Palaeocene–Eocene deep water agglutinated foraminifera from the Numidian Flysch (Rif, Northern Morocco): their significance for the palaeoceanography of the Gibraltar gateway

Abstract. A lower bathyal to abyssal agglutinated foraminiferal fauna (over 78 taxa belonging to 31 genera) is documented from Palaeocene–Eocene deep-water sediments of the Numidian Flysch (Talaa Lakrah Unit) in Northern Morocco. The sample locality is adjacent to the Strait of Gibraltar, which comprised an oceanic ‘gateway’ between the Tethys Ocean and the North Atlantic during the Palaeogene. The chronostratigraphy of the section is based upon long-distance comparisons with the stratigraphic ranges of identified species in the North Atlantic region and the Polish Carpathians. Although no major evolutionary turnover among deep-water agglutinated foraminifera (DWAF) is observed across the Palaeocene/Eocene boundary, a change from Palaeocene Aschemocella- and Trochamminoides-dominated assemblages to an early Eocene Glomospira assemblage is recognized. This Glomospira biofacies occurs throughout the North Atlantic and western Tethys and may indicate lowered productivity and widespread oxygenated deep-water conditions during the early Eocene greenhouse conditions. A change to an overlying Reticulophragmium amplectens biofacies in green claystones reflects renewed higher productivity. Taxonomic affinities and the succession of benthic foraminiferal assemblages from the Gibraltar gateway display greater affinities to Tethyan assemblages than North Atlantic assemblages. This is interpreted as faunal evidence for a late Palaeocene to early Eocene equivalent of ‘Mediterranean outflow water’, flowing from the western Tethys into the Atlantic.