Journal of African Earth Sciences 100 (2014) 379–400

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Journal of African Earth Sciences

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Integrated biostratigraphy of the upper Oligocene–middle Miocenesuccessions in west central Sinai, Egypt

http://dx.doi.org/10.1016/j.jafrearsci.2014.07.0071464-343X/� 2014 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Tel.: +20 02 22475060, mobile: +20 01002660758.E-mail addresses: ahewaidy@hotmail.com, ahewaidy50@yahoo.com

(A.G.A. Hewaidy).

Abdel Galil A. Hewaidy a,⇑, Sherif Farouk b, Haitham M. Ayyad a

a Geology Department, Faculty of Science, Al-Azhar University, Nasr City, Cairo, Egyptb Exploration Department, Egyptian Petroleum Research Institute, Nasr City, Egypt

a r t i c l e i n f o a b s t r a c t

Article history:Received 21 April 2014Received in revised form 13 July 2014Accepted 15 July 2014Available online 31 July 2014

Keywords:Calcareous nannofossilsPlanktonic foraminiferaOligo-MioceneBiostratigraphyWest central SinaiEgypt

The nannofossil and planktonic foraminiferal biostratigraphy in four upper Oligocene–middle Miocenesections are examined in Nukhul–Sudr area of west central Sinai, Egypt. The integration of calcareousnannofossils and planktonic foraminifera is used to verify the ages and determine the biozones of theupper Oligocene–middle Miocene units in the studied area. This target is important in the light of thegreat lithofacies changes during the time interval. The detailed examination of the nannofossil andplanktonic foraminiferal contents in these sections led to identification of 86 calcareous nannofossilspecies belonging to 22 genera, 10 families and 3 orders, in addition to 64 planktonic foraminiferal spe-cies belonging to 11 genera, 4 families and 2 superfamilies. The identified nannofossil and planktonicforaminiferal assemblages allow to distinguish five calcareous nannofossil biozones and six planktonicforaminiferal biozones. The biostratigraphic integration suggested the Chattian–Aquitanian age for theNukhul Formation where the Globigerina ciperoensis Zone (P22) and Globigerinoides primordius Zone(M1a) correspond to calcareous nannofossil Sphenolithus ciperoensis Zone (NP25) and Discoaster druggiiZone (NN2), respectively. The Rudeis Formation is assigned to the Burdigalian–Langhian age dependingon correspondence of Catpsydrax dissimilis Zone (M2), Globigerinoides bisphericus Zone (M4b) andPraeorbulina sicana Zone (M5) with Discoaster druggii zone (NN2), Sphenolithus belemnos Zone (NN3)and Helicosphaera ampliaperta Zone (NN4). The Somar Formation is found barren ofany microfossils,but it contains index pectens and oysters of Burdigalian age which may be equivalent to the lower partof the Rudeis Formation. The Kareem and Sarbut El-Gamal formations are represented by evaporitic andconglomeratic succession, where no foraminifera or nannofossils are recorded and assigned to theLanghian age according to their stratigraphic position. The Belayim Formation is assigned to theSerravallian age, due to the presence of Globorotalia fohsi Zone (M8) which equivalent to Discoaster exilisZone (NN6).

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

The exposed upper Oligocene–middle Miocene sections of westcentral Sinai are characterized by obvious rapid lateral and verticallithologic variations. The enable of correlation between these sec-tions is a matter of difficulty and lack of precision. Many attemptshave been made in the past decades to determine the ages of dif-ferent Oligo-Miocene units and correlate between them (e.g.Said, 1962; Souaya, 1965, 1966; Said and El Heiny, 1967; Wasfi,1968; National Stratigraphic Sub-Committee (NSSC), 1974;Garfunkel and Bartov, 1977; Andrawis and Abdel Malik, 1981;El-Heiny and Martini, 1981; El-Heiny and Morsi, 1992; Haggag

et al., 1990; El-Azabi, 1996, 1997, 2004; Phillip et al., 1997;Amundsen et al., 1998; Abul-Nasr and Salama, 1999; Shahin,2000; Sadek, 2001; El-Deeb et al., 2004; Faris et al., 2009). In theseworks, the Nukhul Formation was assigned to the early Mioceneage based on calcareous nannofossils, the planktonic and/or ben-thonic foraminifera.

Contrary to these attempts Hewaidy et al. (2012) at Wadi Babaarea assigned the Nukhul Formation to the late Oligocene (Chat-tian)–early Miocene (Aquitanian) age. This conclusion magnifiedthe role of integration in solving the age problem of the Mioceneunits in west central Sinai area.

This study aims to integrate calcareous nannofossil and plank-tonic foraminiferal zonations to make more precise division ofsequential access to correlate the upper Oligocene–middle Mio-cene sections of the study area by means of high-resolution inte-grated biostratigraphy.

380 Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400

2. Material and methods

The material and methods on which this study carried out bythe examination of four upper Oligocene–middle Miocene sectionslocated in Nukhul–Sudr area, west central Sinai, Egypt. These arefrom south to north: Wadi Nukhul (Latitude 29�0103000 and Longi-tude 33�1103000), Gabal Sarbut El-Gamal (Latitude 29�07015.6600 and

Fig. 1. Geological map (modified after Moustafa, 2004), showing

Longitude 33�12029.8200), Wadi Wasit (Latitude 29�1303000 and Lon-gitude 32�56054.5800) and Wadi Sudr (Latitude 29�4105500 andLongitude 32�5304100) (Fig. 1). About one hundred and sixty sam-ples were collected from the studied successions and their calcar-eous nannofossils and foraminiferal species were prepared. Theabundances of calcareous nannofossil species were countedfor each sample using a Prior Photomicroscope under X1200

the distribution of the measured sections in the study area.

Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400 381

magnification, by using cross-polarized and phase-contrast light.The identified foraminiferal species are scanning photographed inlaboratories of the Regional Center for Mycology and Biotechnol-ogy of Al-Azhar University.

