Calcareous nannofossil biostratigraphy of the Paleocene at the Misheiti section,East Central Sinai,Egypt

Integration of calcareous nannofossil data, δ¹³C and δ¹⁸O values, and carbonate contents of the lower Paleocene–upper Paleocene sequence that crops out at the Misheiti section, East Central Sinai, Egypt, were used to denote the Danian/Selandian (D/S) and Selandian/Thanetian (S/T) stage boundaries. The study interval belongs to the Dakhla and Tarawan formations. Four calcareous nannofossil zones (NP4, NP5, NP6, and NP7/8) were recognized. The base of the Selandian Stage is tentatively placed at the lowest occurrences (LOs) of taxa ascribable to the second radiation of fasciculiths (i.e., Lithoptychius janii). This level is marked by a sudden drop of δ¹³C and δ¹⁸O values and carbonate content. No distinctive lithological changes were observed across the D/S boundary at the study section. A hiatus at the NP5/NP6 zonal boundary is indicated by the condensation of zones NP5 and NP6.The base of the Thanetian is placed at the base of Zone NP7/8 at the lithological change observed in correspondence to the boundary between the Dakhla and Tarawan formations. The δ¹³C and δ¹⁸O values abruptly decrease slightly above the base of Zone NP7/8. No consistent variations in the carbonate contents were recorded within Zone NP6 or across the NP6/NP7/8 zonal boundary.     

Uncertainty of climate change impact on crop characteristics: a case study of Moghan plain in Iran

Theoretical and Applied Climatology - Crop yield is one of the most critical factors in the food security chain. Climate plays a crucial role in crop water productivity in rainfed and irrigated...     

Shear wave velocity as function of cone penetration resistance and grain size for Holocene-age uncemented soils: a new perspective

For feasibility studies and preliminary design estimates, field measurements of shear wave velocity, V _s, may not be economically adequate and empirical correlations between V _s and more available penetration measurements such as cone penetration test, CPT, data turn out to be potentially valuable at least for initial evaluation of the small-strain stiffness of soils. These types of correlations between geophysical (Vs) and geotechnical (N-SPT, q _c-CPT) measurements are also of utmost importance where a great precision in the calculation of the deposit response is required such as in liquefaction evaluation or earthquake ground response analyses. In this study, the stress-normalized shear wave velocity V _s1 (in m/s) is defined as statistical functions of the normalized dimensionless resistance, Q _tn-CPT, and the mean effective diameter, D ₅₀ (in mm), using a data set of different uncemented soils of Holocene age accumulated at various sites in North America, Europe, and Asia. The V _s1–Q _tn data exhibit different trends with respect to grain sizes. For soils with mean grain size (D ₅₀) < 0.2 mm, the V _s1/Q _tn ^0.25 ratio undergoes a significant reduction with the increase in D ₅₀ of the soil. This trend is completely reversed with further increase in D ₅₀ (D ₅₀ > 0.2 mm). These results corroborate earlier results that stressed the use of different CPT-based correlations with different soil types, and those emphasized the need to impose particle-size limits on the validity of the majority of available correlations.     

Magmatic and metamorphic evolution of the Shotur Kuh metamorphic complex (Central Iran)

Metamorphic basement rocks, that are exposed beneath the very low-grade to unmetamorphosed Upper Jurassic-Eocene formations north of the Torud fault zone within the Great Kavir Block, were investigated to elucidate the origin of their protoliths and the pressure and temperature conditions of metamorphism. The basement, previously assumed as a pre-Cambrian metamorphic complex, is mostly formed by amphibolite-facies orthogneisses (tonalite, granodiorite, and granite) with amphibolites and small amounts of metasediment-micaschists. Major- and trace-element geochemistry in combination with U–Pb age dating of zircon showed that the protoliths formed during Late Neoproterozoic continental arc magmatism that has also been identified in other tectonic blocks of Central Iran. In addition to quartz, feldspar(s), micas in orthogneisses, and amphibole + plagioclase in amphibolite, all rocks may contain garnet that shows prograde zoning. Kyanite was found only in some Al-rich amphibolite together with gedrite. The PT conditions of the rocks, based on conventional geothermobarometry and the pseudosection method, show a medium-pressure amphibolite-facies metamorphism. Ar–Ar age dating of muscovite reveals that this metamorphism occurred in the Middle Jurassic (166 Ma) and related to the closure of the Neotethyan basin.     

