tectono-stratigraphic subdivision of the clastic sequence of aswan area, southern egypt

7/28/2019 Tectono-stratigraphic Subdivision of the Clastic Sequence of Aswan Area, Southern Egypt

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Fifth International Conference on the Geology of the Tethys Realm, South Valley University, January 2010, P. 197-216

TECTONO-STRATIGRAPHIC SUBDIVISION OF THE CLASTIC SEQUENCE OF ASWAN AREA, SOUTHERN EGYPT

Khedr E.S.*, Youssef A. A. E.**, Abou Elmagd K.*, and Khozyem H. M.**Geology Department, Aswan Faculty of Sciences, South Valley University, Aswan, Egypt

** Geology Department, Faculty of Sciences, Cairo University, Giza, [email protected] AND [email protected]

ABSTRACTThe stratigraphic sedimentary sequence of the study area (7500 Km2) commenced in Cambrian period above a

weathering zone developed from the underlying Precambrian basement rocks. The weathering products can be divided intotwo lithotopes, glacial weathering soil formed during cold climate in Paleozoic times (Cambrian to Silurian) and lateriticweathering soil formed in hot hummed climate during Jurassic and Cretaceous times. The stratigraphic sequence islithologically classified into three-fold vertical-groups; from base upwards these are, the Pre Late-Jurassic Infra NubiaGroup, the Late Jurassic-Maastrichtian Nubia Group, and the Campanian-Paleocene to Recent Ultra Nubia Group. Thecomposite stratigraphic section includes nine formations separated with five unconformity planes, from base upwards theseare, Araba Formation (Cambrian-Ordovician), Gilf Formation (Upper Carboniferous), Abu Ballas Formation (Upper Jurassic -Neocomian), Taref Sandstone and Quseir Clastics (Torronian-Santonian), Dawi Formation (Campanian-Maastrichtian), andthe Maastrichtian-Paleocene Dakhla Formation, Kurkur Formation, and Garra Formation.

The area has been subjected to peneplanation since the early Cambrian time. Therefore, the palaeo-relief of thebasement rocks prior to deposition of the sedimentary sequence is not quit clear, but fault downthrown value attaining 172meter is recorded. Palaeocurrent studies and geodynamic investigations together with correlation charts of the studied 31columnar sections indicated a reversal of the Paleozoic southward-paleoslope of the Eastern Desert basin. Northward block-tilting occur prior to deposition of Abu Ballas Formation and the coevals Six-Hill Formation of Jurassic-Early Cretaceous

time. Five major fault-zones are detected in the study area namely, the N-S Pan-African trending Nile-River fault zone, the NWtrending Wadi El-Hudi fault zone of Carboniferous age, and the Middle Triassic Guinean-Nubian lineaments including threemajor fault zones running in NE (805 ) direction, cross-cutting the Nile River, forming Wadi Abu Subera fault zone, the 1stNile-Cataract fault zone, and Khour Kalabsha fault zone.

The present paper provides a generalized stratigraphic section of the study area and modulates the interrelationshipbetween sequence of tectonic events and sedimentation of the different stratigraphic formations.

INTRODUCTIONThe study area situated between Latitudes 230 30\ to 240 15\ N., and Longitudes 320 30\ to 330 30\ E. covering an area

of about 7500 km2 (Fig. 1). The term Nubian Sandstone as proposed by Russegger (1834) has been defined by the sequenceof clastic sediments rests over the hard basement rocks and covered by the upper Cretaceous phosphate beds in SouthernEgypt. This clastic sequence in south Egypt was given many names resulting into vague and loose usage of the term"Nubian Sandstone". Since the suffixes "ian" is rather indicative of a geographic name, Youssef (1957) suggested using theterm Nubia rather than Nubian. Terms like "Nubia complex", "Nubia Series", "Nubia Facies", Nubia Cycle and like were

described and adopted by many authors. Pomeryol (1968) has suggested abolishing the term despite the difficulties thegeologist will face; as the term was become so deeply entrenched into the Egyptian stratigraphy. This unit became a basketterm including rocks varying in age from Cambrian to Tertiary and assuming every possible gradation from marine tocontinental. The dilemma reached its acme when every non-fossiliferous sandstone section in the Middle East, North Africaand southwest Asia (Yemen Saudi Arabia) was equated with the Nubian Sandstone. In Egypt geologists especially in theoil sector, classified the Nubian Sandstone sequence into Nubia A, Nubia B and Nubia C.

Depending on the presence of iron ore deposits in the middle part of the sequence, Attia (1955) suggested aneconomic classification for the sandstone section of Aswan area including, Lower Group, Middle Group, and Upper Group.Following Attia (ibid), El-Naggar (1970) applied formal stratigraphic nomenclature considering the whole sequence of theEast Aswan area as on Group including three formations, Abu Aggag sandstone at the base, Timsah claystone includingiron ore beds in the middle and Umm Barmil sandstones at top. Issawi (1973) published a type section of the NubiaFormation in Sothern Egypt includes three members; Taref Sandstone at base, followed by Quseir Clastic at the middle andShab Clastics at top. Issawi et al. (2009) believe that the bed overlying the Timsah FM is coeval with the Taref sandstone andthe Quseir Clastics. The Mut FM was described by Youssef (1957) and named Quseir Variegated shale, amended by Issawi

(1973) to Quseir Clastic Member. Wadi Qubba is the lower part of Timsah FM (El Naggar, 1970) or the upper part of the BurgFm. (Geological Survey of Egypt, 1982).

The Upper Jurassic-Lower Cretaceous Abu Ballas Fm. includes the continental Six Hills Fm. at base and the uppershallow-marine proper Abu Ballas Fm. The above two formations form the base of the Nubia Formation of Issawi (1973). Thelower clastic division of Paleozoic ages (Said, 1962) have different formational names (Abdalla and Adendani, 1963), nownever considered as a part of the Nubia Formation (Issawi and Osman 1993, 1996; Issawi 2002, 2005a, b; Osman et al. 2002,2005).

More confusion arose when some authors e.g. Klitzsch (1978) called for removing the type section of the NubiaFormation from Bargat El Shab (Issawi, 1973) to Dakhla Oasis area on the assumption that the clastic section in there isthicker. Van Houten et. al., (1984) wanted to relocate the type section in the area northeast of Aswan. These authors


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Khedr, E.S. et al.198overlooked the fact that both areas i. e. Dakhla and NE Aswan, are outside the geographic realm of Nubia area where theterm has its geographic prefix and was first named by Russegger (1834) from the area. The so-called Gilf FM in Klitzsch andhis co-worker publications is a vague unit grouping units ranging in age from the Neocomian to the Cenomanian, whilst thegeological survey members described the Carboniferous rocks in Gilf Kebir area used before the original name. The LakiaArbain is a locality in Sudan whereas the Tadrart is located in south Libya. The above statement shows that the Germanteam working in south Egypt in the period (1984-1987), ignored the old stratigraphic names used by Egyptian geologists andintroduced new names, which certainly complicated the stratigraphy of the area and do not help in clearing the already

difficult sequence. The difficulty stems out from the fact that the sequence is mostly coarse clastics with minor fine beds;both are however, either poorly fossiliferous or barren of fossils. The usage of the old names introduces by erudite Egyptianscholars will certainly help the junior geologist to trace the regional variation in the stratigraphic rock units.

Fig. 1: Lithostratigraphic map of the study area showing the different lithological units.