3. Lithostratigraphy

The upper Oligocene–middle Miocene successions exposed inwest central Sinai are measured in four sections. These sectionsare represented by 6 formations of which the Nukhul, Rudeis andBelayim are fossiliferous while Somar, Kareem and Sarbut El-Gamal formations are barren. At Wadi Nukhul section the NukhulFormation rests unconformably over the Tayiba (Red Beds) Forma-tion. At Gabal Sarbut El-Gamal section three formations wererecorded from base to top as follow; Rudeis, Sarbut El-Gamal andBelayim formations from base to top. Nukhul and the overlyingRudeis formations are recorded at Wadi Wasit section. Towardsnorth at Wadi Sudr section; the Mheiherrat Member of the RudeisFormation is replaced by the Somar Formation, () as the Mheiherrat

Plate 1. 1. Zygrhablithus bijugatus (Deflandre & Fert), sample No. 87. 2. Triquetrorhabdulus88. 5–6. Coccolithus miopelagicus Bukry, sample No. 7. 7–8. Coccolithus pelagicus (WallichIlselithina fusa Roth, sample No. 88. 11. Discoaster adamanteus Bramlette and Wilcoxon. 12Bramlette and Wilcoxon, sample No. 99. 15. Discoaster variabilis Martini & Bramlette, s(Bramlette & Riedel, sample No. 137. 18–19. Helicosphaera ampliaperta Bramlette & WiHelicosphaera mediterranea Muller, sample No. 106. 24–25. Helicosphaera scissura MilleCyclicargolithus floridanus (Roth and Hay in Hay et al.), sample No. 132. 29. ReticulofeneBramlette and Wilcoxon, sample No. 103. 33. Sphenolithus dissimilis Bukry and PercivalSphenolithus ciperoensis Bramlette & Wilcoxon, sample No. 86.

clays are replaced by algal limestones; (EGSMA’s field project;1994 and Abul-Nasr et al., 2009). The Somar Formation is directlyoverlain by the Asl and Mreir member of the Rudeis Formation,Kareem and Belayim formations.

This obvious rapid lateral and vertical lithologic variations willmake correlation between these sections is a matter of complexityand lack of accuracy. This suggests that high resolution integratedbiostratigraphy will enhance the knowledge on the lateral faciesvariability and ages of rock units.

4. Faunal pattern

In the present study, 86 calcareous nannofossil species belong-ing to 22 genera, 10 families and 3 orders, in addition to 64 plank-tonic foraminiferal species belonging to 11 genera, 4 families and 2superfamilies were identified. The SEM photographs of importantspecies were taken and shown on Plate 1 for the nannofossil spe-cies and Plates 2 and 3 for the planktonic foraminiferal species.

milowii Bukry, sample No. 129. 3–4. Chiasmolithus altus Bukry & Percival, sample No.), sample No. 99. 9. Calcidiscus macintyrei (Bukry and Bramlette), sample No. 41. 10.–13. Discoaster deflandrei Bramlette and Riedel, sample No. 99. 14. Discoaster druggiiample No. 99. 16. Discoaster braarudii Roth, sample No. 76. 17. Hayaster perplexuslcoxon, sample No. 76. 20–21. Helicosphaera euphratis Haq, sample No. 28. 22–23.r, sample No. 99. 26–27. Cyclicargolithus abisectus (Müller) , sample No. 132. 28.stra bisecta (Hay, Mohler and Wade), sample No. 88. 30–32. Sphenolithus belemnos, sample No. 41. 34–35. Sphenolithus heteromorphus Deflandre, sample No. 68. 36.

Plate 2. 1. Globorotalia fohsi (Cushman & Ellisor), sample No. 76. 2–3. Globorotalia peripheroacuta Blow & Banner, sample No. 76. 4–5. Globorotalia peripheroronda Blow &Banner, sample No. 76. 6–8. Catpsydrax dissimilis (Cushman & Bermudez), sample No. 131. 9–11. Globoquadrina altispira altispira (Cushman & Jarvis), sample No. 53. 12–14.Globoquadrina dehiscens (Chapman, Parr, & Collins), sample No. 53. 15–17. Globigerina angulisuturalis Bolli, sample No. 86. 18–20. Globigerina angustiumbilicata Bolli, sampleNo. 99. 21–23. Globigerina ciperoensis ciperoensis Bolli, early Miocene (Aquitanian), sample No. 99. 24–26. Globigerina ciperoensis fariasi Bolli, sample No. 99. 27–29. Globigerinaouachitaensis gnaucki Blow & Banner, sample No. 97. 30–31. Globigerina ouachitaensis ouachitaensis Howe & Wallace, sample No. 98. 32–34. Globigerina praebulloidespraebulloides Blow, sample No. 99. 35–36. Globigerina praebulloides leroyi Blow & Banner, sample No. 134. 37–39. Globigerina praebulloides occulusa Blow & Banner, AslMember of the Rudeis Formation, Gabal Sarbut El-Gamal section, sample No.

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Plate 3. 1-3. Globigerinella obesa (Bolli), sample No. 99. 4–6. Globigerinoides altiaperturus Bolli, sample No. 99. 7–9. Globigerinoides bisphericus Todd, sample No. 131. 10–11.Globigerinoides conglobatus (Brady), sample No. 47. 12–14. Globigerinoides diminutus Bolli, sample No. 54. 15–17. Globigerinoides immaturus LeRoy, sample No. 99. 18–20.Globigerinoides primordius Blow & Banner, sample No. 99. 21–23. Globigerinoides ruber (d’Orbigny), sample No. 53. 24–26. Globigerinoides sacculiferus (Brady), sample No. 129.27–29. Globigerinoides subquadratus Brönnimann, sample No. 53. 30–32. Globigerinoides trilobus Reuss, sample No. 53. 33. Orbulina universa d’Orbigny, sample No. 76. 34–36.Praeorbulina sicana Di Stefani, sample No. 62.

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384 Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400

The faunal assemblage of the Nukhul Formation in Wadi Nukhulsection is very rare and badly preserved. Only 5 samples of thetotal 30 include this assemblage, while the others are barren andinclude reworked fauna. Preservation of these fossils ranges frommoderate to poor.

On the other hand, Gabal Sarbut El-Gamal section is highly fos-siliferous in the Rudeis and lower part of the Belayim formations.Meanwhile, the Sarbut El-Gamal Formation and the upper part ofthe Hammam Faraun Member of the Belayim Formation arebarren.

The faunal content of the succession of Wadi Wasit section isless abundant. The Nukhul Formation in this section yields (Chat-tian–Burdigalian) calcareous nannofossil and foraminiferal assem-blages. The faunal content of Wadi Sudr section is relatively poor.

