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31.
François Bache Speranta‐Maria Popescu Marina Rabineau Christian Gorini Jean‐Pierre Suc Georges Clauzon Jean‐Louis Olivet Jean‐Loup Rubino Mihaela Carmen Melinte‐Dobrinescu Ferran Estrada Laurent Londeix Rolando Armijo Bertrand Meyer Laurent Jolivet Gwénaël Jouannic Estelle Leroux Daniel Aslanian Antonio Tadeu Dos Reis Ludovic Mocochain Nikola Dumurdžanov Ivan Zagorchev Vesna Lesić Dragana Tomić M. Namık Çağatay Jean‐Pierre Brun Dimitrios Sokoutis Istvan Csato Gülsen Ucarkus Ziyadin Çakır 《Basin Research》2012,24(2):125-153
The Messinian Salinity Crisis is well known to have resulted from a significant drop of the Mediterranean sea level. Considering both onshore and offshore observations, the subsequent reflooding is generally thought to have been very sudden. We present here offshore seismic evidence from the Gulf of Lions and re‐visited onshore data from Italy and Turkey that lead to a new concept of a two‐step reflooding of the Mediterranean Basin after the Messinian Salinity Crisis. The refilling was first moderate and relatively slow accompanied by transgressive ravinement, and later on very rapid, preserving the subaerial Messinian Erosional Surface. The amplitude of these two successive rises of sea level has been estimated at ≤500 m for the first rise and 600–900 m for the second rise. Evaporites from the central Mediterranean basins appear to have been deposited principally at the beginning of the first step of reflooding. After the second step, which preceeded the Zanclean Global Stratotype Section and Point, successive connections with the Paratethyan Dacic Basin, then the Adriatic foredeep, and finally the Euxinian Basin occurred, as a consequence of the continued global rise in sea level. A complex morphology with sills and sub‐basins led to diachronous events such as the so‐called ‘Lago Mare’.This study helps to distinguish events that were synchronous over the entire Mediterranean realm, such as the two‐step reflooding, from those that were more local and diachronous. In addition, the shoreline that marks the transition between these two steps of reflooding in the Provence Basin provides a remarkable palaeogeographical marker for subsidence studies. 相似文献
32.
Mihaela Grigore Richard Sakurovs David French Veena Sahajwalla 《International Journal of Coal Geology》2008,76(4):301-308
Degradation of coke in the blast furnace is influenced by its inherent mineral matter, the formation of which is itself dependent upon the nature of the coal mineral matter. To date few studies have been made of coke mineralogy and its relationship to the mineralogy of the parent coal. In this study the effect of carbonisation on coal mineral matter has been investigated by a detailed quantitative mineralogical examination of nine cokes and their parent coals. The quantitative analysis was performed on X-ray diffraction patterns of the mineral matter of cokes and coals, using SIROQUANT™. Coke mineralogy and its composition varied strongly between cokes, more strongly than variations in elemental composition of the ash. The mineral matter in the studied cokes consisted of crystalline mineral phases and also significant levels of amorphous phase (ranging between 44 and 75%). Decomposition of clays such as kaolinite, montmorillonite, illite and chamosite produced the amorphous phase and some of the crystalline mineral phases such as mullite, γ-alumina, spinel, cristobalite and leucite. The type of association of mineral matter in coals had an important role in how the clays decomposed. For example, association of kaolinite with silica-bearing minerals in intimate intermixture favoured formation of mullite over γ-alumina. Akermanite and diopside result from reaction of kaolinite with associated calcium bearing minerals (calcite, dolomite or ankerite). Quartz, fluorapatite and the three polymorphs of TiO2 (anatase, brookite and rutile) were the coal minerals that were least affected during carbonisation, as they were also found in the cokes, yet even they were affected in some cases. 相似文献
33.