Rare earth elements in metarhyolite dyke constraints on processes in a dynamic hydrothermal system,Um Ghannam,South Eastern Desert,Egypt

The Um Ghannam area lies within the core of Hafafit Complex, South Eastern Desert. This area is occupied mainly by granitic gneiss (orthogneiss). However, the granitic gneiss is extruded by swarm metarhyolite dykes and quartz veins. The studied metarhyolite dyke is classified into two distinctive zones. However, the intense degree of hydrothermal alteration can partition this dyke into weakly and extremely altered zones. According to the extraordinary diversity in color, this dyke is distinguished into gray to dark gray (weakly altered) and greenish (extremely altered) metarhyolite. Petrographical, mineralogical, and geochemical characteristics of the two distinctive zones are detected in a representative sample. Petrographically, the weakly altered zone is mainly represented by chloritization of primary biotite, garnet, and epidote, and argillitization of primary plagioclase. Although the extremely altered zone contains intensely altered remnants of the original rock, the extremely altered zone is distinguished by intense oxidation products (carbonate minerals and quartz, with significant amounts of secondary Cr-muscovite and hematite). The mineralogical studies are imposed on the millimeter and the micrometer scale in this important hydrogeothermal system. Except for Ca and Mg, most of the major elements are depleted at the extremely altered zone. However, the extremely altered zone is enriched in trace elements (Cr, Mn, Co, and Ni). The major elements of the extremely altered zone reflect the significant alterations (desilication, muscovitization, and carbonatization). These alteration processes have taken place in the hydrogeothermal system in the extremely altered zone. The geothermal fluid is responsible for these hydrothermal alterations. High fO₂ and high temperature are characteristic features of this fluid. Then, the high-field-strength elements such as Zr, Ti, and P are depleted as a significant hydrothermal alteration. Also, nuclear elements with the anion of (CO₃)^2? can travel as molecular complexes (carbonates), as long as the chemical and structural conditions are suitable for the movement of these elements from the metarhyolite dyke to redeposit and accumulate in another geologic formation. The rare earth elements La and Ce, as well as Yb and Lu, are partially mobilized during intensity alterations. The rare earth elements (REEs) are depleted in abundance with enrichment of CO₂ from the weakly altered zone to the extremely altered zone. The REE budget is decreased from the weakly altered zone to the extremely altered zone as 121.17 to (27.38???16.52), respectively. The significant depletion of ∑REEs is controlled by dissolution of monazite. Monazite breakdown and even apatite formation can be caused by alkaline fluid. This fluid is related to event and thermal stage. However, the negative anomaly of Eu can be noticed in all studied samples. Then, Eu anomaly may be formed from plagioclase fractionation. The weakly altered metarhyolite zone and orthogneiss have lower HREE/LREE (0.07–0.11), respectively, relative to the extremely altered metarhyolite zone (0.17???0.2). Even all studied samples at two significant zones are characterized by the enrichment of ∑LREEs relative to ∑HREEs.     

Land cover change dynamics mapping and predictions using EO data and a GIS-cellular automata model: the case of Al-Baha region,Kingdom of Saudi Arabia