5. Biostratigraphy

5.1. Calcareous nannofossil biozones

Unfortunately detailed Oligo-Miocene has been never estab-lished because of discontinuous occurrence of calcareous nanno-fossils. This allows evaluation of the classic biozonal markers andprovides quantitative abundance patterns for supplementaryevents, and improving the biostratigraphic resolution.

A succession of bioevents is observed in the present study fromChattian Zone NP25 to Serravallian Zone NN6. Two major hiatusesin the lowest part of the lower Miocene and middle Miocene

Fig. 2. Abundance of the main taxa of zone NP25 at Wadi Wasit section. The abundanceoccurrence.

respectively, interrupt the sedimentary record and the sequenceof bioevents. Each biostratigraphic event (called ‘‘biohorizon’’ inthis study) is mainly based on the species well-reported fromEgypt. A biohorizon possibly exists at any place between two near-est significant samples. In this study, we assume that each biohor-izon is located at the midpoint between the two samples. Asynthesis of the major biohorizons was proposed based on the firstoccurrence (FO) and last occurrence (LO) of each taxon.

The biostratigraphic zonal schemes of the standard zonations ofMartini (1971) and Perch-Nielsen (1985) have been used for thestudied successions. Five calcareous nannofossil biozones are iden-tified in the present study (Figs. 6–9).

5.1.1. Sphenolithus ciperoensis Zone (NP25)Definition: It is defined from LO of Sphenolithus distentus to the

LO of Sphenolithus ciperoensis (Perch-Nielsen, 1985). In the presentstudy, it is characterized by a biostratigraphic interval of partialrange of Sphenolithus ciperoensis below the FO of Discoaster druggii(Fig. 6).

Authors: Bramlette and Wilcoxon (1967).Age: Late Oligocene (Chattian).Bioevents: Martini (1971), Bukry (1973), Müller (1978) and

Perch-Nielsen (1985); used the LO of Sphenolithus ciperoensis todefine the top of zone NP25 of Chattian age. In the studied areathe Sphenolithus ciperoensis has it’s LO in the upper Oligocene(Chattian) at Wadi Wasit section in the lower part of the NukhulFormation. The abundance pattern and the range of Sphenolithus

scale is expressed as number of specimens per mm2. LO = Last occurrence. FO = First

Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400 385

ciperoensis at Wadi Wasit is shown in (Fig. 2). The LO of theZygrhablithus bijugatus nolfi and Reticulofenestra bisecta are thebioevents used for an approximation of the NP25/NN1 boundary,Perch-Nielsen (1985). This bioevent is observed in sample No. 88at Wadi Wasit section in the lower part of the Nukhul Formation(Fig. 2). The abundance pattern and the range of Zygrhablithusbijugatus nolfi and Reticulofenestra bisecta at Wadi Wasit areshown in (Fig. 2). Perch-Nielsen (1985); mentioned thatTriquetrohabdulus millowii is found in zone NP25. This speciesis recognized in the lower part of the Nukhul Formation at WadiWasit (Fig. 2) and the abundance pattern is illustrated in (Fig. 2).Chiasmolithus altus disappears towards the end of the Oligoceneand this event was detected by Waghorn (1985) to define a zonalboundary corresponding to the NP24/NP25. In the present study,Chiasmolithus altus, which is the youngest representative of thegenus has its LO in the upper Oligocene (Chattian) (sample 88),in the lower part of the Nukhul Formation at Wadi Wasit section(Fig. 2). Gartner (1992); used Ilselithina fusa as a marker, andmentioned that Ilselithina fusa is represented by two morpho-types. The first morphotype, present in the Oligocene, with 12–14 petals in the basal cycle of elements, and the second one iswith six elements and is restricted to the lower Miocene. Thespecimens recovered from the studied successions have 10–14proximal elements (see transferred specimen Pl. 1, Fig. 10). TheLO of Ilselithina fusa coincides with the LO of Sphenolithuscapricornutus and it is recorded at Wadi Wasit section in thelower part of the Nukhul Formation (Fig. 2) and its abundancepattern is illustrated in (Fig. 2).

Stratigraphic position: It is recorded in the lower part of theNukhul Formation at Wadi Wasit (Fig. 6).

Correlation: This zone is equivalent to Sphenolithus ciperoensisZone (NP25) of Martini (1971), Bukry (1973), Müller (1978) andPerch-Nielsen (1985) (Fig. 10). It is not recorded in west centralSinai area. Hewaidy et al. (2012) yielded a late Oligocene nannofos-sil of NP24 Zone from Wadi Baba section.

5.1.2. Discoaster druggii Zone (NN2)Definition: It is defined from FO of Discoaster druggii to the LO

of Triquetrohabdulus carinatus (Perch-Nielsen, 1985). In the presentstudy, Triquetrohabdulus carinatus was not recorded and thiszone is characterized by a biostratigraphic interval between theFO of Discoaster druggii to the FO of Sphenolithus belemnos (Figs. 6and 7).

Authors: Martini and Worsley (1970).Age: Early Miocene (Aquitanian).Bioevents: Both Martini (1971) and Okada and Bukry (1980);

used the FO of Discoaster druggii in their zonal schemes to definethe base of Zone NN2 and the base of Subzone CN1c, respectively.In the present study the FO of Discoaster druggii is recognized in thelower Miocene (Aquitanian) in sample No. 95 and sample No. 8 atWadi Wasit and Wadi Nukhul sections, respectively in the upperpart of the Nukhul Formation (Figs. 2 and 4). The FO of Helicosphaeraampliaperta coincides with the FO of Discoaster druggii. The presenceof Discoaster druggii together with Helicosphaera ampliaperta is rec-ognized in the upper part of Zone (NN2) of Perch-Nielsen (1985);indicating the absence of the lowermost zone in the Miocene(NN1) in addition to the lower part of Zone (NN2). The abundancepattern and the range of both Discoaster druggii and Helicosphaeraampliaperta at Wadi Wasit are illustrated in (Fig. 3). The first occur-rence (FO) of Hayaster perplexus has its FO at the base of NN2 accord-ing to zonal scheme of Perch-Nielsen (1985). This bioevent coincideswith the FO of both Discoaster druggii and Helicosphaera ampliapertain the upper part of the Nukhul Formation at Wadi Nukhul section(Fig. 3).

Stratigraphic position: It is recorded in the upper part of theNukhul Formation and in Mheiherrat Member of the Rudeis For-mation at Wadi Wasit and Wadi Nukhul sections (Figs. 6 and 7).

