Integrated studies for characterization of lineaments used to locate groundwater potential zones in a hard rock region of Karnataka, India     

Subash Chandra  V. A. Rao  N. S. Krishnamurthy  S. Dutta  Shakeel Ahmed 《Hydrogeology Journal》2006,14(5):767-776

An integrated study was carried out to investigate the subsurface geological conditions in a hard rock environment, with the aim of identifying zones with groundwater resource potential. The study, in Bairasagara watershed, Karnataka, India, considered geomorphology, water level, resistivity imaging, self potential, total magnetic field and susceptibility. The signatures due to lineaments have been clearly identified and their role in groundwater movement has been documented. Synthetic simulation methods were used to model the electrical response of the lineament using finite differential modeling scheme. The inverted image of the field data is compared with the synthetic image and iteration were performed on the initial model until a best match was obtained resulting on the generation of the calibrated resistivity image of the subsurface. Resistivity imaging revealed that the dykes are weathered/fractured to a depth of 6–8 m and are compact at deeper levels, and that they behave as barriers to groundwater movement, yet facilitate a good groundwater potential zone on the upgradient side. The results of magnetic surveys were utilized in differentiating granites and dolerite dykes with an insignificant resistivity contrast. Geomorphological expression alone cannot reveal the groundwater potential associated with a lineament. However, characterizing the nature of the feature at depth with integrated geophysical methods provides essential information for assessing that potential.An erratum to this article can be found at  相似文献   

Association of hydrogeological factors in temporal variations of fluoride concentration in a crystalline aquifer in India   总被引：6，自引：0，他引：6  

P. D. Sreedevi  S. Ahmed  B. Made  E. Ledoux  J. M. Gandolfi 《Environmental Geology》2006,50(1):1-11

The major part of groundwater in India is found in granitic aquifers. Fluoride in groundwater from a crystalline aquifer in a semi-arid region of granitic rocks in India, known as Maheshwaram watershed, was analyzed for spatial and temporal variability during 1999–2002 to assess the effect of hydrogeological factors on fluoride concentration. Samples were collected from 32 representative wells in the area for the pre- and post-monsoon seasons and analyzed for F content. The CHESS computer program was used to calculate ionic activities of aqueous species and the mineral saturation index (SI) for calcite and fluorite. The GARDENIA computer program was used to calculate the recharge values in the study area. The influences of dissolution kinetics of fluoride minerals and recharge from rainfall on fluoride concentration were of interest and results clearly indicate that fluoride content in groundwater depends on the interaction period of groundwater with host rock. Results could also be utilized for designing remedial measures particularly with dilution method in an optimal way.  相似文献   

Formation and mineral chemistry of a calcic skarn from Al-Madhiq, SW Saudi Arabia   总被引：2，自引：0，他引：2  

Zulfiqar Ahmed  Mustafa M. Hariri 《Chemie der Erde / Geochemistry》2006,66(3):187-201

A newly identified skarn occurrence is described from the Neoproterozoic rocks of the SW Arabian shield. It is exposed to the SE, E and NE of the Al-Madhiq town. The skarn attributes correspond to those typical of the calcic skarns that host W-deposits. It is characterized as an exoskarn of the proximal type, related to a granitoid contact close to an impure quartzite bed within the regional metamorphic rocks of mixed sedimentary and volcanic derivation. The skarn is localized along a shear zone parallel to the regional faults and other major shear zones. Samples from the studied area contain characteristic skarn minerals that include both the prograde (brownish red grossular, ferrosalite, aluminian titanite-grothite, albite-oligoclase, scapolite), and retrograde (epidote, quartz, hornblende, calcite) assemblages. The pyroxenes are ferrosalites, Mn-bearing, and more like those from “oxidized” skarns; although garnets indicate it to be a “reduced” type skarn. Epidote mimicks that from typical skarns, as it bears a pistacite content of 15.9–20.7%. Grossular composition reflects a largely reduced genetic environment; as it is in solid solution with 6.5–21.6% andradite, 0–0.15% uvarovite, 0–0.47% pyrope, 4.33–18.75% almandine, and 0.4–8.58% spessartine molecules. Titanite composition varies from aluminian titanite to grothite, that may be analogous to the newly described Al-rich titanite from the low-pressure calc-silicate rocks.  相似文献   

