Calcareous nannofossils and paleoenvironments of the PaleoceneeEocene thermal maximum (PETM) interval in central Egypt
Journal of African Earth Sciences 114 (2016) 203e219 Contents lists available at ScienceDirect Journal of African Earth Sciences journal homepage: www.elsevier.com/locate/jafrearsci Calcareous nannofossils and paleoenvironments of the PaleoceneeEocene thermal maximum (PETM) interval in central Egypt Mohamed Youssef a, b, * a b Department of Geology and Geophysics, College of Science, King Saud University, Saudi Arabia Department of Geology, Faculty of Science, South Valley University, 83523 Qena, Egypt a r t i c l e i n f o a b s t r a c t Article history: Received September 2015 Received in revised form 19 November 2015 Accepted 23 November 2015 Available online December 2015 The PaleoceneeEocene Thermal Maximum (PETM) interval was examined from four outcrops in Central Egypt to document the response of the floral communities across the PETM The four outcrops are: Gebel Taramsa west of Qena, Gebel Duwi in the Red Sea Coast, and Gebel Qeryia, Gebel Arras sections in Wadi Qena The qualitative and quantitative analyses of calcareous nannofossils used samples on a high resolution scale The PETM is characterized by distinguished lithological succession, the Dababyia Quarry Beds (DQB) which extend over the Nile Valley, the Eastern Desert and the Western Desert The calcareous nannofossils changes across the Paleocene/Eocene boundary (NP9a/NP9b) is marked by the following events: 1) abrupt decreases in both diversity and abundance, 2) dramatic decrease of Fasciculithus both in diversity and abundance, 3) first acme of Coccolithus pelagicus/Coccolithus subpertusus, and 4) first occurrence of excursion taxa including Discoaster araneus, Discoaster anartios, Discoaster aegyptiacus and Rhomboaster spp) These events may refer to relatively warm and oligotrophic surface waters The abundance of Toweius spp in the upper part of the PETM which associated with Campylosphaera characterizes the return to normal conditions © 2015 Elsevier Ltd All rights reserved Keywords: Calcareous nannofossils Biostratigraphy Paleoenvironments PETM Central Egypt Introduction The Palaeocene/Eocene Thermal Maximum (PETM) was a cata€ hl et al., 2000) strophic climate event continued about 220 kyr (Ro at ~55.5 my ago The sea-surface temperature elevated by C in the tropics and as much as C at the high latitudes by this global warming (Zachos et al., 2003), whereas bottom water warmed by 4e5 C (Thomas et al., 2000) This event is one of the warmest intervals of the Cenozoic, which followed a warming trend that started in the Latest Danian Event (LDE) ~61.7 my (Bornemann et al., 2009), the Danian/Selandian transition event ~61.7 my (Speijer, 2003), and the Mid Paleocene Biotic Event (MPBE) ~58.2 my (Bernaola et al., 2007) The PETM characterized by interval of global warming and negative shift in carbon isotope (Raffi and Bernardi, 2008) The oceanic benthic and planktonic organisms as well as terrestrial mammals characterized by massive turnovers during the * Department of Geology, Faculty of Science, South Valley University, 83523 Qena, Egypt E-mail address: myousefgeology@gmail.com http://dx.doi.org/10.1016/j.jafrearsci.2015.11.021 1464-343X/© 2015 Elsevier Ltd All rights reserved abrupt climatic change associated with the PETM (Zachos et al., 2005) This event characterized by 30e50% of the deep sea benthic foraminiferal species have extinct (Tjalsma and Lohmann, 1983), radiation of land mammals and vegetation (Gingerich, 2003), diversification of planktonic foraminifers (Berggren and Ouda, 2003, 2013), and the so-called “excursion taxa” among planktonic foraminifera and calcareous nannofossils (Kahn and Aubry, 2004) The responses of benthic organisms to the PETM event appear to have been different (Bralower, 2002; Raffi et al., 2005; Gibbs et al., 2006a) Tethyan area is considered as a key area concerning of the PETM warming in particular the potential of producing warm saline waters that may have been the driving force for deep ocean warming (Kennett and Stott, 1991) Tethyan region used to understand the associated changes of flora and fauna (Tantawy, 2006) In early Paleogene, Egypt was situated at the southern margin of the Tethyan seaway, where sedimentation rates were high The Egyptian sections provide a detailed record of biologic and chemical changes through the PaleoceneeEocene transition The GSSP for the base of the Eocene Series is located above the base of Dababiya Quarry beds, at Dababiya section, Egypt (Dupuis et al., 204 M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 2003) The Paleocene/Eocene successions in central Egypt are marked by widely distributed sections rich in calcareous nannoplanktonic assemblages A number of studies carried out the PETM in Tethys region (e.g Lu et al., 1995; Molina et al., 1998; Monechi and Angori, 1998; Von Salis et al., 1998; Bolle et al., 1999; Kahn and Aubry, 2004; Aubry et al., 2007; Berggren et al., 2012; Stassen et al., 2012; Aubry and Salem, 2013; Farouk, 2015; Faris and Farouk, 2015) Previous studies mentioned a prominent organic-rich layer (The Dababiya Quarry beds) of Esna Formation situated at the calcareous nannofossils NP9a/NP9b zonal boundary Few of the previous studies have recorded the response of the calcareous nannofossils based on quantitative analysis The current study aims to 1) evaluate the impact of the PETM on the composition of low latitudinal calcareous nannofossils 2) evaluate diversity, absolute and relative abundance patterns of calcareous nannofossils in the PETM interval in order to understand the paleoenvironmental changes of the PETM interval on low latitudinal areas in Tethys (central Egypt) Lithostratigraphy The Late CretaceouseEarly Eocene sedimentary rocks in central and southern Egypt are characterized by gradual facies differentiation (Issawi, 1972) The