Issawi (personal communication, 2006) believes that the bed overlying the Timsah FM (i.e. Umm Barmil Fm.) is coevalwith the Taref sandstone and the Quseir Clastics. Since these two units have priority than the Umm Barmil, it is thus

preferable to delete the last name. Similarly, the fact that all fossils identified by previous investigators in Aswan area werecollected 15 meter above Timsah Formation (Attia, 1955, Faris and Abu Zeid, 1963, El-Naggar, 1970, and Klitzsch et. al., 1987)which infer that these fossils belonging to either Taref Sandstone or Quseir formation. Hence, the term Timsah Formationshould be abandoned. By this review, the term Nubia Fm. (raised herein to Nubia Group) has a fixed stratigraphic setting andshould be used only to describe clastic bed from below the Duwi Phosphate (Campanian Maastrichtian) and from abovethe ascertained Cretaceous rocks beds in south Egypt. Moreover, the world wide extension of the Upper Jurassic-LowerCretaceous lateritic surface and the evolution of Kaolinite on the Late Jurassic surface of the African shield (Khedr, 2002)indicated that the base of the Nubian Sandstone Senso-Stricto, have developed earlier in the Late Jurassic-Early Cretaceoustime. The following phrases are quoted from Khedr (2002): In an attempt to synchronize the equatorial conditionsthroughout geological history with the consequent kaolin and bauxite products, Smith and Briden's (1977) palaeocontinentalmaps were matched with both of Szabo's et. al., (1988) worldwide aggregates of laterite bauxite and Moullade and Nairn's


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Tectono-Stratigraphic Subdivision of the Clastic Sequence at Aswan Area, Southern Egypt 199

(1978) Phanerozoic geology of the world. This comparison elucidate that during late Jurassic age extensive intracratonicbasins took place slightly after the final break-up of Pangaea (Windley, 1970), and a long period of lateritic weathering wereterminated by the development of fluvial deposits. This environments have produced basement weathering profile, includingbauxite or kaolinite or both, covered by fluviatile facies in the interior parts of Africa (Voros and Mindszenty, 1973), SouthAmerica and Asia (Wopfner, 1983). Similar weathering profiles of kaolin deposit have developed on a variety of metamorphicand igneous rocks (Khedr, 1978, 1984, 1987, 1991) and overlaid by the basal part of the Nubian Sandstone sequencesouthern Egypt.

The most common stratigraphic subdivisions previously proposed for the sandstone sequence are listed in (Table 1).The present work depends on Herds major stratigraphic subdivision of the Phanerozoic sequences in southern Egypt(1985b, 2002), as well as the approved facts being in favor of three marine transgressions occurred in the study area in latestJurassic, middle Cretaceous, and latest Cretaceous ages possibly correlative with the global sea level rises (Klitzsch et. al.,1987). The present work applies new stratigraphic subdivision depends on newly identified fossils and othersedimentological and geodynamical evidences. The Field petroleum geologists currently seeking for hydrocarbons southernEgypt are urgently needed for simple stratigraphic model can help in collocating and following the interacted facies of theclastic formation in the Nubia Region. Consequently, the studied sedimentary sequence can be tentatively divided into three-fold vertical subdivisions of unofficial groups; lower subdivision called "Infra Nubia Group" followed upwards by the "NubiaGroup" and the upper part called "Ultra Nubia Group". Every stratigraphic group includes several Formations (Table 1).

Table 1: The most common time-stratigraphic subdivisions southern Egypt

To comply with the famous term Nubian Sandstone of Russegger (1834), the Nubian Sandstone sequence Senso-Stricto" is sited herein as five formations within the "Nubia Group" which belongs to the Late Jurassic-Maastrichtian age. Itnecessarily occurs directly underneath the fossiliferous phosphate beds (Duwi Formation), but the lower limit is notcompulsory should lie directly over the Precambrian Basement Complex (PBC). There are several Paleozoic formations arediscovered recently resting above the PBC and underneath the Nubian Group (Osman et. al., 2005). However, deposition ofthe Infra Nubia Group commenced by clastic sequence of Cambrian age (Araba Fm.) followed upwards by Gilf formation ofCarboniferous age including the iron-ore of Aswan (the so called Timsah Formation, of El Naggar, 1970). Gilf Formation isfollowed upward by a period of peneplanation (lateritization and erosion) extended until the closing time of the Jurassic age


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Khedr, E.S. et al.200where local re-deposition of Abu-Balas Formation took place due to the latest Jurassic rise of the global sea level formingthe base of the Nubia Group of upper Jurassic-Maastrichtian age. The Nubia Group includes Abu-Ballas FM, and theoverlying Tarif FM, and Quseir Fm. Coeval with seven formations suggested by Klitzsch and Co-worker (1984-1987), frombase upward these are: Six Hills Formation, Abu Simple Formation, Lake Nasser Formation, Sabaya Formation, Abu AggagFM, Timsah Formation, and Um Barmil Formation (Table 1).

The "UNG" commenced with Duwi Formation of Campanian-Paleocene age east of Aswan (Issawi, 1968), coeval or

followed upwards by Dakhla Shale, Kurkur Formation and Garra Formation (Maastrichtian- Paleocene) in Sinn-El-Kaddabescarpment. The weathering zone between the Precambrian basement rocks and the overlying Nubian sandstone sequenceshave not included as a geologic unit in the stratigraphic column of Egypt (Philobbos and Hassan, 1975). It is described as apaleo-soil and distinguished as a separated stratigraphic unit named Ibyan by Philobbos and Hassan (Op. Cit). Detaillithostratigraphic and paleogeographic considerations achieved by Khedr (1978, 1980, 1984, and 2002) indicated that theweathering zone is made up of laterite zone took place underneath the Six Hills Formation of the Upper Jurassic-LowerCretaceous age forming the basal Nubian Sandstone not only in Africa but extended in south America and some Asiancountries in late Jurassic. Fossils, Gemnespermes, and microspores identified by Khedr (2002) in Kalabsha kaolin profileindicate Bajocian- Oxfordiane time. According to El-Ramly et. al., (1971) and Youssef (1996) the stratigraphic sequence ofKalabsha has classified into two sandstone members (Lower and Upper), confining the Wadi Kalabsha kaolin member andcrowned by Wadi talus and wind-blown sands. The Kalabsha weathering profile had been interpreted by Khedr, (2002) aslateritic profiles of tropical weather. On the other hand, tillite deposits of glacial environment are recorded within theunconformity zone between the Precambrian Basement rocks and the overlying basal part of the sedimentary sequence inAswan Area, implying the prevalence of glacial environment during their formation. Consequently, the Infra Nubia Groupshould be formed in different global climatic zones, whilst the Nubia Group could be formed in equatorial regions.Geological processes including peneplanation and sedimentation of the clastic sediments subsists for long period over thePrecambrian basement rocks. This period commenced in Cambrian time and extended until the deposition of DuwiFormation in Campanian to Paleocene times, lasting for more than 535 million years, forming about 91% of the Phanerozoictimes. The stratigraphic subdivision of the well-known sequence of the Nubian Sandstone as they provided by previousauthors are considered and listed in (Table 1). Consequently, the sedimentary sequence of the study Aswan-area can besubdivided into three parts, Paleozoic Infra Nubia Group, Mesozoic Nubia Group, and Cenozoic Ultra Nubia Group. Severalremnants of Paleozoic sediments could preserve into sheltered areas within the Pre-Cambrian hard basement rocks. OtherPaleozoic sequences (i. e. Nubia Group) could be re-cycled in the same Nubia Region; third clastic sediments could beformed later on above the Nubia Group (i. e. Ultra Nubia Group).

Materials and MethodsA total of 31 stratigraphic sections were erected to perform in the present work. During the field work attention was

paid to the vertical and the lateral variations of each of the units over the basement rocks, and to the paleosole horizons. Themeasured columnar sections are described and correlated in seven correlation charts and a composite-stratigraphic section

representing each of the different seven localities is prepared. Further correlation for the seven composite sections iscarried out and an idealized composite section for the whole study area is constructed. Eleven topographic mapsscale1:50,000 of the Geological l Survey of Egypt have been used (Fig. 2) to erect a geomorphological model of the studyarea.

