Integrated biostratigraphy of two Upper Maastrichtian – Palaeocene successions in north-central Sinai , Egypt

Integration of the calcareous nannofossil and planktonic foraminiferal biostratigraphies has been performed for the Upper Maastrichtian – Palaeocene successions at Gebel Umm Khushayb and west El-Hassana sections (north-central Sinai, Egypt). The studied successions include the uppermost part of the Sudr, Dakhla, and Tarawan formations and their lateral coeval Beida Formation. Biostratigraphic analysis has allowed recognition from Zone CF2 to Zone P4 in terms of planktonic foraminifera and from Zone CC26c to Zone NP7/8 in terms of calcareous nannofossils. The Maastrichtian/Palaeogene (K/Pg) boundary is characterized by an erosional surface that marks a hiatus between the Sudr/Dakhla or Sudr/Beida formation boundaries, as confi rmed by the absence of the planktonic foraminiferal CF1 to P1a zones and their equivalent nannofossil zones (top part of CC26c to lowest part of Zone NP3). The Danian/ Selandian (Da/Se) boundary lies in the upper part of the Dakhla Formation within the top of nannofossil Zone NP4, and within planktonic foraminiferal Zone P3b, similar to that of the Global Standard Stratotype-section and Point (GSSP) of the D/S boundary which has recently been chosen at the Zumaia section, northern Spain. A minor hiatus was observed across the Selandian/Thanetian boundary as indicated by a lithological change and a very condensed Zone NP6, corresponding to the Dakhla and Tarawan formation boundary in the west El-Hassana section.


GEOLOGICAL SETTING AND LITHOSTRATIGRAPHY
Tectonically, SAID (1962) divided Egypt into two major provinces, the deformed Unstable Shelf to the north, and the nearly horizontal and less deformed Stable Shelf to the south (Fig. 1).The Syrian Arc Fold Belt is one of the best-known structural features in the Unstable Shelf, and it played an important role in controlling the confi guration of the depositional sequences and the great complexity of changes both in facies and thickness (FAROUK & FARIS, 2008).The study area lies in north-central Sinai of the Unstable Shelf and is characterized by complex uplifts and domal anticlines of the Syrian Arc Fold Belt, that were formed during the closure of Neo-Tethys during the convergence of the African-Arabian Craton (STAMPFLI et al., 1995).
Maastrichtian -Palaeocene siliciclastic/carbonate outcrops are widely distributed in north-central Sinai, where the Campanian-Maastrichtian Sudr Formation overlies unconformably the Palaeocene sediments, which correspond to four well-defi ned formations from oldest to youngest are; Dakhla Formation, Tarawan Formation and lowermost part of the Esna Formation and their lateral coeval Beida Formation.The following is a detailed lithostratigraphic description of the detected Upper Maastrichtian -Palaeocene formations in the study area, given from older to younger (Fig, 2).

Sudr Formation-Campanian-Maastrichtian
The Campanian-Maastrichtian Sudr Formation (GHORAB, 1961) is widespread throughout the foot slopes of Sinai.It unconformably overlies the Dakhla or Bedia formations with a sharp lithological contact.The Sudr Formation is subdivided from base to top into the Markha and Abu Zenima members.The study measured part of the Sudr Formation deals only with the uppermost part of Abu Zenima Member (Upper Maastrichtian).It consists of argillaceous li me stone with a measured thickness of about 2-2.5 m in the study sections (Fig. 2).

