The Messinian evaporites of the Mesaoria basin (North Cyprus): A discrepancy with the current chronostratigraphic understanding

Large volume of evaporites were deposited during the Messinian Salinity Crisis (MSC) across the Mediterranean. These evaporites are currently outcropping on land and are interpreted by seismic profiles beneath the Mediterranean floor. Biostratigraphic, magnetostratigraphic and astrochronologic data recovered from sediments below and above outcropping evaporites, together with gypsum facies associations and stratigraphic cyclicity, are the cornerstone of what is known as the MSC ‘three-stage ’ model: Primary Lower Gypsum (PLG) – MSC stage 1, Resedimented Lower Gypsum (RLG) - MSC stage 2

evaporites in marginal, intermediate-deep and deep Mediterranean basins (Ogniben, 1957;Selly, 1973;Hsü et al., 1973;Ryan, 1976;Clauzon et al., 1996;Krijgsman et al., 1999;Manzi et al., 2013).Over decades, geoscientists have pursued the development of a comprehensive model that would facilitate stratigraphic correlations across the Mediterranean basin (summarized in Rouchy andCaruso, 2006, andRoveri et al., 2014a).However, difficulties have been compounded by the inclusion of the complete MSC event within a sole reversed magnetic chron, absence of precise radiometric ages and shortcomings of biostratigraphic markers.These combined have made difficult to establish stratigraphic and genetic correlations between evaporites formed in marginal and deeper offshore basins.
Based on seismic borehole data and comparison between mostly Sicilian Messinian evaporite successions, a 'two-step' informal division into Lower Evaporites (Lower Gypsum and Halite Unit) and Upper Evaporites (Upper Gypsum) was originally proposed for MSC Mediterranean evaporite deposits (Hsü et al., 1973;Hsü et al., 1977;Cita et al., 1978;Rouchy, 1982;Müller and Mueller, 1991;Butler et al., 1995; those reported for other MSC deposits; and 4) to discuss the integration of the North Cyprus evaporites within the Roveri et al. (2014a) stratigraphic framework proposed for the MSC.
Strontium isotope ratios ( 87 Sr/ 86 Sr) in sedimentary gypsums preserve the isotopic signature of the water source where they precipitated. 87Sr/ 86 Sr in well-mixed ocean waters is homogeneous.The oceanic strontium ratio has changed over geological times as consequence of the balance between different Sr sources (Palmer and Edmond, 1992;Reinhardt et al., 1998;Krabbenhöft et al., 2010;Pearce et al., 2015).
87 Sr/ 86 Sr variations follow a particular trend throughout the MSC deposits.This trend shows a gradual and rapid detachment from the global ocean line (Flecker et al., 2002;Flecker and Ellam, 2006;Topper et al., 2011;Roveri et al., 2014b;García-Veigas et al., 2018).Strontium isotope ratios in Lower Evaporites (PLG and RLG units) are in range, or close, to the global ocean line ( 87 Sr/ 86 Sr: 0.7089-0.7090).Upper Evaporites (UG units) show a marked fall in Sr isotope ratios (0.7087-0.7088) interpreted as linked to the progressive closure of Mediterranean gateways and the increase of freshwater inputs (Flecker et al., 2002;Flecker and Ellam, 2006).
Although sulfate and strontium isotopic signatures in gypsum can be used as good indicators for chemostratigraphic correlations in intermediate and deep basins, mainly fed by marine inputs, the extension towards more marginal basins, with major continental inputs, could be questionable if geochemical end-members are not well constrained.This is the case of the gypsum succession in the Maiella section (Central Apennines), assigned to MSC Lower Evaporites (Sampalmieri et al., 2008;Samplamieri et al., 2010) but reporting some 87 Sr/ 86 Sr values in disagreement with those obtained in most of the MSC Lower Evaporites (Roveri et al., 2014b, and references therein).

Geological setting
The Eastern Mediterranean region consists of several small Neotethyan oceanic basins created and destroyed in a complex geodynamic framework between the African, Arabian and Eurasian lithospheric plates and the smaller Anatolian microplate (Fig. 2) (Kinnaird, 2008;McCay, 2011;Papadimitriou et al., 2018).The island of Cyprus, located in the easternmost part of the Mediterranean region, was formed by the collision and stacking of three main tectonic terranes: the northerly Kyrenia Range, a fragment detached from the southern margin of Anatolian microplate; the central Troodos Ophiolitic Massif; and the southerly Mamonia Complex, a fragment of the continental margin of the African plate (Kinnaird and Robertson, 2012;Papadimitriou et al., 2018).These tectonic terranes form the basement on which several Cenozoic sedimentary basins formed.
