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Depositional Modeling Carbonate Strand Plain Development Using High-Resolution GPR and C-14 Dating


Understanding modern carbonate depositional systems gives valuable insights into the interpretation of ancient carbonate systems. Ancient carbonate strand plains act as productive hydrocarbon reservoirs because of their relatively high porosity. Unfortunately, ancient strand plains are difficult to identify in the rock record because of a lack of work done on modern analogs. Advances in ground penetrating radar (GPR), allowing high resolution subsurface mapping, has enhanced the understanding of modern systems, including strand plains. San Salvador Island in the Bahamas hosts a well-exposed and easily accessible Holocene strand plain, ideal as a modern analog. Sandy Hook, located at the southeast part of the island, consists of approximately 35 beach/dune ridge-swale combinations. The ridges show signs of erosion and subsequent deposition suggesting four distinct phases of deposition. In this study, 20 sediment samples were collected from a depth of one meter. The samples were collected to ensure that each of the depositional phases were represented. Sediment from each sample was C14-dated to create a depositional timeline. Four pseudo-3D GPR surveys were acquired using a 400 MHz antenna. The pseudo-3D surveys were strategically taken to explore internal changes in a particular depositional phase as well as changes laterally between the depositional phases at different sites across the study area. Long 2D transects were acquired connecting the pseudo-3D surveys, to give context for the entire study area. A depositional model for modern strand plain systems was produced that interprets the ridge-swale combinations as deposited by storms.