Journal articles on the topic 'Messinian salt'

ABSTRACT A multi-client 2-D seismic survey, consisting of 6,770 line-kilometer of 2-D data, was acquired by Norway’s PGS Geophysical offshore Cyprus in 2006. It was followed in 2006 and 2007 by the acquisition of two 3-D surveys, located offshore Lebanon (1,500 square kilometers), and offshore Lebanon and Cyprus (1,300 square kilometers). Further, in 2008 an additional 2-D survey was acquired offshore Cyprus to fill in the existing 2006 seismic 2-D grid. The 2008 2-D survey consist of 6,500 line-kilometer and was acquired with the PGS dual sensor GeoStreamer® technology (The 2008 2D data is still being processed so no GeoStreamer® examples are shown in this article). Since 2007, some of the deep-water areas (1,500–2,000 meters deep) offshore Cyprus have been offered for exploration and producing bid licenses by the government, while the Lebanese government is in the stage of preparing its offshore region for exploration and licensing. In this paper, several representative seismic lines are shown to illustrate the quality of the seismic data over this large region. The data shows that a Pliocene to Recent succession overlies a thick Upper Miocene evaporite section, known as the Messinian Salt. The blanketing salt-dominated interval is up to one kilometer thick and provides a regional seal over the area; although some faults are known to penetrate the salt and may allow seepage to occur. The pre-Messinian Salt section is highly structured, with both horsts-and-grabens as well as large folds. In particular, several examples of seismic reflections are presented, which are interpreted as possible Direct Hydrocarbon Indicators (DHI). Some four-way structural closures are highly prospective as they are characterized by multiple DHIs; for example, a bright spot at the base of the Messinian Salt overlying a flat spot. Other examples consist of phase changes, dim spots, velocity pull-downs, low-frequency shadow zones and gas chimneys. Also shown are how some of these interpreted DHIs can be characterized in the 3-D surveys. The 3-D example illustrate a correlation between pre-Messinian four-way structural closure and the root-mean square amplitude of the base Messinian Salt reflection.

We use 3D seismic reflection data from the Levant margin, offshore Lebanon to investigate the structural evolution of the Messinian evaporite sequence, and how intra-salt structure and strain varies within a thick salt sheet during early-stage salt tectonics. Intra-Messinian reflectivity reveals lithological heterogeneity within the otherwise halite-dominated sequence. This leads to rheological heterogeneity, with the different mechanical properties of the various units controlling strain accommodation within the deforming salt sheet. We assess the distribution and orientation of structures, and show how intra-salt strain varies both laterally and vertically along the margin. We argue that units appearing weakly strained in seismic data may in fact accommodate considerable subseismic or cryptic strain. We also discuss how the intra-salt stress state varies through time and space in response to the gravitational forces driving deformation. We conclude that efficient drilling through thick, heterogeneous salt requires a holistic understanding of the mechanical and kinematic development of the salt and its overburden. This will also enable us to build better velocity models that account for intra-salt lithological and structural complexity in order to accurately image sub-salt geological structures.

The definition of pre-Messinian source rocks in the eastern Mediterranean is of paramount importance for hydrocarbon exploration because of the ability of salt to act as a high-quality seal rock. This research evaluates the organic geochemical features of the Upper Miocene (Tortonian—Messinian) sedimentary succession onshore Crete Island, Greece. The study employs original (Messinian, Agios Myron Fm) and published (Tortonian, Viannos Fm, Skinias Fm, Moulia Fm, and Messinian Ploutis section) results from organic geochemical analyses of mudstone samples. One hundred and one samples were examined using standard organic geochemistry methodology (Rock-Eval II and VI-TOC) to define the origin, type, and degree of organic matter maturity. The data indicate that the studied samples have poor to fair gas-prone source rock potential. These possible source rock units have not experienced great temperatures during burial, and, thus, their organic matter is thermally immature. The sub-salt (Tortonian—Messinian) source rock units are likely to be of higher thermal maturity in the western and eastern south Cretan trenches because of tectonic subsidence and a thicker sedimentary overburden. Several traps can grow in these regions, associated with normal faults, rotated blocks and unconformities (both below and above the unconformities). This research provides a basis for the further evaluation of the hydrocarbon potential in Crete Island. It is an area that shares geological similarities with the surrounding regions that contain proven reserves and is of crucial economic and strategic importance.

This study investigates the interplay of evolving tectonic and submarine sedimentation processes in the northwest Aegean Sea using marine multichannel seismic profiles. We identify an extensive basin developing in the Thermaikos Gulf inner shelf, outer shelf, and slope leading to the 1500 m deep West North Aegean Trough (NAT). We establish the unconformable extent of Eocene and Oligocene sequences on the upper shelf and trace their continuation in the deeper shelf and slope of Thermaikos Gulf. The start of the Miocene and Middle Miocene developed below the well-established Messinian bounding reflectors that are mostly erosional. Important lateral variations are observed within the Messinian sequence, which is up to 0.8 s thick. Messinian prograding clinoforms are identified on the Thermaikos Gulf shelf and southeast of Chalkidiki, and a zone of irregular reflectors is attributed to the Messinian salt layer. The transpressional deformation of the Messinian in the southwestern margin constrains the timing of westward progradation of the North Anatolian Fault during Messinian. The Pliocene-Quaternary sediments are 0.6–1.8 s thick, showing the overwhelming effect of tectonics on sedimentation plus the northwards Quaternary activation at the Thermaikos apron.

ABSTRACT The deepwater area of the Nile Delta is within the eastern Mediterranean basin on the Nile Delta Cone between the Herodotus abyssal plain to the west and the Levant basin to the east. The complex evolution and interaction of the African, Eurasian and Arabian plates have shaped the Late Miocene to Recent Nile Cone and its substratum. The tectono-stratigraphic framework is controlled by deep-seated basement structures with distinct gravity and magnetic expressions, and by the interaction of the NW-trending Misfaq-Bardawil (Temsah) and NE-trending Qattara-Eratosthenes (Rosetta) fault zones. In addition, significant salt-induced deformation of a Messinian evaporitic sequence up to 4,000 m thick has occurred, together with large-scale rotational block movement. The deformational pattern is largely the result of multiphase tectonic movements along pre-existing basement faults on the continental margin of the Neo-Tethys ocean. The Nile Cone consists of late Paleogene to Late Miocene sediments that pre-date the Messinian evaporites, and Pliocene-Pleistocene sequences. In the east, the pre-salt deposits (as much as 3,000 m thick) are primarily deepwater sediments with local condensed sequences over syndepositional intrabasinal highs. Shale occurs westward across the Rosetta trend. The Messinian evaporitic sequence exhibits three distinct seismic facies suggesting cyclic deposition with the occurrence of interbedded anhydrite, salt and clastic sequences and pure halite deposition. During the Messinian salinity crisis, large-scale canyons were excavated that resulted in multiphase cut-and-fill clastic systems. The Pliocene-Pleistocene sequences were deposited in a slope to basin-floor setting. Exploration targets are the Pliocene-Pleistocene deepwater channel and basin-floor turbidite sands in a variety of structural settings. Water depths range from 800 to 2,800 m. The Upper Miocene sequence offers additional exploration objectives in the form of fluvial and/or turbidite sands. The focus of pre-salt exploration is the delineation of distal turbidities within the Serravallian to Tortonian sequence and the identification of new reservoir sequences deposited on pre-existing intrabasinal highs. Hydrocarbon charge has yet to be proven by drilling, but seismic amplitude anomalies and the occurrence of natural surface slicks suggest both gas and liquid charges from pre-salt source rocks through faults and salt-withdrawal windows.