Remarks: According to Perch-Nielsen (1985), Helicosphaeraampliaperta Bramlette and Wilcoxon (1967), associated withDiscoaster druggii Bramlette & Wilcoxon indicate the upper partof Zone NN2 which is the case in the present study (Fig. 3).

Correlation: This zone may be equivalent to the upper part ofZone (CN1) of Bukry (1973) and Okada and Bukry (1980)(Fig. 10). It is also equivalent to the upper part of Zone (NN2) ofMartini (1971), Bukry (1973), Müller (1978) and Perch-Nielsen(1985). It is correlated with Zone (NN2) of Mandur (2009) andMarzouk (2009) in the Gulf of Suez region and equivalent to Zones(MNN2 a and b) of Fornaciari and Rio (1996) (Fig. 10).

5.1.3. Sphenolithus belemnos Zone (NN3)Definition: It is defined from LO of Triquetrohabdulus carinatus

to the LO of Sphenolithus belemnos (Martini, 1971). In the presentstudy, it is characterized by common and continuous presence ofSphenolithus belemnos.

Authors: Bramlette and Wilcoxon (1967), emend. Martini(1971).

Age: Early Miocene (Burdigalian).Bioevents: The LO of Sphenolithus belemnos was used by Bukry

(1973), Okada and Bukry (1980) and Perch-Nielsen (1985); as abioevent to determine the top of Zone NN3. In the present studythe LO of Sphenolithus belemnos coincides with the LO of Sphenolithusconicus. These bioevents were observed in the Hawara Member ofthe Rudeis Formation in sample No. 38 at Gabal Sarbut El-Gamalsection indicating the presence of Zone NN3 in this rock unit(Fig. 4). The abundance pattern and the range of both of Sphenolithusbelemnos and Sphenolithus conicus are illustrated in (Fig. 4).

Stratigraphic position: It is recorded in Hawara Member of theRudeis Formation at Gabal Sarbut El-Gamal (Fig. 8).

Correlation: This zone may be equivalent to Zone (CN2) ofBukry (1973) and Okada and Bukry (1980) (Fig. 10). It is correlatedwell with Sphenolithus belemnos Zone (NN3) of Martini (1971),Perch-Nielsen (1985), Mandur (2009) and Marzouk (2009)(Fig. 10). It may be equivalent to the lower part of Zone (NN3) ofMüller (1978) (Fig. 10). It may be equivalent to the upper part ofZone (MNN3a) of Fornaciari and Rio (1996).

5.1.4. Helicosphaera ampliaperta Zone (NN4)Definition: It is defined from the LO of Sphenolithus belemnos to

LO of Helicosphaera ampliaperta Martini (1971). In the presentstudy, it is characterized by a biostratigraphic interval of FO ofSphenolithus heteromorphus with presence of Helicosphaeraampliaperta above the LO of Sphenolithus belemnos (Fig. 8).

Authors: Bramlette and Wilcoxon (1967), emend. Martini(1971).

Age: Early Miocene (Burdigalian) to middle Miocene (Langhian).Bioevents: Sphenolithus heteromorphus has its FO at the base of

zone NN4 according to zonal scheme of Perch-Nielsen (1985) andDe Kaenel and Villa (1996). This bioevent is observed in the upperpart of the Hawara Member and in the lower part of the Asl Mem-ber of the Rudeis Formation at Wadi Sudr and Gabal Sarbut El-Gamal, respectively (Figs. 4 and 9) and its abundance pattern andthe range are shown in (Figs. 4 and 8). Calcidiscus macintyrei isfound rare in the upper part of Helicosphaera ampliaperta ZoneNN4 Perch-Nielsen (1985). Calcidiscus macintyrei has its FO in theHawara Member at Wadi Sudr (Fig. 5) and in the Asl Member atGabal Sarbut El-Gamal (Fig. 4). Helicosphaera euphratis becomesrare and often disappears in the upper part of zone NN4 Perch-Nielsen (1985). The LO of Helicosphaera euphratis is recognized inthe upper part of the Asl Member at Gabal Sarbut El-Gamal section(Fig. 4). Bramlette and Wilcoxon (1967) and Martini (1971); used

Fig. 3. Abundance of the main taxa of zone NN2 at Wadi Nukhul section. The abundance scale is expressed as number of specimens per mm2. LO = Last occurrence. FO = Firstoccurrence.

386 Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400

this event to determine the top of NN4. The LO of Helicosphaeraampliaperta is recorded in the upper part of the Mreir Member ofthe Rudeis Formation at Gabal Sarbut El-Gamal (Fig. 4).

Stratigraphic position: It is recorded in the Hawara, Asl andMreir members of the Rudeis Formation at Wadi Sudr and GabalSarbut El-Gamal (Figs. 7 and 8).

Correlation: It may be equivalent Zone (CN3) of Bukry (1973)and Okada and Bukry (1980) (Fig. 10). It is correlated well withHelicosphaera ampliaperta Zone (NN4) of Martini (1971), Perch-Nielsen (1985), Mandur (2009) and Marzouk (2009) (Fig. 10) andit is equivalent to Zone NN3 and the lower part Zone (NN4) ofEl-Heiny and Martini (1981) and equivalent to Zones (MNN3b &MNN4a) of Fornaciari and Rio (1996) (Fig. 10).

5.1.5. Discoaster exilis Zone (NN6)Definition: It is defined from the LO of Sphenolithus heteromorphus

to FO of Discoaster kugleri and/or LO of Cyclicargolithus floridanusMartini (1974). In the present study, it is defined from the FO of Dis-coaster braarudii which is a marker species for this zone (Perch-Nielsen, 1985) (Fig. 8).

Authors: Hay (1970), emends. Martini (1974).Age: Middle Miocene (Serravallian).Bioevents: Discoaster braarudii which is slender, six-rayed with

non-tapered arms appears near the base of Zone NN6 Perch-Nielsen (1985). It is recorded in the Hammam Faraun Member ofBelayim Formation at Gabal Sarbut El-Gamal (sample No. 76)(Fig. 4). The abundance pattern and the range of Discoaster braarudiiis shown in (Fig. 4).

Stratigraphic position: It is recorded in the Hammam FaraunMember of the Belayim Formation at Gabal Sarbut El-Gamal(Fig. 8).

