Calcareous nannofossil bioevents at the Palaeocene / Eocene boundary in the Kharga Oasis , Western Desert of Egypt

Two upper Palaeocene – lower Eocene stratigraphic sequences at the Kharga Oasis (Umm El Ghanayim and Naqb Assiut sections) were studied biostratigraphically on the basis of their calcareous nannofossil content. The investigated interval includes the upper part of the Tarawan Formation, the Tarawan Chalk, and the Esna formations. A total number of sixty-seven different taxa have been identified. The lowest occurrence (LO) of Discoaster araneus was used to place the base of the NP9b Subzone (base of Eocene) at the Gabal Umm El Ghanayim section. The lowest occurrences (LOs) of Rhomboaster bitrifida, Discoaster araneus and D. anartios are used to define the NP9a/NP9b subzonal boundary at the Gabal Naqb Assiut section. In this section, the P/E boundary is marked by a minor lithologic hiatus as indicated by the absence of the basal part of the Dababiya Member. At the studied two sections, a major turnover in calcareous nannofossil assemblages across the P/E transition was documented. The abundance of warm water Ericsonia subpertusa, Fasculithus spp., Coccolithus eopelagicus, Discoaster spp., Rhomboaster bitrifida and Tribrachiatus bramlettei characterize the Palaeocene-Eocene transition and suggest global warming and the Palaeocene – Eocene Thermal Maximum (PETM). the west of the Nile Valley. The two sections at Kharga Oasis are the Naqb Assiut and Gabal Umm El Ghanayim sections were in­ vestigated (Fig. 1). The upper Palaeocene to lower Eocene sedimentary suc­ cession in the Kharga Oasis includes from the base to the top: the upper part of the Dakhla Shale, the Tarawan Chalk, the Esna Shale and the Thebes formations. The lithostratigraphic corre­ lation for the P/E rock units in different sections from the west­ ern and eastern Desert and the present study, are illustrated in Table 1. In the following paragraphs a brief description of the meas­ ured and sampled formations is given. 2.1. Tarawan Formation The Tarawan Formation was first termed by AWAD & GHO­ BRIAL (1965) to describe the limestone; chalky limestone and the marly limestone succession which overlie the Dakhla Shale and underlie the Esna Formation. This unit is about 11 m thick, and is represented by samples 1 to 8 in the Gabal Umm El Gha­ nayim section. 2.2. Esna Formation The term Esna Shale was first introduced by BEADNELL (1905), to describe the shale succession that overlies the Tarawan Forma­ tion and underlies the Thebes Formation at Gabal Oweina, Esna­ Idfu area, Upper Nile Valley. ABDEL­RAZIK (1972) separated this formation into two members, the El Hanadi Member at the base and the El Shaghab Member at the top. DUPUIS et al. (2003) classified the Esna Formation from the base to the top, into three units (Esna Unit 1, Esna Unit 2 and Esna Unit 3) (Table 1). Article history: Manuscript received April 06, 2017 Revised manuscript accepted September 19, 2017 Available online October 31, 2017


INTRODUCTION
The late Palaeocene to early Eocene interval is considered to be one of the warmest time periods (THOMAS, 1998) known as the Palaeocene -Eocene Thermal Maximum (PETM) (KENNETT & STOTT, 1991) during which numerous events occurred.The remarkable climate change during that time can be explained by the release of a massive amount of methane from gas hydrates (DICKENS et al., 1995;KATZ et al., 1999).
Major changes in the terrestrial and marine biota occurred at the PETM.This interval is marked by the mass extinction of benthic foraminifera, with a global decrease in their diversity, which ranges from 30 to 50% (KENNETT & STOTT, 1991), be ing known as the Benthic Foraminiferal Extinction Event (BFEE) (THOMAS & SHACKLETON, 1996).The time interval is cha racterized by the presence of shortranging taxa such as "mal formed discoasters" and "rhomboasters".The extreme environmen tal changes at the PETM caused those malformations of coccoliths (JIANG & WISE, 2006).The global Palaeocene/Eocene bound ary was defined at the Dababiya Quarry section, south of Luxor, in the Upper Nile Valley (DUPUIS et al., 2003).
The aims of the present study are to identify the calcareous nannofossil assemblages of the PETM interval, to assign the stu died sections to several nannofossil biozones and to provide some light on the palaeoecology for the late Palaeoceneearly Eocene interval based on the presence of the most abundant calcareous nannofossil taxa.

