Selective blackening of bioclasts via mixing‐zone aragonite neomorphism in Late Triassic limestone,Zlatibor Mountains,Serbia     

KINGA HIPS  JÁNOS HAAS  MÁRIA VIDÓ  ZSUZSANNA BARNA  DIVNA JOVANOVIĆ  MILAN N. SUDAR  ZOLTÁN SIKLÓSY 《Sedimentology》2011,58(4):854-877

A peculiar facies of the Norian–Rhaetian Dachstein‐type platform carbonates, which contains large amounts of blackened bioclasts and dissolutional cavities filled by cements and internal sediments, occurs in the Zlatibor Mountains, Serbia. Microfacies investigations revealed that the blackened bioclasts are predominantly Solenoporaceae, with a finely crystalline, originally aragonite skeleton of fine cellular structure. Blackening of other bioclasts also occurs subordinately. Solenoporacean‐dominated reefs, developed behind the platform margin patch‐reef tract, were the main source of sand‐sized detritus. The blackened and other non‐blackened bioclasts are incorporated in automicrite cement. Radiaxial fibrous calcite cements in the dissolutional cavities are also black, dark grey or white. Reworked black pebbles were reported from many occurrences of peritidal deposits; in those cases, the blackening took place under pedogenic, meteoric diagenetic conditions. In contrast, in the inner platform deposits of the Ilid?a Limestone, the blackening of bioclasts occurred in a marine–meteoric mixing‐zone, as indicated by petrographic features and geochemical data of the skeleton‐replacing calcite crystals. Attributes of mixing‐zone pore waters were controlled by mixing corrosion, different solubility of carbonate minerals and microbial decomposition of organic matter. In the moderate‐energy inner platform environment, large amounts of microbial organic tissue were accumulated and subsequently decomposed, triggering selective blackening in the course of early, shallow burial diagenesis. The δ¹⁸O and δ¹³C values of the mixing‐zone precipitates and replacive calcite do not produce a linear mixing trend. Variation mainly resulted from microbial decomposition of organic matter that occurred under mixing‐zone conditions. The paragenetic sequence implies cyclic diagenetic conditions that were determined by marine, meteoric and mixing‐zone pore fluids. The diagenetic cycles were controlled by sea‐level fluctuations of moderate amplitude under a semi‐arid to semi‐humid climate.  相似文献   

Air temperature and wind changes in Costa Rica during the total solar eclipse of July 11, 1991     

Walter FernÁndez  Vilma Castro  Hugo Hidalgo 《Earth, Moon, and Planets》1993,63(2):133-147

Air temperature and wind measurements on the surface and in the free atmosphere taken during the total solar eclipse of July 11, 1991, are analyzed. Surface air temperature decreased significantly, 2 to 5 °C in general, with the lowest values occurring 10 to 30 minutes after totality. In some places, surface wind speed decreased gradually during the eclipse, as a result of the decrease of air temperature and temperature gradients. In other places, it increased due to local atmospheric conditions. A radiosonde launched at 13:26 LT (local time) appeared to have been affected by the moon's shadow at about 13 km height. At this altitude temperature was relatively lower than usual and the balloon carrying the radiosonde experienced an upward acceleration. Also at this altitude wind direction changed and wind speed decreased  相似文献   

pH-dependent copper release in acid soils treated with crushed mussel shell     

B. Garrido-Rodríguez  D. Fernández-Calviño  J. C. Nóvoa Muñoz  M. Arias-Estévez  M. Díaz-Raviña  E. Álvarez-Rodríguez  M. J. Fernández-Sanjurjo  A. Núñez-Delgado 《International Journal of Environmental Science and Technology》2013,10(5):983-994

The aim of this study was to assess the influence of pH on copper mobilization in two copper-rich acid soils (from vineyard and mine) amended with crushed mussel shell. Crushed mussel shell amended soils (0–48 Mg ha^?1) were subjected to the effect of several acid and alkali solutions in a batch experiment in order to study their copper release. Copper distribution was studied in decanted soils from batch experiments using a sequential extraction procedure, whereas the effect of crushed mussel shell on copper release kinetics was studied using a stirred flow reactor. When soils were treated with acid solutions, the copper mobilization from non-amended soils was significantly higher than from the amended samples. Major changes in copper fractionation were an increase of the acid soluble fraction in acid-treated vineyard soil samples with shell dose. For the mine soil, the oxidable fraction showed a relevant diminution in acid-treated samples at the highest crushed mussel shell dose. For both soils, copper desorption rates diminished up to 86 % at pH 3 when crushed mussel shell was added. At pH 5, copper release rate was very slow for both soils decreasing up to 98 % for the mine soil amended with the highest shell dose, whereas no differences were observed at pH 7 between amended and non-amended soils. Thus, crushed mussel shell addition could contribute to reduce potential hazard of copper-enriched soils under acidification events.  相似文献   

