SEDIMENTOLOGIC AND TECTONIC EVOLUTION OF THE UPPER ...

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The Upper Cretaceous-Lower Ternary rocks around Wadl Qena. Egypt. represent a mixed sdlclclas- tlc-carbonate-phosphorlte succession including (from base ...
Sedimentary Geology, 46 (1986) 111-133

111

Elsewer Science Pubhshers B V, Amsterdam - Printed m The Netherlands

S E D I M E N T O L O G I C A N D T E C T O N I C E V O L U T I O N OF THE U P P E R C R E T A C E O U S - L O W E R TERTIARY S U C C E S S I O N AT WADI QENA, EGYPT

M O H A M E D A SOLIMAN. M O H A M E D E HABIB and EZZAT A A H M E D

Department of Geology. Faculty of Science. Umverslty of Asstut. AssJut (Egypt) (Received August 31. 1984. rewsed and accepted March 26. 1985)

ABSTRACT

Sohman, M A , Hablb, M E and Ahmed, E A , 1986 Sedlmentologtc and tectomc evolution of the Upper Cretaceous-Lower Tertiary succession at Wadl Qena, Egypt Sediment Geol, 46 111 133

The Upper Cretaceous-Lower Ternary rocks around Wadl Qena. Egypt. represent a mixed sdlclclastlc-carbonate-phosphorlte succession including (from base to top) the Nubia Sandstone. Quselr Shale. Duwl Formation. Dakhla Shale. Tarawan Chalk. Esna Shale and Thebes Formation Facies and m~crofacles lnvestlgauons were carned out The Nubm Sandstone was deposited by a fluvlatlle system. whereas the Quselr Shale was laid down by deltaic sedimentation The Dakhla Shale. Esna Shale and Tarawan Chalk were formed m open marine (pelagic) realms The Thebes Formation IS a shallow,ng carbonate facies Phosphontes were accumulated as lag deposits by reworklng and winnowing of pre-existing phosphatic materials The sedimentation of the Upper Cretaceous-Lower Tertiary rocks were affected by regional and local tectonics (1 e, faulting) The latter played a substantial role in the distribution of the different facies particularly the sfl~c~clast~c-carbonate facies

INTRODUCTION

The Upper Cretaceous Lower Terttary sedimentary rocks cropping out m the Wadl Qena area, Egypt (Fig 1), are represented by a mixed sthclclastlc-carbonatephosphonte succession up to about 335 m thick. The lithostratlgraphtc classification and ages of this succession (Fig 2) were dealt with by many authors (Youssef, 1957; Said, 1961, 1962, Abdel Razlk, 1972; Fans, 1974, Abdel Gawad, 1980) Previous studies carried out on these rocks were mainly of straugraphlc interest (e.g Zlttel, 1883; Barron and Hume, 1902; Said, 1961, 1962) Brief hints about their sedimentology were casually given by Abdallah et al (1972a, b) and Philobbos (1976). In this paper the facies characteristics and deposltlonal environments of 0037-0738/86/$03 50

© 1986 Elsevter Science Pubhshers B V

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Q u a t e r n o r j and Phocene

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~,ediments Thebes Formo%on

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these rock~ are presented An attempt has also been made to present a concept about the regional and local tectonics which controlled their deposition F A ( IFS A N D D E P O S I T 1 O N A L E N \ I R O N M E N T S

Nubia Sandstone

In the study area the Nubia Sandstone (Russegger, 1837, Youssef. 1957: Said, 1962) crops out along the Qena-Safaga road from Km 45 eastward (Fig. 1) and includes three distinctive llthologlc umts (Fig_ 3) from base to top (1) A sandstone unit. about 10 m thick, of yellowish-brown and medmm-gramed quartz arenite characterized by the occurrence of large-scale planar cross-beddings, erosional surfaces, and trough cross-bedding (Ftg_ 4a and b) The large-scale planar cro,ss-beddlng could be formed b3, lateral accretion The top of this unit (Fig 4a)

113 Lithostrohgrophy After Youssef (1957)ond SOld ( 1 9 6 2 )

Adopted ~n the present studies ( o t t e r Abdel G o w o d , 1 9 8 0 )

Thebes F o r m a t i o n

Thebes Formation

Ekno

Esna

Ypresian

Londenlon

shale

Shale

irowan Chalk

Taravon

Chalk

Dakhla

Dakhla Shale

Damon

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Shale

Noestricht ion _

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Nubia

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Shale Nubia

Pre_Componlan

ormatlon

Sandstone

Sandstone

F~g 2 Stratigraphy of the Upper Cretaceous-Lower Tertiary succession at Wad~ Qena. Egypt

displays lenticular and planar bedding suggesting deposition m the upper flow regime. Geometrically, this sandstone displays lentlcular shape. It grades laterally into a: (2) Siltstone-mudstone unit (about 45 m thick) consisting of greemsh-grey,

