GPR results used to infer depositional processes of coastal spits in large lakes

The depositional processes which determine the locations and sedimentation pattern of lacustrine coastal spits is still controversial (Gilbert 1885, 1890; Thompson 1937; Coakley 1976; Nielsen et al. 1988). Most frustrating is the difficulty of recognizing spit deposits in ancient rock successions. The criteria for recognition of spit deposits from drill core and geophysical logs is still an uncertain because the sedimentologic linkage with modern deposits is not well understood. Recent improvements in ground penetrating radar (GPR) offers a means to better understand modern sedimentary structures in coastal spits, which in turn will improve the interpretation of spit deposits in buried rock sequences. Previous research on the use of GPR to infer sedimentary facies and depositional processes to our knowledge is limited only to the pioneering work of Ulriksen (1982). Later work by Forgotson et al. (1990) and Beres and Haeni (1991) provided several guidelines for classifying and interpreting radar signatures. The actual linkage of spit depositional processes with radar facies (reflection patterns) will be the focus of this paper. Our objective is to show how radar facies from two coastal spits can be used to infer depositional processes.