A micromorphological record of contemporary and relict pedogenic processes in soils of the Indo‐Gangetic Plains: implications for mineral weathering,provenance and climatic changes          下载免费PDF全文

Pankaj Srivastava  Manini Aruche  Ajay Arya  Dilip K. Pal  Lalan P. Singh 《地球表面变化过程与地形》2016,41(6):771-790

Micromorphology has important application in earth surface process and landform studies particularly in alluvial settings such as the Indo‐Gangetic Plains (IGP) with different geomorphic surfaces to identify climatic changes and neotectonic events and their influence on pedogenesis. The soils of the IGP extending from arid upland in the west to per humid deltaic plains in the east developed on five geomorphic surfaces namely QIG1 to QIG5 originating during the last 13.5 ka. Four soil‐geomorphic systems across the entire IGP are identified as: (i) the western Yamuna Plains/Uplands, (ii) the Yamuna‐Ganga Interfluve, (iii) the Ganga‐Ghaghara Interfluve, and (iv) the Deltaic Plains. Thin section analysis of the soils across the four soil‐geomorphic systems provides a record of provenance, mineral weathering, pedogenic processes and polygenesis in IGP. The soils over major parts of the IGP dominantly contain muscovite and quartz and small fraction of highly altered feldspar derived from the Himalayas. However, soils in the western and eastern parts of the IGP contain large volumes of fresh to weakly altered plagioclase and smectitic clay derived from the Indian craton. The soils in western Yamuna Plains/Uplands dominated by QIG2–QIG3 geomorphic surfaces and pedogenic carbonate developed in semi‐arid climate prior to 5 ka. However, soils of the central part of the IGP in the Yamuna‐Ganga Interfluve and Ganga‐Ghaghara Interfluve regions with dominance of QIG4–QIG5 surfaces are polygenetic due to climate change over the last 13.5 ka. The clay pedofeatures formed during earlier wet phase (13.5–11 ka) show degradation, loss of preferred orientation, speckled appearance in contrast with the later phase of wet climate (6.5–4 ka). The soils over the deltaic plains with dominance of vertic features along with clay pedofeatures suggest that illuviation of fine clay is an important pedogenic process even in soils with shrink‐swell characteristics. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Neutral planetary boundary layer above a nonhomogeneous surface     

S. P. S. Arya 《地球物理与天体物理流体动力学》2013,107(1):333-355

Abstract

Theoretical analyses of the atmospheric boundary layer are generally based on the assumptions of stationarity and horizontal homogeneity, which permit one to neglect the inertial terms in equations of motion. The importance of these terms is examined for the case where slight inhomogeneities may cause small but monotonic changes of surface shear in the direction of flow. Considering several models of the neutral barotropic Ekman layer, it is shown that horizontal gradient in the friction velocity of as small as one cm/sec per ten kilometers could make the wind hodograph deviate significantly from that for the homogeneous case. Significant deviations from the logarithmic profile in the surface layer, on the other hand, would occur for horizontal gradients of at least an order of magnitude greater. Thus, the practical criteria for assuming homogeneity may be far more strict and difficult to satisfy for the outer layer than these are for the surface layer.  相似文献   

Usage of strain and vorticity analyses to interpret large‐scale fold mechanisms along the Sanandaj–Sirjan HP‐LT metamorphic belt,SW Iran     

Khalil Sarkarinejad  Abdolreza Partabian  Ali Faghih  Timothy M. Kusky 《Geological Journal》2012,47(1):99-110

3D finite strain analyses and kinematic vorticity measurements were carried out on the Loghon Anticline within the HP‐LT Sanandaj–Sirjan metamorphic belt (Neyriz area, SW Iran). Rƒ/φ and Fry methods were used on the strain markers (e.g. deformed fossils) to interpret geometric relationships between the fold axis, strain ellipsoid axes and shear zone boundaries. The results indicate the predominance of prolate strain in the anticline. Quantitative kinematic analyses show that the W_k parameter is 0. 67 ± 0. 06 (i.e. pure‐shear dominated non‐coaxial flow). This study quantitatively supports the establishment of a dextral transpressive system, which is responsible for the development of the large‐scale right‐lateral shear zones that strike sub‐parallel to the major folds. Flexural shear combined with regional dextral‐shear is suggested to be the most common mechanism of folding in this area. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Natural carbon nanofibers in graphite     

Tatyana Grygoryevna Shumilova  Sergey Ivanovich Isaenko  Farid Karibovich Divaev  Junji Akai 《Mineralogy and Petrology》2012,104(3-4):155-162

  相似文献   

Tectono-sequence stratigraphy and U–Pb zircon ages of the Rincón Blanco Depocenter,northern Cuyo Rift,Argentina     

Silvia Barredo  Farid Chemale  Claudia Marsicano  Janaína N. Ávila  Eduardo G. Ottone  Victor A. Ramos 《Gondwana Research》2012,21(2-3):624-636