GEOLOGIC SETTING AND LITHOSTRATIGRAPHY
The Kharga Oasis is one of the depressions of the Western De sert, lying between latitudes 24 o and 26 o north, about 200 km to the west of the Nile Valley.The two sections at Kharga Oasis are the Naqb Assiut and Gabal Umm El Ghanayim sections were in vestigated (Fig. 1).
The upper Palaeocene to lower Eocene sedimentary suc cession in the Kharga Oasis includes from the base to the top: the upper part of the Dakhla Shale, the Tarawan Chalk, the Esna Shale and the Thebes formations.The lithostratigraphic corre lation for the P/E rock units in different sections from the west ern and eastern Desert and the present study, are illustrated in Table 1.
In the following paragraphs a brief description of the meas ured and sampled formations is given.

Tarawan Formation
The Tarawan Formation was first termed by AWAD & GHO BRIAL (1965) to describe the limestone; chalky limestone and the marly limestone succession which overlie the Dakhla Shale and underlie the Esna Formation.This unit is about 11 m thick, and is represented by samples 1 to 8 in the Gabal Umm El Gha nayim section.

Esna Formation
The term Esna Shale was first introduced by BEADNELL (1905), to describe the shale succession that overlies the Tarawan Forma tion and underlies the Thebes Formation at Gabal Oweina, Esna Idfu area, Upper Nile Valley.ABDELRAZIK (1972) separated this formation into two members, the El Hanadi Member at the base and the El Shaghab Member at the top.DUPUIS et al. (2003) classified the Esna Formation from the base to the top, into three units (Esna Unit 1, Esna Unit 2 and Esna Unit 3) (Table 1).SAID, 1990).AUBRY et al. (2007) subdivided the Esna Formation into four members, from the base to the top as follows, the El Hanadi, El Dababiya Quarry, El Mahmiya and Abu Had members.
In the present study, the Esna Formation was sampled and described.The total thickness is about 17.5 m at the Gabal Umm El Ghanayim section and about 10 m at the Naqb Assiut section.This rock unit represents the El-Hanadi, El Dababiya Quarry and the lower part of ElMahmiya Member (Figs. 2 and 3).These members will be discussed briefly below.

El Hanadi Member
The El Hanadi Member was originally introduced by ABDEL RAZIK (1972)   thick at the base (sample 9 to 11), and another shale of about 8 m thick (samples 12 to 26) at its top (Fig. 2).At the Naqb Assiut sec tion, the lower part of the El Hanadi Member is composed of about 6 m of shale deposits (samples 1 to 17) and varies gradu ally into massive marls of about 0.95 m thick (samples 18 and 19) in its upper part.

Dababiya Quarry Member
At the type locality, the El Dababiya Quarry Member consists of five characteristic beds (1-5) of about 3.68 m thickness: Bed no. 1 is an organic rich clay layer (~0.63 m thick); bed no. 2 is a phos phate brown shale (~0.50 m thick); and bed no. 3 is a creamy phosphatic shale (~0.84 m thick); bed no. 4 is a grey calcareous shale (~07.1 m thick) and bed no. 5 is a calcarenitic marly lime stone (~1.00 m thick) (AUBRY et al., 2007).
In the current study, the Dababiya Quarry Member is about 1.2 m thick at Gabal Umm El Ghanayim and 0.9 m thick at the Naqb Assiut section.This Member consists of three beds as de scribed from the base to the top: Bed 1 is an organic rich clay layer, which contains scattered coprolites at Gabal Umm El Ghanayim (sample 27, about 15 cm), but it is absent at the Naqb Assiut sec tion; Bed 2 is brown-coloured fish debris and coprolite-rich lami nated shale at Gabal Umm El Ghanayim (samples 28 to 35, about 90 cm).At the Naqb Assiut section it consists of massive phos phatic marls rich with collophane grains at the base, and 70 cm of marly limestone at the top (samples 20 and 21, about 20 cm).Bed 3 consists of marls at Gabal Umm ElGhanayim (sample 36, about 15 cm), while at the Naqb Assiut section (Fig. 3) it is mainly com posed of chalky limestone (samples 22 to 25, about 70 cm).

