The Messinian salinity crisis in Cyprus: a further step towards a new stratigraphic framework for Eastern Mediterranean

A revised stratigraphic framework for the Messinian succession of Cyprus is proposed demonstrating that the three‐stage model for the Messinian salinity crisis recently established for the Western Mediterranean also applies to the Eastern Mediterranean, at least for its marginal basins. This analysis is based on a multidisciplinary study of the Messinian evaporites and associated deposits exposed in the Polemi, Pissouri, Maroni/Psematismenos and Mesaoria basins. Here, we document for the first time that the base of the unit usually referred to the ‘Lower Evaporites’ in Cyprus does not actually correspond to the onset of the Messinian salinity crisis. The basal surface of this unit rather corresponds to a regional‐scale unconformity, locally associated with an angular discordance, and is related to the erosion and resedimentation of primary evaporites deposited during the first stage of the Messinian salinity crisis. This evidence suggests that the ‘Lower Evaporites’ of the southern basins of Cyprus actually belong to the second stage of the Messinian salinity crisis; they can be thus ascribed to the Resedimented Lower Gypsum unit that was deposited between 5.6 and 5.5 Ma and is possibly coeval to the halite deposited in the northern Mesaoria basin. Primary, in situ evaporites of the first stage of the Messinian salinity crisis were not preserved in Cyprus basins. Conversely, shallow‐water primary evaporites deposited during the third stage of the Messinian salinity crisis are well preserved; these deposits can be regarded as the equivalent of the Upper Gypsum of Sicily. Our study documents that the Messinian stratigraphy shows many similarities between the Western and Eastern Mediterranean marginal basins, implying a common and likely coeval development of the Messinian salinity crisis. This could be reflected also in intermediate and deep‐water basins; we infer that the Lower Evaporites seismic unit in the deep Eastern Mediterranean basins could well be mainly composed of clastic evaporites and that its base could correspond to the Messinian erosional surface.     

Latent sprawl,divided Mediterranean landscapes: urban growth,swimming pools,and the socio-spatial structure of Athens,Greece

Although Mediterranean cities have inherent differences on a local scale, together they offer a kaleidoscopic overview of distinctive morphologies and patterns of socio-spatial segregation. In this study, we explore the distribution of residential swimming pools as indicators of the use of land and water at the metropolitan scale, in relation to recent changes in the socio-spatial structure of a large Mediterranean city (Athens, Greece). Our results indicate a polarized spatial distribution of swimming pools, still considered a luxury affordable only for a minor segment of the Greek population. The analysis highlights the spatial linkages between concentration of residential pools, class segregation and low-density settlements, indicating that the socio-spatial structure of Athens remains characterized by persistent disparities between rich and poor neighborhoods. Comparison with another Mediterranean city (Barcelona) demonstrates the peculiarity of Athens’ recent development as reflected in the fragmented and polarized urban structure. The study provides an alternative reading of recent Mediterranean urban growth by considering pools as a “landmark” for urban sprawl, producing contested landscapes of localized social segregation.     

Debris flows of 28 June 2014 near the Arshan village (Siberia,Republic of Buryatia,Russia)

On 28 June 2014, high intensity rainfall resulted in seven simultaneous debris flows going down the slopes of the Tunka Ridge in the vicinity of Arshan village, which is a balneological and alpine resort (51° 54′ 31″ N, 102° 25′ 44″ E). The debris flows caused one life loss and several injuries, 112 buildings were damaged, and 15 were completely destroyed. The total volume of the transported deposits amounted to 3?×?10⁶ m³. Debris flows’ formation began with the failure of weak sediments in the hanging cirques. Similar phenomena had not been recorded in the study area for over 40 years. The article presents a complete picture of the event and analysis of geological, geomorphological, and meteorological conditions for debris flows formation, for which extreme local rainfall was the major cause.     

Multi‐kilometre long pathway of geofluids migration: Clues concerning an ophiolite serpentinization setting possibly responsible for the inferred abiotic provenance of methane in thermal water outflows of the South‐West Carpathians (Romania)

Methane occurrences displaying signatures of a possible abiotic origin had previously been reported in the South‐West Carpathians (Romania). Such an accumulation, at Tisovi?a, was intercepted by a well drilled in an ophiolitic rocks massif, whereas in two other localities—situated tens of kilometres faraway—the concerned methane is released via thermal groundwater outflows that are apparently not associated with any ultramafic products. By using groundwater ionic compositions, corroborated with previously published isotopic (¹³C‐CH₄, ²H‐CH₄, ³He/⁴He) and molecular gas analyses, we assessed in more detail the conjectured abiotic provenance of methane, and quantitatively investigated the hypothesis of a progressive mixing between two, abiotic and thermogenic, methane end‐members. The corresponding geofluids behaviour was modelled by hypothesizing a “concealed” ophiolite serpentinization setting (largely similar to that at Tisovi?a), whose abiotic methane production was “diverted” towards remote discharges at ground surface, via a ~20‐km‐long flowpath supposedly generated by recently operating extensional tectonics.     