The Mesaoria basin is a tectonically active basin, bounded to the north by the Kyrenia Range and to the south by the Troodos Ophiolitic Massif (Fig. 2).The depositional settings of the basin were strongly influenced by the regional tectonic activity (Robertson and Kinnaird, 2016).From the Late Cretaceous (Maastrichtian) to the Oligocene, the island of Cyprus was a deep marine setting where pelagic marls and carbonates (Lefkara Fm.) deposited (Fig. 3) (Robertson and Hudson, 1974;Robertson et al., 1995;Kinnaird et al., 2011).During the Late Eocene, a regional southward thrusting related to the subduction of the northern Troodos oceanic crust beneath the Anatolian microplate (Kyrenia range) resulted in the deposition of debris flows in the foredeep domain (Kalograia-Ardana Fm. -Lapithos Group) (Fig. 3).
The structural evolution of North Cyprus from the Late Eocene to recent times is still unclear.Recent tectonic reconstructions (Kinnaird, 2008;Kinnaird and Robertson, 2012;Robertson and Kinnaird, 2016;Robertson et al., 2019) suggest that northward subduction to the south of Cyprus initiated in the Late Oligocene -Early Miocene causing the uplift of the Troodos Ophiolitic Massif and a progressive shallowing with deposition of the hemipelagic marine carbonates and carbonate reefs of the Pakhna Fm. (Fig. 3) (Kinnaird et al., 2011).
A second convergence phase, during the Middle -Late Miocene, resulted in the Kyrenia thrust belt dock.As a result of the on-going convergence, the foredeep domain between the Kyrenia Range and the Troodos Massif was segmented into two depocenters (Robertson et al., 2019).Fine-grained terrigenous turbidites (Bellapais Fm. -Kythrea Group) (Fig. 3) deposited in the vicinities of the Kyrenia Range.The convergence phase continued during Late Miocene (Messinian) -Early Pliocene (McCay and Robertson, 2013;Robertson and Kinnaird, 2016) resulting in a high subsidence of the Mesaoria basin.The tectonic configuration of the basin, and the progressive restriction of the Atlantic-Mediterrean connection, led to deposition of the Messinian evaporites (Kalavasos Fm.) (Fig. 3), consisting of up to 100 m thick outcropping gypsum deposits, and a salt unit (~ 300 m thick) identified by borehole and seismic profiles in the subsurface of the Mesaoria plain (Gass, 1960;Zomenis, 1972).The Early Pliocene was characterized by a quiescent tectonic period as well as by a transgressive trend causing the deposition of the Nicosia Fm. pelagic sediments (Fig. 3) (Palamakumbura and Robertson, 2016).

Material and methods
This study concentrates on different gypsum successions outcropping in both the southern and northern margins of the Mesaoria basin in North Cyprus (Fig. 2).
More than 50 hand samples and thin sections of gypsum have been studied with petrographic and scanning electron microscopes (SEM-EDS).Several chips of the fine-grained gypsum and of different selenite crystals were selected for SEM-EDS observations and isotopic determinations.
SEM observations have been performed at the Scientific and Technological Centers of the University of Barcelona (CCiTUB) with a FEI Quanta-200 and a Jeol-7100F Field Emission SEM, both equipped with energy dispersive X-Ray spectrometers for elemental identifications (EDS).
Sulfur and oxygen isotope compositions (δ 34 S sulfate and δ 18 O sulfate ) in gypsum samples (n = 30) have been determined at the CCiTUB.Gypsum samples were dissolved in ultrapure water, filtered to remove insoluble material and acidified to pH 3 to eliminate carbonates.Dissolved sulfate was reprecipitated as BaSO 4 by addition of a BaCl 2 solution.Isotope determinations were performed with an ISOGAS Sira-9 Spectrometer and a Thermo Finnigan Delta Plus XP Spectrometer.The analytical error (2σ) is ±0.3‰ for δ 34 S and δ 18 O.Values obtained for the international standard NBS-127 are δ 34 S: 20.3 ± 0.1‰ and δ 18 O: 9.3 ± 0.2‰.
