The Association for the Geological Collaboration in JapanJapan{AGCJ) (AGCJ) EARTIg SCIENCE (Chikyu Kagaku) Vol.48,No.2, pp.143"-l57 Mareh1994 143 Ostracodes from Eocene rocks of the El Sheikh Fadl-Ras Gharib stretch, the Eastern Desert, Egypt -Biostratigraphy and paleoenvironments- Ashraf M.T. Elewa' and Kunihiro Ishizaki" Abstract The present study of ostracode faunas from the Eoeene rocks exposed along the El Sheikh Fadl:Ras Gharib streteh in eastern Egypt has resulted in, as shown below, the establishment of biozones and the de]ineation of the distribution of paleoenvironments which prevailed during this period of time. Forty-two ostracode speeies have been dis- criminated in samples collected from 11 sections in the study area. Of these samples 43 which yielded 100 or more ostracode specimens have been grouped under five biotopes as the result of cluster analysis. These biotopes are roek bodies characterized by particular ostracode faunas, and thus provide kernels of three assemblage-and one acme-zones of the middle Eocene, and one assemblage-zone of the lower Eoeene. In consequenee, gener- al paleoenvironments prevailing in the study area during Eocene time can be presumed by stratigraphie and geographie distributions of these biozones. Kbbl u)ords : Eoeene, estraeodes, biostratigraphy, eluster analygig. biozone, depositional environment, Eastern Desert, Egypt. ' Iarge portions of the Eoeene formations. I Introduction The purpose of the present work is to estab- The El Sheikh Fadl-Ras Gharib streteh lish an appropriate zonation of these sediments (about 245km long) extends from Ras Gharib through the use of eluster analysis of the ostra- City on the western coast of the Gulf of Suez in code faunas and to interpret the paleoenviron- the east to El Sheikh Fadl village on the east- ment under which 'the Eocene sediments were ern bank of the River Nile in the west. deposited in the study area. Eleyen sections A number of studies have been done on the were measured and studied. They geographical- Eocene rocks of the study area and their faunal ly extend eastward 5km to 140km from the village contents, but unfortunately only a few of these of El Sheikh Fadl (Fig. 1), These sections eol- studies dealt with ostraeode faunas and their lectively range in age from Paleoeene to middle ･ paleoenvironmental significance, despite these Eocene (Lutetian). creatures being eontained in great abundanee in Received September30, 1993; accepted Decembcr20, 1993 *Departrnent Egypt, of Gcology, Faculty of Seience, El Minla Univer3ity, "Department of Geoenvironmental Science, Faculty of Science, Tohoku University, Sendai 980, Japan. (61) NII-Electronic Library Service The Association for thetheGeological Geological Collaboration in JapanJapan{AGCJ) (AGCJ) 144 Ashraf M. T. Elewa and Kunihiro Ishizaki ifa and Cronin(1979) deseribed 22 ostraeode ll Previous Studies on Eocene Ostra- species including the following nine new speeies: eodes of the EI Sheikh Fadl-Ras Paracg[pris maghaghaensis, Xestoteberis ? ke- Gharib Streteh nawyi, Costa? cameroni, Loxoconcha mataien- The Eocene biostratigraphy of the study area sis, Leguminocythereis hassani, Costa berggreni, has been the subject of many workers, among Anticythereis saitoi, Ctithrocytheridea? tarlaen- them being Cronin and Khalifa(1979), Khalifa sis, and Cytherqpteron boukharyi. and Cronin(1979), Boukhary etal.(1982), and In their study on the Eocene in the Beni Aref(1982)who investigated ostracode assem- Mazar area, Boukhary et al.(1982) discovered blages. the following new ostracode species: Legurninocy- Cronin and Khalifa(1979)studied the Eoeene thereis praesadeki, Anticythereis pemeroli, and ostracodes of Gebel El Mereir and proposed the Echinocythereis bassiounii. following new species: Bythocmpris? rnereiren- During his study on the Eoeene rocks in the sis, Costa nilensis. Costa bassiounii, Digmo- area between Assiut and Beni Suef, cast of the cythere omarai, Anticythereis saidi, Anti- Nile Valley, Aref(1982)reeognized 10 ostracode cuthereis seylingi, Schi2ecythere ladtensis, and species including three new speeies (Anti- addition, Echinocgthereis bassiounii, Loxoconcha pseudopunctatelta. In they cgthereis pomerbti, assigned middle and late Eocene ages to these and Leguminocgthereis praesadeki). ostracode assemblages based on planktonic NQne of the studies mentioned above, howev- foraminiferal species. er, paid much attention to analyses of the pale- In their study of Gebel El Sheikh Fadl, Khal- oenvironmental significance of those ostraeodes. 