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This paper presents the easternmost mineralogical and geochemical evidence of the 1755 Lisbon tsunami found in the Western Mediterranean. This multidisciplinary analysis of a sediment core obtained in Gibraltar (southern Iberian Peninsula) has allowed us to differentiate a tsunamiite from an old lagoon (The Inundation). This tsunamigenic layer has increased levels of calcite and aragonite and higher concentrations of Ba and ferromagnesian elements in comparison with the underlying lagoonal sediments of this core. This layer is also differentiated by its paleontological record, with the introduction of marine species within this lagoon. The uppermost part of the core includes a transition from swampy/marsh paleoenvironments to terrestrial scenarios, with a final anthropogenic filling occurring during the last century. [ABSTRACT FROM AUTHOR]

• The Holocene paleoenvironmental evolution of a coastal lagoon is recorded. • An open bay was progressively confined until forming a restricted lagoon. • The 1755 tsunami deposits are identified near the top of the succession. • This deposit constitutes the first faunal evidence of this event for the Mediterranean Sea. This paper analyzes the first systematic faunal record of the 1755 Lisbon tsunami in the Mediterranean. On the basis of sedimentological and paleontological features, the sedimentary record of a core collected in Gibraltar was divided into six sedimentary facies, with a paleoenvironmental evolution from a shallow marine paleoenviroment to an increasingly restricted lagoon. This record includes a bioclastic layer deposited by the 1755 Lisbon tsunami and characterized by an erosive base, presence of basal rip-up clasts and abundant shell debris composed by marine and brackish molluscs. The paleoenvironmental reconstruction derived from the foraminiferal analysis is congruent with that inferred from the sedimentary and the macrofaunal reconstructions, with the introduction of brackish species into the innermost, intertidal areas of a confined lagoon. This paleontological record is the first faunal evidence of the 1755 Lisbon tsunami in the Mediterranean. [ABSTRACT FROM AUTHOR]