The 87 Sr/ 86 Sr in gypsum samples have been measured at the University of Queensland, Australia.Dissolved samples in 2 N HNO 3 were loaded onto columns pre-filled with 0.19 ml of Eichrom Sr-spec resin (50-100 μm).The Sr was released from the columns and collected using 2.8 ml 0.05 N HNO 3 .The Sr concentrations were then screened on a Thermo X-series II quadrupole Inductively Couple Plasma Mass Spectrometer (ICP-MS).Based on the screened results, a 3 ml dilute aliquot in 2% HNO 3 (vol/vol) was made for each sample for measurement of Sr isotopic compositions on a Nu Plasma HR Multi-collector ICP-MS.Mass fractionation were corrected by normalizing the raw ratios to 86 Sr/ 88 Sr = 0.1196.Repeated measurements of a SRM-987 standard solution of a similar concentration to the samples was measured every five samples giving 87 Sr/ 86 Sr ratios of 0.710249 ± 0.000006 (2σ, n = 4).

Gypsum lithofacies in the Mesaoria basin
In North Cyprus, the MSC evaporites of the Mesaoria basin crop out in the northern margin along a 150 km 2 E -W area in up to 22 gypsum quarries (Necdet and Anıl, 2006;Varol and Atalar, 2017).However, only few, gypsum successions crop out in the southern margin of the basin, close to the Troodos Ophiolitic Massif (Fig. 2).
Gypsum in North Cyprus MSC deposits can be grouped into three main groups of lithofacies: 1) fine-grained laminated gypsum, 2) vertically-oriented selenites, which include massive and banded selenite facies (Babel, 2007, Lugli et al., 2010) and selenite clusters, and 3) clastic gypsum, including gypsarenites and gypsirudites.Fine-grained laminated gypsum lithofacies, labeled "Marmara" in Cyprus, have been considered by Robertson et al. (1995) and Roveri and Manzi (2006) equivalent to the "Balatino" term used in Italy.The Marmara gypsum consists of fine-laminated gypsum formed by alternating darker and lighter laminae (mm -cm size).The darker laminae are composed by gypsum crystals mixed with micritic carbonate (mostly dolomite), while lighter laminae are mainly formed by gypsum.Under the microscope gypsum laminae are made up of two different gypsum microfacies.The most common microfacies consist of prismatic equant gypsum crystals (50-200 μm size) showing blocky texture, the other consist of acicular gypsum crystals (< 0.5 mm long) displaying horizontal parallel elongations.Framboidal pyrite and celestine crystals are locally abundant.
Crystalline gypsum nodules, coalescing to form parallel enterolitic structures, show a displacive growth deforming the fine-grained lamination (Fig. 4a).These nodules consist of radial aggregates of prismatic elongated primary gypsum crystals (mm size) without any evidence of anhydrite precursor.
Banded selenite intervals consist of vertically-oriented twinned crystals (cmdm size) displaying competitive growth.The bottom of each bed generally shows longer crystals.Individual gypsum beds are separated by thin layers of fine-grained gypsum or carbonate laminae (mostly dolomicrite).
Massive selenite beds are equivalent to the "swallow-tail gypsum" term used by Robertson et al. (1995) and to the "non-bedded selenites" of Varol and Atalar (2017).It consists of columns made of twinned gypsum crystals adjacent and stacked one upon another showing a continuous competitive vertical development.Selenite columns growth concurrently, parallel to each other, forming thick selenite beds, more than 0.3 m long (Lugli et al., 2010) and up to 5 m long (giant selenites).Often, the base and top of massive selenite beds contain subhorizontal or randomly oriented crystals.Most selenite crystals show a brownish core with microfilaments resembling the 'spaghetti-like filaments' described in Northern Apennines (Vai and Ricci Lucchi, 1977) and Sicily (Rouchy and Monty, 1999).
Selenite clusters consist of vertically-oriented or non-oriented twinned gypsum crystals (cm-size) growing within fine-grained laminated gypsum and gypsarenite beds (Fig, 4c).They usually show a displacive deformation although locally break the original lamination (Fig. 4d).The lateral growth of several vertically-oriented clusters can coalesce forming selenite layers.