114

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Small-scale cross-bedding

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Fig 3 Measured columnar sechon,, In the Nubia Sandstone showing the different lacJes ,~l Km 60 and 65 along Qena Safaga road

papery shale alternating with highly ferruglnated fine sandstone and slltstone beds (up to 30 cm thick)_ This s l l t s t o n e - m u d s t o n e unit includes plant remains a n d occasional calc~tlc spherulltes (Fig. 4c) of p r o b a b l y pedogenic o n g m

115

l-~g 4 (a) Large-scale planar cross-bedding at the base, and lentlcular bedding at the top separated by erosional surface and channel-fllhng trough cross-bedding at the middle (arrow) probably channel bar Nubia Sandstone, Km 65, Qena-Safaga road (b) Close-up view showing the trough cross-bedding in the middle of the channel bar, Km 65 along Qena-Safaga road (c) Calcite spheruhtes of a paleosod honzon in the Nubia Sandstone (d) Rods of plant remains at the top of the Nubia Sandstone

(3) The upper sandstone unit, about 10 m thick, is formed of yellowish-brown and pink, free-grained quartz aremte characterized by planar cross-bedding, ripple marks and traces of roots (Fig 4d) Generally these units are devoid of marine fossils. The facies characteristics of the Nubia Sandstone display features in common with those proposed for the fluvial models (e g. Selley, 1978; Walker, 1979) The basal sandstone unit of the Nubia Sandstone (Fig. 3, section 1) might represent a channel point bar. The base of this point bar is unexposed Accordingly, it Is hard to see lag deposits The interbedded ferruglnated fine sandstone, slltstone and laminated shales including plant remains and pedogenetlc calcite concretions, and showing fining-upward cycles (F~g. 3, section 2) are Interpreted as floodplain deposits The upper fine sandstone unit characterized by planar cross-bedding and traces of roots

116 on its top (Fig. 3, section 3) could be d e p o s i t e d by crevasse rivers (c.f. Khtzsch et a l , 1979, W a r d et al., 1979).

Qusetr Shale The Quseir Shalo (Fig. 5) overhes c o n f o r m a b l y the N u b i a S a n d s t o n e and underhes the Duwl F o r m a t t o n (Fig 2)_ Its m a x i m u m thickness attains a b o u t 50 m_ The first a p p e a r a n c e of this unit is occasionally m a r k e d by the presence of an oyster bed, up to 125 cm duck, or p h o s p h a u c b e d s ( a b o u t 70 c m thick), b o t h of which represent the first e n c r o a c h m e n t of the sea in the C a m p a n i a n time. T h e Quse]r Shale ts represented b y an u p w a r d - c o a r s e n i n g sequence (Figs. 5 a n d 6a, b). D e p o s i t i o n m a

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LEGEND ~!N',~ Sandstone Peering n a t r o j a r o s l t e T h i n . bedded ( S - 3 0 c m ) a l t e r n a t e d fine and ferrugmous sandstone and laminated grey shale

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117 deltmc system ~s suggested At the base of the sequence, open marine finely laminated and dark grey shales with abundant planktomc foraminifera are encountered which could be deposited within the zone of the pro-delta clay. Phosphatic bed intercalauons at the base of the Quselr Shale are composed of intact collophane grains, skeletal bones and coprohtes admixed with benthonic and planktonic forammifera and free-grained detrital quartz grams, all set in a calcareous cement or argillaceous matrix (Fig. 6c). Idlomorphlc pyrite crystals are found distributed m the groundmass and within the collophane and bone grams indicating a phase of anoxlc conditions. The occurrence of strong bloturbation at the base of the phosphatic beds indicates a phase of oxic conditions in which orgamc activity was maximum. This m~ght have preceded the above-mentioned anoxic one The occurrence of intact collophane grams and skeletal bones (Fig. 6e and f) reveals a very weak effect of reworkmg The top of the Quseir Shale is composed of rhythrmcally alternating free sandstone and slltstone beds (5 cm to 1 m thick) with occasional ripple marks (Fig. 7a), channelhng (Fig. 6b) and marine fossihferous (shelly) marly bed mtercalanons Natrojarosite-bearing sandstone is encountered at the top of Gabal Abu Had (F~g. 5). This umt is interpreted as a delta front The natrojaroslte-bearing and rippledrifted sandstones probably represent distributary channel mouth bars, whereas the fosslliferous beds rmght be deposited in interdistrlbutary bays.

