Influence of the sediment delivery ratio index on the analysis of silting and break risk in the Plasencia reservoir (Central System,Spain)

The random forest method was used to generate susceptibility maps for debris flows, rock slides, and active layer detachment slides in the Donjek River area within the Yukon Alaska Highway Corridor, based on an inventory of landslides compiled by the Geological Survey of Canada in collaboration with the Yukon Geological Survey. The aim of this study is to develop data-driven landslide susceptibility models which can provide information on risk assessment to existing and planned infrastructure. The factors contributing to slope failure used in the models include slope angle, slope aspect, plan and profile curvatures, bedrock geology, surficial geology, proximity to faults, permafrost distribution, vegetation distribution, wetness index, and proximity to drainage system. A total of 83 debris flow deposits, 181 active layer detachment slides, and 104 rock slides were compiled in the landslide inventory. The samples representing the landslide free zones were randomly selected. The ratio of landslide/landslide free zones was set to 1:1 and 1:2 to examine the results of different sample ratios on the classification. Two-thirds of the samples for each landslide type were used in the classification, and the remaining 1/3 were used to evaluate the results. In addition to the classification maps, probability maps were also created, which served as the susceptibility maps for debris flows, rock slides, and active layer detachment slides. Success and prediction rate curves created to evaluate the performance of the resulting models indicate a high performance of the random forest in landslide susceptibility modelling.     

Toxic metals in a highly urbanized industry-impacted estuary (Bahia Blanca Estuary,Argentina): spatio-temporal analysis based on GIS

Cadmium, chromium, nickel, and lead were evaluated in the particulate fraction at one of the most industrialized estuaries at the Southwestern Atlantic Ocean, through Geographic Information System (GIS). Concentrations were analyzed at 21 stations during 2008–2010. The highest metal concentrations (Cd: 8,9; Cr: 256,49; Ni: 27,02; Pb: 78,43 µg g^??1 d. w.) were recorded at the stations located near industrial and urban discharges situated along the estuary. In addition, Pb presented a different seasonal and spatial behavior in comparison with Cd, Cr and Ni. Winter and spring presented the higher concentrations of Pb, and the inner stations presented the higher values. The estuary is considered a moderate to strongly polluted and significantly polluted according to the Index of geoaccumulation (I_geo) and the Enrichment Factor of Cd, respectively. The Multidimensional Scaling plot showed three groups of stations: the inner, associated to low levels of metals (G1), middle stations (G2) with intermediate levels and the outer (G3) with the highest ones. In addition, this work reveals the usefulness of the GIS-mapping techniques in the distribution of pollutants along an estuarine environment and the environmental quality assessment of estuarine systems.     

Ecotoxicological evaluation of dredged sediments from Rodrigo de Freitas Lagoon (Rio de Janeiro State,Brazil) using bioassays with earthworms and collembolans

The toxicity and metal bioavailability were studied in dredged sediments from Rodrigo de Freitas Lagoon (Rio de Janeiro, RJ, Brazil) using acute and avoidance tests with Eisenia andrei, and reproduction tests with Folsomia candida. The sediment was mixed with an artificial soil, and two natural soils (ferralsol and chernosol—representative Brazilian tropical soils) to obtain the following doses: 1, 3, 6, 12, 18, 24 and 30%. Total metal concentrations were determined in the sediment to support the interpretation of ecotoxicological data. Metal concentrations in the mixtures were in agreement with the threshold limits established by Brazilian law. However, significant avoidance responses were found on doses ≥?3% and were the most sensitive endpoint. Earthworm mortality found in artificial soil mixtures (LC50?=?3.9) suggests higher toxicity levels than those obtained in ferralsol (LC50?=?7.6%) and chernosol (11.0%) treatments. Earthworm mortality, avoidance responses and collembolan reproduction levels found in ferralsol mixtures (LC50?=?9.2; avoidance EC50?=?2.3%; reproduction EC50?=?2.8%) were higher compared to chernosol treatments (LC50?=?11.0%; avoidance EC50?=?4.3%; reproduction EC50?=?4.9%). The reduction of toxicity levels in chernosol mixtures is probably due to the abundance of expansive clay minerals in chernosols with capacity of adsorbing metals and other xenobiotic substances from soil pore water, decreasing metal bioavailability. Finally, threshold limits defined by Brazilian legislation for soil quality and land disposal of dredged sediments are not sufficient to prevent noxious effects on soil fauna and should be complemented with a preliminary ecotoxicological evaluation.     

