Neotectonics and shoreline history of the Rock of Gibraltar, southern Iberia

Several sets of staircased Quaternary marine deposits can be observed along the Gibraltar coast ranging from 1 to 210 m above the present mean sea level. Geomorphological mapping establishes, from the relationship between shore, scree and dune sedimentary formations, five main morphotectonic steps on the Rock: marine terraces between 1 and 25 m, 30-60 m, 80-130 m, 180-210 m, and above. Each terrace level and its slope-aeolian linked sediments is backed by a steep relict sea cliff margin, so forming a composite cliff. The most recent coastal landforms and sediments are associated with the last 250 ka linked to Oxygen Isotope Stages (OIS) 1, 3, 5 and 7. These landforms determine a morphosedimentary highstand-lowstand sequence, with several staircased and offlapped episodes, comprising a major morphotectonic step. A well-developed palaeocliff usually separates the highstand marine terraces of OIS 9 from those of OIS 7. The Gibraltar mean tectonic uplift value of 0.05±0.01 mm/yr is maintained from 200 ka to the present. Before this, at least to 250 ka, the mean uplift rate was higher (0.33±0.05 mm/yr), possibly compatible with major tectonic events in response to a NNW-SSE compressive stress field between Africa and Iberia.