Original paper

The sedimentary inventory of tsunamis along the southern Gulf of Cadiz (southwestern Spain)

Reicherter, Klaus; Vonberg, David; Koster, Benjamin; Fernández-Steeger, Tomás; Grützner, Christoph; Mathes-Schmidt, Margret

Abstract

Outcrop evidence and shallow percussion drilling in coastal areas proved sedimentary evidence for paleo-tsunamis along a 50 km long segment of the Atlantic coast of southern Spain. The coast between Barbate and Tarifa yielded several depositional environments to preserve tsunamigenic layers, both on top of rocky cliffs as well as in lagoons, marshlands and along sedimentary beaches. Also, we focused on bays with river inlets, which are most probably sheltered from direct tsunami wave action. In these bays, the Roman villages of Baelo Claudia and Mellaria are situated. We found no evidence for tsunamigenic sediments there.On the other side, the findings of an enigmatic, most probable tsunamite has been encountered upon the cliff along the Barbarte-Zahara de los Atunes beach in various heights above mean sea level. Because only one dark-colored fining-up layer with a paleocurrent direction towards the sea has been found directly resting on folded Betic substratum, we interpret this layer as tsunamigenic back wash sediments. The last major event that affected severely the coast of the Gulf of Cádiz was the 1755 Lisbon tsunami. Reportedly, wave heights reached > 10 m in the study area. So, it is likely that coastal changes and deposition of tsunamigenic sediments in this area occurred, being attributed to this 1755 event. However, also older sedimentary relicts of tsunamis have to be taken into account, because sedimentary cores yield evidence for multiple intercalations.

Keywords

1755 lisbon tsunamitsunamitesback wash sedimentsgulf of cadiz