Palaeoenvironmental changes at the Tortonian/Messinian boundary: A deep-sea sedimentary record of the eastern Mediterranean Sea
Résumé
In the eastern Mediterranean, the island of Crete offers excellent exposures of upper Miocene marine deposits. Three detailed sections of the Tortonian/Messinian sedimentary succession were measured and sampled in three different basins (from west to east: Chania, Heraklion, and Sitia). The biostratigraphic analysis based on planktonic foraminifera yielded ages ranging from about 7.58 to 6.72 Ma. Nine bioevents were also recognised and provided good correlations between the studied sections. Rich benthic faunas (commonly occurring together with fish otoliths) have furthermore been recovered and analysed: foraminifera, mollusc (mostly bivalves), bryozoans, and ostracods. The autochthonous assemblages suggest deposition at middle-upper bathyal depths at the base and outer-inner shelf in the upper parts of the sections. The shallowing upward trend observed in all three sections is accompanied by the occurrence in a few Messinian levels of allochthonous fossils transported downslope and deposited in deep-water environments. Dysoxic episodes were moreover recorded in some beds, mostly in the Messinian. A comparison with other coeval basins and faunas indicates that similar palaeoenvironmental conditions predominated throughout the Mediterranean Sea during the late Miocene. This is consistent with the postulate of open connections (through marine corridors) between the Mediterranean and the Atlantic, presumably until late in the Messinian.