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901.
902.
Ivana Conceição de Araújo Pinho Johildo Salomão Figueiredo Barbosa Angela Beatriz de Menezes Leal Hervé Martin Jean-Jacques Peucat 《Journal of South American Earth Sciences》2011,31(2-3):312-323
The studied tonalitic and trondhjemitic granulites are located in the SSE granulitic domain of the São Francisco craton, Bahia, Brazil, where they represent most of the southern part of the Archean and Paleoproterozoic Itabuna-Salvador-Curaçá Block (ISCB). Chemically, the tonalitic and trondhjemitic granulites belong to a low-K calc-alkaline suite; their REE patterns are steep with strong LREE/HREE fractionation and no significant Eu anomaly. Garnet-bearing mafic granulites that occur as enclaves in the tonalitic and trondhjemitic granulites were derived from basalts and/or gabbros of tholeiitic affinity. Geochemical modelling showed that the tonalitic and trondhjemitic granulites were produced by moderate fractional crystallization of an assemblage of hornblende and plagioclase, with subordinate amounts of magnetite, apatite, allanite and zircon. The garnet-bearing mafic granulites would be the source of the magmas that generated these rocks. Partial melting left a residue made up of plagioclase, garnet, orthopyroxene and hornblende. 相似文献
903.
Ryan D. Stewart Majdi R. Abou Najm David E. Rupp John W. Lane Hamil C. Uribe José Luis Arumí John S. Selker 《水文研究》2015,29(4):557-571
Irrigation experiments on 12 instrumented field plots were used to assess the impact of dynamic soil crack networks on infiltration and run‐off. During applications of intensity similar to a heavy rainstorm, water was seen being preferentially delivered within the soil profile. However, run‐off was not observed until soil water content of the profile reached field capacity, and the apertures of surface‐connected cracks had closed >60%. Electrical resistivity measurements suggested that subsurface cracks persisted and enhanced lateral transport, even in wet conditions. Likewise, single‐ring infiltration measurements taken before and after irrigation indicated that infiltration remained an important component of the water budget at high soil water content values, despite apparent surface sealing. Overall, although the wetting and sealing of the soil profile showed considerable complexity, an emergent property at the hillslope scale was observed: all of the plots demonstrated a strikingly similar threshold run‐off response to the cumulative precipitation amount. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
904.
Juliana Alcântara Costa Joaquín Navarro-Hevia Carlos Alexandre Gomes Costa José Carlos de Araújo 《水文研究》2021,35(3):e14070
Evapotranspiration (ET) plays an important role in integrated water resource planning, development and management. This process is particularly relevant in semiarid regions. The aim of this study is, hence, to compare spatial and temporal patterns of actual ET, as well as the temporal trends in two different semiarid forests, Caatinga (Brazil) and Tierra de Pinares (Spain). We used the surface energy balance algorithm for land (SEBAL) to assess actual evapotranspiration (ETa) in both areas. In the Brazilian semiarid forest, Caatinga is the main vegetation, while it is Pinares in Spain. For this purpose, 69 Landsat-5 and 42 Landsat-8 images (1995–2019) were used. The Mann–Kendall test was applied to assess the occurrence of trends in precipitation, temperature and potential ET data; and the Temporal Stability Index (TSI) to know which areas have greater seasonal ETa. The annual amplitude of the potential evapotranspiration (ET0) is the same in both areas, however, the Caatinga values are higher. In the Caatinga forest, when ET0 presents its highest values throughout the year, ETa presents the lowest, and vice versa. In the Pinares forest, ETa follows the ET0 dynamics during the year, and the difference between ET0 and ETa is maximum during the summer. The Caatinga forest showed a greater spatial variation of ETa than the Pinares forest as well as a greater extension with lower temporal stability of ETa than the Pinares forest. Both the Caatinga forest and the Pinares forest showed significant positive trends in annual ET0 and ETa. We estimate that the value of ETa increases more rapidly in Pinares than in the Brazilian Caatinga. Taking Caatinga as a hydrological mirror, some consequences are expected to Pinares, such as significant changes in the water balance, increase of biodiversity vulnerability, and reduction of water availability in soil and reservoirs. 相似文献
905.
