الفهرس 
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Abstract
The present study deals with an area located in the Central Eastern Desert. It lies between latitudes 25?12? to 25? 32? N and longitudes 34? 10? to 34? 50? E. Satellite data including landsat thematic mapper (TM) has been processed and Satellite images have been produced. Visual interpretations of these images yield a number of photomaps such as geomorphologic, geologic, structure, drainage network and drainage basins. Also, different information have been extracted from topographic maps.
Field verification, measurements, and laboratory analyses have been used to increase the accuracy of these maps
Geomorphologically, the area could be classified into different geomorphologic units including:
Denudation landforms as mountains (Umm Naqqat and Abu Daib), denudation hills, mesas and cuestas.
Deposition landforms, which include alluvial fans, terraces, karst, badlands, sandsheets, and wadi deposits.
Coastal plain, which include shores, beaches, lagoons, islands and coral reefs.
The water resources in the investigated area could be classified into surface, ground and desalinated waters. To study the surface water, the drainage network map of the study area has been prepared that the investigated area includes nine drainage basins. The morphometric parameters of four of these basins were calculated (Wadi Mubarak, Wadi Buwal, Wadi Shuni and Wadi Murrain). Both linear and real parameters are considered including: drainage segments (total number and length, frequency, and density), basin area, basin perimeter, valley length, relief, circularity, elongation, basin order, weighted mean bifurcation ratio, valley index, length of overland flow, relief ratio, and ruggedness number. These parameters have different values concerning with the amount of surface runoff, causing flash flooding. They are also controlling the amount of groundwater recharge probability. Available data on groundwater in the investigated area is represented by about six hand-dug wells. One of these wells is abandoned (Bir Bariq well). Three of these wells are producing brackish water (Mubarak, Um Huitat and El Nabi), while two wells are producing saline water (Ain Asali and Abu Ariki). Desalinated water is produced by a number of desalinating units, which were recently installed on the Red Sea shoreline in order to fulfil the domestic purposes.
Visual interpretations of the landsat thematic mapper (TM) images and field verification revealed the occurrence of different basement and sedimentary rock units. The igneous rocks could be classified into ophiolites and related rocks, metasediments, metavolcanics, gabbro-diorite group, older granitoid and younger granitoid. Most of the sedimentary rocks exposed in the area belong to the Miocene and Quaternary age. These rocks have been separated from the satellite images and checked during the field trips and two stratigraphic successions have been measured in some localities. The post Miocene deposits include organic reefs, raised beaches and Wadi deposits.
Two stratigraphic successions were measured and studied at two localities namely, Wadi Mubarak and Wadi Shuni. The following formations arranged from older to younger Gebel El Rusas, Abu Dabbab, Samh, Gabir, Shagra, Organic reefs, Raised beaches and Recent reefs.
Gebel El Rusas Formation rests unconformably on the basement rocks. It consists of two members, the lower member only present at Wadi Mubarak. It measures 0.5 to 1.0 m thick at Wadi Mubarak. The upper member is cropping out all the area. Its thickness in the studied successions measures 2.5 m thick at Wadi Mubarak and 2.0 m thick at Wadi Shuni. Petrographically, the Lower Member of this formation is formed mainly of conglomerates, while the Upper Member is composed of conglomerates with thin claystone and pebbly sandstone intercalations. The conglomerates are described as extraformational conglomerate. Microscopically, it is composed of coarse to very coarse, rounded to subrounded heterogeneous quartz grains (40 – 50 %), rock fragments form about 10 - 20 % of the rock constituent and represented by plutonic and volcanic rock types and few feldspar, all components are cemented by sparry calcite. The roundness of the grains and presence of calcite cement suggesting that this bed were deposited by marine wave action (Youssef and Abu Khadra, 1984).
