Palaeoenvironmental changes after the Messinian Salinity Crisis in the Mediterranean Almería-Níjar Basin (SE Spain) recorded by benthic foraminifera

Abstract

In this study, the early Pliocene palaeoenvironmental context of the Mediterranean Almería-Níjar Basin (SE Spain) is analysed using benthic foraminifera, with special focus on environmental conditions after the Messinian Salinity Crisis (MSC). A deep upper-slope setting (274 m water depth), with high oxygen levels and low organic matter fluxes, is inferred for the earliest Pliocene sediments over the Miocene-Pliocene boundary. In this setting, the westernmost and earliest recolonization of the species Siphonina reticulata across the Mediterranean is reported. This finding, along with the presence of intensively bioturbated sediments and highly diverse benthic foraminiferal assemblages at —or just above— the Miocene-Pliocene boundary might indicate the earliest establishment of well-ventilated fully marine conditions in the Mediterranean after the MSC. Subsequent shallowing from 274 to 220 m water depth during the earliest Pliocene is likely related to a global sea-level drop. Palaeobathymetry remains stable around 220–230 m water depth after this sea-level fall. However, three successive palaeoenvironmental subintervals could be defined within this upper slope setting. Increasing continental organic matter and sediment inputs indicate higher fluvial discharge during the first subinterval. The second subinterval records a decrease in both terrestrial organic matter and sediment supply due to lower riverine discharge. Finally, reduced input of continental organic matter suggests low river runoff during the third subinterval, in which a slight increase in transported shelf foraminiferal taxa may be related to vertical tectonic movements of the basin margins.