Study of the Recent Morphodynamic and Internal Architecture of the Sillon Talbert Gravel Barrier Spit Using GPR (France)

The Sillon de Talbert is a 3.2 kilometer trailing-type pebble spit located on the northern coast of the Brittany peninsula in France. It is composed of four distinct sedimentary units and is formed of sediments which granulometry ranges from sand grain to pebble. This study focuses on the internal architecture of the distal part of the spit. A near-surface geophysical method was used in order to image this architecture: Ground Penetrating Radar (GPR) using 500 MHz shielded and 100 MHz unshielded antennas. The 500 MHz shielded antennas were used to acquire 63 cross-shore and long-shore time sections, whereas the 100 MHz antennas were used to obtain Common Mid-Point (CMP) sections for velocity estimation. Following this acquisition, GPR data was processed using ReflexW® software, following different steps, including conversion of time sections into depth sections. The processed GPR sections were then interpreted. They allow to identify the internal structures and to define specific facies of the distal part. Moreover, we were able to link these sedimentary structures to marine dynamics and specific events like storms. Therefore, we understood how the different structures where put in place. Finally, the age of the structures was also determined.