The record of energetic marine events in the bay of Cadiz during historical times

The bay of Cadiz is a coastal area intensively occupied during prehistorical and historical times from which many archaeological remains have been preserved. The bay is a low coast characterized by several spit-barrier systems which close wide estuarine marshes. This kind of coastal environment is especially vulnerable to marine energetic events, like storms and tsunamis, which have occurred in the region during the late Holocene with some regularity. The present work summarizes the different morphosedimentary records of historical marine events identified in the Bay up to date. New chronological and stratigraphical data are presented, obtained from drills, together with different geoarchaeological indicators of historical marine events identified along the Bay. Special attention is paid on the effects produced on the Valdelagrana spit-barrier, where the geometry and age of different historical beach ridges reveal the onset of at least three very energetic events, probably of tsunamigenic origin: one on 2700-2300 cal BP, a second one by the end of the IX century AD and the third one in 1755 AD. The two first events caused deep geomorphological modifications, like river captures, onset of new beach ridge systems, and coastal lowering. Archaeological data indicate that economical effects and infrastructure damage produced by these events conditioned later human occupation and related activities.