The role of magma mixing/mingling and cumulate melting in the Neapolitan Yellow Tuff caldera-forming eruption (Campi Flegrei,Southern Italy)

Understanding the mechanisms responsible for the generation of chemical gradients in high-volume ignimbrites is key to retrieve information on the processes that control the maturation and eruption of large silicic magmatic reservoirs. Over the last 60 ky, two large ignimbrites showing remarkable zoning were emplaced during caldera-forming eruptions at Campi Flegrei (i.e., Campanian Ignimbrite, CI, ~?39 ka and Neapolitan Yellow Tuff, NYT, ~?15 ka). While the CI displays linear compositional, thermal and crystallinity gradients, the NYT is a more complex ignimbrite characterized by crystal-poor magmas ranging in composition from trachy-andesites to phonolites. By combining major and trace element compositions of matrix glasses and mineral phases from juvenile clasts located at different stratigraphic heights along the NYT pyroclastic sequence, we interpret such compositional gradients as the result of mixing/mingling between three different magmas: (1) a resident evolved magma showing geochemical characteristics of a melt extracted from a cumulate mush dominated by clinopyroxene, plagioclase and oxides with minor sanidine and biotite; (2) a hotter and more mafic magma from recharge providing high-An plagioclase and high-Mg clinopyroxene crystals and (3) a compositionally intermediate magma derived from remelting of low temperature mineral phases (i.e., sanidine and biotite) within the cumulate crystal mush. We suggest that the presence of a refractory crystal mush, as documented by the occurrence of abundant crystal clots containing clinopyroxene, plagioclase and oxides, is the main reason for the lack of erupted crystal-rich material in the NYT. A comparison between the NYT and the CI, characterized by both crystal-poor extracted melts and crystal-rich magmas representing remobilized portions of a “mature” (i.e., sanidine dominated) cumulate residue, allows evaluation of the capability of crystal mushes of becoming eruptible upon recharge.     

Using topographical attributes to evaluate gully erosion proneness (susceptibility) in two mediterranean basins: advantages and limitations

Empirical multivariate predictive models represent an important tool to estimate gully erosion susceptibility. Topography, lithology, climate, land use and vegetation cover are commonly used as input for these approaches. In this paper, two multivariate predictive models were generated for two gully erosion processes in San Giorgio basin (Italy) and Mula River basin (Spain) using only topographical attributes as independent variables. Initially, nine models (five for San Giorgio and four for Mula) with pixel sizes ranging from 2 to 50 m were generated, and validation statistics were calculated to estimate the optimal pixel size. The best models were selected based on model performance using the area under the receiver operating characteristic (AUC) curve and the generalized cross-validation. The best pixel size was 4 m in the San Giorgio basin and 20 m in the Mula basin. The finest resolution was not necessarily the best; rather, the relationship between digital elevation model resolution and size of the landform was important. The two selected models showed an excellent performance with AUC values of 0.859 and 0.826 for San Giorgio and Mula, respectively. The Topographic Wetness Index and the general curvature were identified as key topographical attributes in San Giorgio and Mula basins, respectively. Both attributes were related to the processes observed in the field and described in the literature. Finally, maps of gully erosion susceptibility were produced for each basin. These maps showed that 22 and 20 % of San Giorgio and Mula basins, respectively, present favourable conditions for the development of gullies.     

Adaptation of the Canadian Fire Weather Index to Mediterranean forests

Natural Hazards - The Canadian Fire Weather Index (FWI) is one of the most used tools to forecast forest fire hazard. In this paper, we propose an adaptation of the FWI to take into account the...     

Observations and box model analysis of radon-222 in the atmospheric surface layer at L’Aquila,Italy: March 2009 case study

Two years of radon-222 observations collected at L’Aquila (Italy) in the atmospheric surface layer during 2004–2006 were analyzed in correlation with meteorological data and other atmospheric tracers. A box model was developed to better understand the mechanisms of diurnal and seasonal variability of the tracer and to indirectly assess the magnitude of the monthly averaged radon soil flux in the L’Aquila measurement site. The model was successfully validated with measurements, with a 0.8 average correlation coefficient between hourly values for the whole period of radon observations. Measurements taken during March 2009 were analyzed to find possible signs of perturbation due to the ongoing seismic activity that would have reached its peak on the 6 April 2009 destructive earthquake. Contrary to the professed (and unpublished) dramatic increases of radon activity unofficially announced to the inhabitants at that time, the study presented here shows that no radon activity increase took place in L’Aquila with respect to a previous ‘seismically unperturbed’ year (same month with similar meteorological conditions), but that an average 30 % decrease was experienced. This conclusion is reached from a direct comparison of observed data and also as a result of the previously validated radon box model constrained by actual meteorological data, from which an indirect estimate of a 17 % reduction of the radon soil flux is obtained.     

