Campanian – Early Eocene Stratigraphy of the Southern Galala Plateau , Eastern Desert , Egypt

The Upper Cretaceous–Lower Tertiary rocks are widely distributed all over the Eastern Desert, extending from Gebel Shabrawet in the north, through the Gebel Ataqa and Galala massifs, to Wadi Qena in the south. In the north Eastern Desert (Gebel Shabraweet), these rocks are greatly affected by movement of the Syrian arc which gradually diminishes southward in the Galala massifs until its effect is very reduced in Wadi Qena. Several Palaeozoic–Jurassic outcrops are exposed on the foot slopes of the Galala massifs through Wadi Araba and underlie the Cretaceous–Eocene rocks. The Campanian–Early Eocene deposits are of carbonate platform facies type that predominate in both Campanian–Early Eocene Stratigraphy of the Southern Galala Plateau, Eastern Desert, Egypt


INTRODUCTION
The Upper Cretaceous-Lower Tertiary rocks are widely distributed all over the Eastern Desert, extending from Gebel Shabrawet in the north, through the Gebel Ataqa and Galala massifs, to Wadi Qena in the south.In the north Eastern Desert (Gebel Shabraweet), these rocks are greatly affected by movement of the Syrian arc which gradually diminishes southward in the Galala massifs until its effect is very reduced in Wadi Qena.Several Palaeozoic-Jurassic outcrops are exposed on the foot slopes of the Galala massifs through Wadi Araba and underlie the Cretaceous-Eocene rocks.
The Campanian-Early Eocene deposits are of carbonate platform facies type that predominate in both

Campanian-Early Eocene Stratigraphy of the Southern Galala Plateau, Eastern Desert, Egypt
Ahmed Aly ISMAIL, Yasmine HUSSEIN-KAMEL, Mohamed BOUKHARY and Ahmed Abdel Aziz GHANDOUR Galalas.The distribution of planktonic and larger foraminifera within the investigated succession allowed an integrated biostratigraphic study to be achieved.Generally, several authors have been involved with the stratigraphy and palaeontology of the Southern Galala Plateau, e.g.FARAG (1954), AWAD & ABDALLAH (1966), ABDALLAH & EISSA (1971), ABDALLAH et al. (1971), MAZHAR et al. (1979), KUSS (1986), KUSS & LEPPIG (1989), SELIMA & ASKALANY (1996), KEHEILA (2000), SCHEIBNER et al. (2000SCHEIBNER et al. ( , 2001)), and ISMAIL & BOUKHARY (2001).There are no publications from the study area, 20 km west of Saint Anthony Monastery (Fig. 1) to nearly the western part of the Southern Galala Plateau.For this reason, the following aims were selected for the study area: (1) to carry out a detailed stratigraphic analysis including lithostratigraphic units and biostratigraphic zones in order to increase the understanding of the nature of the basin of deposition in the Southern Galala plateau during the Late Cretaceous-Early Eocene time.
(2) to determine the relationship between horizons yielding smaller foraminifera (planktonic and benthonic) and those yielding larger ones in order to understand why the Southern Galala has different facies from those recorded in the Western Desert and in Sinai during the same interval.

MATERIAL AND METHODS
A total of 91 rock samples were collected from two surface sections covering the Campanian-Early Eocene succession in the western part of Southern Galala Plateau.The first section, Umm Khayshar (UK) lies 20 km west of Saint Anthony Monastery, and is 139 m in thickness.The second, Umm Damaranah section (UD) is located 30 km west of Saint Anthony Monastery (197 m thickness).Forty nine samples were collected from the Umm Khayshar section covering the Campanian-Maastrichtian, while forty two samples were collected from the Umm Damaranah section covering the Campanian-Early Eocene succession.
The collected samples were described and washed for separating microfossils.These microfossils (plank-tonic and benthic foraminifera) were identified, photographed by Scanning Electron Microscope (SEM) and are illustrated in four plates.For larger foraminifera, normal photography was used.Some samples were pre-pared for thin-sections to study the larger foraminifera, in addition some thin-sections were made through the free tests of these foraminifera.It is worth mentioning that the Umm Khayshar (UK) section starts with the

STRATIGRAPHY
The stratigraphic analysis of the studied rocks depends mainly on the distribution of foraminifera through the Campanian-Early Eocene succession.In intervals that lack foraminifera, macrofossils were used whenever possible.The identified foraminiferal assemblages include planktonic, small benthonic and larger foraminifera that were extracted from the Umm Khayshar and Umm Damaranah measured sections (Figs. 2,3 & 10).The identified foraminiferal assemblages were correlated with the standard Cretaceous biozones of CARON (1985) and the standard Palaeocene-Eocene biozones of TOUMARKINE & LUTERBACHER (1985).Furthermore, the rock units in the study area are the Gebel Thelmet Formation, Sudr Chalk and Southern Galala Formation (Figs. 4 & 5).The lithostratigraphic description, in addition to the faunal content (Figs. 6 & 7) is discussed below.