Abu Dabbab Formation overlies conformably on Gebel El Rusas Formation. It consists mainly of gypsum. Its thickness in the studied successions measures 20.5 m thick at Wadi Mubarak and 22.0 m thick at Wadi Shuni. Petrographically, the Abu Dabbab Formation consists mainly of gypsum. Gypsum shows small to large fibrous and interlocking crystals with relics of anhydrite laths. The presence of anhydrite laths with gypsum provides evidence that this gypsum may be formed by replacement of anhydrite. Such replacement may be occurred during early diagenetic stage at tidal flat area in which anhydrite is precipitated by evaporation. The dominance of evaporite minerals may indicate a back reef, lagoonal environment.
Samh Formation overlies unconformably the Abu Dabbab Formation. It consists mainly of thick bed of sandstone followed by calcareous claystone and shale intercalation with thin bands of gypsum. Its thickness in the studied successions measures 6.0 m thick at Wadi Mubarak and 8.0 m thick at Wadi Shuni. The petrographical study indicated that the Samh sandstone composed of quartz arenite followed by lithic wacke. Sandstones are composed of quartz and feldspar grain scattered in anhydrite cement. Anhydrite is mainly found in the form of parallel laths between the quartz and feldspars grains with relics of gypsum. This microfacies deposit at supratidal zone (Abu Khadra and Wahab, 1984). The calcareous claystone and shale, which dominate at the southern part of the area and which are associated with the sandstone, represent a winnowing out of finer material from coarse sandstone debris, and its deposition represents quieter phases of the same general conditions which produced the sandstone deposits (Kurmbine and Sloss, 1962). It is interesting to notice that during the time of deposition of the Samh Formation, there was a gradual decrease in the depth of the sea from intertidal to agitated shallow water (Vail et al., 1977).
Gabir Formation overlies conformably over Samh Formation. It consists mainly of sandstone successions. Its thickness in the studied successions measures 2.2 m thick at Wadi Mubarak and 2.0 m thick at Wadi Shuni. The petrographical study of the upper part of the Gabir Formation is described as lithic arenite. It is composed of quartz grains, rounded to subrounded, medium to coarse and moderately sorted. The quartz grain enclosed by sparry calcite cement. Sparry calcite exhibits aggrading neomorphism of the primary lime mud. This microfacies may be deposited in subtidal zone (Vail et al., 1977). The presences of some casts of pelecypoda in the Gabir beds indicate marine deposition, which may be deeper than the Samh Formation.
Shagra Formation conformably overlies the Gabir Formation. It consists mainly of limestone. It measures 8.0 m thick at Wadi Mubarak and 10.0 m thick at Wadi Shuni. The Shagra Formation is described as biopelsparite. Most peloids are of fecal origin and have a regular shape and they are rich in organic matter. They are most common in the sediments of protected environments such as lagoons and tidal flats. The sediment is closely packed suggesting that compaction occurred before significant precipitation of microsparite cement filling the pores. Cementation was followed by dolomitization process replacing the calcite matrix by finely crystalline dolomite. The presence of euhedral crystals of dolomite indicates that the replacement was incomplete. Microfacies associations for Shagra Formation are characterized by shallow water depositional environment (Said, 1990).
Pleistocene organic reefs cropping out at the two localities. It consists of limestone. Its thickness in the studied successions measures 6.0 m thick at Wadi Mubarak and 5.0 m thick at Wadi Shuni. The Pleistocene organic reefs are described, as biolithite referring to limestone formed in situ, such as reef rock. As a result of recent geological events (in particular the Pleistocene glaciation), shallow marine carbonates are not so widely developed. In the past shallow epeiric seas periodically covered vast continental areas so that limestone was deposited over thousands of square kilometers. The presence of microsparite gives an indication on low energy environment (Tucker, 1984).
The Recent reefs cropping out at the two localities. It consists of limestone. Its thickness in the studied successions measures 7.0 m thick at Wadi Mubarak and 5.0 m thick at Wadi Shuni. The petrographical study indicated that limestone is composed of algal biosparite, biosparite and biomicrite. The rock present as completely preserved microfossils and shell fragments embedded in micrite matrix and / or sparite as cementing material. The majority of fossils are filled by sparite and enveloped by micrite at late diagenetic stage. Microfacies associations for Recent reefs are characterized by shallow water depositional environment (Said, 1990).
