الجمعة، 17 يونيو 2016

FACIES ANALYSIS AND SEDIMENTARY HISTORY OF SOME PALEO-MESOZOIC ROCK UNITS, WADI ARABA, EASTERN DESERT, EGYPT.



CHAPTER ONE
INTRODUCTION


1.1.    PRELUDE:

The Paleo-Mesozoic sediments are well exposed in the Wadi Araba area which is located in the northern part of the Eastern Desert of Egypt. Some important works on the carboniferous - Cenomanian succession in Wadi Araba area has already been published (e.g. Fourtau, 1900 & 1904; Hume 1911; Abdallah & Adindani 1963; Awad & Abdallah, 1966 and Hewaidy et al. 2003). Most of these works were essentially concerned with the paleontological considerations and the stratigraphic relationships. However, little has been paid to the modern sedimentological aspects. These aspects will be considered herein to emphasize   Paleo-Mesozoic rock units along the easternmost parts of Wadi Araba. 

1.2. THE STUDY AREA:
Wadi Araba is situated at the far north eastern reaches of the Egyptian Eastern Desert, along the western coast of Gulf of Suez. The study area lies at the northeastern corner of the northern bank of Wadi Araba (Fig. 1.1). It extends between the Lat.: 29° 22' 37"' & 29°29'15'"N and Long.: 32° 32' 42"' & 32° 14' E, Fig. (1.1).




Fig. 1.1 Satellite image of Wadi Araba including the study area.

1.3. ACCESSIBILITY:
The study area lies between Ain-Sokhna and Zaafrana areas.  The area is easily to be arrived by vehicles along the international asphaltic road run parallel to the coast of the Gulf of Suez (Ain Sokhna –Zaafrana road), Suez governorate. Inside Wadi Araba itself, the outcrops are distributed along the floor, and on both banks of the wadi. These outcrops are in form of low hills and moderate-high cliffs that can be easily walked and traversed.



1.4. AIM OF THE WORK:
The aim of the work is to examine a part of the Paleozoic-Mesozoic sedimentary succession to the north-eastern part of Wadi Araba, along the southern slopes of the Northern Galala Plateau. The detailed lithological characteristics will be discussed both in the field outcrops and in the laboratory. The different sedimentary facies forming the sedimentary succession and their mutual relationships are to be emphasized. The depositional interpretations will be given to arrive the evolution of these sediments. The tectono-sedimentary status of the given succession will be discussed in terms of the sequence stratigraphic principles.