906.
Anderson José Maraschin Ana Maria Mizusaki Horst Zwingmann André Weissheimer de Borba Gesiane Fraga Sbrissa 《Journal of South American Earth Sciences》2010,29(2):400-411
Several analytical studies performed on alluvial-eolian sandstones of the Early Paleozoic Guaritas Allogroup (Camaquã Basin, southern Brazil) indicate illite to be abundant, showing different morphologies as authigenic grain rims and pore-bridging filaments. Authigenic illite separates of variable grain sizes from distinct stratigraphic intervals of the Guaritas Allogroup yielded 40K–40Ar ages from 521.7 ± 10.3 to 473.7 ± 9.4 Ma. These ages, interpreted to record the timing of illite authigenesis, are coincident with the age of emplacement of the Rodeio Velho andesites (470 ± 19 Ma). Moreover, field structures suggest interaction between hot, andesite lava flows and wet, poorly consolidated sediments of the Pedra Pintada Alloformation (lower strata of the Guaritas Allogroup). This set of data indicates that the Rodeio Velho volcanism could have been responsible for a widespread remobilization of interstitial fluids and consequent authigenic illite precipitation in the sandstones of the Guaritas Allogroup. 相似文献
907.
Multi‐scale assessment of overflow‐driven lateral connectivity in floodplain and backwater channels using LiDAR imagery
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Overflow‐driven lateral connectivity significantly influences the spatial distribution and diversity of floodplain habitats and biota. Proper understanding of lateral connectivity in floodplain and backwater channels is therefore critical for assessment of river quality and for targeting management or restoration actions. In this study, we present a methodological framework for spatial and temporal assessments of overflow‐driven lateral connectivity at two spatial scales: bypass reach and backwater channel. Firstly, we compute the relative elevations, as well as overflow discharge, duration, and frequency using a simple, raster‐based method that uses a LiDAR digital elevation model (DEM), rating curves, and streamflow time series. Subsequently, we analyse the accuracy of this approach with respect to the accuracy of a DEM and evaluate its further applications. Altogether, four 10‐km‐long bypass reaches and 11 backwater channels are analysed, located along the Rhône River corridor in France. The results proved the precision of the method to be affected by the LiDAR DEM accuracy, which was on average more precise in a typically homogeneous floodplain setting rather than for backwater channel plugs with pronounced topographic complexity and usually riparian forest canopy. Amongst the four studied reaches, Brégnier Cordon proved to have the greatest flooding dynamics, followed by Belley and Chautagne. The hydrological connectivity pattern of Pierre Bénite differed significantly. Three longitudinal patterns of hydrological connectivity of backwater channels displayed stepwise advancement of the water. The presented results can be used to assess ecological potential of floodplain habitats and their historic and prospective evolution through time. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
908.
Jorge Alonso‐Henar Walter Montero José J. Martínez‐Díaz José A. Álvarez‐Gómez Juan M. Insua‐Arévalo Wilfredo Rojas 《地学学报》2013,25(5):368-373
On 4 May 1910, the most destructive earthquake in the history of Costa Rica (Ms 6.4) destroyed the city of Cartago, a major city located in the Valle Central of Costa Rica. Using both palaeo‐seismological and morphotectonic analyses, we have found evidence that points to the Aguacaliente Fault (AF) as the source of this earthquake. This structure is a N100° E trending, strike‐slip fault situated to the south of Cartago and within a wide band of deformation. We excavated two trenches near Bermejo, south of Cartago. We found evidence of three surface ruptures within the last 1000 years on this fault. The age of the most recent rupture is consistent with the Cartago 1910 earthquake. The AF is a seismogenic source capable of producing large earthquakes (Mw 6.5–6.9) with an estimated recurrence interval of about 500 years. 相似文献
909.
