Integrated stratigraphy and paleoceanographic evolution of the pre-evaporitic phase of the Messinian salinity crisis in the Eastern Mediterranean as recorded in the Tokhni section (Cyprus island)

An integrated micropaleontologic, magnetostratigraphic and cyclostratigraphic investigation of the Tokhni composite section (Southern Cyprus Island, Eastern Mediterranean) refines the previously published age model and paleoenvironmental interpretation particularly concerning its uppermost pre-Messinian Salinity Crisis interval (pre-MSC), between 6.46 and 5.97 Ma. This section is characterized by a precession-paced alternation of red shales and limestones, which correlate with insolation maxima and minima on the basis of their delta O-18 signatures and calcareous nannofossil assemblages. The planktonic foraminifer and magnetostratigraphic events permit the tuning of the sedimentary cycles to the 65 degrees N summer insolation curve and to the Mediterranean pre-evaporitic reference sections. The upper bathyal sedimentary succession of the Tokhni composite section records paleoceanographic changes at 6.4 and 6.1 Ma, indicating increasingly stressed conditions both at the sea floor and in the water column. Compared to the Western Mediterranean pre-MSC successions, we observe less severe sea floor anoxic conditions at times of insolation maxima and higher salinity surface and bottom waters at times of insolation minima. Moreover, from 6.1 Ma to the MSC onset we observe a progressively increase of continental-derived waters, which was likely caused by a tec-tonic pulse. The MSC onset at 5.97 Ma is marked by the deposition of clastic carbonates rather than primary evaporitic facies and is approximated by the last recovery of foraminifera, the abundance peaks of Helico sphaera carteri and Umbilicosphaera rotula and the decrease of the Sr-87/86. The MSC onset is recorded two cycles below the Messinian erosional surface (MES, 5.60 Ma) and the overlying clastic evaporites, suggesting a hiatus of approximately 350 kyr.