The Messinian of Agios Myron (Crete, Greece): A key to better understanding of diatomite formation on Gavdos (south of Crete)

The Agios Myron section in the NE of the Heraklion Basin on central Crete exposes a pre-evaporitic Messinian sequence of 24 sedimentary cycles of deep-marine homogeneous and laminated marls (sapropels). Planktonic foraminiferal biostratigraphy and ash layers show that the 24 cycles in section Agios Myron correlate to cycles M79 to M102 in the well-studied and orbitally tuned Metochia section on Gavdos Island. The correlation of the cycle patterns in sections Agios Myron and Metochia not only provides tuned ages for sedimentary cycles, planktonic foraminiferal bioevents, and ash layers in Agios Myron, but also reveals that the diatomites in Metochia cycles M94-M102 have no equivalents at Agios Myron. The onset of diatomite formation on Gavdos at 6.72 Ma is shown to coincide with eutrophication and related to a restriction-imposed increase in salinity 20 kyr earlier at 6.74 Ma. Geographic differences in productivity and possibly also the better preservation potential of siliceous microfossils on the much deeper seafloor at the Metochia site are believed to explain why diatomites are present on Gavdos and absent in time-equivalent levels at Agios Myron.