Ground Water Contamination of Arsenic in Ganges Plain     

Hiroaki Ishiga  Kaori Dozen  Md. Badrul Islam  Md. Hamidur Rahman  Md. Abdus Sattar  Chikako Yamazaki  Ahmed Faruque 《Gondwana Research》2001,4(4):636

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The Precambrian Terranes of Yemen and their Correlation with those of Saudi Arabia and Somalia: Implications for the Accretion of Gondwana     

Brian F. Windley  Martin J. Whitehouse  Douglas B. Stoeser  Salah Al-Khirbash  Mahfood A.O. Ba-Bttat  Ahmed Al-Ghotbah 《Gondwana Research》2001,4(2)

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X-Ray Spectral Study of AGN Sources Content in Some Deep Extragalactic XMM-Newton Fields     

M. A. Hassan  B. A. Korany  R. Misra  I. A. M. Issa  M. K. Ahmed  F. A. Abdel-Salam 《Astrophysics and Space Science》2012,339(2):355-364

We undertake a spectral study of a sample of bright X-ray sources taken from six XMM-Newton fields at high galactic latitudes, where AGN are the most populous class. These six fields were chosen such that the observation had an exposure time more than 60 ksec, had data from the EPIC-pn detector in the full-Frame mode and lying at high galactic latitude |b|>25^∘. The analysis started by fitting the spectra of all sources with an absorbed power-law model, and then we fitted all the spectra with an absorbed power-law with a low energy black-body component model.The sources for which we added a black body gave an F-test probability of 0.01 or less (i.e. at 99% confidence level), were recognized as sources that display soft excess. We perform a comparative analysis of soft excess spectral parameters with respect to the underlying power-law one for sources that satisfy this criterion. Those sources, that do not show evidence for a soft excess, based on the F-test probability at a 99% confidence level, were also fitted with the absorbed power-law with a low energy black-body component model with the black-body temperature fixed at 0.1 and 0.2 keV. We establish upper limits on the soft excess flux for those sources at these two temperatures. Finally we have made use of Aladdin interactive sky atlas and matching with NASA/IPAC Extragalactic Database (NED) to identify the X-ray sources in our sample. For those sources which are identified in the NED catalogue, we make a comparative study of the soft excess phenomenon for different types of systems.  相似文献   

Food security and dietary diversity of tea workers of two tea gardens in greater Sylhet district of Bangladesh     

Ahmed  Jasim Uddin  Mozahid  Md. Nur  Dhar  Aurup Ratan  Alamgir  Md. Shah  Jannat  Arifa  Islam  Md. Monirul 《GeoJournal》2021,86(2):1015-1027

The study analyzed the food security and dietary diversity of tea workers in Lakkatura Tea Garden and Ootterbhag Tea garden in greater Sylhet district of Bangladesh. A total of 200 respondents (100 from each tea estate) were interviewed to evaluate the food security and dietary diversity. The study found that average daily per capita calorie intake by tea workers was 2095.96 kcal. In addition, around 85.30% of the total calorie intake was received from the rice consumption. Average per capita daily intake of rice was estimated at 538.51 gm which is higher than the national average. It was also observed that 71.7 and 65.0% households were food secure in Lakkatura and Ootterbhag Tea garden, respectively. In Lakkatura Tea Garden, 61.67% tea workers have medium dietary diversity and in Ootterbhag Tea Estate 49.47% tea workers have low dietary diversity. Using the logit model analysis, this study provides food consumption patterns of tea workers and determine the factors responsible for food security. Household size, farm income and daily calorie intake were found having significant influence on households’ food security. For improving socioeconomic conditions of tea workers, educational institution should be set up to improve their educational status and government should give loans for them at a low interest rate and create alternative job opportunity in off season.