Fig. 2: Index of the topographic sheets of the Geological Survey of Egypt scale 1: 50,000 utilized in the presentwork.

Geomorphology

To create a geomorphological model of the Aswan area, eleven topographic maps (Fig. 2) have been used. A numberof 4575 sites are considered for measurements of their elevation above the sea level (A.S.L). An isometric map and contourmap (Fig. 3-a, 3-b) have been constructed for the whole area under investigation. The isometric map (Fig. 3-a) shows gradualwestward and northward decreases in elevation and it is obviously differentiated between the spatial elevation of threeregions in the study area (low, medium, and high relief regions). The obtained isometric map and contour map of the study


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area illustrate the relative differences in elevation of the Eastern and the Western Deserts. Despite the unique thickness ofdifferent stratigraphic formations, there are large differences in elevations above the sea level (A.S.L) attaining 172 meterswhich facilitate the detection of major fault zones in the study area. It also explained the absence of some formations andrepeated unconformity planes due to peneplanation of unstable fault-blocks.

32 30`

32 45

33 00

33 15

33 45

23 45

24 00

23 30

24 15

Aswan City

Wadi Abu Subera Wadi Abu Aggage

Wadi Allaqi

Wadi Kurkur

Aswan Dam

A

B

Fig. 3: Isometric map (A) and contour map (B) portraying the relative differences in elevation of the study area above the sealevel. Note: contour intervals = 10m.

STRATIGRAPHYA total of 31 stratigraphic sections were measured and described in the present work. During the field work attention

was paid to the vertical and the lateral variations of each of the units over the basement rocks, and to the paleosolehorizons. For simplicity, and for correlation purpose, the studied area was divided into seven localities (Fig. 4). However,local names of the studied seven localities are given below: I- Kalabsha (Kaolin mine). II- Kurkur area (Kurkur Oasis, andAswan Abu Simple road). III- Area at the entry of Edfu Marsa-Alm Road. IV- East bank of River Nile (Wadi Abu Subera). V-East bank of River Nile (Wadi Abu Aggag, Gebel Taggoge area, and East Aswan Dam). VI- West bank of River Nile (WestAswan area, Agha khan area, and south of Aswan airport). VII- Wadi-Allaqi area(Wadi Dehmit- Umm Hubal sections).

To shed more light on definitions of the different stratigraphic rock units in the study area, the present workmeasured columnar sections previously studied by different workers. The measured columnar sections are described andcorrelated in seven correlation charts and a composite-stratigraphic section representing each of the different seven

localities (Fig. 4) is prepared. Further correlation for the seven composite sections is carr ied out and an idealized compositesection for the whole study area is shown in (Fig. 5).

Control on the Proposed Stratigraphic Subdivisions:The stratigraphic subdivision proposed in the present work suggests one formal "Group" of formation called the

"Nubia Group. The clastic sequence which took place over the hard basement rocks including two un-official names ofstratigraphic Groups or clusters of formations either underneath the Nubia Group (Infra) or overlying the Nubia Group(Ultra).

A- Infra Nubia Group:


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Khedr, E.S. et al.202This Group includes all clastic rocks laid over the basement hard-rocks or their weathered zone. It represents

sedimentary rocks ranging in age between Cambrian and pre-Late Jurassic age. This division includes four PaleozoicFormations described by Osman et. al.,(2002), and Issawi and Osman (2002); from base upward these are: Araba Fm.,Gbgaba Fm., Naqus Fm., and Wadi Malik Fm. It also included the so called Abu Aggag Formation which described byKlitzsch and co-worker (1974-1987) for the basal sandston in Abu Aggag Valley East of Aswan. Khedr (1985b) stated that theInfra Nubia sequence which belongs to Ordovician-Silurian age is made up of 400m thick undisturbed and recycledglaciofluvial sands and gravels, exposed near Gebel Uwinate S.W. Egypt.

Fig. 4: Key map for locations of the studied seven localities and sits of the measured lithostratigraphic sections.Notes insert represent Edfu area.

1- Araba Formation (Cambrian-Ordovician)The lower sedimentary unit of the Infra Nubia Group in the study area has different names given by different authors

namely, Abu Aggag Formation by El-Naggar (1970), Abu Aggag Sandstone by Hendriks et. al. (1984a), Basal part of theNubian sandstone sequence by Khedr (1978), Aswan Formation by Klitzsch (1984), and Facies-1 by Van Houten et. al.,

(1984). However, Khedr (2002) reported that this unit disconformably overlays the basement rocks, and is made up ofconglomerate beds or sandstone with bands of conglomerate. These beds followed upward by violet and yellow sandyclaystone or siltstone sometimes mudstone ranging between 0.5 and 10m in thickness and contains badly preserved rootsof unidentified plant fossils, and developed over the weathering zone of the underlying Precambrian basement rocks. Thepresent work offers for the first time a fossil record of Cambrian-Ordovician age for this stratigraphic unit (Fig 6-I, A &B).Consequently, the authors changed all previous formational names for these and called it Araba Formation.

In Aswan area the Araba Formation 0-22 m. thick is made up of a lentoid, fining upward sequence of coarse grained,kaolinitic, trough cross bedded arenaceous sandstone and conglomerate with many paleosole horizons. Cambrian till (Fig6-I, A) and White dacitic siltstone of Araba Formation at km-6 in Wadi Abu-Aggag and tilloid in km 35 of WadiAllaqi as well as glacially warped part forming hanging valley (Fig. 6-I, B) is recorded overlaying the weathering

zone of the Precambrian crystalline rocks (Khedr, 1978 and 1985b). According to (Issawi and Jux, 1982) the age of the


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Araba FM (previously Abu Aggag Formation) is Cambrian. The present authors recorded the occurrence of Skolithos andArchaeocyatre us (Fig. 6-I & 6-II) in sandstone bed near the top of Araba Formation, indicating Cambrian-Ordovician age.Hence, the Araba Formation and the overlying beds in the present area are equivalent to Araba, Gabgaba and Naqusformations of Osman et. al., (2002 & 2005).The top surface of Araba Formation is characterized by the presence of undulated erosion surface of unconformity planecovered by bioturbated sandy siltstone band include Calamites suckowi Brongniart (Khozym, 2006) announces thebeginning of sedimentation of Gilf Formation in Carboniferous. Identified fauna herein are Lower Carboniferous

Archaeocalamites sp. from the iron ore horizon of Km 52 of Abu Aggag valley (Fig 6-I, C) and Visean/LowerNamurian Lepidodendropsis devogediand Tomiodendron Os Trogianum from the entrance of Wadi Abu Aggag(Fig. 6-I, C&D)

This unconformity plane is in harmony with probable uplifting of the study area coincided with the Late Devonianuplifting in the Arabo-Nubian shield (Khedr, 2002). In the Carboniferous-Permian time, a relatively newer uplift took place inthe Middle East Area (Bishop, 1975; Al-Lubonn, 1988). This movement in North Africa and West-Asia has been extended untilthe Middle Jurassic (Morgan, 1968).

2- Gilf Formation (Carboniferous) Upper unit of the Infra Nubia Group. It is 10 to 22m thick sequence of the Nubiansandstone (Attia, 1955) or the Timsah Formation (El Naggar, 1970) unconformably overlies the Araba Formation. GilfFormation assigned to different ages by different authors (Table 1). The base of this unit is defined by the first appearance ofiron-ore bed in the area of the former iron mines of Aswan. However, Zaghloul et. al., (1983) recorded Paleozoic ichnofossils(Bifungites) within the Gilf Formation above the iron-ore horizon. The same ichnofossils (Bifungites) previously has beenrecorded by Khedr (1978) below the iron ore horizon at Aswan and compared with the Devonian Appalachian deposits ofUSA.