Growth,dynamics and deglaciation of the last British–Irish ice sheet: the deep-sea ice-rafted detritus record

The evolution and dynamics of the last British–Irish Ice Sheet (BIIS) have hitherto largely been reconstructed from onshore and shallow marine glacial geological and geomorphological data. This reconstruction has been problematic because these sequences and data are spatially and temporally incomplete and fragmentary. In order to enhance BIIS reconstruction, we present a compilation of new and previously published ice-rafted detritus (IRD) flux and concentration data from high-resolution sediment cores recovered from the NE Atlantic deep-sea continental slope adjacent to the last BIIS. These cores are situated adjacent to the full latitudinal extent of the last BIIS and cover Marine Isotope Stages (MIS) 2 and 3. Age models are based on radiocarbon dating and graphical tuning of abundances of the polar planktonic foraminifera Neogloboquadrina pachyderma sinistral (% Nps) to the Greenland GISP2 ice core record. Multiple IRD fingerprinting techniques indicate that, at the selected locations, most IRD are sourced from adjacent BIIS ice streams except in the centre of Heinrich (H) layers in which IRD shows a prominent Laurentide Ice Sheet provenance. IRD flux data are interpreted with reference to a conceptual model explaining the relations between flux, North Atlantic hydrography and ice dynamics. Both positive and rapid negative mass balance can cause increases, and prominent peaks, in IRD flux. First-order interpretation of the IRD record indicates the timing of the presence of the BIIS with an actively calving marine margin. The records show a coherent latitudinal, but partly phased, signal during MIS 3 and 2. Published data indicate that the last BIIS initiated during the MIS 5/4 cooling transition; renewed growth just before H5 (46 ka) was succeeded by very strong millennial-scale variability apparently corresponding with Dansgaard–Oeschger (DO) cycles closely coupled to millennial-scale climate variability in the North Atlantic region involving latitudinal migration of the North Atlantic Polar Front. This indicates that the previously defined “precursor events” are not uniquely associated with H events but are part of the millennial-scale variability. Major growth of the ice sheet occurred after 29 ka with the Barra Ice Stream attaining a shelf-edge position and generating turbiditic flows on the Barra–Donegal Fan at ～27 ka. The ice sheet reached its maximum extent at H2 (24 ka), earlier than interpreted in previous studies. Rapid retreat, initially characterised by peak IRD flux, during Greenland Interstadial 2 (23 ka) was followed by readvance between 22 and 16 ka. Readvance during H1 was only characterised by BIIS ice streams draining central dome(s) of the ice sheet, and was followed by rapid deglaciation and ice exhaustion. The evidence for a calving margin and IRD supply from the BIIS during Greenland Stadial 1 (Younger Dryas event) is equivocal. The timing of the initiation, maximum extent, deglacial and readvance phases of the BIIS interpreted from the IRD flux record is strongly supported by recent independent data from both the Irish Sea and North Sea sectors of the ice sheet.     

Raman study of MgCO3–FeCO3 carbonate solid solution at high pressures up to 55 GPa

Magnesite, siderite and ferromagnesites Mg_1?x Fe _x CO₃ (x = 0.05, 0.09, 0.2, 0.4) were characterized using in situ Raman spectroscopy at high pressures up to 55 GPa. For the Mg–Fe-carbonates, the Raman peak positions of six modes (T, L, ν₄, ν₁, ν₃ and 2ν₂) in the dependence of iron content in the carbonates at ambient conditions are presented. High-pressure Raman spectroscopy shows that siderite undergoes a spin transition at ~40 GPa. The examination of the solid solutions with compositions Mg_0.6Fe_0.4CO₃, Mg_0.8Fe_0.2CO₃, Mg_0.91Fe_0.09CO₃ and Mg_0.95Fe_0.05CO₃ indicates that with increase in the amount of the Fe spin transition pressure increases up to ~45 GPa.     

Magmatic evolution of the ultramafic–mafic Kharaelakh intrusion (Siberian Craton, Russia): insights from trace-element, U–Pb and Hf-isotope data on zircon

The ultramafic–mafic Kharaelakh intrusion in the northwestern part of the Siberian Craton (Russia) hosts major economic platinum-group-element (PGE)–Cu–Ni sulphide deposits. In situ U–Pb, REE and Hf-isotope analyses of zircon from these rocks, combined with detailed study of crystal morphology and internal structure, identify four zircon populations. U–Pb ages of these populations cover a significant time span (from 347 ± 16 to 235.7 ± 6.1 Ma) suggesting multiple magmatic events that cluster around 350 and 250 Ma, being consistent with two recognised stages of active tectonism in the development of the Siberian Craton. The oldest zircon population, however, represents previously unknown stage of magmatic activity in the Noril’sk area. Epsilon-Hf values of +2.3 to +16.3 in the analysed zircons reflect a dominant role of mantle-derived magmas and suggest that juvenile mantle material was the main source for the ultramafic–mafic Kharaelakh intrusion. A significant range in initial ¹⁷⁶Hf/¹⁷⁷Hf values, found in zircons that cluster around 250 Ma, indicate mixing between mantle and crustal magma sources. Our findings imply that economic intrusions hosting PGE–Cu–Ni deposits of the Noril’sk area have a far more complex geological history than is commonly assumed.