CHARACTERIZING THE SEDIMENTARY FLUXES AND GEOMORPHOLOGICAL ALTERATIONS OF PRESQUE ISLE PENINSULA USING GROUND PENETRATING RADAR

Presque Isle Peninsula, situated within the Pennsylvania boundary of Lake Erie, is heavily susceptible to the erosional processes created by the constant movement of wind and water. This oscillatory pattern of lacustrine transgression and regression cycles creates a dynamic pattern of sedimentary fluxes and surface features which are visible throughout the landscape. We expect to see similar patterns that document these episodes in the subsurface, but due to the fragile ecosystem and other constraints typical subsurface, investigations are impossible.

Ground penetrating radar (GPR) is a minimally invasive geophysical technique that uses high frequency (10 MHz to 2 GHz) electromagnetic (EM) waves emitted from a transmitting antenna that penetrate the subsurface and return to the receiver as a succession of reflections produced at certain interfaces. These interfaces represent contrasts in physical properties in the rock or sediment and typically correspond with stratigraphic or structural boundaries. The velocity of propagation of the EM waves is dependent on the relative dielectric permittivity (εr), a geophysical property related to the ability of a material to store and release electromagnetic energy in the form of an electric charge. GPR data can be collected quickly across long distances without major disturbances, making this an ideal form of subsurface investigation at Presque Isle.

In this research, GPR data was collected at a series of shore-perpendicular transects across Presque Isle to characterize the subsurface stratigraphy through the identification of sediment interfaces and depositional packages. The sites were chosen to investigate depositional facies variability due to transgressive and regressive episodes and to provide a cross-section of below-ground sedimentary facies. GPR data shows numerous crosscutting and filling depositional sequences, bed thickness variability, dune structure, and overall sediment thickness. This study shows the ability of the GPR method to better understand the link between subsurface structure and surficial processes in a rapidly changing sedimentary environment efficiently and without disturbing the subsurface.