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Implementation of a Petrographical and Petrophysical Workflow Protocol for Studying the Impact of Heterogeneity on the Rock Typing and Reservoir Quality of Reefal Limestone: A Case Study on the Nullipore Carbonates in the Gulf of Suez     

Mona G. SAFA  Bassem S. NABAWY  Ahmed M.K. BASAL  Mohammad A. OMRAN  Aref LASHIN 《《地质学报》英文版》2021,95(5):1746-1762

This study focuses on the heterogeneity of the middle Miocene syn-rift Belayim nullipore (reefal) marine sequences in the Gulf of Suez and its impacts on reservoir quality. The sequences consist of coralline algal reef limestones with a highly complex dual-porosity system of primary and secondary porosities of widely varying percentages. To achieve a precise mathematical modeling of these reservoir sequences, a workflow protocol was applied to separate these sequences into a number of hydraulic flow units (HFUs) and reservoir rock types (RRTs). This has been achieved by conducting a conventional core analysis on the nullipore marine sequence. To illustrate the heterogeneity of the nullipore reservoir, the Dykstra-Parsons coefficient (V) has been estimated (V = 0.91), indicating an extremely heterogeneous reservoir. A slight to high anisotropy (λk) has been assigned for the studied nullipore sequences. A stratigraphic modified Lorenz plot (SMLP) was applied to define the optimum number of HFUs and barriers/baffles in each of the studied wells. Integrating the permeability-porosity, reservoir quality index-normalized porosity index (RQI-NPI) and the RQI-flow zone indicator (RQI-FZI) plots, the discrete rock types (DRT) and the R35 techniques enable the discrimination of the reservoir sequences into 4 RRTs/HFUs. The RRT4 packstone samples are characterized by the best reservoir properties (moderate permeability anisotropy, with a good-to-fair reservoir quality index), whereas the RRT1 mudstone samples have the lowest flow and storage capacities, as well as the tightest reservoir quality.  相似文献   

Rudists (Bivalvia) from a Cretaceous Platform in Northern Egypt:Taxonomy and Paleobiogeography     

Yasser SALAMA  Jamaan S. AJAREM  Ahmed A. ALLAM  Ahmed M. ALMALKI 《《地质学报》英文版》2021,95(6):1967-1983

New well-preserved rudist materials come from the Barremian–Turonian marine formations in the Yelleg, Minsherah, Maaza, and Raghawi sections in North Sinai, northern Egypt. There, 17 discovered rudist species belonging to 13 genera and seven taxonomic families are described in detail as follows: Eoradiolites plicatus (Conrad), Eoradiolites liratus (Conrad), Praeradiolites ponsianus (?Archiac), Archaeoradiolites sp., Bournonia africana Douvillé, Bournonia fourtaui Douvillé, Biradiolites lombricalis (?Orbigny), Biradiolites zumoffeni Douvillé, Radiolites lewyi lewyi Parnes, Radiolites sauvagesi (?Hombres-Firmas), Durania arnaudi (Choffat), Toucasia carinata (Matheron), Toucasia sp., Neocaprina raghawiensis Steuber and Bachmann, Sellaea sp., Ichthyosarcolites sp. and Horoiopleura sp.. The Cenomanian deposits in the northern Eastern desert of Egypt only contain E. liratus. The domination of the Cenomanian rudist species in North Sinai, however, is attributed to changes in the platform, which passes mainly from carbonate in the north to siliciclastics in the south. The presence of Horiopleura sp. in the late Barremian–early Aptian deposits is documented for the first time, which suggests the expansion of taxa of the genus Horiopleura Douvillé to North Sinai during this interval. The age of the rudist species is documented from the late Barremian–Turonian formations, with their geographic distribution in the Mediterranean region considered..  相似文献   

Perceived and actual risks of drought: household and expert views from the lower Teesta River Basin of northern Bangladesh     

Salam  Roquia  Ghose  Bonosri  Shill  Badhon Kumar  Islam  Md. Aminul  Islam  Abu Reza Md. Towfiqul  Sattar  Md. Abdus  Alam  G. M. Monirul  Ahmed  Bayes 《Natural Hazards》2021,108(3):2569-2587

Natural Hazards - Disaster risk perception and risk appraisal are essential in formulating an appropriate disaster risk reduction policy. This study examines the actual vs perceived drought risks...  相似文献