Thermal, mechanical and chemical influences on the performance of optical fibres for distributed temperature sensing in a hot geothermal well   总被引：2，自引：2，他引：0  

Thomas Reinsch  Jan Henninges  Ragnar Ásmundsson 《Environmental Earth Sciences》2013,70(8):3465-3480

Structural well-bore integrity is an important issue for sustainable provision of geothermal energy. Raman scattering based fibre optic distributed temperature sensing (DTS) can help to monitor the status of a well and therefore help to optimize expensive work-over activities. This study reports on the installation of a fibre-optic cable in the cemented annulus behind the anchor casing in the high temperature geothermal well HE-53, Hellisheiði geothermal field, SW Iceland. Although the cable has been damaged during the installation, temperature data could be acquired during the entire length of installation down to 261.3 m. Temperature measurements were performed during the installation in spring 2009, during the onset of a flow test in summer 2009 and after a 8.5 month shut-in period in summer 2010. During the flow test, maximum temperatures of 230 °C were measured after 2 weeks fluid production. Using optical time domain reflectometry (OTDR), attenuation measurements at 850 and 1,300 nm enabled to identify mechanical, thermal, and chemical degradation along the optical fibre. The observed degradation led to erroneous temperature readings and limits, due to the optical budget of the DTS system, the accessible length of the fibre. The characteristics and the influence of the different degradation mechanisms on the accuracy of the DTS measurements are discussed and recommendations for an optimized installation are given.  相似文献   

Cathodoluminescence microscopy and spectroscopy of forsterite from Kaba meteorite: An application to the study of hydrothermal alteration of parent body     

Arnold Gucsik  Taro Endo  Hirotsugu Nishido  Kiyotaka Ninagawa  Masahiro Kayama  Szaniszló Bérczi  Szabolcs Nagy  Péter Ábrahám  Yuki Kimura  Hitoshi Miura  Ildikó Gyollai  Irakli Simonia  Péter Rózsa  József Posta  Dániel Apai  Krisztián Mihályi  Mihály Nagy  Ulrich Ott 《Meteoritics & planetary science》2013,48(12):2577-2596

Highly forsteritic olivine (Fo: 99.2–99.7) in the Kaba meteorite emits bright cathodoluminescence (CL). CL spectra of red luminescent forsterite grains have two broad emission bands at approximately 630 nm (impurity center of divalent Mn ions) in the red region and above 700 nm (trivalent Cr ions) in the red–IR region. The cores of the grains show CL blue luminescence giving a characteristic broad band emission at 400 nm, also associated with minor red emissions related to Mn and Cr ions. CL color variation of Kaba forsterite is attributed to structural defects. Electron probe microanalyzer (EPMA) analysis shows concentrations of Ca, Al, and Ti in the center of the forsterite grain. The migration of diffusible ions of Mn, Cr, and Fe to the rim of the Kaba meteoritic forsterite was controlled by the hydrothermal alteration at relatively low temperature (estimated at about 250 °C), while Ca and Al ions might still lie in the core. A very unusual phase of FeO (wüstite) was also observed, which may be a terrestrial alteration product of FeNi‐metal.  相似文献   

TimeBliography: A Dynamic and Online Bibliography on Temporal GIS     

Willington Siabato  Christophe Claramunt  Miguel Ángel Manso‐Callejo  Miguel Ángel Bernabé‐Poveda 《Transactions in GIS》2014,18(6):799-816

This article introduces an online bibliography on temporal GIS, a research area in which different scientific fields and researchers have provided substantial results and literature over the past few years. We first define the scientific domain of temporal GIS, its origin and recent evolution, and the context of this bibliography. Then, the components and functionalities of the web‐based application that support the online bibliography are described. The bibliography, entitled TimeBliography, is accessible on the Web at http://spaceandtime.wsiabato.info .  相似文献   

GIS approach to scale issues of perimeter-based shape indices for drainage basins     