In this work, the terms 'gypsarenite' and 'gypsirudite' are used with genetic connotation in the sense of clastic gypsum deposits resulted from erosion, transport and resedimentation processes.
Gypsarenite beds consist of gypsum crystals with minor carbonate crystals (mainly dolomite), mud and fossils (diatoms and coccoliths) possibly reworked due to the clastic nature of the sediments.Usually, gypsarenites alternate with fine-grained laminated gypsum beds.Parallel laminations, ripples and cross laminations are often recognized (Fig. 4b).
Gypsirudites show clast-supported fabrics mainly made by broken, abraded or partly dissolved selenite crystals (Fig. 4e).Scattered clasts of fine-grained laminated gypsum, often showing internal soft-sediment deformation, are also frequent (Fig. 4f).Selenite clasts contain 'spaghetti-like' filaments characteristics of the related 'in situ' selenite deposits.

Mesaoria gypsum successions
Most of the Mesaoria gypsum deposits are buried in the subsurface and therefore not accessible (Gass, 1960;Cleintuar et al., 1977).Outcropping gypsum deposits of the Kalavasos Fm. do not show a complete evaporitic succession.Four stratigraphic sections (Türkeli -Agios Vesileios, Kanli Tepe, Akova -Gypson and Kalecik -Gastria) have been studied in the northern margin of the Mesaoria basin, whereas only one (Kato Moni) in the southern margin.The Kato Moni section corresponds to that previously studied by Pierre (1982) and Manzi et al. (2016).General views, locations, outcrop pictures and primary data (geochemical data and microphotographs) are included as Supplementary Material.
The Türkeli section (Fig. 5) corresponds to one of the westernmost gypsum quarries in the northern margin of the Mesaoria basin (Fig. 2).Hemipelagic marls of the Pakhna Fm., containing a dark purple stratiform manganese deposit (5 m thick), are observed in the base of the quarry.The contact between the Pakhna Fm. and the Kalavasos Fm. is a conformity at the outcrop scale.The gypsum succession is separated in a lower interval (20 m thick) of fine-grained laminated gypsum alternating with gypsarenites, and an upper (7 m thick) gypsirudite interval.Elemental sulfur nodules occur scattered within the lower gypsum interval.δ 34 S sulfate and δ 18 O sulfate data of the Türkeli gypsum show values of δ 34 S ~ 23‰ (23.3-24.1‰)and of δ 18 O ~ 14‰ (13.7-14.9‰).
The Kalecik quarry (Fig. 8), 10 km E of the Yeni Iskele village, shows the most complete succession of the Kalavasos Fm. in the Mesaoria basin.Up to 100 m of concordant gypsum beds crop out along two continuous gypsum quarries, one (old quarry) on top of the other (new quarry).The older quarry was previously described by Varol and Atalar (2017).The new quarry, stratigraphically below, has been recently exposed by mining operations.The evaporitic succession, in the new quarry, consists of a 30 m thick interval of gypsirudites and gypsarenites alternating with fine-grained laminated gypsum beds.Enterolitic layers of crystalline radiating gypsum and sulfur nodules occur in the lowermost part.A fine-grained laminated gypsum bed, 5 m thick, is recognized in both the top of the new quarry and at the base of the older quarry.The old quarry shows the uppermost 70 m of the evaporite succession and consists of a lower mixed (laminated to disoriented and vertically-oriented selenites) gypsum bed followed by six verticallyoriented selenite beds (between 7 and 15 m thick) of banded and massive lithofacies, separated by fine-grained gypsum intervals (between 0.5 and 1 m thick).Pliocene marine sediments rest conformably, at the outcrop scale, over the gypsum beds of the old quarry.δ 34 S sulfate and δ 18 O sulfate data of the Kalecik gypsum beds show δ 34 S values ~23‰ (22.6-23.6‰).However, the δ 18 O profile can be divided in two different parts.The lower part, characterized by clastic gypsum beds, shows δ 18 O values ~12‰ (11.8-13.7‰)while, the upper part, represented by vertically-oriented selenites, has values of ~13‰ (12.6-13.5‰).Strontium isotope ratios in the Kalecik gypsum do not show differences between the new and old quarries, with values ~0.7089 (0.70894-0.70896).

