Paleoclimate record in the Nubian Sandstone Aquifer,Sinai Peninsula,Egypt

Sixteen groundwater samples collected from production wells tapping Lower Cretaceous Nubian Sandstone and fractured basement aquifers in Sinai were analyzed for their stable isotopic compositions, dissolved noble gas concentrations (recharge temperatures), tritium activities, and ¹⁴C abundances. Results define two groups of samples: Group I has older ages, lower recharge temperatures, and depleted isotopic compositions (adjusted ¹⁴C model age: 24,000–31,000 yr BP; δ¹⁸O: − 9.59‰ to − 6.53‰; δ²H: − 72.9‰ to − 42.9‰; < 1 TU; and recharge T: 17.5–22.0°C) compared to Group II (adjusted ¹⁴C model age: 700–4700 yr BP; δ¹⁸O: − 5.89‰ to − 4.84‰; δ²H: − 34.5‰ to − 24.1‰; < 1 to 2.78 TU; and recharge T: 20.6–26.2°C). Group II samples have isotopic compositions similar to those of average modern rainfall, with larger d-excess values than Group I waters, and locally measurable tritium activity (up to 2.8 TU). These observations are consistent with (1) the Nubian Aquifer being largely recharged prior to and/or during the Last Glacial Maximum (represented by Group I), possibly through the intensification of paleowesterlies; and (2) continued sporadic recharge during the relatively dry and warmer interglacial period (represented by Group II) under conditions similar to those of the present.     

Impact of climate change on the wheat-growing season over Iran

The objective of this paper is to derive and analyze the present and future climate projections over the region of wheat production over Iran. In addition, the projected future climate fluctuation results will be used to assist the maximum performance of wheat and to be used as the main basis for planning changes in the farming calendar in Iran. Observed climate (temperature and degree day) changes during the period (1951–2009) will be discussed. Projected future changes up to 2100 based on the MAGICC/SCENGEN 5.3 compound model was utilized. Furthermore, 18 scenarios were used to derive a single GCM model referred to as the United Kingdom Hadley Center Global Environment Model, which will be used to select the worst, best, and average scenario.     

Exploration of copper deposits in Wadi El Regeita area, Southern Sinai, Egypt, with contribution of remote sensing and geophysical data

Three types of hydrothermal alterations are recorded in Wadi El Regeita area, argillic, phyllic, and propylitic. Whole-rock analysis of representative samples of the alteration halo (1) shows a Cu, Au, and Ag content up to 1.7 wt.%, 1.6 g/t, and 4 g/t, respectively; in the alteration halo (2), these metal contents are up to 1.3 wt.%, 1.4 g/t, and 3 g/t, following the same order. The integrated remote sensing and geophysical data, as well as geological field verification, show that Wadi El Regeita area includes promising Cu ores within two hydrothermal alteration haloes. Spatial data analyses of lineaments from Landsat Enhanced Thematic Mapper (ETM) band ratio image (7/5, 5/4, 3/1) reveal the presence of alteration haloes that potentially may host Cu mineralization at south and north of El Regita Cu mine. Gravity interpretation indicates that the surveyed area is dissected by NE–SW fault zones in the central part, near Wadi El Regeita Cu mine. Ground magnetic survey data revealed that the surveyed area includes six magnetic bodies at depths ranging from 32 to 90 m, possibly recording the presence of mineralized and hydrothermally altered andesitic dykes. The half length of these dykes ranges from 600 to 1,070 m; their half thickness from 30 to 123 m and their half width from 48 to 531 m. Dyke locations coincide with surface alteration haloes (1) and (2) as indicated by the ETM band ratio image processing. The final assessment of the area, however, needs more detailed geological and geophysical studies with contributions of remote sensing techniques.     

Dominant impact of South Asian low heat on summer monsoon rainfall over Central India

Although previous literature have considered Southern Oscillation Index (SOI), Indian Dipole, and SST as the major teleconnection patterns to explain the variability of summer monsoon rainfall over India. South Asia low pressure and Indian Ocean high are the centers of action that dominates atmospheric circulations in Indian continent. This paper examines the possible impact of South Asian low pressure distribution on the variability of summer monsoon rainfall of India using centers of action approach. Our analysis demonstrates that the explanation of summer monsoon rainfall variability over Central India is improved significantly if the SOI is replaced by South Asian low heat. This contribution also explains the physical mechanisms to establish the relationships between the South Asian low heat and regional climate by examining composite maps of large-scale circulation fields using NCEP/NCAR Reanalysis data.     