Abstract Three-dimensional seismic imaging and well calibration reveal a large allochthonous mud edifice that is composed of several mud extrusions and covers an area >740 km2 on the outer shelf slope of the Nile Delta. The allochthonous material was sourced from beneath the ∼1-km-thick Messinian evaporites in the Eastern Mediterranean and extruded synchronously as eight large mud volcanoes directly on top of the Messinian evaporites in a catastrophic remobilization event at the end of the Messinian salinity crisis. These large extrusive flows coalesced to form a single edifice with an exceptional volume of ∼292 km3 that is connected to eight widely spaced conduits. We argue that this large mud body represents a new morphological type and scale of mud extrusion. We propose that mud extrusions that coalesce on a surface forming a multi-conduit-fed edifice be referred to as mud canopies, by analogy with salt canopies, with implications for basin reconstruction, paleo–overpressure release events, and fluid migration.

Based on the geodynamic context, two hypotheses of origin of salt in the subsurface of the Sahel area are worth being defended. The first suggests that the halokinesis activities, namely, of the Triassic evaporitic sedimentation, may still be until now influencing the functioning of the saline systems in the Sahel. The second integrates the Sahel area geodynamic evolution in the framework of the convergence between African and Eurasian plates. It suggests a link between the blockage of the subduction between African and Eurasian plates in North Tunisia, the Messinian Salinity Crisis, and eventually the concrete opening and evolution of the playa during the Quaternary. Such a suggestion is materialized by a geodynamic model relating successively these events. This scenario suggests that the Messinian Salinity Crisis constituted huge quantities of salt and/or salty water. This saline subsurface reserve is until now influencing the Sahel behavior as a whole. Through groundwater convergence, huge quantities of salt are accumulated within depressions of the Sahel area. Currently, the convergence of the plate between African and Eurasian plates results in a tectonic activity within these saline systems materialized by the formation of fault spring mounds along preferential orientation ensuring the surface-subsurface connectivity.

Abstract The Messinian salinity crisis (MSC) is characterized by gigantic erosion that remodels the margins while a thick, essentially evaporitic and detrital, sedimentary sequence forms in the deep basins. Based on recent (MAURESC, 2003) and earlier (MESEA 1, 1990; MAGIRAA, 1996; GEOBREST, 2002) seismic reflection data, this work brings to light the record of the MSC on the Provençal margin, which has until now been rarely explored from this perspective. Beyond its strictly regional interest, this study fits into a larger synthesis of MSC seismic markers in the Mediterranean and Black Sea marine domain [Lofi et al., 2011] and employs the new nomenclature established on this occasion. The results obtained reveal a Messinian detrital body (CU unit) of 625 metres maximum thickness at the foot of the margin, accumulating at the mouths of the principal canyons. Its form, facies and extension assimilate it to clastic fans, fed by subaerial erosion linked to the MSC. The relative geometry of CU and the Messinian units MU and UU deposited in the deep basin give indications to their chronostratigraphic relations. The deposition of the CU unit is posterior to the basal part of the mobile unit consisting of halite (MU), but contemporary to its top. These results agree with the recent scenarii, which propose that the precipitation of MU in the basin began early, during the lowering of the sea level, and ended at a low level during the MSC [Blanc, 2000; Martin et al., 2001; Sage et al., 2005; Ryan, 2009]. The UU unit surmounts MU and is subdivided into two sub-units with perceptibly different seismic facies : UU1 at the base and UU2 at the summit. UU1 could correspond to a unit containing more halite and/or more clastic material than UU2. The UU1 sub-unit could be partially contemporary to the CU unit. Concerning salt tectonics and its markers, three structural provinces have been evidenced in the sector of study, respectively : an upslope domain in extension (normal faults), an intermediary domain in translation (tabular MU) and a downslope domain in contraction (salt diapirs). These domains are directly linked to the gravity spreading and/or gliding of the brittle sedimentary cover formed by the CU, UU and Plio-Quatenary units and of the mobile level, MU. In the study area, a close relation between the distribution and thickness of CU and salt tectonics has additionally been evidenced at the mouths of the large Messinian canyons, being best expressed where CU is thick.

Abstract There is a growing consensus that the sulfates and halite within the massive evaporite deposits on the shallow margin and deep floor of the Mediterranean sea formed in two steps. Both phases had geodynamic consequences. The current evidence indicates that during the first step when the first cycle “Lower Evaporites” were deposited primarily in marginal settings, the surface of the Mediterranean remained at or very close to the level of the external Atlantic. The geodynamic response resulted from the increasing weight of the brine layer as it concentrated from normal marine salinity to the threshold for sulfate precipitation and then to the threshold for halite precipitation. This weight alone significantly deepened the Mediterranean basins by isostatic loading. Flexure of the lithosphere caused a peripheral bulge to appear that may have been the agent to close off the further entry of Atlantic seawater. Step two began with the subsequent evaporative drawdown and the deposition of the second cycle “Upper Evaporites”. As the basins dried out the loss of weight of the water led to regional isostatic uplift that permanently closed the prior inlets. Sediments removed from the margins by early subaqueous mass-wasting and later subaerial erosion and delivered to the basin floors further accentuated uplift of the margins and subsidence of the depocenters. The principal result has been to progressively tilt the Mediterranean substrate downwards from the margin towards the basin centers. This tilting was enhanced with the flooding of the desiccated sea at the climax of the salinity crisis. Consequently the salt layer rests today out of equilibrium on a surface that is more inclined after precipitation than before. The current mobility and flowage of the salt away from its margins and towards the basin centers is therefore not so much a response to the differential thickness and weight of overlying sediments, but to the combination of geodynamic processes that have produced the seaward tilting. Other giant salt deposits seem to have experienced a similar two-step evolution.

In the article the ancient geological processes of transporting a huge volume of water (up to 2500 km3/year), whereby the Paratethys Sea and the Manych, Bosporus and Dardanelles straits was formed, are regarded as deterministic physical processes. In our opinion, these processes can be studied by mathematical modeling. 5 million years ago, similar events happened in the Mediterranean Sea. At the beginning of the Messinian Salt Crisis, as a result of uncompensated evaporation, the sea dried up to depth of approximately 1700 m, and then, after the formation of the Gibraltar Strait and the breakthrough of the ocean waters, the sea again was filled by the ocean water. It is shown that about 100 km3/year of water during the glacial period, 200 km3/year during the climatic optimum, and up to 2200 km3 year during the glacial melt period came from the Paratethys Sea to the Mediterranean Sea. During the Messinian crisis, the freshening of the water of the Eastern Basin was observed and favorable conditions for freshwater faunawere created.

About 6 million years ago, the Mediterranean basin was the location of one of the most extraordinary events in the recent geological history of the Earth: the Messinian Salinity Crisis. Restriction of the seawater exchange between the Atlantic and the Mediterranean led to excess evaporation and deposition on the bottom of the deep Mediterranean basins of a 1.5 km-thick salt layer. Research on this event initiated a long-term scientific controversy. COST (European Cooperation in Science and Technology) and Marie Skłodowska-Curie European Training Networks were identified as the most appropriate tools to address and solve the controversy using a highly cross-disciplinary approach.

Interpretation of seismic profiles and results of scientific drillings in the Mediterranean subseafloor provided indication of gigantic salt deposits which rarely crop out on land, such as in Sicily. The salt giants were ascribed to the desiccation, driven by the solar energy, of the entire basin. Nevertheless, the evaporite model hardly explains deep-sea salt deposits. This paper considers a different hypothesis suggesting that seawater reached NaCl saturation during serpentinization of ultramafic rocks. Solid salts and brine pockets were buried within the serpentinite bodies being later (e.g., in the Messinian) released, due to serpentinite breakdown, and discharged at seafloor as hydrothermal heavy brines. Therefore, sea-bottom layers of brine at gypsum and halite saturation were formed. The model is applicable to the Mediterranean area since geophysical data revealed relicts of an aged (hence serpentinized) oceanic lithosphere, of Tethyan affinity, both in its western “Atlantic” extension (Gulf of Cádiz) and in eastern basins, and xenoliths from Hyblean diatremes (Sicily) provided evidence of buried serpentinites in the central area. In addition, the buoyant behavior of muddled serpentinite and salts (and hydrocarbons) gave rise to many composite diapirs throughout the Mediterranean area. Thus, the Mediterranean “salt giant” consists of several independent geobodies of serpentinite and salts.