Fluctuation in calpionellid, foraminiferal, and nannofossil diversity and abundance are documented in two successions located in the eastern part of the Upper Jurassic–Lower Cretaceous carbonate platform of the Southern Carpathian area, Romania. The lower part of the studied sections consists of upper Tithonian–upper Berriasian bioclastic limestones. This age is supported by the presence of the calpionellid assemblages assigned to the Crassicollaria, Calpionella, and Calpionellopsis Zones. Based on biostratigraphical data, a gap was identified within the uppermost Berriasian–base of the upper Valanginian (the interval encompasses the Boissieri, Pertransiensis, Campylotoxum, and lower part of the Verrucosum ammonite Zones). Hence, the upper Tithonian–upper Berriasian bioclastic limestones are overlain by upper Valanginian–lower Hauterivian pelagic limestones (the interval covered by the NK3B and NC4A nannofossil Subzones). A detailed qualitative and semiquantitative analysis of the nannoflora was carried out over this interval. To estimate the surface water fertility conditions, the nannoplankton-based nutrient index (NI) was calculated. The fluctuation pattern of NI allow us to recognize four phases in the investigated interval, as follows: (1) phase I (covering the lower part of the NK3B nannofossil Subzone and the upper part of the Verrucosum ammonite Zone, respectively) is characterized by low values of the NI (below 20%), by the dominance of the genus Nannoconus in the nannofloral assemblages (between 60–70%), and moderate abundance of Watznaueria barnesae (up to 23%), while the high-fertility nannofossils constitute a minor component of the assemblages; (2) phase II (placed in the NK3B nannofossil Subzone, extending from the top of Verrucosum ammonite Zone, up to the lower part of the Furcillata ammonite Zone) is characterized by increase of NI above 30%, a decrease of nannoconids (up to 50% at the top), while Watznaueria barnesae increases in abundance up to 27%. The fertility proxies (Diazomatolithus lehmanii, Zeugrhabdotus erectus, Discorhabdus rotatorius, and Biscutum constans) represent again a minor component of the recorded nannofloras (less than 7% in both sections), but they have an ascending trend; (3) phase III (which encompasses the boundary interval of the NK3B and NC4A nannofossil Subzones, corresponding to the upper part of the Furcillata ammonite Zone) contains higher NI values (over 35%, and up 52% towards the base of this phase), an abrupt nannoconid decrease (down to 20%), higher abundance of Watznaueria barnesae (over 30%), while the fertility nannofossils became an important nannofloral component, jointly amounting to almost 20%; (4) phase IV (identified within the NC4A Nannofossil Zone and corresponding to the boundary interval of the Furcillata and Radiatus ammonite Zones) is characterized by a decrease of NI to 25%, a recovery of the nannoconids up to 40%, a decline in abundance of Watznaueria barnesae to 25%, together with a pronounced drop of fertility taxa, which make together no more than 8%. We assume that maximum of eutrophication in the studied interval from the Southern Carpathians was in the Furcillata ammonite Zone. Notably, within the phases 2 and 3, the morphological changes identified in the benthic foraminiferal assemblages (the predominance of flattened morphologies, together with the presence of conical and trochospiral inflated forms), as well as the occurrence of the Zoophycos trace fossils and pyrite framboids, indicate dysaerobic conditions. In the Southern Carpathians, the late Valanginian–early Hauterivian biogeographical changes are coeval with the initiation of the carbonate platform drowning. 相似文献
34.
Graham Bird Paul A. Brewer Mark G. Macklin Dan Balteanu Mihaela Serban Basarab Driga Sorin Zaharia 《Applied Geochemistry》2008,23(12):3498-3518
The River Vişeu catchment in Maramureş County, northwestern Romania, has a long history of base and precious metal mining. Between 1994 and 2003 waste from mining activity at Baia Borşa was stored in the Novaţ-Roşu tailings pond in the upper Vişeu catchment. However, in March 2000, the tailings dam failed releasing approximately 100,000 m3 of contaminated water and 20,000 t of mineral-rich solid waste, which was routed downstream through the Rivers Novaţ, Vaser and Vişeu into the River Tisa. Following the accident metal (Cd, Cu, Pb, Zn) concentrations in river water and river channel sediment were assessed in samples collected annually (July 2000, 2001, 2002 and 2003) from 29 sites in the Vişeu catchment, downstream of the tailings pond. Additionally, the speciation of sediment-associated metals was established using a 4-stage sequential extraction procedure (SEP) and Pb isotope analysis (206/204Pb and 207/204Pb) was carried out to establish the provenance of contaminated sediments. Metal concentrations in river water were found to comply with EU directive ‘target’ values within four months of the failure. However, the impact of the spill upon river channel sediments was found to be much longer-lasting, with evidence of the delayed downstream remobilization of tailings stored within the narrow Novaţ valley following the dam failure, as well as continued inputs of contaminated sediment to the River Vişeu from the River Tisla, another mining-affected tributary. Comparison with data from other recent tailings dam failures, indicates that river system recovery rates depend upon local geomorphological conditions, hydrological regimes, and the nature and scale of post-spill clean-up operations. 相似文献
35.