The Gilf Formation unconformably overlies the Araba Formation and is unconformably overlain by the Abu BallasFormation. Gilf Formation commencing at base by thin (0.5 to 60 cm thick) bed made up of bioturbated sandy siltstoneweathered black. It covered by shale bed of economic values, which varied laterally into oolitic ironstone beds in Wadi Abu-Aggag . This Formation is tabular cross-bedded sandstone demonstrating derivation from the north. This formation hasbeen previously recorded (before the inundation of Nasser Lake water) south of Aswan along the Nile valley, where similarbeds including ironstone bands were recorded in Kalabsha, Garf Hussein, Korosko, Abu Simple and other locations (Farisand Abu Zeid, 1963). The present authors recorded the fossils Calamites and Strotocrinus of Carboniferous age at the baseof Gilf Formation. Long time after deposition of the Gilf Formation in Carboniferous, the Abu Ballase formation took placeand followed upward by Taref Sandstone and covered by Quseir Formation, all were deposited as a hetrochronusmagnafacies. The very close similarly in rock units, facies association, besides the controversial ages determined for thenewly introduced named in the stratigraphy of the Western Desert by Klitzsch and co-worker (1984-1987), all suggestlumping several rock formations (which have no stratigraphical significance) in one rock unit which at least can be explainedon the light of the global geotectonic bases. The writers would like to emphases that the previously identified fossils ofUpper Cretaceous age collected from Aswan area (Gindy, 1965 and Khedr, 2002) all are belong to the Quseir Formation.

B- Nubia Group (Nubian Sandstone Senso-Stricto)The Infra Nubia Group is followed upwards by the "Nubia Group" rock unit of Late Jurassic-Maastrichtian age and

includes the Abu Ballas Formation, Taref Sandstone, Quseir Formation and covered by the "Maastrichtian-Recent" UltraNubia Group which started over the top of the Nubian Sandstone Senso-Stricto either by the Duwi Fm., or by the PaleoceneDakhla Shale. On this base, sedimentation of the Ultra Nubia Group starts in the Campanian to the Paleocene.

1- Abu Ballas Formation (Upper Jurassic-Early Cretaceous)The upper Jurassic-early Maastrichtian age "Nubia Group" comprises five rock units above the Carboniferous Gilf

Formation. According to Klitzsch and co-workers (1982-1987) this unit includes Abu Ballas, Sabaya, Baharya, TarefSandstone, and Quseir clastics formations. Only Abu Ballas Formation, Taref Sandstone, and Quseir Formation are recordedin the study area.

Abu Ballas Formation is made up mainly of white, friable, cross-bedded sandstone includes silicified rootlets, andtrunks of silicified wood. This formation of late Jurassic-Early Cretaceous age covered the economic kaolin deposit of

Kalabsha, SW of Aswan (Youssef, 1996). Khedr (2002) reported the presence of Jurassic microspores Classopollistorosusand Glcicheniidites species, as well as Serpulasulcata J. de C Sowerby; all are found interior pisoids at the top of theBajocian-Oxfordian Kalabsha kaolin profile (Khedr, 2002). This weathering profile was developed over the Precambriangranitic rocks by lateritization in late-Jurassic-early Cretaceous time.

2- Taref Formation and Quseir Formation


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Khedr, E.S. et al.204The term Taref Sandstone Formation has a wide distribution in the area north of Wadi Abu Aggag and in the western sideof the Nile River, and up to Gebel Sin El Kaddab along AswanGabal El Barqua area. The formation was reported below theKurkur Formation along Aswan Abu Simple Road. Hendriks et al., (1987) introduced the term Keiseba Formation to replacethe Dakhla FM which is certainly an erroneous contribution. The upper Group of Attia (1955) or the Umm Barmil and QuseirFormations of El Naggar (1970), which are replaced by Wadi Abbad Formation (El-Shazly et. al., 1974). It is also equivalent toUmm Barmil Formation of Klitzsch and Ligal Nicol (1984), and facies 3 by Van Houten et. al. (1984) is unconformably laidover the Gilf Formation. It made up of tabular planner cross-bedded; medium to coarse grained quartzose sandstone

deposited by low sinuosity streams and grads upwards to vary colored shale gradually increase in thickness northward atWadi Abbad near Edfu.

Fig. 5: Generalized stratigraphic section of the studied area


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Fig. (6-I). A": Cambrian tillite of Araba Formation at km-6 in Wadi Abu-Aggag; note boulders and cobble-sizedgravels detached from the silt-sized bed. B: White dacitic siltstone of Araba FM, at base glacially buckled partforming hanging valley to the lift of the photo unconformably overlaid by Gilf FM which unconformably capped byAbu-Ballase Fm.(west side of the old Aswans Dam). C: Archaeocalamites sp.PF 7/81-B) from the iron orehorizon of Km 52 of Abu Aggag valley (Lower Carboniferous)- (X1/4) D: Lepidodendropsis devogediJONGMANS 1954- (PF 2/86, B 384) Abu el Reesh scarp East of Aswan (Visean/Lower Namurian)- (X ). E:Bumastus (trilobite) Middle OrdovicianLower Silurian. Length 10cm. Wadi Alaqui. F: CF. Tomiodendron OsTrogianum (RADCZENKO) MEYEN 1972 (CF 5/86, B 371). Entrance of Wadi Abu Aggag. (Upper Visean/ LowerNamurian) (X ).


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Khedr, E.S. et al.206

Fig. (6-II) Identified Paleozoic fossils from the study area. A: Didymograptus murchisoni, Lower Ordovician,Stipe lenth 6 cm. B: Wilkingia elliptica (Phillips) (upper Carboniferous) (Syn. Allorisma sulcata Fleming). C:Minor trilobitomorphs- Opabinia Walcott. O. regalis Walcott (4, dorsal side) and Sidneya Walcott. S. inexoectansWalcott(9, dorsal view), both from (Middle Cambrian) reddish siltstone of Aquaba quarries north of Aswan.Widthof the photo 15 cm. D: Tentaculitesmolds (Ordovician-Devonian) El Kanayes site at Edfu-Marsa Alam road. (X1) E: Skolithos (Skolithus linear Hal) from Araba Formation consisted of approximately vertical cylenders.Cambrian trace fossils in well-cemented quartz sandstone, F: Acanthograptus (Dendroid Graptolites)Ordovician-Silurian graptolites Upper part of Araba Formation Abu el Reesh scarb east of Aswan city.


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C- ULTRA NUBIA GROUP (Paleocene-Recent)This group of rock units includes all stratigraphic formations which took place since the early Paleocene and extends

until the present time. The "Ultra Nubia Group" lumps the Dakhla Formation, Esna Formation at the eastern bank of the Niletogether with the coeval Paleocene age Kurkur and Garra Formations in the western side of the Nile as well as the followedupwards stratigraphic-formations in the study area. Issawi (1968) introduced the terms Kurkur Formation, Garra Formation,and Dungul Formation for the rock units in the Western Desert, coeval with Dakhla, Tarawan chalk and Esna shale andThebes limestone in the Nile Valley section (Table 1).

Lithostratigraphic Correlation

The Araba Formation unconformably overlies the weathering zone and represented by fining upward sequencesstarting at base by conglomerate and/or pebbly sandstone characterized by the presence of scour filling structure withrippled and bioturbated (borrowed) Skoilithos and Arkaeocythus (Cambrian-Ordovician) followed upward by cross-beddedsandstone. Unconformably resting above the Araba Formation, The provenance of Araba Formation occurs north of Aswan(Khedr, 1978). On contrast the dip direction of the cross-bedding in Gilf Formation and the overlying Quseir Formation aretowards the north implying derivation of their clastic materials from the south. To sum up, two unconformity planes aredetected in between Araba Formation and the overlying Gilf Fm. and between the top of Gilf Formation and the base of theoverlying Abu Ballas Formation and the overlying Taref Sandstone which varied northerly to form the Quseir VariegatedShale (Youssef, 1957, El-Naggar, 1971).