Dakhla Formation-Danian-Selandian
The term Dakhla Formation was fi rstly used by SAID (1961) to describe the Maastrichtian-Palaeocene siliciclastics and carbonate deposits in Dakhla Oasis, Western Desert.In northern latitudes 26º30' in Egypt, the lower part of the Dakhla Formation is generally laterally equivalent to carbonate facies (the Sudr and Khoman formations).
Therefore in the Sinai Peninsula, the Dakhla Formation belongs to the Palaeocene and it overlies unconformably the tion of the global stratotypes of the Danian/Selandian and Selandian/Thanetian boundaries).In the two study sections, the K/Pg, De/Se and Se/Th remain unclear and not been precisely identifi ed.
However, many discrepancies in the Palaeocene bioevents could not be clarifi ed because either taxonomically different concepts caused uncertainties in correlation of the Palaeocene zones, especially in the southern Tethyan realm, (ORUE-ETXEBARRIA et al., 2007;ARENILAS, 2012), or these marker bio-events are recorded from different palaeolatitudes showing considerable variations in age (FAROUK & FARIS, 2011).
The main purpose of this research was to accurately correlate the Palaeocene bio-events with the standard biostratigraphic scales, using both calcareous nannofossils and planktonic foraminifera, for two Upper Maastrichtian -Palaeocene successions in north-central Sinai, and to discuss in details the Cretaceous/Palaeogene (K/Pg), the Danian/Selandian (Da/Se) and the Selandian/Thanetian (Se/Th) boundaries in the studied successions.
Calcareous nannofossils were analyzed using standard smear slides, which were examined using a light photomicroscope at 1250X magnifi cation.A qualitative estimation of the abundance of calcareous nannofossil taxa are noted as follows: A= abundant (more than 5 specimens /fi eld of view, fov), C=common (1-5 specimens/fov), F=frequent (one Maastrichtian Sudr Formation and also underlies the Tarawan Formation, with very clear contact, and can be easily recognized in the fi eld.It consists mainly of moderately hard, greenish grey monotonous pelagic calcareous mudstone with fl ooded well-diversifi ed calcareous planktonic assemblages with thicknesses ranging from 20 to 25 m in the west El-Hassana section.

Tarawan Formation-Thanetian
The Tarawan Formation (AWAD & GHOBRIAL, 1965) is composed of hard to moderately hard, massive yellowish white argillaceous limestone, partly limonitic with a thickness of 2 to 4 m in the west El-Hassana section.The partly resistant, light-coloured limestone of this unit is clearly distinguished from the overlying and underlying dark-colored soft shales.In Egypt, the Dakhla Formation is overlain by the Tarawan Formation which includes, at its upper part, the socalled "Velascoensis Event" with notable changes in the patterns of sedimentation in late Palaeocene time.The event that produced those changes is believed to be primarily tectonic coupled with global sea-level fall (STROUGO, 1986).

Beida Formation-Palaeocene
The term Beida Formation was fi rstly used by ALLAM & KHALIL (1988) based upon predominant carbonate deposits at Wadi Beida, north of Gebel Arif El-Naqa.It is equivalent to the Palaeocene siliciclastic/carbonate of the Esna Formation, which is recorded in different parts of Egypt.
In the study area, the Beida Formation has a wide distribution in the submerged palaeo-high areas around central Sinai, extending from Gebel Umm Khushayb to Ras Sudr.It unconformably overlies and underlies the Sudr and Thebes formations, respectively.The Beida Formation attains a total thickness of 40 m and is composed of greenish gray marl, argillaceous limestone, and well-bedded chalky limestone with chert bands in the Gebel Gebel Umm Khushayb section.

BIOSTRATIGRAPHY
The biostratigraphy is evaluated here based on the Cretaceous Foraminiferal (CF) Zonal Scheme of LI & KELLER (1998) and on the Palaeocene (P) Zonal Scheme of BERG- GERN & PEARSON (2005).These zonal schemes are applied in the present study to provide a much improved biostratigraphic framework.
For the calcareous nannofossil zonation, the Cretaceous Zonal Scheme of SISSINGH (1977) and the Palaeogene Zonal Scheme of MARTINI (NP, 1971) and VAROL (NTp, 1989) have been applied.The distribution of the calcareous nannofossils and planktonic foraminifera in the two studied sections are shown in Tables 1-4.The most important foraminifera and calcareous nannofossil taxa are fi gured in three plates (1)(2)(3).Abbreviations used FO= First Occurrence, LO= Last Occurrence; FCO= First Common Occurrence; FRO= First Rare Occurrence.The following is the description of the established calcareous nannofossil and planktonic foraminiferal biozones arranged from older to younger.Remarks: The Micula prinsii Subzone was informally defi ned by PERCH-NIELSEN (1979) and corresponds to the upper part of Zone CC26 of SISSINGH (1977).This subzone is a correlative of the latest Maastrichtian.However, its upper limit cannot be determined with accuracy in the two studied sections due to a large hiatus observed at the base of the Palaeocene.Micula murus is one of the rare Maastrichtian species and clearly restricted to low latitudes (WORSLEY AND MAR-TINI, 1970;THIERSTEIN, 1981;GARDIN, 2002;LEES, 2002).It was used for recognition of the uppermost Maastrictian (LAMOLDA & GOROSTIDI, 1992;POSPICAL, 1994;BERNAOLA & MONECHI, 2007 and many others).Remarks: The vanishing Cretaceous species are those extinct at the K/Pg boundary, and the Cretaceous persistent species are those calcareous nannofossil genera and species that are known to occur in the Cretaceous and survive into the Palaeocene (PERCH-NIELSEN, 1985b).The NP3 Zone is characterized by a decrease of Cretaceous vanishing species.In the two studied sections, Cretaceous persistent species are very rare in this zone and only a few specimens of Thoracosphaera operculata BRAMLETTE & MARTINI, Placozygus sigmoides (BRAMLETTE & SULLIVAN) and Cyclagelosphaera reinhardtii (PERCH-NIELSEN) dominate the assemblage.This zone has a reduced thickness in both the studied sections.Cruciplacolithus edwardsii RO-MEIN fi rst appears simultaneously with the FO of Ch. danicus (base NP3).