Remarks: Discoaster braarudii appears near the base of thiszone; (Perch-Nielsen, 1985) (Fig. 4). Cyclicargolithus floridanusdecreases in abundance and it is replaced by abundant Reticulofen-estra pseudoumbilica; (Perch-Nielsen, 1985) (Fig. 4).

Correlation: It may be equivalent Zone (CN5) of Bukry (1973)and Okada and Bukry (1980) (Fig. 10). It is correlated with Discoasterexilis Zone (NN6) of Martini (1971), Perch-Nielsen (1985), Mandur(2009) and Marzouk (2009) and equivalent to the upper part Zone(NN5) of El-Heiny and Martini (1981) (Fig. 10).

Fig. 4. Abundance of the main taxa of zone NN3, NN4 and NN6 at Gabal Sarbut El-Gamal section. The abundance scale is expressed as number of specimens per mm2.LO = Last occurrence. FO = First occurrence.

Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400 387

5.2. Planktonic foraminiferal biozones

Six planktonic foraminiferal biozones are distinguished in thestudied successions which are discussed as follows from older toyounger. The distribution charts of the identified planktonic spe-cies are shown on Figs. 11–14.

5.2.1. Globigerina ciperoensis Zone (P22)Definition: Originally this zone is characterized by a partial

range of the nominate taxon between the last occurrence (LO) ofGlobigerina opima opima to the first occurrence (FO) of Globorotaliakugleri. The two marker species characterizing the lower and upperboundaries of this zone are not recorded in the studied successions.Some authors (e.g. Haggag et al., 1990; Ouda, 1998) noted theabsence of Globorotalia kugleri in the Gulf of Suez area. Thus,the zone is identified as the interval with the nominate taxon tothe FO of Globigerinoides spp.

Authors: Cushman and Stainforth (1945) and emended by Bolli(1957).

Age: Late Oligocene (Chattian).Stratigraphic position: It is recorded in the lower part of the

Nukhul Formation at Wadi Wasit (Fig. 11). This biozone attains athickness of about 20 m, and covers samples 83–93. It coincideswith the calcareous nannofossil Zone NP25 of Chattian age, andit is marked by high diversity with moderately preserved plank-tonic foraminiferal elements (Fig. 11).

Remarks: The presence of the Globigerina ciperoensis group andother small-sized planktonic forams in addition to the absence ofany Globigerinoides spp., indicate a late Oligocene age. The Globigerinaciperoensis group (Globigerina ciperoensis and Globigerina angustium-bilicata) was best-adapted in the late Oligocene (Bolli, 1957;

Postuma, 1971; Bolli and Saunders, 1985; Kennett and Srinivasan,1983); noted that Globigerina ciperoensis is a valuable index for thelate Oligocene but is rare in the early Miocene.

Correlation: This zone is equivalent to Globigerina angulisuturalisZone (N3) of Blow (1969) (Fig. 15). It is also equivalent to Globigerinaciperoensis Zone (P22) of Berggren et al. (1995). It is correlated withGlobigerina ciperoensis Zone (P22) of Hewaidy et al. (2012) in theGulf of Suez region.

5.2.2. Globigerinoides primordius Interval Subzone (M1a)Definition: Berggren et al. (1995) subdivided the Globorotalia

kugleri Total Range Zone into two subzones; the Globigerinoidesprimordius Interval Subzone (M1a) and the Globorotalia kugleri/Globoquadrina dehiscens Concurrent Range Subzone. TheGlobigerinoides primordius Subzone is defined by the biostrati-graphic interval of the nominate taxon between the FO ofGloborotalia kugleri and the FO of Globoquadrina dehiscens. In thepresent study, this subzone is defined by the total range of thenominate taxon. The subzone M1b which includes the biostrati-graphic interval between the (FAD) Globoquadrina dehiscens andthe (LAD) of Paragloborotalia kugleri was not recorded in the stud-ied successions and not recognized in the Gulf of Suez region(Wasfi, 1968; El-Heiny and Martini, 1981).

Authors: Blow (1969) and Berggren et al. (1995).Age: Early Miocene (Aquitanian).Stratigraphic position: It is recorded in the upper part of the

Nukhul Formation at Wadi Wasit and Wadi Nukhul sections(Figs. 11 and 12). This subzone attains a thickness of about 30 m(samples 94–107) at Wadi Wasit section and 65 m (samples 5–30) at Wadi Nukhul section. The distribution of the identifiedplanktonic elements is shown on Figs. 11 and 12.

388 Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400

Remarks: A marked change in the size, preservation and diver-sity of the foraminiferal fauna from Chattian to Aquitanian arenoted. A change from small-sized and limited diversity to large-sized and high diversity represented the transition from Chattianto Aquitanian faunas. The FO of Globigerinoides has widely beenaccepted as the datum for the Oligocene/Miocene boundary(Banner and Blow, 1965; Bolli, 1966; Cita, 1976; Bolli andPremoli Silva, 1973; Blow, 1969, 1979; Bolli and Saunders, 1985;Haggag et al., 1990; Phillip et al., 1997; El-Deeb et al., 2004).

Correlation: This subzone is equivalent to the lower part ofGlobigerinoides primordius/Globorotalia kugleri Zone (N4) of Blow(1969). It is also equivalent to Globigerinoides primordius Zone(M1a) of Berggren et al. (1995) and equivalent to the lower partof Globigerinoides trilobus Zone of Jenkins, 1985. It is correlatedwith Globigerina ciperoensis Zone (M1a) of Hewaidy et al. (2013)in the Gulf of Suez region (Fig. 15).

5.2.3. Catpsydrax dissimilis Zone (M2)Definition: Berggren et al. (1995), illustrated that this zone is

characterized by a biostratigraphic interval of the nominate taxonbetween LO Globorotalia kugleri and the FO of Globigerinatellainsueta. The two marker species characterizing the lower andupper boundaries of this zone are not recorded in the studiedsuccessions. It is identified by the biostratigraphic interval of thenominate taxon above the LO of Globigerinoides primordius.

Author: Cushman and Renz (1942); emended by Bolli (1957),Blow (1969) and Berggren et al. (1995).

Age: Early Miocene (Burdigalian).

Fig. 5. Abundance of the main taxa of zone NN4 at Wadi Sudr section. The abundance soccurrence.