study area in central Egypt is covered by sediments of Nile Valley facies The PaleoceneeEocene Thermal Maximum (PETM) interval in central Egypt is marked by complex beds of marly calcarenitic limestone and laminated phosphatic shale The PETM interval in Egypt extends within the lowest part of Esna Formation (Dupuis et al., 2003), they referred to this succession firstly as Dababiya Quarry beds (DQB) and now (Aubry et al., 2007) as Dababiya Quarry member (DQM) The Dababiya Quarry Member in the Global stratotype section (Dababiya section) is about 1.90 m thick and divided into beds In the studied area the all beds of Dababiya Quarry Member are not present (Fig 2) Measured sections The samples used in this study were collected from Gebel Taramsa, Nile Valley; Gebel Qreiya, Gebel Araas sections in Wadi Qena, and Gebel Duwi in the Red Sea Coast (Figs and 2) The locations of the studied outcrops as follow: 1- Gebel Taramsa: km west of Qena city (N26 10 04200 , E32 430 19200 ,) 2- Gebel Qreiya: at the Road to Safaga, after 15 km to the left across railroad in the main entrance of Wadi Qena (N26 300 18800 , E32 520 30500 ,) 3- Gebel Arras section: along the road to Safaga at 11 km sign, at Bir Araas to the left (N26 220 43600 , E32 450 27600 ,) 4Gebel Duwi: the section is located about 20 km from Quseir, km west of the Qift-Quseir Road (N25 140 65000 ; E32 450 99400 ,) Materials and methods Detailed sampling was performed for the PETM interval in the four sections A total of 81 samples were sampled at high resolution level (sample spacing of 1e50 cm) for all sections Preparation of slides followed the random settling technique (Geisen et al., 1999) using Norland-61 optical adhesive as a mounting medium Slides were examined in the micrpaleontological lab in the Geologie €t Bochum, Germany using an olymbus instituit, Ruhr Universita microscope The slides were examined under cross polarized, transmitted, and phase-contrast light at 1250x and 1600x magnification For most samples 300e400 specimens were counted per slide Absolute abundance was calculated using the calibration of (Geisen et al., 1999) Relative abundance of individual nannofossil species and overall preservation of the nannofossil assemblages were recorded in quantitative estimates under a magnification of 1600x for each sample The average state of preservation of the nannofossil assemblage in each sample is designated following those of (Arney and Wise, 2003) as follows: VG ¼ very good, G ¼ good, M ¼ moderate, P ¼ poor Tables 1e4 Results The calcareous nannofossil assemblages through the PETM at the studied sections show similar trends, although the magnitudes of the fluctuations are different Preservation of calcareous nannofossils at the studied area in general is moderate to good The calcareous nannofossil display a high species richness throughout the interval investigated especially in the upper part with a slight decrease in species richness and absolute abundance in the lower portion of the PETM 5.1 Gebel Taramsa section Calcareous nannofossils in the interval of NP9a have abundances of 0.7e1 109 specimens/g sediment Dissolution interval of 10 cm is nearly barren in the lower part of NP9b Lower abundances (0.1 109 specimens/g sediment) occur mainly in less well preserved nannofossil assemblages in the interval 0.77 m, whereas samples with good preservation show high abundances between and 109 specimens/g sediment in the rest interval of NP9b Calcareous nannofossils in the interval of NP10a have abundances of 1e2 109 specimens/g sediment Diversity varies throughout the investigated interval from 11 to 36 species/sample In the NP9a interval a diversity of 21e25 species/sample has been observed In the interval of NP9b diversity ranges from 11 to 36 species The interval of NP10a is characterized by high diversity (32e36 species/sample) Out of a total of 36 species recorded in the studied interval, nine taxa (Coccolithus spp., Toweius spp., Fasciculithus spp., Campylosphaera dela, Chiasmolithus spp., Discoaster spp., Rhomboaster spp., Tribrachiatus spp., Sphenolithus spp.) make the bulk of the calcareous nannofossil abundance (Fig 3) These taxa account more than 80% of the assemblage in all samples The most common genus is Coccolithus represented by three species Coccolithus pelagicus, Coccolithus subpertusus and Coccolithus formosus C pelagicus (Fig 3) varies from 13.5% (0.48 m) to 76.8% (0.45 m) In the interval of NP9a (0.0e0.35 m) C pelagicus usually accounts 44e51.1% of the assemblage C pelagicus count 13.5e49.6% with maximum at 0.45 m (76.8%) in the interval of NP9b The interval of NP10a has values of C pelagicus range from 26.7% to 50.8% Toweius makes up 13e22.6% of the total abundance in the NP9a interval In the interval of NP9b Toweius ranges 35e43.8% with the minimum 2.6% (at 0.48 m) The following interval of NP10a has abundances of Toweius from 24.7 to 56.8% and thus is quite common The other common taxa are as follow: Coccolithus subpertusus (4.4e23.4%); Fasciculithus spp (1.1e17.7%) with abrupt decrease in the basal part of the NP10a; Discoaster spp (2.6e32.3%); Sphenolithus spp (0.8e7.6%); Rhomboaster spp (1e27.6%) and Campylosphaera dela/ eodela (0.3e4.3%) Fig 5.2 Gebel Araas section In the interval of the NP9a the calcareous nannofossil absolute abundance is relatively low range from 0.4 to 109 specimens/g sediment High abundances (0.5e3 109 specimens/g sediment) occur in the interval of NP9b Calcareous nannofossils in the interval of NP10a have abundances of 0.9e3 109 specimens/g sediment Divers assemblage was recorded from the investigated interval ranges from 24 to 33 species/sample In the NP9a interval a M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 205 Fig Location map, ¼ Taramsa section, ¼ Araas section, ¼ Qeryia section, ¼ Duwi section diversity of 24e29 species/sample has been recorded In the interval of NP9b diversity ranges from 