Calcareous nannofossils
The identifi ed Zone NP3 is equivalent to Zone NP3 of MARTINI (1971), the upper part of the Cruciplacolithus tenuis Zone of ROMEIN (1979)  Remarks: According to the Palaeocene zonation of VA-ROL (1989), the Zone NP4 in west El-Hassana and Umm Khushayb sections can be divided into three subzones, NTp6, NTp7 and NTp8.VAROL (1989) subdivided Zone NTp7 and NTp8 into several subzones.In the present study, it was so diffi cult to subdivide these two biozones into several subzones due to the extreme condensation of this interval.On the other hand, Zone NP4 could be divided into two subzones; NP4a, Ellipsolithus macellus-Sphenolithus primus Subzone, it is defi ned from the FO of E. macellus (BRAM-LETTE & SULLIVAN) to the FO of Sphenolithus primus PERCH-NIELSEN and NP4b, Sphenolithus primus -Fasciculithus tympaniformis defi nes from the FO of Sphenolithus primus to the FO of Fasciculithus tympaniformis (QUILLÉVÉRÉ et al., 2002 andFARIS et al., 2005).This subdivision was applied in the current study.
A small hiatus is suggested at the NP3/NP4 zonal boundary in the two studied sections, based on the absence of the uppermost part of Zone NP3 and the basal part of Zone NP4 (absence of Subzone NTp5B and NTp5C and most probably the lowermost of Zone NTp6 of VAROL, 1989).Also a minor hiatus is detected at the NP3/NP4 zonal boundary of the northern scarp of the Farafra Oasis (TAN-TAWY et al., 2003).The NTp6 Subzone is defi ned as the interval from the FO of Ellipsolithus macellus to the LO of Neochiastozygus imbriei HAQ & LOHMANN and N. eosaepes PERCH-NIELSEN.
In the study sections, E. macellus, shows a rare and sporadic presence throughout the study interval which may be a result of dissolution and /or the effect of diagenesis.
The subzone NTp7 defi nes the stratigraphic interval from the LOs of Neochiastozygus imbriei and N. eosaepes to the FCO (First Common Occurrence) of Sphenolithus primus.The FO of Chiasmolithus edentulus marks the base of Subzone NTp7B of VAROL (1989) and occurs within Zone NTp7 in the west El-Hassana and Umm Khushayb sections.According to VAROL (1989), the FO of this taxon can be used to directly correlate Tethys and the type area across the D/S boundary.The fi rst occurrence of Ch. edentulus in the study sections is easily correlated with the type area of the Danian/Selandian boundary.
The NTp8 has been defi ned to include the interval from the FO of Sphenolithus primus to the FO of Fasciculithus tympaniformis.Previous studies have indicated that the occurrences of Sphenolithus and Fasciculithus (Palaeocene taxa) are closely related.It is generally believed that the genus Sphenolithus appears just below the genus Fasciculithus (e.g.ROMEIN, 1979;BACKMAN, 1986;BERGGREN et al., 1995), although other authors observed a reverse setting in the relative stratigraphic position of the two biohorizons (VAROL, 1989;BERGGREN et al., 2000).
The onset of the fi rst radiation of Fasciculithus species occurs in samples 24 and 240 in the west El-Hassana and Umm Khushayb sections, respectively.The onset of the second radiation of Fasciculithus taxa occurs in samples 36 in the west El-Hassana section and in sample 242 in the Umm Khushayb section.Radiation of Fasciculithus (F.pileatus, F. bitectus, F. involutus, F. janii, and F. ulii) fi rst occurred in higher levels above the FO of S. primus in the study area.
As proposed by PERCH-NIELSEN (1985b) the FO of Neochiastozygus perfectus PERCH-NIELSEN was used for delineating the base of Zone NP5 in North Sea area.In the Zumaia section, the FO of this taxon occurs above the First Common Occurrence (FCO) of S. primus and immediately below the LCO of Braarudosphaera (DINARES-TURELL et al., 2007).In the two studied sections, N. perfectus fi rst appears within Zone NP4 (Zone NTp7).
The FO of N. perfectus in Zone NP4 in the study sections is considered to be earlier than reported in the North Sea area, and it is therefore apparently a diachronous event and must be used with caution for long distance corre lation.