North Cyprus MSC evaporites: Genetic and stratigraphic relationships
In North Cyprus, the Messinian evaporites of the Kalavasos Fm. largely consist of 'in situ' gypsum beds precipitated/grown in the place where they are found, and clastic gypsum beds transported and resedimented away from where originally precipitated.
Fine-grained laminated gypsum can correspond both to 'in situ' or to clastic facies.As 'in situ' facies, fine-grained gypsum crystals nucleate from a sulfate oversaturated brine, falling and accumulating on the basin floor (Garber et al., 1987;Krumgalz, 2019).As resedimented facies, finegrained gypsum crystals can be transported towards deeper sites.Finegrained 'balatino' gypsum deposits in the Northern Apennines, previously interpreted as deep-water primary gypsum deposits, are now considered clastic deposits formed by gravitational flows (Manzi et al., 2005).In the absence of other clastic evidence (detritic clasts, crossbedding, ripple marks, etc.) we interpret fine-grained gypsum beds as 'in situ' cumulate deposits when intercalate between bottom-grown vertically-oriented selenite beds, and as clastic deposits when intercalate between gypsarenites and gypsirudites.
Gypsarenites and gypsirudites of the Kalavasos Fm. in North Cyprus are interpreted as gravity-flow gypsum deposits.These clastic gypsum deposits derived from the erosion and resedimentation of verticallyoriented selenite gypsum deposits previously formed on shallower marginal surrounding areas (Fig. 10).Instabilities in the marginal selenite platforms, tectonic and/or eustatic in origin, led to the erosion of marginal selenite deposits resedimented basinward as gravity-flow gypsum deposits (Fig. 10).
A correlation chart of the North Cyprus Kalavasos Fm. is proposed in Fig. 11.A bed-to-bed correlation has not been possible because the long distance between outcrops and the absence of key beds.The North Cyprus MSC gypsum succession is subdivided in two different units.The lower unit, best represented in westward sections (Türkeli, Kanli Tepe), mainly consists of clastic gypsum facies, whereas the upper unit, well Fig. 7. Akova gypsum section.Sulfur, oxygen (in sulfate), and strontium isotope profiles.Shaded areas correspond to expected values for Late Miocene marine evaporites (Claypool et al., 1980;Paytan et al., 1998;Roveri et al., 2014b).The stratigraphic succession in North Cyprus, with deeper clastic gypsum deposits followed upwards by 'in situ' selenite platforms represents a shallowing regressive trend (Fig. 12).Selenite platforms, initially formed in marginal areas, were eroded during the relative sealevel drop and resedimented as gravity-flow gypsum deposits in deeper Fig. 9. Kato Moni gypsum succession.Sulfur, oxygen (in sulfate), and strontium isotope profiles.Shaded areas correspond to expected values for Late Miocene marine evaporites (Claypool et al., 1980;Paytan et al., 1998;Roveri et al., 2014b).areas.As the sea level continued to drop, the staked clastic lobes were subsequently overlaid by younger selenite platforms.

Geochemical signatures in the Mesaoria evaporites
Isotopic gypsum data in the North Cyprus Kalavasos Fm. are very homogeneous and do not show significant differences between the stratigraphic lower (gravity-flow gypsum deposits) and upper (selenite platform deposits) units.Isotope compositions in gypsum sulfate are of δ Strontium isotope ratios in North Cyprus evaporites (~ 0.7089) are in range with those reported for Lower Evaporites (PLG and RLG deposits in the 'three-stage' model) (Roveri et al., 2014b, and references therein).