The structural elements affecting the area have been identified. These elements include bedding structures (parallel and cross lamination, ripple marks, gradded bedding and mud cracks), fractures, joints, folds and faults of different trends mainly NNW and ENE.
Mechanical analysis of studied sands reveals that 12 samples are unimodal (i.e., well sorted) and 8 samples are bimodal (i.e., moderate sorted). The cumulative curves of the studied sandstone seem to represent river sands, since the central parts of the curves have a gentle slope.
Mean size for the studied sand samples show that the mean size values of Gebel El Rusas, Raised beaches and Terraces are coarse sand, Samh and Gabir formations are medium sand, Wadi deposits and beach sands are fine sand. The inclusive graphic standard deviation values indicate that sandstone samples of Wadi deposits and beach sands are well sorted and Samh and Gabir formations are moderately sorted. While samples of Gebel El Rusas, Raised beaches and Terraces are poorly sorted. The inclusive graphic Skewness (SKI) values show that the values rang from 0.3 to 1.0 thus indicating that most samples are fine skewed, near symmetrical and small samples rang from 0.27 to – 0.01 thus indicating coarse skewed, near symmetrical. The kurtosis values show that values rang from 0.67 to 1.74 thus indicating that most samples are platykurtic to very leptokurtic.
A plot of standard deviation against mean size of the most samples shows no general trend of variation, while some samples shows V- shaped (i.e., small rang grain size).
The scatter plot diagram of the main size against skewness shows 6 samples of negative sign (i.e., coarse skewed) and 14 samples of positive sign (i.e., fine skewed).
Mineralogical study of sandstone samples reveals that the light fractions are formed mainly of quartz and feldspars represented by few grains of orthoclase and plagioclase. The heavy fractions of the studied samples are composed of opaques (> 70 %) and non-opaque heavy minerals. The non-opaque heavy minerals are composed essentially of rutile, tourmaline, zircon, epidote, anatise, chlorite, mica (biotite and muscovite), amphiboles (hornblende), Pyroxenes (hypersthene) and garnet arranged in decreasing order of abundance. The abundance of stable heavy minerals (rutile, tourmaline and zircon) favours that sandstone samples are mature. The presence of euhedral and rounded zircon and tourmaline reflects the mixing source of these sandstones or reworking from older sediments. Sato diagram showed that some of sandstone samples are of granitic source and others refers to crystalline schist origin.
In order to estimate the maturity of the concerned sediments, some heavy mineral ratios were calculated. These are zircon/tourmaline, zircon / rutile and zircon / rutile + tourmaline. In addition, the degrees of weathering were estimated. These are Wr1 (pyroxene +amphiboles)/ (zircon + tourmaline), Wr2 (hornblende)/ (zircon + tourmaline) and Wr3 (biotite)/ (zircon +tourmaline). The results revealed that the studied samples of Miocene and Pleistocene age are generally mature and highly weathered; evidenced by the relative abundance of the ultrastable minerals whereas recent sediments of Quaternary age are immature. The values of the degrees of weathering (Wr1, Wr2 and Wr3) of the concerned sediments decreased progressively from Miocene to Quaternary sediments.
The land resources in the area have been studied including mineral deposits, ornamental stones, and building materials. The area is very rich in mineral deposits, which include; those associated with ultramafic and layered mafic rocks (as chromate and copper – nickel- cobalt deposits), granites (tin, tungsten, nubian – tantalium, beryllium, fluorite and uranium), in addition to precious and base metal vein type deposits (gold and barite veins), metamorphic rocks (iron and cinnabar), sedimentary sequences (zinc-lead, sulfur, gypsum, limestone, placers and uranium). Clays, sands, gravels and limestones can be used as building materials. Also different type of granites can be used as ornamental stones.