Palaeoenvironmental changes of the early Pliocene (Zanclean) in the eastern Mediterranean Pissouri Basin (Cyprus) evidenced from calcareous dinoflagellate cyst assemblages

The first similar to 100 ka of the earliest Pliocene (Zanclean) sediments of the eastern Mediterranean Pissouri Basin on Cyprus have been investigated on calcareous dinoflagellate cyst assemblages. These assemblages reflect the return, in three phases, to the open oceanic conditions following the Messinian Salinity Crisis (MSC) 5.33 Ma ago. The lowermost phase (dominated by Leonella granifera cysts) indicates substantial land-derived nutrient supply and low salinities. This confirms earlier observations of enhanced continental water runoff during the earliest Pliocene in the eastern Mediterranean basin. The second phase (dominated by Caracomia stella and Calciodinellum albatrosianum cysts) indicates a change to warmer, meso- to oligotrophic waters. The third phase marks the first appearance and still continuing dominance of Thoracosphaera heimii in the region. In addition, the endemic eastern Mediterranean species, Lebessphaera urania, peaks within this upper interval. It probably survived the Salinity Crisis in the Mediterranean. The assemblage reflects the establishment of typical open marine, well stratified and oligotrophic surface conditions similar but not yet identical to the situation in the Mediterranean Sea today. This study points out a discrepancy between the fast refilling scenario (similar to 1-2 ka) in the Pissouri Basin and a long time (similar to 100 ka) environmental reorganisation in the surface waters as indicated by the calcareous dinoflagellate cysts. The onset of the Pliocene is also marked by the first appearance of Calciodinellum elongatum and Calciodinellum levantinum, which must have migrated from the Atlantic Ocean. (C) 2009 Elsevier B.V. All rights reserved.