Duwt Formation The Duwi Formation crops out at Gabla Abu Had and Wadi Hamama districts overlying conformably the upper sandy unit (delta front) of the Quseir Shale (Figs. 7b and 8). Detailed description of the lithology and deposltional environment of this formation will be treated in a separate article. The Duwi Formation was deposited during a transgressive phase probably interrupted by a local regressive one. The first transgressive phase is indicated by the formation of oyster banks showing a marked imbrication, fossiliferous massive sandstones and laminated sdtstones at the base of the Duwl Formation. These beds comprise a restricted marine fauna (Buhmma eleganttsstma; D.O. Ouda, pers. commun., 1982) and are characterized by lag deposits and bioturbauon at the bottom. These sedimentologlc features point to a restricted environment in which the hvlng fauna shows little diversity In addmon, the presence of bottom bioturbation and lag deposits, and lammanon indicate deposition in coastal bays. Overlying this unit (Figs. 8 and 9), thick beds of phosphontes occur composed of collophane grains and bones admixed with minor amounts of quartz grams. The phosphatic components m the Duwl Formation differ markedly from those associated with the Quseir Shale (Fig. 6c), here they are more fragmented and contain phosphatic lithoclasts (Fig. 10a). Also, the collophane grams contain hmomte inclusions instead of pyrite. The presence of strong bloturbatxon as well as erosional surfaces (Figs. 6d and 10b) at the base of the phosphorite beds suggest a period of slow sedimentation, followed by a phase of anoxic condmon m

II~

119

Fig '7 (a) Ripple drifted cross-bedding in the free-grained sandstone bed intercalations at the top of the Quselr Shale at Wad1 H a m a m a (b) Close-up view showing the sharp contact (arrow) between the Duwi Formation (whate) at the top and the underlying rhythmic bedding (delta front) of the Quselr Shale

Fig 6 (a) Coarsening-upward sequence of the Quselr Shale Note the presence of the phosphorlte bed ( p ) and dark grey shale (sh) at the base, and s a n d - s d t s t o n e umt (s) at the top, Gabal Abu Had (b) Close-up view of the top part of the Quselr Shale (at Gabal Abu Had) showing the channel fillings (arrow) and the characteristic rhythmic bedding (c) Negative print of phosphorlte composed of poorly sorted collophane grains (cn) set m a mlcrmc matrix The white n m of the largest collophane grams proved to be pyrite coating Quselr Shale, × 40 (d) Close-up view showing bloturbatlon at the base of the phosphorlte beds (e) Collophane nodules (cn) set in a fine-laminated shaly matrix at the Quselr Shale Note the marked stretching and deformation of the collophane grams, × 33 (f) Intact bones embedded in a mlcntlc matrix rich in planktomc forarns, Quselr Shale, × 24

120 Secrpon 4

Secflon S

8ecflon 6

See hon 8

Chalk wLth fhnI noduLes {I'll Phosphorlte

m'l

Horl Oyster bed Shole i ' ~ Phvsphol:c sondsione Onsconfor rnl [y surroce I ~ ] elolurbcl~on []

,,l

(

4t(m

2km

13 5 km

Quse[r Shole

F=g 8 Measured c o l u m n a r secnons m the Duwn F o r m a t i o n

which collophane grains enclosing authlgenlc pyrite inclusions were formed_ These condlttons are probably stmilar to those prevailing during the deposmon of the phosphortte intercalations at the base of the Quselr Shale The absence of pyrite, and the fragmented nature of the phosphorite components in the Duwi Formation point to a peraod of reworklng in oxic conditions Garrison et al. (1979) and Glenn and Mansour (1979) believed that the phosphontes of the Duwl Formation were formed by concentration as lag deposits through winnowing of the finer material during a phase of sea regression. This concept seems to be applicable in the present case, since evidences of long transportation have not been recorded for the phosphorltes of the Wadl Qena distract.

Dakhla and Esna Shales

The Dakhla and Esna Shales are exposed along the cuesta scarp faces at Gabal Abu Had and Wadi Hamama The two shale units are separated by the Tarawan Chalk, 6 m thick (Fig. 2)_ Thicknesses of the Dakhla and Esna Shales attain 42 and 50 m, respectwely, minor local variations in the thickness occur at Wadt Hamama The two formations consist of monotonous grey laminated shales and marls, which become more calcareous upward toward the top of each unit The topmost part of the Esna Shale in particular is marked by the presence of htghl3, ferrugmated silty intercalations Planktonic foraminifera are abundant in both the Dakhla and Esna Shales The upper part of the Dakhla Formation is characterized by an abrupt change in mlcrofaunal composltnon from a GIobotrun~ana-Heterohehx to Globorotaha-Globtgerma assemblage (Abdel Razlk, 1972, Fans, 1974). Such a dia-

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Fig l0 (a) Photomicrograph showing phosphonte of the Du~l Formation compo,,ed nlaml; ol Iragmerited bone,, (hn) and minor amount> of collophane (on), sel m a calcareous groundmd~ (dai k) X 5(1 (hi (lose-up ,,row at the base of the Duw~ Formation Note (1) the remnant ot submarine erosional ~urface (dashed lines) and (2) the Irregular boundary bevaeen the ~fllcffmd and unsdlt.lhed parts of a phosphorlte bed (arrov,)

s t e m o c c u r s at t h e b o u n d a r y b e t w e e n t h e C r e t a c e o u s a n d T e r t i a r y abundant