Post-glacial persistence of turbiditic activity within the Rhône deep-sea turbidite system (Gulf of Lions,Western Mediterranean): Linking the outer shelf and the basin sedimentary records

Emplacement of post-glacial turbidites is commonly controlled by rapid changes in sea level or by seismicity. On the continental rise of the Gulf of Lions (Western Mediterranean), an aseismic area, we identified turbiditic beds deposited during the rising stage and highstand of sea level. Swath bathymetry, sediment cores, in situ Cone Penetrating Tests (CPTU), heavy mineral associations and radiocarbon dating determined the source, composition, distribution and age of the turbiditic beds. Turbidites are composed of homogeneous to positively graded silts to medium sand with quartz (up to 90%), shell debris and shelfal benthic faunas. Their distribution on the sea floor is very patchy and controlled by abundant inherited erosional bedforms. Their source is found in relict regressive sands at the outershelf. Their deposition occurred just after the onset of the post-glacial sea level rise and the concomitant sediment starvation of the Rhône deep sea turbiditic system until recently. Whilst canyons are fed with sand by strong seasonal hydro-sedimentary dynamics on the outershelf, the emplacement of post-glacial turbidites is not controlled by sea level changes but probably by the periodic flushing of the canyons. Our study revealed that this low energy aseismic margin undergoes significant transport of sand, down to the base of slope, during the sea-level rise and the Holocene highstand.     

Influence of atmospheric dust on non-telescopic sunspot observations

Catalogues of non-telescopic sunspot observations from the Orient have been presented by several authors. Since atmospheric dust facilitates naked-eye observation of the Sun we investigate its possible influence by comparing the historical records of sunspot sightings and atmospheric dust storms. A distinction is made between the record up to the end of the Ming dynasty that is based on court documents and the post-Ming reports that are all provincial sightings. The earlier record is found to be significantly anti-correlated with C-14 fluctuations while the latter one is weakly anti-correlated. The provincial sightings contain a much larger signature of atmospheric turbidity, as is also indicated by their poor comparison with telescopic data.     

Significance of enhanced infiltration due to groundwater extraction on the disappearance of a headwater lagoon system: Toluca Basin, Mexico

Mexico City relies significantly on groundwater resources drawn from the Sistema Lerma well field located in the Toluca Basin, Mexico. Enhanced infiltration caused by groundwater extraction is suspected to be both a prime factor in the disappearance of a lagoon system at the Toluca Basin and a potential risk to long-term groundwater quality. A combined approach of field investigation and numerical modeling was adopted to assess the groundwater-surface water interactions within the lagoon system. Potentiometric data indicate that current downward vertical hydraulic gradients below the lagoon and surrounding wetland area are extremely low suggesting very slow infiltration rates. Geochemical and isotope data from surface water and groundwater sampling also indicate that very little surface water infiltration has occurred. Numerical simulations demonstrate that enhanced surface water infiltration is unlikely to be the primary cause in the significant reduction in size of the lagoon system. Other factors such as modifications to the surface water drainage system and capture of spring flow from the surrounding mountainous regions are likely more significant. Simulations also suggest that contaminants originating in the lagoon system are currently entering nearby production wells although the total contaminant mass flux to the wells is still very low and significantly diluted.

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Resumen La Ciudad de México depende significativamente de los recursos de aguas subterráneas obtenidos del campo de pozos Sistema Lerma ubicado en la Cuenca Toluca, oeste de la Cuenca de México. Se sospecha que la infiltración estimulada causada por extracción intensiva de aguas subterráneas es un factor principal en la desaparición de un sistema de lagunas en la cabeceras del Río Lerma en el centro de México y un riesgo potencial para la calidad de aguas subterráneas a largo plazo en la región. Se adoptó un enfoque combinado de investigación de campo y modelizado numérico para evaluar las interacciones de agua superficial-agua subterránea dentro del sistema de lagunas. Datos potenciométricos indican que los gradientes hidráulicos verticales descendentes actuales, ubicados por debajo de la laguna y vecina área de humedales, son extremadamente bajos sugiriendo ritmos de infiltración muy lentos. Datos geoquímicos e isotópicos provenientes del muestreo de agua superficial y subterránea también indican que ha ocurrido muy poca infiltración de agua superficial. Las simulaciones numéricas demuestran cuantitativamente que no es probable que la infiltración estimulada de agua superficial sea la causa principal en la reducción significativa del tamaño del sistema de lagunas en la cabecera. Otros factores tal como modificaciones al sistema superficial de drenaje de agua y captura de flujo de manantial en las regiones montañosas vecinas son probablemente más significativos. Las simulaciones también sugieren que los contaminantes que se originan en el sistema de lagunas están actualmente ingresando a pozos de producción cercanos aunque el flujo de masa contaminante total a los pozos es aún muy bajo y diluido significativamente en los volúmenes grandes de extracción. La magnitud de la amenaza a largo plazo a la calidad del agua subterránea en los pozos de producción Sistema Lerma proveniente de contaminantes infiltrados es una preocupación y amerita estudios futuros.

