Depositional processes and basin analysis of Messinian evaporites in Cyprus

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Abstract
Messinian evaporites in Cyprus resulted from the interplay of Mediterranean‐wide and eustatic sea‐level changes and local tectonics, in an inferred above‐subduction zone setting. Distinctive Tortonian‐early Messinian pre‐evaporitic facies include diatomaceous marls and microbial carbonates, overlain by a variety of gypsum facies and then by lagoonal‐lacustrine deposits and local palaeosols. Facies analysis and comparisons allow construction of a simple model, in which evaporites formed in semi‐isolated small basins not far below global eustatic sea‐level. Coarsely crystalline gypsum formedin situ along the margins of small basins and within shallow‐water lagoons (< 10 m deep); this comprised common banded‐stacked (i.e. layered) selenite, swallowtail selenite, botryoidal selenite and sugary‐bedded selenite. Fine‐grained gypsum precipitated widely and was reworked into basinal areas (< 70 m deep) by weak traction currents and low‐density turbidity currents. Shallow‐water derived selenite was also reworked basinwards by high‐density turbidity currents and debris flows. Slumps indicate tectonic instability. More detailed basin analysis can be achieved by study of individual sub‐basins. In the Polemi sub‐basin in the west, a Lower Unit (up to 60 m thick) comprises basinal gypsum, interbedded with gypsum turbidites and mass flow deposits, with slumps. This is overlain by an extensive mega‐rudite (up to 20 m thick) including up to metre‐sized clasts of marginal gypsum facies. Above, the Upper Unit (up to 70 m thick) includes shallow‐water gypsum (e.g. swallowtails), marl and minor microbial carbonates. The Pissouri sub‐basin in the south‐west exposes marginal facies of the Upper Unit, including deltaic elastics and palaeosols. The Maroni sub‐basin in the south exhibits a basinal lower gypsum unit, with laterally equivalent marginal facies (up to 50 m thick), overlain by an extensive mega‐rudite (up to 20 m thick). Finally, the Mesaoria subbasin in the north exposes relatively marginal gypsum facies in an unstable tectonic setting. Formation of the Polemi, Pissouri and Mesaoria gypsum sub‐basins relates to coeval extensional faulting and graben development. Evaporites in south Cyprus (Maroni sub‐basin) formed in elongate basins between former compressional lineaments created by localized Early Miocene thrusting. In the sub‐basins of west, south‐west and south Cyprus, large‐scale slumping of marginal gypsum facies took place towards depocentres (to form megarudite debris flows), triggered by one or several phases of extensional faulting.