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251.
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. 相似文献
252.
253.
Debris flows of 28 June 2014 near the Arshan village (Siberia,Republic of Buryatia,Russia) 总被引:1,自引:0,他引:1
Alena V. Kadetova Artem A. Rybchenko Elena A. Kozireva Vadim A. Pellinen 《Landslides》2016,13(1):129-140
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. 相似文献
254.
Horia Mitrofan Constantin Marin Florina Chitea Nicoleta Cadicheanu Ioan Povar Alin Tudorache Daniela Elena Ioni Mirela‐Adriana Anghelache 《地学学报》2021,33(1):56-73
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. 相似文献
255.
256.
James D. Scourse Anna I. Haapaniemi Elena Colmenero-Hidalgo Victoria L. Peck Ian R. Hall William E.N. Austin Paul C. Knutz Rainer Zahn 《Quaternary Science Reviews》2009,28(27-28):3066-3084
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. 相似文献
257.
Anna Spivak Natalia Solopova Valerio Cerantola Elena Bykova Egor Zakharchenko Leonid Dubrovinsky Yuriy Litvin 《Physics and Chemistry of Minerals》2014,41(8):633-638
Magnesite, siderite and ferromagnesites Mg1?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 Mg0.6Fe0.4CO3, Mg0.8Fe0.2CO3, Mg0.91Fe0.09CO3 and Mg0.95Fe0.05CO3 indicates that with increase in the amount of the Fe spin transition pressure increases up to ~45 GPa. 相似文献
258.
259.
Kreshimir Nenadovitch Malitch Elena A. Belousova William L. Griffin Inna Yu Badanina Norman J. Pearson Sergey L. Presnyakov Evgeniya V. Tuganova 《Contributions to Mineralogy and Petrology》2010,159(6):753-768
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. 相似文献
260.
Lutz Christoph Götze Rainer Abart Erik Rybacki Lukas M. Keller Elena Petrishcheva Georg Dresen 《Mineralogy and Petrology》2010,99(3-4):263-277
We synthesize reaction rims between thermodynamically incompatible phases in the system MgO-Al2O3-SiO2 applying uniaxial load using a creep apparatus. Synthesis experiments are done in the MgO-SiO2 and in the MgO-Al2O3 subsystems at temperatures ranging from 1150 to 1350 °C imposing vertical stresses of 1.2 to 29 MPa at ambient pressure and under a constant flow of dry argon. Single crystals of synthetic and natural quartz and forsterite, synthetic periclase and synthetic corundum polycrystals are used as starting materials. We produce enstatite rims at forsterite-quartz contacts, enstatite-forsterite double rims at periclase-quartz contacts and spinel rims at periclase-corundum contacts. We find that rim growth under the “dry” conditions of our experiments is sluggish compared to what has been found previously in nominally “dry” piston cylinder experiments. We further observe that the nature of starting material, synthetic or natural, has a major influence on rim growth rates, where natural samples are more reactive than synthetic ones. At a given temperature the effect of stress variation is larger than what is anticipated from the modification of the thermodynamic driving force for reaction due to the storage of elastic strain energy in the reactant phases. We speculate that this may be due to modification of the physical properties of the polycrystals that constitute the reaction rims or by deformation under the imposed load. In our experiments rim growth is very sluggish at forsterite-quartz interfaces. Rim growth is more rapid at periclase-quartz contacts. The spinel rims that are produced at periclase-corundum interfaces show parabolic growth indicating that reaction rim growth is essentially diffusion controlled. From the analysis of time series done in the MgO-Al2O3 subsystem we derive effective diffusivities for the Al2O3 and the MgO components in a spinel polycrystal as ${\rm D}_{MgO} = 1.4 \pm 0.2 \cdot 10^{-15}$ m2/s and ${\rm D}_{Al_2O_3} = 3.7 \pm 0.6 \cdot 10^{-16}$ m2/s for T?=?1350 °C and a vertical stress of 2.9 MPa. 相似文献