Extensional processes that followed the Gondwanan Orogeny rise to the development of a series of rift basins along the continental margin over older accreted Eopaleozoic terranes. Stratigraphic, structural, paleontological, and isotopic studies are presented in this work in order to constrain the ages of the sedimentary infilling and to analyze the tectosedimentary evolution of one of the Cuyo basin depocenters, known as Rincón Blanco. This asymmetrical half-graben was filled by continental sediments under a strong tectonic control. The infilling was strongly controlled by tectonics which in term produced distinctive features along the whole sedimentary sequence. Using a combination of lithological and structural data the infilling was subdivided into packages of genetically linked units bounded by regional extended surfaces. Several tuffs and acid volcanic rocks have been collected across the whole section of the Rincon Blanco sub-basin for SHRIMP and LA-MC-ICPMS U–Pb zircon dating. The ages obtained range from 246.4 ± 1.1 Ma to 230.3 ± 1.5 Ma which is the time elapsed for the deposition of three tectono-sequence units separated by regional unconformities and mainly constrained to the Middle Triassic. They are interpreted as a result of a reactivation of the extensional system that has evolved along strike as segments of faults that linked together and/or as laterally propagating faults. Regional correlation with coeval rift basins permits to establish north-south propagation in the extensional regime along the western margin of SW Gondwana. This trending started in the lowermost Triassic and extended until the latest Triassic. Two of them were precisely correlated with Cerro Puntudo and Cacheuta half-graben systems. The new data indicate that the three sequences were mostly deposited during the Middle Triassic (246 to 230 Ma), with no evidence of sedimentation during Norian and Rhaetian, which is in conflict with some previous biostratigraphic studies.  相似文献   

Pliocene–Pleistocene stratigraphy and macrofauna of the Farasan Islands, South East Red Sea, Saudi Arabia     

Hamza Moustafa Khalil 《Arabian Journal of Geosciences》2012,5(6):1223-1245

The stratigraphy of the Farasan Islands (Pliocene?CPleistocene deposits) is established on the basis of a detailed study of six stratigraphic sections described and sampled in the field. Detailed examinations involve the microfacies analyses and identification of macrofossils makes it possible to determine two new informal formations, namely, from the base to the top: Esbah formation of Pliocene age and Farasan formation of Pleistocene age. The detected microfacies types of the studied samples are only carbonate facies and include five major types: mudstone, wackestone, packstone, floatstone and boundstone. No grains of quartz sand or igneous mineral were found in the islands. The nomenclature of the biostratigraphic units established in the present work is not intended to define world-wide zonal standards. It is only used to subdivide the sequence into biostratigraphic zones according to 137 macrofaunal species (78 bivalves, 56 gastropods and three echinoids). These biozones, namely: Lithophaga teres zone (Early Pliocene), Clypeaster reticulates?CLaganum depressum zone and Chesapecten madisonius?CNoetia limula interval zone are assigned to the Late Pliocene; meanwhile, Noetia limuli?CAnadara ovalis interval zone and A. ovalis range zone are assigned to the Pleistocene age. The affinity of the Pliocene?CPleistocene fauna recorded from the Farasan Islands increase with time towards the Indo-Pacific realm. The identified bivalves and gastropods are dominated by the Indo-Pacific forms suggesting the connection of the Red Sea rift with the open Indian Ocean via the Gulf of Aden and Bab El Mandab in the latest Miocene and Early Pliocene.  相似文献   

Hyperspectral Radiometry to Quantify the Grades of Iron Ores of Noamundi and Joda Mines,Eastern India     

Magendran Thangavelu  Sanjeevi Shanmugam  Arya Kumar Bhattacharya 《Journal of the Indian Society of Remote Sensing》2011,39(4):473-483

This paper present the results of a preliminary study to assess the potential of the visible, NIR and SWIR energy of the EMR in differentiating iron ores of different grades in a rapid manner using hyperspectral radiometry. Using different iron ore samples from Noamundi and Joda mines, Jharkhand and Orissa, states of India, certain spectro-radiometric measurements and geochemical analysis were carried out and the results have been presented. It was observed that the primary spectral characteristics of these iron ores lie in the 850 to 900 nm and 650–750 nm regions. The spectral parameters for each curve used for studying the iron ores are: (i) the slopes of the spectral curve in 685–725 nm region; (ii) position of the peak with respect to wavelength in 730–750 nm region and (iii) radius of curvature of the absorption trough in the 850–900 nm region. Comparison of these spectral parameters and the geochemistry of the samples indicates that the position of the peak of the curve in 730–750 nm region shifts towards longer wavelength with increasing iron oxide content, while the slope of the curvature in the 685–725 nm region has a strong negative correlation with the iron oxide content of the samples. Similarly, a strong negative correlation is observed between the radius of curvature of the 850–900 nm absorption trough and the iron oxide content. Such strong correlations indicate that hyperspectral radiometry in the visible and NIR regions can give a better estimate and quantification of the grades of iron ores. This study has demonstrated that generation of empirical models using hyperspectral radiometric techniques is helpful to quantify the grade of iron ores with limited geochemical analysis.  相似文献   