El Mahmiya Member
This Member was defined by AUBRY et al. (2007), to cover the Esna 2 Unit of DUPUIS et al. (2003) at the Village of El Dababiya (35 km south of Luxor).At the Gabal Umm El Ghanayim section, the El Mahmiya Member is essentially composed of about 6 m of shale (samples 37 to 48), while at the Naqb Assiut section, the El Mahmiya Member consists mainly of 2.25 m of calcareous shale (samples 26 to 30).

MATERIAL AND METHODS
A total number of 78 samples were collected for calcareous nan nofossils investigations, from which 48 belong to the Gabal Umm El Ghanayim section and 30 to Naqb Assiut.The samples have been closely collected from the upper Palaeocenelower Eocene interval in the study sections and reach about 5 cm near the P/E boundary.The calcareous nannofossil assemblages were observed using a polarized light microscope at a magnification of 1250X and their identification was based on the standard taxonomy of PERCHNIELSEN (1985).
Calcareous nannofossil abundances were determined by counting 200300 specimens/slide (BACKMAN & SHAKLE TON, 1983).Additionally, one random traverse of the slide was scanned for rarer species.The nannofossil relative abundance was considered as follows: A = abundant (>10 specimens/field of view), C = common (1-10 specimens/field of view), F = few (1 specimen/1-10 fields of view), R = rare (1 specimen/> 10 fields of view) VR= very rare (1 specimen/more than100 field of view).The species richness is given as the total number of species re corded in each sample.
Nannofossil preservation was classified as: G = good (little or no evidence of dissolution and/or overgrowth; specimens can be easily identified to species level) and M = moderate (speci mens exhibit some etching and/or overgrowth; most specimens are identifiable to the species level).Palaeotemperatures from calcareous nannofossil proxies were calculated using the Microsoft Excel program in accordance with the mentioned authors in the palaeoecologysection and our research data.

