| Abstract: |
SUMMARY AND CONCLUSIONSThe present work studies the exposed Eocene rocks lying in the central part of the area stretching between the Northern Galala to the south and Gabal Qattamia-Gabal Kahalyia to the north. The study includes the lithologic and microfacies investigations; rEight stratigraphic sections were selected, measured and sampled at west Gabal Um Zeita, Gabal El Nugra, west Gabal Kahalyia, Gabal Um El Reheiat, Gabal Ghraibun, north east Gabal Ghraibun, south Gabal Sad El Naam and Wadi Um Gerfan for completing the stuLITHOLOGIES AND MICROFACIESLithologically, the studied Eocene rocks consist mainly of carbonates which are chalky and cherty in the Lower Eocene, while in the Middle Eocene, they become locally rich in alveolines and Nummulites toward the west, substituted by Dictyoconus and large ROCK UNITSDepending on the field work, lithologic study and microfacies investigation, the studied Eocene successions in the 8 studied sections were assigned to the following rock units :1] Thebes Formation : It is the oldest exposed Eocene rock unit in the studied area and detected from west Gabal Kahalyia section where it lies with unexposed base and reaches 66.6 m. thick. It consists of white to grayish white limestones, moderately com2] Minia Formation : It is detected in west Kahaliya section where it conformably overlies the Thebes Formation and reaches 91 m in thickness. The studied Minia Formation consists of grayish to yellowish white limestones, nummulitic at base, dolomitic and3] Observatory Formation : This unit is the thickest recorded unit in the studied area, it is found in Gabal Nugra, G. Um El Reheiat, south G. Sad El Naam and Wadi Um Gerfan sections with thicknesses of 160.4 m, 21.7 m, 49.3 m and 79.6 m, respectively. It4] Qurn Formation : It consists of lower white to grayish white marly limestone, middle marl to marly limestones and upper yellowish white limestones. This unit is represented by 22.9 m, 37.8 m, 60.5 m and 22.2 m in Wadi Um El Reheiat, Gabal Ghraibun, sou5] Wadi Hof Formation : This is the youngest exposed Eocene unit recorded in studied area at north east Gabal Ghraibun and west Gabal Um Zeita with thicknesses 20.1 m and 15.2 m, respectively; it belongs to the Late Eocene (Priabonian) and lies unconformaFOSSIL CONTENTFaunastically, 123 micro and macrofaunal species have been identified, they include : 58 planktonic, benthonic and large foraminiferal species belonging to 31 genera, 25 families, 20 ostracod species (including 3 new ones) belonging to 15 genera, 9 familiBIOSTRATIGRAPHYSeventeen biozones have been recognized throughout the Lower, Middle and Upper Eocene successions in the eight studied sections. These biozones are 8 microbiozones and 9 macrobiozones, the firsts are 4 range and 4 assemblage biozones of foraminifera only 8- Epinoides schreibersi Zone (Priabonian).7- Nonion cf. graniferum Zone (Priabonian).6- Quinqueloculina carinata Zone (Priabonian).5- Nummulites beaumonti – Nummulites striatus Zone (Lutetian – Bartonian).4- Dictyoconus egyptiensis – Nummulites striatus Zone (Lutetian – Bartonian).3- Dictyoconus egyptiensis – Nummulites beaumonti Zone (Lutetian – Bartonian).2- Alveolina frumentiformis Zone (Early Lutetian).1- Acarinina pentacamerata – Nummulites silvanus Zone (Latest Ypresian).Macrobiozones :B- Pegophysema pharaonis – Vulsella crispata super zone.9- Cassis nilotica – Spondylus egyptiacus Zone (Lutetian – Bartonian).8- Saxolucina rai Zone (Lutetian – Bartonian).7- Ostrea califera Zone (Lutetian – Bartonian).6- Cassis nilotica Zone (Lutetian – Bartonian).5- Lucina immanis Zone (Lutetian – Bartonian).A- Carolia placunoides – Plicatula polymorpha super zone.4- Carolia placunoides Zone (Priabonian).3- Ostrea reili Zone (Priabonian).2- Mesalia shatai Zone (Priabonian).1- Lower interval Zone (Priabonian).The forementioned micro and macrobiozones were correlated inside the studied area and discussed, compared and correlated with similar and equivalent biozones inside and outside Egypt especially the widely extended foraminiferal biozones (see the biostratiCHRONOSTRATIGRAPHYThe 8 studied sections were attributed to the Lower (Ypresian), Middle (Lutetian and Bartonian) and Upper (Priabonian) Eocene stages based on their macro and microfaunal content, biozones, stratigraphic positions and correlation. In ascending order, the d1- The Lower Eocene (Ypresian) :It comprises the lower segment of the exposed succession studied in west Gabal Kahalyia which includes the exposed part of the Thebes Formation. This segment is occupied by the Ypresian Acarenina pentacamerata – Nummulites silvanus Zone and lies conformab2- The Middle Eocene (Lutetian – Bartonian) :a) Lower Lutetian : It is represented by the upper segment of the exposed succession studied at west Gabal Kahalyia which belongs to the Minia Formation and occupied by the early Lutetian Alveolina frumentiformis Zone. This is the only lower part of the Lb) Upper Lutetian – Bartonian : This is represented by the Eocene sediments exposed in Gabal El Nugra, Wadi Um Gerfan, south Gabal Sad El Naam and Gabal Um El Reheiat which belong to the Observatory Formation and/or Qurn Formation. These units are occupiec) Bartonian : It is represented by the exposed part of the Qurn Formation which is occupied by Nummulites beaumonti – Nummulites striatus Zone in Gabal Ghraibun section which most likely have an occurrence in the upper part of the Bartonian, this in addi3- The Upper Eocene (Priabonian) :The sediments of this stage are represented by the exposed parts of Wadi Hof Formation at north east Gabal Ghraibun section and west Gabal Um Zeita section; the first is occupied by the foraminiferal biozones Quinqueloculina carinata Zone, Nonion cf. granPaleoecologically, the recognized microfacies and the recorded fauna indicate that, the studied Eocene successions were deposited generally within usually warm, normal shallow marine to inner neritic conditions; sometimes deep and other times littoral; pr
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