Fasciculithus tympaniformis Zone (NP5)
Defi nition: The fi rst occurrence (FO) of Fasciculithus tympaniformis is used to defi ne the base of Zone NP5 and the FO of Heliolithus kleinpellii SULLIVAN defi nes its top.
Occurrence: This zone occupied the interval from the upper part of the Dakhla and Bedia formations, samples 245-249 (3 m thick) in the Umm Khushayb section, and samples 40-41 in the west El-Hassana section (1.5 m thick).
Characteristic species: The most characteristic species of this zone include those of Zone NP4 in addition to Fasciculithus tympaniformis.
In the study sections,Zone NP5 corresponds to NP5 Zone of MARTINI (1971)     Characteristic species: In addition to the fl oral assemblage, which characterizes Zone NP5, the following species are recorded in this zone: Heliolithus kleinpellii, Fasciculithus alanii PERCH-NIELSEN, Discoaster bramlettei MARTINI, and Bomolithus conicus (PERCH-NIELSEN).
Remarks: The FO of Heliolithus cantabriae PERCH-NIELSEN predates the FO of H. kleinpellii in the Umm Khushayb and west El-Hassana sections, and occurs at the top of Zone NP5, in agreement with the observations of PERCH-NIELSEN (1985b) andTANTAWY et al. (2003).In the Umm Khushayb section, Discoaster bramlettei occurs at the base of Zone NP6 and is considered here to be a reliable marker for the base of Zone NP6 in this section.Occurrence: This zone is only represented by the Tarawan Formation in the west El-Hassana section (samples 43-45, 1m thick).
Characteristic species: In addition to the identifi ed nannofossils that have been recorded in the Zone NP6; Discoaster mohleri, Fasciculithus schaubii HAY & MOHLER, and F. richardii PERCH-NIELSEN have their fi rst appearance in this zone.
Remarks: The zonal scheme of MARTINI (1971) cannot be applied to this interval because the marker species which defi nes the NP7/NP8 zonal boundary (Heliolithus riedelii BRAMLETTE & SULLIVAN) is absent in the west El-Hassana section.The Discoaster mohleri Zone of RO-MEIN (1979) is used here.In the Umm Khushayb section, the FO of Fasciculithus alanii PERCH-NIELSEN occurs at the base of Zone NP6, while this species fi rst appears at the base of Zone NP7/8 in the west El-Hassana section.
The recorded Zone NP7/8 is equivalent to the combined NP7 and NP8 Zones of MARTINI (1971)
Occurrence: This zone occupies the upper part of the Sudr Formation in the study area.It's true thickness is not defi ned because the base of the Sudr Formation is unexposed in the two studied sections.
Characteristic species.The most dominant planktonic species recorded in this zone yields a relative high abundance of biserial heterohelicids, while pseudoguembelinids, triserial and globotruncanid species are generally very rare (Tables 3 & 4).

Remarks:
The Micula prinsii Subzone coincides with part of the Pseudoguembelina palpebra and the whole Plummerita hantkeninoides zones (TANTAWY & KELLER, 2000;KELLER et al., 2007;FAROUK & FARIS, 2008).The absence of Plummerita hantkeninoides and Gansserina gansseri zones; in addition to the recognition of Micula prinsii confi rms the presence of the CF2 in the upper part of the Sudr Formation (Fig. 3).