Late Campanian-Early Maastrichtian deposits
Sediments of Late Campanian and Early Maastrichtian age are widely distributed in the upper parts of the Southern Galala Plateau and the foot slopes of the Northern Galala Plateau facing Wadi Araba.In the lower part they are composed of well-bedded flaky limestone intercalated with chalk and sandstones.In the upper part they consist of fossiliferous, chalky, sandy and argillaceous limestones intercalated with green shales.The thickness of this interval reaches 69 m in the Umm Khayshar section and >40 m in the Umm Damaranah Section.The interval is named the Gebel Thelmet Formation by ABDALLAH & EISSA (1971) at Gebel Thelmet, Southern Galala.It contains some larger foraminifera of stratigraphic significance.
In the Umm Khayshar section, the sequence is characterized by the abundance of Orbitoides media (ARCHI-AC) and Omphalocyclus macroporus (LAMARCK) and overlain by a horizon containing several planktonic and small benthic foraminiferal species of Late Campanian-Early Maastrichtian affinity

( S G ) ( S )
gested Early Maastrichtian age may be partially equated to the Globotruncanella havanensis zone.
In Umm Damaranah, the presence of the larger foraminifera Orbitoides media (ARCHIAC) and Omphalocyclus macroporus ascribe the upper part of the Gebel Thelmet Formation to the Late Campanian (ISMAIL & BOUKHARY, 2001).It is overlain by a nonfossiliferous sequence of chalky limestone, which suggests the extension of its age to the Early?-Middle Palaeocene as evidenced by the appearance of Glomalveolina dachelensis (SCHWAGER) and Fallotella (F.) kochanskae persica HOTTINGER & DROBNE.

Early Maastrichtian deposits
The chalky deposits are widely distributed within this interval, named the Sudr Chalk by GHORAB (1961)

Middle Maastrichtian deposits
These deposits are only recorded at the Umm Khayshar section where they occupy the upper part of the Sudr Chalk.The thickness of this interval attains 30 m.It overlies the Globotruncana aegyptiaca interval zone of the Early Maastrichtian and unconformably underlies the Nummulites cf.subramondi-Alveolina pasticellata horizon of the Early Eocene.This horizon yields the oysters Exogyra overwegi and E. cornuarietis of Middle Maastrichtian age (LUGER, 1985), in addition to large gastropods.This horizon is equivalent to the Gansserina gansseri zone of CARON (1985), SIGAL (1977) and POSTUMA (1971).There are a few beds yielding some long-ranging planktonic foraminiferal species -Heterohelix globulosa, Hedbergella holmedelensis and Contusotruncana fornicate.

Early?-Middle Palaeocene deposits
Early?-Middle Paleocene deposits are only recorded in the Umm Damaranah section and occupy the lower part of the Southern Galala Formation.The thickness of this horizon is 127.5 m.It overlies the Orbitoides media and Omphalocyclus macropora assemblage zone of the Late Campanian and underlies the Morozovella angulata zone of the Middle Palaeocene.This horizon is characterized by a large number of white globular larger fora-

Middle Palaeocene deposits
These are recorded in the Umm Damaranah section, which occupy the middle part of the Southern Galala Formation.The thickness of this zone is 6 m.It overlies the Glomalveolina dachlensis horizon of the Early?-Middle Palaeocene and underlies the Planorotalites peudomenardii zone of Early Late Palaeocene time.This zone is of low diversity, where few species are recorded -Morozovella angulata (WHITE) and Morozovella conicotruncata (SUBBOTINA), in addition to some badly preserved specimens of the same affinity.

Late Palaeocene deposits
Late Palaeocene deposits are only recorded in the Umm Damaranah section, where they comprise the upper part of the Southern Galala Formation and are 14 m thick.

