排序方式： 共有135条查询结果，搜索用时 17 毫秒
71.
Andrea Loprieno Romain Bousquet Stefan Bucher Stefano Ceriani Florian H. Dalla Torre Bernhard Fügenschuh Stefan M. Schmid 《International Journal of Earth Sciences》2011,100(5):963-992
The Valais units in Savoy (Zone des Brèches de Tarentaise) have been re-mapped in great detail and are subject of combined stratigraphic, structural and petrological investigations summarized in this contribution. The sediments and rare relics of basement, together with Cretaceous age mafic and ultramafic rocks of the Valais palaeogeographical domain, represent the heavily deformed relics of the former distal European margin (External Valais units) and an ocean–continent transition (Internal Valais unit or Versoyen unit) that formed during rifting. This rifting led to the opening of the Valais ocean, a northern branch of the Alpine Tethys. Post-rift sediments referred to as “Valais trilogy” stratigraphically overlie both External and Internal Valais successions above an angular unconformity formed in Barremian to Aptian times, providing robust evidence for the timing of the opening of the Valais ocean. The Valais units in Savoy are part of a second and more external mid-Eocene high-pressure belt in the Alps that sutured the Briançonnais microcontinent to Europe. Top-N D1-deformation led to the formation of a nappe stack that emplaced the largely eclogite-facies Internal Valais unit (Versoyen) onto blueschist-facies External Valais units. The latter originally consisted of, from internal to external, the Petit St. Bernard unit, the Roc de l’Enfer unit, the Moûtiers unit and the Quermoz unit. Ongoing top-N D2-thrusting and folding substantially modified this nappe stack. Post 35 Ma D3 folding led to relatively minor modifications of the nappe stack within the Valais units but was associated with substantial top-WNW thrusting of the Valais units over the Dauphinois units along the Roselend thrust during W-directed indentation of the Adria block contributing to the formation of the arc of the Western Alps. 相似文献
72.
Since the 1970s, protected area networks in mainland Southeast Asian countries have developed significantly to occupy 4–25 per cent of their respective national areas, located mostly in the mountainous domains of ethnic minority peoples. Through this process, regions that were only nominally part of national geobodies until the 1950s have become more territorially integrated. The complexity of the characteristics and geographical impacts of this territorialisation have yet to be grasped. As a step in this direction, we briefly outline a multilevel systems approach that usefully contextualizes these issues together with a historical and cartographical assessment of the evolution of protected area networks for Burma, Thailand, Laos, Cambodia and Vietnam. Our main findings are intertwined. On the one hand, protected areas represent a new tool of state intervention in mountainous areas, clearly in keeping with past, notably colonial, actions. On the other hand, this evolution in state territorialisation and attendant power relations have disrupted, far more deeply than previous actions, the pre‐1970s sociogeographical organization in mountainous areas, where most of the region's residual forests remain. 相似文献
73.
Pascale Huyghe Romain Guilbaud Matthias Bernet Albert Galy Ananta Prasad Gajurel 《Basin Research》2011,23(3):332-345
Clay mineral assemblages of the Neogene Himalayan foreland basin are studied to decipher their significance with respect to tectonic and climate processes. Fluvial deposits of the Siwalik Group (west‐central Nepal), and sediment of the Ganga River drainage system were analysed for clay mineralogy. The observed clay mineral assemblages are mainly composed of illite (dominant), chlorite, smectite and kaolinite. Illite and chlorite are chiefly of detrital origin, derived from Himalayan sources. Kaolinite and smectite are authigenic, and mainly developed within pore space and as coating of detrital particles. With increasing burial, diagenetic processes affected the original clay mineral signature. Illitisation of smectite and kaolinite occurred below 2500 and 3500 m depth, respectively. Therefore, illite in the lower parts of the Siwalik Group consists of a mixture of inherited illite and illitised smectite and kaolinite, as suggested by illite crystallinity. Detrital grains that make up the framework of the Siwalik Group sandstones mainly consist of quartz, feldspar and lithic fragments, which are principally of sedimentary and metamorphic origin. Lithoclast content increases over time at the expense of quartz and K‐feldspar in response to uplift and erosion of the Lesser Himalaya Series since about 11–10 Ma. Despite mainly felsic source rocks, dominantly physical erosion processes in the Himalayan belt, and high‐energy fluvial depositional systems, smectite is abundant in the <7 Ma Siwalik Group deposits. Analyses of the Siwalik deposits and comparison with the clay mineralogy of the modern drainage system suggest that smectite preferentially formed in floodplains and intermontane valleys during early diagenesis because of downward percolating fluids rich in cations from weathering and soil development. In general, increasing seasonality and aridity linked to variability of the Asian monsoon from about 8 Ma enhanced clay mineral formation and development of authigenic smectite in paleo‐plains on the southern side of the Himalaya. 相似文献
74.