25 to 32 species The upper part of the studied interval (NP10a) is characterized by high diversity between 29 and 33 species/sample (Fig 4) The most common taxa in the studied interval are C pelagicus followed by Toweuis and the two taxa count more than 60% of the total assemblage In the course of NP9a C pelagicus range from 25.3 to 43.7% and abruptly increase in the interval of NP9b (31.6e66.3%) It has the same trend in the interval of NP10a and range from 29 to 60.7% The genus Toweuis is mainly represented by Toweius pertusus and T toave and display high abundance in the interval of NP9a and range form10.8e30.1% It increases in abundance upward constitute 20.6e49.9% in the interval of NP9b and 25e49.6% in the interval of NP10a The third common taxa is Discoaster which is constitute abundance range of 15.1e22.8%, 3.3e11.2% and 7.4e13% in the interval of NP9a, NP9b and NP10a respectively Fasciculithus has high abundance in the interval of NP9a constitute 9.3e19.9% of the total assemblage It decreases abruptly both in abundance and diversity in the rest of the studied interval (0.3e1.7%) Other common genera in the studied interval of Araas section include Sphenolithus (1e19.3%), Rhomboaster spp (0.3e3.7%) and Neochiastozygus spp (0.3e3.2%) Fig 5.3 Gebel Qeryia Nannofossil abundance in Qeryia section is consistently moderate to high ranges from 0.002-1x 109 specimens/g sediment in the lower most intervals 0e0.25 m (NP9a) The abundance increases in the course of NP9b and range from 0.9 to 109 specimens/g sediment with the minimum amount at 0.30 m (0.004 109specimens/g sediment) In the upper most part of the studied interval (NP10a) the absolute abundance of calacerous nannofossil ranges from to 109 specimens/g sediment Diversity is moderate to high varies from 25 to 29 species in the NP9a interval The diversity ranges from to 31 through the NP9b interval with very low diversity (3 species) at 0.30 m High diversity has been observed in the interval of NP10a ranges from 23 to 33 species per sample Throughout the studied interval the calcareous nannofossil assemblage is dominated by Coccolithus and the main components are C pelagicus and C subpertusus which account together more than 70% percent from the total assemblage In the interval of the NP9a C pelagicus and C subpertusus range from 41.2 to 50% and 6e10.9% respectively The abundance of Coccolithus is very high through the course of NP9b It ranges from 38.6 to 87% and 1.8e11.2 for C pelagicus and C subpertusus respectively with peak of C pelagicus (92.8%) at 0.45 m The abundance of C pelagicus and C subpertusus decreased rapidly in the interval of NP10a to 26e38.5% and 4.7e6.4% respectively Toweuis is the second abundant genus in the studied interval, it is comprises 26.1e50% of the entire assemblage in NP9a interval The abundance of Toweuis still high in the interval of NP9b, it ranges from 9.2 to 42.8% with very low abundance (0.3%) at 0.45 m Very high abundance of Toweius was observed in NP10a interval ranges from 42.3 to 57.1% Discoaster which represented by many species is the third common taxon ranges from 4.2 to 6.8% in the interval of NP9a and from 1.4 to 11.1% in the interval of NP9b The abundance of Discoaster slightly decreases in the upper part of the studied interval (NP10a) ranges 206 M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 Fig Lithostratigraphic units of the PaleoceneeEocene succession exposed at studied sections from 1.1 to 3.2% Fasciculithus comprises 4.7e8.6% in the NP9a interval and increases in the NP9b ranges from 0.8 to 11.3% Fasciculithus abruptly decreases both in abundance and diversity rarely constitute 0.3e1.1% of the total assemblages Other taxa such as Sphenolithus, Rhomboaster and Neochiastozygus constitute less than 10% of the total assemblages in the studied interval (Fig 5) 5.4 Gebel Duwi Calcareous nannofossil preservation varies from medium to good in most samples and poor to moderate preservation around the boundary The absolute abundance in the lower part of the studied interval is high ranges from to 109 specimen/g sediment The abundance decrease in the interval around the P/E boundary from 0.08 to 0.03 109 specimen/g sediment In the upper part of NP9b subzone absolute abundance increases to 109 specimen/g sediment with maximum value (5 109) at 1.20 m It decreases again in the studied part of NP10a to 0.3 109 specimen/g sediment The calcareous nannofossil assemblage is moderate to high diverse comprises 10e32, 16e31 and 32 species/ sample in the interval of NP9a, NP9b and NP10a respectively The calcareous nannofossil assemblage characterized by Paleocene low latitude taxa (Coccolithus and Toweius) Coccolithus pelagicus is the most abundant species through the studied interval ranges from 19 to 52.3% and increases markedly in the upper part of NP9b interval (74.3%) at 1.20 m Toweius is very common in the interval of NP9a ranges from 16.9 to 62% Frequent occurrences of Toweius has been recorded through the interval of NP9b (1.6e36.1%) with its maximum (46.2%) at 1.50 m, it is still high in the interval of NP10a (35.1%) Other abundant nannofossils are: Coccolithus subpertusus (1.8e24.9%), Fasciculithus (0.3e12.9%), D araneus (0.4e10.3%), Sphenolithus (0.6e9.7%), Discoaster (0.6e9.7%), Rhomboaster (0.4e6.2%) Pontosphaera (0.3e2.3%) and Neochiastozygus (0.8e4.8%) (Fig 6) Biostratigraphy The calcareous nannofossil biostratigraphy of the lower Paleogene in Egypt have been investigated by many workers in the last thirty years and placed the P/E boundary either at the top of Zone NP9 or within Zone NP10 (e g Kerdany, 1970; Faris et al., 1985; Von Salis et al., 1998; Monechi et al., 2000; Tantawy et al., 2000; Youssef and Mutterlose, 2004) Calcareous nannofossils in the study area are generally abundant to common, highly diverse, and moderately to well preserve However, the absolute abundances, diversity and preservation