9'N 2e'E Fig.1 Map showing locations of the sections measured along the EI Sheikh Fadl-Ras Gharib stretch, the Eastern Desert , 1: Gebel EI Sheikh Fadl (GE) section, 2: Gebel El Mohasham (GM) section, 3: seetion at km 8, 4: section A at km IO, 5: section B at km 10, 6: Gebel El Mereir section at km 18, 7: Gebel El Mereir seetion at km 40, 8: Gebel El Mereir section at km 68, 9: Gebel El Mereir section at kn 92, 10: section at km 127, 11:section at km 140. kn refers to the distance (km) from the village of El Sheikh Fadl. (62) NII-Electronic Library Service The AssociationforAssociation for the Geological Collaboration in JapanJapan{AGCJ) (AGCJ) Ostracodes from Eocene rocks of El Sheikh Fadl-Ras Gharib 145 of the section. It eonsists of yellowish white, M Synopsis of Lithostratigraphy of hard Iimestone, showing a papery structure on Eocene Sections of the El Sheikh rmRas weathered surfaces, with dark brown flint pock- Fadl Gharib Stretch ets arranged horizontally in parallel bands. The Eoeene sequence in the study area (Fig. This formation yields a Nitmrnutites speeies in- 2) extends eastward from the village of El dicative of the lower Eocene of Egypt (Said, Sheikh Fadl and is represented by sections on 1960). Khalifa and El Sayed(1984)assigned it an Gebel E] Sheikh Fadl (GE) and Gebel EI Mo- early Eoeene age on the basis of presenee of hasham (GM), at three sites 8 and 10km east of Gtoborotalia pentacamerata Subbotina, 1947, the village of El Sheikh Fad] (km 8 and km 10A, C Maghagha FDrmation B), four sites at km and92 on This 18,4e, 68, Gebel term was first proposed by Bishay(1966) EI Mereir, and twQ sites at km 127and140. to designate the chalk-marl complex exposed These sections can be divided into the follow- at Maghagha district on ･the Nile Valley instead "B" ing roek units in upward sequenee based on of the informal term formation used by lithologie features : Barker(1945). A Esna Formation In the study area, the Maghagha Formation The term Esna Shale was originally intro- is exposed in the GE seetion (the type section duced by Beadnell(1905)to describe the thiek as designated by Azab(1984)), another sectien shale of Gebel Aweina near Esna. Said(196e, at km 8, seetions A and B at km 10, and at the 1971)used the term Esna Formation to designate base of the Gebel El Mereir section at km 18. the shale outcropping in the suecession of north- It consists of alternating beds of white, mod- ern Wadi Qena. erately hard, chalky limestone ancl grayish In the study area, the Esna Formation lies white to yellowish white, soft to moderately 14ekm east of the village of El Sheikh Fadl(km hard marl. The Maghagha Formation reaehes 14e), It is composed of gray to dark gray, soft its maximum thickness (about 8L30m) in the to moderately hard, gypsiferous shale (about 5 study area at the GE section. T.his formation m thiek) in the lower part of the seetion. Said has been plaeed in the middle Eocene on the (1960) first reported the fauna of planktonie basis of presence of Orbutinoides beckmanni foraminifers from this formation, whieh he con- (Saito, 1962) (Omara et al., 1977) or Globoro- sidered to be indicative of the Paleocene (Lan- talia cerroaxulensis frontosa (Subbotina, 1953) denian). Khalifa and EI Sayed(1984)assigned and Globorotatia cerroa2ulensis possagnoensis this formation an late Paleocene age on the ba- (Toumarkine and Bolli, 1970) (Boukhary et al., sis of presence of aloborotatia vetascoensis 1982).D Cushman, 1925. Qarara Formation B Thebes Formation The term Qarara Formation was introdueed The Thebes Formation was originally de- by Bishay(1966)to designate the sequence of scribed by Said(1960)in the Gebel Gurnah area Gebel Qarara whi ¢ h forms the northern bound- (opposite Luxor); he later assigned the same ary of the Maghagha distriet ("C" formation of term to limestone overlying the Esna Formation Barker(1945)). This sequenee is eomposed of in northern Wadi Qena (Said, 1971), calcareous quartz sandstone and elay very rich In the study area, the Thebes Formation is in nummulites and maerofossils (Azab, 1984). observed at two outcrops at km 127 and km 140. In the study area, it is represented by yellow- In the section at km 127 it composes the whole ish white, very hard caleareous sandstone and thickness of the section (about 25m), while in grecnish white to gray, moderately hard shale the section at km 140 it occupies the upper part rieh in macrofossils and nummulites. This se- (63) NII-Electronic Library Service The Association for thetheGeologicalCollaboration Geological Collaboration inJapan{AGCJ)in Japan (AGCJ) 146 AshrafM. T. Elewaand Kunihiro Ishizaki km 18 km 140 shalewa va Martg e Lirnestone Calcareous shale Tg Sandy shale as Clayey limestone ss CalcareoussandstoAe ge Sandy limestone as [Ig] ew Sandy ctayey limestone Fig. 2 Columnar sections of Eocene roeks in the study area. 1 to11: loeations referring to those in Fig. 1, S3 to W3: horizons of samples subjected to cluster analysis and pertain to those in Fig. 3, vertical wavy lines on both sides of GM section show presumed interfingering relationships between the Maghagha and Qarara Formations. quence is obscrved in the GM section and the Qarara Formation. Gebel El Mereir seetions at km 18, 40, 68, and In the study area, it is also represented by 92, and reaehes its maximum thickness of white limestone which intercalates flint bands and bryozoans but about 91,30 m at km 18.