The northwest Mediterranean Basin includes a thick Messinian salt sequence composed of three evaporitic units. From these, the intermediate unit, which is dominantly composed of halite, acted as a gravitational detachment favoring the downslope failure of the overlying sediments in a thin-skinned deformation regime. As a result, the structure of the margin is characterized by an upper extensional domain with basinward-dipping listric normal faults and a lower contractional domain that accommodates upslope extension by folding, salt inflation, or diapir squeezing. Lower to middle Miocene volcanic seamounts (presalt reliefs) located at the upper extensional domain locally disrupted the evaporitic units and produced salt flow perturbations. They acted as passive buttresses during the gravitational failure modifying the structural zonation of the margin. Using an experimental approach (sandbox models), we analyze the role played by seamounts during the kinematic evolution of passive margins and how they alter salt flow and suprasalt deformation during gravitational gliding. The experiments found that the seamounts locally interrupt the structural zonation of the margin because they hindered downdip salt flow during early deformation. Seamounts initially compartmentalize the margin architecture, resulting in the development of two gravitational subsystems with two extensional/contractional pairs that are subsequently reconnected when the accumulation of salt analog upslope of the relief is enough to overthrust it. From this point onward, the cover is passively translated downslope as a regional system. The changes in the viscous layer flow velocity related to the dip differences between the flanks and edges of the seamount determine the kinematic evolution of this system. Our experiments also provide geometric constraints to consider during interpretation of these structures, which are commonly poorly imaged in seismic data.

The halogenesis of the Messinian Tuz Gölü Basin corresponds to the sulfate type and the magnesium sulfate subtype. Compared to the Messinian Sea brines, they have a slightly higher [Na+] concentration, which is 96.6–116.4 g/L, and a much lower [K+] concentration, ranging from 0.1 to 2.35 g/L. During salt sedimentation, the [Mg2+] concentration ranged from 6.1 to 14.0 g/L, and the [SO42−] concentration from 18.2 to 4.5 g/L. Physical–chemical reactions in the basin's near-surface and bottom waters during the suspension of halite deposition had a decisive influence on the significant reduction of [SO42−] sedimentation brines. During these periods, there was an intensive influx of Ca(HCO3)2 into the sedimentation basin and the formation of glauberite layers. The formation of the glauberite resulted from the slow dissolution of pre-deposited finely dispersed metastable minerals—gypsum, sodium syngenite, or mirabilite. In fluid inclusions in the halite, the sulfate minerals being allogenic crystals of calcium sulfate, are represented by gypsum, bassanite, and anhydrite. Additionally, as the other sulfate minerals, glauberite, anhydrite, and thenardite are found within halite crystals. Sharp fluctuations in daytime air temperatures characterized climatic indicators of the summer period in the Tuz Gölü region: 15.6–49.1 °C. In the spring or cool summer–autumn period, the daytime air temperature in the region ranged from 15.7–22.1 °C, and in late spring and early summer, it ranged from 20.6 °C to 35.0 °C. During some periods, the Tuz Gölü halite crystallized at 61.8–73.5 °C. The extreme high-temperature crystallization regime at the bottom of the salt-bearing basin was achieved due to the emergence of a vertical thermohaline structure. The "greenhouse effect" in the Tuz Gölü was established only briefly but was periodically renewed due to the influx of “fresh” waters.

ABSTRACT We used previously obtained marine geophysical and geotechnical data for the proposed Galsi pipeline route from Algeria to Sardinia to analyze the buried salt distribution, rates of fault displacements, and frequency and lateral extent of submarine slope failures. Crossing the convergent African/Nubian–European plate boundary, the southern section of the pipeline route traverses continental shelves and slopes of Algeria and Sardinia as well as the Algerian abyssal plain of the western Mediterranean. Deeply buried Messinian-aged salt is present throughout this area. Being less dense and more buoyant than the overburden sediment, the salt tends to flow upward to form diapiric structures that, in turn, result in the formation of faults and landslides in the overlying sediment. Measured offsets from seismic profiles of different resolutions were compared with predicted sediment age at depth of each offset, yielding an average rate of fault displacement of 1.5 cm/kiloyear (ky). The highest rates of displacement are along the Cagliari slope near Sardinia (2.5-2.7 cm/ky) and near the convergent plate boundary (2.3 cm/ky). Utilizing the same geophysical data, the frequency and lateral extent of submarine slope failures in the study area can also be linked to the distribution of salt and the influence of salt tectonics. Turbidity currents and hyperpycnal flows are present within the Algerian basin, whereas local debris flows, landslide runouts, and channelized debris flows are present along the Sardinian slope. The low sedimentation rates, determined in this study, suggest that the most recent slope failures related to salt tectonics occurred more than 12,000 years ago.

Abstract. The Calabrian Arc (CA) subduction complex is located at the toe of the Eurasian Plate in the Ionian Sea, where sediments resting on the lower plate have been scraped off and piled up in the accretionary wedge due to the African/Eurasian plate convergence and back arc extension. The CA has been struck repeatedly by destructive historical earthquakes, but knowledge of active faults and source parameters is relatively poor, particularly for seismogenic structures extending offshore. We analysed the fine structure of major tectonic features likely to have been sources of past earthquakes: (i) the NNW–SSE trending Malta STEP (Slab Transfer Edge Propagator) fault system, representing a lateral tear of the subduction system; (ii) the out-of-sequence thrusts (splay faults) at the rear of the salt-bearing Messinian accretionary wedge; and (iii) the Messina Straits fault system, part of the wide deformation zone separating the western and eastern lobes of the accretionary wedge. Our findings have implications for seismic hazard in southern Italy, as we compile an inventory of first order active faults that may have produced past seismic events such as the 1908, 1693 and 1169 earthquakes. These faults are likely to be source regions for future large magnitude events as they are long, deep and bound sectors of the margin characterized by different deformation and coupling rates on the plate interface.