Calcareous Nannofossils Biostratigraphy
The present manuscript concerns the biostratigraphy of calcare ous nannofossils from the upper part of the Tarawan Chalk and Esna formations (upper Palaeocene -lower Eocene interval) at the Umm El Ghanayim and Naqb Assiut sections.
The calcareous nannofossil assemblages are rich (72 species) and very diverse (22 genera) throughout the studied interval (late Palaeocene to early Eocene), while the preservation varies from moderate to good.
The stratigraphic distribution charts of calcareous nannofos sil species are shown in Figs. 4 and 5. Some index calcareous nannofossil species are illustrated in Pls. 1 and 2.
Remarks on assemblages: The base of this zone is defined by the LO of D. mohleri whilst its top is defined by the LO of D. multiradiatus (ABU SHAMA et al., 2007;FARIS & ABU SHAMA, 2007a).The calcareous nannofossil assemblages are similar to those of the underlying NP6 Zone, with the additional presence of marker species D. mohleri (Fig. 4).2).
Occurrence: The NP9 Zone covers the topmost part of the Tarawan Formation (sample 8), as well as most of the Esna For mation (samples 9 to 38) at the Gabal Umm El Ghanayim section, and occupies the whole Esna Formation at the Gabal Naqb Assiut section (samples 1 to 30).
Remarks on assemblages: The calcareous nannofossil as semblages are highly diverse and abundant in the NP9 Zone and this agrees well with the statement of PERCHNIELSEN (1985) that the Palaeocene diversity reached a maximum value in the  The two subzones of AUBRY (1999) were identified in our study.The NP9a/NP9b is marked by the LO of Discoaster araneus at the Gabal Umm El Ghanayim section (Fig. 4) and the LOs of Rhomboaster bitrifida, Discoaster araneus and D. anartios can be used to delineate the base of NP9b at the Gabal Naqb Assiut section (Fig. 5).
The total range of D. mahmoudii characterizes the subzone NP9c (AUBRY & SALEM, 2012).In the Umm El Ghanayim sec tion, D. mahmoudii first appears in sample 37.The LO of R. spineus in sample 34, is restricted to NP9c.We can conclude that the Subzone NP9c is approximately represented by a short inter val (samples 3438) in this section.In the Naqb Assiut section, the LOs of D. araneus, D. anartios and R. bitrifida (markers of NP9b) occur in sample 20.Nevertheless, D. mahmoudii appears only in sample 27 and the base of the NP9c can also be tentatively placed at this sample.(Table 2).
Occurrence: At the Gabal Umm El Ghanayim section, T. bramlettei has rare occurrences and the top of the zone cannot be defined due to the complete absence of Tribrachiatus contortus.
Remarks on assemblages: A new species, Tribrachiatus digitalis, was described from the DSDP Site 550, and used to sub divide the NP10 Zone into four subzones (AUBRY, 1996).The LO of T. bramlettei defines the base of the NP10a Subzone, the LO of T. digitalis defines the base of the NP10b Subzone, the HO of T. digitalis defines the base of the NP10c Subzone, and the LO of T. contortus defines the base of the NP10d Subzone.The base of the NP11 Zone (= top of NP10d Subzone) is defined by the HO of T. contortus.AUBRY et al. (1999) also used this subdivision in their de scription of the Esna Shale of Egypt (Gebel Qreiya, Gebel Kila biya).DUPUIS et al. (2003) used the same four nannofossil sub zones for dividing the NP10 of MARTINI (1971) at the Dababiya section.
Only the subzones NP10a and NP10b have been identified at the Gabal Umm El Ghanayim section.In the Umm El Ghanayim section, the NP10a Subzone includes the interval from sample 39 to 40.The interval from samples 41 to 48 can be assigned to the NP10b Subzone, based on the observed first rare occurrence of T. digitalis.

Palaeocene/Eocene (P/E) boundary
The onset of the carbon isotopic excursion (CIE) associated with the Palaeocene/Eocene Thermal Maximum (PETM) is considered as a best criterion for defining the P/E boundary in marine and nonmarine sequences worldwide.At the Dababiya section (the Global Standard Stratotype sec tion and Point -GSSP) the base of the lower Eocene beds (73 cm thick) is carbonate free and barren of calcareous nannofossils, and the taxa Discoaster araneus, Discoaster anartios, Rhomboaster spineus, and Rhomboaster spp.were recorded directly above this barren interval (DUPUIS et al., 2003).
El DAWY et al. (2016) studied the planktonic foraminifera at the Naqb Assiut section.They observed an irregular uncon formity surface associated with pebbles and bioturbated sand at the Palaeocene/Eocene boundary interval, and they suggested the existence of a minor hiatus at this boundary.In the present study, this small hiatus cannot be detected by means of nannofossils.
At the Wadi Nukhul section, West Central Sinai, KHOZYEM et al. ( 2013), suggest that the lowermost Eocene sediments are absent.The presence of a short hiatus at the P/E boundary is also observed in other sections from Egypt (Gabal Duwi and G. Aweina sections; SPEIJER et al., 2000).The presence of a hiatus at the P/E boundary was recorded at the W. Nukhul, Wadi Matu lla, and G. Mekattub sections (West Central Sinai) (FARIS et al., 2015b).
At the Gabal Umm El Ghanayim section, the LO of Discoaster araneus was used to delineate the base of Subzone NP9b, while the LOs of Rhomboaster bitrifida, Discoaster araneus and D. anartios can be used for approximation of the NP9a/NP9b subzonal boundary (early Eocene) at Gabal Naqb Assiut section.