Infra Nubia GroupThis Group includes all Paleozoic formation which took place in the Nubia Region above the Precambrian basement

crystalline rocks and underneath the Nubia Group; indicating Cambrian-Ordovician age probably extended to Silurian age(Issawi and Osman, 1993, Issawi, et. al., 1999). Hence, the Araba Formation in Aswan area is equivalent to Araba, Gabgaba,and Naquse Formations of Osman et. al., (2002 & 2005). Above the Araba Formation there is an undulated erosional surfaceof unconformity plane covered by bioturbated silty sandstone band include Calamites suckowi Brongniart, Strotocrinus

Athyris Mccoy (Middle Devonian-Lower Carboniferous), Wilkingia elliptica (Phiillips) (upper Carboniferous), (syn. Allorismasulcata Fleming, Fig. 6) declares the beginning of sedimentation of Gilf Formation in Upper Carboniferous times. The studyarea is formed of two main rock types; the Pre-Cambrian basement hard rocks which are mainly of granitic rocks, and theoverlying sedimentary cover. The sedimentary section, 85 meter thick, commenced at base either by the Cambrian ageAraba Formation (e. g. Wadi Abu Aggag) ,or by Upper Jurassic-Lower Cretaceous Abu Ballas Formation (e.g. Kalabsha area,Khedr, 2002). The present authors recorded the occurrence ofSkolithos andArchaeocyathus (Fig. 6) in sandstone bed nearthe top of Araba Formation. Gilf Formation which encloses the Upper Carboniferous Calamites suckowi Brongniart,Strotocrinus, Athyris Mccoy(Middle Devonian-Lower Carboniferous) and Wilkingia elliptica (Phillips) of Upper Carboniferous(Fig. 6) unconformably followed upwards by the upper Jurassic-Lower Cretaceous Abu Ballas FM that unconformablycovered by Taref Sandstone that crowned by Quseir Formation.

The weathering zone in the southeastern part of the study area (at Wadi Dehmit locality, Allaqi section) attains 8.5meter in thickness and composed of a residual weathering profile developed over granitic rocks followed upward by theCarboniferous Gilf Formation. Seven cycles of coarsening upward sedimentation were recorded and interpreted asmeandering derivation from nearby granitic rocks which were hydrothermally altered due to the injection of volcanic basicrocks during the early Carboniferous. The Allaqi section most probably formed in down-faulting block within the crystallineBasement Complex during the Paleozoic Era. These blocks took place as an asymmetric intermountain graben extendedseveral kilometers in E-W direction and bounded by active faults running in NE-SW directions. Rejuvenation of faultingoccurred and volcanic swarms are recorded intersecting the basal part of the sedimentary sequence. The early basins fillcommenced with alluvial fan deposits and overlaid by repeated units of coarsening upward cycles of clastics each one 1-2meters in thickness started by ferruginous mud and capped by coarse sometimes pebbly sandstone. This sequencedocuments small-scale subsidence of the basin floor. Isotopic dating of the injected volcanic rocks indicates either earlyCarboniferous age (Cahen et. al., 1984) or Triassic-Lower Jurassic (Mineisy, 1990). On the Western Desert at Kalabsha area,the weathering profile is formed mainly of pisolitic and plastic kaolin developed over the hard crystalline rocks in LateJurassic-early Cretaceous age as documented by the presence of Jurassic microspors Surpula sulcata (Khedr, 2002). Theweathering zone is made up of two different horizons separated by sandstone bands. The lower horizon is formed of

residual kaolin whereas the upper horizon is formed of transported kaolin. Both of the two horizons were subjected tofurther lateritic weathering prior to and slightly after deposition of the basal Nubian Sandstone of the Abu Ballas Fm.(Jurassic-Neocomian).

The Infra Nubia Group in the study area is represented by three formations, from base upward these are, theCambrian-Ordovician age Araba Formation that overlies the weathering zone and formed of Kaolinitic sandstone, large scalecross-bedded sandstone, siltstone and shale, with fining upward cycles. The cross bedding direction indicate that thissandstone was derived from the north. However, the thickness of the sandstone beds of Araba Formation decreasessouthwardly. Araba Formation is unconformably overlaid by Gilf Formation. The greatest thickness of Gilf Formation (31m)is recorded in the north of the study area and gradually decreases southward. However, the Carboniferous Gilf Formation(previously Timsah Formation) is formed mainly of laminated sandstone, oolitic ironstone, and shale in two horizons: a)


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Khedr, E.S. et al.208Ferruginous shale horizon attaining 16m in thickness in Wadi Abu-Aggag, and b) Ball-clay horizon 3 meter in thicknessoccurs in Wadi Abu Subera north east of Aswan City and in a locality south of Wadi Al Kobanya north west of Aswan. Theterm "Umm Barmil Formation is ignored in the present work and is considered herein as a complementary part of GilfFormation which started at the base with the first appearance of iron-ore bed and crowned by deeply scoured surface ofunconformity. The scouring in the Carboniferous Gilf Formation sometimes deep enough to attain more than 20 meters indepth and hundreds of meters in width. Such scouring had resulted on undulatory erosional surface of unconformity iscovered at Wadi Abu-Aggag locality by a (40m) thick sequence of two separate transgressive unites started at base by 1 to

10 meter thick sequence of white sandstone belongs to Upper Jurassic-Early Cretaceous Abu-Ballas Formation. The unitcontains thin band of quartz pebbles at base and digitized lenses of subangular quartz gravels. The vector dip-direction ofthe cross-bedding is toward the north (Khedr, 1985). The sandstone unit with its basal conglomerate and White sandstonebands of Abu Ballas Formation are recorded at Km 8 of Wadi Abu Aggag in the same level with Gilf Formation whichconfines the oolitic iron ore. It is also recorded unconformably overlying Gilf Formation at km- (12) of Wadi Abu Aggag. AbuBallas Formation truncated upwards by another undulated surface of erosion characterized by pebbly conglomeratic horizoncovered by Taref Sandstone which took place in Turronian-Santonian age. Taref Sandstone is interpreted as shallow marineto aeolianbeach deposits took place during the Turronian-Santonian time and extended during most of the Campanian timeresulting in alternative sequence of sandstone beds, 0.5 to 5m thick, character of massive units sometimes cross-bedded atbase. This Formation graded at its top from fine sandstone and siltstone into shale beds representing Quseir Clastics, whichthickened northward to attain 18 meter in Km-10 of EdfuMarsa-Alam Road.

The dip directions of the cross bedding strata in both of the Araba Formation and the Gilf Formation indicating southwardpalaeo-slope of the basement rocks in the Eastern Desert and northward palaeo-slop in the Western Desert, and antigonizeddirections of clastic supplay. However, the victor dip directions of cross-bedding of Abu Ballas FM and the overlying Tarefand Quseir Formations oriented northerly in the whole study area. After deposition of the Gilf Formation fluviatile to tidalchannel environments had prevailed resulting in widespread deposition of southerly inclining cross-bedded sets of whitesandstone gravelly at base character of the upper Jurassic Abu Ballas Formation. Angular unconformity is recordedbetween the top of the Gilf Formation and the base of Abu Ballas Formation at Wadi Abu Aggag. However, as indicated byage dating Carboniferous age basaltic sheets and felsic dykes are recorded cutting across the Araba and Gilf Formations.Consequently, the eastern part of the sedimentary section of study area had experienced tectonic events. Suporting to thisview, other volcanic-extrusions of Triassic age were recorded transecting Abu-Ballas Formation in Wadi Allaqi (Cahen et. al.,1984). Moreover, palaeocurrent studies carried out by Khedr ( 1985), indicate that prior to deposition of Abu BallasFormation tectonic movement in the study area, most probably in early Triassic-lower Cretaceous times, led to the reversalin the slop direction of the large sedimentary basin only at the Eastern Desert and followed by peneplanation phase. Theresulted slop inclined northerly in the Eastern Desert, and the two previous basins of the western and the Eastern Desertsare unified in one large basin inclined northerly. To sum up, the pale slops of two large basins covering the study area andsplatted along the present site of the Nile stream in Aswan area and extended along Wadi Qena were antagonized during thedeposition of clastic sequence started in Cambrian and continued until the Lower Carboniferous. The two basins are unified

in one northerly sloping basin in the Upper Carboniferous and remained so until the present time. Prior to deposition of AbuBallas Formation further rejuvenation of tectonic movement in the study area most probably in early Triassic-lowerCretaceous times led to the completion of reversal in the slop direction of the Eastern-Desert sedimentary-basin.