Diamond in metasedimentary crustal rocks from Pohorje,Eastern Alps: a window to deep continental subduction

We report the first finding of diamond and moissanite in metasedimentary crustal rocks of Pohorje Mountains (Slovenia) in the Austroalpine ultrahigh‐pressure (UHP) metamorphic terrane of the Eastern Alps. Microscopic observations and Raman spectroscopy show that diamond occurs in situ as inclusions in garnet, being heterogeneously distributed. Under the optical microscope, diamond‐bearing inclusions are of cuboidal to rounded shape and of pinkish, yellow to brownish colour. The Raman spectra of the investigated diamond show a sharp, first order peak of sp³‐bonded carbon, in most cases centred between 1332 and 1330 cm^?1, with a full width at half maximum between 3 and 5 cm^?1. Several spectra show Raman bands typical for disordered graphitic (sp²‐bonded) carbon. Detailed observations show that diamond occurs either as a monomineralic, single‐crystal inclusion or it is associated with SiC (moissanite), CO₂ and CH₄ in polyphase inclusions_. This rare record of diamond occurring with moissanite as fluid‐inclusion daughter minerals implies the crystallization of diamond and moissanite from a supercritical fluid at reducing conditions. Thermodynamic modelling suggests that diamond‐bearing gneisses attained P–T conditions of ≥3.5 GPa and 800–850 °C, similar to eclogites and garnet peridotites. We argue that diamond formed when carbonaceous sediment underwent UHP metamorphism at mantle depth exceeding 100 km during continental subduction in the Late Cretaceous (c. 95–92 Ma). The finding of diamond confirms UHP metamorphism in the Pohorje Mountains, the most deeply subducted part of Austroalpine units.     

Zircon geochronology and geochemistry to constrain the youngest eruption events and magma evolution of the Mid-Miocene ignimbrite flare-up in the Pannonian Basin,eastern central Europe

A silicic ignimbrite flare-up episode occurred in the Pannonian Basin during the Miocene, coeval with the syn-extensional period in the region. It produced important correlation horizons in the regional stratigraphy; however, they lacked precise and accurate geochronology. Here, we used U–Pb (LA-ICP-MS and ID-TIMS) and (U–Th)/He dating of zircons to determine the eruption ages of the youngest stage of this volcanic activity and constrain the longevity of the magma storage in crustal reservoirs. Reliability of the U–Pb data is supported by (U–Th)/He zircon dating and magnetostratigraphic constraints. We distinguish four eruptive phases from 15.9 ± 0.3 to 14.1 ± 0.3 Ma, each of which possibly includes multiple eruptive events. Among these, at least two large volume eruptions (>10 km³) occurred at 14.8 ± 0.3 Ma (Demjén ignimbrite) and 14.1 ± 0.3 Ma (Harsány ignimbrite). The in situ U–Pb zircon dating shows wide age ranges (up to 700 kyr) in most of the crystal-poor pyroclastic units, containing few to no xenocrysts, which implies efficient recycling of antecrysts. We propose that long-lived silicic magma reservoirs, mostly kept as high-crystallinity mushes, have existed in the Pannonian Basin during the 16–14 Ma period. Small but significant differences in zircon, bulk rock and glass shard composition among units suggest the presence of spatially separated reservoirs, sometimes existing contemporaneously. Our results also better constrain the time frame of the main tectonic events that occurred in the Northern Pannonian Basin: We refined the upper temporal boundary (15 Ma) of the youngest counterclockwise block rotation and the beginning of a new deformation phase, which structurally characterized the onset of the youngest volcanic and sedimentary phase.     

Progressive failure leading to the 3 December 2013 rockfall at Puigcercós scarp (Catalonia,Spain)

A detailed analysis of the pre-failure behavior of the 3 December 2013 rockfall (1,012 m³) occurred on Puigcercós pilot study area (Catalonia, Spain) is presented. The exact date of failure was obtained based on a photographic monitoring performed every 4 h. The long-term monitoring (2,217 days) of the rock slope carried out by a Terrestrial LiDAR allowed the early detection of both pre-failure deformation and precursory rockfalls preceding the final failure. By means of the analysis of the pre-failure deformation, four different deformed areas were detected and the tertiary creep phase was observed in three of them. An attempt to predict the time to failure was performed using the Fukuzono’s (1985) method. Furthermore, the temporal evolution of the precursory rockfalls occurred in those four areas during the progressive failure showed a close resemblance with the exponential pattern of the cumulated displacements at tertiary creep stage. Finally, the study of the meteorological conditions did not show any single triggering factor associated with the final failure. Reversely, the increase in the occurrence of precursory rockfalls on several areas of the slope together with the observed acceleration on the deformation pattern reinforce the role of a progressive degradation of the stability conditions, which ultimately leaded to the 3 December rockfall event.     