Distribution and origin of nitrate in groundwater in an urban and suburban aquifer in Mar del Plata,Argentina

The impact of urbanization on groundwater quality is of special concern for water managers dealing with the provision of drinking water to large urban centers. Nitrate is one of the most common contaminants found in urban aquifers. This paper presents a case study aiming at evaluating the distribution and sources of nitrate in an urban aquifer in the city of Mar del Plata, Argentina. Four study zones under different land uses, including a pristine, a semi-rural, an intermediate, and an urban area, were evaluated as a part of this study. The three latter zones are linked by the groundwater flow system. The average nitrate concentration in the pristine area is 6.7 mg/L as nitrate and is over the permissible level of 50 mg/L for drinking water in the other areas. In the semi-rural area it ranges from 39.2 to 107.1 mg/L with an average value of 38.2 mg/L and the nitrate concentration tends to decrease in the intermediate zone to an average value of 38.2 mg/L; however, values above 60 mg/L are also observed there. Then the nitrate concentration in the urban area water is higher than that in the intermediate zonewater ranging from 48.2 to 100.3 mg/L with an average value of 67.3 mg/L. Data on the stable isotopes 15N and 18O in nitrate show that the main sources of nitrate in the study area are manure associated to agriculture uses and cesspools in the semi-rural area, and leakage of the sewage distribution network in the urban area, respectively. This is supported by a previous study which found that 20 % of the water flooding many underground structures in the city came from leakage of the sewage network. No evidence of nitrate attenuation by denitrification was found in the groundwater. This study has shown that aquifers in urban areas can be affected by agricultural activity in the upstream areas and leakage of the sewage network in the urban area.     

A continuous stable isotope record from the penultimate glacial maximum to the Last Interglacial (159–121 ka) from Tana Che Urla Cave (Apuan Alps,central Italy)

Relatively few radiometrically dated records are available for the central Mediterranean spanning the marine oxygen isotope stage 6–5 (MIS 6–5) transition and the first part of the Last Interglacial. Two flowstone cores from Tana che Urla Cave (TCU, central Italy), constrained by 19 U/Th ages, preserve an interval of continuous speleothem deposition between ca. 159 and 121 ka. A multiproxy record (δ¹⁸O, δ¹³C, growth rate and petrographic changes) obtained from this flowstone preserves significant regional-scale hydrological changes through the glacial/interglacial transition and multi-centennial variability (interpreted as alternations between wetter and drier periods) within both glacial and interglacial stages. The glacial stage shows a wetter period between ca. 154 and 152 ka, while the early to middle Last Interglacial period shows several drying events at ca. 129, 126 and 122 ka, which can be placed in the wider context of climatic instability emerging from North Atlantic marine and NW European terrestrial records. The TCU record also provides important insights into the evolution of local environmental conditions (i.e. soil development) in response to regional and global-scale climate events.     

华南、华北地块中生代构造演化与超高压变质岩的折返机制

本文在讨论中国东部现有构造演化模式基础上，着重从华北与华南地块之间板块尺度的动力学过程剖析秦岭－大别中生代造山带构造演化，以及大别－苏鲁超高压变质地体的形成和折返过程。晚二叠世－中三叠世华南地块向华北地块持续挤压，陆壳大规模俯冲导致超高压变质作用的产生，而华北地块在晚三叠世至早侏罗世发生快速逆时针旋转，使得这一地区上地幔深度的超高压变质地体快速折返至下地壳。由于超高压变质地体侵位后，地壳结构、构造的差异，在南北地块的进一步挤压下，造成中国东部晚侏罗世－早白垩世郯庐断裂带的巨大左行剪切。     

Vestan lithologies mapped by the visual and infrared spectrometer on Dawn

We present global lithological maps of the Vestan surface based on Dawn mission's Visible InfraRed (VIR) Spectrometer acquisitions with a spatial sampling of 200 m. The maps confirm the results obtained with the data set acquired by VIR with a spatial sampling of 700 m, that the reflectance spectra of Vesta's surface are dominated by pyroxene absorptions that can be interpreted within the context of the distribution of howardites, eucrites, and diogenites (HEDs). The maps also partially agree with the ground and Hubble Space Telescope observations: they confirm the background surface being an assemblage of howardite or polymict eucrite, as well as the location of a diogenitic‐rich spot; however, there is no evidence of extended olivine‐rich regions in the equatorial latitudes. Diogenite is revealed on the Rheasilvia basin floor, indicating that material of the lower crust/mantle was exposed. VIR also detected diogenites along the scarp of Matronalia Rupes, and the rims of Severina and a nearby, unnamed crater, and as ejecta of Antonia crater. The diogenite distribution is fully consistent with petrological constraints; although the mapped distribution does not provide unambiguous constraints, it favors the hypothesis of a magma ocean.     

Middle-Upper Miocene stratigraphy of the Taman Peninsula, Eastern Paratethys

The stratigraphy of the Taman Peninsula is defined using the sections at Zelensky Hill ?? Panagia, Popov Kamen, Taman and Zheleznyi Rog. The stratigraphy is constructed from distribution of mollusks, foraminifers, nannofossils, diatoms, and organic-walled phytoplankton, as well as incorporating paleomagnetic data. The occurrence of oceanic diatom species in the Middle-Upper Sarmatian, Maeotian and Lower Pontian makes a direct correlation possible between the sections studied, the Mediterranean basin and oceanic zonation. The new data on planktonic and benthic biotic groups suggests a pulsating connection of the Eastern Paratethys with the open marine basins, especially during transitional intervals within constant environments. Comprehensive studies of the Chokrakian-Kimmerian microbiota provide evidence for several levels of marine microbiotic associations that are related to short-term marine invasions. The biotic and paleomagnetic data of the Taman Peninsula sections give a more comprehensive, but sometimes a controversial picture on the Eastern Paratethys history and the nature of its relationship with the adjacent marine basins.     

Erratum to: Geotechnical and mineralogical properties of weak rocks from Central Greece

The original version of this article was published in Central European Journal of Geosciences volume 1, issue 4 (2009), pp 431–442, DOI:10.2478/v10085-009-0029-0. Unfortunately the original version of this article contains mistakes in authors names which we correct here. Editorial staff of the journal apologise for any inconvenience that may result from the oversight.