Small-scaled variations in the 1755 CE tsunami deposits – Observations from a sedimentological trench

Abstract

Tsunami deposits originating from the 1755 CE Lisbon tsunami are known from the Spanish Gulf of Cádiz. The coastal areas around Conil de la Frontera were severely affected by the tsunami, with the destruction of the Conilete village, damages to the medieval Torre de Castilnovo, and inundation of low-lying areas of Conil de la Frontera (e.g., the old tuna factory La Chança). A tsunami wave train of at least three waves with inundation heights of up to 8 m has been reported in historical eyewitness documentation. Already, few studies have documented sedimentary remnants in the form of sandy units, and their inland extends in Conil de la Frontera and the adjacent alluvial plains of El Palmar de Vejer. Few studies along the coastal areas of the tsunami-affected Iberian Peninsula excavated trenches and pits for sampling. Yet, no study has investigated the 1755 CE tsunami deposits and their small-scaled sedimentological features in a high resolution along the cross-section of a sedimentological trench. This research presents a combined sedimentological, micropaleontological, and biogeochemical analysis of a coastline-perpendicular cross-section in a large-scale hand-dug trench (4.5 × 4.5 × 1 m) from the coastal alluvial plain of El Palmar de Vejer. By means of sediment-stratigraphic analysis, grain size and micropaleontological analyses, organic biogeochemistry, and photogrammetry the 1755 CE tsunami layer has been distinctly identified from its surrounding strata, and sedimentary structures resulting from small-scaled tsunami processes have been analyzed.