THE IMPORTANCE OF SPIT DEPOSITS WITHIN THE VALLEY-FILLS OF THE NORTHWESTERN GULF OF MEXICO

Recent work has documented the importance of “fetch-limited” barrier islands and spits along the coastlines of the world. Despite the importance of these features on the modern coast and their suggested high-preservation potential, very few examples of “fetch-limited” barrier islands have been documented in the ancient. Using high-resolution marine seismic profiles and several cores from the estuaries of the northwestern Gulf of Mexico, we document the presence of these features preserved within Holocene valley-fill successions. We also examine their similarity within seismic profiles to other depositional elements including bayhead deltas and tidal inlets – both also preserved as a series of prograding clinoforms within seismic profiles. Our results suggest that fetch-limited barrier-islands are best preserved in under-filled incised valleys. Due to their similarity in seismic character to bayhead deltas, they may be more common than formerly thought but often mistaken for other coastal features in the sedimentary record.