Stratigraphic position: It is recorded in the Mheiherrat Mem-ber of the Rudeis Formation at Wadi Wasit and in the lower partof the Hawara Member of the Rudeis Formation at Wadi Sudr. Itattains a thickness of about 10 m (samples 106–107) at WadiWasit and 40 m (samples 129–139) at Wadi Sudr. The distributionof the planktonic elements recorded in this zone is shown inFigs. 11 and 14.

Remarks: This zone is defined by the extinction of theGlobigerinoides primordius and the common occurrence ofCatpsydrax dissimilis. The most characteristic feature of this zoneis the frequent occurrence and diversity of the genus Globigerino-ides (Fig. 14).

Correlation: This zone is correlated well with Globoquadrinadehiscens Zone (N5) of Blow (1969). It is also equivalent toGlobigerinoides primordius Zone (M1a) of Berggren et al. (1995).

It is equivalent to the lower part of Globigerinoides trilobus Zone ofPostuma (1971); and the lower part of Globigerinoides altiaperturusZone of El-Heiny and Martini (1981) and Phillip et al. (1997). It is cor-related with Catpsydrax dissimilis Zone (M2) of Berggren et al. (1995)and Hewaidy et al. (2013) in the Gulf of Suez region (Fig. 15).

5.2.4. Globigerinoides bisphericus Partial Range Zone (M4b)Definition: This zone was originally defined as the interval of

the partial range of the nominate taxon between the FO of Globoro-talia birnageae and FO of Praeorbulina sicana (Berggren et al., 1995).Globorotalia birnageae is not recorded in the present study, andthus the zone was defined as the partial range of the nominate

cale is expressed as number of specimens per mm2. LO = Last occurrence. FO = First

Fig. 6. Distribution chart of the calcareous nannofossil species recorded in Wadi Wasit section.

Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400 389

Fig. 7. Distribution chart of the calcareous nannofossil species recorded in Wadi Nukhul section.

390 Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400

Fig. 8. Distribution chart of the calcareous nannofossil species recorded in Gabal Sarbut El-Gamal section.

Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400 391

Fig. 9. Distribution chart of the calcareous nannofossil species recorded in Wadi Sudr section.

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taxon below the FO of Praeorbulina sicana. (M4a) Zone was notrecorded in the present study.

Authors: Blow (1969, 1979).Age: Early Miocene (late Burdigalian).Stratigraphic position: It is recorded in the upper part of the

Hawara Member of the Rudeis Formation at Gabal Sarbut El-Gamaland in the lower part of Asl Member at Wadi Sudr. It attains 20 mthick at Gabal Sarbut El-Gamal and 45 m thick at Wadi Sudr(Fig. 13 and 14).

Remarks: In the present study, Globorotalia birnageae is absent,so it is difficult to define the M4a/M4b boundary. The zone is char-acterized by the presence of Globigerinoides bisphericus below theFO of Praeorbulina sicana.

Correlation: This zone is correlated with Globigerinatella insueta(N7) Zone of Blow (1969). It is also equivalent to (M4b) Zone ofBerggren et al. (1995) and equivalent to the upper part of Globigeri-noides trilobus Zone of Postuma (1971). It is correlated well withGlobigerinoides trilobus (N7) Zone of Abul-Nasr et al. (2009) and(M4) Zone of Hewaidy et al. (2013) in the Gulf of Suez region(Fig. 15).

5.2.5. Praeorbulina sicana-Orbulina suturalis Zone (M5)Definition: This zone is distinguished by a biostratigraphic

interval between the FO of Praeorbulina sicana and the FO of Orbu-lina suturalis.

Authors: Blow (1969, 1979).Age: Middle Miocene (Langhian).Stratigraphic position: It is recorded in the upper part of the

Asl Member of the Rudeis Formation at Gabal Sarbut El-Gamal sec-tion. It attains a thickness of about 60 m at Gabal Sarbut El-Gamal

section and it is marked by high diversity with moderately pre-served planktonic foraminiferal assemblage (Fig. 13).

Remarks: The evolutionary transition from Praeorbulina toOrbulina occurs within this zone (Berggren et al., 1995) (Fig. 13).The zones M6 and M7 are not recorded in the present study.

Correlation: This zone is correlated well with Globigerinoides sic-anus Zone (N8) of Blow (1969) and Praeorbulina sicana Zone (M5) ofBerggren et al. (1995). It may be equivalent to the lower part ofOrbulina suturalis Zone of Jenkins, 1985. It is correlated withPraeorbulina glomerosa Zone (N8) of Abul-Nasr et al. (2009) andZone (M5) of Hewaidy et al. (2013) in the Gulf of Suez region(Fig. 15).

5.2.6. Globorotalia fohsi Zone (M8)Definition: This zone is represented by a biostratigraphic inter-

val between the initial evolutionary appearance of the nominatetaxon and the initial evolutionary appearance of Globorotalia fohsilobata.

Authors: Cushman and Stainforth (1945); emended by Bolli(1957).

Age: Middle Miocene (Serravallian).Stratigraphic position: It is recorded in the Hammam Faraun

Member of the Belayim Formation at Gabal Sarbut El-Gamal sec-tion. It attains a thickness of about 50 m at Gabal Sarbut El-Gamalsection (Fig. 13). The distribution of the most important planktonicelements recorded in this zone is illustrated on Fig. 13.

Remarks: It is marked by the FO of Globorotalia fohsi (Fig. 13).Correlation: This zone is correlated well with Globorotalia

praefohsi (N11) Zone of Blow (1969) and Globorotalia fohsi (M8)Zone of Berggren et al. (1995). It may be equivalent to the upperpart of Globorotalia mayeri Zone of Jenkins 1985. In the Gulf of Suez

Fig. 10. Nannofossils biozones used by different authors for the upper Oligocene (Chattian)–middle Miocene (Serravallian).

Fig. 11. Distribution chart of the planktonic foraminiferal species recorded in Wadi Wasit section.

Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400 393

Fig. 12. Distribution chart of the planktonic foraminiferal species recorded in Wadi Nukhul section.

394 Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400

region, this zone may be equivalent to the upper part of Orbulinasuturalis Zone (N9) of Abul-Nasr et al. (2009) (Fig. 15).

6. Biostratigraphical integration

The integration between the distinguished calcareous nanno-fossil and planktonic foraminiferal biozones in the upper Oligo-cene-middle Miocene succession exposed in west central Sinaiare discussed from older to younger:

6.1. Chattian Stage

The Chattian Stage corresponds to the planktonic foraminiferalGlobigerina ciperoensis Zone (P22) and the calcareous nannofossilSphenolithus ciperoensis Zone (NP25). It is represented by (19 mthick-) of the lower part of the Nukhul Formation at Wadi Wasit sec-tion (Fig. 16).