Eoglobigerina edita Partial-range Zone
Defi nition: This zone is defi ned as the biostratigraphic interval between the LO of Parvularugoglobigerina eugubina (LUTERBACHER & PREMOLI SILVA) and the FO of Praemurica uncinata (BOLLI).

Occurrence:
The zone is recorded from the basal part of the Beida Formation and only from the Gebel Umm Khushayb section.It is represented by samples 222-224 (0.5 m thick).This subzone is missing in the west El-Hassana section due to the larger amplitude of the unconformity in this section.3 & 4).
Remarks: At the K/Pg boundary, several changes are observed in the planktonic foraminiferal assemblages, including the extinction of virtually all Cretaceous species (tropical-subtropical and cosmopolitan), and the fi rst appearance of the Danian species.The Cretaceous species present at the base of a transgression of lower Danian sediments are reworked, and are represented by small cosmopolitan surface water dwellers such as Heterohelix and Pseudoguembelina with very rare Rugoglobigerina and Globotruncana spp..
The FOs of Globanomalina compressa and/or Praemurica inconstans have been used to determine the base of Subzone P1c (OLSSON et al., 1999;BERGGREN & PEAR-SON, 2005).The authors believe that the FO of Glo ba no malina compressa predates that of the FO of Praemurica inconstans, and occurs within Zone P1b.A similar occurrence in Subzone P1b was also reported by KELLER (2002).According to BERGGREN & PEARSON (2005), Zone P1b falls between the top part of the Cruciplacolithus tenuis (NP2) Zone, and the basal part of the Chiasmolithus danicus (NP3) Zone.Therefore, the authors believe that the base of Zone P1b should be absent in the Gebel Umm Khushayb due to absences of the Cruciplacolithus tenuis Zone NP2.

Lowest-occurrence Subzone (P1c)
Defi nition: The biostratigraphic interval from the FO of Globanomalina compressa and/or Praemurica inconstans and the FO of Praemurica uncinata.
Occurrence: This zone is recorded from the lower part of the Dakhla Formation and represented only by samples 7-8 (2.0 m thick) from the west El-Hassana section and it encompasses, samples 224-230 (3.0 m thick) at the Gebel Umm Khushayb section.
Characteristic species.In this interval the species are highly abundant and well preserved.The assemblage of this interval is similar to that of the underlying Subzone P1c with the addition of four more species Praemurica inconstans, Globanomalina compressa and Parasubbotina varianta (SUBBOTINA), Morozovella trinidadensis (BOLLI).

Praemurica uncinata Lowest-Occurrence Zone (P2)
Defi nition: This is the Biostratigraphic interval between the FO of Praemurica uncinata to the FO of Morozovella angulata (WHITE).

Occurrence:
The zone encompasses the middle part of the Dakhla Formation at the west El-Hassana section and is represented by samples 9-29 (15 m thick).In the Gebel Umm Khushayb section it is recorded from the middle part of the Beida Formation and is represented by samples 229-236 (8 m thick).Remarks.Morozovella conicotruncata and M. pasionensis fi rst appeared within the lower part of this subzone, while M. velascoensis, M. occlusa, M. acuta, M. preaequa and Subbotina velascoensis fi rst occurred within the upper part of the subzone (Tables 3 & 4).

Globanomalina pseudomenardii Total Range Zone (P4)
Defi nition: This zone is defi ned as the interval of the total range of the nominated taxon.
Occurrence: The zone occupies about 5.5 m of the uppermost part of the measured Beida Formation at Gebel Umm Khushayb and is represented by samples 244-251.It also occurs in the topmost part of the Dakhla Formation, as well as the whole Tarawan Formation at the west El-Hassana section (samples 40-45).
Remarks.BERGGREN AND PEARSON (2005) subdivided the P4 Zone into three subzones; Globanomalina pseudomenardii/Parasubbotina variospira (P4a) concurrentrange Subzone; Acarinina subsphaerica (P4b) Partial-range Subzone and Acarinina soldadoensis/Globanomalina pseudomenardii (P4c) concurrent-range Subzone.In the current study, it was also diffi cult to subdivide the P4 into these biozones due to the poor preservation of foraminiferal tests as a result of carbonate dissolution.OLSSON et al. (1999) reported that the FO of Morozovella aequa occurs at the lower boundary of the P4c Zone.
In the present study, the FO of Morozovella aequa is recognized at the top part of P3b Zone, which is equivalent to the top part of the calcareous nannofossil NP4 Zone.A similar occurrence in the P3b Zone was also reported by ARENI-LAS (2012) in the Caravaca section of Spain.