Abstract Introduction.– The Oligo-Miocene extension phase of the Mediterranean basins rifting (30–25 Ma) [Jolivet and Faccenna, 2000] followed by the Ligurian basin oceanic crust formation (21–18 Ma) [Le Pichon et al., 1971 ; Réhault et al., 1984 ; Carminati et al., 1998 ; Gueguen et al., 1998] occurred during the western Alps compression phase. The deformations were characterised during the Miocene by the southwestward structuration of the Castellane Arc [Fallot and Faure-Muret, 1949 ; Laurent et al., 2000] and during the Mio-Pliocene by the southward structuration of the Nice Arc. This latter arc is bounded on its western side by a dextral strike-slip fault and on its southern side by a thrust inducing an uplift of this arc [Ritz, 1991 ; Guglielmi and Dubar, 1993 ; Clauzon et al., 1996 ; Guardia et al., 1996 ; Schroetter, 1998]. Fission tracks thermochronology data [Bigot-Cormier et al., 2000] suggest a general uplift at ~3.5 Ma of the Argentera massif. Stratigraphical [Irr, 1984 ; Hilgen, 1991 ; Hilgen and Langereis, 1988, 1993] and geomorphological studies [Clauzon et al., 1996 b ; Dubar and Guglielmi, 1997] show evidences for an uplift of the Ligurian coast increasing east of the Var river. The analysis of 70 seismic-reflection profiles allows us to better characterise and quantify the deformation from Antibes to Imperia (fig. 1). We then reconstruct vertical motions in space and time since the Messinian crisis in order to propose a deformation model of the margin related to crustal thickening. Morpho-structural and sedimentary characteristics of the margin. – The morphology of the margin results both from the Oligocene rifting and the Messinian crisis (5.8–5.3 Ma) characterised by a sea level fall of ~1500 m. At the surface, the margin, with a steep mean slope of 6–8o near Antibes [Réhault, 1981] to 12o near Imperia [Savoye and Piper, 1991], is cut by several canyons. At depth, there are two or three tilted blocks covered by Mesozoic sediments and in the Imperia area by the Helminthoïd Flyschs [Sosson et al., 1998]. In the basin, above the Miocene units, we observe some lower evaporites at the bottom, the Messinian salt in the middle and upper evaporites (E) marking the end of the low sea level 5.32 Ma ago [Ryan et al., 1973 ; Mauffret et al., 1973 ; Réhault 1981 ; Savoye and Piper, 1991]. The sedimentary series ends with 1500 m thick of Plio-Quaternary units [Gennesseaux and Le Calvez, 1960 ; Sosson et al., 1998]. At the top of the margin, we observe an erosion surface while toward the basin, two units are evidenced : the Messinian fan (CYL 30–05, fig. 2) unconformity, covered by a seismic facies similar to the one of the upper evaporites in the basin. The “M” surface, that relates the erosional surface of the margin and the upper evaporites of the basin, has a regular slope toward the basin (fig. 3). We will use this surface as a stratigraphic and structural reference for this work. Acquisition and methodology. – We analysed 12 profiles from the MALIGU cruise (1993–1994) [Chaumillon et al., 1994] and ~ 60 from several cruises (1992–2001) with the “Tethys” oceanographic ship to synthesize all stratigraphic and structural observations along the margin. In this paper, we only present 12 of them. We quantify the deformation at the margin/basin limit with a velocity gradient [Le Douaran et al., 1984 ; Rollet, 1999 ; Contrucci et al., 2001] on 50 profiles and we propose a deformation chronology using the “M” surface. Evidence for Pliocene deformation – Between Antibes and the east of Nice : there is no deformation of the “M” surface (fig. 3). – Between the east of Nice and the west of Menton : we observe a deformation at the top of the margin characterised by tilted seismic reflectors (fig. 4A). According to the micro-paleontology study, this deformation is dated at the Lower-Upper Pliocene limit. – From the west of Menton to San Remo : the deformation, observed in the middle of the margin, is characterised by a tilted Messinian fan and the formation of small basins (fig. 4A,B). We note that this deformation increases when the margin strikes ENE-WSW. – From San Remo to Imperia : the deformation increases from the middle to the base of the margin (fig. 4B). The apparent normal throw estimated at ~ 500 m near Antibes increases up to more than 2000 m near Imperia since ~ 5 Ma (fig. 5). This deformation induced (i) the formation of a piggy-back basin located near Imperia, (ii) a decrease of the “M” surface slope with at places a slope inversion compared with the Antibes area (fig. 4B). Space and time reconstitution of vertical motions. – In order to better visualise the geometry of the structure of the margin, we drew seismic profiles with no exaggeration. We interpret the observations seen above and the fact that normal faults on the rifted tilted blocks show a slope between 45–30o as the occurrence of a blind thrust (fig. 6). Motion along the thrusting plane induces the rotation of tilted blocks and is responsible for the margin uplift during the Lower-Upper Pliocene limit following a book-shelf mechanism [Mandl, 1987 ; Jackson and McKenzie, 1983]. At the bottom of the margin, we therefore interpret the apparent normal fault as a gravitary sliding (fig. 7) which enhances the front of the thrust vanishing in the Messinian salt unit. Discussion – Comparison between this model and others previously proposed : contrary to the model proposed by Chaumillon et al. [1994], we can explain the uplift of the margin and the presence of the “normal” faults at the limit margin/basin, only with one mechanism of crustal compression. This mechanism clearly comes from onshore and not from offshore as suggested by Béthoux et al. [1992]. The thrust, dipping toward the continent, can be observed on multichanel seismic reflection profiles [Rollet, 1999] (fig. 8). – The compression of the margin since the end of the lower-Pliocene : our results are chronologically and geometrically in agreement with reversal faults dipping toward the continent, observed along Cap Mele (fig. 1) at the bottom of the Pliocene units [Réhault, 1981]. Both, the important thickness of the Plio-Quaternary sediments near Imperia, far away from the Var river, and the many salt diapirs in the NE area, are consistent with a thrust motion. – The area Argentera massif-Ligurian margin : according to fission track data [Bigot-Cormier et al., 2000] a major uplift was detected at ~3.5 Ma. At the same time, the Ligurian margin recorded a compressive phase with a structural geometry consistent with the deformation onshore (fig. 9). The deformation on the thrust front is the most important at the axis of the main structures of the Argentera. This thrust front is located at the base of the margin near Imperia and propagated toward the top close to the western edge of the Nice arc (fig. 10). Our observations suggest that the deformations propagate offshore in relation with the advance of the Alpine front toward the south. Conclusion. – The analysis of 70 seismic reflection profiles based on stratigraphic and structural studies allows us to quantify and date the deformation of the Ligurian margin increasing eastward. This deformation dated at the Lower-Upper Pliocene limit is due to the propagation of a blind thrust front consistent with the basement tectonic deformation of this period reactivating the Oligocene rifting structures.

The advantages of recording a well-sampled, wider range of azimuths on seismic surveys are being seen in different geological settings worldwide. The success of wide-azimuth surveys has been well documented for sub-salt illumination in the deep water plays of the Gulf of Mexico. Multi-azimuth surveys have similarly shown improved S/N beneath the Messinian unconformity offshore Egypt. More recently, the benefits of improved sampling (and hence attenuation) of noise by dense, wide-azimuth surveys have been demonstrated onshore Oman. Although the successful marine results have highlighted the benefits of true 3D or wide-azimuth surveys, land surveys have often been recorded with a wide range of azimuths for many years. The step-change occurring onshore is the dramatic increase in the trace density on wide-azimuth surveys. We are learning that one of the reasons that conventional land seismic data have often been viewed as noisy is that coherent energy, particularly near surface events, is grossly under-sampled. Modern land recording techniques such as overlapping vibrator sweeps, single vibrator (point source) recording, multiple vibrator fleets and high channel systems allow us to record data much more efficiently. In turn, these enabling technologies allow us to obtain much improved seismic data quality via greatly increased sampling density. Moreover, recording geometries on this new generation of land supercrews provide trace densities that are many times higher than on marine surveys. The next step for marine wide-azimuth surveys may require a similar step-change in recording density in order to address difficult geologies that cannot be imaged with current recording techniques.

ABSTRACT Since the onshore discovery of oil in the Eastern Desert in 1886, the petroleum industry in Egypt has accumulated reserves of more than 15.5 billion barrels of oil equivalent. An understanding of the tectono-stratigraphic history of each major basin, combined with drilling history and field-size distributions, justifies the realization of the complete replacement of these reserves in the coming decades. Most of the increase in reserves will be the result of offshore exploration. In addition to the 25 trillion cubic feet already discovered, the offshore Mediterranean may hold 64 to 84 trillion cubic feet and the onshore Western Desert may contribute 15 to 30 trillion cubic feet in new gas resources. Many of the new fields are expected to be in the giant-field class that contains greater than 100 million barrels of oil equivalent. Challenges include sub-salt imaging, market constraints for predominantly gas resources and economic constraints imposed by the high cost of development of the current deep-water gas discoveries that are probably unique worldwide. The offshore Gulf of Suez may yield an additional 1.5 to 3.3 billion barrels of oil equivalent, but it continues to be technologically constrained by poor-quality seismic data. Advances in multiple suppression and development of new ‘off-structure’ play concepts with higher quality seismic data should result in continual new pool discoveries. Offshore frontier exploration includes the Red Sea rift (currently under reassessment with area-wide 3-D surveys) and the Gulf of Aqaba. Deep-water and sub-salt imaging remain significant challenges to be overcome. Despite a relatively complex history, the Phanerozoic geological framework of Egypt is extremely prospective for oil and gas. Eight major tectono-stratigraphic events are: (1) Paleozoic craton; (2) Jurassic rifting; (3) Cretaceous passive margin; (4) Cretaceous Syrian Arc deformation and foreland transgressions; (5) Oligocene-Miocene Gulf of Suez rifting; (6) Miocene Red Sea opening; (7) the Messinian salinity crisis; and (8) Pliocene-Pleistocene delta progradation. Each of these events has created multiple reservoir and seal combinations. Source rocks occur from the Paleozoic through to the Pliocene and petroleum is produced from reservoirs that range in age from Precambrian to Pleistocene. The offshore Mediterranean, Gulf of Suez and Red Sea/Gulf of Aqaba contain significant exploration potential and will provide substantial reserve replacements in the coming decades.

