Abstract

The Rock of Gibraltar is located in a geographic configuration and a geodynamic context that favors the occurrence and preservation of tsunami deposits in their coasts. These deposits show different sedimentological and paleontological features depending on the sedimentary environment exposed to these high-energy events. The aim of this research is to describe the sedimentary record of the historical tsunamis in the Rock, i.e. those originated by the Lisbon earthquake (AD 1755) and the 218-209 BC earthquake, mainly characterized by their high heterogeneity. Three tsunamigenic facies have been differentiated in both the coast and the adjacent marine area of Gibraltar: i) massive, fine to medium sandy facies with reworked microfauna from the nearby Pliocene outcrops, characterized by the presence of vegetation remains to the top, normal grading and mud clast in the bottom, that record the inundation and the fast filling of a coastal lagoon due to erosion of the littoral spit; ii) crevice filling some meters above the sea-level in cliffs, constituted by highly bioclastic, coarse sandy coastal sediments, with predominance of echinoderm spicules and cirripids, very fragmented malacofauna (ostreids) and scarce benthic foraminifera (Elphidium crispum, E. advenum, Quinqueloculina sp.) and ostracoda (Bairdia mediterranea); and iii) submarine cave and rockshelter filling with bioclastic coastal and shallow marine bioeroded blocks, gravels and sands with bivalves (Acanthocardia tuberculata, Venus pollastra), gastropods (Hinia reticulata, Bittium reticulatum) and microfauna (foraminifera and ostracoda), probably deposited by a tsunami event backwash current in the shallow marine settings of the platform.