Calcareous dinoflagellate turnover in relation to the Messinian salinity crisis in the eastern Mediterranean Pissouri Basin, Cyprus

摘要

The extent to which the Messinian salinity crisis modified the initially Tethyan, eastern Mediterranean phytoplankton community has been investigated by monitoring the fate of calcareous dinorlagellale cysl assemblages prior to, during and after the salinity crisis in the Pissouri section (Cyprus). A rich, but low diversity open oceanic assemblage, dominated by Caleiodini'llum albalioskmwn, is found in the upper Torlonian and lower Messinian. The upper Messinian (pre-evaporitic) sediments yield only few cysts bin the assemblage is much more diverse and reflects unstable more neritic conditions (liicarinelhun Iricarinclloidex), lluvial influence (Leonella gramfmi) and varying, temporally increased salinities {Purnambiigiti luhero.w), probably related to the increasingly restricted environment. The basal Pliocene sediments relied the return to normal marine conditions; the dinoflagellate assemblage is rich in cysts and again has a low diversity. However, in contrast to the C. ulbatrosiaimm-ilamin&led upper Tortonian and pre-evaporilic Messinian sediments, L. granijera clearly dominates the basal Pliocene association just after the replenishment of the Mediterranean basin. Apart from this shift in dominance, the onset of the Pliocene is furthermore marked by the first appearance of CatciodineUum elongatwu, which must have immigrated from the Atlantic Ocean. Lehexsphaera unmiiu a postulated remnant of the Tethyan Ocean survived the salinity crisis, possibly in as yet unidentified marine refuges in the Mediterranean itself. Although the environmental changes caused by the Messinian salinity crisis did not lead to an extinction of calcareous dinoflagellate species of the Pissouri Basin, it resulted in a significant change in the assemblages and contributed to a more modern character of the Pliocene dinoflagellate association in the eastern Mediterranean.