According to sulfur, oxygen (in sulfate), and strontium isotope data, we interpret that the entire evaporite succession in North Cyprus (Mesaoria basin) corresponds to the MSC Lower Evaporites in the classical 'two-step' lithostratigraphic division.In our opinion, differentiation between PLG and RLG is isotopically questionable because RLG deposits are, in origin, evaporites precipitated during MSC stage 1 and then resedimented during MSC stage 2 (Roveri et al., 2008b(Roveri et al., , 2014a)).No isotopic fractionation occurs during gypsum resedimentation so, gypsum deposits of both stages should keep the same sulfate and strontium isotope signatures.Roveri et al. (2014a) MSC clastic gypsum deposits assigned to the RLG (MSC stage 2) in the Roveri et al. (2014a) model are recognized either in western (Sicily and North Apennines) and eastern (Greece and South Cyprus) Mediterranean.In this chronostratigraphic model, RLG (MSC stage 2) deposits post-date the 'in situ' vertically-oriented selenite sequences of the PLG (MSC stage 1) unit.According to this model, the main phase of the erosion (MES) entirely follows the deposition of the PLG.This phase is linked to the subaerial exposure of the basin margins following the deterioration of the Atlantic-Mediterranean exchange and the consequent drop of the Mediterranean base-level.However, RLG deposits are never found laterally or vertically in continuity with PLG deposits.Where both PLG and RLG deposits are recognized in the same basin, they are always separated by faults, thrust fronts or other structural elements as occurs in the Northern Apennines (Manzi et al., 2007) or North Sicily (Roveri et al., 2008a).
In the North Cyprus Mesaoria basin, the lower unit of the Kalavasos Fm. consists of clastic gypsum similar to those reported for RLG units in Northern Apennines (Manzi et al., 2007) and South Cyprus (Manzi et al., 2016), whereas the upper unit shows vertically-oriented selenite gypsum lithofacies characteristic of both PLG and UG units.
Tentatively, following the 'three-stage' model of Roveri et al. (2014a), the lower part of the North Cyprus gypsum succession could be assigned to the RLG unit, and the upper to the UG unit.However, the upper part does not show the characteristic stacking pattern (gypsummarl cycles) and does not contain Lago Mare flora and fauna typical of the UG deposits in Sicily and South Cyprus (Rouchy et al., 2001;Manzi et al., 2009Manzi et al., , 2016;;Roveri et al., 2014a).Furthermore, our geochemical data show that the upper part is consistent with isotopic values found in other vertically-oriented selenite deposits assigned to the PLG deposits.The PLG assignation of the upper part, conformably overlying clastic gypsum tentatively assigned to RLG deposits, conflicts with the gypsum lithostratigraphic succession proposed in the Roveri et al. (2014a) model.
Based on lithostratigraphic and isotopic data, we assign the complete gypsum succession of the Kalavasos Fm. in North Cyprus to the MSC Lower Evaporites in the sense of the classical stratigraphic division (Lower and Upper Evaporites) summarized and outlined in Rouchy and Caruso (2006).The Roveri et al. (2014a) chronostratigraphic model, mainly based on Sicily, cannot be applied to the North Cyprus Messinian evaporites.
Our assignation implies that, at least in North Cyprus, verticallyoriented selenite platforms tentatively assigned to the PLG in the Roveri et al. (2014a) model underwent erosion coevally with its formation.Selenite platforms, eroded and resedimented, and subsequently overlaid by younger selenite platforms must be considered within the same MSC chronostratigraphic unit.

MSC evaporites in North and South Cyprus
In South Cyprus, three gypsum lithostratigraphic units are recognized in the Messinian Kalavasos Fm.: Lower Gypsum, Intermediate Gypsum Breccia, and Upper Gypsum (Rouchy, 1982;Pierre, 1982;Robertson et al., 1995;Rouchy et al., 2001;Orszag-Sperber et al., 2009).In these works, assignation of each gypsum unit to the classic MSC stratigraphic division (Lower Evaporites and Upper Evaporites) is suggested rather than concluded.Rouchy et al. (2001) identify Lago Mare fauna assemblages, similar to those reported from other Mediterranean basins (Andreetto et al., 2021, for a review), in the latest intergypsum intervals and in the post-evaporitic deposits.
Recently, Manzi et al. (2016) recognize a clastic origin for most gypsum beds of the Lower Gypsum in South Cyprus, identify the Messinian Erosional Surface at its base, and propose the assignation of the Lower Gypsum and the Intermediate Gypsum Breccia units to the RLG deposits (MSC stage 2) in the Roveri et al. (2014a) model.Based on lithological features and strontium isotope ratios, these authors assign the selenite-bearing Upper Gypsum unit of Rouchy (1982) to the UG unit (MSC stage 3) in the Roveri et al. (2014a) model.