ANDRÁS BÁRDOSSY  FRIDJOF SCHMIDT 《水文科学杂志》2013,58(6):931-942

Abstract

Shape indices have been in use for several decades to describe the characteristics and hydrological properties of drainage basins. Due to the fractal behaviour of the basin boundary, perimeter-based shape indices depend on the scale at which they are determined. Therefore, these indices cannot objectively compare drainage basins across a range of scales and basin sizes. This paper presents an objective GIS-based methodology for determining scale-dependent shape indices from gridded drainage basin representations. The scale effect is addressed by defining a representative scale at which the indices should be determined, based on a threshold symmetric difference between two grids representing the drainage basin at different resolutions.  相似文献   

Zone design of specific sizes using adaptive additively weighted Voronoi diagrams     

Pilar Moreno-Regidor  Jésus García López de Lacalle  Miguel-Ángel Manso-Callejo 《International journal of geographical information science》2013,27(10):1811-1829

Territory or zone design processes entail partitioning a geographic space, organized as a set of areal units, into different regions or zones according to a specific set of criteria that are dependent on the application context. In most cases, the aim is to create zones of approximately equal sizes (zones with equal numbers of inhabitants, same average sales, etc.). However, some of the new applications that have emerged, particularly in the context of sustainable development policies, are aimed at defining zones of a predetermined, though not necessarily similar, size. In addition, the zones should be built around a given set of seeds. This type of partitioning has not been sufficiently researched; therefore, there are no known approaches for automated zone delimitation. This study proposes a new method based on a discrete version of the adaptive additively weighted Voronoi diagram that makes it possible to partition a two-dimensional space into zones of specific sizes, taking both the position and the weight of each seed into account. The method consists of repeatedly solving a traditional additively weighted Voronoi diagram, so that each seed's weight is updated at every iteration. The zones are geographically connected using a metric based on the shortest path. Tests conducted on the extensive farming system of three municipalities in Castile-La Mancha (Spain) have established that the proposed heuristic procedure is valid for solving this type of partitioning problem. Nevertheless, these tests confirmed that the given seed position determines the spatial configuration the method must solve and this may have a great impact on the resulting partition.  相似文献   

Late Ediacaran syn‐rift/post‐rift transition and related fault‐driven hydrothermal systems in the Anti‐Atlas Mountains,Morocco     

J. Javier Álvaro 《Basin Research》2013,25(3):348-360

The syn‐rift/post‐rift transition of the late Ediacaran‐mid Cambrian Atlas rift is characterized by the interplay of several processes, such as a widespread episode of fracturing and tilting, associated with encasement of fault‐controlled vein metallic ore deposits of economic importance, and carbonate production and phosphogenesis (Taguedit Bed, Tabia Member) bordering rift‐flank uplifts. A correlatable unconformity marks the end of these processes and the beginning of a thermal subsidence‐dominated regime with development of a more stable, carbonate, peritidal‐dominated platform (Tifnout Member). Late Ediacaran microbial carbonate production and phosphogenesis extended in discontinuous belts around the periphery of uplifted rift shoulders and flanks. Karst development is interpreted to have formed along synsedimentary faults and fractures during abrupt tectonic uplift associated with emplacement of polymetallic hydrothermal dikes (rich in Cu, Fe and subsidiary Pb, Zn). Isotopic analysis indicates that speleothem precipitation in karstic palaeocaves displays significantly lighter δ¹³C and δ¹⁸O values as compared to the host dolomite, implying calcite precipitation by terrestrial fluids rich in decomposing organic matter and/or microbial activity in the cave system.  相似文献   

River flow forecasting system with data management,graphical river network control and interactive operation     

LÁSZLÓ IRITZ 《水文科学杂志》2013,58(6):637-651

Abstract

The feasibility and success of a forecasting system depend on many factors. Although the models may be of the highest accuracy, they cannot make a forecasting system effective without a well organized database and interpretable output. The interaction between the processes of data management, computation and output presentation should be dynamic. A complete river forecasting system for IBM (or compatible) personal computers aimed at meeting the above demands has been developed at the Department of Hydrology of Uppsala University. The program package sets up the river network, stores a database for it, supplies the appropriate data for a wide choice of forecasting models, and gives interpretable output. The functions are supported by screen graphics. The paper presents this system, the most important points of the algorithms, and an example application.  相似文献