Fundamental differences between SPH and grid methods 总被引：1，自引：0，他引：1
Oscar Agertz Ben Moore Joachim Stadel Doug Potter Francesco Miniati Justin Read Lucio Mayer Artur Gawryszczak rey Kravtsov Åke Nordlund Frazer Pearce Vicent Quilis Douglas Rudd Volker Springel James Stone Elizabeth Tasker Romain Teyssier James Wadsley Rolf Walder 《Monthly notices of the Royal Astronomical Society》2007,380(3):963-978
75.
Romain Chesnaux 《水文科学杂志》2013,58(2):421-436
Abstract Estimates of trends of climatic changes at basin and state scales are required for developing adaptation strategies related to planning, development and management of water resources. In the present study, seasonal and annual trends of changes in maximum temperature (T max), minimum temperature (T min), mean temperature (T mean), temperature range (T range), highest maximum temperature (H max) and lowest minimum temperature (L min) have been examined at the basin scale. The longest available records over the last century, for 43 stations covering nine river basins in northwest and central India, were used in the analysis. Of the nine river basins studied, seven showed a warming trend, whereas two showed a cooling trend. The Narmada and Sabarmati river basins experienced the maximum warming and cooling, respectively. The majority of basins in the study area show increasing trend in T range, H max and L min. Seasonal analysis of different variables shows that the greatest changes in T max and T mean were observed in the post-monsoon season, while T min experienced the greatest change in the monsoon season. This analysis provides scenarios of temperature changes which may be used for sensitivity analysis of water availability for different basins, and accordingly in planning and implementation of adaptation strategies. 相似文献
76.
Térence Desclaux Hugues Lemonnier Pierre Genthon Benoit Soulard Romain Le Gendre 《水文科学杂志》2013,58(11):1689-1706
ABSTRACTThe GR4H lumped hourly rainfall–runoff model was assessed for its integration in a ridge-to-reef modelling framework. Particular attention was paid to rainfall representation, robustness of parameter estimates and ability to reproduce the main runoff features. The study was conducted in four tropical mountainous watersheds in New Caledonia, which are exposed to intense rainfall events, large annual climatic variations triggered by El Niño oscillation, and wildfires. The inverse distance and elevation weighting algorithm outperformed other classical rainfall interpolation methods under data-limited conditions. The time span of data needed for robust calibration was site specific and varied from 6–7 years to 10 years, which may be linked to El Niño events and to wildfires. With sufficient data, simulation quality was equivalent during the calibration and validation periods. The GR4H model was generally able to simulate both flash floods and large annual variations. The model was more reliable when simulating wet years and watersheds not subject to land-cover changes. 相似文献
77.