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foraminifera and

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123 TARAWAN CHALK AND THEBES FORMATION Tarawan Chalk (Awad and Ghobrlal, 1965) and Thebes Formation (Said, 1962) represent the carbonate facies associated with the Upper Cretaceous-Lower Tertiary sedimentary succession at Wadl Qena (Fig 2) The Tarawan Chalk overhes conformably the Dakhla Shale and underlies the Esna Shale It has a consistent' thickness of 6 m allover the study area. It was deposited during the Landenlan (Abdel Razik, 1972, Fans, 1974). The Tarawan Chalk is composed of planktonic foraminifera and nannofosslls (coccohths) which point to deposition in an open marine realm The Thebes Formation (Fig. 2) overlies conformably the Esna Shale representing a shallowing-upward sequence Three different facies can be recognized from bottom to top (Fig. 11): (1) A marly facies composed of light grey massive marl, the lower part of which is represented at Gabal E1 Gir by rhythmically alternating beds of calcareous shales and marls grading upward Into massive chalk and marly beds Sparse chert nodules are encountered within this facies (2) A rhythmic chalky facies usually intercalating the middle part of the Thebes Formation at Gabal El Gir (Fig. 11) It consists of alternating thin beds, about 30 cm thick, of hard and frmble chalky hmestone (Fig 12a). The former contains sparse bloclasts comprising fragments of pelecypods, echinoderms and gastropods, planktonic foraminifera are rare. Llthtfxcatlon of the chalky beds might have occurred contemporaneously with the deposition, particularly during periods of low rate of sedimentation (cf. Furslch and Wendt, 1976) The friable chalky beds are laminated including chert nodules and foramlnlferal ooze (Fig 12b). The marly and rhythmic chalky faoes represent an open marine (pelagic) facies (3) A nodular and shelly limestone facies constituting the upper part of the Thebes Formation It is recorded at Gabal E1 Gir and Gabal Aras, at Gabal Abu Had this facies is missing It consists of nodular limestone, up to 11 m thick, alternating with shelly limestone beds The nodular limestone displays a pseudoconglomeratlc appearance, where the friable and laminated chalky matrix bends around the coarser components. The shelly limestone is composed of fragments belonging to lamelhbranchs and gastropods, bryozoan fragments and benthonic and planktonic foraminifera are rare (Fig 12c). Chert is less abundant compared with the lower faoes A limestone bed containing N u m m u h t e s is encountered near the top of Gabal Aras (Fig. 12d) Weber (1965), Hopkins (1977) and Seyfrled (1980) attributed the formation of nodular chalk to differential submarine cementation, submarine erosion and subsequent resedimentation by gravity flow processes_ Reading (1980, p 376) stated that the prime mover behind these phenomena must have been reduced rates of sedimentation which characterlse local non-subsldent areas or more widespread regions during shallowing, an both cases accelerated bottom currents probably played significant roles (Kennedy and Garrison, 1975). The nodular and

124



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Fig 11 Correlauon chart showing the distribution of the different carbonate facie,

125

Fig 12 (a) Rhythmic bedding in the Thebes Formation, Gabal El Glr_ (b) Planktomc ooze at the base of the Thebes Formation, × 23, (c) B~oclastlcwackestone enclosing gastropod and mollusc shells. × 20, (d) Nummuht~c bloclastlc wackestone at the top of the Thebes Formation Gabal Aras, × 25

N u m m u h t l c h m e s t o n e facies indicates a shallowing of the sea at the top of the Thebes Formation SEDIMENTARY EVOLUTION T h e s e d l m e n t o l o g l c evolution of the U p p e r C r e t a c e o u s - L o w e r T e r t i a r y sedimentary succession c r o p p i n g out m W a d i Q e n a area can be s u m m a r i z e d as follows (Fig_ 13): (1) In p r e - C a m p a m a n time a thick fluvial sequence of the N u b i a S a n d s t o n e was deposited. A c c o r d i n g to K h t z s c h et al (1979) a h u m i d climate p r e v a i l e d d u r i n g this time. E1 Shazly a n d Krs (1972, 1973) c o n c l u d e d that the N u b i a S a n d s t o n e was d e p o s i t e d u n d e r t r o p i c a l to s u b t r o p i c a l conditions, as the p a l e o e q u a t o r at that time p a s s e d t h r o u g h central Egypt. (2) T h e e n c r o a c h m e n t of the T e t h y a n Sea in this area b e g a n after the d e p o s l t t o n of the N u b i a Sandstone, as i n d i c a t e d by the oyster b a n k s overlying Jr. The base of the Quselr Shale m a r k s the transgression of the sea which caused the d e p o s i t i o n of l a m i n a t e d m a n n e shales c o n t a i n i n g a p p r e c i a b l e a m o u n t s of bones, c o l l o p h a n e n o d u l e s a n d p l a n k t o n i c f o r a m i n i f e r a T h e beds, o c c a s i o n a l l y rest on a n d are interc a l a t e d b y p h o s p h a t i c b e d s rich m pyrite crystals i n d i c a t i n g a p e r i o d of anoxic condition. This unit is overlain b y a c o a r s e n i n g - u p w a r d sequence consisting of p r o - d e l t a and delta front d e p o s i t s t e r m i n a t i n g the d e p o s i t i o n of the Quselr Shale

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:~g 13 Fac:es, depo~,thonal e n ; l r o n m e n t s and sea-level change,, of the U p p e r ( retaceou,, [ order Tert:ary succession at WadJ Qena Eg,cpt

Nubia Sandstone

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Age

¢.