Messina (Melilotus siculus) is a new annual pasture legume with better combined waterlogging and salt tolerance than other annual legumes. Messina cv. Neptune and a new salt-tolerant rhizobial symbiont (Sinorhizobium medicae SRDI-554) were made available to Australian growers in 2017. Messina is related to the annual medics (Medicago spp.) that are nodulated by the same genus of rhizobia and regarded as sensitive to soil acidity. Because some saltland soils are acidic, it is important to understand the sensitivity of messina to soil acidity in order to avoid failures during early adoption. Acidity tolerance of the messina–Sinorhizobium symbiosis was investigated in a hydroponic experiment (inoculation with SRDI-554, or the salt-intolerant strain WSM-1115 recommended for medics), and in three acidic soils (pHCa 4.3–5.5) (inoculation with SRDI-554 ± lime pelleting of seed), in the greenhouse. In the hydroponic experiment, the percentage of messina plants (with SRDI-554) that formed nodules declined at pH levels between 5.7 (43%) and 5.5 (4%). Strain SRDI-554 was slightly more sensitive to acidity than strain WSM-1115. In the acidic soils, more plants formed nodules than in the hydroponic experiment at similar pH levels; however, without lime pelleting, nodule number was inadequate at soil pHCa <5.5. Addition of lime to seed was beneficial to messina nodulation. Nodule number per plant increased from 4.0 to 9.6 with the addition of lime. The messina–Sinorhizobium symbiosis was confirmed as sensitive to low pH. At pHCa 5.5, which is the level recommended as the lower limit for growing messina, nodule number was constrained in both hydroponics and soil. The risk of suboptimal nodulation would be reduced if the recommended lower soil pH limit for growing messina is increased to pHCa 5.8, in line with most annual medics. Efforts to improve the acidity tolerance of the messina symbiosis would be best focused on the rhizobial symbiont, rather than the plant.

Messina (Melilotus siculus) cv. Neptune, an annual pasture legume native to the Mediterranean Basin, has recently been released for saltland pastures in southern Australia following demonstration of biomass production and persistence superior to other commercial pasture legumes in saline environments prone to winter waterlogging. Self-regenerating annual pasture legumes also require seed adaptations for both tolerating and avoiding salinity at germination in these environments. This study examined diversity within Neptune and 20 other messina accessions for salt tolerance at germination, recovery of germinability from temporary salt stress, and timing and extent of hardseed softening, compared with balansa clover (Trifolium michelianum) cv. Frontier, burr medic (Medicago polymorpha) cv. Scimitar and white melilot (Melilotus albus) cv. Jota. Germination rates after 14 days at 300 mM NaCl relative to 0 mM NaCl were ≥99% for Neptune and 18 other messina accessions, 66% for Scimitar, 21% for Jota and 11% for Frontier. No genotype germinated at 600 mM NaCl; however, when transferred to 0 mM NaCl after 14 days at 600 mM, all genotypes except Scimitar and Jota recovered partial germination, ranging from 13% to 93% of controls (0 mM NaCl for 28 days). The softening rate of hard (impermeable) seeds in the field varied among genotypes, with deferral of hardseed softening until late autumn–early winter, when rainfall is more likely, indicating greater persistence. The months in which the hardseed level first became significantly lower than the initial level (in freshly harvested seeds) after placement on the soil surface in December were: March for Frontier; April for Scimitar, Jota and Neptune; and March–July for all messina accessions. This study confirmed that messina has high salt tolerance and several avoidance mechanisms at germination that contribute to its adaptation to saline soils in southern Australia. Several messina accessions were superior to Neptune for individual traits which could be exploited for plant breeding. These results also have implications for saltland pastures in other regions of the world with Mediterranean-type climates.

Melilotus siculus (common name messina) has shown potential as a productive annual forage legume in saline and waterlogged areas in temperate Australia. The salt and waterlogging tolerances of 30 M. siculus accessions were evaluated at germination and as established plants. Many accessions germinated at 240 mm NaCl, but germination was <15% at 320 mm NaCl. In vegetative plants, accessions differed in the degree of growth reduction at 300 mm NaCl, with some producing >90%, but others <20%, of non-saline controls. A negative relationship (r = 0.47, P < 0.001) was found between dry weight under non-saline conditions and relative salt tolerance (i.e. salt-treated as % of controls). Concentrations of Cl– and Na+ in shoots of all accessions increased significantly with increasing NaCl in the medium, although these differed among accessions. No relationships were found between shoot Cl–, Na+, or K+ concentrations and relative salt tolerance at 300 mm NaCl, whereas net K+ : Na+ selectivity to shoots was positively correlated with relative salt tolerance (r = 0.30, P = 0.1). All accessions showed good tolerance to stagnant, O2-deficient conditions in the root medium, and shoot growth was not reduced by >20% in any accession. Root porosity (% gas volume/root volume) in both the main and lateral roots increased in all accessions when in stagnant medium, but accessions differed in root porosity. Lateral root porosity was not, however, correlated with either shoot dry weight or root dry weight in stagnant conditions. No single accession of M. siculus had the highest tolerance to saline conditions both at germination and the vegetative stage, but some accessions (e.g. SA 40002 and SA 40004) performed consistently well under saline and waterlogged conditions. Further research and selection is warranted on these accessions with the aim to release a cultivar.

Agriculture is increasingly forced to utilize marginal waters to meet its increasing demands, which in turn increases the risks of soil salinization and yield reduction in the arid and semi-arid areas of the Mediterranean basin. Given that the bean is an extremely salt sensitive species, the purpose of the present work was to study the effect of 0 and 75 mM sodium chloride (NaCl) on leaf characteristics, growth, pod yield and ion accumulation of three green bean (Phaseolus vulgaris L.) cultivars (‘Corallo Nano’, ‘Romano Bush Plaja’ and ‘Starazagorski’), widely used in Greece. Plants were grown in a greenhouse of Technological Educational Institute of Peloponnese in Messinia, Southern Greece, from April to June 2014, in hydroponics. The experimental design was the factorial completely randomized one with five replications; each replication consisted of the three plants grown on the same rockwool slab. The results of the majority of growth and yield parameters determined showed the superiority of ‘Corallo’ over ‘Romano’ whereas ‘Starazagorski’ tolerance was found to be intermediate. ‘Corallo’ tolerated NaCl salinity better due to its capacity for Na retention in the roots and maintaining appropriate K/Na and Ca/Na ratios, limiting the accumulation of toxic ions into actively growing shoots. The salt sensitivity of ‘Romano’ was related to its higher concentration of Na in the leaves and lower in the roots, to the greater decrease of the leaf number and leaf water content, as well as to the specific leaf area increase compared to the other two cultivars under saline conditions.

AbstractIn ancient times, the name “Peloro” was used to indicate an anthropic area that gradually developed around the first known human settlement on the Sicilian shore near the Straits of Messina. Since the 5th century BC, historians have documented that numerous naval armadas landed for long periods at Peloro. However, the present-day morphology of the Peloro Cape Peninsula does not have any protected inlet that would offer a location to repair hundreds of ships, as has been documented by historical sources. To address this discrepancy, geomorphologic data were collected and analyzed to verify whether historical documents were consistent with the palaeotopography of the area. This approach is based on the analysis of the morphotectonic evolution of the coastal lowland that resulted from regional uplift over the Quaternary and Holocene. The results indicate that the harbour was located in the basin of the Pantano Piccolo salt marsh, and was large and deep enough to have sheltered up to 320 ships.

