies – 25 MHz, 50 MHz, 100, MHz, 200 MHz, 225 MHz, 450 MHz and 900 MHz. We also used various transmitter powers and receivers that that allowed for increased stacking. An appropriate step size was used to avoid spatial aliasing as well as a suitable antennae separation for each frequency. Common midpoint surveys were collected in the field and were analyzed to determine a near surface velocity in order to estimate depth. Topographic measurements were collected along each line with a laser leveler to geometrically correct each GPR profile. Data was processed using pulseEKKO and EKKO_Project software and plotted using trace to trace and down trace filters in wiggle trace format. Stratigraphy from various geomorphic environments were imaged to depths > 50 m. With little research done on large barrier systems worldwide, these datasets are important as they will aid in better understanding and predicting future coastal changes due to both climate change and lake/sea level changes.