The Cretaceous/Palaeogene (K/Pg) boundary
The K/Pg boundary is marked by an abrupt lithological change that corresponds to the boundary between the Sudr and Dakhla formations at the west El-Hassana section or to the Sudr / Beida formation at Umm Khushayb.Biostratigraphic analysis (planktonic foraminifera, calcareous nannofossils) confi rms that the studied sections are incomplete and discontinuous across the K/P boundary.A small hiatus is suggested by the absence of the Plummerita hantkeni-pressa, Parasubbotina pseudobulloides, Parasubbotina varian ta, Subbotina concellata (BLOW), S. trinagularis (WHI TE), S. triloculinoides, S. trivialis, Praemurica uncinata, P. inconstans and Morozovella praeangulata (BLOW) (Tables 3 & 4).
Remarks: Subbotina triangularis and S. concellata fi rst appear within the upper part of this biozone (Tables 3 & 4).STEURBAUT & SZTRÁKOS (2008), mentioned that the Praemurica uncinata Zone falls within the top part of the calcareous nannofossil Zone NTp6 in south-west France.In the present study, it falls within Zone NTp6 and the lower part of Zone NTp7.A similar occurrence was also reported by STEURBAUT et al. (2000) in the Kalaat Senan section, central Tunisia.
noides, Guembelitria cretacea, Parvularugoglobigerina eugubina Zones and Parasubbotina pseudobulloides Subzone.In the west El-Hassana section, the Subbotina triloculinoides Subzone is also missing.Moreover, the upper part of the calcareous nannofossil Micula prinsii Subzone and the earliest Danian Zones (NP1 and NP2) are missing.This hiatus may be linked to tectonic activity and irregular palaeotopography associated with low sedimentation rates as suggested by FA-ROUK & FARIS (2008).
The K/Pg boundary is characterized by the extinction of Cretaceous tropical planktonic foraminifera, and an abrupt change in species richness.However, most of the Cretaceous calcareous nannofossil vanishing species progressively decrease in abundance within Zone NP4; only the most dissolution-resistant Cretaceous species (Micula decussata, Watznaueria barnesae) are still present near the top of Zone NP4.The Cretaceous persistent species progressively increase in abundance above the K/Pg boundary.Cyclagelosphaera reinhardtii is the most common Cretaceous persistent species in the Palaeocene.