The present study designed to monitor and predict land cover change (LCC) in addition to characterizing LCC and its dynamics over Al-Baha region, Kingdom of Saudi Arabia, by utilizing remote sensing and GIS-cellular automata model (Markov-CA). Moreover, to determine the effect of rainwater storage reservoirs as a driver to the expansion of irrigated cropland. Eight Landsat 5/7 TM/ETM images from 1975 to 2010 were analyzed and ultimately utilized in categorizing LC. The LC maps classified into four main classes: bare soil, sparsely vegetated, forest and shrub land, and irrigated cropland. The quantification of LCC for the analyzed categories showed that bare soil and sparsely vegetated was the largest classes throughout the study period, followed by forest, shrubland, and irrigated cropland. The processes of LCC in the study area were not constant, and varied from one class to another. There were two stages in bare soil change, an increase stage (1975–1995) and decline stage (1995–2010), and the construction of 25 rainwater-harvesting dams in the region was the turning point in bare soil change. The greatest increase was observed in irrigated cropland after 1995 in the expense of the other three categories as an effect of extensive rainwater harvesting practices. Losses were evident in forest and shrubland and sparsely vegetated land during the first stage (1975–1995) with 5.4 and 25.6 % of total area in 1995, while in 1975, they covered more than 13.8 and 32.7 % of total area. During the second stage (1995–2010), forest and shrubland witnessed a significant increase from 1569.17 km² in 1975 to 1840.87 km² in 2010. Irrigated cropland underwent the greatest growth (from 422.766 km² in 1975 to 1819.931 km² in 2010) during the entire study period, and this agriculture expansion reached its zenith in the 2000s. Markov-CA simulation in 2050 predicts a continuing upward trend in irrigated cropland and forest and shrubland areas, as well as a downward trend in bare soil and sparsely vegetated areas; the spatial distribution prediction indicates that irrigated cropland will expand around reservoirs and the mountain areas. The validation result showed that the model successfully identified the state of land cover in 2010 with 97 % agreement between the actual and projected cover. The output of this study would be useful for decision makers and LC/land use planners in Saudi Arabia and similar arid regions.     

Calcareous nannofossil biostratigraphy of the marine Oligocene and Miocene succession in some wells in Northern Egypt

Twelve calcareous nannofossil biozones of Late Oligocene-Late Miocene in Northern Egypt were defined and correlated with their corresponding biozones in Egypt and other parts of the world. These are arranged from the top to base as Zone NN12, Zone NN11, Zone NN10, Zone NN8, Zone NN7, Zone NN6 Zone NN5, NN4, Zone NN3, Zone NN2 Zone NP25 and Zone NP24. In the present study (Boughaz-1 Well), the Late Miocene unconformably overlies the Middle Miocene. This unconformity surface is recognized by the missing of calcareous nannofossil zones NN7 to NN9. While, in North Sinai (Malha-1 Well), the Early/Middle Miocene boundary cannot be recognized, where the Middle Miocene unconformably overlies the topmost Oligocene, and it is defined by the missing calcareous nannofossil zones NN1 to NN4.     

Natural and anthropogenic influences in the northeastern coast of the Nile delta,Egypt

Landsat enhanced thematic mapper imagery (ETM) of 2002 and aerial photography of 1955, combined with published charts and field observations were used to interpret coastal changes in the zone between Kitchener drain and Damietta spit in the northeastern Nile delta, previously recognized as a vulnerable zone to the effects of any sea level rise resulting from global warming. The interpretation resulted in recognition of several changes in nine identified geomorphological land types: beach and coastal flat, coastal dunes, agricultural deltaic land, sabkhas, fish farms, Manzala lagoon, saltpans, marshes and urban centers. Reclamation of vast areas of the coastal dunes and of Manzala lagoon added about 420 km2 to the agricultural deltaic land. About 48 km2 of backshore flats, marshes, salt pans and Manzala lagoon have been converted to productive fish farms. The main urban centers have expanded; nearly 12.1 km² have been added to their areas, and new urban centers (Damietta harbor and the New Damietta city) with total area reach of ~35.3 km² have been constructed at the expense of vast areas of Manzala lagoon, coastal dunes, and backshore flats. As a consequence of human activities, the size of Manzala lagoon has been reduced to more than 65%. Shoreline changes have been determined from beach profile survey (1990–2000), and comparison of 1955 aerial photographs and ETM satellite image of 2002 reveal alongshore patterns of erosion versus accretion. The short-term rate of shoreline retreat (1990–2000) has increased in the downdrift side of Damietta harbor (≃14 m/year), whereas areas of accretion exist within the embayment of Gamasa and in the shadow of Ras El Bar detached breakwaters system, with a maximum shoreline advance of ~15 m/year. A sandy spit, 12 km long, has developed southeast of Damietta promontory. These erosion/accretion patterns denote the natural processes of wave-induced longshore currents and sediment transport, in addition, the impact of man-made coastal protection structures.