排序方式： 共有40条查询结果，搜索用时 18 毫秒
11.
Relu D. Roban Mihai N. Ducea Vlad I. Mihalcea Ioan Munteanu Victor Barbu Mihaela C. Melinte-Dobrinescu Cornel Olariu Mihai Vlăsceanu 《Basin Research》2023,35(1):244-270
We present new sedimentological, petrographical, palaeontological and detrital zircon U–Pb data on late Oligocene–early Miocene sedimentary rocks of the thin-skinned thrust belt of East Carpathians. These data were acquired to reconstruct the sedimentary routing system for two compositionally different turbidite fans made of the regionally extensive Kliwa and Fusaru formations. On the eastern margin of the Moldavides foreland basin, large low-gradient river systems draining the East European Platform provided well-sorted quartz-rich sand forming deltas on wide shallow shelves and thick Kliwa submarine fans. Due to the westward subduction of a thinned continental plate, the western basin margin was characterized by short, steep-gradient routing systems where sediment transport to deep water was mainly through hyperpycnal flows. The Getic and Bucovinian nappes of the East Carpathians and the exhumed Cretaceous–Early Palaeogene orogenic wedge fed Fusaru fans with poorly sorted lithic sand. The Fusaru fans trend northwards in the foredeep basin having an elongate depocentre, interfingering and then overlapping on the distal part of the Kliwa depositional system due to the eastward advance of the Carpathian fold-and-thrust belt. A smaller sediment input is supplied by southern continental areas (i.e. Moesian Platform, North Dobrogea and potentially the Balkans). In general, the sandstone interfingering between distinct basin floor fan systems is less well documented because the facies would be similar and there are not many systems that have a distinct sediment provenance like Kliwa and Fusaru systems. This case study improves the understanding of regional palaeogeography and sedimentary routing systems and provides observations relevant here or elsewhere on the interfingering turbidite fan systems. 相似文献
12.
Diatom assemblages in recent versus pre-industrial sediments were examined in 40 relatively undisturbed lakes from the Experimental
Lakes Area (ELA). The ELA region of northwestern Ontario receives low amounts of acidic deposition and the lakes have been
minimally disturbed by watershed development or other human activities. Consequently, this region represents an important
location to detect possible changes in lakes due to climate change. In over half of the lakes, planktonic taxa (especially
Discostella stelligera) increased between 10 and 40% since pre-industrial times. Changes in diatom assemblages are consistent with taxa that would
benefit from enhanced stratification and a longer ice-free season. We hypothesized that there should be a relationship between
stratification and measured chemical and physical characteristics of the study lakes. Multiple correlation analysis was undertaken
to see the relationship between planktonic taxa and D. stelligera since pre-industrial times and the physical and chemical characteristics of the study lakes. Lake depth was consistently
identified as an important variable. The timing of the increase in planktonic taxa within cores from these lakes will be needed
to rule out other possible regional changes that may also be occurring in the ELA region. 相似文献
13.
Wenxin Cao Dangpeng Xi Mihaela C.Melinte-Dobrinescu Tian Jiang Sherwood W.Wise Jr. Xiaoqiao Wan 《地学前缘(英文版)》2018,9(5):1465-1478
The Paleocene-Eocene Thermal Maximum(PETM) event was a dramatic global warming w55.93 Ma ago that resulted in biological extinction events, lithological changes, and major deviations in σ13 C and σ18 O.The southwestern Tarim Basin of China exposes successive Paleogene strata as a result of Tethys evolution and is considered an ideal region for PETM research.Based on calcareous nannoplankton biostratigraphy, we also used stable isotopes and XRD to analyse the Paleocene-Eocene transition in the Tarim Basin. At the Bashibulake Section, the PETM interval is characterized by(1) an abrupt negative shifts in σ13 C_(org), σ13 C_(carb) and σ18 O(-3%, -4.5% and -3%respectively);(2) an obvious negative correlation between the K-mode(Discoaster, Fasciculithus, Ericsonia, Sphenolithus and Rhomboaster) and r-mode(Biscutum, Chiasmolithus, Toweius) nannofossil taxa coincident with a robust Rhomboaster-Discoaster assemblage; and(3) a significant increase in the percentage of detrital input along with an increase in gypsum content. In the upper part of the Qimugen Formation Micrantholithus and Braarudosphaera are commonly found right up to the top where most of the nannofloras suffer a sharp decrease. In the overlying Gaijitage Formation, calcareous nannofossils disappear completely. These events indicate that the southwestern Tarim Basin was a warm shallow continental shelf during the deposition of the Qimugen Formation. From the early Eocene, the environment changed conspicuously. Evaporation increased and sea level fell, which led to an acid climate.This climate mode continued within the youngest unit studied, the Gaijitage Formation, characterized by the deposition of thick evaporates. Consequently, most of the marine plankton, i.e. calcareous nannoplankton, became disappear, because of the significant climate shift. 相似文献
14.
