Depositional processes and basin analysis of Messinian evaporites in Cyprus

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.

The onset of the Messinian salinity crisis in the Eastern Mediterranean (Pissouri Basin, Cyprus)

“…Two to three sedimentary cycles consisting of stromatolitic limestones are found beneath the ¢rst gypsum. This stromatolite-bearing interval directly below the evaporites is also observed in the adjacent basins of Psematismenos and Polemi where they are locally intercalated with thick megabreccia beds [12,15,17]. Evaporite deposition during the MSC on Cyprus is thus preceded by an approximately 60-kyr transitional interval of deteriorating environmental conditions.…”

“…This change in basin con¢guration re£ects tectonic instability related to both the uplift of the Troodos Massif [18] and the position of Cyprus in a fore-arc setting within the complex zone of convergence between Africa and Eurasia [16,19]. The Messinian evaporites were deposited in these sub-basins at a time when the African plate was undergoing northward subduction beneath Eurasia [17].…”

“…The Neogene sedimentary sequence on Cyprus shows a gradual shallowing from Palaeocene^Oli-gocene deep-water pelagic carbonates (Lefkara Formation [20]), through mixed detrital and carbonate sediments (Pakhna Formation [21]) and reefal limestones (Koronia Member [22]), to the Messinian evaporites [12,17]. Deeper water conditions were re-established at the beginning of the Pliocene before renewed shallowing in middle Pliocene times [17,23].…”

“…Deeper water conditions were re-established at the beginning of the Pliocene before renewed shallowing in middle Pliocene times [17,23]. The Messinian sedimentary succession of Cyprus is characterised by pre-evaporitic deposits, overlain by two gypsum units which are separated by a breccia [12,17].…”

The Miocene–Pliocene boundary and the Messinian Salinity Crisis in the easternmost Mediterranean: Insights from the Hatay Graben (Southern Turkey)

“…Furthermore, Roveri et al (2014a, b) This revised Messinian scenario is described within the framework of a 3-stage stratigraphic model constructed mainly with observations from the marginal to intermediate basins exposed onshore in Sicily and in the Northern Apennines (CIESM, 2008;Roveri et al, 2014a, b). However, despite the extensive 'back-catalogue' of work on the Messinian stage (e.g., Roveri et al, 2014a), many studies from the easternmost extent of the Mediterranean have focussed on Cyprus (e.g., Robertson et al, 1995;Krijgsman et al, 2002;Kouwenhoven et al, 2006;Orszag-Sperber et al, 2006;Manzi et al, 2015) and adjacent ODP data (e.g., Blanc-Valleron et al, 1998;Pierre et al, 1998), with limited data from southern Turkey Darbaş and Nazik, 2010;Poisson et al, 2011;Cipollari et al, 2013;Faranda et al, 2013;Radeff et al, 2015). In this paper we focus on late Miocene and early Pliocene sediments of the Hatay Graben (southern Turkey), previously identified by Boulton et al ( , 2008 and Tekin et al (2010).…”