1.5. PERVIOUS WORK:
The study area has been treated geologically long ago. Different geo-topics have been discussed since the early time of 20th Century. The following is a brief of the concerned works:
1.5.1. Stratigraphy:
Carboniferous:
The Carboniferous rocks along Wadi Araba were first discovered by Schwerin ­ Furth (1883) at the mouth of Wadi Abu Silla. Walther (1890) described the rocks in detail, especially those found opposite the exit Wadi Rod El–Hamal. The author (ibid) came to the conclusion that the marls and limestone beds of Wadi Araba having the age of “Sub-carbon" or Lower 'Carboniferous. Said (1962) supported the Lower Carboniferous (Visean) age to Wadi Araba outcrops. Abdallah and Adindani (1963) stated that the carboniferous rocks in Wadi Araba are represented by Rod El-Hamal Formation. It is best exposed in the area at the junction of Wadi Araba and Wadi Rod El-Hamal, comprising of 5 units of different lithological compositions. The whole succession is overlain by thick red shales. The authors (ibid) further added that on the basis of the corals and pelecypods present in the top parts of the Rod El-Hamal, it can be stated to be of Upper Carboniferous age. Moreover, Abdallah and Adindani (1963) considered the member 5, at the top of the Rod El-Hamal Formation as to be of Pennsylvanian age, thus the lower members may belong to the Mississippian. Adindani and Shakhov (1970) stated that in South Sinai, along Ayun Musa wells drilled for coal exploration, the clastics including the coal seams are regarded to be Carboniferous in age depending on pollen spores analysis. Kora (1995) stated that Early to Late Carboniferous in Wadi Araba is represented by Rod El-Hamal Formation.
Permo-Triassic:
Abdallah and Adindani (1963) identified and described a Permo-Triassic succession, on the basis of the badly preserved fossils, named by them to as Qiseib Formation along Wadi Qiseib in the Northern Galala Plateau-western side of the Gulf of Suez. They added that the Qiseib Formation unconformably underlies the Lower Cretaceous Malha Formation (Abdallah and Adindani op. cit.). Horowitz 1970 stated that the lower clastic red beds of the Qiseib Formation include many thin coal seams with rich palynomorphs suggesting an Early to Middle Triassic age. Druckman (1974) In Abu Hamth well-I, pointed-out that the Qiseib Formation is 376 m thick; the upper 36 m are made of limestones rich in Middle Triassic marine fossils. El Barkouky (1986) confirms a Triassic age for the Qiseib Formation in Sinai. Lejal-Nicol (1987) identified a Lower Permian flora from Wadi Araba. Kora (1992) confirmed this Lower Permian age of the Qiseib Formation due to the occurrence of the bivalves Notomya cuneata (Sowerby) and Megadesmus nobilissiinus (De Koninck). Issawi et al. (1999) further supported that the Qiseib Formation is of Permo–Triassic age, forming a transition unit between the Paleozoic and the Mesozoic.
       Early Cretaceous:
Abdallah and Adindani (1963) mapped the west side of the Gulf of Suez where they first recorded a rich Lower Cretaceous fauna in a unit below the Cenomanian beds, which they first named as the Malha Formation. Fawzi and Naim (1964) studied a 174 m Lower Cretaceous section in Gebel Shabrawet and gave an Albian age to the upper part of the Malha Formation section. Bartov and Steinitz (1977) at Arif El Naga, North Sinai, found that the Malha Formation consists of grey, white and variegated sandstones, cross-bedded and quartzitic in parts with silt interbeds and limonitic shale beds mainly in the lower part. Mazhar et al. (1979) The clastic beds of the Malha Formation unconformably overlie red shales of possibly Triassic or Permo - Triassic age and unconformably underlie the Cenomanian Galala Formation. Al Ahwani (1982) published that the Lower Cretaceous sediments are subdivided into four main rock units; two clastic units and two upper carbonate units, the lower two units are made of sandstones topped by dolomite and dolomitic limestones. El-Fawal (1988) stated that the Malha Formation along El-Tih Scarp, South Sinai is generally has Early Cretaceous age on the basis of it geometrical basis and the enclosing plant remains. The author further added that this formation is composed of two members; a lower gravelly sandstone member evolved within active braided channels, and an upper member of thick intercalation of sandstone and silt- & clay-shale paleosol evolved with a wide meandering river belt. Jenkins (1990) stated that the Malha Formation unconformably overlies Jurassic beds. Kerdany and Cherif (1990) pointed out that the lower sandstone beds formerly called as Nubia Sandstone might be Barrernian in age. Aboul Ela et al. (1991) stated that the Lower Cretaceous section at Gebel Shabrawet is correlated here with the Malha Formation and is believed to be of Albian to Varconian age, though the lower beds of this formation might belong to the Aptian or even to the Berriasian - Barremian.
Upper Cretaceous (Cenomanian):
Carozzi (1951) early stated that the Galala Plateau was interpreted as a cycle of decreasing depth of the sea. Hume (1962) noted that it is remarkable that neither Turonian nor Cenomanian formations are exposed anywhere along the northern slopes of the Southern Galala range. Abdallah and Adindani (1963) were the first who applied the name Galala Formation at the Galala massif, along the western coast of the Gulf of Suez. Al Ahwani (1982) believes that the Galala Formation in G. Shabrawet area was deposited in a decreasing water depth on an inner shelf environment.

1.5.2. Structure:
Said (1962) subdivided the continental platform area of Egypt into two tectonic domains: a northern ‘Unstable Shelf’ and southern ‘Stable Shelf’ with unstable hinge zone in between. The stable shelf is included the south of Egypt and is mainly covered by incomplete continental successions belonging to the Palaozoic and Mesozoic rocks with simple structural features (Said, 1990). Abdallah et al. (1973) stated that there are minor anticlines and synclines are recognized in Wadi Araba particularly in the Paleozoic rocks of the Rod El-Hamal locality, East Wadi Araba. According to Bandel & Kuss (1987) several structural units (blocks) can be differentiated in Wadi Araba, Fig (1.2).


Fig. 1.2 Sketch showing the geological situation in the Wadi Araba area (modified after Kuss, 1989).