Near the top of the two escarps of the Nile Valley in Aswan there are thin beds of shale belonging to Quseir Formation.These are covered by very hard quartzite bed. In the western part of the study area, the Abu Ballas Formation laidunconformably over the Precambrian Basement rocks then covered by Taref Sandstone followed upward by Wadi AbbadFormation (Quseir Fm.) which in term covered by the Dakhla shale. The Dakhla shale sequence formed of gray laminatedshale, brown to green hematitic siltstone and calcareous sandstone in the top overlaid by Kurkur Formation that is manlyformed of brown fossiliferous limestone, laterally varied in few cases to phosphatic limestone and/or oolitic limestone.Collectively; overlying the basement igneous and metamorphic rocks, the obtained stratigraphic sections are composed ofnine formations separated with four unconformity planes.

ANALYSIS OF FAULT TRENDS

Trends of fault planes were measured in the study area using geological map of Egypt (1988) and traced from theaerial photographs. A total of 324 faults and lineaments having a total length of 2195.6 km were individually measured (Fig.7) using planimeter (PLANEX 5000). Field visits and pop round for more than 200 fault plan to look into their dip andextension have been carried out. Google-Earth computer programs as well as inspections of remote sensing replicas areemployed to detect the lateral connections of the known fault planes. The obtained data were grouped into 18 azimuthclasses each equals 10 degree. The frequency of faults in the different classes is listed in (Table 2) and then plotted on rosediagram (Fig. 8).Following the work of Schandelmier, (1987) and Meshref (1990) the authors subdivided the major structure trends in thestudy area into seven regional directions which can be delineated as follows:


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1- Nubian or East African Trend (010)N: This direction (Schandelmier, 1987) forming 10.6% of the counted faults ofthe study area, the majority of which (8.7%) are oriented in the NW direction (Table 2).

2- NW Gulf of Suez Trend (30-40) NW: (Table 2) indicates that the most pronounced directions of faulting in thestudied area (20.4%) belong to Gulf of Suez trend. This trend refers to the Pan African Orogeny (670 m. y., Fenton andFenton, 1958). This fault trend seems to be reactivated again in late Oligocene and Miocene. The effect of reactivation hadbeen recorded in the post Oligocene and Miocene deposits, and oriented mainly in the (40o-50o) NW direction (Schandelmeiret al., 1988).

3- The Najd-Fault-System Trend (6010) NW: This trend took place by the closing time of Pan African Orogeny andcontinued until the Devonian times (Moufty and Khedr, 1998). Number of fault planes oriented in this trend attains 11.5% ofthe total number of faults in the study area. Many of these faults have been reactivated again as it was recorded crosscutting sediments of Cretaceous age (Table 2). The same trend was recorded by Davies (1984) in the south of the WesternDesert of Egypt.

4- Red Sea Trend (205) NNW: This trend took place during the initial phase of the Red Sea rifting (Girdler andstyles, 1974, and Khedr, 1990). This trend has most probably occurred due to tensional forces probably started in latePrecambrian times, (Veil, 1979), continued during Carboniferous as some kind of depression existed (Girdler, 1969), andextended until Cenomanian to the early Tertiary time (Guiraud, 1974, Guiraud and Bosworth, 1999). Number of fault planesbelonging to this trends form 13.2% of the total number of the counted faults. Windley, (1979) attributed this trend to domingand thinning of the continental crust in the Red Sea region and the consequent rifting phase began during the Turronian orConiacian, whilst the first major rift movement occurs by the opening date of the middle Eocene (Girdler, 1969).

Table (2): Percent frequency of the total number of fault planes classified into 18 azimuth classes.

Azimuth

classesNENWAzimuth classes2NE3NW4

%Frequency%Frequency%Frequency%Frequency

0-101.9>50-602.58.3

>10-201.28.7>60-700.73.2

>20-302.513.2>70-803.22.5

>30-402.220.4>80-902.51.1

>40-503.111.1Total19.880.2

5- NE Trans Red Sea Trend (40-50

): There are other faulting trends which formed syn-genetically with the Red Sea

trend known as the Trans Red Sea trend which runs in the NE (40-50) direction (Schandelmeir et. al., 1987). The number offault planes belonging to this trend forms 11.1% of the total number of faults in the study area.

6- Gulf of Aqaba Trend (155) NE and Gulf of Aden Trend (705) NE: These fault trends formed syn-geneticallywith Gulf of Aqaba and Gulf of Aden trend. It took place in NE 155 or Gulf of Aqaba Trend, and in NE 705 or Gulf of

Aden Trend.7- Guinean- Nubian lineament (805) NE trend: This trend most probably took place in middle Triassic time as it

evidenced by occurrence of rhyolites filling fault planes running NE 805 southern of the study area (Guiraud et al., 2001).Numerous anorogenic alkaline complexes were intruded during the early to Middle Triassic are recorded in the southern partof the study area. However, age dating of the rhyolite materials filling fault planes running 805 trend has not beendecided precisely. Following Guiraud et. al. (2001), the authors will refer the 805NE faulting trend to a wide range of time,lasting between Permian and Early Late-Jurassic. Recently Guiraud et. al., (2001) attributed the occurrence of either basalticmagmatic activity or failed rifts across many parts of Africa, including Egypt, to the late Paleozoic-Early Mesozoic rifting ofGondwanaland. They (ibid) have identified three rifting phases:

Permian-Triassic-Liassic (Late-Jurassic, and Early Cretaceous). Despite the small number of the counted fault planes(5.7%) running in 805NE direction, the length of this faults are extend enough that they form major trends in the studyarea. Three major fault groups having the same trend, extending from the Western to the Eastern Deserts crossing the Nileare inferred (Fig. 10). Many of the NE oriented faults recorded at 70km southeast of Aswan along the main valley floor ofWadi Allaqi and Aswan Baranees road are filled with volcanic rocks and/or hydrothermal materials. The extrusive rocks

filling fault zones are noticed incised in the base of the sandstone sequence. This indicates that the majority of the countedfaults (80.2%) are oriented in NW direction, 40 % out of them are trending 30 to 60 NW. N45W fault planes in the study areawere formed after the deposition of the basal part of the sandstone either in early Palaeozoic times (Osman, et. al., 2002) orMid to late Jurassic (Cahen et al., 1984 and Issawi, 2002) or in Jurassic-Neocomanian times (Khedr, 2002). However,rejuvenation and infilling of some fault plane by volcanic materials which cross-cut the basal part of the sandstone seemsthat they took place repeatedly in different ages.