Climate change is a serious threat to all nations. This raises the question of why continuous treaty negotiations for more than two decades have failed to create a viable or adequate international climate regime. The current strategy of addressing climate change misdiagnoses the issue as a pollution problem by focusing on symptoms (emissions) and not on underlying causes (unsustainable development). In short, the wrong treaty is being negotiated. Drawing on negotiation analysis, it is argued that the existing and proposed climate treaties fail to meet the national interests of any party. An alternative strategy for addressing climate change is proposed that reframes the overall approach to reflect all countries’ development needs and links climate protection goals to the development structure of the treaty. The current deadlock over emissions reductions might be overcome and a mutual gains agreement reached by directing international cooperation towards promoting the provision of clean energy services for development and ensuring universal access to those services as part of an ‘early action’ agenda that will complement efforts to utilize forests and reduce other GHGs from multiple sectors. 相似文献
15.
Narjess El Euch-El Koundi Serge Ferry Jean-Pierre Suc Georges Clauzon Mihaela Carmen Melinte-Dobrinescu Christian Gorini Anissa Safra Fouad Zargouni 《地学学报》2009,21(1):41-48
Outcrops, offshore wells, electric logs and seismic profiles from northern Tunisia provide an opportunity to decipher the Messinian Salinity Crisis in the Strait of Sicily. Messinian deposits (including gypsum beds) near the Tellian Range reveal two successive subaerial erosional surfaces overlain by breccias and marine Zanclean clays, respectively. In the Gulf of Tunis, Messinian thick evaporites (mostly halite) are strongly eroded by a fluvial canyon infilled with Zanclean clays. The first erosional phase is referred to the intra-Messinian tectonic phase and is analogous to that found in Sicily. The second phase corresponds to the Messinian Erosional Surface that postdates the marginal evaporites, to which the entire Sicilian evaporitic series must refer. The Western and Eastern Mediterranean basins were separated during deposition of the central evaporites. 相似文献
16.
Identification of extreme events using drought indices and their impact on the Danube lower basin discharge 
下载免费PDF全文
下载免费PDF全文 In this study extreme droughts and extremely wet periods in the Danube upper and middle basin (DUMB) have been highlighted with specific indices. The most widely used indices have been considered to estimate both the dry and wet phenomena severity and the frequency or spatio‐temporal extension. The climatic condition of 15 meteorological stations situated in the Danube basin has been evaluated using four indices: Palmer Drought Severity Index (PDSI), Palmer Hydrological Drought Index (PHDI), Weighted PDSI (WPLM) and Palmer Z‐index (ZIND). The four indices have been analysed separately for each of the four seasons between 1901 and 2000. First the internal structure of the time series of the four indices has been analysed separately. Then the overall temporal characteristic has been analysed by means of the principal component of the Multivariate Empirical Orthogonal Functions decomposition of the four indices (PC1‐MEOF). For the discharge in the Danube lower basin, station Orsova has been chosen, representing an integrator of the discharges from the DUMB. A very close connection has been found between Palmer indices and Danube discharge in all seasons (with correlation coefficients greater then 0.80) excepting the spring season. A classification in five classes of both the four indices separately and the PC1‐MEOF has been achieved in order to highlight extreme events. The impact of phenomena quantified by Palmer indices in DUMB upon discharges in Danube lower basin is evident. It was demonstrated in this study that the Greenland‐Balkan Oscillation (GBO) influences the south‐east European hydro‐climatic regime more than the North Atlantic Oscillation (NAO) Index. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
17.
Mihaela Constantin Aurelian C. Trandafir Marta C. Jurchescu Daniel Ciupitu 《Environmental Earth Sciences》2010,59(7):1569-1578
The May–August 2005 heavy rainstorm events in Romania triggered a large number of geomorphic hazards of great magnitude, consisting
of primarily floods and landslides. Some of the most affected regions were the Curvature Carpathians and Subcarpathians. This
paper addresses the effects of rainfall on slopes, especially in the middle sector of the Sibiciu basin (the Buzău Carpathians)
outlining the significant landslide damage along the road connecting the Colţi and Aluniş villages. The landslides are analyzed
in terms of geologic, geomorphic and engineering geologic features, focusing on the Colţi–Aluniş landslide which had the greatest
impact on the road displacement. The related environmental and social impacts are also discussed. 相似文献
18.