6.2. Chattian–Aquitanian boundary

Generally, the Chattian–Aquitanian boundary can be recog-nized within the top portion of the foraminiferal Zone P22 ofCushman and Stainforth (1945) and Berggren et al. (1995). This

boundary is in accordance with the upper portion of the calcare-ous nannofossil Zone NP25 of Martini (1971) and Perch-Nielsen(1985) (Fig. 2). According to Bukry (1973), it is cited within thecalcareous nannofossil Zone CP19 where top is defined by theLO of Sphenolithus ciperoensis (Fig. 2). Bolli and Saunders (1985)associated the Chattian–Aquitanian boundary with the top ofZone Globorotalia kugleri of Bolli (1957); at the FO of Globigerino-ides primordius. Hewaidy et al. (2012) suggested this boundary atthe marked change in the size, preservation and diversity of theforaminiferal fauna from Chattian to Aquitanian at the FO ofGlobigerinoides spp. In the present study, the Chattian–Aquitanianboundary seems to be present at the top of the planktonic fora-miniferal Zone P22, which is marked by noticeable change insize, preservation and diversity of the foraminiferal fauna associ-ated with the FO of Globigerinoides spp. This planktonic foraminif-eral criteria are corresponding to the top portion of thecalcareous nannofossil Zone NP25 at the LO of the main Oligo-cene taxa: Sphenolithus ciperoensis, Chiasmolithus altus, Zygrhabli-thus bijugatus nolfi, Reticulofenestra bisecta and Triquetrohabdulusmillowii and at the FO of Discoaster druggii. There is a discerniblehiatus separating between Chattian and Aquitanian, due toabsence of the calcareous nannofossil zone (NN1) and probablythe topmost part of (NP25) as well as basal part of Zone (NN2)(Fig. 16).

Fig. 13. Distribution chart of the planktonic foraminiferal species recorded in Gabal Sarbut El-Gamal section.

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Fig. 14. Distribution chart of the planktonic foraminiferal species recorded in Wadi Sudr section.

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6.3. Aquitanian Stage

The Aquitanian Stage is distinguished in the studied successionson the basis of the presence of the planktonic foraminiferal Globige-rinoides primordius Subzone (M1a). It is represented by the upperpart of the Nukhul Formation (65 m) thick at Wadi Nukhul section(Fig. 16).

6.4. Aquitanian–Burdigalian boundary

The Aquitanian–Burdigalian boundary has not been formallydefined. However, Berggren et al. (1995); cited this boundary atthe base of the planktonic foraminiferal Zone M2 at the extinctionlevel of Globorotalia kugleri (Fig. 2). Fornaciari and Rio (1996); drewthis boundary at the top portion of the calcareous nannofossil ZoneMNN1 at the FO of Helicosphaera carteri (Fig. 2). Gradstein et al.(2004) cited the Aquitanian–Burdigalian boundary at 20.43 Ma. Inthe present study, this boundary is defined by LO of Globigerinoidesprimordius within the lowermost part of the Rudeis Formation(Mheiherrat Member) at Wadi Wasit section (Fig. 11), and it seemsto be present within the calcareous nannofossil Zone NN2 withoutany marker event of calcareous nannofossil species (Fig. 6).

Helicosphaera ampliaperta is represented in Zone NN2, this meansthat the represented Zone NN2 in the studied succession is not com-plete and a small hiatus can be detected at the Aquitanian–Burdiga-lian boundary. There is a hiatus separating between Aquitanian andBurdigalian, due to absence of the planktonic foraminiferal Globoro-talia kugleri/Globoquadrina dehiscens Subzone (M1b) (Fig. 16).

6.5. Burdigalian Stage

The Burdigalian Stage is subdivided into two planktonic forami-niferal zones: Catpsydrax dissimilis Zone (M2) and Globigerinoidesbisphericus Zone (M4b) (M3 and M4a were not recorded in the pres-ent study), which coincide with the calcareous nannofossil Discoas-ter druggii Zone (NN2) and Helicosphaera ampliaperta Zone (NN4).

The early Burdigalian is represented by the Mheiherrat Member(20 m thick) of the Rudeis Formation at Wadi Wasit section. AtWadi Sudr, the early Burdigalian is represented by the Somar For-mation, which is barren of any microfossils, but it contains pectensand oysters e.g. Chlamys (Lyropecten) santamaria, Crassostreagryphoides, Cubitostrea frondosa and Hyotissa verleti of Burdigalianage (Imam, 1991; El-Hedeny, 2005).

The middle Burdigalian is represented by the Hawara Member(20 m thick.) of the Rudeis Formation at Gabal Sarbut El-Gamal

Fig. 15. Planktonic foraminiferal biozones used by different authors for the upper Oligocene (Chattian)–middle Miocene (Serravallian).

Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400 397

section. There is a hiatus separating between middle and late Burd-igalian, due to absence of the planktonic foraminiferal Globigerina-tella insueta/Catpsydrax dissimilis Zone (M3) and Catpsydraxdissimilis/Globorotalia birnageae Subzone (M4a) (Fig. 15).

The late Burdigalian is represented by the lower part of the AslMember (15 m thick) of the Rudeis Formation at Wadi Sudr section(Fig. 16).

6.6. Burdigalian–Langhian boundary

Bolli and Saunders (1985) suggested the Burdigalian–Langhianboundary at the base of Globorotalia fohsi peripheroronda; at theextinction level of Globigerinatella insueta. Blow (1969) suggestedthis boundary within the basal portion of the foraminiferal Glob-igerinoides sicanus-Globigerinatella insueta Zone N8. Berggren et al.(1995); used the FO of Praeorbulina sicana to define the Burdiga-lian–Langhian boundary. Perch-Nielsen (1985); recognized thisboundary within Helicosphaera ampliaperta Zone NN4 at theextinction level of Helicosphaera ampliaperta. In the Gulf of Suezarea; Sadek (2001) and Marzouk (2009); were defined thisboundary by the LO of Helicosphaera ampliaperta. Faris et al.(2009) recognized this boundary in the upper part of the RudeisFormation (Mreir Member) of Wadi Gharandal section at the baseof Orbulina suturalis Zone which lies within Helicosphaera amplia-perta Zone (NN4). In the present study, the Burdigalian–Langhianboundary is cited at level of the FO Praeorbulina sicana whichcoincides with the LO of Sphenolithus belemnos and the FO Sphen-

olithus heteromorphus (Fig. 10). It can be drawn at the base of theAsl Member of the Rudeis Formation at Gabal Sarbut El-Gamalsection (Fig. 8).