Contrasting isotopic signatures between anthropogenic and geogenic Zn and evidence for post-depositional fractionation processes in smelter-impacted soils from Northern France   总被引：2，自引：0，他引：2  

Farid Juillot  Delphine Jouvin  Philipe Telouk  Philippe Ildefonse  Steve Sutton  Gordon E. Brown Jr. 《Geochimica et cosmochimica acta》2011,75(9):2295-2308

Zinc isotopes have been studied along two smelter-impacted soil profiles sampled near one of the largest Pb and Zn processing plants in Europe located in northern France, about 50 km south of Lille. Mean δ⁶⁶Zn values along these two soil profiles range from +0.22 ± 0.17‰ (2σ) to +0.34 ± 0.17‰ (2σ) at the lowest horizons and from +0.38 ± 0.45‰ (2σ) to +0.76 ± 0.14‰ (2σ) near the surface. The δ⁶⁶Zn values in the lowest horizons of the soils are interpreted as being representative of the local geochemical background (mean value +0.31 ± 0.38‰), whereas heavier δ⁶⁶Zn values near the surface of the two soils are related to anthropogenic Zn. This anthropogenic Zn occurs in the form of franklinite (ZnFe₂O₄)-bearing slag grains originating from processing wastes at the smelter site and exhibiting δ⁶⁶Zn values of +0.81 ± 0.20‰ (2σ). The presence of franklinite is indicated by EXAFS analysis of the topsoil samples from both soil profiles as well as by micro-XANES analysis of the surface horizon of a third smelter-impacted soil from a distant site. These results indicate that naturally occurring Zn and smelter-derived Zn exhibit significantly different δ⁶⁶Zn values, which suggests that zinc isotopes can be used to distinguish between geogenic and anthropogenic sources of Zn in smelter-impacted soils. In addition to a possible influence of additional past sources of light Zn (likely Zn-sulfides and Zn-sulfates directly emitted by the smelter), the light δ⁶⁶Zn values in the surface horizons compared to smelter-derived slag materials are interpreted as resulting mainly from fractionation processes associated with biotic and/or abiotic pedological processes (Zn-bearing mineral precipitation, Zn complexation by organic matter, and plant uptake of Zn). This conclusion emphasizes the need for additional Zn isotopic studies before being able to use Zn isotopes to trace sources and pathways of this element in surface environments.  相似文献   

A new evaluation of seismic hazard for the northwestern part of Saudi Arabia     

Al-Arifi  Nassir S.  Fat-Helbary  R. E.  Khalil  Ahmad R.  Lashin  Aref A. 《Natural Hazards》2013,69(3):1435-1457

Natural Hazards - A new evaluation of seismic hazard in the northwestern part of Saudi Arabia area has been carried out, for the minimization and mitigation of earthquake losses. The study area...  相似文献   

Influence of Degree of Saturation in the Electric Resistivity–Hydraulic Conductivity Relationship     

Mohamed Ahmed Khalil  Fernando A. Monterio Santos 《Surveys in Geophysics》2009,30(6):601-615

The relationship between aquifer hydraulic conductivity and aquifer resistivity, either measured on the ground surface by vertical electrical sounding (VES) or from resistivity logs, or measured in core samples have been published for different types of aquifers in different locations. Generally, these relationships are empirical and semi-empirical, and confined in few locations. This relation has a positive correlation in some studies and negative in others. So far, there is no potentially physical law controlling this relation, which is not completely understood. Electric current follows the path of least resistance, as does water. Within and around pores, the model of conduction of electricity is ionic and thus the resistivity of the medium is controlled more by porosity and water conductivity than by the resistivity of the rock matrix. Thus, at the pore level, the electrical path is similar to the hydraulic path and the resistivity should reflect hydraulic conductivity. We tried in this paper to study the effect of degree of groundwater saturation in the relation between hydraulic conductivity and bulk resistivity via a simple numerical analysis of Archie’s second law and a simplified Kozeny-Carmen equation. The study reached three characteristic non-linear relations between hydraulic conductivity and resistivity depending on the degree of saturation. These relations are: (1) An inverse power relation in fully saturated aquifers and when porosity equals water saturation, (2) An inverse polynomial relation in unsaturated aquifers, when water saturation is higher than 50%, higher than porosity, and (3) A direct polynomial relation in poorly saturated aquifers, when water saturation is lower than 50%, lower than porosity. These results are supported by some field scale relationships.  相似文献