significantly decrease in the thin dissolution interval (Bed of Dababiya Quarry beds) in the basal Eocene The current study spans the latest Paleocene-early Eocene biostratigraphy (Zones NP9- NP10) based essentially on the standard zonal scheme of Martini (1971) Fig 6.1 Discoaster multiradiatus zone (NP9) This zone spans the interval from the first occurrence of D M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 207 Table Absolute abundance of calcareous nannofossils, diversity and relative abundance data of selected species in Taramsa section X ¼ Species had been recorded in addition traverse investigation but not counted Biozone (Martini, 1971) NP9 NP10 NP9a Camylasphaera dela Camylasphaera eodela Cruciplacolithus tenuis Chiasmolithus bidnes C consuetus C eograndis Coccolithus formosus Coccolithus pelagicus Coccolithus subpertusus Discoaster aegyptiacus Discoaster araneus Discoaster anartios Discoaster delicates Discoaster diastypus Discoaster falcatus Discoaster lenticularis Discoaster limbatus Discoaster mahmoudi Discoaster medosius Discoaster multiradiatus Discoaster nobilis Discoaster binodosus Discoaster elegans Fasciculithus alanii Fasciculithus clinatus Fasciculithus hayii Fasciculithus involutus Fasciculithus lillianae Fasciculithus schaubii Fasciculithus thomasii F tympaniformis Fasciculithus auberta Fasciculithus bobii Fasciculithus richardii Pontospharae versa P inconspicus Neochiastozygus junctus N distentus N protenus Placozygus sigmoides Zygodiscus adamas Zygodiscus bramlettei Zygodiscus herlynii Sphenolithus primus S anarrhopus Toweius eminens Toweius pertusus Toweius tovae Ellipsolithus macellus Ellipsolithus distichus Rhomboaster cuspis Rhomboaster bitrifida Rhomboaster calcitropa Rhomboaster spineus Tribrachiatus bramlettei Thoracosphaera Zygrhablithus bijugatus Lophodolithus nascens NP9b NP10 a 10 11 12 13 14 15 16 0 0 0 147 62 0 0 0 0 29 0 12 13 11 x 0 0 0 0 13 32 0 0 0 0 0 x 157 56 0 0 0 0 29 0 11 11 x 0 0 0 0 19 31 x x 0 0 0 0 x 0 181 20 0 0 0 0 11 0 13 4 0 0 0 25 73 x 0 0 0 0 0 0 187 35 0 0 0 0 x 0 11 10 0 0 20 53 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 288 29 28 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 13 0 0 0 0 0 26 45 60 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 24 23 0 0 0 171 30 27 0 0 0 0 x 1 0 0 0 0 0 11 1 13 0 11 25 16 12 x 0 0 0 0 145 18 15 0 1 0 0 x 1 x 0 x 0 0 x 135 x 0 0 1 140 29 12 x x 0 x 0 0 1 0 x x 0 0 x 0 0 x 142 x 0 x x 0 x x x x 186 15 0 0 0 1 x 0 1 x x x x 133 x x 1 0 x 0 x x 167 17 x 0 x 0 x 0 x x 0 x x x 0 0 3 115 x 0 x x 0 10 1 x 110 0 x x x 17 0 x 0 x 0 0 0 10 150 1 x 2 x 0 x x x 189 19 0 0 x x 15 1 0 x 0 0 0 x 1 10 5 85 0 x 0 x x 101 17 0 0 x x 1 0 0 0 1 0 x x x 3 218 0 0 x x 14 x x 1 119 30 0 0 x 2 0 1 0 0 1 x 2 157 x 0 0 x x multiradiatus to the FO of Tribrachiatus bramlettei and has an estimated duration of 1.2 my (Berggern et al., 1995) The studied part of Zone NP9 attains 1.45 m, 2.70 m, m, 1.42 m and 1.60 in Taramsa, Araas, Qeriya, and Duwi sections respectively A thin dissolution interval is observed in the middle part of Zone NP9 (Bed DQB) and marked by a notable decrease, or absence, of calcareous nannofossils A subdivision of Zone NP9 has been suggested by various authors based on the first occurrence of Campylosphaera dela/eodela or the FO of Rhomboaster spp and D araneus According to Bukry (1973), Campylosphaera eodela has its first occurrence within Zone NP9 and defines the CP8a/b Subzonal boundary of Okada and Bukry (1980) This agrees well with the occurrence reported by Perch-Nielsen (1985) The FO of C dela/eodela appears to be a good marker species for subdividing NP9 into subzones a, b The rare FO of C.(eo)dela is recorded directly above the dissolution interval (Bed of DQB) together with the FO of D araneus and the first 208 M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 Table Absolute abundance of calcareous nannofossils, diversity and relative abundance data of selected species in Araas section X ¼ Species had been recorded in addition traverse investigation but not counted Biozone (Martini, 1971) NP9 Np10 NP9 a NP9 b NP 10 a Sample number 10 11 12 13 14 15 16 Camylasphaera dela Camylasphaera eodela Cruciplacolithus tenuis Chiasmolithus bidnes Chiasmolithus consuetus Chiasmolithus eograndis Chiasmolithus solitus Coccolithus formosus Coccolithus pelagicus Coccolithus subpertusus Discoaster aegyptiacus Discoaster araneus Discoaster anartios Discoaster araneus Discoaster delicates Discoaster diastypus Discoaster falcatus Discoaster lenticularis Discoaster limbatus Discoaster mahmoudi Discoaster medosius Discoaster mohleri Discoaster multiradiatus Discoaster binodosus Fasciculithus alanii Fasciculithus clinatus Fasciculithus hayii Fasciculithus involutus Fasciculithus lillianae Fasciculithus schaubii Fasciculithus thomasii Fasciculithus tympaniformis Fasciculithus auberta Fasciculithus bobii Fasciculithus richardii Pontospharae inconspicus Pontospharae versa Neochiastozygus distentus Neochiastozygus junctus Neococcolithus protenus Placozygus sigmoides Zygodiscus adamas Zygodiscus bramlettei Zygodiscus herlynii Sphenolithus anarrhopus Sphenolithus primus Toweius eminens Toweius pertusus Toweius tovae Ellipsolithus macellus Ellipsolithus distichus Rhomboaster cuspis Rhomboaster bitrifida Rhomboaster calcitropa Rhomboaster spineus Tribrachiatus bramlettei Thoracosphaera 0 0 0 97 20 0 0 0 x 0 36 30 0 0 1 0 14 43 87 1 0 0 0 0 x 1 x x 89 18 0 0 0 0 24 1 13 x 0 0 0 x 0 68 15 91 x 0 0 0 0 0 1 x 1 112 33 0 0 0 0 27 1 19 19 3 24 0 0 0 35 11 45 1 0 0 0 0 1 1 145 52 0 0 0 0 26 14 2 0 0 0 0 21 30 0 0 0 0 0 0 x 0 94 52 0 0 0 11 0 14 10 10 x 16 0 0 x 0 28 87 x 0 0 0 0 1 0 159 40 3 0 x 0 0 0 0 0 2 0 0 0 101 1 x x x 0 0 0 203 13 x 10 10 0 0 0 0 0 x x 0 0 x x x 0 0 x 91 2 2 1 0 x 0 238 2 0 0 x 0 0 x x x 1 0 x 0 0 x 12 72 x 0 x 0 x 1 0 140 25 0 x x 0 0 x 0 0 0 13 150 x x x 0 x 0 124 11 x 0 x 0 0 0 0 0 1 0 10 180 x x 0 10 