Paleoenvironmental significance of aluminum phosphate-sulfate minerals in the upper Cretaceous ooidal ironstones,E-NE Aswan area,southern Egypt

Aluminum phosphate-sulfate (APS) minerals are present as small, disseminated crystals in the upper Cretaceous shallow marine ooidal ironstones, E-NE Aswan area, southern Egypt. Their association with the ironstones is considered as a proxy of subaerial weathering and post-diagenetic meteoric water alteration. The mineralogical composition of the ooidal ironstones was investigated by optical and scanning electron microscopes, X-ray diffraction, Fourier transform infrared and Raman spectroscopy. The ooidal ironstones are composed mainly of ooids and groundmass, both of which consist of a mixture of detrital (quartz) and diagenetic (fluorapatite, chamosite and pyrite) mineral assemblages. These mineral assemblages are destabilized under acidic and oxidizing, continental conditions. These conditions resulted from the oxidation of pyrite and probably organic matter under warm and humid, tropical climate followed the Santonian Sea regression and subaerial exposure. These pedogenic conditions promoted corrosion of quartz, dissolution of chamosite and apatite and hydrolysis of feldspars of the nearby exposed granitoids. The released Si, Al and Sr from quartz, chamosite and feldspars; Fe and S from pyrite and P, Ca and light rare earth elements (LREE) from apatite are reprecipitated as hematite, kaolinite, apatite and APS minerals from the pore fluids or along fractures. The paragenetic sequence and textural relationships of this post-diagenetic mineral assemblage indicate that hematite was formed by replacement of chamosite followed by formation of a secondary generation of pore filling chlorapatite and APS minerals and finally the precipitation of kaolinite in the remaining pore spaces. The formation of APS minerals and chlorapatite is simultaneous, but APS minerals are stable at shallow depths under acidic to neutral pH conditions, whereas chlorapatite is stable under alkaline pH conditions. Alkaline conditions were maintained at greater depths when the infiltrated acidic fluids reacted with chamosite. The APS minerals display a homogeneous chemical composition in all ironstone locations in Aswan area, corresponding to a solid solution between crandallite (CaAl₃(PO₄)₂(OH)₅·H₂O), goyazite (SrAl₃(PO₄)₂(OH)₅·H₂O), svanbergite (SrAl₃(PO₄)(SO₄)(OH)₆) and woodhouseite (CaAl₃(PO₄)(SO₄)(OH)₆) end-members. The variations in the APS mineral chemistry (AB₃(XO₄)₂(OH)₆) are essentially due to variable substitutions of Sr and LREE for Ca at the A site and limited S for P at the X site. The spatial distribution of APS minerals and their composition in the ooidal ironstones of Aswan area permitted to consider them as good tracers of physicochemical and paleoenvironmental changes, in particular those associated with subaerial exposure and pedogenesis. The post-diagenetic phosphatization and kaolinization of the Aswan ironstones decrease their economic potentiality; thus, understanding paragenetic sequence and textural relationships is essential for the iron ore beneficiation.     

Prediction of hourly actual evapotranspiration using neural networks,genetic programming,and statistical models

The complexity of the evapotranspiration process and its variability in time and space have imposed some limitations on previously developed evapotranspiration models. In this study, two data‐driven models: genetic programming (GP) and artificial neural networks (ANNs), and statistical regression models were developed and compared for estimating the hourly eddy covariance (EC)‐measured actual evapotranspiration (AET) using meteorological variables. The utility of the investigated data‐driven models was also compared with that of HYDRUS‐1D model, which makes use of conventional Penman–Monteith (PM) model for the prediction of AET. The latent heat (LE), which is measured using the EC method, is modelled as a function of five climatic variables: net radiation, ground temperature, air temperature, relative humidity, and wind speed in a reconstructed landscape located in Northern Alberta, Canada. Several ANN models were evaluated using two training algorithms of Levenberg–Marquardt and Bayesian regularization. The GP technique was used to generate mathematical equations correlating AET to the five climatic variables. Furthermore, the climatic variables, as well as their two‐factor interactions, were statistically analysed to obtain a regression equation and to indicate the climatic factors having significant effect on the evapotranspiration process. HYDRUS‐1D model as an available physically based model was examined for estimating AET using climatic variables, leaf area index (LAI), and soil moisture information. The results indicated that all three proposed data‐driven models were able to approximate the AET reasonably well; however, GP and regression models had better generalization ability than the ANN model. The results of HYDRUS‐1D model exhibited that a physically based model, such as HYDRUS‐1D, might be comparable or even inferior to the data‐driven models in terms of the overall prediction accuracy. Based on the developed GP and regression models, net radiation and ground temperature had larger contribution to the AET process than other variables. Copyright © 2010 John Wiley & Sons, Ltd.     