Torben Koenigk Mihaela Caian Grigory Nikulin Semjon Schimanke 《Climate Dynamics》2016,46(1-2):317-337
Seasonal prediction skill of winter mid and high northern latitudes climate from sea ice variations in eight different Arctic regions is analyzed using detrended ERA-interim data and satellite sea ice data for the period 1980–2013. We find significant correlations between ice areas in both September and November and winter sea level pressure, air temperature and precipitation. The prediction skill is improved when using November sea ice conditions as predictor compared to September. This is particularly true for predicting winter NAO-like patterns and blocking situations in the Euro-Atlantic area. We find that sea ice variations in Barents Sea seem to be most important for the sign of the following winter NAO—negative after low ice—but amplitude and extension of the patterns are modulated by Greenland and Labrador Seas ice areas. November ice variability in the Greenland Sea provides the best prediction skill for central and western European temperature and ice variations in the Laptev/East Siberian Seas have the largest impact on the blocking number in the Euro-Atlantic region. Over North America, prediction skill is largest using September ice areas from the Pacific Arctic sector as predictor. Composite analyses of high and low regional autumn ice conditions reveal that the atmospheric response is not entirely linear suggesting changing predictive skill dependent on sign and amplitude of the anomaly. The results confirm the importance of realistic sea ice initial conditions for seasonal forecasts. However, correlations do seldom exceed 0.6 indicating that Arctic sea ice variations can only explain a part of winter climate variations in northern mid and high latitudes. 相似文献
36.
Mihaela Grigore Richard Sakurovs David French Veena Sahajwalla 《International Journal of Coal Geology》2008,75(4):213-224
Coke degradation in the blast furnace is influenced by its inherent mineral matter. Coke gasification affects the composition of the inherent mineral matter and would therefore be expected to change its effect on coke degradation. Four cokes prepared in a laboratory oven were exposed to carbon dioxide (100%) at approximately 900 °C for different carbon conversion levels, namely 15% and 75%. The mineralogy of the raw and reacted cokes was qualitatively and quantitatively determined. Gas composition was found to have a more significant effect on mineralogy than temperature; the mineralogy (qualitative and quantitative) being dramatically affected by carbon dioxide, whereas treatment at 900 °C in the absence of carbon dioxide resulted in little change. During gasification the reduced phases underwent transformations due to oxidation by carbon dioxide. Oxidation of the reduced phases enabled their reaction with adjacent minerals. Also, as gasification proceeds, the carbon in contact with the mineral matter is consumed, diminishing the contact surface area between them. 相似文献
37.
Horia Mitrofan Constantin Marin Dorel Zugr&#x;vescu Alin Tudorache Lucian Beu?iu Mihaela Radu 《地学学报》2008,20(2):87-94
The Na, K, Mg and Ca contents of certain deep‐origin groundwater discharges have been used by Giggenbach (1988) to define a series of ‘geoindicators’, which may provide hints on the up‐flow depth of origin, on the duration of the fluid ascent to the ground surface and on the associated CO2 flux. On occurrence of a Mw = 6.0 Vrancea earthquake, significant fluctuations of Giggenbach’s geoindicators have been recorded in a saline spring, some 50 km away from the epicentre. A pre‐seismic overall anomaly was monitored for 1 year and a half, the sharpest variations occurring about 3 months before the earthquake. Processes controlling the geoindicator fluctuations assumedly took place at 7–8 km depth, while the earthquake hypocenter depth was about 100 km. This could be an evidence for a mechanical coupling still existing between the seismogenic body in the lithosphere and the overlying crust. 相似文献
38.