The main structural events affected the southern part of Egypt including the study area can be summarized asfollows: -

Three phases of uplift and erosion of the Gebel Uweinate-Aswan uplift, accompanied with intrusion of alkalinemagmas, most probably occurred in the Permo-Triassic, Triassic-Jurassic and CretaceousTertiary times. These events arecoincided with disintegration of Pangaea and left behind anorogenic alkaline complexes which were intruded during Early to


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Khedr, E.S. et al.210Middle Triassic with other magmatic activity occurred in southern Egypt-Northern Sudan. More precisely, this trend runningin NE 805, extending between Gebel Uweinate and Abu Simple City, and on into the Eastern Desert in parallelization withGuinean- Nubian lineament (see Guiraud et. al., 2001) - In Southern Egypt rejuvenation of the older fracture systems tookplace in the eastern part, fault blocking occur in the western part, and related alkaline volcanism and formation of EW faultsystem and grabens occurs in Late Cretaceous and in the Tertiary times. Whatever the inferred events which led to thepresent structures on southern Egypt, the chronologic classification of the fault trends in North Africa according to severalauthors is listed in (Table 3).

Table (3): Chronological classification of fault trends in NE AfricaANGLETRENDAGEREFERENCE

NE 45 5Trans Red Sea TrendLate CretaceousKlitzsch (1970)

NE 80 5Guinean-Nubian lineamentTriassic-Lower JurassicGuiraud, et. al., (200111)

WNW 60 5Najd Fault TrendLate PalaeozoicDavies (1984)

NNW 20 5Red Sea TrendLate CarboniferousGirdler (1969)

NW 35 5Gulf of Suez TrendEarly CarboniferousKlitzsch (1986)

NW-NE 0 10"Nubian" or "East African"Late Pre-CambrianSchandelmeieret. al., (1988)

Fig. 7: Lineament fault-map of the study area (data from EGPC, 1987)

Fig. 8: Rose diagram of the lineament directions of fault trends, in the study area together with geneticnames of the fault trends.

The Sequence of Tectonic Events Occurred in the Study Area.

The study area can be subdivided according to the prepared contour maps into three regions (high, medium, and lowrelief) with highest elevation A.S.L. in the east and in the south, medium elevation in the central part and low elevation in thewest and in the north of the study area. According to the measured elevations of the basal conglomerate zone of thesandstone sequence in the study area, as well as the measured elevation of the barren beaks of the hard basement rocks.Figure (3) provides graphic presentation of the present relief of the land-surface of the basement hard rocks. The lineatedfault zones are named herewith according to names of localities passing within/or near it. The major NW fault-trend whichcut across all rock types in the area indicates rejuvenation of this fault- trend during the geologic history of the area. If


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peneplanation was uniquely active on whole parts of the surface of the basement rocks prior to deposition of the overlyingsandstones, the above mentioned difference in elevation of the basement rocks should be tectonically controlled. Inaddition, the predominance of the NW-SE directions of faulting in the study area (Fig. 9) with the recorded local differencesin relief (Fig. 3) attaining 250m ASL, suggests a subdivision of the study area by tentative lines into several fault blocks. Thesuggest lines are in harmony with the regional geodynamic principals of the area as previously suggested by Klitzsch andco-worker (1984 and 1987), Guiraud et. al., (1985), Guiraud (1998), Guiraud et. al., (2000), and Issawi (2000).

Lineation of regional fault-zones are also carried out herein where the extensions of fault lines are appropriate and inaccordance with: a- Presence of un-continuous fault planes in the original geological map of Egypt, where lineament ofevery two un-jointed fault lines would form one continuous fault. b- Sudden differences in elevation between adjacentlocalities having linear features, c- The probable occurrence of dry valleys that extend along the passes of two fault adjacentlines, and d- The occurrence of previously studied thick sequences of sediments filling grabens in the Pre-Cambrianbasement rocks. However, all the tentatively identified major faults which marked and named above, have been indicated inthe correlation stratigraphic charts (Khozayem, 2006), judged by the substantial differences in elevations ofmarker beds in adjacent blocks.

Fig. 9: Cross sections along AA`, BB`, CC` and DD` lines showing the present relief of the basement hardrocks with reference to elevations of the bottom of Araba Formation in the study area.

The Nile River in the study area as well as the western border of the high relief area (Fig. 3) can be tentativelybordered by two continuous zones of faulting group (Fig. 9), namely, the Nile river fault zone, and Wadi El-Hudi Fault zone.Value of vertical down-throw of the base of Araba Formation east and west of the Nile, attains 172 meter. Third fault zonetentatively running (NE-SW) in parallelism with the hedge line of Uwienat-Aswan uplift can be traced along the main valley of

Wadi-Kobanya crossing the River Nile, and extends along and just north of Wadi Abu Subera. This fault zone (Wadi Abu-Subera Fault zone) extends along the northern limit of the exposed Precambrian basement rocks in the Nile Valley at Aswanand shows the lowest measured elevation in the whole study area (Fig. 9). Fourth tentative fault-zone (The 1st Nile-Cataractfault zone) can be identified along the NE-SW direction passing just south of the Aswan 1st cataract, and to the north ofGebel El-Barqua in the Western Desert and extends until the eastern end of Wadi Abu Aggag, east of Nile. Fifth tentative faultzone could be drawn as a major fault plane along the NE-SW direction. It extends along Wadi Kalabsha, passing from thewestern bank of Lake Nasser until the southern limit of the high relief area juxtaposed Gebel Dehisa in the Eastern Desert(Khour Kalabsha Fault zone).Figure (10) is a key map to location of the proposed five fault zones in the study area. Major Fault zones assuming in NW-SEdirection or N-S direction are: 1- The Nile River fault zone, running along the Nile in N-S direction (Pan African). 2- Wadi El-Hudi fault zone, running in a NW-SE direction parallel to the general trend of uplifted mountain range of the Red Sea


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Khedr, E.S. et al.212(Carboniferous). The designated names for three fault zones running in NE-SW direction are: 3- Wadi Abu Subera Fault zoneextending in the Western Desert to join the Sciala fault (See Khedr, 2002, Fig. 1, p.696). 4- The 1st Nile-Cataract fault zone(Nubian-East African trend). 5- Khour Kalabsha fault zone. Extending in the Western Desert and join with the Kalabsha faultline. This three fault zones are pass from highly elevated localities in the south to poorly elevated localities in the north partof the study area.

Fig. 10: Outlines on the sequence of tectonic events occurred in the study area: (A) Key map to location of the Uweinat-Aswan Uplift. (B) Tentative lineament of fault zones. (C) Slopes and surface morphology of the basement rocks in the studyarea during deposition in Cambrian-Pre-Carboniferous time and tensional faults (F2) formed during late pan African timesand the followed rejuvenation of faulting and block faulting in Lower Carboniferous time (Gridler et. al.,1974). (D) Basinconfiguration of the study area during deposition of ironstone and the economic shale in upper Carboniferous time and thefollowing reverse in block tilting and subsidence followed by deposition of Abu Ballas Fm. and Qusier Fm. in Late Jurassicand Upper Cretaceous time, respectively.