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Résumé La Cité de Mexico dépend significativement des ressources en eau souterraine pompées au site de captages de Sistema Lerma, dans le Bassin de Toluca, à lOuest du Bassin de Mexico. Laugmentation de linfiltration, causée par lextraction extensive des eaux souterraines, est suspectée dêtre à la fois un facteur primaire de la disparition dun système de lagons en amont de la rivière Lerma au centre de Mexico, et un risque potentiel à long-terme pour la qualité de leau souterraine dans la région. Uen approche combinée détudes de terrain et de modélisation numérique a été adoptée pour estimer les interactions entre les eaux de surface et les eaux souterraines, au sein du système de lagons. Les données potentiométriques indiquent que les gradients hydrauliques verticaux descendants sont très bas au niveau des lagons, ce qui suppose un taux dinfiltration faible. Les données géochimiques et isotopiques provenant des eaux de surface et souterraines, indiquent également que peu deau de surface sinfiltrent. La simulation numérique démontre quantitativement que laugmentation de linfiltration des eaux de surface nest probablement pas la première cause de réduction des lagons. Dautres facteurs, tels que les modifications du drainage des eaux de surface, laménagement en captage des sources situées aux pieds des montagnes environnantes, sont probablement plus importants. Les simulations suggèrent également que les contaminants provenant des lagons se retrouvent également dans les captages les plus proches, bien que le flux total de contaminants entrant dans les captages reste faible. Les volumes dextraction étant très important ils diluent effectivement les contaminants. Les effets à long-terme de lextraction critique au niveau des forages de Sistema Lerma et de la dégradation de la qualité des eaux souterraines par les contaminants, nécessite une grande attention pour le futur.

     

Groundwater exploration and evaluation by using geophysical interpretation (case study: Al Qantara East, North Western Sinai, Egypt)

Different geophysical tools such as geoelectric, gravity, and magnetic have been applied to detect groundwater potentiality and structural elements, which controlled a geometry of the groundwater aquifers in the study area. Nineteen vertical electrical soundings measured using ABEM SAS 4000 equipment through Schlumberger configuration of AB/2 ranged from 1.5 to 1,000 m; the quantitative interpretation was carried out using manual and analytical techniques. The results of quantitative interpretation used to construct six geoelectrical cross-sections indicate that the subsurface sequence of the study area consists of seven geoelectrical units. These units are Quaternary sand sheet and sand dunes, Quaternary aquifer, marly limestone, clay, sandy clay, clay with sandstone intercalation, and deep Nubian sandstone aquifer. The isopach map of the Quaternary aquifer exhibits thickness of the Quaternary aquifer that increased at the northern and southern part (50 m) and decreased at the eastern and western part (5 m), and the depth of the aquifer increased at the northern part (40 m) and decreased at the central part to 6 m. The isoresistivity map of the aquifer shows a high resistivity at the northern part but the southern part reveals low resistivity according to the lithology. The water salinity increases in the direction of groundwater flow from 500 to 10,500 mg/l. The low water salinity is due to direct recharge from El-Sheikh Zayed Canal, which supplied fresh water to this area. Sixty-five gravity stations were measured using Auto-Grav gravity meter; different gravity corrections were applied on raw data. The corrected gravity values were plotted to represent a Bouguer anomaly map; the residual gravity anomaly map was used for delineation of the fault elements. The area was dissected by different fault elements of trends NW–SE, NE–SW, and E–W. In addition, 65 ground magnetic stations were measured at the same sites of gravity stations. The results of magnetic interpretation indicate that the depth of the basement is shallow at the western and southern parts of the area (4,500 m), but the central part exhibits greater depth of 7,900 m.