The Danian/Selandian boundary
The global stratotype section and point (GSSP) across the Danian/Selandian (Da/Se) boundary has been defi ned in the Zumaia section, northern Spain close to the FO of F. tympaniformis, just below the NP4/NP5 boundary and within the planktonic foraminiferal P3b Zone (BERNOALA et al., 2009).Based on calcareous nannofossils, the Danian/Selandian (Da/Se) boundary is delineated at a level close to the FO of Fasciculithus tympaniformis, just below the NP4/NP5 boundary and it coincides with the End Acme of Braarudosphaera bigelowii (BERNOALA et al., 2009).The Lowest Common Occurrence (LCO) of Braarudosphaera, which marked the lithological change at the D/S boundary at the type area in Denmark, can be directly correlated with the abrupt transition from the Danian limestones to the marly Itzurun Fm. at Zumaia (SCHMITZ et al., 1998;BERNAOLA et al., 2009).This event is not applicable to the Tethyan sections because Braarudosphaera was not recorded there (BER NAOLA et al., 2009).The Last Common Occurrence (LCO) of Braarudosphaera seems applicable for placing the base of the Selandian in Denmark, but it is an unreliable event for de lineating the Danian/Selandian boundary in the study sections.
Previously in Egypt, the Danian/Selandian was marked as a prominent organic-rich layer with a short-term sea-level fall coinciding with the P3a/P3b boundary, by using the lowest occurrence of the slightly keeled Igorina as a zonal boundary criterion (SPEIJER, 2003;OBAIDALLA et al., 2009;SPRONG et al., 2009).In the Qreiya section, the organicrich layer occurs approximately 1 m above the FOs of Chiasmolithus edentulus and small fasciculiths (SPRONG et al., 2009).This event bed at the D/S boundary, situated at the base of the Subzone NTp7B, and the equivalent planktonic foraminiferal P3a/P3b zonal boundary, is now considered latest Danian in age (BERNOALA et al., 2009;YOUSSEF, 2009).
On the other hand, FARIS & ABU SHAMA (2007) put the Danian/Selandian boundary at the base of Zone NP5.In the present study, it is bracketed within the Zone NTp8 (topmost NP4 equivalent to top part of the planktonic foraminifera P3b Subzone), at a level close to the First Occurrence (FO) of Morozovella velascoensis, M. occulsa, M. aquea and M. acuta (below) and the FO of Fasciculithus tympaniformis (above) just below the NP4/NP5 boundary in west El-Hassana and Umm Khushayb sections, is similar to that of the Global Standard Stratotype-section and Point (GSSP) of the Da/Se boundary which has recently been selected at the Zumaia section.
An important global nannofossil event is the onset of the second radiation of Fasciculithus (F.bitectus, F. involutus, F. janii, F. billii and F. ulii).It starts within Zone NTp8 (topmost NP4 and P3b) at a level close to the FO of F. tympaniformis and just below the NP4/NP5 boundary in the study sections.
The fi rst continuous occurrence (FCO) of Sphenolithus primus, the marker taxon for the base of Subzone NTp8A of VAROL (1989), is a reliable marker for delineating the Danian/Selandian transition (FARIS et al., 2005, QUILLE-VERE et al., 2002).In the present study, the FRO (First Rare Occurrence) of Sphenolithus primus is not a useful global marker because it occurs rarely and sporadically.STEUR- BAUT &SZTRÁKOS (2008) andBERNAOLA et al. (2009) also reported a similar occurrence for the FRO of Sphenolithus primus.

The Selandian/Thanetian boundary
The base of the Thanetian in its original type area, has been correlated within the upper part of the nannofossil Zone NP6 (AUBRY, 1994;KNOX, 1994).The base of Chron C26n at Zumaian, as a continuous, deep marine and cyclic sequence, offers the possibility of establishing a potential Thanetian Unit Stratotype (DINARÈS-TURELL et al., 2007).It is positioned 30.5 m above the base of the Itzrun Formation, very close to the base of Chron C26N (SCHMITZ et al., 1998).
A minor hiatus is proposed at the Selandian/Thanetian boundary as indicated by a condensed interval that marks a lithological change from the calcareous shales of the Dakhla Formation to the limestones of the Tarawan Formation.Therefore, the Selandian/Thanetian boundary in the present study is located at the top of Zone NP6 and within the lower part of the Globanomalina pseudomenardii Zone.No great changes in the nannofossil assemblages have been observed in the west El Hassana section, except for the FO of Discoaster mohleri.The Heliolithus kleinpellii Zone (NP6) is not recorded in several localities in Egypt (e.g. BASSIOUNI et al., 1991;FARIS et al., 1999;FARIS & ZAHRAN, 2002;AYYAD et al., 2003).

CONCLUSIONS
The results obtained can be summarized as follows: 1.An integrated calcareous nannofossil and planktonic foraminiferal biostratigraphy has been achieved for the

Figure 1 :
Figure 1: Location map of the study area.
The FO of Heliolithus kleinpellii defi nes the base of Zone NP6 and the FO of Discoaster mohleri BUKRY & PERCIVAL defi nes its top.Occurrence: Zone NP6 occupies the interval from the upper part of the Dakhla and Bedia formations and is represented by samples 250-251 (2.5 m thick) in the Umm Khushayb section and occurs only in sample 42 (0.4 m thick) in the west El-Hassana section.