Facies analysis and palaeoclimatic significance of ironstones formed during the Eocene greenhouse

Lower and middle Eocene ironstone sequences of the Naqb and Qazzun formations from the north‐east Bahariya Depression, Western Desert, Egypt, represent a proxy for early Palaeogene climate and sea‐level changes. These sequences represent the only Palaeogene economic ooidal ironstone record of the Southern Tethys. These ironstone sequences rest unconformably on three structurally controlled Cenomanian palaeohighs (for example, the Gedida, Harra and Ghorabi mines) and formed on the inner ramp of a carbonate platform. These palaeohighs were exposed and subjected to subaerial lateritic weathering from the Cenomanian to early Eocene. The lower and middle Eocene ironstone sequences consist of quiet water ironstone facies overlain by higher energy ironstone facies. The distribution of low‐energy ironstone facies is controlled by depositional relief. These deposits consist of lagoonal, burrow‐mottled mud‐ironstone and laterally equivalent tidal flat, stromatolitic ironstones. The agitated water ironstone facies consist of shallow subtidal–intertidal nummulitic–ooidal–oncoidal and back‐barrier storm‐generated fossiliferous ironstones. The formation of these marginal marine sequences was associated with major marine transgressive–regressive megacycles that separated by subaerial exposure and lateritic weathering. The formation of lateritic palaeosols with their characteristic dissolution and reprecipitation features, such as colloform texture and alveolar voids, implies periods of humid and warm climate followed major marine regressions. The formation of the lower to middle Eocene ironstone succession and the associated lateritic palaeosols can be linked to the early Palaeogene global warming and eustatic sea‐level changes. The reworking of the middle Eocene palaeosol and the deposition of the upper Eocene phosphate‐rich glauconitic sandstones of the overlying Hamra Formation may record the initial stages of the palaeoclimatic transition from greenhouse to icehouse conditions.     

Using Vertical Electrical Soundings for Characterizing Hydrogeological and Tectonic Settings in Deir El-Adas Area,Yarmouk Basin,Syria

The present study is aimed at characterizing the subsurface geological and tectonic structure in Deir El-Adas area, by using Vertical Electrical Sounding survey (VES) and hydrogeological investigations, in order to determine the causes of the failure for the majority of the wells drilled in the area. The survey data was treated in three different approaches including direct VES inversion, pseudo-2D method and horizontal profiling, in order to maximize the reliability of the data interpretation. The results revealed the presence of a local faulted anticline structure at the top of the Paleogene formation, underneath the basaltic outcrops where Deir El-Adas village is situated. The appearance of this subsurface anticline structure has complicated the local hydro-geological situation, and most likely led to limitation of the groundwater recharge in the area. Moreover, the performed piezometric and discharge maps indicated the presence of a notable groundwater watershed, in addition to feeble water productivity of the wells drilled adjacent to Deir El-Adas, mostly related to the subsurface geological and tectonic settings in the area.     

The biostratigraphic and paleoecological importance of the subsurface Carboniferous microfossil assemblages from Faghur-1x well,Western Desert of Egypt

The microfossil assemblages of subsurface Carboniferous rocks from Faghur-1x were examined and identified. Their biostratigraphical and paleoenvironmental importance were investigated. The assemblage included well-preserved foraminifera like Omphalotis omphalota, Omphalotis sp. 2, Omphalotis sp. 3, Paraarchaediscus stilus, Paraarchaediscus koktjubensis, Archaediscus krestovnikovi, Archaediscus complanatus, Archaediscus inflatus, Archaediscus karreri, Diplosphearina inequalis, Eotubertina sp., Tetrataxis conica, Cribrostomum lecomptei, Palaeotextularia angulata, and Palaeotextularia longiseptata. This foraminiferal association indicates the late Viséan-early Serpukhovian. The other microfossils are gastropods, brachiopods, ostracods, crinoidal ossicles, frond-like fenestrate bryozoan types and stick-like colonies, echinoderms, microproblematica like Draffania biloba and algal Calcisphaera and the dasyclad Koninckopora. This microfossils assemblage points to the deposition in a restricted to open platform in a lagoonal framework environment. The Tehenu Basin is the eastern segment of northern African Sahara basins that provided refuge for the foraminiferal genera through the mass extinction events during the glacial Viséan-Serpukhovian times. However, its foraminiferal associations have lower diversities than the western basins, which indicate that it was more readily affected by the mass extinction event.     

