Geophysical investigations of wave ravinement at the base of the shoreface: Hurricanes Ike and Sandy

摘要

The transgressive wave ravinement is an important stratigraphic sequence boundary, forming the base of transgressive and the top of lowstand systems tracts. It is presumed to form by wave ravinement of the shoreface, planing off the barrier sands, estuarine and older sediments as sea level rises and the shoreface migrates landward. An erosive lag, often diagnostic of the ravinement surface, is left behind and marine and shoreface sands, often recycled from the eroded material, aredeposited on top. The transgressive ravinement is frequently well-imaged in CHIRP data on the inner- to outer shelf, either because of the physical contrast between Holocene sands above and Pleistocene or estuarine material below (often residing in buried river channels), or because of the presence of lag material. But the process of wave ravinement, occurring somewhere along the base of the shoreface, is not well understood, and is difficult to observe because it presumably happens during the most severe storm conditions. The relationship between shoreface sand shoreward of the ravinement, and marine sand seaward, is also poorly known, with little understanding of whether, how, and in what direction sand crosses this boundary.