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141.
Leonardo M. Pichel Alex F. Antunes Haakon Fossen Barbara F. Rapozo Emma Finch Valeria C. Córdoba 《Basin Research》2023,35(1):61-85
The Rio do Peixe Basin is part of a series of aborted Cretaceous rifts formed within the Proterozoic Borborema Province, onshore NE Brazil in response to rifting between Africa and South America. The basin is remarkably well-imaged and comprises fault-bounded depocentres, the main ones being the NE-oriented Brejo das Freiras and the E–W-oriented Sousa half-grabens. These grabens and their bounding faults are influenced by Neoproterozoic basement shear zones and present a complex framework of secondary normal faults and folds. Recent workers also interpret large reverse faults and regional post-rift shortening driven by far-field stresses from the Andes. For those reasons, the basin represents an ideal setting to investigate the multiphase history of rift basins. We thus combine borehole-calibrated 2D and 3D seismic and magnetic data with section restoration and numerical modelling to investigate the architecture and evolution of this basin. We aim to understand: (i) the controls of the basement fabric in 3D fault architecture and kinematics and (ii) how syn-rift faults controlled the geometry and development of fault-related folds. By doing this, we also investigate the timing, kinematics, and magnitude of inversion in the basin to explore its multiphase history. We demonstrate that (i) the basement fabric controlled not only the strike of faults but also their geometry and polarity at depth, (ii) folds in the syn-rift sequence are attributed simply to syn-rift extension along stepped and/or curved faults, and (iii) inverted and/or reverse faults occur within the basin, but these are minor and appear to have formed during rifting. We explain this minor inversion by a change in plate kinematics related to the onset of the nearby transform margin to the north. These results have implications for understanding the 3D evolution of oblique grabens, the role of structural inheritance, and the recognition of inversion- versus extension-related folds in rift basins worldwide. 相似文献
142.
Abstract The annual water balance of Lake Kyoga is estimated by a comparison of upstream and downstream flows in the Nile channel during a period of reliable measurements (1940–1977), supported by rainfall records over the basin. The relative contributions of net lake rainfall and tributary inflows are estimated. Changes in annual rainfall and seasonal distribution are examined. Editor Z.W. Kundzewicz Citation Brown, E. and Sutcliffe, J.V., 2013. The water balance of Lake Kyoga, Uganda. Hydrological Sciences Journal, 58 (2), 342–353. 相似文献
143.
Emma S. BULLOCK Glenn J. MacPHERSON Kazuhide NAGASHIMA Alexander N. KROT Michail I. PETAEV Stein B. JACOBSEN Alexander A. ULYANOV 《Meteoritics & planetary science》2012,47(12):2128-2147
Abstract– Detailed petrologic and oxygen isotopic analysis of six forsterite‐bearing Type B calcium‐aluminum‐rich inclusions (FoBs) from CV3 chondrites indicates that they formed by varying degrees of melting of primitive precursor material that resembled amoeboid olivine aggregates. A continuous evolutionary sequence exists between those objects that experienced only slight partial melting or sintering through objects that underwent prolonged melting episodes. In most cases, melting was accompanied by surface evaporative loss of magnesium and silicon. This loss resulted in outer margins that are very different in composition from the cores, so much so that in some cases, the mantles contain mineral assemblages that are petrologically incompatible with those in the cores. The precursor objects for these FoBs had a range of bulk compositions and must therefore have formed under varying conditions if they condensed from a solar composition gas. Five of the six objects show small degrees of mass‐dependent oxygen isotopic fractionation in pyroxene, spinel, and olivine, consistent with the inferred melt evaporation, but there are no consistent differences among the three phases. Forsterite, spinel, and pyroxene are 16O‐rich with Δ17O ~ ?24‰ in all FoBs. Melilite and anorthite show a range of Δ17O from ?17‰ to ?1‰. 相似文献
144.