Messina [Melilotus siculus (Turra) Vitman ex. B. D Jacks] is a salt- and waterlogging-tolerant annual legume that could be highly productive on saline land. Arbuscular mycorrhizal (AM) fungi form a symbiotic relationship with the majority of terrestrial plant species, and improved productivity of plants inoculated with AM fungi under saline conditions has been attributed to the increased uptake of nutrients such as phosphorus (P). However, the mycorrhizal status of M. siculus under saline or non-saline conditions is unknown, as is the role of AM in improved nutrition and nodulation. In this study, the role of AM fungi in growth improvement and nodulation of M. siculus was examined in saline and non-saline soil. The M. siculus plants were inoculated with either a single AM species or mixed AM species, or remained uninoculated, and were grown at three levels of sodium chloride (NaCl) (0, 80, and 250 mm NaCl). AM-inoculated plants had significantly greater nodulation than plants that did not receive AM inoculum, regardless of salinity level. Plants inoculated with mixed AM species at 250 mm NaCl showed improved survival (90%) compared with the plants inoculated with single AM species or uninoculated control plants (30%). Within each salinity level, plants inoculated with mixed AM species had significantly greater dry weight than all other treatments. In addition, plants inoculated with mixed AM species had increased total uptake of P. It is likely that the increased growth observed in AM-inoculated M. siculus plants is due to improved P nutrition, showing the potential of AM fungi to enhance the growth of M. siculus on saline land.

Sir, In one of his precious masterpieces, Portuguese novelist José Saramago narrates in detail the lives of the rice weeders who used to work in this land and, after a day of work, soak their bare feet in a bath with hot water, salt, mallow, and chamomile in order to restore their ankles, swollen and inflated for the alga native to these particular paddy fields, Laminaria ochroleuca (Bachelot de la Pylaie), extremely rich in fucose and alginates, provoking an accelerated and paroxistic synthesis of elastin, fibronectin, and collagen. This brown alga may be retrieved from the waters of France, Spain, Scotland, and the Shetland Islands, yet even in the Azores Islands and Morocco (Alboran Sea) [1–4]. The authors of this paper selected a special Laminaria from the Strait of Messina (Nereocystis luetkeana), a heterokont that is able to grow half a meter per day reaching the surprising and amazing height of 260 ft.). The legend has it that shell collectors, chiefly young girls, day after day, saw their legs together to create the tail of a siren, a cartilaginous appendage rich in collagen and elastin becoming scaly and squamous owing to the seawater. The authors created a dermocosmetic emulsion with high concentrations of acetolyte from Laminaria ochroleuca (12%) and other nourishing active ingredients (obviously, the chief components were petrolatum and lanolin, as per the pharmaceutical art of preparing the cold cream of Galenus). Hence, this golden alga is able to support the skin by providing antioxidants to fight free radicals, supporting the health of collagen and elastin, which helps the skin retain elasticity and radiance, reducing fine lines and wrinkles and helping to moisturize the skin while boosting its barrier. Some researchers [5] claimed that this alga could be useful to build a skin equivalent, as fucoidan significantly stimulates the proliferation of CCD-25Sk human fibroblasts. Also, western blot analysis demonstrates that fucoidan markedly increases the expression of cyclin D1 and decreases the expression of p27. Fucoidan was practically used to reconstruct SE. Immunohistochemical staining reveals that the addition of fucoidan to dermal equivalents increases the expression of proliferating cell nuclear antigen (PCNA) and p63. In addition, the expression of a6-integrin is significantly increased by fucoidan, whereas the expression of b1-integrin, type 1 collagen, elastin, and fibronectin does not markedly change. In the light of the above, the authors may assert that fucoidan shows positive effects on epidermal reconstruction and is, therefore, beneficial in the reconstruction of all types of skin damage. The authors recruited a panel of eight people: 2 veterans from Iraq and Afghanistan (a-b) presenting old war wounds with no chance to cure these after years of treatments and a myriad of surgical operations; 2 elders (one male and one female, 87 and 89 yrs. old, respectively, c-d) presenting severe bedsores; 2 older ladies (e-f) who, in the past, underwent unsuccessful aesthetical operations, presenting puckers, seams, furrows and deep wrinkles; 2 girls (two ex-prostitutes, one black and one white, g-h) who were scarred with a razor by their enemies.