Said (1990) pointed out that there was rapid lateral variation in the lithofacies of the different stratigraphic units during the Cretaceous, one of the most interesting features of the north Eastern Desert, could be due to syn-sedimentary structural control. Abdel-Aal & Lelek (1994) stated that the Galala plateaus represent a major branch of the Syrian Arc in the Eastern Desert. It is characterized by Late Cretaceous uplift in the north, and subsidence farther to the south. Folding &/or uplift of the Syrian Arc began in post-Cenomanian times.
Stampfli et al. (1995) stated that the complex uplifts and domal anticlines of the Syrian Arc Fold Belt were formed during the closure of the Neotethys. Kuss et al. (2000) stated that the North eastern Egypt is situated at the northern edge of the African- Arabian Craton. It was affected during the Late Cretaceous to early Tertiary times by east- northeast-oriented dextral wrench-faulting. This resulted in transpressive movements and the inversion of the Late Triassic – Liassic half-grabens that cut east-northeastward across the northern rim of the African-Arabian Plate. Kuss et al. (2000) stated that the folding &/or uplift of the Syrian Arc began in post-Cenomanian times, reached its acme during the Late Cretaceous, Fig. (1.3).

 

Fig. 1.3 The tectonic features in northeast Egypt showing the distribution
of the Syrian Arc System (modified after Kuss et al., 2000).

1.5.3. Tectonics:
The Galala mountain complex represents an isolated late Cretaceous (Maastrichtian) to Eocene carbonate platform at the southern margin of the Tethys, which is referred to as the unstable shelf of northern Egypt (Youssef 2003). The evolution of the carbonate platform is connected closely to the tectonic activity of the ENE–WSW striking Wadi Araba Fault, which forms part of the Syrian Arc-Fold-Belt (e.g. Krenkel 1925; Moustafa and Khalil 1995; Hussein and Abd-Allah 2001). During the Early Eocene, a major phase of tectonic activity occurred along the Syrian Arc-Fold-Belt (Shahar 1994). Regional uplift and subsidence triggered the formation of ENE–WSW striking basins, submarine swells and subaerially exposed plateaus on the unstable shelf (Said 1990; Schütz 1994). According to regional tectono-sedimentary constraints, three major depositional units can be distinguished; (i) the Northern Galala/Wadi Araba High (NGWA), (ii) a transitional slope zone, and (iii) the Southern Galala Sub-basin (SGS). The NGWA represents shallow-marine to probably subaerially exposed inner platform environments. Due to the syn-sedimentary monoclinal uplift, an erosional phase started since the Late Cretaceous, thus major inner-ramp deposits were eroded or intensively altered (Moustafa and Khalil 1995). The Rocks of the northern platform interior are intensively affected by tectonic displacement, which is a result of the Miocene opening of the Gulf of Suez. The connection between the NGWA and the SGS is represented by a transitional slope zone (mid ramp to outer ramp).
The Galala Mountains are tectonically and depositionally linked to the monoclinal structure of Gebel Somar on west-central Sinai (Moustafa and Khalil 1995). Both structures were separated during the rifting of the Gulf of Suez in the Late Oligocene and Miocene. Formation and evolution of carbonate platform systems are strongly controlled by eustatic sea-level changes and the activity of adjacent tectonic provinces (Bosellini 1989; Everts 1991).
Based on the Paleocene record of the Galala platform, (Scheibner et al. 2003) assume a platform evolution that is affected more by local tectonic displacements than by eustatically controlled sea-level changes. Thus, the tectonic activity along the Wadi Araba Fault system triggered the initial growth of the Galala platform as a coupled effect of sea-level drop and local tectonic uplift. The geometry and architecture of platform and slope have undergone repeated changes since the Cretaceous due to the varying tectono-sedimentary constraints on the unstable Egyptian shelf (Meshref 1990; Schütz 1994; Youssef 2003).

1.5.4 Geomorphology:
These structural features control the geomorphology of the study area, where Wadi Araba is bounded in the north by the Northern Galala Plateau, in the south by the Southern Galala Plateau and in the east by the Gulf of Suez.Wadi Araba has NE – SW direction, following the direction of a regional Syrian Arc anticline structure. Wadi Araba is relatively low compared with the great heights of the surrounding plateaus (Fig. 1.4). It reaches 30 km width from north to south and extends westward to the central Eocene limestone plateau of the Eastern Desert. It is traversed by a large number of drainage lines. Some of these drainage lines are shedding from the two Galala (NW – SE and SE – NW), forming tributaries of the main WSW – ENE drainage line of Wadi Araba.Most of these drainage lines are filled with Plio – Pleistocene deposits (gravel or loose sands) that were transported from the limestone cliffs by the tributary branches.