Stéphane Audry Henriette Ateba Bessa Jean-Pierre Bedimo Bedimo Jean-Loup Boeglin Laurie Boithias Jean-Jacques Braun Bernard Dupré Mikael Faucheux Christelle Lagane Jean-Christophe Maréchal Jules Remy Ndam-Ngoupayou Bernadette Nka Nnomo Justin Nlozoa Jean-Claude Ntonga Olivier Ribolzi Jean Riotte Emma Rochelle-Newall Laurent Ruiz 《水文研究》2021,35(5):e14138
Simultaneously acquiring time series of climate, hydrology and hydrochemical data over decades on river systems is pivotal to understand the complex interactions involving rock, soil water, air and biota in the Critical Zone, to build integrated modelling and to propose predictive scenarios. Among the Critical Zone Observatories (CZOs) implemented in the past 25 years, only a few are located in the humid Tropics despite the importance of these regions in terms of population density, fast-changing land use, biodiversity hotspots, biomass stock on continents, size of river systems, etc. Since 1994, weathering and erosion processes and fluxes have been investigated at both local (experimental watershed) and regional scales in the Nyong River Basin (Cameroon) which belongs to the Critical Zone Observatories network named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Cameroon are: (1) rainfall; (2) air temperature, air relative humidity, wind speed and direction, and global radiation; (3) stream and river water level; (4) pH, electrical conductivity, water temperature and suspended particulate matter (SPM) concentration; (5) major ion, alkalinity and dissolved organic carbon (DOC) concentrations. The dataset already contributed to describe the water partitioning in these tropical humid watersheds, to better understand the factors controlling chemical weathering and physical erosion in tropical ecosystems, particularly the role of organic matter. The dataset also contributed to calculate elemental weathering fluxes and saprolite production rate and to propose denudation rates on tropical cratonic landscapes. Hydrological modelling allowed quantification of the geographical water sources contributing to streamflow. DOC data were used to determine greenhouse-gas emissions and carbon budgets from African inland waters. However, long-term solute concentrations at the outlet of a small tributary of the Nyong River exhibit non-stationary behaviour over the last 26 years. The processes governing those fluctuations are not yet fully understood and might be related to changes in the hydrological regime, land-cover and land-use. The latter highlights the need for longer time-series and continued support for CZOs particularly in the humid tropics. 相似文献
145.
Navarro P Amouroux D Thanh ND Rochelle-Newall E Ouillon S Arfi R Van TC Mari X Torréton JP 《Marine pollution bulletin》2012,64(9):1789-1798
In this work, two field campaigns were performed in July 2008 (wet season) and March 2009 (dry season) to produce original data on the concentration, partition and distribution of mercury and butyltin compounds along the tropical Bach Dang Estuary located in North Vietnam (Haiphong, Red River Delta). The results demonstrate that mercury and butyltin speciation in the surface waters of this type of tropical estuary is greatly affected by the drastic changes in the seasonal conditions. During high river discharge in the wet season, there was a large estuarine input of total Hg and tributyltin, while the longer residence time of the waters during the dry season promotes increasing MMHg formation and TBT degradation. Although most of the Hg and TBT is transported into the estuary from upstream sources, tidal cycle measurements demonstrate that this estuary is a significant source of TBT and MMHg during the wet (~3kgTBT/day) and dry (~3gMMHg/day) seasons. 相似文献
146.
147.
In this paper, we focus on strength properties of double porous materials having a Drucker-Prager solid phase at microscale. The porosity consists in two populations of micropores and mesopores saturated with different pressures. To this end, we consider a hollow sphere subjected to a uniform strain rate boundary conditions. For the microscale to mesoscale transition, we take advantage of available results by Maghous et al. (2009), while the meso to macro upscaling is performed by implementing a kinematical limit analysis approach using Eshelby-like trial velocity fields. This two-step homogenization procedure delivers analytical expression of the macroscopic criterion for the considered class of saturated double porous media. This generalizes and improves previous results established by Shen et al. (2014). The results are discussed in terms of the existence or not of effective stresses. Some illustrations are provided. 相似文献
148.
大别造山带北缘后碰撞富钾火山岩:地球化学与岩石成因 总被引:12,自引:10,他引:12
大别造山带北缘晚中生代富钾火山岩分布在磨子潭-晓天断裂以北的上叠式火山盆地中,主要为一套以钾玄岩-粗安岩-安粗岩-粗面岩为主体的中偏碱性岩石组合,晚期出现少量碱性火山岩。化学成分上具有富碱、富钾、贫钛、氧化系数较高等特点。岩石的Rb、Ba、Th、Pb等大离子亲石元素含量高,富轻稀土,La/Nb、Ba/Nb及LREE/HREE比值高,并且有显著的Nb、Ti负异常和Pb正异常,而铕异常则不明显。富钾火山岩的Isr值较高(=0.70872-0.70895),εNd(t)值显著偏低(=-14.62--18.51)。根据对岩石产出动力地质背景及地球化学特征的综合分析,结合同位素组成的混合模拟,表明本区富钾火山岩最可能起源于受俯冲陆壳析出流体交代作用所形成的富集地幔(EM I)的部分熔融。 相似文献
149.
Emma Rigby, Melissa Symonds and Derek Ward-Thompson review the evidence for the possibility that a comet may have impacted the Earth in historical times, and discuss the size of the putative comet. 相似文献
150.