Calcareous nannofossils and paleoenvironments of the PaleoceneeEocene thermal maximum (PETM) interval in central Egypt

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Calcareous nannofossils and paleoenvironments of the

PaleoceneeEocene thermal maximum (PETM) interval in central

Egypt

aDepartment of Geology and Geophysics, College of Science, King Saud University, Saudi Arabia

bDepartment of Geology, Faculty of Science, South Valley University, 83523 Qena, Egypt

a r t i c l e i n f o

Article history:

Received 9 September 2015

Received in revised form

19 November 2015

Accepted 23 November 2015

Available online 2 December 2015

Keywords:

Calcareous nannofossils

Biostratigraphy

Paleoenvironments

PETM

Central Egypt

a b s t r a c t

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 res-olution 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

char-acterizes the return to normal conditions

1 Introduction

The Palaeocene/Eocene Thermal Maximum (PETM) was a

cata-strophic climate event continued about 220 kyr (R€ohl et al., 2000)

at ~55.5 my ago The sea-surface temperature elevated by 5C in

the tropics and as much as 9 C at the high latitudes by this global

warming (Zachos et al., 2003), whereas bottom water warmed by

4e5C (Thomas et al., 2000) This event is one of the warmest

intervals of the Cenozoic, which followed a warming trend that

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

in-terval 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

abrupt climatic change associated with the PETM (Zachos et al.,

benthic foraminiferal species have extinct (Tjalsma and Lohmann,

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 wa-ters 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 chem-ical 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.,

* Department of Geology, Faculty of Science, South Valley University, 83523 Qena,

Egypt.

E-mail address:myousefgeology@gmail.com

Contents lists available atScienceDirect

Journal of African Earth Sciences

j o u r n a l h o m e p a g e :w w w e l s e v i e r c o m / l o c a t e / j a f r e a r s c i

http://dx.doi.org/10.1016/j.jafrearsci.2015.11.021

Journal of African Earth Sciences 114 (2016) 203e219

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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

nanno-fossils 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

calcar-eous 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)

2 Lithostratigraphy

The Late CretaceouseEarly Eocene sedimentary rocks in central

and southern Egypt are characterized by gradual facies

differenti-ation (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

succes-sion ﬁrstly as Dababiya Quarry beds (DQB) and now (Aubry et al.,

Member in the Global stratotype section (Dababiya section) is

about 1.90 m thick and divided into 5 beds In the studied area the

all beds of Dababiya Quarry Member are not present (Fig 2)

3 Measured sections

The samples used in this study were collected from Gebel

Tar-amsa, Nile Valley; Gebel Qreiya, Gebel Araas sections in Wadi Qena,

and Gebel Duwi in the Red Sea Coast (Figs 1 and 2) The locations of

the studied outcrops as follow:

1- Gebel Taramsa: 6 km west of Qena city (N261004200, E32430

19200,) 2- Gebel Qreiya: at the Road to Safaga, after 15 km to the left

across railroad in the main entrance of Wadi Qena (N2630018800,

E3252030500,) 3- Gebel Arras section: along the road to Safaga at

11 km sign, at Bir Araas to the left (N2622043600, E3245027600,)

4-Gebel Duwi: the section is located about 20 km from Quseir, 5 km

west of the Qift-Quseir Road (N2514065000; E3245099400,)

4 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

instituit, Ruhr Universit€at Bochum, Germany using an olymbus

microscope The slides were examined under cross polarized,

transmitted, and phase-contrast light at 1250x and 1600x

magni-ﬁcation 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

G ¼ good, M ¼ moderate, P ¼ poorTables 1e4

5 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 nan-nofossils 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 109specimens/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 pre-served nannofossil assemblages in the interval 0.77 m, whereas samples with good preservation show high abundances between 2 and 4 109 specimens/g sediment in the rest interval of NP9b Calcareous nannofossils in the interval of NP10a have abundances

of 1e2 109specimens/g sediment

Diversity varies throughout the investigated interval from 11 to

36 species/sample In the NP9a interval a diversity of 21e25 spe-cies/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., Campylos-phaera dela, Chiasmolithus spp., Discoaster spp., Rhomboaster spp., Tribrachiatus spp., Sphenolithus spp.) make the bulk of the

calcar-eous nannofossil abundance (Fig 3) These 9 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

in-terval 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%); Fas-ciculithus spp (1.1e17.7%) with abrupt decrease in the basal part of

(0.8e7.6%); Rhomboaster spp (1e27.6%) and Campylosphaera dela/ eodela (0.3e4.3%).Fig 3