Early Eocene (Ypresian) deposits
These are recorded in the accessible, uppermost part of the Southern Galala Formation in the two measured sections.In the Umm Khayshar section, these deposits unconformably overlie the Exogyra overwegi-E.cornuarietis horizon of Middle Maastrichtian age.However, in the Umm Damaranah section, they overlie the Plano-

TAXONOMIC NOTES
This discussion includes the synonymy, special remarks and stratigraphic distribution for each species.For planktonic foraminifera the Cretaceous scheme of CARON (1985) and the Palaeocene-Eocene scheme of TOUMARKINE & LUTERBACHER (1985) have been followed, while several publications (e.g.HENSON, 1948;OMARA, 1956;SAID & KENAWY, 1956;SAID & BARAKAT, 1957;NEUMANN, 1967;SLITER, 1968;ISMAIL, 1992;BOLLI et al., 1994, etc.) have been used for identification of benthic foraminifera.Furthermore, the Treatise of LOEBLICH & TAPPAN (1988) facilitated the classification of the different genera.The identified small foraminiferal species (Fig. 11) were photographed by Scanning Electron Microscope (SEM) and the larger foraminiferal species, in addition to thin sections were photographed by a high power petrographic microscope, while normal photography was used for separated specimens.The larger foraminiferal species are illustrated in 2 plates.Type specimens of the identified species are deposited in the Geological Museum of the Department of Geology, Faculty of Science, Ain Shams University, Cairo, Egypt (Ismail Collection).

Family Heterohelicidae CUSHMAN, 1927 Genus Heterohelix EHRENBERG, 1843
Heterohelix glabrans (CUSHMAN) Pl. I, Fig. 1 1938 Remarks: This species is easily distinguished by the fine striations on the surface of the test.
Distribution: In the study area, it is recorded from the Umm Khayshar section, sample UK 80, Sudr Chalk (Maastrichtian).
Remarks: This species possesses an imperforate peripheral band in all chambers of the last whorl.Distribution: In the study area, it is recorded from the Umm Khayshar section, sample UK 84, Sudr Chalk (Maastrichtian).
Remarks: This species is characterized by its compact arrangement of the subglobular chambers.
Distribution: In the study area, it is recorded from the Umm Khayshar section, samples UK 80 and UK 100, Sudr Chalk (Maastrichtian).
Remarks: It has 4 chambers in the last whorl and two closely spaced keels.
Distribution: In the study area, it is recorded from the Umm Khayshar section, sample UK 80, Sudr Chalk (Maastrichtian).
Remarks: This species is characterized by inflated chambers on both sides and two widely spaced keels.
Remarks: All chambers of the last whorl are angular conical.Instead of a peripheral keel, delicate spines are concentrated around the periphery and the umbilical shoulders.Distribution: In the study area, it is recorded from the Umm Damaranah section, samples UD 34, Southern Galala Formation (Middle Palaeocene) and samples UD 38 and UD 39, Southern Galala Formation (Late Palaeocene).
Remarks: This species is characterized by its conicotruncate shape in lateral view, with 6 chambers in the last whorl and the chambers are angular conical.
Distribution: In the study area, it is recorded from the Umm Damaranah section, samples UD 34, Southern Galala Formation (Middle Palaeocene).
Remarks: This species has 5 angular conical chambers in the last whorl and it also has a wide umbilicus.
Distribution: In the study area, it is recorded from the Umm Damaranah section, samples UD 37, Southern Galala Formation (Middle Palaeocene).

Remarks:
The early chambers of the last whorl are angular conical and the suture lines on the spiral side are strongly curved backwardly.

Genus Omphalocyclus BRONN, 1853 Omphalocyclus macropora (LAMARCK)
Pl. III, Figs.Remarks: It has a biconcave test, the megalospheric embryo is quadrilocular followed by cycles of arched equatorial chambers.Distribution: Omphalocyclus macropora was recorded from the Upper Cretaceous of Libya by KRUM-BECK (1906), from the Maastrichtian of Switzerland by RENZ (1937), from the Maastrichtian of Holland by NEUMANN (1958), and from the Maastrichtian of Cuba by HANZAWA (1962).In Egypt, it was recorded from the Campanian of Gebel Thelmet, Southern Galala by ISMAIL & BOUKHARY (2001).
In the study area, it is recorded from samples UK 66, UK 67 and UK 71 in the Umm Khayshar section, Gebel Thelmet Formation, Campanian, and samples UD 1, UD 2 and UD 3 from the Umm Damaranah section, also Gebel Thelmet Formation, Campanian.

Family Orbitolinidae MARTIN, 1890
Genus Chamberlets in the last whorls are quadrate and beaded in the early whorls.In the A-form, the last whorls lack a thickened basal layer which is thin, chamberlets beaded all over the test, and the last whorls are narrowly separated, early whorls at regular step size.The proloculus is globular, the diameter of the protoconch is 0.16 mm, diameter of deuteroconch is 0.11 mm., diameter of the test is 3.05 mm, number of whorls per radius are 11 whorls in a radius of 1.44 mm.

