Using advanced soft computing techniques for regional shoreline geoid model estimation and evaluation

This study aims at evaluating the global geoid model for a regional shoreline fitting using advanced soft computing techniques and global navigation satellite system/leveling measurements. Artificial neural networks, fuzzy logic, and least square support vector machine models are developed and used to fit the global geoid model for the north coastal Egyptian line. In addition, a novel estimation geoid model is designed and evaluated based on the latest global geoid models. The results of the three estimation models show that they can be used to correct the shoreline geoid model, in terms of root mean square error that ranges from 1.7 to 8.5?cm. Moreover, it is found that the least square vector machine model is a competitive approach with certain advantage in solving complex problems represented by missing data.     

Physical and geometrical parameters of VCBS XIII: HIP 105947

The best physical and geometrical parameters of the main sequence close visual binary system(CVBS), HIP 105947, are presented. These parameters have been constructed conclusively using Al-Wardat's complex method for analyzing CVBSs, which is a method for constructing a synthetic spectral energy distribution(SED) for the entire binary system using individual SEDs for each component star. The model atmospheres are in its turn built using the Kurucz(ATLAS9) line-blanketed plane-parallel models. At the same time, the orbital parameters for the system are calculated using Tokovinin's dynamical method for constructing the best orbits of an interferometric binary system. Moreover, the mass-sum of the components, as well as the ?θ and ?ρ residuals for the system, is introduced. The combination of Al-Wardat's and Tokovinin's methods yields the best estimations of the physical and geometrical parameters. The positions of the components in the system on the evolutionary tracks and isochrones are plotted and the formation and evolution of the system are discussed.     

Climate impacts of environmental degradation in Sudan

There exists an impressive amount of work for Sudan showing the anthropogenic degradation of natural vegetation cover. However, there are few examples of consequent climatic changes in literature. This work, thus, seeks to assess such effects of environmental forcing on various climatic patterns over the past few decades. Within the frame of the present analysis, the results are quite striking and are in concordance with scientific contentions that such land degradation could result in climatic modification. Higher temperature and less rainfall, sunshine duration and global radiation have been noticed. Evapotranspiration has responded more to the warming and drying conditions, thus showed signs of increasing rates, especially during the wet season. However, the extent of increase seems to have been suppressed by the decrease in sunshine duration and solar radiation as well as the inconsistent behaviour of wind speed. Changes in the variability of the within-year monthly observations have also occurred, thus suggesting an increase in the occurrence of extremes. The observed climatic modification in the country has exaggerated the insidious drought conditions. The present findings are hoped to contribute to our understanding of the effects of environmental problem and assist in considering policy responses. This revised version was published online in July 2006 with corrections to the Cover Date.     

Stratigraphy of the Cenomanian–Turonian Oceanic Anoxic Event OAE2 in shallow shelf sequences of NE Egypt

Two shallow water late Cenomanian to early Turonian sequences of NE Egypt have been investigated to evaluate the response to OAE2. Age control based on calcareous nannoplankton, planktic foraminifera and ammonite biostratigraphies integrated with δ¹³C stratigraphy is relatively good despite low diversity and sporadic occurrences. Planktic and benthic foraminiferal faunas are characterized by dysoxic, brackish and mesotrophic conditions, as indicated by low species diversity, low oxygen and low salinity tolerant planktic and benthic species, along with oyster-rich limestone layers. In these subtidal to inner neritic environments the OAE2 δ¹³C excursion appears comparable and coeval to that of open marine environments. However, in contrast to open marine environments where anoxic conditions begin after the first δ¹³C peak and end at or near the Cenomanian–Turonian boundary, in shallow coastal environments anoxic conditions do not appear until the early Turonian. This delay in anoxia appears to be related to the sea-level transgression that reached its maximum in the early Turonian, as observed in shallow water sections from Egypt to Morocco.     

Hydrogeological framework and water balance studies in parts of Krishni–Yamuna interstream area, Western Uttar Pradesh, India

