Subsurface Investigation of the Wisconsin Point Barrier Spit

Abstract

A barrier spit is a coastal feature formed by laterally moving water carrying and depositing sediment in the direction of the wave motion. To better understand the processes and conditions that cause the formation of barrier spits, a subsurface investigation was conducted on the Wisconsin Point barrier spit along the west coast of Lake Superior. A geophysical survey was carried out using ground penetrating radar (GPR) to image the interior of the Wisconsin Point barrier spit in Superior, Wisconsin. Four cross-barrier lines were collected using a pulseEKKO 100 GPR system with frequencies of 50, 100, and 200 MHz. Using different frequencies allows for the capturing of various depths of penetration and resolution of the sediments. The 100 MHz frequency was primarily utilized for imaging with a 0.25 meter step size due to the depth of penetration and good resolution it provides. Topography was collected using a Topcon RL-H3CL laser leveling system at two meter intervals. The topography data was then input into Microsoft Excel to be processed and then geometrically corrected by the pulseEKKO 100 software to reflect the topography of the barrier spit. The GPR data was processed using pulseEKKO software and displayed using wiggle trace format. By interpreting the imagery, the profiles illustrate sub-horizontal and dipping reflections indicative of a progradational, aggradational barrier. The information collected will be used to understand the processes that formed the barrier spit and to help plan a habitat for the endangered piping plover.