Sedimentation in the floodplains of the Mekong Delta,Vietnam Part II: deposition and erosion
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Nguyen Nghia Hung José Miguel Delgado Andreas Güntner Bruno Merz András Bárdossy Heiko Apel 《水文研究》2014,28(7):3145-3160
Deposition and erosion play a key role in the determination of the sediment budget of a river basin, as well as for floodplain sedimentation. Floodplain sedimentation, in turn, is a relevant factor for the design of flood protection measures, productivity of agro‐ecosystems, and for ecological rehabilitation plans. In the Mekong Delta, erosion and deposition are important factors for geomorphological processes like the compensation of deltaic subsidence as well as for agricultural productivity. Floodplain deposition is also counteracting the increasing climate change induced hazard by sea level rise in the delta. Despite this importance, a sediment database of the Mekong Delta is lacking, and the knowledge about erosion and deposition processes is limited. In the Vietnamese part of the Delta, the annually flooded natural floodplains have been replaced by a dense system of channels, dikes, paddy fields, and aquaculture ponds, resulting in floodplain compartments protected by ring dikes. The agricultural productivity depends on the sediment and associated nutrient input to the floodplains by the annual floods. However, no quantitative information regarding their sediment trapping efficiency has been reported yet. The present study investigates deposition and erosion based on intensive field measurements in three consecutive years (2008, 2009, and 2010). Optical backscatter sensors are used in combination with sediment traps for interpreting deposition and erosion processes in different locations. In our study area, the mean calculated deposition rate is 6.86 kg/m2 (≈ 6 mm/year). The key parameters for calculating erosion and deposition are estimated, i.e. the critical bed shear stress for deposition and erosion and the surface constant erosion rate. The bulk of the floodplain sediment deposition is found to occur during the initial stage of floodplain inundation. This finding has direct implications on the operation of sluice gates in order to optimize sediment input and distribution in the floodplains. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
910.
Christina Ifrim Wolfgang Stinnesbeck Rufino Rodríguez Garza José Flores Ventura 《Journal of South American Earth Sciences》2010,29(3):597-618
Few biostratigraphic data exist from the Parras and La Popa basins, mainly due to the absence of index fossils. This paper describes 19 ammonoid species from 15 genera and 1 nautilid from La Parra, southeastern Coahuila, Mexico. The assemblage consists of Tethyan [(Baculites ovatus, Brahmaites (Anabrahmaites) vishnu, Fresvillia constricta, Hauericeras rembda, Pachydiscus (P.) ex gr. neubergicus, Solenoceras reesidei, Tetragonites cf. superstes], cosmopolitan (Anagaudryceras politissimum, Desmophyllites diphylloides, Diplomoceras cylindraceum, Gaudryceras kayei, Phyllopachyceras forbesianum, Pseudophyllites indra), and cold water taxa [Fresvillia teres, Hypophylloceras (Neophylloceras) surya, H. (N.) hetonaiense, Pachydiscus (P.) cf. egertoni]. Eutrephoceras sp. and Menuites juv. sp. were not determined to species level. A similar assemblage was recently described from the coeval Méndez Formation at Cerralvo, Nuevo León. Species endemic to North America, particularly the Western Interior Seaway, are absent at La Parra. The ammonoid assemblage and associated planktonic foraminifers allow for precise biostratigraphic assignation to the early Maastrichtian planktonic foraminiferal zone CF 5, and thus provide an important marker level for correlation of the lower Difunta Group. The new biostratigraphic data presented herein allow for the first time precise dating of the Cañon del Tule Formation of the Difunta Group. Their combination with existing sequence- and magnetostratigraphic data improve the correlation of the lower Difunta Group with time-equivalent lithostratigraphic units such as the Cárdenas Formation in Mexico. They also provide new insight into ammonoid migration patterns induced by sea-level changes. Baculites ovatus migrated into the La Popa Basin as a result of the sea-level highstand documented at La Parra. 相似文献