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الملخص العربي   طرق جيوفيزيقية مختلفة مثل الكهربية الأرضية, التناقلية الأرضية والمغناطيسية الأرضية تم تطبيقها لتحديد إمكانية تواجد المياه الجوفية والتراكيب الجيولوجية التي تتحكم في إبعاد وهندسة الخزان الجوفي في منطقة الدراسة. تسعة عشر جسة كهربية عمودية تم قياسها باستخدام جهاز من شركة (ِ ABEM) ساس 4000 من خلال تشكيل شلمبرجير بمسافة بين القطبين أب /2 تبدأ من 1.5 متر حتى 1000 متر, التفسير الكمي تم علي البيانات باستخدام التفسير اليدوي والتحليلي. نتائج التفسير الكمي تم استخدامها لتشييد ست قطاعات جيوكهربية والتي أوضحت أن التتابع التحت سطحي لمنطقة الدراسة يتكون من سبعة وحدات جيوكهربية. هذه الوحدات هي صفائح من الرمال والكثبان الرملية للعصر الرباعي, الخزان الجوفي الرباعي, حجر جيري مارلي, طفلة, طفله رمليه, طفله متداخلة مع الرمل والخزان الجوفي النوبي. خريطة السمك للخزان الجوفي الرباعي تظهر أن سمك الخزان الجوفي الرباعي يزيد عند شمال وجنوب منطقة الدراسة (50 متر) ويقل عند الجزء الشرقي والغربي (5 متر). وعمق هذا الخزان الجوفي الرباعي يزيد عند الجزء الشمالي (40 متر) وينقص عمق الخزان الرباعي عمد وسط المنطقة (6 متر). خريطة المقاومة الحقيقية للخزان الجوفي الرباعي تبين أن المقاومة تزيد عند الجزء الشمالي وتقل المقاومة عند الجزء الجنوبي من منطقة الدراسة بناءا علي التكوين الصخري للطبقات. ملوحة المياه الجوفية تزيد في اتجاه سريان المياه من 500 مليجرام/لتر إلي 10500 مليجرام/لتر. نقص الملوحة المياه ناتج عن التسرب المباشر من قناة الشيخ زايد والتي تعتبر مصدر المياه العزبة في منطقة الدراسة. خمس وستون محطة تثاقيلية أرضية تم قياسها باستخدام اوتو-جرافميتر, العديد من تصحيحات الجاذبية الأرضية نم تطبيقها علي البيانات الأصلية. قراءات الجاذبية الأرضية المصححة تم رسمها علي خريطة لتمثل شاذات البوجير وتم استخدام خريطة الشاذات المحلية لتجديد التراكيب الجيولوجية (الفوالق). حيت أوضحت الدراسة أن المنطقة تأثرت بعده فوالق باتجاهات مختلفة مثل شمال غرب- جنوب شرق, شمال شرق-جنوب غرب وشرق-غرب. نتيجة تفسير بيانات المغناطيسية الأرضية أظهرت أن عمق ضجور القاعدة تكون ضحلة عند الجزء الغربي والجنوبي (4500 متر) وتكون ضجور القاعدة عميقة (7900 متر) عند الجزء الأوسط من منطقة الدراسة.

     

Tectonic evolution of kid metamorphic complex and the recognition of Najd fault system in South East Sinai,Egypt

International Journal of Earth Sciences - A low-to medium-grade metamorphic belt of a volcano-sedimentary succession occurs in the eastern side of South Sinai as a part of the northernmost...     

Introduction to TETHYS—an interdisciplinary GIS database for studying continental collisions

The TETHYS GIS database is being developed as a way to integrate relevant geologic, geophysical, geochemical, geochronologic, and remote sensing data bearing on Tethyan continental plate collisions. The project is predicated on a need for actualistic model ‘templates’ for interpreting the Earth's geologic record. Because of their time-transgressive character, Tethyan collisions offer ‘actualistic’ models for features such as continental ‘escape’, collision-induced upper mantle flow magmatism, and marginal basin opening, associated with modern convergent plate margins. Large integrated geochemical and geophysical databases allow for such models to be tested against the geologic record, leading to a better understanding of continental accretion throughout Earth history. The TETHYS database combines digital topographic and geologic information, remote sensing images, sample-based geochemical, geochronologic, and isotopic data (for pre- and post-collision igneous activity), and data for seismic tomography, shear-wave splitting, space geodesy, and information for plate tectonic reconstructions. Here, we report progress on developing such a database and the tools for manipulating and visualizing integrated 2-, 3-, and 4-d data sets with examples of research applications in progress. Based on an Oracle database system, linked with ArcIMS via ArcSDE, the TETHYS project is an evolving resource for researchers, educators, and others interested in studying the role of plate collisions in the process of continental accretion, and will be accessible as a node of the national Geosciences Cyberinfrastructure Network—GEON via the World-Wide Web and ultra-high speed internet2. Interim partial access to the data and metadata is available at: http://geoinfo.geosc.uh.edu/Tethys/ and http://www.esrs.wmich.edu/tethys.htm. We demonstrate the utility of the TETHYS database in building a framework for lithospheric interactions in continental collision and accretion.