Canopy dieback in the upper montane rain forests of Sri Lanka

In 1978 a patch of dying upper montane rain forest had been observed on the slope of Thotupolakanda above Horton Plains. Patches in the upper montane rain forests of Sri Lanka were also recorded in 1980/81. All these sites were on windswept western slopes and ridges with stunted tree growth and shallow soil. From 1971 to 1983 Sri Lanka experienced some exceptionally dry years. The severe droughts of 1976 might have cause or “triggered” that dieback. After heavy rains between 1983 and 1986, these forests showed signs of recovery. Some trees had survived and sprouted again. Tree saplings were found, but regeneration was very low and further impeded by serious frost in February 1986. The influence of drought and frost clearly indicates the vulnerability of the stunted upper montane rain forest in the highest and wind-exposed regions of Sri Lanka.     

Causes of the famine among the rural population of the Sahelian zone of the Sudan

Taking the example of W Sudan, an analysis of the climatic incidents leading to the two recent famine disasters is made. On this natural background, the human side is investigated. Focus is directed towards the fragile economic structure of the famine-prone population groups. An early-warning system for famine in the Sahelian Zone is proposed taking grain production and storage, livestock development and the relationship between the prices of livestock and grain as major indicators.     

Die Wurzel der Osning-Überschiebung und der Mechanismus herzynischer Inversionsstörungen in Mitteleuropa

Zusammenfassung Neuere Untersuchungen ergaben, daß die Osning-Überschiebung als flache Störung in der steilen südlichen Randverwerfung der Ibbenbürener Karbonscholle wurzelt. Die Karbonscholle selbst ist von fiedrig angeordneten Randbrüchen begrenzt, die offenbar Teil eines varistischen Osning-Lineamentes sind. Das tektonische Inventar der Karbonscholle und die Osning-Überschiebung im Deckgebirge des südlichen Vorlandes werden als Folge einer Einengung und Heraushebung der Scholle in der Oberkreide gesehen, wobei die fiedrige Anordnung der Randstörungen eine Umsetzung horizontaler Seitenverschiebungen in Vertikalbewegungen bewirkte. Es wird angenommen, daß die Osning-Überschiebung generell in einem steilen Tiefenbruch wurzelt. Die Osning-Zone und andere herzynisch streichende Bruchsysteme mit daran gebundenen Falten und Überschiebungen dürften ihre Ursache in konvergierenden Schollenbewegungen mit horizontalen Seitenverschiebungen haben.

---

Recent investigations revealed that the Osning thrust originates as a low angle plane in the southern marginal fault of the Ibbenbüren Carboniferous block. The fault block itself is limited by steep faults, which are considered to be en echelon faults as part of the variscan Osning lineament.The structures of the fault block indicate a compression and uplift of the Ibbenbüren fault block by strike-slip movements at the en echelon Osning lineament. In connection with the uplift compressional and lateral shearing movements produced the south vergent Osning thrust within the overlaying strata. Thus, it is concluded, that the flat Osning thrust in their total extension originates in steep faults. It is further presumed that Osning Zone as well as other NW-SE striking fault systems connected with folds and thrusts in Middle Europe are caused by transpression.

---

Résumé Des études récentes amènent à regarder le charriage de l'Osning comme un accident faiblement incliné qui s'enracine dans la faille redressée formant la bordure sud du bloc carbonifère d'Ibbenbüren. Le bloc carbonifère est lui-même limité par des failles marginales en échelons, considérées comme faisant partie du linéament hercynien de l'Osning. L'inventaire tectonique du bloc carbonifère et le charriage de l'Osning dans la couverture de l'avant-pays méridional sont interprétés comme les effets d'un raccourcissement et d'une montée du bloc pendant le Crétacé supérieur, la configuration des failles marginales en échelons étant responsable de la transformation des déplacements horizontaux en mouvements verticaux. On conclut que le charriage de l'Osning, dans son ensemble, s'enracine dans une fracture profonde à fort pendage. La zone de l'Osning ainsi que d'autres zones failleuses WNW-ESE d'Europe Centrale avec les plis et les charriages qui leur sont associés sont considérés comme le résultat de mouvements convergents de blocs liés à des décrochements.

---

, . , . , , . , . .