Mihaela I. Chidean Antonio J. Caama&#;o Carlos Casanova-Mateo Julio Ramiro-Bargue&#;o Sancho Salcedo-Sanz 《Theoretical and Applied Climatology》2020,140(3):927-949
The authors present a novel self-organized climate regionalization (CR) method that obtains a spatial clustering of regions, based on the explained variance of physical measurements in their coverage. This method enables a microscopic characterization of the probabilistic spatial extent of climate regions, using the statistics of the obtained clusters. It also allows for the study of the macroscopic behaviour of climate regions through time by using the dissimilarity among different cluster size probability histograms. The main advantages of the presented method, based on the Second-Order Data-Coupled Clustering (SODCC) algorithm, are that SODCC is robust to the selection of tunable parameters and that it does not require a regular or homogeneous grid to be applied. Moreover, the SODCC method has higher spatial resolution, lower computational complexity, and allows for a more direct physical interpretation of the outputs than other existing CR methods, such as Empirical Orthogonal Function (EOF) or Rotated Empirical Orthogonal Function (REOF). These facts are illustrated with an example of winter wind speed regionalization in the Iberian Peninsula through the period (1979 − 2014). This study also reveals that the North Atlantic Oscillation (NAO) has a high influence over the wind distribution in the Iberian Peninsula in a subset of years in the considered period. 相似文献
19.
Landslide susceptibility assessment using the bivariate statistical analysis and the index of entropy in the Sibiciu Basin (Romania) 总被引：13，自引：6，他引：7
Mihaela Constantin Martin Bednarik Marta C. Jurchescu Marius Vlaicu 《Environmental Earth Sciences》2011,63(2):397-406
The Sibiciu Basin is located in Romania between the Buzău Mountains and the Buzau Subcarpathians (Curvature Carpathians and
Subcarpathians). The geology of the basin consists of Paleogene flysch deposits represented by an alternation of sandstones,
marls, clays and schists and Neogene deposits represented by marls, clays and sands. The area is affected by different types
of landslides (shallow, medium-deep and deep-seated failures). In Romania, in the last decades, direct and indirect methods
have been applied for landslide susceptibility assessment. The most utilized before 2000 were based on qualitative approaches.
This study evaluates the landslide susceptibility in the Sibiciu Basin using a bivariate statistical analysis and an index
of entropy. A landslide inventory map was prepared, and a susceptibility estimate was assessed based on the following parameters
which influence the landslide occurrence: slope angle, slope aspect, curvature, lithology and land use. The landslide susceptibility
map was divided into five classes showing very low to very high landslide susceptibility areas. 相似文献
20.
Mihaela Trelea‐Newton Nicholas R. Golledge 《Boreas: An International Journal of Quaternary Research》2012,41(4):614-628
Geomorphological mapping of locally nourished glaciers was conducted in four glens in the southeastern Monadhliath Mountains, Scotland. Three glaciers are interpreted to be of Younger Dryas age based on geomorphological similarity to features in other Scottish upland areas known to have been glaciated during the Younger Dryas, and on comparison to adjacent ice‐free areas in the lower glens where landform‐sediment assemblages typically reflect peri/paraglacial readjustment during the stadial. Here we reconstruct Younger Dryas glacier termini based on moraine alignments and associated geomorphological and sedimentological evidence. An adjacent wide plateau area at high altitude may have permitted extensive ice accumulation, but no unequivocal geomorphological signature is evident. To establish upper glacier limits, a series of ice profiles are modelled. The results yield a range of realistic glacier configurations bracketed between two distinct scenarios: a valley glaciation with the glaciers' upper limit on the plateau edge, and a low‐domed icecap centred on the plateau with ice flowing radially into the lower glens. Reconstructed equilibrium‐line altitudes are 795 m a.s.l. for the valley‐glacier scenario and 894 m a.s.l. for the icecap scenario. Calculated mean ablation‐season temperatures at the ELA are 1.2°C and 0.4°C for the valley‐glacier and the icecap scenario, respectively, from which we infer mean annual precipitation rates between 323 and 520 mm a?1. Palaeoclimate results indicate a stadial climate in central Scotland 65–79% more arid than at present, comparable to that of western Norway for the stadial and to the present‐day Canadian Arctic. 相似文献