SUMMARY AND CONCLUSIONS
The present study is an attempt to throw more light on the stratigraphy of the Southern Galala Plateau.This is a very detailed stratigraphic analysis both lithostratigraphically and biostratigraphically, and has some additional chronostratigraphic implications.The exposed rocks in the area west of the Saint Anthony Monastery have not been previously studied, except for inclusion in some general publications on the Southern Galala Plateau.
The stratigraphic analysis is based on a detailed micropalaeontologic investigation of some Upper Cretaceous rocks exposed in the area west of the Saint Anthony Monastery, Southern Galala, Eastern Desert, Egypt.Two stratigraphic sections were described, measured and sampled -the Umm Khayshar section (139 m thick, 49 samples) and the Umm Damaranah section (197 m thick, 42 samples).The stratigraphic studies subdivided the Campanian-Early Eocene rocks exposed into three rock units.These units are (from base to top): the Gebel Thelmet Formation (Campanian), Sudr Chalk (Maastrichtian) and Southern Galala Formation (Palaeocene-Early Eocene).The distribution of the identified foraminifera either small or large with some macrofos-sil horizons were the main basis for the biostratigraphic studies.
The occurrence of Orbitoides media (ARCHIAC)-Omphalocyclus macropora (LAMARCK) in the Gebel Thelmet Formation, in addition to a reasonable number of small foraminifera in the Umm Khayshar section, defines the Late Campanian-Early Maastrichtian period here.This larger foraminiferal horizon is overlain by chalky deposits (Sudr Chalk of GHORAB, 1961) yielding numerous planktonic foraminiferal species.Among these species, the The Gebel Thelmet Formation represents a continuation of the transgression and deposition in an open marine environment in its lower part, and coastal marine to near shore shelf seas in its upper part.The Sudr Chalk begins with deposition under an open marine environment and ended with sedimentation in a shallow marine environment.The Southern Galala Formation represents deposition in a shallow marine environment (coastal marine).The shallow water carbonates within the Palaeogene stratigraphy of the Southern Galala Plateau yield several larger foraminiferal species of stratigraphic significance.A few beds also contain some planktonic foraminifera, which aids determination of the stratigraphic position of the larger foraminifera.Glomalveolina dachlensis was recorded in the Morozovella angulata zone.This indicates that the stratigraphic level of Glomalveolina dachlensis is possibly Early-Middle Palaeocene.Furthermore, the occurrence of the algae Ethelia album (PFENDER) and Neomeris plagnensis DELOFFRE supports the suggested age for Glomalveolina dachlensis (pers.comm.with Professor J. KUSS).Most of the planktonic foraminifera were poorly preserved which makes it difficult to delineate the Palaeocene/Eocene boundary.The Early Eocene rocks contain Nummulites cf.subramondi.In the Southern Galala, the Early Eocene rocks represent a remarkable sequence that unconformably overlie the Palaeocene rocks and form a steep and vertical inaccessible scarp.4,6,7,11 Orbitoides media (ARCHIAC), 1-3 -external view, specimens from sample UD2, Gebel Thelmet Formation, Campanian (Deposit no.ud 2 1, 2, 3), 4 -axial section, specimen from sample UD 3, Gebel Thelmet Formation, Campanian (Deposit no.ud 3 1), 6-7 -axial section, specimens from sample UK66, Gebel Thelmet Formation, Campanian (Deposit no.uk 66 1, 2), 11 -protochonch of Orbitoides media (ARCHIAC), sample UK66, Gebel Thelmet Formation, Campanian (Deposit no.uk 66 3).

Fig. 2 AFig. 4 A
Fig. 2 A general view of Umm Khayshar section.Fig. 3 A panoramic view of Umm Damaranah section.

FigFig. 6
Fig. 5 A field photograph showing the Gebel Thelmet Formation (T) and the Southern Galala Formation (SG) at the Umm Damaranah Section.

Fig. 11
Fig. 11 Distribution chart of species determined at the Um Damaranah Section.
Remarks: It has 4 chambers in the last whorl and a rounded periphery.Distribution:In the study area, it is recorded from the Umm Khayshar section, samples UK 80, Sudr Chalk (Maastrichtian).1985Rugoglobigerinarugosa(PLUMMER)-CARON,  p. 72,.Distribution: In the study area, it is recorded from the Umm Khayshar section, samples UK 80, Sudr Chalk (Maastrichtian).

Genus Glomalveolina HOTTINGER, 1962 Glomalveolina dachelensis (SCHWAGER)
This genus is characterized by having alternating whorls, the first whorl with discoidal planispiral evolute coiling, the other whorls are of the spiroloculine type of coiling.The outer outline of the test is planispiral involute.There are two types of side pillars, the first type interfinger with the whorls while the other occurs over the whorls.