127 (3) The base of the Duwl Formation (Campanian-Maestrlchtlan) is characterized by the deposition of oyster banks, bioturbated massive sandstones and clays (with a restricted benthonic fauna), probably in bays. Continuous deepening of the sea led to the accumulation of thick phosphorite beds over the above-mentioned facies. Such phosphorite deposition seems to have been developed as a result of complex processes including deposition of phosphatic beds under anoxlc conditions, similar to those phosphatic beds at the base of the Quseir Shale, followed by a phase of winnowing, reworking and concentration of the phosphatic materials probably as lag deposits, under OXlC conditions (see Garrison et al, 1979; Glenn and Mansour, 1979). The last phase may be attributed to the effect of sea-level drop during the late Campanlan-Maestnchtian. (4) An abrupt rise of sea level or subsidence in the basin of deposition took place at the beginning of the Maestrlchtlan leading to the deposition of an open marine chalk forming the top of the Duwi Formation This chalk is rich in planktonic foraminifera and assooated with chert nodules. The basin was gradually filled with a thick succession of open m a n n e shales and marls (Dakhla and Esna Shales), rich in planktonic foraminifera, and interrupted in the middle by 6 m thick open marine chalk (Tarawan Chalk), conformably over the Duwi Formation. These were followed by a thick sequence of open marine marl and chalk of the Thebes Formation. The lower part of the Dakhla Shale belongs to the Maestrichtian, whereas the upper part belongs to the Danian (see Said, 1962, Said and Sabry, 1964) The advent of the Tertiary is characterized by the extinction of the Globotruncana- Heterohehx associations. As mentioned by Hallam (1981, p. 159) and others, the Cretaceous was, except at the end, a period when tropical-subtropical climates extended to at least 45°N and warm to cool temperature climates extended to the poles. He added that there is a consensus that the Maestrichtian was a time of cooling with chmat~c deterioration continuing across the Cretaceous-Tertiary boundary to reach culmination in the late Danian (Krassllov, 1975). In the opinion of the present writers the mass extraction of the Globotruncana-Heterohehx assemblage and other animals at the end of the Cretaceous may be due to such deterioration of climate TECTONICS AND SEDIMENTATION The Upper Cretaceous-Lower Tertiary succession in the Wadi Qena area represents a predominantly transgressive sequence (Fig. 13). The first transgression of the sea has been recognized in the Campanian time on top of the Nubia Sandstone. A m a x i m u m transgressive peak has been recorded in the Early Maestrlchtian during which open marine chalk at the top of the Duwl Formation was deposited. Two phases of sea shallowing could perceivably be recognized both in the Late Maestrichtian and the Ypresian. The first phase is reflected in disconformlties and diastems at the Cretaceous/Tertiary boundary (El Naggar, 1970, Issawi, 1972), whereas the