x x x 0 113 39 0 x 0 x x x 0 x x 0 x 0 0 7 0 161 x x 1 x x 1 0 115 34 0 0 1 x 0 x 0 0 x x 0 11 x 2 12 125 x x 0 x 3 x 0 0 204 23 0 0 x 0 0 0 0 0 0 0 0 0 1 81 1 0 x x x 10 x x x x 0 118 20 2 2 x 0 x 0 x 0 1 0 13 1 190 x x 0 0 x x x x x 0 158 24 0 0 0 x x 0 0 0 0 0 0 x x x 104 0 0 0 18 1 x 106 39 0 0 x x 0 x 0 0 0 0 x x x 161 0 0 0 representatives of Rhomboaster (Rhomboaster cuspis, Rhomboaster spineus and Rhomboaster birifida) The NP9a/b subzonal contact is drawn at the lowest occurrence of C (eo) dela and/or D araneus A major turnover in the calcareous nannofossil assemblage has been observed around this horizon 6.2 Tribrachiatus contortus zone (NP10) This zone corresponds to the interval between the FO of Tribrachiatus bramlettei and the last occurrence (LO) of Tribrachiatus contortus The studied part of this zone is about 0.50, 0.90, 0.75 m and 0.20 m in the Taramsa, Araas, Qeriya and Duwi sections respectively The last occurrence of Fasciculithus spp has been used by many authors to approximate the NP9/NP10 boundary In the Egyptian sections, representatives of the genus Fasciculithus decreases markedly both in diversity and abundance in the middle part of Zone NP9 and the genus is extinct in the basal part of Zone NP10 The FO of D diastypus, which marks the CP8/9 zonal M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 209 Table Absolute abundance of calcareous nannofossils, diversity and relative abundance data of selected species in Qreiya section X ¼ Species had been recorded in addition traverse investigation but not counted Biozones (Martini, 1971) NP9 NP 10 NP a NP b NP 10 a Sample number 10 11 12 13 14 15 16 17 18 19 Camylasphaera dela Camylasphaera eodela Cruciplacolithus tenuis Chiasmolithus bidnes Chiasmolithus consuetus Chiasmolithus eograndis Chiasmolithus solitus Coccolithus formosus Coccolithus pelagicus Coccolithus subpertusus Discoaster araneus Discoaster anartios Discoaster delicates Discoaster diastypus Discoaster falcatus Discoaster lenticularis Discoaster mahmoudi Discoaster mediosus Discoaster mohleri Discoaster multiradiatus Discoaster nobilis Discoaster binodosus Fasciculithus alanii Fasciculithus clinatus Fasciculithus hayii Fasciculithus involutus Fasciculithus lillianae Fasciculithus schaubii Fasciculithus thomasii Fasciculithus tonii Fasciculithus tympaniformis Fasciculithus auberta Fasciculithus bobii Fasciculithus richardii Pontospharae inconspicus Pontospharae versa Neochiastozygus distentus Neochiastozygus junctus Neococcolithus protenus Placozygus sigmoides Zygodiscus herlynii Sphenolithus anarrhopus Sphenolithus primus Toweius eminens Toweius pertusus Toweius tovae Ellipsolithus macellus Ellipsolithus distichus Rhomboaster cuspis Rhomboaster bitrifida Rhomboaster calcitropa Rhomboaster spineus Tribrachiatus bramlettei Thoracosphaera Zygrhablithus bijugatus Lophodolithus nascens 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 x x 0 162 26 0 0 0 x 15 x x x x x 0 0 0 0 10 77 12 x 0 0 0 0 0 0 0 173 23 0 0 3 18 5 x 10 x 0 0 0 0 22 88 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 x x x x x 140 23 0 0 x 8 x x 12 x 0 x 0 23 105 x 0 0 0 0 0 x 146 40 0 0 0 18 x 12 x 0 0 0 16 80 0 0 0 0 0 0 0 0 320 13 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 x x 0 0 0 0 0 299 25 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 x 158 20 12 x 0 0 0 x 0 0 x x 0 10 134 x x 0 0 0 0 144 22 18 0 0 0 0 1 0 0 0 x 0 17 1 2 10 0 0 0 x x 0 180 23 0 2 0 0 1 x 0 x 0 90 0 0 x x 0 168 0 0 x 0 0 x x x 0 x 0 x x 0 152 x x 0 x 0 x x 0 x 0 218 0 0 x 0 x 0 0 0 0 0 x 6 13 53 2 0 0 x x 10 0 x x x 211 10 0 0 0 0 0 1 0 0 0 11 2 14 78 x x 0 0 x 17 x x x 0 114 24 0 0 x x 0 0 1 x x x 0 x 11 13 15 202 x 0 1 x 14 x x 0 0 89 22 0 0 0 0 0 0 0 0 0 10 1 11 160 0 x 14 2 x x 0 140 17 0 0 2 0 0 0 0 0 0 x 0 152 x 0 0 0 x x 0 97 17 0 x x 0 0 0 0 0 x 0 x x 2 199 0 0 2 x 1 147 39 0 0 x x 12 9 x x x x x 0 0 0 1 13 88 x 0 0 0 0 boundary of Okada and Bukry (1980), is recorded with T bramlettei in the Taramsa, Araas, and Duwi sections respectively and 0.65 m below the FO of T bramlettei in the Qeryia section In the present study the FO of T bramlettei (which is clearly distinguished from R cuspis, Rhomboaster bitrifida and R spineus) marks the NP9/NP10 zonal boundary following the original definition of Martini (1971) The Subzone NP10a - Tribrachiatus bramlettei-Tribrachiatus digitalis Interval Range Subzone, spans the interval between the FO of T bramlettei and the FO of T digitalis.Only the basal part of this zone was distinguished in the study sections Discussion 7.1 Calcareous nannofossil turnover The interval of NP9-NP10 in the studied sections is characterized by a succession of FO, LO and acmes of several taxa (Figs 3e6) These stratigraphic events include the fluctuations in species diversity and total abundances of Fasciculithus and Discoaster, the change in the abundance of Coccolithus and Toweius, and the first occurrence and thriving of the species of Rhomboaster and 210 M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 Table Absolute abundance of calcareous nannofossils, diversity and relative abundance data of selected species in Duwi section X ¼ Species had been recorded in addition traverse investigation but not counted Biozones (Martini, 1971) NP NP a NP b Sample number 10 11 12 13 14 15 Camylasphaera dela Camylasphaera eodela Cruciplacolithus tenuis Chiasmolithus bidnes Chiasmolithus consuetus Chiasmolithus eograndis Chiasmolithus solitus Coccolithus formosus Coccolithus pelagicus Coccolithus subpertusus Discoaster aegyptiacus Discoaster araneus Discoaster anartios Discoaster delicates Discoaster diastypus Discoaster lenticularis Discoaster limbatus Discoaster mahmoudi Discoaster multiradiatus Discoaster nobilis Discoaster binodosus Fasciculithus alanii Fasciculithus clinatus Fasciculithus hayii Fasciculithus involutus Fasciculithus schaubii Fasciculithus thomasii Fasciculithus tympaniformis