Late Tortonian–Middle Messinian Palaeoenvironmental Changes in the Western Betic Strait (SW Spain)

Abstract

During the late Neogene, the Mediterranean Sea was connected with the Atlantic Ocean by two straits: the northern Betic Strait and the southern Rifian Strait. In this paper, we analyze the main palaeoenviromental changes produced in the western sector of the Betic Strait during the late Tortonian–middle Messinian (7.4–6 Ma). The temporal evolution and statistical analysis of benthic foraminiferal assemblages both in cores and surface sections of the western Guadalquivir Basin (SW Spain) allow drawing an initial important deepening from the late Tortonian calcarenite coastal areas to the well oxygenated, upper slope palaeoenvironments of the latest Tortonian to early Messinian, with a latest Tortonian condensed horizon composed by glauconitic silts deposited in the middle-outer shelf. The lower Messinian silts and clays (7.2–6.3 Ma) were deposited in a upper slope scenario, with a small oxygen depletion at 6.48 Ma. The 6.3–6.2 Ma interval was characterized by an important sea level drop and the presence of low oxygenated, outer shelf palaeoenvironments in this area, coinciding with a global glaciation. Prior to the Messinian Salinity Crisis (5.97–5.33 Ma), the upper slope palaeoenvironments were initially re-established (∼6.2–6.1 Ma) and finally a new regressive period (∼6 Ma) preceded Messinian Salinity Crisis.