الفهرس 
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Abstract
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CbapterV
Summary and Geological History
The impact of global forces on the history of the sediments in the studied
area in particular and on the Africa-Arabia plates in general has been
generally overlooked by most workers in Egypt. The transgressions and
regressions of the seas over the plates were not probably governed by
rise and fall of sea levels, instead by renewed uplift of source areas and
variations in a continuous detrital input linked to tectonism along the
continental margins (Sloss, 1979) and within the craton (VanHouten,
1980) with no necessary changes in s~a level. Both extremities are a.
fault- the savoir faire- has to take in consideration both sea levels
changes and tectonism.
The history of the exposed sediments in the study area is greatly ruled
by the geodynamics of the concerned plates, their diverging and
converging settings. The progressive fragmentation of Gondwana began
during the Late Carboniferous-Early Permian and Triassic times
following the Variscan orogeny (Guiraud, 1995). Associated with this
phase of crustal dissociation, at the close of the Paleozoic Era, several
geosynclinal seas were developed, the most important in the
Mediterranean region was the Neotethys that formed a sea way which
continued eastward through the Middle East to the Himalayas (Kummel,
1970). This sea; the Tethys played the most important role in the
Mesozoic and Cenozoic history of the Circum Mediterranean region as a
whole and of Egypt in particular.
On the western margin of the present day Africa, another seaway
began along the dissected edges of the African-South American plates;
along the future Central Atlantic Ocean. In both the Tethys and West
Africa, rifting concentrated along their margins. The westward
propagation of the Paleotethys from its Paleozoic domain in east
Gondwana to fill the highly rifted zones in the Mediterranean realm
followed the polyphase rifting which started in the Permian and
constantly propagated westward during the Triassic, reached its acme by
the separation between North Africa and Europe by Middle Jurassic
(Ziegler 1988, 1992). This rifting together with the Paleozoic paleo-relief
of northern Gondwana resulted in the development of major sedimentary
basins along the present day North African plate (subsurface basins in
the north Western Desert) and the Sinai sub-plate of the Arabian plate.
”.
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The multiple ·phases of rifting resulted in fact, in the oceanization of the
Neotethys, The important phases occurred in the Cretaceous during the
Neocomian-Early Aptian (Mascle et al. 1988, Binks and Fairhead 1992)
along the proto-Atlantic ocean and. from Tunisia to Egypt to the
Euphrates through the Palmyrides (Guiraud and Bellion 1985). A second
phase of rifting happened during the Aptian-Albian where the old basins
were ”pull-apart” in consequence to the rapid opening of the Equatorial
Atlantic Ocean (Guiraud and Maurin 1991, 1992). The rifting phases
were either preceeded by magmatic volcanism (active rifting) or latter
vulcanicity (passive rifting). However, these rifting phases resulted into
the many basins that littered the northern part of Egypt where thick
Jurassic and Cretaceous sediments were deposited. The earliest
Cretaceous sediments in the area studied were recorded from the core of .
Gebel Halal where the Malha Formation was deposited. The Lower
Cretaceous Malha Formation is known from the eastern and western
sides of Sinai, from the north of the Eastern Desert between Shabrawet in
the north and Wadi Qena in the south and also from the subsurface of the
northern Western Desert.
In Sinai, the Malha Formation is a clastic-carbonate sequence of the
platform type whereas subsea clastic fans were developed in the north
giving place -to shales in the deep marine. Thickness is 240 m in the
surface section in addition to 406 m in the subsurface. In the Gebel Halal
core, the Malha Formation is classified_ into 3 members, the lower is
dominated by ferruginous siltstones, the middle is made of thick crossbedded
ferruginous sandstones and the upper is composed of kaolinitic
and calcareous sandstones interbedded with claystone. The contacts
between the middle and upper members and between the upper member
and the overlying Halal Formation reflect unconformable relationships.
These hiatuses are most probably related to the time gaps between the
different phases of rifting spanning the time between the Neocomian.and
the Albian. The contact between the Malha Formation and the
Cenomanian Halal Formation is marked by a conglomerate bed, which
seems to be of more than local significance.- The conglomerate represents
the beginning of a transgressive phase when the Cenomanian flooded
Egypt and penetrated deeply southward covering most of the country and.
even continued into the Sudan (Klitzsch 1978t Issawi et a1. 1998, 1999).