The Krishni–Yamuna interstream area is a micro-watershed in the Central Ganga Plain and a highly fertile track of Western Uttar Pradesh. The Sugarcane and wheat are the major crops of the area. Aquifers of Quaternary age form the major source of Irrigation and municipal water supplies. A detailed hydrogeological investigation was carried out in the study area with an objective to assess aquifer framework, groundwater quality and its resource potential. The hydrogeological cross section reveals occurrence of alternate layers of clay and sand. Aquifer broadly behaves as a single bodied aquifer down to the depth of 100 m bgl (metre below ground level) as the clay layers laterally pinch out. The depth to water in the area varies between 5 and 16.5 m bgl. The general groundwater flow direction is from NE to SW with few local variations. An attempt has been made to evaluate groundwater resources of the area. The water budget method focuses on the various components contributing to groundwater flow and groundwater storage changes. Changes in ground water storage can be attributed to rainfall recharge, irrigation return flow and ground water inflow to the basin minus baseflow (ground water discharge to streams or springs), evapotranspiration from ground water, pumping and ground water outflow from the basin. The recharge is obtained in the study area using Water table fluctuation and Tritium methods. The results of water balance study show that the total recharge in to the interstream region is of the order of 185.25 million m³ and discharge from the study area is of the order of 203.24 million m³, leaving a deficit balance of −17.99 million m³. Therefore, the present status of groundwater development in the present study area has acquired the declining trend. Thus, the hydrogeological analysis and water balance studies shows that the groundwater development has attained a critical state in the region.     

Water supply problems in the Butana region-central Sudan with special emphasis on Jebel Qeili area

The Butana region of central Sudan is famous for its animal wealth and extensive pastures. Yet scarcity of water resources in the area especially during the dry seasons handicaps the proper utilization of these pastures. The area is occupied by non-water-bearing basement rocks and the only source of water is from direct run-off. Thus large numbers of small-size water reservoirs, haffirs, were constructed, but these are inadequate to provide enough water for the growing human and animal population. An all-year lake is here proposed to be constructed utilizing the ring-structure the Jebel Qeili igneous complex, central Butana. This lake is expected to solve the present water problem and meet the future demand of central Butana at the present rate of human and animal growth.     

A new record and a new ichnospecies of Arachnostega from the Middle Miocene of Egypt

The ichnogenus Arachnostega Bertling, 1992 is recorded for the first time from a bioeroded, coral-rich, Middle Miocene limestone bed in the middle Siwa Escarpment Member (Marmarica Formation) at Siwa Oasis, northern Western Desert of Egypt. These burrowing traces are preserved on the surface of a few internal moulds of bivalves and gastropods. Until now, the ichnogenus Arachnostega included a single ichnospecies, A. gastrochaenae Bertling, 1992. In the material studied herein, two ichnospecies are identified, described, illustrated and compared with other, similar traces. One of these is a new ichnospecies of Arachnostega; this is here named A. siwaensis ichnosp. nov. It is distinguished from A. gastrochaenae in the possession of tunnels that usually branch in a V-pattern; intervals of ramification are longest in the main branch and decrease in second- and third-order branches. Arachnostega traces were produced in a warm, low-energy, shallow-marine (<10?m water depth) environment. Polychaetes are the most likely producers of marine Arachnostega, which are commonly occurred in the same studied bed. This new occurrence is significant in extending the known stratigraphical and geographical ranges of Arachnostega into the Middle Miocene of Egypt.     

Groundwater resources evaluation in calcareous limestone using geoelectrical and VLF-EM surveys (El Salloum Basin,Egypt)

Understanding and developing groundwater resources in arid regions such as El Salloum basin, along the northwestern coast of Egypt, remains a challenging issue. One-dimensional (1D) electrical sounding (ES), two-dimensional (2D) electrical resistivity imaging (ERI), and very low frequency electromagnetic (VLF-EM) measurements were used to investigate the hydrogeological framework of El Salloum basin with the aim of determining the potential for extraction of potable water. 1D resistivity sounding models were used to delineate geoelectric sections and water-bearing layers. 2D ERI highlighted decreases in resistivity with depth, attributed to clay-rich limestone combined with seawater intrusion towards the coast. A depth of investigation (DOI) index was used to constrain the information content of the images at depths up to 100 m. The VLF-EM survey identified likely faults/fractured zones across the study area. A combined analysis of the datasets of the 1D ES, 2D ERI, and VLF-EM methods identified potential zones of groundwater, the extent of seawater intrusion, and major hydrogeological structures (fracture zones) in El Salloum basin. The equivalent geologic layers suggest that the main aquifer in the basin is the fractured chalky limestone middle Miocene) south of the coastal plain of the study area. Sites likely to provide significant volumes of potable water were identified based on relatively high resistivity and thickness of laterally extensive layers. The most promising locations for drilling productive wells are in the south and southeastern parts of the region, where the potential for potable groundwater increases substantially.