12g second phase is reflected in the deposition of the shallowing-upward carbonate sequence of the Thebes Formation Another phase of sea shallowing might have occurred in the Late Campaman at the Wadl Qena district and appears to have been responsible for reworklng, winnowing and concentration of the phosphorltes of the Ouwl Formation_ The Campaman transgressive and Ypreslan regressive phases (Fig 13) agree with the worldwide Campaman sea transgression and Late Ypreslan sea regression (Vail et al, 1977), and might thus be related to global eustatlc change of sea level_ The Cretaceous/Tertiary regressive phase of Vail et al (1977) and Hancock and Kaufmann (1979) is reflected in the Wadi Qena area m the extinction of the Glohotruncana Heteroheh:, assemblage at the top of the Maestrlchtlan Local tectomcs seem to have played a substantial role in the development and dtsmbutlon of the different facies of the Upper Cretaceous Lower Tertlar) succession of Wadl Qena_ In order to stud) such tectonic effects, it is necessary to deal with the sedimentary succession of Wadl Qena within the framework of a regional sedlmentologlc-tectomc model. After Hallam's (1981) X and Y postulated zones, the following sedlmentologlc-tectonlc model during the Late Cretaceous Early Tertmry p, made Regional data (Fig 14) are collected from E1 Naggar (1970), Issawl (1972) and Abdallah (1983). In pre-Campaman time fluvml Nubia Sandstone started to deposit in the northern and southern parts of Wadl Qena area (Fig 15a) In the Campanian time the Tethys transgressed over the Nubia Sandstone where oyster banks or phosphonte beds came to rest over it m the southern part of Wadl Qena area. lssawl (1972) believed that such a transgression started early in the Cenomaman where much of the country as far south as 25°30'N was covered by the sea The Campanlan time was associated, m the southern part of Wadl Qena, with a deepening of the basin of sedimentation probably accompanied bY synsedlmentary fracturing across the northern part of Wadl Qena (F~g. 15b) As a result, the area starting from the southern part of Wadl Qena till south of Gabal Owema was subsided developing a structural low, ke the '~ zone of Hallam (1981) The structural high north of it represents the X zone At the southern part of Wadl Qena the structural low basin was favourable for the deposition of open marine shales with abundant planktomc foraminifera mterbedded with phosphatic beds rich in authlgenlc pyrite This umt lorms the base of the prodelta shale or the base of the Qu,,mr Shale The subsidence was acuve tdl the end of deposltum of the Quselr Shale At the top of the Qusmr Shale a thick sequence of delta front ',and v~as deposited (Fig. 13). The structural basin (Y zone) behaved as a trap for the slliclclastlcs (sand, silt, clay) which were prevented from reaching the structural high (X zone), on which marine carbonates were deposited (Fig 15b) Thereafter. the transgression of the sea continued during which the basal part of the Duw~ Formation (facies of bays) was deposited on the Quselr Shale This was probably followed by a phase of anoxic condmons similar to those characterizing the lower part of the Qusmr Shale where phosphatic deposits were formed in SltU (such a phase

U, lr I I r l r "

S

=

34

Nubia Sandstone

~

,~

2

Wad; Qena

Co~

/

~

1"---~-------"4

- -

3 Gobol Owe0na

"

4

--

I

"t-.

,

"

Kur

Th

Ou.

4 Kurkur_DungUl

['

5

~

~

~:4

Basement rocks

Sholy Facies(marginal)

S Bir Abu EI HuseJn

6 Baragot El Shah

El. G. = El Oalala Formation

S.Ch. = Suldr Chalk

DK.Sh.= Dakhla Shale

Eoc. = Eocene

I-'-'-'-

= Thebes Formation

= Duwi Formation

Noes. -- MoeMrJchtian

I--1~ s,--

-_ I---I

U.E.= Um Umyied Formation

ES.Sh. = Esno Shale

Q. Sh. = Quseir Shale

o.

I-----'1 1

P----I u

:

Fig 14 Correlation chart between different stratlgraphlc secttons m Central and Southern Egypt (ls,,awy, 1972, Abdallah, 1983, and the present stud3,)

IA

u.

, , , ,

I.,.I/ .o~;' -" , ' , ~, 'e"

Camp. = Capon;an

Haw. = I-k]waShlya Formation

T.C:h.= Taravon Chalk

N,

Con. = Conioc,on

LEGEND

30 °

2

i//

• 3

[TrT-i Carbonole Facies (shallow marine) Sholy Facies (pelagic)

],',:~Carbonate Facies(pelage)

130 I

I

Wodi Oeno N

I

W Oeno

I

Owtlflo

S

I

I

KurKur

Bar

OunOul

El hueoein

Ooro01 El shN

X

~Y--

5 L

,--,

Ypreo ion

S'L 't

Y

.

Londenlon Ypres~on

S L

Londenlon 4- X-e, •

-Y

8 L

/"

"

I S L-x-

-

I -

Maestnchtlon - Damon

Y

...---'J

,,

Companion

~ ~

.

,

.

,

.

_ Moestricllt~on

J

~ Pre_ Compoman

~]

Nubia Duwi

E~

....

Fig

15

Sandstone Format=on

Ouse=r

Shale

Dk = Oakhla

~

Shale

Tarawan Chalk

Es = E s n a

Thebes

~

Inferred

Formahon

Shale

Drosfem

Foul!