A comparison of three-dimensional interpolation techniques for plume characterization

Interpolation of contaminant data can present a significant challenge due to sample clustering and sharp gradients in concentration. The research presented in this paper represents a study of commonly used interpolation schemes applied to three-dimensional plume characterization. Kriging, natural neighbor, and inverse distance weighted interpolation were tested on four actual data sets. The accuracy of each scheme was gauged using the cross-validation approach. Each scheme was compared to the other schemes and the effect of various interpolation parameters was studied. The kriging approach resulted in the lowest error at three of the four sites. The simpler and quicker inverse distance weighted approach resulted in a lower interpolation error on the other site and performed well overall. The natural neighbor method had the highest average error at all four sites in spite of the fact that it has been shown to perform well with clustered data. Another unexpected result was that the computationally expensive high order nodal functions resulted in reduced accuracy for the inverse distance weighted and natural neighbor approaches.     

Flood mapping under uncertainty: a case study in the Canadian prairies

In April 2013, a 7.0 Mw earthquake struck along the Longmen Shan fault in the city of Ya’an, Sichuan Province, China, causing serious damage. The invaluable contributions of the non-governmental organizations (NGOs) in dealing with this disaster highlighted the significance of government–NGO relationships in post-disaster reconstruction and the effect this has on the efficiency and quality of post-disaster reconstruction. This paper examines government–NGO relationships (GNR) in the post-Lushan earthquake period as a multi-stakeholder collaborative problem based on organizational lifecycle perspectives through the birth, growth, stability, and saturation stages. Two-year field research was conducted in the affected areas which identified the GNR as a bridged government–NGO relationship (BGNR) during the reconstruction period, with the Ya’an service center acting as the bridging organization. The BGNR’s experience was compared to the previous Wenchuan earthquake, and the general BGNR post-disaster reconstruction situation is discussed on two dimensions: mutuality and organizational identity.     

Impacts of climate change on soil moisture and evapotranspiration in reconstructed watersheds in northern Alberta,Canada

This study aims at developing a generalized understanding of the sensitivity of soil moisture patterns in reconstructed watersheds, in northern Alberta, to changes in the projected precipitation in the twenty‐first century. The GSDW model is applied to three watersheds using climate scenarios generated using daily precipitation and air temperature output from a global climate model (CGCM3), under A2 and B1 emission scenarios, to simulate the corresponding soil moisture. CGCM3 results indicate an increase in the mean annual temperature for Fort McMurray, Alberta of 3·3 (A2) and 2·4 °C (B1), and an increase in the predicted annual precipitation of 34% (A2) and 8·6% with A2 and B1 emission scenarios, respectively. The GSDW model is used, along with onsite historical data, to downscale A2 and B1 emission scenarios and to evaluate the future hydrological performance of the designated watersheds with respect to soil moisture deficit and actual evapotranspiration using a probabilistic framework. The forecasted maximum soil moisture deficit values based on A2 and B1 emission scenarios are expected to decrease compared to those based on the current, largely because of the expected increase in precipitation rates, associated with an expected increase in evapotranspiration. Copyright © 2011 John Wiley & Sons, Ltd.     

Contribution of the geophysical methods in characterizing the water leakage in Afamia B dam, Syria

The objective of this work was to characterize and understand the origin of the water losses problem in the Afamia B dam located at Al-Ghab basin in Syria. The survey involved various geophysical methods including a superficial electromagnetic (EM), an electrical sounding (ES) and electrical resistivity tomography (ERT). Special considerations were focused on the lake of the dam, which is currently suffering serious water infiltration and leakage through its bedrocks. The application of the ERT technique was more effective and convenient. The analysis of the integrated results of the above mentioned methods revealed a vertical serious leakage which could take place in certain locations via fractures and faults that hit the main valley and pass through the dam lake. Additionally, the presence of an alternating lithological heterogeneity between permeable and impermeable layers may lead to infiltration through the geological formations of the basin. These processes are most likely causing hydraulic connections between the Neogene superficial deposits and the underlying Cretaceous fractured and karstified carbonates rocks. Consequently, such hydraulic connections may lead to water losses and leakage throughout the dam basin. Eventually, the presence of tens of drilled wells which penetrate the Neogene and Cretaceous formations, and the existence of numerous archeological graves and subsurface tunnels complicate the situation in the study area and cause more water leakage.