5.2 Gebel Araas section

In the interval of the NP9a the calcareous nannofossil absolute abundance is relatively low range from 0.4 to 1 109specimens/g

occur in the interval of NP9b Calcareous nannofossils in the

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

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diversity of 24e29 species/sample has been recorded In the

in-terval of NP9b diversity ranges from 25 to 32 species The upper

part of the studied interval (NP10a) is characterized by high

di-versity 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

consti-tute 20.6e49.9% in the interval of NP9b and 25e49.6% in the

in-terval 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

com-mon genera in the studied interval of Araas section include

Neochiastozygus spp (0.3e3.2%)Fig 4

5.3 Gebel Qeryia

Nannofossil abundance in Qeryia section is consistently

mod-erate to high ranges from 0.002-1x 109specimens/g sediment in

the lower most intervals 0e0.25 m (NP9a) The abundance

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 1 to 2 109specimens/g sediment Di-versity is moderate to high varies from 25 to 29 species in the NP9a interval The diversity ranges from 9 to 31 through the NP9b in-terval 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

abun-dant 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% Dis-coaster 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

Fig 1 Location map, 1 ¼ Taramsa section, 2 ¼ Araas section, 3 ¼ Qeryia section, 4 ¼ Duwi section.

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from 1.1 to 3.2% Fasciculithus comprises 4.7e8.6% in the NP9a

in-terval and increases in the NP9b ranges from 0.8 to 11.3%

Fas-ciculithus 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 1 to 4 109specimen/g

sedi-ment The abundance decrease in the interval around the P/E

upper part of NP9b subzone absolute abundance increases to

4 109specimen/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%),

(0.8e4.8%) (Fig 6)

6 Biostratigraphy The calcareous nannofossil biostratigraphy of the lower Paleo-gene 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 1 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

ofMartini (1971).Fig 7

6.1 Discoaster multiradiatus zone (NP9) This zone spans the interval from the ﬁrst occurrence of D.

Fig 2 Lithostratigraphic units of the PaleoceneeEocene succession exposed at studied sections.

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multiradiatus to the FO of Tribrachiatus bramlettei and has an

esti-mated duration of 1.2 my (Berggern et al., 1995) The studied part of

Zone NP9 attains 1.45 m, 2.70 m, 1 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 1 DQB) and

marked by a notable decrease, or absence, of calcareous

nanno-fossils 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 toBukry (1973), Campylosphaera eodela has its ﬁrst occurrence within

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

1 of DQB) together with the FO of D araneus and the ﬁrst

Table 1

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.

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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

de-creases 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

Table 2

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.

Sample number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

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boundary ofOkada 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 ofMartini (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

7 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

di-versity 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

Table 3

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.

Sample number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Coccolithus pelagicus 1 147 162 173 3 140 146 320 299 158 144 180 168 218 211 114 89 140 97

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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

Fas-ciculithus 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,

Fas-ciculithus alanii, FasFas-ciculithus hayi, FasFas-ciculithus bobii, FasFas-ciculithus

schaubii, and Fasciculithus richardii and continuous occurrence of

Fasciculithus tympaniformis The diversity and abundance of

Fas-ciculithus 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

0 and 4 species The Fasciculithus extinction occurs in the lower-most 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, Fas-ciculithus alanii and FasFas-ciculithus 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 ob-servations were recorded in the Qreiya, Duwi and Owaina sections

Table 4

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 9

Sample number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

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(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 dur-ing 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),

Fig 3 Absolute abundance, diversity and relative abundance of selected nannofossil species in Taramsa section.

Fig 4 Absolute abundance, diversity and relative abundance of selected nannofossil species Araas section.

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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

NP9-NP10 with rapid increase in diversity towards the PETM, and

appearance of new species (i.e Discoaster binodosus, lenticularis,

Discoaster falcatus, Discoaster limbatus, Discoaster mediosus,

Dis-coaster araneus, DisDis-coaster 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 1 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

recorded in the studied sections The ﬂoral assemblage after the PETM characterized by sudden appearance and rapid increase of

Fig 5 Absolute abundance, diversity and relative abundance of selected nannofossil species in Qreiya section.

Fig 6 Absolute abundance, diversity and relative abundance of selected nannofossil species in Duwi section.

Tiêu đề	Calcareous Nannofossils and Paleoenvironments of the Paleocene-Eocene Thermal Maximum (PETM) Interval in Central Egypt
Tác giả	Mohamed Youssef
Trường học	King Saud University
Chuyên ngành	Geology and Paleontology
Thể loại	Research Article
Năm xuất bản	2016
Thành phố	Cairo

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Số trang	17
Dung lượng	1,86 MB