褶皱逆冲带的几何学研究是造山带研究的热点,但是无论是传统构造地质学方法还是地球物理学方法都在研究褶皱逆冲带几何特征时存在多解性.为了制约这种多解性,本文以天山北麓的呼图壁河剖面为列,介绍一种地质与地球物理相结合的研究方法.该方法首先沿呼图壁河剖面进行详细的地表观测,获取地表的构造地质数据形成初步的地质模型,其次结合地表构造和钻井分层数据,对收集到的石油地震剖面进行重新解释.然而,地震反射数据只分布在盆地内部,在盆山结合带缺失或者不清晰,因此对该剖面进行了重力测量并计算出布格重力异常.结合盆地各沉积地层和基底密度值,用重力正演方法模拟呼图壁河剖面的密度结构.研究结果显示沿呼图壁河剖面并不存在天山北缘断裂,盆地的沉积盖层可以从准噶尔盆地连续过度到天山内部并不整合覆盖在天山古生代基底之上.这一结果与西段金钩河剖面的天山基底逆冲到准噶尔盆地显然不同,说明了天山北缘盆山结合带构造的多样性.利用平衡剖面技术,恢复的呼图壁河平衡剖面缩短量约为4.8 km,对比前人研究,说明了天山北缘的缩短量沿东西方向存在显著的不均一性.本研究也说明这种构造地质与地震及非震地球物理相结合的方法可以广泛地被应用于褶皱逆冲带. 相似文献
78.
Poujol Marc Pitra Pavel Van Den Driessche Jean Tartèse Romain Ruffet Gilles Paquette Jean-Louis Poilvet Jean-Charles 《International Journal of Earth Sciences》2017,106(2):477-500
International Journal of Earth Sciences - One of the striking features that characterise the late stages of the Variscan orogeny is the development of gneiss and migmatite domes, as well as... 相似文献
79.
Christophe Lcuyer Franois Fourel Magali Seris Romain Amiot Jean Goedert Laurent Simon 《Geostandards and Geoanalytical Research》2019,43(4):681-688
The large range of stable oxygen isotope values of phosphate‐bearing minerals and dissolved phosphate of inorganic or organic origin requires the availability of in‐house produced calibrated silver phosphate of which isotopic ratios must closely bracket those of studied samples. We propose a simple protocol to synthesise Ag3PO4 in a wide range of oxygen isotope compositions based on the equilibrium isotopic fractionation factor and the kinetics and temperature of isotopic exchange in the phosphate–water system. Ag3PO4 crystals were obtained from KH2PO4 that was dissolved in water of known oxygen isotope composition. Isotopic exchange between dissolved phosphate and water took place at a desired and constant temperature into PYREX? tubes that were placed in a high precision oven for defined run‐times. Samples were withdrawn at desired times, quenched in cold water and precipitated as Ag3PO4. We provide a calculation sheet that computes the δ18O of precipitated Ag3PO4 as a function of time, temperature and δ18O of both reactants KH2PO4 and H2O at t = 0. Predicted oxygen isotope compositions of synthesised silver phosphate range from ?7 to +31‰ VSMOW for a temperature range comprised between 110 and 130 °C and a range of water δ18O from ?20 to +15‰ VSMOW. 相似文献
80.
Guillermo Booth-Rea José Miguel Azañón Vı́ctor Garcı́a-Dueñas Romain Augier 《Comptes Rendus Geoscience》2003,335(9):751-761
The Palomares Fault Zone (PFZ) is one of the main strike-slip brittle shear zones found in the Betics. It is segmented in several faults that have been active between the Upper Tortonian and present day. Data from drill cores in the Palomares area have permitted us to define the geometry and location of sedimentary depocentres related with the PFZ. These data show an eastward displacement between the Upper Tortonian to Messinian and the Pliocene–Quaternary sedimentary depocentres, towards the presently active Arteal fault, which bounds the western mountain front of Sierra Almagrera, showing that deformation along this fault zone has migrated towards the east, from the Palomares segment, with its main activity during the Upper Tortonian and Messinian, towards the Arteal fault, active during the Pliocene and Quaternary. To cite this article: G. Booth-Rea et al., C. R. Geoscience 335 (2003). 相似文献