1.5.5. Paleogeography:
Said (1990) stated that the first major marine transgression in the Cretaceous occurred during the Aptian in response to a world-wide rise in sea-level. Kuss & Bachmann (1996) added that the Albian sea encroached further south due to the rising of sea-level, resulting in conformable Aptian-Albian successions in northern Sinai, while in the south, the Albian sequences unconformably onlap Aptian and pre-Aptian siliciclastics. Furthermore, during the Cenomanian, the



 



Fig. 1.4: The drainage system and elevation of Wadi Araba and the bounding Galala plateaus
(modified after Conoco, 1987).

ongoing rise of the sea-level corresponds to a Tethyan-wide high stand (Philip et al., 1993). Kuss & Malchus (1989) further added that the Late Cenomanian shelf facies of the Eastern Desert and northern Sinai is characterized by a rich assemblage of benthic foraminifera and ammonites of the genera Neolobites and Vascoceras. During the Turonian, Bauer et al. (2003) pointed out that in the Eastern Desert, shallow-marine, siliciclastic and terrestrial conditions prevailed during the relative sea-level lowstand across the Turonian – Coniacian boundary. Kuss & Bachmann (1996) reported a wide calcareous succession of an open marine chalk and chalky limestone sediments of Campanian–Maastrichtian transgressive phase.  The authors (ibid) stated that these sediments are widely distributed over the southern Egypt and Sinai. Said (1990) further added that by the end of the Cretaceous, during the Maastrichtian, the transgression reached further to the south and covered wide areas mostly with thick chalk-marl units, shale, and subordinate silts of deeper shelf origin.







CHAPTER SEVEN
SUMMARY AND CONCLUSIONS
The present study is concerned with the Paleo/Mesozoic sedimentary succession exposed at the entrance of Wadi Araba along the southern scarp of the Northern Galala Plateau, west of the Gulf of Suez. Detailed field studies were under-taken to establish the vertical and lateral changes in the lithology, the geometry of sedimentary bodies, the enclosing sedimentary structures, and the paleocurrent characterizing the examined succession.
The results of these investigations have provided some conclusions which are summarized in terms of the (1) lithostratigraphy, (2) sedimentary facies analysis, (3) depositional interpretations, and (4) depositional history of the examined rock units.
7.1. ROD EL-HAMAL FORMATION:
7.1.1. Lithostratigraphy:
In the study area as well as the Gulf of Suez region Rod El-Hamal Formation representing the time span of Upper Carboniferous age. Its lithology ranges from coarse-grained sandstone and gravelly sandstones to shales, with occasional basal conglomeratic deposits at the contact with underlying basement rocks.
7.1.2. Sedimentary facies analysis:
The lithological successions represented within the different units of the Rod El-Hamal Formation in the study area have been subdivided into 3 lithofacies associations which have been identified by means of their lithology, geometry, grain size and sedimentary structures. These facies include; Crudely-bedded, Monomineralic Conglomerate, Cross-stratified Sandstone, and Fine-laminated gray to black silt-shale.
7.1.3. Depositional interpretations:
The facies analysis done for Rod El-Hamal Formation in the study area have provided that the formation was deposited as a result of mild marine transgression advanced over the unconformable contact with the underlying basement rocks. the sediments were collected within shallow intertidal foreshore as mixed sandy/muddy tidal flat.
7.2. THE QISEIB FORMATION:
7.2.1. Lithostratigraphy:
In the study area, the Qiseib Formation represents the depositional episode of Permo-Triassic age.  Its lithology varies between gravelly sandstones to mudstones and claystones. The Qiseib Formation exhibits different colors including white, yellow, gray, green, chocolate-brown, deep violet, olive, and red mottling with variable sedimentary structures. Features of subaerial exposure, including mottling and iron crusts in the siltstones and claystone of the formation are common. The rock succession of the examined formation displays definite depositional stacking regime in form of regular successive fining-upward sequences.
7.2.2. Sedimentary facies analysis:
The Qiseib Formation is divided into three major lithofacies, each of which is characterized by specific lithology and sedimentary structures. These lithofacies are recorded within the rock succession of the examined formation displaying definite depositional stacking regime in form of regular successive fining-upward sequences. Each sequence varies in thickness from 2.0 m to about 5.0, and commences with lag-conglomerates, whereas terminates by the mudstones /mud-shales. These sedimentary facies include basal conglomerates trough cross-stratified sandstones, and varicolored, mottled silt-shale.
7.2.3. Depositional interpretations:
Based upon the sedimentary facies analysis done for the Qiseib Formation in the study area, it can be concluded that the formation was deposited under continental fluvial environment within a wide belt of meandering rivers.
7.3. THE MALHA FORMATION:           
7.3.1. Lithostratigraphy:
The Malha Formation crops-out throughout the regions of south Sinai, southeast Sinai, north Sinai, north central Sinai and west of the Gulf of Suez. It overlies rock units of different ages indicating a major erosional phase prior to Malha deposition.
In the study area, the Malha Formation is subdivided into two members; the Lower Member is gravelly sandstones, whereas the Upper Member is sandstone/mudstone intercalation.
7.3.2. Sedimentary facies analysis:
The lithological successions representing the different units of the Malha Formation in the study area have been subdivided into six sedimentary facies; which have been identified by means of their lithology, geometry, grain size, sedimentary structures and paleocurrent patterns. The Lower Member of the formation consists of four sedimentary facies; including clast supported conglomerate association, large-scale, trough cross-stratified gravelly sandstone, large scale, planar tabular cross-stratified gravelly sandstone, and horizontally laminated sandy mudstone. The Upper Member, on the other hand, consists of two sedimentary facies including; large-scale, epsilon and trough cross-stratified sandstone and rooted and burrowed sandy-mudstone.
7.3.3. Depositional interpretations:
The precise study of the different lithofacies associations has led to the interpretation of the depositional environments of each of the units as follows:
The sedimentary facies of the Lower Member of the Malha Formation includes gravelly sandstones and mudstones which are stacked in fining upward sequences. These were deposited as successive, widespread fluvial, gravel-rich sandy sheet-floods. These sheet-floods were laid down within an extensive fluvial network of low sinuosity braided streams running in a N, NE and NW directions under the influence of a relatively high paleoslope. Deposition had taken place near to the hinterlands in the areas dominated by channel influence.
The sedimentary facies of the Upper Member were formed as bedforms deposited mainly by high sinuosity meandering streams, forming point bars and flood plains. Flood plains were later subjected to subaerial conditions and developed completely or partially into prolific paleosols.