SchemaUc diagram

showing the

Cretaceous Lower Tertiary succession

tectonic

and

sedimentary evolution of

the

UppeJ

131 is now missing due to later reworklng). The phosphatic materials were then subjected to reworkmg, winnowing and concentration as lag deposits. This could be attributed to shallowing of the sea due probably to a local tectonic uplift. A major transgresswe phase took place at the b e g m m n g of Maestrichtian and has resulted in the deepening of the sea basin at Wadi Qena area, so that the Wadi Q e n a - K u r k u r area behaved as Y zone On the structural highs (X zone) the open-marine chalky facies forming the top part of the Duwi F o r m a t m n was deposited at Wadl Qena During the Maestnchtlan and Danian, the Wadi Q e n a - K u r k u r area was characterized by the deposmon of the Dakhla Shale in the Y zone (Fig. 15c). In the northern part of the Wadl Qena area, ttuck open marine chalky limestone was still forming on he structural high (X zone) till the end of the Maestnchtmn At the beginning of the Landenian the O w e m a - K u r k u r district was subjected to more subsidence. An X zone developed from the southern part of Wadl Qena to Owema on which the open marine Tarawan Chalk was deposited. This formation Is missing m the northern part of the Wad~ Qena area. The K u r k u r - D u n g u l area was structurally high about that time. It was uphfted and subjected to erosive acuon (Issawl, 1972). On the structural high, thereafter, the shallow marine carbonate facies of the Kurkur Formation came to rest over the eroded parts of the Dakhla Shale (Fig. 15d). Such an uplift appears to be of a relatively local character since fine siliciclastic detritus was able, tdl the beginning of the Landenian (Said, 1962; Said and Sabry, 1964), to reach the basin of deposluon to complete the upper parts of the Dakhla Shale, between north of Kurkur and the Oweina area In the L a n d e m a n - Y p r e s m n , the general topography of the depositional basin was largely subdued and a major subsidence occurred, where much of the country till Blr Abu E1 Huseln behaved as a Y zone in which the Esna Shale facies was deposited (Fig. 15e). In the Late Ypresian the sea flooded the country up to the Bargat El Shab area (Fig. 15f) The whole area was changed to an X zone on which the Thebes Formation was deposited. This could be related to the development of a structural low (i.e, Y zone) south of the Bargat E1 Shab area According to the present model one can expect to find free siliciclastlcs in such a structural low SUMMARY AND CONCLUSION (1) The Upper Cretaceous-Lower Tertiary rocks of Wadl Qena area, Egypt, represent a mixed sfllclclastic-carbonate-phosphorlte succession. (2) This succession was deposited by a predominantly transgressive sea. (3) Facies descnpUon and modelling, and microfacles analysis revealed that: (a) The Nubia Sandstone was deposited in a fluvlatile environment, (b) the Quselr Shale represents a deltaic facies; (c) The phosphontes in the Duwi FormaUon were deposited by reworkang of phosphatic materials m the near shore zone as lag deposits, the pre-existing phosphonte sediments were deposited in anoxic conditions; (d) the Dakhla and Esna Shales represent open marine facies deposited in

132 s t r u c t u r a l lows d u r i n g m a j o r t r a n s g r e s s t v e p h a s e s . (e) the T a r a w a n C h a l k ts a n o p e n m a r i n e facies d e p o s i t e d o n s t r u c t u r a l h i g h s w i t h i n the o p e n m a r m e r e a l m , a n d (f) t h e T h e b e s F o r m a t i o n r e p r e s e n t s a s h a l l o w i n g c a r b o n a t e facies ( p r o b a b l y d u e to m a j o r uplift of the entire m a n n e basra) c o m m e n c e d with the d e p o s m o n of d e e p e r m a r i n e marl and chalk and e n d e d by shallow m a r i n e n o d u l a r h m e s l o n e a n d N u m m u l l t t c facms L o c a l t e c t o n i c s (l_e controlhng

the

f a u l t m g ) are t h o u g h t to h a v e p l a y e d a s u b s t a n t t a l role in

facms a n d

facies d l s t r t b u t l o n o f

the

Upper

Cretaceous

Lower

Terttarv rocks of Wadl Q e n a area

REFERENCES

Abdallah, G M, 1983 Stratlgraphmcal and sedtmentologlcal studies on El Sheikh Fadl Ras (;hanb road, Eastern Desert. Egypt M Sc thesis, Urn`, of Assmt, Assmt ~bdallah A M, Mahfouz. S and Abdel Razlk, T M 1972a Mineralogical and get.heroical studms on some Egyptian phosphates (Southern Egypt) Chern Erde, 31 305 320 Abdallah & M, Mahfouz, S and Abdel Razlk T M, 1972b Genesis of some Egyptian phosphate deposits [southern Egypt) wUh speual ernphas~s on X-ray analysis Chem Erde, 31 364 372 Abdel Gawad, M, 1980 Geology of the area southeast of Qena v~uh special reference to the phosphate deposits M Sc thes~s, Asstut Urn`, ~ssmt Nbdel Raz~k, T M, 1972 Comparative studms on the Upper Cretaceous-Early Paleogene sedmlents on the Red Sea coast. Nile Valley and Western Desert. Egypt 6th Arab Petroleum Congress, Algmre Pap No 71, pp 1-23 Awad G H and Ghobrlal, M G, 1965 Zonal stratigraphy oi the Kharga Oasis Egypt Geol Surs , 34 p 77 Bamm ~I and Hume, W F. 1902 Topography and Geology of the Eastern Desert ol Egypt (Central Portum) Sur`,ey Dept Cairo k[ Naggar. R, 1970 On a proposed hthostratlgraphlc subdivision for the Late (retaceous-Earl`, Paleogene succession m the Nile Valley,, Egypt U A R, 7th Arab Petroleum Congress, Pap No 64 El Shazly, E M and Krs M, 1972 A paleomagnetJc stud,~ of Cretaceous rocks from WadJ Natash area, Eastern Desert, Egypt Tra~ Inq Geophys Acad Tcbecoslo,, Sen no 329. Geofvs Sb 18 (1970) 323 334 El Shazly F. M and Krs, M 1973 Paleogeograph~ and paleomagnensm ol the Nublan Sandstone Eastern Desert of Egypt Geol Rundsch 62/l) 212--225 Fans, M, 1974 GeologLcal and paleontological studms on the Late Cretaceous-Earl.,' Fertlar> succession m the Qena region and Kharga ()asls M Sc thesis, Assmt Lira`, Assmt Furslch F F and Wendt, J, 1976 Hartgrunde und Kondensattona-Largerstaten Z Gcol Palaontol, 1-ml 11,5/6 238--245 Garrison R E , Glenn. C R . Snavely P D and Mansour S E A , 1979 Sedimentology and origin of Llpper Cretaceous phosphorlte deposHs at '~bu Tartur, Western Desert. Egypt Ann Geol Surv Egypt. 9 261 281 Glenn, ( R and Mansour, S k A 1979 Reconstructmn of the deposmonal and dlageneuc history of phosphontes and associated rocks of the Duwl Formation (Late (retaceous) Eastern Desert Egypt &nn Geol Surv Egypt, 9 3g8-407 Hallam A 1981 Facies lnterpretataon and the StratJgraphlc Record Freeman, San I~rancmsco, {: ahf Hancock, J M and Kaufman. E G, 1979 The great transgressmns of the late Cretaceous I (;eol Soc London 136 175-186