Abstract Variations in salinity and flow rate in the aerial, naturally salty spring of Almyros of Heraklion on Crete were monitored during two hydrological cycles. We describe the functioning of the coastal karstic system of the Almyros and show the influence of the duality of the flow in the karst (conduits and fractured matrix) on the quality of the water resource in the coastal area. A mechanism of saltwater intrusion into this highly heterogeneous system is proposed and validated with a hydraulic mathematical model, which describes the observations remarkably well. Introduction. – Fresh groundwater is a precious resource in many coastal regions, for drinking water supply, either to complement surface water resources, or when such resources are polluted or unavailable in the dry season. But coastal groundwater is fragile, and its exploitation must be made with care to prevent saltwater intrusion as a result of withdrawal, for any aquifer type, porous, fractured or karstic. In karstic zones, the problem is very complex because of the heterogeneous nature of the karst, which makes it difficult to use the concept of representative elementary volume developed for porous or densely fractured systems. The karstic conduits focus the major part of the flow in preferential paths, where the water velocity is high. In coastal systems, these conduits have also an effect on the distribution of the saline intrusion. As was shown e.g. by Moore et al. [1992] and Howard and Mullings [1996], both freshwater and salt-water flow along the fractures and conduits to reach the mixing zone, or the zone where these fluids are superposed in a dynamic equilibrium because of their differences in density ; but the dynamics of such a saltwater intrusion are generally unknown and not represented in models. Such coastal karstic systems are intensely studied at this moment in the Mediterranean region [Gilli, 1999], both as above sea-level or underwater springs, for potential use in areas where this resource would be of great value for economic development. This article discusses the freshwater-saltwater exchange mechanisms in the karstic aquifer of the Almyros of Heraklion aquifer (Crete) and explains the salinity variations observed in the spring. First, the general hydrogeology of the study site is described, then the functioning of the spring : a main conduit drains the freshwater over several kilometres and passes at depth through a zone where seawater is naturally present. The matrix-conduit exchanges are the result of pressure differences between the two media. These processes are represented in a mathematical model that confirms their relevance. General hydrogeology of the studied site. – The karstic coastal system of the Almyros of Heraklion (Crete) covers 300 km2 in the Ida massif whose borders are a main detachment fault, and the Sea of Crete in the north, the Psiloritis massif (highest summit at 2,456 m) in the south and west, and the collapsed basin of Heraklion filled in by mainly neo-geneous marl sediments in the east. The watershed basin consists of the two lower units of characteristic overthrust formations of Crete (fig. 1) : the Cretaceous Plattenkalk and the Cretaceous Tripolitza limestones. The two limestone formations are locally separated by interbedded flysch or phyllade units that form an impervious layer [Bonneau et al., 1977 ; Fassoulas, 1999] and may lead to different flow behaviour within the two karstic formations. Neo-tectonic activity has dissected these formations with large faults and fractures. The present-day climate in Crete is of Mediterranean mountain type, with heavy rain storms and snow on the summits in winter. Rainfall is unevenly distributed over the year, with 80 % of the annual total between October and March and a year-to-year average of 1,370 mm. The flow rate of the spring is high during the whole hydrologic cycle, with a minimum in summer on the order of 3 m3.s−1 and peak flow in winter reaching up to 40 m3.s −1. The water is brackish during low flow, up to a chloride content of 6 g.l−1, i.e. 23 % of seawater, but it is fresh during floods, when the flow rate exceeds 15 m3.s−1. During the 1999–2000 and 2000–2001 hydrologic cycles, the water was fresh during 14 and 31 days, respectively. The water temperature is high and varies very little during the year (see table I). In the areas of Kéri and Tilissos (fig. 1), immediately south of the spring, the city of Heraklion extracts water from the karstic system through a series of 15 wells with depth reaching 50 to 100 m below sea level. Initially, when the wells were drilled, the water was fresh, but nowadays the salinity rises progressively, but unequally from well to well (fig. 2). The relatively constant temperatures and salinities of the wells, during the hydrological cycle, contrast with the large salinity variations at the spring (fig. 2 and table I). They show that the karstic system is complex and comprises different compartments, where each aquifer unit reacts to its individual pressures (pumping, rainfall) according to its own hydrodynamic characteristics [Arfib et al., 2000]. The Almyros spring seems disconnected from the surrounding aquifer and behaves differently from that which feeds the wells (upper Tripolitza limestone). It is recharged by fresh water from the mountains, which descends to depths where it probably acquires its salinity. The spring would thus be the largest resource of the area, if it was possible to prevent its pollution by seawater. A general functioning sketch is proposed (fig. 3), which includes the different geological units of interest. Identification of the functioning of the Almyros spring through monitoring of physical and chemical parameters. – The functioning of the aquifer system of the Almyros spring was analysed by monitoring, over two hydrological cycles, the level of the spring, the discharge, the electric conductivity and the temperature recorded at a 30 min time interval. In the centre of the watershed basin, a meteorological station at an altitude of 800 m measures and records at a 30 min time interval the air temperature, rainfall, relative humidity, wind velocity and direction ; moreover, an automatic rain gauge is installed in the northern part of the basin at an altitude of 500 m. The winter floods follow the rhythm of the rainfall with strong flow-rate variations. In contrast, the summer and autumn are long periods of drought (fig. 7). The flow rate increases a few hours after each rainfall event ; the water salinity decreases in inverse proportion to the flow rate a few hours to a few days later. Observations showed that the water volume discharged at the Almyros spring between the beginning of the flow rate increase and the beginning of the salinity decrease is quite constant, around 770,000 m3 (fig. 4) for any value of the flow rate, of the salinity and also of the initial or final rainfall rates. To determine this constant volume was of the upmost importance when analyzing the functioning of the Almyros spring. The lag illustrates the differences between the pressure wave that moves almost instantaneously through the karst conduit and causes an immediate flow rate increase after rainfall and the movement of the water molecules (transfer of matter) that arrives with a time lag proportionate to the length of the travel distance. The variation of the salinity with the flow rate acts as a tracer and gives a direct indication of the distance between the outlet and the seawater entrance point into the conduit. In the case of the Almyros, the constant volume of expelled water indicates that sea-water intrusion occurs in a portion of the conduit situated several kilometres away from the spring (table II), probably inland, with no subsequent sideways exchange in the part of the gallery leading up to the spring. As the lag between the flow rate and the salinity recorded at the spring is constant, one can correct the salinity value by taking, at each time step, with a given flow rate, the salinity value measured after the expulsion of 770,000 m3 at the spring, which transforms the output of the system so as to put the pressure waves and the matter transfer in phase [Arfib, 2001]. After this correction, the saline flux at the spring, equal to the flow rate multiplied by the corrected salinity, indicates the amount of sea-water in the total flow. This flux varies in inverse proportion to the total flow rate in the high-flow period and the beginning of the low-flow period, thereby demonstrating that the salinity decrease in the spring is not simply a dilution effect (fig. 5). The relationship that exists between flow rate and corrected salinity provides the additional information needed to build the conceptual model of the functioning of the part of the Almyros of Heraklion aquifer that communicates with the spring. Freshwater from the Psiloritis mountains feeds the Almyros spring. It circulates through a main karst conduit that descends deep into the aquifer and crosses a zone naturally invaded by seawater several kilometers from the spring. The seawater enters the conduit and the resulting brackish water is then transported to the spring without any further change in salinity. The conduit-matrix and matrix-conduit exchanges are governed by the head differences in the two media. Mathematical modelling of seawater intrusion into a karst conduit Method. – The functioning pattern exposed above shows that such a system cannot be treated as an equivalent porous medium and highlights the influence of heterogeneous structures such as karst conduits on the quantity and quality of water resources. Our model is called SWIKAC (Salt Water Intrusion in Karst Conduits), written in Matlab®. It is a 1 D mixing-cell type model with an explicit finite-difference calculation. This numerical method has already been used to simulate flow and transport in porous [e.g. Bajracharya and Barry, 1994 ; Van Ommen, 1985] and karst media [e.g. Bauer et al., 1999 ; Liedl and Sauter, 1998 ; Tezcan, 1998]. It reduces the aquifer to a single circular conduit surrounded by a matrix equivalent to a homogeneous porous medium where pressure and salinity conditions are in relation with sea-water. The conduit is fed by freshwater at its upstream end and seawater penetrates through its walls over the length L (fig. 6) at a rate given by an equation based on the Dupuit-Forchheimer solution and the method of images. The model calculates, in each mesh of the conduit and at each time step, the head in conditions of turbulent flow with the Darcy-Weisbach equation. The head loss coefficient λ is calculated by Louis’ formula for turbulent flow of non-parallel liquid streams [Jeannin, 2001 ; Jeannin and Marechal, 1995]. The fitting of the model is intended to simulate the chloride concentration at the spring for a given matrix permeability (K), depth (P) and conduit diameter (D) while varying its length (L) and its relative roughness (kr). The spring flow rates are the measured ones ; at present, the model is not meant to predict the flow rate of the spring but only to explain its salinity variations. Results and discussion. – The simulations of chloride concentrations were made in the period from September 1999 to May 2001. The depth of the horizontal conduit where matrix-conduit exchanges occur was tested down to 800 m below sea level. The diameter of the conduit varied between 10 and 20 m, which is larger than that observed by divers close to the spring but plausible for the seawater intrusion zone. The average hydraulic conductivity of the equivalent continuous matrix was estimated at 10−4 m/s. A higher value (10−3 m/s) was tested and found to be possible since the fractured limestone in the intrusion zone may locally be more permeable but a smaller value (10−5 m/s) produces an unrealistic length (L) of the saline intrusion zone (over 15 km). For each combination of hydraulic conductivity, diameter and depth there is one set of L (length) and kr (relative roughness) calibration parameters. All combinations for a depth of 400 m or more produce practically equivalent results, close to the measured values. When the depth of the conduit is less than 400 m, the simulated salinity is always too high. Figure 7 shows results for a depth of 500 m, a diameter of 15 m and a hydraulic conductivity of 10−4 m/s. The length of the saltwater intrusion zone is then 1,320 m, 4,350 m away from the spring and the relative roughness coefficient is 1.1. All the simulations (table II) need a very high relative roughness coefficient which may be interpreted as an equivalent coefficient that takes into account the heavy head losses by friction and the variations of the conduit dimensions which, locally, cause great head losses. The model simulates very well the general shape of the salinity curve and the succession of high water levels in the Almyros spring but two periods are poorly described due to the simplicity of the model. They are (1) the period following strong freshwater floods, where the model does not account for the expulsion of freshwater outside the conduit and the return of this freshwater which dilutes the tail of the flood and (2) the end of the low-water period when the measured flux of chlorides falls unexpectedly (fig. 5), which might be explained by density stratification phenomena of freshwater-saltwater in the conduit (as observed in the karst gallery of Port-Miou near Cassis, France [Potié and Ricour, 1974]), an aspect that the model does not take into account. Conclusions. – The good results produced by the model confirm the proposed functioning pattern of the spring. The regulation of the saline intrusion occurs over a limited area at depth, through the action of the pressure differences between the fractured limestone continuous matrix with its natural saline intrusion and a karst conduit carrying water that is first fresh then brackish up to the Almyros spring. The depth of the horizontal conduit is more than 400 m. An attempt at raising the water level at the spring, with a concrete dam, made in 1987, which was also modelled, indicates that the real depth is around 500 m but the poor quality of these data requires new tests to be made before any firm conclusions on the exact depth of the conduit can be drawn. The Almyros spring is a particularly favorable for observing the exchanges in the conduit network for which it is the direct outlet but it is not representative of the surrounding area. To sustainably manage the water in this region, it is essential to change the present working of the wells in order to limit the irreversible saline intrusion into the terrain of the upper aquifers. It seems possible to exploit the spring directly if the level of its outlet is raised. This would reduce the salinity in the spring to almost zero in all seasons by increasing the head in the conduit. In its present state of calibration, the model calculates a height on the order of 15 m for obtaining freshwater at the spring throughout the year, but real tests with the existing dam are needed to quantify any flow-rate losses or functional changes when there is continual overpressure in the system. The cause of the development of this karstic conduit at such a great depth could be the lowering of the sea level during the Messinian [Clauzon et al., 1996], or recent tectonic movements.