     

Caractérisation des paragenèses et des paléocirculations fluides dans l'indice d'or de Bleı̈da (Anti-Atlas,Maroc)Characterization of the paragenesis and the fluid palaeo-circulations in the gold showings of Bleida (Anti-Atlas,Morocco)

The gold showings at Bleida are hosted in Late Pan-African N50–80 °E quartz–hematite–chlorite 1 tension lenses that are related to the activity of major sinistral sub-east–west thrusts. Ores result from three superimposed stages of fluid migration. Gold occurs in microcracks offsetting the earlier minerals. Fluids evolved from COHN compositions with a saline component to boiling aqueous fluids. Pressure and temperature decreased from 50 MPa and 300 °C to less than 4 MPa and 150 °C. Thus, the gold showings at Bleida were formed in a typical geothermal (epithermal) setting, likely controlled by the Late Pan-African magmatism. To cite this article: A. Barakat et al., C. R. Geoscience 334 (2002) 35–41     

The sandstone-hosted stratiform copper mineralization at Mwitapile and its relation to the mineralization at Lufukwe, Lufilian foreland, Democratic Republic of Congo

The Lufilian foreland is a triangular-shaped area located in the SE of the Democratic Republic of Congo and to the NE of the Lufilian arc, which hosts the well-known Central African Copperbelt. The Lufilian foreland recently became an interesting area with several vein-type (e.g., Dikulushi) and stratiform (e.g., Lufukwe and Mwitapile) copper occurrences. The Lufilian foreland stratiform Cu mineralization is, to date, observed in sandstone rock units belonging to the Nguba and Kundelungu Groups (Katanga Supergroup).The Mwitapile sandstone-hosted stratiform Cu prospect is located in the north eastern part of the Lufilian foreland. The host rock for the Cu mineralization is the Sonta Sandstone of the Ngule Subgroup (Kundelungu Group). A combined remote sensing, petrographic and fluid inclusion microthermometric analysis was performed at Mwitapile and compared with similar analysis previously carried out at Lufukwe to present a metallogenic model for the Mwitapile- and Lufukwe-type stratiform copper deposits. Interpretation of ETM+ satellite images for the Mwitapile prospect and the surrounding areas indicate the absence of NE–SW or ENE–WSW faults, similar to those observed controlling the mineralization at Lufukwe. Faults with these orientations are, however, present to the NW, W, SW and E of the Mwitapile prospect. At Mwitapile, the Sonta Sandstone host rock is intensely compacted, arkosic to calcareous with high silica cementation (first generation of authigenic quartz overgrowths). In the Sonta Sandstone, feldspar and calcite are present in disseminated, banded and nodular forms. Intense dissolution of these minerals caused the presence of disseminated rectangular, pipe-like and nodular dissolution cavities. Sulfide mineralization is mainly concentrated in these cavities. The hypogene sulfide minerals consist of two generations of pyrite, chalcopyrite, bornite and chalcocite, separated by a second generation of authigenic quartz overgrowth. The hypogene sulfide minerals are replaced by supergene digenite and covellite. Fluid inclusion microthermometry on the first authigenic quartz phase indicates silica precipitation from an H₂O–NaCl–CaCl₂ fluid with a minimum temperature between 111 and 182 °C and a salinity between 22.0 and 25.5 wt.% CaCl₂ equiv. Microthermometry on the second authigenic quartz overgrowths and in secondary trails related to the mineralization indicate that the mineralizing fluid is characterized by variable temperatures (Th = 120 to 280 °C) and salinities (2.4 to 19.8 wt.% NaCl equiv.) and by a general trend of increasing temperatures with increasing salinities.Comparison between Mwitapile and Lufukwe indicates that the stratiform Cu mineralization in the two deposits is controlled by similar sedimentary, diagenetic and structural factors and likely formed from a similar mineralizing fluid. A post-orogenic timing is proposed for the mineralization in both deposits. The main mineralization controlling factors are grain size, clay and pyrobitumen content, the amount and degree of feldspar and/or calcite dissolution and the presence of NE–SW to ENE–WSW faults. The data support a post-orogenic fluid-mixing model for the Mwitapile- and Lufukwe-type sandstone-hosted stratiform Cu deposits, in which the mineralization is related to the mixing between a Cu-rich hydrothermal fluid, with a temperature up to 280 °C and a maximum salinity of 19.8 wt.% NaCl equiv., with a colder low salinity reducing fluid present in the sandstone host rock. The mineralizing fluid likely migrated upwards to the sandstone source rocks along NE–SW to ENE–WSW orientated faults. At Lufukwe, the highest copper grades at surface outcrops and boreholes were found along and near to these faults. At Mwitapile, where such faults are 2 to 3 km away, the Cu grades are much lower than at Lufukwe. Copper precipitation was possibly promoted by reduction from pre-existing hydrocarbons and non-copper sulfides and by the decrease in fluid salinity and temperature during mixing. Based on this research, new Cu prospects were proposed at Lufukwe and Mwitapile and a set of recommendations for further Cu exploration in the Lufilian foreland is presented.