Calcareous nannofossil bioevents
Fasciculithus alanii occurs below the P/E boundary, and is re stricted to the NP9a subzone (DUPUIS et al., 2003).The HO of this species has also been reported in several areas in Egypt such as Gabal Aweina, Gabal Duwi, Gabal Abu Had (AUBRY, 1998;VON SALIS et al., 1998;AUBRY & SALEM, 2013) and at Wadi Nukhul in West Central Sinai (KHOZYEM et al., 2013).The HO of F. alanii at the Markha section (WC Sinai), can be used to ap proximate the P/E boundary (FARIS & FAROUK, 2015).In the present study, the HO of Fasciculithus alanii was recorded at the base of the NP9b Subzone (sample 27) at the Gabal Umm El Gha nayim section.
The first occurrence of Discoaster mahmoudii is noticed in the uppermost part of the NP9b Subzone in the investigated sec tions (Figs. 4,5), and has its last appearance (HO in sample 39) in the lower part of the NP10a Subzone at the Gabal Umm El Ghanayim section.
The lowest occurrence of Campylosphaera eodela is within the NP9a Subzone (late Palaeocene) at the Gabal Umm El Gha nayim section, indicating that this species cannot be used as a reliable marker for subdividing the CP8 (=NP9) of OKADA & BUKRY (1980) into CP8a and CP8b (=NP9a and NP9b).The cal careous nannofossil bioevents, recorded by different authors in many sections in Egypt, are summarized in Tables 3 and 4.
In the present study, the Rhomboaster-Discoaster taxa did not occur simultaneously, having very rare relative abundances (Figs. 4,5).The first appearance of D. araneus is at the base of NP9b at the Um El Ghanayim section.Other taxa occurred in sequential order: D. anartios, R. bitrifida, R. cuspis and R. spineus.At the Gabal Naqb Assiut section, D. araneus, D. anartios and R. bitrifida cooccurred at the base of the NP9b Subzone, and R. cuspis appeared later at a higher level within NP9b.

Diversity
The diversity of calcareous nannofossils is the number of species in each sample.It reaches its maximum in the late Palaeocene (PERCHNIELSEN, 1985;FARIS & SALEM, 2007).The cal careous nannofossil diversity reaches a maximum of 26 species in the NP9a Subzone (sample no.17), with 21 species in NP9b at G. Umm El Ghanayim section.Above this subzone, fluctuations in species diversity occur, with variations from 24 to 7 species in the NP10 Zone with a generally decreasing trend.
At the Naqb Assiut section, the number of species fluctuates within NP9a from 5 to a maximum of 23 species (sample no 6), and reaches about 16 species in the upper part of late Palaeocene, while above that level the diversity fluctuates from 7 to 18 spe cies in the NP9b Subzone (early Eocene).
Coccolithus pelagicus is a dominant species of the high lati tudes from the Neogene to the present, based on palaeobiogeo graphic studies (MCINTYRE & BE, 1967, HAQ & LOHMANN, 1976, HAQ, 1980).In addition, C. pelagicus s. ampl.prevails in lower latitudes during midPalaeocene to early Eocene, where C. eopelagicus is documented in the early Eocene (HAQ & LOHM ANN, 1976) as in this study as characterizing global warming and early Eocene climatic optimum.Nevertheless, Coccolithus pelagicus dominates in the low latitudes throughout late Palaeocene early Eocene time, indicating nutrient improvement (JIANG & WISE, 2006), which could also be the cause of our results too.Coccolithus pelagicus s. ampl.dominates in assemblages together with Ericsonia subpertusa in our sections too.An increase of the relative abundance of Coccolithus pelagicus and Ercisonia subpertusa (C.subpertusus) during the PETM in the studied two sec tions was observed.They are interpreted as indicators of warm waters and were presumably adapted to oligotrophic environment based on their close association with the excursion taxa (discoast ers, rhomboasters, tribrachiatus).It is evident that changes in the abundance of the calcareous nannofossil species can be inter preted as a response to palaeoecologic conditions such as palaeo temperature and nutrients.The acme of Ericsonia subpertusa (Coccolithus subpertusus) was recorded at the Dababyia section above the dissolution horizon with the LOs of D. anartios and Rhomboasters (base of NP9b) and coincides with the negative δ13C value of the CIE (DUPUIS et al., 2003), which proves the aforementioned Benthic Foraminiferal Extinction Event (BFEE).These authors correlated this acme with that recorded at the Equa torial Pacific Ocean Drilling Site 865 (KELLY et al. 1996) and concluded that the acme of E. subpertusa is a global Acme pos sibly as a response to global warming.E. subpertusa (C.subpertusus) is common in the lower part of PETM, then reaches its acme in the middle part of the PETM in the Matulla section (West Cen tral Sinai (ABU SHAMA et al., 2007) and coincides with the LO of Rhomboaster taxa.In the studied two sections, the relative abundance of E. subpertusa varies from frequent to common in dicating warming conditions and eutrophication that occurred around the Palaeocene/Eocene boundary.The lower abundances of early Eocene oligotrophic, warm water Rhomboaster species are possible consequences of the aforementioned nutrientricher water condition.This is also evident from the domination of eu trophic, warm water C. eopelagicus detected in the early Eocene at the Um El Ghanayim section.Today, large forms of C. pelagicus can be observed at lower latitudes and upwelling regions (ZIVERI et al., 2004, BAUMANN et al., 2000).
In the studied sections, semiquantitative analyses of calcar eous nannofossil assemblages were performed for the interval from NP78 to the basal part of the NP10 Zone.At the Um EL Ghanayim section, the number of warm water nannofossil taxa fluctuates between 6-17 species in the late Palaeocene (NP7-8     Zone to NP9a Subzone) and reaches a maximum in a single sam ple of 12 species in the NP9b of the early Eocene, while the cold water taxa gradually decreases around this boundary (  5 and 6.The vertical variations in the number of warm water and cold water species in these two sections are shown in Fig. 6.On the other hand, the total warm and cold water specimens/slide and warm/cold water specimens are shown in Fig. 7. The last abundant appearance of Coccolithus subpertusus, and the frequent occurrence of excursion taxa including Discoaster araneus, D. anartios with rare Rhomboaster spp.across the PETM in four outcrops in Central Egypt are present in re sponse to the beginning of the warming period (YOUSSEF, 2016).