Objetivo: Describir los conocimientos sobre transmisión, sintomatología, acciones de prevención y control frente a dengue en la región Piura, Perú. Material y métodos: Análisis secundario de la sección 700 (salud) de la Encuesta Nacional de Programas Estratégicos 2014, realizada por el Instituto Nacional de Estadística e Informática a 113 073 habitantes de ≥14 años a nivel nacional (5 131 en Piura). Se analizaron las preguntas 701 al 704 sobre conocimientos de dengue. Las respuestas fueron analizadas según características demográficas y provincia de residencia. Además, se comparó los resultados de toda la región frente al promedio nacional. Resultados: En Piura, el 78,4% refirió que la transmisión de dengue es por la picadura de un mosquito, (solo 54,5% a nivel nacional). Hubo diferencias entre zonas urbana (84%) y rural (58,2%), y entre provincias. Los síntomas más recordados fueron fiebre (79,7%), cefalea (56,4%), dolor de huesos/articulaciones (30,3%) y escalofríos (28,7%). 96,9% acudiría a un establecimiento de salud si presentara síntomas (97,8% a nivel nacional). Conocimiento sobre control de mosquito fue menor del 50% de medidas adecuadas. Conclusiones: El conocimiento sobre algunos aspectos del dengue es aún limitado en la región Piura, siendo ésta la más endémica a nivel nacional. Se debe enfatizar en educación sanitaria a nivel poblacional para frenar el avance alarmante de este problema. 1. Guzman MG, Harris E. Dengue. Lancet. 2015;385(9966):453-65.2. Rey JR, Philip Lounibos P. Ecología de Aedes aegypti y Aedes albopictus en América y transmisión enfermedades. Biomédica. 2015;35:177-85. 3. Bouyer J, Chandre F, Gilles J, Baldet T. Alternative vector control methods to manage the Zika virus outbreak: more haste, less speed. Lancet Glob Health. 2016;4(6):e364. 4. Hermann LL, Gupta SB, Manoff SB, Kalayanarooj S, Gibbons RV, Coller BA. Advances in the understanding, management, and prevention of dengue. J Clin Virol. 2015;64:153-9. 5. Bhatt S, Gething PW, Brady OJ, Messina JP, Farlow AW, Moyes CL, et al. The global distribution and burden of dengue. Nature. 2013;496:504–507. 6. Quintero J, Brochero H, Manrique-Saide P, Barrera-Pérez M, Basso C, Romero S, Petzold M, et al. Ecological, biological and social dimensions of dengue vector breeding in five urban settings of Latin America: a multi-country study. BMC Infect Dis. 2014;21:14:38. 7. Kroeger A, Lenhart A, Ochoa M, Villegas E, Levy M, Alexander N, et al. Effective control of dengue vectors with curtains and water container covers treated with insecticide in Mexico and Venezuela: cluster randomised trials. BMJ. 2006;332:1247–1252. 8. Paz-Soldán VA, Morrison AC, Cordova Lopez JJ, Lenhart A, Scott TW, Elder JP, et al. Dengue Knowledge and Preventive Practices in Iquitos, Peru. Am J Trop Med Hyg. 2015;93(6):1330-7. 9. Cáceres-Manrique FM, Vesga-Gómez C, Perea-Florez X, Ruitort M, Talbot Y. Conocimientos, Actitudes y Prácticas sobre Dengue en Dos Barrios de Bucaramanga, Colombia. Rev. salud pública. 2009;11(1):27-38. 10. Santos SL, Parra-Henao G, Silva MB, Augusto LG. Dengue in Brazil and Colombia: a study of knowledge, attitudes, and practices. Rev Soc Bras Med Trop. 2014;47(6):783-7. 11. Egedus VL, Ortega JM, Obando AA. Knowledge, perceptions, and practices with respect to the prevention of dengue in a mid-Pacific coastal village of Costa Rica. Rev Biol Trop. 2014;62(3):859-67. 12. Wong LP, AbuBakar S. Health beliefs and practices related to dengue fever: a focus group study. PLoS Negl Trop Dis. 2013;7(7):e2310. 13. Van Benthem BH, Khantikul N, Panart K, Kessels PJ, Somboon P, Oskam L. Knowledge and use of prevention measures related to dengue in northern Thailand. Trop Med Int Health. 2002;7(11):993- 1000. 14. Sala de Situación de Salud – Semana Epidemiológica N° 11 2017 [Internet]. Lima: Centro Nacional de Epidemiología, Prevención y Control de Enfermedades - Ministerio de Salud; 2017 [citado el 10 de octubre de 2017]. Disponible en: http://www.dge.gob.pe/portal/docs/vigilancia/sala/2017/salaSE11.pdf. 15. Ferreira MC. Geographical distribution of the association between El Niño South Oscillation and dengue fever in the Americas: a continental analysis using geographical information system-based techniques. Geospat Health. 2014;9(1):141-51. 16. Encuesta Nacional de Programas Estratégicos 2011-2014 [Internet]. Lima: Instituto Nacional de estadística e Informática; 2015 [citado el 10 de octubre de 2016]. Disponible en: https://www.inei.gob. pe/media/MenuRecursivo/publicaciones_digitales/Est/Lib1291/libro.pdf 17. Palma-Pinedo H, Cabrera R, Yagui-Moscoso M. Factors behind people's reluctance towards dengue vector control actions in three districts in northern Peru. Rev Peru Med Exp Salud Publica. 2016;33(1):13-20. 18. OMS habla de una epidemia por dengue en región Piura [Internet]. Lima: CMP noticias; 2016 [citado el 10 de octubre de 2016]. Disponible en: https://cmp.org.pe/oms-habla-de-una-epidemiapor- dengue-en-la-region-piura/ 19. Gyawali N, Bradbury RS, Taylor-Robinson AW. Knowledge, attitude and recommendations for practice regarding dengue among the resident population of Queensland, Australia. Asian Pac J Trop Biomed. 2016;6(4):360–366. 20. Malhotra G, Yadav A, Dudeja P. Knowledge, awareness and practices regarding dengue among rural and slum communities in North Indian city, India. Int J Med Science and Public Health. 2014;3(3):295-299. 21. Hairi F, Ong CH, Suhaimi A, Tsung TW, Sundaraj C, Soe MM, et al. A knowledge, attitude and practices (KAP) study on dengue among selected rural communities in the Kuala Kangsar district. Asia Pac J Public Health. 2003;15(1):37-43. 22. Dhimal M, Aryal KK, Dhimal ML, Gautam I, Singh SP, Bhusal CL, et al. Knowledge, attitude and practice regarding dengue fever among the healthy population of highland and lowland communities in central Nepal. PLoS One. 2014;9(7):e102028.