The Cenomanian rich history, in Egypt and in many other parts in
Africa and South America, is related to the final separation between the
two continents which took place approximately at 100” 105 Ma; Albian
to Cenomanian (Mascle et al. 1986, Nuremberg and Muller 1991). On
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the other hand, the Neotethys began to close during the Cenomanian in
jolts or pulses (Phillip et al. 1993 a; b; Dercourt et aI. 1993) and
expressed in the many unconformities within the thick Cenomania.n
section in Egypt. The closure of the Neotethys triggered a multiple
phases of rifting along the Africa ..Arabia plate margin. The Cenomanian
time falls within the worldwide recorded Cretaceous Normal Magnetic
Quiet Zone (NMQZ) which started around 120 Ma: Early Aptian
(Ziegler 1990, 1992) and this fact is expressed in the widespread and
thick Cenomanian sections along the edges of Africa-Arabia plate. The
basins developed were deepened probably due to a sag phase during the
pre-Cenomanian and also during the Cenomanian times. The heavy load
of ca 2000 m Jurassic sediments and the Triassic thick sediments in the
subsurface in Sinai, 400 m (Issawi et a1. 1999) plus an anticipated
Paleozoic and Lower Cretaceous sections (£g 1500 m) resulted in a sag
phase, accommodating the basins, for more sediments to be poured in
them. According to McKenzie (1978), the basins subsided in response to
cooling and contraction of the lithosphere and the asthenosphere, which
were thermally disturbed during the earlier rifting phases. The isostatic
. response to such cooling is flexural subsidence of the crust. In such a
thermal setting, magmatic activity decreases rapidly and then ceases
altogether.
In the deepened basins along northern Egypt and due to a high sea
level (Haq et al. 1988), these basins were filled by thick carbonate
sediments, e.g. Gebel Halal area; at the same time clastics were
interbedded with carbonates toward the south. The southern facies in
Sinai is the most dominant Cenomanian facies in all Egypt, which was
named ”Gaiaia Formation” by Abdallah et a1. (1965).
The Cenomanian carbonates of the Halal Formation is a localized
facies, hence Issawi et al. (1998, 1999) named the Cenomanian beds in
Sinai ”Galala Formation” which is more widespread than the Halal
Fonnation.
The HaIal Fonnation builds up the main bulk of Gebels Haial and
Libni, whereas the upper members of the formation are exposed in the
faulted blocks of Talaat El Badan, EI Burqa and Urn Hosseira. In the
study area, the Halal Formation is divided into five members; marly
limestone (92 m) at top followed downward by chalky limestone (90 m),
marly dolostone (60-75 m), dolostone (73 m) and clastic-carbonate
section (281 m) at base. Both the upper and lower boundaries of the
formation show unconformable relationships with the Abu Qada and the
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Malha formations respectively. The lower boundary is characterized by
conglomerate, whereas the upper boundary is dedolomtized including
dessication cracks and paleosol red beds. The unconformities between the
members are taken as a proof for the uplift pulses, which the area suffered
during the Cenomanian echoing the many phases of the Tethys closure.
On the other hand, erratic distribution of the members of the Halal
Formation in different blocks is taken as a proof for block faulting where
meridional or submeridional faults dissected the area during the
Cenomanian. Blocks kept rising in the transgressive sea leading to the
absence of one or more members contiguous to other blocks where these
members are present.
The Africa-Arabia passive margin registered several episodes of
rifting, subsidence and magmatism before the Neotethys began to close
during the Early Turonian (Lanphere and Pamic 1993; Sengor et al. 1993)
though the initiation .of the closure started in pulses during the
Cenomanian. The closure of the Neotethys was associated with N-S
shortening and the collision between North Africa and Europe. The
Turonian history in Egypt is very complicated and diversified when
moving from south to north. Southern Egypt was in flames due to the
uprising of the acidic magma building the many impressive mountains of
EI Kahaf, Abu Khrug, Mishbeh and many others. The acidic rocks were
dated Turonian, though eruptions started in the Early Cretaceous and
continued during most of the Cretaceous. However, the eruptions peaked
in the Turonian and the Senonian especially during the Coniacian and
Campanian (Meneisy1990; Issawi et al. 1999). Proper Turonian
fossiliferous strata are not known south of Qena, but further north they
started humbly with minor thickness, 20 m at Wadi Qena and increase
gradually northward, 140 m at Ataqa Facies (Gebel Ataqa and
surroundings, Issawi et a1. 1999) and reach 225 m at Sinai Facies.
The earliest Turonian sequence in the study area is the Abu Qada
Formation represented by 39 m green shales, yellow marls and white
fossiliferous limestone. The base of the unit is a 2-6 m rich ammonite
marl bed, which is a marker horizon at the base of the Turonian section in
Sinai. At Talaat EI Badan, the topmost bed of the Abu Qada Formation is
2 m reddish claystone with gypsum nodules and beach gravels. The upper
contact of this bed is wavy and uneven. Outside the area studied, Issawi
et al. (1998) mapped a 15 m section between the Abu Qada Formation at
base and the Wata Formation at top at Ras EI Naqb-Sheikh Attia stretch.
These authors named the gypsum unit ”Buttum Formation. In the study
area, it is believed that the 2 m red bed
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at the top of the Abu Qada Formation is coeval with the Buttum
Formation. This red bed was spotted by the candidate.from Gebel Areif.
