الفهرس 
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Abstract
The basal sandstone varying in age from early Cambrian to lower Miocene. The more abundant basal sandstone exposures are mainly of Paleozoic age. The detailed lithostratigraphic investigations of these exposures in west and east southern Sinai, resulted in a general stratigraphic point of view, that basal sandstone in southern Sinai are represented by Araba Formation overlain by Naqus Formation. These two units were fluvially deposited and are widely distributed in the southern Sinai. where in Um Bogma area and its vicinities they are replaced by four other formations which acquire more marine aspects and contain more frequent subordinate amounts of marine shales and siltstones in addition to the sandstones. These formations from base to top are; Sarabit El Khadim, Abu Hamata, Naseib and El Adedia Formations. The whole sequence overlies with nonconformity the Precambrian crystalline basement rocks and unconformably underlies the upper Paleozoic sequence. In central southern Sinai the present Adedia Formation nonconformably overlies the Precambrian basement rocks and unconformably underlies the early Cretaceous Malha Formation. The Araba Formation nonconformably overlies the basement rocks and underlies a nonvisible unconformity surface between the Araba and Naqus Formations. where in Um Bogma area the equivalent units of Araba Formation unconformably underlie the Lower Carboniferous; Um Bogma dolostones and Abu Thora clastics. The present author shows that Naqus Formation begin to exposed in the northern area of Paleozoic basin at southeast of G.Hemeyir area (Seih W. Qarqur). The Araba Formation was assigned CambroOrdovician age and Naqus Formation was assigned late Ordovicianearly Silurian age. Naqus Formation composed of white to paleearthy yellow fine to medium and coarsegrained, well sorted, massive, laminated, and occasionally crossbedded sandstones. The basal part composed of random quartz pebbles, egglike in shape and size and haphazardly distributed in the sandstone bodies. The Naqus Formation is best developed at east Sinai. The thickness may reach to 200m at W.Saal. Malha Formation is of lower Cretaceous age and occurs as small bodies rest on the top of high mountains, peneplained basement rocks or as down faulted blocks against crystalline basement blocks in west Nuweiba area. The Malha Formation can be correlated with the early Cretaceous Hatira Formation of in southern Palestine. Sherm El Sheikh Formation is OligoL.Miocene in age and is characterized by its mottled appearance by the red, black, and yellow colours. Colouration of the sandstone cliffs is attributed to presence of manganiferous mineralizations towards the southwest direction. The sandstone is overlain by marine Miocene yellowish sandy limestone. These sandy deposits may be correlated with the continental Oligocene sandy formation of G. Ahmar in east of Cairo City. The lithofacies in the selected areas were varied from the coarse, sandy gravel interchannel fluvial deposits for sediments in the basal parts to fine, intertidal to tidal inlet facies in the top of basal sandstone sequence, which shows alternated fining upward cycles of depositions. The most abundant crossbedding type in the studied basal sandstone exposures in Um Bogma area is tabular type especially in El Adedia Formation. Tabular crossbedding is well developed in the top of El Adedia pebbly sandstone facies. While; herringbone, convolute, and trough types are restricted in the sandy facies of Abu Hamata and Nasieb Formations. Generally, there is a close relation between the directions of the paleocurrents of the sediments in the four formations of Um Bogma group. This indicates the same provenance and source Naqus Formation composed of white to paleearthy yellow fine to medium and coarsegrained, well sorted, massive, laminated, and occasionally crossbedded sandstones. The basal part composed of random quartz pebbles, egglike in shape and size and haphazardly distributed in the sandstone bodies. The Naqus Formation is best developed at east Sinai. The thickness may reach to 200m at W.Saal. Malha Formation is of lower Cretaceous age and occurs as small bodies rest on the top of high mountains, peneplained basement rocks or as down faulted blocks against crystalline basement blocks in west Nuweiba area. The Malha Formation can be correlated with the early Cretaceous Hatira Formation of in southern Palestine. Sherm El Sheikh Formation is OligoL.Miocene in age and is characterized by its mottled appearance by the red, black, and yellow colours. Colouration of the sandstone cliffs is attributed to presence of manganiferous mineralizations towards the southwest direction. The sandstone is overlain by marine Miocene yellowish sandy limestone. These sandy deposits may be correlated with the continental Oligocene sandy formation of G. Ahmar in east of Cairo City. The lithofacies in the selected areas were varied from the coarse, sandy gravel interchannel fluvial deposits for sediments in the basal parts to fine, intertidal to tidal inlet facies in the top of basal sandstone sequence, which shows alternated fining upward cycles of depositions. The most abundant crossbedding type in the studied basal sandstone exposures in Um Bogma area is tabular type especially in El Adedia Formation. Tabular crossbedding is well developed in the top of El Adedia pebbly sandstone facies. While; herringbone, convolute, and trough types are restricted in the sandy facies of Abu Hamata and Nasieb Formations. Generally, there is a close relation between the directions of the paleocurrents of the sediments in the four formations of Um Bogma group. This indicates the same provenance and source typically induced a basal horizontal shear zone. The other is low angle, detachment fault. These two normal faults are dissected by Recent strike slip movements related to Aqaba sinistral horizontal movements. The Araba beds between the two faults, form turtle backs landform. It is resulted from the effect of listric and detachement faults. In west Nuweiba area the basal sandstone bodies, form a faulted tilted blocks. Most of these faults are low angle, detachement faults and their downthrowns in the direction of the center of Aqaba rift (e.g. in W. El Saada and W.Um Zeriq). Low angle normal fault planes consist of steeply tilted hanging wall strata resting on expansive flat to gently dipping fault surfaces. The selected basal sandstone basins are dissected by numerous faults, which cut the country rocks into various blocks with different values of displacement. About, fourty four (44) minor faults in the studied basins in southern Sinai were measured in the field. The most common fault trends are, the most common fault trends are NESW, NWSE, EW, and NNESSW respectively. The point and contour diagrams show that, these minor fault planes are mainly dip in the SE, SW, E, and S directions respectively. The stresses responsible for the jointing in the Precambrian basement rocks and its overlying basal sandstones are mainly in N50620E trend and the dip angle is 570 (in average). These with the exception of basal sandstone in Ras Millan, the stress responsible for its deformation is in S210E and dipping 110. The joint analysis in basement rocks and its overlying basal sandstone shows that, there is good connection between joints in both basement rocks and those in the overlying basal sandstone units (especially in Um Bogma and west Nuweiba areas). This connection has the main role in the upwelling of ground water carrying the leachable uranium. While; in Ras Millan and G.Hemeyir areas joints moderately to poorly connected. So, the circulation of ground water is slow and discontinued.