The relationship between surficial sediment diatom species and measured environmental variables was explored in lakes from the Abitibi region of western Quebec. Diatom assemblages in 42 lakes were identified and their relationship with measured environmental variables was examined using multivariate statistical methods. Canonical correspondence analysis with forward selection and Monte Carlo permutation tests revealed that the three environmental variables pH, TP and DOC each accounted for statistically significant fractions of the variation in diatom taxa. A training set with 164 modern diatom taxa was used to derive transfer functions for lake-water pH, TP and DOC using weighted-averaging-partial-least-squares (WA-PLS) techniques. The models were developed to infer lake water pH, TP and DOC within the ranges 4–8 for pH, 2.75–30.0 g l–1 for TP, and 2.9–18.5 mg l–1 for DOC. These quantitative inference models may now be used to help identify and estimate the effects of natural disturbances on the biogeochemistry of Abitibi lakes during their historical development. 相似文献
39.
Graham Bird Paul A. Brewer Mark G. Macklin Mihaela Serban Dan Balteanu Basarab Driga 《Journal of Geochemical Exploration》2005,86(1):26-48
The Abrud–Arieş river system, western Romania, is subject to ongoing mining activity associated with Cu, Pb and Zn ore extraction. The catchment contains what is believed to be Europe's largest unutilized Au deposit at Roşia Montană that is planned to be exploited by open-cast mining techniques. The magnitude and environmental significance of metal (Cd, Cu, Pb, and Zn) concentrations in surface water and river channel sediment have been investigated along a 140 km reach of the Rivers Abrud and Arieş and 9 tributaries affected by mining. The speciation of sediment-bound metals was established using a 4-stage sequential extraction procedure (SEP) that identified four chemical phases: (1) exchangeable, (2) Fe/Mn oxides, (3) organic matter/sulphides and (4) residual. Peak solute and sediment-bound metal concentrations were found to occur in the River Abrud downstream of the EM Bucium mine and in mining-affected tributaries, with up to 71% of sites containing sediment metal concentrations in excess of Dutch intervention values. The River Arieş was found to be much less polluted than the River Abrud, with only Cu showing concentrations above guideline values, as a consequence of porphyry Cu mineralization in the catchment. The magnitude and spatial extent of metal pollution is influenced by local physico-chemical conditions and hydrological linkages between mining and local river systems. Sediment-bound Cd and Zn were found to be predominantly associated with the exchangeable phase of the sediment (9–74% and 6–65%, respectively), whilst Fe/Mn oxides (5–76%) and organic matter/sulphides (1–45%) generally accounted for a majority of Pb and Cu partitioning, respectively. Sites of environmentally significant sediment-metal pollution were identified in the Rivers Abrud and Arieş where exchangeable metal concentrations exceeded Dutch intervention values. The implications of metal contamination in the Arieş river basin to the proposed mining development at Roşia Montana are discussed in relation to other contaminated Romanian catchments and with the EU Water Framework Directive. 相似文献
40.
Volcanic ash layers in sediment cores are valuable geochronological markers in paleolimnological research. The composition
of volcanic glass is related to identifiable, chronologically distinctive volcanic eruptions. Consequently, tephra layers
provide time horizons allowing regional-scale correlations for lake sediments. Volcanic glass is often present in samples
routinely prepared by paleolimnologists such as diatom slides and thin sections. Knowledge of the morphological and optical
properties of volcanic glass allows for its identification. This is essential for the identification of ash layers that are
not macroscopically visible or to track their vertical migration in soft organic sediments. The purposes of this note are
to: (1) describe how the morphological (i.e., shape, vesicularity) and optical (i.e., refractive index and birefringence)
properties can be used to identify volcanic glass in preparations from lake sediments; and (2) show how the quantification
of volcanic glass from diatom slides is used to quantify the density-induced displacement of a 4.5 cm-thick Mazama ash-layer
through organic sediments and to approximate its timing of initial deposition. 相似文献