El Naga, Kherim to Gebel El Risha whereas sandy facies takes its place
at northeast Sinai; where at Qussaiyma the base of the Wata Formation is
cross-bedded, ripple-marked carbonate-clastic sequence. The base of the
Abu Qada Formation is rich in planktonics which decreases gradually
upward in the section pointing to shallower depositional conditions
reaching its acme at the middle Turonian where very shallow conditions
gave the Buttum Formation or its coeval red gypseous claystone with
beach gravels. At the west of Gebel Halal, the place of this shallow
sabkha flat is taken by the presence of greenish yellow saliferous sandy
argillaceous dolomicrite with ferruginous calcite veinlets.
Following this sabkha phase in the Turonian history of Sinai, a shallow
transgression flooded the ’study area .depositing ca_170 m brownish
yellow and white colored well-bedded limestone section equated here
with Ghorab’ s Wata Formation (1961). The Wata Formation is classified
in the study area into three members. The lower member is 49 m peloidal
bioclastic wackestone, bioclastic packstone and oolitic peloidal
packstone. The middle member is 43 m bioclastic wackestone and
bioclastic packstone whereas the top member is 79 m planktonic
bioclastic wackestone. The three members are not always represented in
all the sections measured in the study area. The Wata Formation is
represented by one or more members in places, that again points to block
movement mostly along meridional direction that cut through the basin
while deposition was taking place.
At the north of Gebel Ralal and around Gebel Dalfa, the lower
member of the Wata Formation is directly overlain by the Matulla
Formation. The gap in sedimentation between both units is much greater
than in other sections in the same Gebel. This gap is a major
unconformity represented in other sections in east Sinai by 5-10 m
(Issawi et a1. 1998), and in west Sinai by 40 m (Issawi et al. 1981) crossbedded
sandstone, showing every kind of color and textural variations.
The stratigraphic setting of this sandstone makes it possible to equate it
with the Taref Sandstone of the Nubia Fonnation in the central and
southern latitudes of Egypt. The age of the Taref sandstone is Coniacian,
a stage of DROP in sea level (Haq et at. 1988). The quartz sands of the
Taref Fonnation was brought by rivers from the high acidic mountains in
the south. However, Kerdany & Cherif (1990) reported 80 m crossbedded
sandstone on the top of the Wata Formation, which they
considered the lower part of the Matulla Formation192
..
In the study area and in the Gulf of Suez (Awad and Abda.J.la1966)
there are fossiliferous carbonate’,beds which belong to the Coniacian-
Santonian, 93.5 m thick at Gebel EI Shereif (northern Sinai), and 90 m
thick at Gebel Thelmet (Gulf of Suez). The occurrence of this Coniacian~
Santonian marine section is probably attributed to block faulting by
which some of the blocks sank in the Coniacian sea.
The Santonian is characterized by intense movements corresponding
approximately’to the end of the Cretaceous Normal Magnetic Quiet Zone -
dated at 83.5 + 0.5 Ma (Ziegler 1990, 1992).Most of the areas affected
by the Santonian intra-plate compressional- transpressional deformations
are localized in Pan-African crustal domains. Shortening increased along
the Tethyan margin from west to east. The closure was related to the
cotinter~clockwise rotational northward drift of Africa-Arabia during
Santonian times, synchronous with a global plate reorganization leading
to this drift and also to the collision with the Eurasian plate (Le Pichon et
al. 1988; Dewy et a1. 1989; Ziegler 1990).The Santonian was the time
when the inversion of the north Sinai basins took place.
The Matulla Formation is Late Turonian-Santonian in’ age and
represented in the present area by the upper 43.5 m sandy bioclastic
wackestone, sandy dolomicrite, bioclastic wackestone and claystone and
the lower 50 m dolomicrite, bioturbated and argillaceous micrite. Above
the Lower Member of the Wata Formation at the north of Gebel HaIal
and around Gebel Dalfa, the upper part of the Matulla Fonnation lies
which is represented by 43.5 m packstone, partly peloidal, marly or
argillaceous micrite and shales. The Matulla Formation is missing
around Gebel Lebni.
The many unconformities within the Matulla section and between the
MatuBa Formation and the overlying and underlying units are explained
by the rising or the inversion of the many basins in north Sinai during the
Santonian leading to the formation of the major Syrian Arc System in
north Egypt. The history of unconformities is, heightened by the
meridional faults, which were also active during the inversion leading to
different sections in adjacent blocks.
Above the Matulla Formation in central Sinai lies the Duwi
Formation, which is 65-85 m limestone and marl partly phosphatic with
dark chert bands. The Duwi Formation in central Sinai carries the same
fossil assemblages, which the fonnation includes in central Egypt (Issawi.