133 Hopkins, J C , 1977 Production of foreslope breccia by differential submarine cementation and downslope displacement of carbonate sands, Mmtte and Ancient Wall buildups, Devoman, Canada, Soc Econ Paleontol Mineral, Spec Publ_, 25 155-170 Issawy, B_, 1972_ Review of Upper Cretaceous-Lower Tertiary Stratigraphy m Central and Southern Egypt 56 1448-1463 Kennedy, W J , and Garrison, R E 1975 Morphology and genesis of nodular chalks and hard grounds in the Upper Cretaceous of southern England Sedlmentology, 22 311-386 Khtzsch, E , Harms, J C , Lejal-Nicol, A and List, F_K, 1979 Major subdivisions and deposltlonal environments of Nubia Strata, southwest Egypt Bull. A m Assoc_ Pet Geol, 63 967-974 Krassllov, V A , 1975 Chmatlc changes in eastern Asia as indicated by fossil floras II Late Cretaceous and Danlan Palaeogeogr, Palaeochmatol, Palaeoecol, 17 157-172 Phllobbos, E R , 1976_ Distribution of some trace elements in the phosphatic sediments of Egypt, and their possible utility as depth indicators Bull Fac Scl, Asslut U m v , 5 383-399 Russegger, J R , 1837 Kreide und Sandsteln Elnfluss yon G r a m t auf Letztern Neues Jahrb Mineral, pp 665-669 Reading, H G , 1980 Sedimentary Environments and Facies Blackwell, Oxford Said, R , 1961 Tectonic framework of Egypt and its influence on distribution of foraminifera Bull Am Assoc Pet Geol, 4 5 : 1 9 8 - 2 1 8 S a i d , R , 1962 The Geology of Egypt Elsevier, A m s t e r d a m Said, R and Sabry, H , 1964 Planktonic foraminifera from the type locality of the Esna Shale In Egypt Micropaleontology, 10:376-395 Selley, R C , 1978 Ancient Sedimentary Environments C h a p m a n and Hall, London_ Seyfried, H , 1980 Uber die Bildungsberelche Medlterraner Jurasedlmente am Belspiel der Betischen Kordlllere (Sudost-Spamen) Geol Rundsch 69 149-178 Vail, P R , Mltchum J r , R M and T h o m p s o n II1, S, 1977 Seismic stratigraphy and global changes of sea level, part four global cycles of relative changes of sea level, M e m A m Assoc Pet Geol. 26 83-98 Walker, R G , 1979 Facies Models Geoscl C a n , Reprint Ser 1 Ward, W C , McDonald, K C_ and Mansour, S E A , 1979 The Nubia Formation of the Quseir-Safaga area, Egypt A n n Geol Surv Egypt, 9 420-431 Weber, P , 1965 Blldung und Regelung yon Kalkknollengefugen Untersuchungen in Oberdevon des Rhelnlschen Schmfergebirges Dechenlana, 118 (1) 55-84 Youssef, M I, 1957 Upper Cretaceous rocks in Kosselr area Bull lnst D6sert Egypt, 7 35-54 Zittel, K A , 1883 Beltrage zur Geologle und Palaontologle der hbyschen Wuste und der angrenzenden Gebiete yon Agypten Paleontograpluca, 30 (1) 1-112