Foraminiferal response to the deposition of insolation cycle 90 sapropel in different Mediterranean areas

Abstract. Foraminifera were investigated across the sapropel unit corresponding to insolation cycle 90 deposited in three different oceanographic and depositional settings of the Mediterranean Sea (Alboran Sea, South Adriatic Sea and Ionian Sea). The constant presence of benthic foraminifera throughout the sapropels at <2000 m water depth and their absence within the sapropel at greater depth (>3000 m) indicate that the severity of oxygen depletion at the time of sapropel onset increases with increasing water depth.

Planktonic and benthic foraminiferal patterns also document an interruption during sapropel deposition, which allows for the recognition of two sapropel phases. In all basins, the short interruption appears to be related to climatic deterioration, which led to the break in stratification and, hence, to the re-oxygenation of bottom waters. Since the interruption of the time-equivalent sapropel intervals has been documented previously in other Mediterranean areas, these data support the recent theory that this interruption must have been a trans-Mediterranean phenomenon and that the interruption records a short excursion out of the periods of wet climate associated with precessional minima.