Paleoenvironmental conditions preceding the Messinian salinity crisis in Lower Chelif Basin based on benthic foraminifera (Northwestern Algeria); A case study of Djebel Meni section

Abstract

The study of benthic foraminifera from the pre-evaporitic interval of Djebel Meni in the Lower Chelif Basin (Northwestern of Algeria) allowed the reconstruction of the paleoenvironmental conditions preceding the Messinian salinity crisis.Our results refer to three well-distinguished stages of environmental evolution. The first stage corresponds to the bottom part of the section which is characterised by a high diversity of benthic foraminifera. It may be interpreted by well-oxygenated and well-ventilated bottom water as a stable environment with a deepening marine environment. This refers to a fairly exchange of water with and into the Chelif Basin during this stage as an open marine environment as an outer shelf to slope environment. The second stage corresponds to the middle part of the section, which is characterized by a decline in abundance of the oxyphilic species and an increase in the suboxic–dysoxic ones. Within this interval, the gradual decrease in oxygen content is most likely triggered by deep-sea stagnation that indicates a slight and progressive lowering in sea level. The third stage of evolution is in the upper part of the section. It is characterised by a sharp decline in a number of taxa indicate the dominance of some species Bolivina spp., Bulumina spp. and Rectuvigerina spp. pointing to the departure from stability conditions to become a more restricted environment. These taxa are well known as oligotrophic with infaunal microhabitat. They thrive under a specific restricted environment with stressed conditions such as oxygen depletion, high salinity and high food supply favoured by an enhanced density stratification suggesting an inner-middle shelf environment.Our data point to that during the interval that precedes the Messinian salinity crisis, the Lower Chelif Basin most likely underwent the same paleoenvironmental conditions as the other Mediterranean basins.