Foraminiferal record of environmental changes: Messinian of the Los Yesos area (Sorbas Basin, SE Spain)

Abstract

The Late Messinian of the Sorbas Basin (Betic Cordillera, SE Spain) has been sampled to estimate (1) the paleoenvironmental changes recorded by the benthic foraminifers in pre-evaporitic and evaporitic units, and (2) the impact of the ‘Messinian Salinity Crisis’ on the foraminiferal biodiversity. In the pre-evaporitic unit, foraminifers indicate a circalittoral to bathyal environments and show significant changes in bottom-water oxygenation. Simultaneously, the occurrences of epiphytic damaged foraminifers and the blocks of Porites point out the presence of plant substrates and coral-reefs on the infralittoral zone. The overlying evaporitic unit is characterized by four subaqeous selenitic gypsum layers and three marine fossiliferous intercalations. Each episode of gypsum deposition ends with a desiccation event. Each fossiliferous intercalations traduce a rapid reflooding of the basin by marine waters corresponding to infralittoral to upper bathyal environments with normal marine conditions. During the evaporitic period, the ecological conditions in the water column were intermittently favorable to the development of marine organisms, and moreover, the marginal basins of the Betic Cordillera were not continuously desiccated during the Messinian. The low percentage of extinct species (5%) at the Messinian–Pliocene boundary and the occurrences of benthic foraminifers in the evaporitic unit indicate that the infralittoral to upper bathyal environments have not been completely modified and/or barren during the ‘Messinian Salinity Crisis’, i.e. the ‘Messinian Salinity Crisis’ is not associated with a biological crisis.