7.4. THE GALALA FORMATION:
7.4.1. Lithostratigraphy:
In the study area, the Galala Formation overlies unconformably the Malha Formation. The upper boundary of the Galala Formation with the overlying formations is generally conformable relations.
Galala Formation is represented by ~60 m thick of intercalation of shales, sandstones, limestones, dolostones, and marly limestones with the characteristic Cenomanian fauna. The basal parts, just overlying the lower contact, the shales of the Galala Formation are rich in glauconite acquiring the shale an egg-yellow colours.
7.4.2. Sedimentary facies analysis:
The lithological successions represented within the different units of the Galala Formation in the study area have been subdivided into five microfacies associations which have been identified by means of their petrographical composition:
 (1) Dolomitized Dismicrite Association: Basal parts of the Galala Formation consist of thick hard massive faint yellow limestones interbedded with thinner vary colored shale layers, these limestones are consisting of homogenous pale grey lime-micrite.
(2) Ostracodal biomicrite Association:  thick intercalation of grey, medium hard limestone beds, and thin highly fissile vary colored shale intervals, and rich with many animal bioturbations.
(3) Foraminiferal biomicrite Association: recorded at the lower part, consists of hard light grey argillaceous limestone with reddish brown bands showing different types of animal burrows.
(4) Dolomitic quartz arenite Association: recorded at the lower and upper parts, consists of hard, compact, sheet-like beds of brown sandstone beds vary in thickness intercalating with shale beds at the upper parts.
(5) Gypsiferous feldspathic quartz arenite Association: recorded at the uppermost part, consists thick, hard, compact and massive sandstones.
7.4.3. Depositional interpretations:
The precise study of the different lithofacies associations has led to the interpretation of the depositional environments of the given unit as a sedimentary product of shallow transgressive sea conditions evolved with the marine transgression covered the northern parts of Egypt during the early Cenomanian. the sediments were deposited in the realm varying between supratidal and intertidal foreshore to inner shelf depositional settings.
7.5. THE DEPOSITIONAL EVOLUTIONARY PHASES OF THE PALEO-MESOZOIC SUCCESSION IN THE STUDY AREA
The foregoing sedimentological analyses have enabled that the examined Paleo-Mesozoic succession in the study area was developed through a series of depositional phase events that can be summarized as follows:
- Pre - Carboniferous phase
- Carboniferous phase
- Permo-Triassic phase
- Jurassic-Early Cretaceous phase
- Late Cretaceous (Cenomanian) phase



Full Essay 

https://www.dropbox.com/s/w5mkopxksub4lkm/FACIES%20ANALYSIS%20AND%20SEDIMENTARY%20HISTORY%20OF%20SOME%20PALEO-MESOZOIC%20ROCK%20UNITS%2C%20WADI%20ARABA%2C%20EASTERN%20DESERT%2C%20EGYPT.pdf?dl=0