SUMMARY AND CONCLUSIONSThe stratigraphic sedimentary sequence of the study area (7500 Km2) commenced in Cambrian period above a

weathering zone developed from the underlying Precambrian basement rocks. The weathering products can be divided intotwo lithotopes, glacial weathering soil formed during cold climate in Paleozoic times (Cambrian to Silurian) and lateriticweathering soil formed in hot hummed climate during Triassic-Jurassic and Cretaceous times. The stratigraphic sequence islithologicaly classified into three-fold vertical-groups; from base upwards these are, the Pre Late-Jurassic Infra Nubia

Group, the Late Jurassic-Maastrichtian Nubia Group, and the Maastrichtian-Paleocene to Recent Ultra Nubia Group.The composite stratigraphic section includes nine formations from base upwards these are, Araba Formation (Cambrian-Ordovician), Gilf Formation (Upper Carboniferous), Abu Ballas Formation (Upper Jurassic-Neocomian), Taref Sandstone andQuseir Clastics (Torronian-Santonian), Duwi Formation (Campanian-Maastrichtian), and the Maastrichtian-Paleocene DakhlaFormation, Kurkur Formation, and Garra Formation. The Araba Formation unconformably overlies the weathering zone andrepresented by fining upward sequences starting at base by conglomerate and/or pebbly sandstone character of scourfilling structure with rippled and bioturbated (borrowed) Skoilithos and Arkaeocythus (Cambrian-Ordovician) followedupward by cross-bedded sandstone (Issawi, and Jux, 1976, and Isawi, 2002, and 2005). Unconformably resting above theAraba Formation, Gilf Formation which encloses the Upper Carboniferous Calamites suckowi Brongniart, Strotocrinus,

Athyris Mccoy (Middle Devonian-Lower Carboniferous) and Wilkingia elliptica (Phiillips) of Upper Carboniferousunconformably followed upwards by the upper Jurassic lower Cretaceous Abu Ballas Formation which unconformably


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overlaid by upper Cretaceous Taref Sandstone that covered by Quseir Formation. The provenance of Araba Formation andGilf Formation occurs north of Aswan (Khedr, 1978). On contrast the dip direction of the cross-bedding in the overlying AbuBallas, Taref and Quseir Formations are towards the north implying derivation of their clastic materials from the south. Threeunconformity planes are detected in between Araba Formation and the overlying Gilf Fm. and between the top of GilfFormation and the base of the overlying Abu Ballas Formation. Third andulatory surface of unconformity occurs betweenAbu-Ballas Formation and Taref Formation that conformably covered by the Quseir Variegated Shale (Youssef, 1957, El-Naggar, 1971).

Infra Nubia Group: This Group includes all Paleozoic formations which took place in the Nubia Region above thePrecambrian basement crystalline rocks and underneath the Nubia Group. The present authors recorded the occurrence ofSkolithos and Archaeocyathu in sandstone bed near the top of Araba Formation, indicating Cambrian-Ordovician ageprobably extended to Silurian age (Khedr, 1978, Zaghloul, Z. M. et al., 1983, Issawi and Osman, 1993, Issawi, et. al., 1999).Hence, the Araba Formation is equivalent to Araba, Gabgaba and Naqus Formations of Osman et. al., (2002 & 2005). Abovethe Araba Formation there is an undulated erosional surface of unconformity plane covered either by bioturbated siltysandstone band include Calamites suckowiBrongniart, Strotocrinus Athyris Mccoy(Middle Devonian-Lower Carboniferous),or by sandstone including three mudstone horizone (all are lateraly changed eastward to oolitic ironstone) includingWilkingia elliptica (Phiillips) (upper Carboniferous), (syn.Allorisma sulcata Fleming, declares the beginning of sedimentationof Gilf Formation in Upper Carboniferous times.

Nubia Group: The Gilf Formation is unconformably overlain by Abu Ballas Formation which unconformably overlainby Taref Sandstone which graded upward to Quseir Formation (El-Shazly, et. al., 1977).

Ultra Nubia Group: This group of rock units includes all stratigraphic formations, which took place since theMaasterichtian-early Paleocene and extends until the present time. The "Ultra Nubia Group" lumps the Duwi Fm and DakhlaFormation, Esna Formation at the eastern bank of the Nile together with the coeval Paleocene age Kurkur and GarraFormations in the western side of the Nile as well as the subsequent upwards stratigraphic formations in the study area. Thegeneralized stratigraphic section indicated that Gilf Formation consists of three shale beds namely, lower; middle, and uppershale beds, all are in use for ceramics industry. On the other hand, other younger shale beds of the Ultra Nubia Grouprepresenting both of Quseir Formation of the Nubia Group and of the Dakhla Formation are not in use for ceramics industryat the time being.

The authors suggest a subdivision of the study area by tentative fault trends into several fault blocks. The suggesttrends are in harmony with the regional geodynamic principals of the area as previously suggested by Klitzsch andcoworker (1984 and 1987), Guiraud et. al., (1985), Guiraud (1998), Guiraud et. al., (2000). Figure (10) is a key map to locationof the proposed five fault zones in the study area. The designated names for these five fault zones are derived from the localnames of different five localities possessing the major ground surface extension of every zone. 1- The Nile River fault zone,running along the Nile stream in N-S direction in Aswan area. Value of the vertical downthrown of the western bank of theNile attains 130 meter relative to the eastern bank in Luxor area (Kamel, 2004). The differences in elevation between the baseof Araba Formation in the eastern and the western banks of the River Nile attains (172 meters).2- Wadi El-Hudi fault zone,running in NW-SE directions parallel to the mountain range of the Red Sea. Both of the Nile River Fault and the Wadi El-Hudi

fault zones are strike slipped westerly along the fault planes. On the other hand, three other fault zones running in NE-SWdirections, their names are designated as 3- Wadi Abu Subera Fault zone extending in the Western Desert to join the Sialafault (See Khedr, 2002, Fig 1, p.696). 4- The 1st Nile-Cataract fault zone. 5- Khour Kalabsha fault zone, extending in theWestern Desert and join with the Kalabsha fault line.The later three fault zones (Number 3, 4 and 5 above) are slipped from highly elevated localities in the south to poorlyelevated localities in the north part of the study area. Major Fault zones lineated in NW-SE directions or in N-S direction mostprobably have a close connection with the evolution of the Red Sea: The initial phase of the Red Sea rifting took place inCarboniferous (Girdler, 1974) times. This rifting phase resulted in strike slip faults trending NW-SE direction occurs eitherunder the present Red Sea water surface or forms elongate subsided fault-blocks in the study area filled by thick sediments.Thickness of sediments filling one of these greens in Wadi Baranram attains one and half kilometre (Meneisy, 2006).Moreover, NW-SE trending fault planes filled by acidic exhalative materials dated to Carboniferous (Cahen et. al., 1984) arerecorded in Umm Hubal intersecting older strata of the Infra Nubia Group. However, rifting and break-up of Gondwana alongthe Northern African-Arabian plate margin occurred in the late Carboniferous and propagated westward during the Permianand Triassic from the NE margin of the Arabian Peninsula to Morocco (Guiraud et. al., 2000).

- The first phase of Uwinate-Aswan uplift most probably had taken place during the Permo-Triassic and accompanied withNW trending faults and fault swarms running parallel and perpendicular to the length of the uplifted area (Ginean-NubianTrend, Fig. 10-A).- During Triassic-Jurassic times rejuvenation of the old NW trending fault occurred with magma filling fault planedated Triassic-Lower Jurassic (Guiraud et al., 2001) and cutting across the tillite and the overlying Gilf Formations ofCambrian-Ordovician and Carboniferous ages in the south-eastern part of the study area at Umm Hubal locality.- During Cretaceous-Tertiary times. Volcanic extrusions took place along deep seated fault planes running in E-Wand NE-SW directions in the Western Desert (Kalabsha area) parallel to the NE striking lineament of the uplifted Uwinate-Aswan area (Fig. 10-A).


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Khedr, E.S. et al.214The deposition factors controlling sedimentation in Aswan area are related to the palaeo-relief of Precambrian groundsurface, sea level changes and the structural setting of the area. The surface of the basement rocks in the Early Cambrianwas very irregular and uneven. Hence, local erosion was the essential factor controlled the formation of large number oflocal basins (Khedr, 1987), whilst, only two large basins on a regional scale took place due to NE-SW tectonically upliftedarches and NW-SE regional faulting. Comparison between the basins palaeo-slops of the Western Desert and the EasternDesert along the Phanerozoic (Khedr, 1985) indicated initiation of two elongated basins separated by a fault zone runningmostly N-S along the present site of the Nile in Aswan and extended northeasterly along Wadi Qena until the reach of the

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