6.7. Langhian Stage

The Langhian Stage is represented by the planktonic foraminif-eral Zone (M5), which coincides with the calcareous nannofossilZone NN4.

The early Langhian is represented by the upper part of the AslMember (50 m thick) of the Rudeis Formation at Gabal Sarbut El-Gamal section.

The middle Langhian is represented by the Mreir Member (35 mthick.) of the Rudeis Formation at Gabal Sarbut El-Gamal section.

The late Langhian is represented by the Kareem (15 m thick) orSarbut El-Gamal (20 m thick) formations at Wadi Sudr and GabalSarbut El-Gamal sections, respectively. Kareem and Sarbut El-Gamal formations are found barren of fauna, and they are assignedto the Langhian age according to their stratigraphic position andcorrelation with other previous studies (e.g. Marzouk, 2009;Hewaidy et al., 2013).

6.8. Langhian–Serravallian boundary

The Langhian–Serravallian boundary is highly controversial inthe literature. Blow (1969); placed this boundary within Zone(N9), which coincides with Zone (M6) of Berggren et al. (1995).

Fig. 16. Biostratigraphic integration of the studied successions; showing their chronology.

398 Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400

Perch-Nielsen (1985) placed this boundary within the Discoasterexilis Zone (NN6) at the LO of Sphenolithus heteromorphus.Marzouk (2009); placed this boundary at level of the LO of Sphen-olithus heteromorphus which coincides with the calcareous nanno-fossil Sphenolithus heteromorphus Zone (NN5). In the studiedsuccessions, the Langhian–Serravallian boundary is placed at theFO of Globorotalia fohsi which coincides with the FO of Discoasterbraarudii. It appears at the base of the calcareous nannofossil ZoneNN6 of Perch-Nielsen (1985) (Fig. 10). This boundary lies withinthe Hammam Faraun Member of the Belayim Formation at GabalSarbut El-Gamal section (Fig. 8).

There is a hiatus separating the Langhian from the Serravallian,due to absence of the planktonic foraminiferal zones (M6 and M7)and the missing of (NN5) Zone (Fig. 16).

6.9. Serravallian Stage

The Serravallian Stage includes the planktonic foraminiferalGloborotalia fohsi Zone (M8) and the calcareous nannofossil Disco-aster exilis Zone (NN6). It is represented by the Hammam FaraunMember (55 m thick) of the Belayim Formation at Gabal SarbutEl-Gamal section.

7. Summary and conclusions

1. The integration of calcareous nannofossils and planktonicforaminifera was used to place the zonal boundaries inthe upper Oligocene–middle Miocene successions in the

Abdel Galil A. Hewaidy et al. / Journal of African Earth Sciences 100 (2014) 379–400 399

Nukhul–Sudr area, west central Sinai, Egypt. The identified spe-cies provide more accurate determinations and high resolutioncorrelations in the studied area.

2. The age of the Nukhul Formation is a controversial point in thestratigraphy of west central Sinai and the biostratigraphicanalysis of this study has confirmed its Chattian–Aquitanian age.

3. The Chattian Stage corresponds to the planktonic foraminiferalGlobigerina ciperoensis Zone (P22) and the calcareous nannofos-sil Sphenolithus ciperoensis Zone (NP25). The Chattian–Aquita-nian boundary seems to be present at the top of theplanktonic foraminiferal zone P22, which is marked by notice-able change in size, preservation and diversity of the foraminif-eral fauna from Chattian to Aquitanian at the FO ofGlobigerinoides spp. This boundary is corresponding to the toppart of the calcareous nannofossil Zone NP25 at the LO of mainOligocene taxa Sphenolithus ciperoensis, Chiasmolithus altus,Zygrhablithus bijugatus nolfi, Reticulofenestra bisecta and Trique-trohabdulus millowii and at the FO of Discoaster druggii. Thereis a discernible hiatus separating Chattian from Aquitanian,due to absence of the calcareous nannofossil Zone (NN1).

4. The Aquitanian Stage is determined in the studied successionson the basis of the presence of the planktonic foraminiferalGlobigerinoides primordius Zone M1a. The Aquitanian–Burdiga-lian boundary is defined by LO of Globigerinoides primordiuswithin the lowermost part of the Rudeis Formation(Mheiherrat Member) at Wadi Wasit section and it seems tobe present within the calcareous nannofossil Zone NN2 with-out any marker event of calcareous nannofossil species (Figs. 6and 11). Helicosphaera ampliaperta is represented well in ZoneNN2, this means that the identified Zone NN2 in the studiedsuccession is not complete and it is represented only by theupper portion of this calcareous nannofossil zone. There is ahiatus separating Aquitanian from Burdigalian, due toabsence of the upper part of the planktonic foraminiferal Zone(M1b).

5. The Burdigalian Stage is defined by two planktonic foraminif-eral zones M2, M4b and (M3 and M4a were not recorded inthe present study), which coincides with the calcareous nanno-fossil zones NN2 and NN4. The Burdigalian–Langhian boundaryis defined by the FO Praeorbulina sicana which coincides withthe LO of Sphenolithus belemnos and the FO Sphenolithus hetero-morphus at the base of the Asl Member of the Rudeis Formationat Gabal Sarbut El-Gamal section (Figs. 8 and 10).

6. The Langhian Stage is defined by the planktonic foraminiferalZone M5, which coincides with the calcareous nannofossil ZoneNN4. The Langhian–Serravallian boundary is recognized at theFO of Globorotalia fohsi which coincides with the FO of Discoas-ter braarudii that appears in the base of calcareous nannofossilZone NN6 (Perch-Nielsen, 1985). This boundary lies withinthe Hammam Faraun Member of the Belayim Formation atGabal Sarbut El-Gamal section (Fig. 8).

7. The Serravallian Stage includes the planktonic foraminiferalGloborotalia fohsi Zone (M8) and the calcareous nannofossil Dis-coaster exilis Zone (NN6).

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