CONCLUSIONS
Two upper Palaeocene -lower Eocene stratigraphic sequences at Kharga Oasis (the Umm El Ghanayim and Naqb Assiut sections) were studied biostratigraphically for their calcareous nannofossil content.The investigated interval comprises the upper part of the Tarawan and the Esna formations.The Esna Shale can be divided from the base to top as follows: the El Hanadi, the Dababiya Quarry and El Mahmiya members.
At the Umm El Ghanayim section, the Dababiya Quarry Member consists of three beds: an organic richclay layer (15 cm), brown-coloured fish debris and coprolite-rich laminated shale (90 cm) and marls (15 cm).At the Naqb Assiut section, the Dababiya Quarry Member is composed of 20 cm of massive phosphatic marls rich with collophane grains at the base and 70 cm of marly limestone at the top.At the Naqb Assiut section, the P/E bound ary interval is marked by the absence of the organic richclay layer (Bed no.1) of the Dababiya Quarry Member at the Dababiya section (GSSP) which may indicate the presence of a minor hia tus at the base of the Eocene.This minor unconformity could not be detected palaeontologically by means of nannofossils.
At the Gabal Umm El Ghanayim section, the exposed part of the Tarawan Chalk encompasses nannofossil zones NP6, NP7/8 and the basal part of the NP9a Subzone.The El Hanadi Member includes the middle and upper parts of the NP9a Sub zone, and this means that a conformable relationship exists be tween these two units.In this section, the Dababiya Quarry Mem ber includes the NP9b Subzone (early Eocene) and the El Mahmiya Member includes the upper NP9b, the NP10aand NP10b Subzones.
The base of the NP9b Subzone is delineated by the LO of Discoaster araneus at the G. Umm El Ghanayim section, while at the Gabal Naqb Assiut section, the first appearances of the nannofos sil taxa Rhomboaster bitrifida, Discoaster araneus and D. anartios can be used to place the NP9a/NP9b subzonal boundary.
The current study indicates that the Umm El Ghanayim sec tion appears to be stratigraphically complete, at least based on nannofossil biostratigraphic resolution, and spans a late Palae ocene -early Eocene time interval encompassing zones NP9 to the base of NP10.The Palaeocene-Eocene boundary is placed at the base of the Dababiya Quarry Member of the Esna Fomation.
On the other hand, the species richness (diversity) fluctuates with a detected minimum around the Palaeocene/Eocene boun dary and Fasciculithus spp.decreases in diversity and abundance above the Palaeocene/Eocene boundary in the studied sections which is in agreement with other aforementioned research in the region and globally.