Fasciculithus auberta Fasciculithus bobii Pontospharae inconspicus Pontospharae versa Neochiastozygus distentus Neochiastozygus junctus Neococcolithus protenus Placozygus sigmoides Zygodiscus adamas Zygodiscus bramlettei Zygodiscus herlynii Sphenolithus anarrhopus Sphenolithus primus Toweius eminens Toweius pertusus Toweius tovae Ellipsolithus macellus Ellipsolithus distichus Rhomboaster cuspis Rhomboaster bitrifida Rhomboaster calcitropa Rhomboaster spineus Thoracosphaera Zygrhablithus bijugatus Scapholithus apertus Lophodolithus nascens 0 0 0 91 0 0 0 0 0 1 x 0 0 2 16 101 95 x 0 0 x 0 0 0 90 0 0 x 0 0 1 0 1 x 0 1 26 95 92 0 0 0 1 0 0 x x 175 0 0 0 x x 1 x x 0 x x 81 22 x 0 0 x 1 0 0 32 0 0 0 0 0 0 1 0 0 0 0 0 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 1 27 0 0 0 0 0 0 0 0 0 0 21 0 0 0 0 0 0 0 0 102 27 0 0 0 1 1 0 0 0 1 16 33 13 0 0 0 0 0 0 0 197 88 22 0 0 0 x x x 0 2 0 1 13 13 x 0 0 0 0 223 29 0 0 0 0 0 x x x 0 0 0 0 0 1 12 0 x x 0 x 0 x 0 286 33 35 0 x 0 x x x x 0 0 0 0 15 x x 0 0 0 0 175 97 x 40 0 0 x 0 0 x x 0 x x 2 38 0 3 x x 0 0 0 0 268 33 x 20 0 x x x 0 0 1 x 0 0 0 x 18 0 x x 0 10 x x x 125 0 0 0 x 0 x 0 10 x 155 0 0 11 1 147 10 0 1 10 0 0 x 0 3 0 11 118 2 0 0 0 x x 0 1 2 116 10 0 0 0 0 0 1 0 13 0 0 90 1 0 0 asymmetrical Discoasters (D araneus, D anartios and D aegyptiacus) during the PETM The Fasciculithus spp show an abrupt change across the Paleocene/Eocene transition The abundance of Fasciculithus below the PETM attains 6e20% of the total nannofossil abundance The diversity is ~9 species in the uppermost Subzone NP9a with first occurrence datums of Fasciculithus tonii, Fasciculithus alanii, Fasciculithus hayi, Fasciculithus bobii, Fasciculithus schaubii, and Fasciculithus richardii and continuous occurrence of Fasciculithus tympaniformis The diversity and abundance of Fasciculithus decreased sharply across the NP9a/b subzonal boundary which correlates well with the dissolution interval at the base of the DQM, where the Fasciculithus diversity fluctuates between and species The Fasciculithus extinction occurs in the lowermost part of NP10 F tympaniformis F involutus are recorded in basal part of Zone NP10, while most of Fasciculithus species such as F hayi, Fasciculithus clinatus, Fasciculithus lillianae, F bobii, Fasciculithus alanii and Fasciculithus mitreus disappeared near the upper part of NP9b The LAD of Fasciculithus, which has been used to approximate the NP9/NP10 zonal boundary (Aubry et al., 1996; Youssef and Mutterlose, 2004; Tantawy, 2006) extends in the study area upward into the lowermost part of Zone NP10 The same observations were recorded in the Qreiya, Duwi and Owaina sections M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 211 Fig Absolute abundance, diversity and relative abundance of selected nannofossil species in Taramsa section Fig Absolute abundance, diversity and relative abundance of selected nannofossil species Araas section (Von Salis et al., 1998) and in G Taramsa, G Serai (Tantawy, 2006) The same overlap of the range of T bramlettei and F tympaniformis is recorded in other localities in the world i.e., Italy (Proto Decim et al., 1975), Israel, Spain (Angori and Monechi, 1996), DSDP Hole 605 (Aubry, 1995) and New Jersey (Bybell and Self-Trail, 1997) Coccolithus pelagicus and Toweius dominant the nannoplankton assemblages throughout the studied interval making up 70% of the assemblage pre and post-PETM Toweius shows a sharp drop upward in relative abundance through the studied successions The abundance of Toweius (T pertusus, T.eminens, Toweius tovae), which constitute the main components of the assemblage throughout the studied interval, were decreased considerably together with an increase of the abundance of Coccolithus pelagicus/subpertusa during the PETM This phenomena (C pelagicus acme) also observed in other southern Egyptian sections (von Salis et al., 1998; Tantawy et al., 2000; Dupuis et al., 2003; Youssef and Mutterlose, 2004), 212 M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 Fig Absolute abundance, diversity and relative abundance of selected nannofossil species in Qreiya section Fig Absolute abundance, diversity and relative abundance of selected nannofossil species in Duwi section in Spain (Monechi et al., 2000), in the ODP Sites 865 (Kelly et al., 1996) and ODP Sites 690 (Bralower, 2002), various DSDP Sites (Kahn and Aubry, 2004), ODP Site 1260B (Mutterlose et al., 2007) Two acmes in the abundance of Coccolithus pelagicus/subpertusa were observed in the present studied sections (Figs 3e6) The first acme of 75e84.5% is located in the lowermost part of the DQM The second one is found in uppermost part of the PETM interval where it attains an abundance of 70% Discoaster is well represented in the studied sections showing interesting fluctuations within the studied interval of Zones NP9NP10 with rapid increase in diversity towards the PETM, and appearance of new species (i.e Discoaster binodosus, lenticularis, Discoaster falcatus, Discoaster limbatus, Discoaster mediosus, Discoaster araneus, Discoaster anartios, D aegyptiacus, Discoaster mahmoudii, and Discoaster diastypus, (Figs 3e6) The long-armed asymmetrical Discoaster araneus and Discoaster aegyptiacus with relative abundance of 32% were recorded in the middle part of the PETM interval Representatives of Rhomboaster are present and well preserved in the whole studied sections (Figs 3e6) The FO of the Rhomboaster (Rhomboaster cuspis and Rhomboaster bitrifida, Rhomboaster calcitrapa, and Rhomboaster spineus) has been recognized in the PETM interval just above the dissolution interval (Bed of the DQB) with relative abundance of 27% (Fig 3) This high abundance is restricted to the CIE interval and drops to ~1% in the remaining NP9b The FO of Tribrachiatus bramlettei which had been chosen by Martini (1971) to define the base of NP10 was rarely recorded in the studied sections The floral assemblage