In North Cyprus, the work of Manzi et al. (2016) is limited to the study of the Kato Moni section (Fig. 9), in the southern margin of the Mesaoria basin (Fig. 2).Based on gypsum lithofacies and on an interpreted stratigraphic unconformity assigned to the Messinian Erosional Surface (MES), they suggest that this small gypsum outcrop belongs to the UG unit (MSC stage 3).We disagree because the Kato Moni gypsum succession does not show the marked marl-gypsum cyclicity characteristic of the UG deposits (Manzi et al., 2009;Roveri et al., 2014a), there are not 87 Sr/ 86 Sr isotope data and/or Lago Mare records supporting this assignation and lastly, the interpreted erosional surface probably corresponds to a tectonic control.Some lithological similitudes, but important geochemical differences, exist between the gypsum successions assigned to the different MSC units/ stages in South (Polemi, Pissouri, and Maroni basins) and North (Mesaoria basin) Cyprus.The lower part of the evaporite succession, in both North and South Cyprus, is characterized by clastic gypsum deposits with sulfate and strontium isotope signatures in range with other MSC Lower Evaporites.However, important differences exist in the upper part of each evaporite succession.In South Cyprus, the upper part shows facies associations and isotope data similar to those reported for Upper Evaporites -UG (MSC stage 3) deposits in Sicily.However, in North Cyprus, the upper part is characterized by facies association, and isotope signatures in range with Lower Evaporites -PLG and RLG (MSC stages 1 and 2).Manzi et al. (2016) propose a North Cyprus -South Cyprus geological correlation of the MSC evaporites (Fig. 13).Although their observation is only limited to the Kato Moni gypsum quarry in North Cyprus, where clastic gypsum deposits do not crop out, they recognize extensive RLG and UG units in both parts of the island.We propose a new correlation chart (Fig. 13) in which Lower and Upper Evaporite deposits, in the sense of the classical MSC stratigraphic division, are represented in South Cyprus, and only Lower Evaporite deposits in North Cyprus.

Conclusions
Despite the current use of the unifying three-stage litho-and chronostratigraphic frame (PLG, RLG, and UG) proposed by Roveri et al. (2014a) to different MSC gypsum deposits across the Mediterranean, marked differences exists between the MSC gypsum successions recorded in South (Polemi, Pissouri and Psemastimenos basins) and North (Mesaoria basin) Cyprus.
Correlative sections in the northern margin of the Mesaoria basin divide the North Cyprus MSC gypsum succession in two gypsum units.Following the Roveri et al. (2014a) model, the lower unit, mainly consisting of clastic gravity-flow gypsum deposits, could be tentatively assigned to RLG deposits (MSC stage 2).Whereas, the upper part, characterized by 'in situ' vertically-oriented selenite beds, should be assigned to PLG deposits (MSC stage 1).
The complete Kalavasos Fm., in North Cyprus, is characterized by homogeneous sulfur and oxygen (in sulfate) isotope compositions (δ 34 S ~ 23‰ and δ 18 O ~ 13‰) and strontium isotope ratios ( 87 Sr/ 86 Sr ~ 0.7089).These values match those reported for MSC Lower Evaporites in the classic 'two-step' model (Rouchy and Caruso, 2006, for a review) that integrate PLG (MSC stage 1) and RLG (MSC stage 2) deposits in the 'three-stage' model of Roveri et al. (2014a).Unlike in South Cyprus, Upper Evaporites -Upper Gypsum (MSC stage 3) deposits are absent in the North Cyprus Mesaoria basin.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
D.Artiaga et al.   preserved in the eastward sections (Kato Moni, Akova, Kalecik) mainly consists of 'in situ' vertically-oriented selenite facies.Both parts are well exposed in the Kalecik section.

Fig. 11 .
Fig. 11.Correlation chart of MSC gypsum sections of the Kalavasos Fm. in the Mesaoria basin (North Cyprus).

Fig. 12 .
Fig. 12. Evolutive model for the gypsum succession of the Kalavasos Fm. in the Mesaoria basin (North Cyprus).
The evaporite succession in North Cyprus, with clastic gravity-flow gypsum deposits overlaid by 'in situ' selenite gypsum platforms, both geochemically assigned to MSC Lower Evaporites in the classical lithostratigraphic division, raised concerns to the extension of the currently accepted 'three-stage' model to other MSC Mediterranean basins where local tectonics, bathymetric and paleogeographic factors could led to different gypsum facies distributions.