Figure 1 .
Figure 1.Geological map of the Kharga area (Western Desert, Egypt) with the location of the studied sections (modified after SAID, 1990).
to describe the lower part of the Esna Formation (5 m of shale succession) which overlies the Tarawan Formation and underlies the El Shaghab Member at Gabal El Shaghab, east of El Hanadi Village, near Esna City.According to AUBRY et al. (2007), the El Hanadi Member equates to the Esna Unit 1 of DU PUIS et al. (2003).At the Gabal Umm El Ghanayim section, the El Hanadi Member is composed of a calcareous shale about 1 m

Figure 2 .
Figure 2. Lithostratigraphy and biostratigraphy of Umm El Ghanayim section (Kharga Oasis, Western Desert, Egypt), samples position and correlation to the standard zonation of MARTINI (1971).

Table 2 .
Late Palaeocene to Early Eocene biozones and bioevents, according to the standard biozonations of MARTINI, 1971 (NP), OKADA & BUKRY, 1980 (CN), AG-NINI et al., 2014 (CNP to CNE) and the zonal scheme of the present study.NP9 Zone.The identification of NP9 is mainly based on the prese nce of D. multiradiatus.The marker species D. multiradiatus is continuously present from sample 8 upwards in G. Umm El Ghanayim and appears in all samples in the Nabq Assiut section.The genus Fasciculithus suffered decreasing diversity at the onset of the P/E boundary, and disappeared completely shortly above the base of the NP10 Zone.AUBRY (1999) divided the NP9 Zone into two subzones (NP9a and NP9b) based on the lowest appearance of Rhomboaster spp.and/or Discoaster araneus.

Figure 6 .
Figure 6.Vertical variations in the number of warm water and cold water species in Umm El Ghanayim and Naqb Assiut sections.

Figure 7 .
Figure 7.Total warm and cold water specimens/slide and warm/cold water specimens in Umm El Ghanayim and Naqb Assiut sections.

Table 1 .
Lithostratigraphic correlation for the P/E transition interval, between different works from the western and eastern Desert and the present study.

Table 3 .
Calcareous nannofossil bioevents at the Palaeocene/Eocene boundary recorded by different authors in the Eastern and Western Desert and Nile Valley.

Table 4 .
Calcareous nannofossil bioevents at the Palaeocene/Eocene boundary recorded by different authors in Sinai.

Table 5 .
Calcareous nannofossils from Umm El Ghanayim section, grouped according to their paleoecological behaviour into warm water, cold water and non-characteristic species.

Table 5 . continued Table 6 .
Calcareous nannofossils from Naqb Assiut section, grouped according to their paleoecological behaviour into warm water, cold water and non-characteristic species

Table 5 )
. At the Naqb Assiut section, the warm water species range from 7 to 15 in number below the P/E boundary and decreases to 3 near this boundary.Nevertheless, warmwater Coccolithus eopelagicus, Discoaster multiradiatus, D. araneus, Ericsonia subpertrusa, Sphenolithus primus, Zygrhablithus bijugatus in conjunc tion to cold water Neochiastozygus junctus are the most common species of the late Palaeocene -early Eocene interval in the two studied sections.This suggests the Palaeocene-Eocene Thermal Maximum (PETM) with the pick in the samples 21 and 33 of the Naqb Assiut and Umm El Ghanayim sections respectively dur ing this time interval(Figs.6,7).The warm, cold water and noncharacteristic calcareous nan nofossils near the P/E boundary at the Umm El Ghanayim and Naqb Assiut sections are shown in Tables