Figure 3 :
Figure 3: Standard and alternative planktonic foraminiferal and calcareous nannofossil biozonations for the Palaeocene interval.
Defi nition: interval from the FO of the Morozovella angulata to the FO of Igorina albeari (CUSHMAN & BERMU-DEZ).
, the Fasciculithus tympaniformis Stratigraphic distribution of the identifi ed calcareous nannofossils in West El-Hassana section , NC Sinia, Egypt Table1 :

Table 3 :
Stratigraphic distribution of planktonic foraminiferal taxa identifi ed in the west El-Hassana section.

Table 4 :
Stratigraphic distribution of planktonic foraminiferal taxa identifi ed in the Gebel Umm Khushayb section.
m thick) in west El-Hassana, and sample 237-243 (7 m thick) from Gebel Umm Khushayb.Various authors have observed that Zone P3 is condensed in this area (e.g.SAMIR, 2002; AL-WOSABI & ABU SHAMA, 2007 in Egypt; Upper Maastrichtian-Palaeocene successions on the west El-Hassana and Umm Khushayb sections, northcentral Sinai.The Maastrichtian -Palaeocene material studied in this work consists of siliciclastic/carbonate deposits belonging to four formations: The Sudr, Dakhla, Tarawan formations, and their lateral coeval Beida Formation.2. 44 calcareous nannofossil and 31 planktonic foraminiferal taxa are identifi ed with moderate to good preservation and relatively high diversity.These microfossil assemblages allowed subdivision of the study sections into one subzone and fi ve calcareous nannofossil zones: Micula prinsii Subzone (CC26c), Chiasmolithus danicus Zone (NP3), Ellipsolithus macellus Zone (NP4), Fasciculithus tympaniformis Zone (NP5), Heliolithus kleinpellii Zone (NP6), Discoaster mohleri Zone (NP7/8); and fi ve planktonic foraminiferal zones and four subzones; Pseudoguembelina palpebra Zone (CF2), Eoglobigerina edita (P1) Zone, Praemurica uncinata Zone (P2), Morozovella angulata-Globanomalina pseudomenardii Zone (P3), Globanomalina pseudomenardii Zone (P4).Zone P1 can be subdivided into the Subbotina triloculinoides Subzone (P1b), and the Globanomalina compressa/Praemurica inconstans Subzone (P1c).Zone P3 is subdivided into the Morozovella angulata-Igorina albeari Subzone (P3a), and the Igorina albeari/Globanomalina pseudomenardii Subzone (P3b).3. Biostratographic analyses of the two studied sections based on planktonic foraminifera and calcareous nannofossils, indicate that deposition of the Latest Maastrichtian to Early Danian sediments was interrupted by erosion and or non-deposition related to tectonic activity.As a result, some planktonic foraminifera (Plummerita hantkeninoides, Guembelitria cretacea, Parvularugoglobigerina eugubina biozones and, Parasubbotina pseudobulloides Subzone and their equivalent calcareous nannofossils (top part of CC26c, NP1 and NP2 zones) are missing.4. The new-Palaeocene calcareous nannfossil taxa fi rst appear at the base of Zone NP3 of early Danian age.They progressively increase upwards and are more common than the Cretaceous vanishing species in Zone NP3 and NP4. 5.According to the Palaeocene Zonal Scheme of VAROL (1989); the nannofossil Zone NP4 of MARTINI (1971), can be divided into three subzones; NTp6, NTp7 and NTp8 in the west El-Hassana and Umm Khushayb sections.A small hiatus is observed at the NP3/NP4 zonal boundary as suggested by the absence of the NTp5B Subzone and NTp5C and most probably the lowermost part of Zone NTp6.6.The onset of a second diversifi cation of the genus Fasciculithus, represented by F. bitectus, F. involutus, F. janii, F. billii and F. ulii, begins within Zone NTp8 and just below the NP4/NP5 boundary in El Hassana and Umm Khushayb sections.This radiation marks the Danian/Selandian boundary.Based on planktonic fora mi-nifera, the Danian/Selandian boundary lies with the basal part of the P3b Subzone.7. The Selandian/Thanetian boundary is placed at the contact between the Dakhla and Tarawan formations at west El-Hassana, approximately at the top of calcareous nanofossil Zone NP6 within the equivalent planktonic foraminiferal Zone P4.A minor hiatus was observed at this boundary as indicated by the prominent lithological chan ge from the calcareous shale of the Dakhla Formation to the limestones of the Tarawan Formation and the very condensed calcareous nannofossil Zone NP6.