after the PETM characterized by sudden appearance and rapid increase of M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 213 Fig Biostratigraphy and ranges of the most important calcareous nannofossil index species for the PaleoceneeEocene succession at study area the “Excursion taxa” up ~35% These taxa include D araneus, D anartios, Rhomboaster 7.2 Excursion taxa New taxa markedly abundant at the PETM (D araneus, D anartios, D aegyptiacus, and Rhomboaster spp.) are called excursion taxa These “Excursion taxa” have been interpreted as malformed nannofossils (Jiang and Wise, 2006) The D.s and Rhomboaster make up to (32.3% and 27.6% respectively) of the assemblage and are limited to the PETM interval A similar assemblage has been described from the equatorial Pacific (Raffi et al., 2005) The excursion nannoflara (D araneus and Rhomboaster) had been recorded at (ODP Site 1260B) Atlantic Ocean (Mutterlose et al., 2007) The D.eRhomboaster spp excursion taxa characterize the Atlantic Ocean, the Tethys, the westernmost Indian Ocean and the equatorial Pacific (Kahn and Aubry, 2004; Gibbs et al., 2006a, b; Mutterlose et al., 2007) The abundance of these taxa is considered as a result of the acidification of the ocean throughout the PETM interval (Mutterlose et al., 2007; Raffi and Bernardi, 2008) A related change was recorded in Planktonic foraminifera of the PETM with the evolution of an excursion planktonic fauna These excursion taxa include: Acarinina Africana, Acarinina sibaiyaensis and Morozovella allisonensis The excursion planktonic taxa were recorded in the following sites: ODP Site 1220 (Equatorial Pacific), ODP Site 1260B (equatorial Atlantic), ODP Site 1220, the US Atlantic coast, ODP 865 (Central Pacific) (Kelly et al., 1998) The excursion planktonic taxa were also recorded in the Egyptian sections (Berggren and Ouda, 2003) In the study area the excursion planktonic taxa are very rare in E1 biozone The depletion of oxygen in the upper water column might have been one of the factors causing their prominent occurrence at the PETM (Luciani et al., 2007) 7.3 Paleoenvironmental changes The paleoenvironmental interpretation of calcareous nannofossil strongly have been established by a lot of studies (e.g Haq and Lohmann, 1976; Aubry, 1998; Bralower, 2002; Mutterlsoe et al., 2007; Raffi and Bernardi, 2008) The paleoenvironmental changes in the study interval have been investigated by means of ten important nannofossil taxa: Discoasters were divided into excursion Discoasters (Discoaster arenus, Discoaster anartios, Discoaster aegyptiacus) and normal Discoasters Discoasters have been known as warm-water specialists (Bukry, 1973) Discoaster spp has been also described as Kmode species which prefer the warm oligotrophic surface waters (Aubry, 1998; Bralower, 2002; Tremolada and Bralower, 2004) Discoasters show a stable distribution in the whole studied interval with minor fluctuations includes high abundance at the pre-PETM interval (3.5e14%) of the total assemblage The Discoaters is highly abundant in the high latitude than tropics and mid latitude and interpreted as deep dwelling and oligotrophic preference (e.g Aubry, 1998; Jiang and Wise, 2006) and cosmopolitan K-strategist with mid latitudinal affinities (Mutterlose et al., 2007) The asymmetrical aberrant Discoasters (D araneus, D anartios, D aegyptiacus) which are limited to the basal part of the CIE is explained as malformation for Discoaster due to high CO2 concentration and low PH (Jiang and Wise, 2006; Mutterlose et al., 2007) Coccolithus pelagicus now is well represented in North Atlantic , 1967), and shows an optimum growth temper(McIntyre and Be ature between and 12 C (Okada and Bukry, 1980), Jiang and Wise, 2006 used Coccolithus pelagicus as a temperature and productivity proxy in Neogene paleoceanographic studies C pelagicus is uncommon or rare in high and mid latitudinal sites, while it was highly abundant in tropical and low latitudinal sites In Paleocene/ Eocene times This variation was considered as an effect of the gradual warming in Cenozoic or perhaps C pelagicus migrate to the cooler environments through time Haq and Lohmann (1976) 214 M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 Based on its co-occurrence with the excursion taxa Coccolithus subpertusus has been considered as an oligotrophic warm water species (Aubry, 1998) In the studied interval the abundance of C subpertusus increases from ~2% in pre-PETM to more than 23% during the PETM and suggest warm and oligotrophic conditions The co-occurrences of C subpertusus with the excursion Discoasters and Rhomboaster was considered similar ecological preferences of these three taxa (Mutterlose et al., 2007) Toweius spp are global (Haq and Lohmann, 1976) and shows higher abundance in high latitudes and has been interpreted as they prefer warm and mesotrophic conditions (Bralower, 2002; Gibbs et al., 2006a) Toweius is still abundant during the PETM in the whole studied sections suggesting not very well defined habitat Due to it is abundant occurrence during the PETM Toweius is considered as a cosmopolitan generalist without any specific ecological affinity (Mutterlose et al., 2007) Fasciculithus shows an abrupt decline of both diversity and abundance in the upper most part of NP9b and basal part of NP10 in the studied area The close association of Fasciculithus with Discoasters and the inverse correlation with Prinsius martini has been interpreted by Haq and Lohmann, 1976 as a warm oligotrophic taxon Fasciculithus inhabit oligotrophic conditions as its close association with Discoasters in pre-PETM at Site 1260B (Gibbs et al., 2006a; Mutterlose et al., 2007) Chiasmolitus is very rare in the studied interval indicating a warm water conditions, it has been interpreted as a eutrophic cold water taxon (Bralower, 2002; Gibbs et al., 2006a) Campylosphaera has been considered as mesotrophic taxon (Gibbs et al., 2006a) In the studied area a moderate increase in the abundance of Campylosphaera begin in the lower most part of NP10 (5%) and considered as a “recovery” phase of the PETM (Fig 8) This taxon is rare at many mid and high latitudinal sites and seems to have preferred eutrophic warmer surface waters (Mutterlose et al., 2007) Sphenolithus is considered to have been adapted to warm oligotrophic waters based on its close association with Discoaster (Wei and Wise, 1990) Sphenolithus have been considered as Kstrategist prefers warmer more oligotrophic environments (Bralower, 2002) In the studied area Sphenolithus is common through the studied interval, increasing in the pre-PETM interval (reach to 20%) Rhomboaster/Tribrachiatus lineage co-occurred with excursion Discoasters and adapted to very warm and oligotrophic conditions (Aubry, 1998), it had positive correlation with other oligotrophic taxa such as C subpertusus and Sphenolithus (Mutterlose et al., 2007) The Rhomboasters in the studied area are limited to the PETM interval means that a higher salinity and a potential acidification prevailed during the PETM caused the onset of Rhomboaster/Tribrachiatus (Aubry, 1998; Mutterlose et al., 2007) Zygodiscaceae are represented by Neococcolithes, Neochiastozygus and very rare occurrence of Zygrhablithus bijugatus The first two genera are abundant in the studied interval and increase in the lower most part of NP10 (~5%) co-occurred with Campylosphaera Both genera were considered as mesotrophic taxa (Gibbs et al., 2006a) The index species are illustrated in Figs 9e11 Conclusions Quantitative analyses of 81 samples from four outcrops in Central Egypt have documented primary changes in the calcareous nannofossil assemblages across the PETM The relative abundance changed from Discoaster, Fasciculithus and Toweius (K-mode specialists) to Coccolithus pelagicus, and C subpertusus (R-mode specialists) An abrupt decrease in the diversity and abundance of Fasciculithus occurs across the NP9a/b subzonal boundary until its extinction in the lower part of NP10 The representatives of the genus Toweius, which comprise the main components of the nannofossil assemblage throughout the PaleoceneeEocene interval, were found to decrease considerably together with an increase of Coccolithus pelagicus/subpertusus during the PETM Discoasters show a stable distribution within Zones NP9-NP10 Discoaster and Fig Summary of the paleoenvironmental interpretation of the PaleoceneeEocene transition at studied sections M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 215 Fig 1- Campylosphaera dela, T-16, 2- Campylosphaera eodela, T-16, 3-Cruciplacolithus tenius, Q1-24, 4-Chiasmolithus bidens, D-15, 5- Chiasmolithus consuetus, Q1-24, 6- Chiasmolithus eograndis, D-17, 7- Coccolithus pelagicus, T-16, 8- Coccolithus subpertusus, Q2-29, 9- Ellipsolithus macellus, D-15, 10- Ellipsolithus distichus, T-16, 11- Neochiastozygus distentus, T-16, 12, 13- Neochiastozygus junctus, T-15, 14- Neococcolithes protenus, D-17, 15-Lophodolithus nascens, Q2-29, 16-Zygodiscus sigmoides, T-16, 17- Zygodiscus herlynii, D-15, 18Zygrhablithus bijugatus, D-17, 19- Pontosphaera inconspicua, D-15, 20- Pontospharea versa, D-15., D-15 Coccolithus are interpreted as indicators of warm waters and adapted to oligotrophic environment The gradual increase of Toweius accompanied with gradual increase of Campylosphaera immediately above the CIE indicate return to eutrophic warmer surface waters environment The significant changes of the calcareous nannofossils demonstrate that the low latitudes environments were dramatically affected by the global climatic changes of the PETM 216 M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 Fig 10 1- Sphenolithus primus, Q2-29, 2- Scapholithus apertus, Q2-29, 3-Toweius pertusus, T-16, 4- Toweius tovae, Q2-29, 5- Fasciculithus alanii, T-2, 6- Fasciculithus aubertae, D-12, 7Fasciculithus clinatus, Q1-24, 8- Fasciculithus clinatus, Q1-24, 9- Fasciculithus hayi, Q2-29, 10- Fasciculithus involutus, T-2, 11- Fasciculithus lillianae, Q1-24, 12- Fasciculithus lillianae, Q1-24, 13- Fasciculithus richardii, T-2, 14- Fasciculithus schuabii, T-2, 15- Fasciculithus schuabii, Ar-5, 16- Fasciculithus thomasii, D-3, 17- Fasciculithus thomasii, D-3, 18- Fasciculithus tympaniformis, T-2, 19- Fasciculithus sp.1, D-3, 20- Fasciculithus sp 2, Q1-24 M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 217 Fig 11 1- Discoaster araneus, D-11, 2- Discoaster araneus, D-12, 3- Discoaster araneus, Q2-25, 4- Discoaster binodosus, Ar-5, 5- Discoaster diastypus, T-15, 6- Discoaster falcatus, Q2-29, 7- Discoaster falcatus, D-17, 8- Discoaster lenticularis, Q2-29, 9- Discoaster mahmoudii, T-15, 10- Discoaster multiradiatus, T-15, 11- Discoaster multiradiatus, D-15, 12- Discoaster nobilis, Q1-24, 13- Discoaster sp.1, Q1-24, 14- Discoaster sp.2, T-16, 15- Rhomboaster bitrifida, D-12, 16- Rhomboaster calcitrapa, D-11, 17- Rhomboaster cuspis, D-11, 18- Rhomboaster spineus, D12, 19- Tribrachiatus bramlettei, T-15, 20- Tribrachiatus bramlettei, Ar-16 218 M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 Acknowledgments This project was supported by King Saud University, Deanship of Scientific Research, and College of Science Research Center I gratefully acknowledge Prof Mahmoud Faris (Tanta University) for critical comments I would like 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nannofossils in the PETM interval in order to understand the paleoenvironmental... and Mutterlose, 2004) Calcareous nannofossils in the study area are generally abundant to common, highly diverse, and moderately to well preserve However, the absolute abundances, diversity and. .. Coccolithus and Toweius, and the first occurrence and thriving of the species of Rhomboaster and 210 M Youssef / Journal of African Earth Sciences 114 (2016) 203e219 Table Absolute abundance of calcareous