Palaeoenvironmental turnover across the Palaeocene/Eocene boundary at the Stratotype section in...

Palaeoenvironmental turnover across the Palaeocene/Eoceneboundary at the Stratotype section in Dababiya (Egypt) based onbenthic foraminifera

Laia Alegret,1,2 Silvia Ortiz,2 Ignacio Arenillas2 and Eustoquio Molina21Department of Earth Sciences, University College London, WC1E 6BT London, UK; 2Departamento de Ciencias de la Tierra, Universidad de

Zaragoza, 50009 Zaragoza, Spain

Introduction

The Palaeocene/Eocene (P/E) bound-ary interval is marked by a negativeshift in d13C values [commonly knownas the carbon isotope excursion (CIE)]in carbonates in marine and contin-ental sections. During this interval,one of the most abrupt global warm-ing events in the Cenozoic occurred(Zachos et al., 2001). A major faunalturnover, including a major extinctionof deep-sea benthic foraminifera (e.g.Thomas, 1990, 2003), an acme of thetropical–subtropical planktic for-aminiferal genus Acarinina (e.g. Are-nillas and Molina, 1996; Kelly et al.,1998), distinctive assemblages of cal-careous nannoplankton (Aubry, 1995;Bralower, 2002), an acme of the dino-flagellate Apectodinium at middle andhigh latitudes (Crouch et al., 2001),and the rapid radiation of mammalson land (Koch et al., 1992), occurredduring this warm period, which hasbeen called the initial Eocene thermalmaximum (IETM) or the Palaeocene–Eocene thermal maximum (PETM).Although the ultimate cause of theCIE is not well known, the dissoci-ation of methane hydrates along thecontinental margins is a plausible

hypothesis to account for the injectionof 13C-depleted carbon into the atmo-spheric and oceanic reservoirs (Dick-ens et al., 1997). Deep-sea benthicforaminifera suffered major extinctionat the time of the shift in d13C valuesin bulk carbonates, benthic and plank-tic foraminifera (Thomas, 2003),whereas benthic foraminifera frommarginal and epicontinental basinsshow lesser extinction or temporaryassemblage changes. Along the south-ern margin of Tethys (Egypt, Israel),the upwelling of low-oxygen interme-diate water into the epicontinentalbasin led to increased biological pro-ductivity and anoxia at the sea floorbefore and during the IETM (Speijerand Schmitz, 1998; Speijer et al., 2000;Speijer and Wagner, 2002). Low oxy-gen conditions during the IETM havealso been documented in the north-eastern Peri-Tethys (Gavrilov et al.,2003).The Global Stratotype Section and

Point (GSSP) for the P/E boundarywas defined at the Dababiya Quarry,in Egypt (Dupuis et al., 2003). Duringthe late Palaeocene and early Eocenethis part of the Tethys was occupiedby an epicontinental basin, deepeningin a NNW direction from neritic touppermost abyssal (Said, 1990; Speijeret al., 2000). The lithology, mineral-ogy, carbon isotope stratigraphy, andplanktic foraminiferal biostratigraphyof the Dababiya section were des-cribed by Dupuis et al. (2003) and

Berggren and Ouda (2003), but thebenthic foraminifera have not beendescribed in detail. We carried out thefirst detailed analysis of benthic for-aminiferal assemblages across thePalaeocene–EocenetransitionatDaba-biya, in order to infer the palaeoenvi-ronmental turnover, to document theextinction of benthic foraminifera inthe type section, and to correlate thebenthic foraminiferal turnover in thatsection to the extinction of benthicforaminifera in the deep sea.

Materials and methods

The GSSP of the P/E boundary is ineastern Egypt, and occurs in the EsnaShale Formation in Dababiya Quarry,35 km south of Luxor (Dupuis et al.,2003). The 130-m-thick Esna Forma-tion consists of monotonous grey tobrown-green marls and shales withabundant and generally well-pre-served microfossils. The GSSP is inthe lower part of the Esna Formation,at the contact between the marly Esna1 and Esna 2 Units. The latter unitcontains a succession of five beds thatwere formally described and named�Dababiya Quarry Beds 1–5� (Dupuiset al., 2003). The CIE (as recognizedin bulk organic matter) occurs withinthe Dababiya Quarry Beds (DQBeds),which contain phosphatic dissolutionlevels in which calcareous foramini-fera are almost absent (Figs 1 and 2).The P/E boundary has been placed at

ABSTRACT

The Global Stratotype Section and Point for the Palaeocene/Eocene (P/E) boundary was defined at Dababiya Quarry (Egypt)at the base of the carbon isotope excursion (CIE). We presentthe first detailed analysis of Palaeocene–Eocene benthic for-aminifera from Dababiya, in order to infer the palaeoenviron-mental turnover across the P/E boundary. At Dababiya, the CIEcoincides with a major turnover in foraminiferal assemblages;the last occurrence of Angulogavelinella avnimelechi, at the baseof the CIE, may be correlated to the main phase of extinction of

deep-sea benthic foraminifera. Benthic foraminifera indicatethat stressful conditions such as oxygen deficiency, carbonatedissolution, and changes in food supply, persisted at the seafloor over most of the CIE interval. The main phase of recoveryof benthic foraminifera is recorded c. 250 cm above the P/Eboundary, and it may be linked to increased productivity andoxygenation at the sea floor.

Terra Nova, 17, 526–536, 2005

Correspondence: Dr Laia Alegret, Depart-

ment of Earth Sciences, University College

London, London WC1E 6BT, UK. Tel.:

020 7679 3344; fax: 020 7679 4166; e-mail:

[email protected]

526 � 2005 Blackwell Publishing Ltd

doi: 10.1111/j.1365-3121.2005.00645.x

the base of the CIE, at the contactbetween the marly Esna 1 Unit andthe dark, laminated non-calcareousclayey DQB 1 (Dupuis et al., 2003).We studied 32 samples from the

upper 1.57 m of Unit Esna 1 (Palaeo-cene) and the lower 7.5 m of UnitEsna 2 (Eocene) in subsection (DBH)where the GSSP was formally defined.The DBH subsection spans the middlepart of the planktic foraminiferalMorozovella velascoensis Zone (ZoneP5).In order to avoid the loss of small

taxa, quantitative studies were basedon representative splits of about 300specimens of benthic foraminifera lar-ger than 63 lm (Table 1). Benthic for-aminiferal morphotype analysis(Table 2), and changes in the abun-

dance of selected taxa and in genusrichness allowed us to infer probablemicrohabitat preferences and environ-mental parameters (e.g. Bernhard,1986; Jorissen et al., 1995). The Fish-er-a diversity index and the H(S) Shan-non–Weaver information functionwere calculated in order to documentpossible changes in diversity (Murray,1991).

Palaeobathymetry

Benthic foraminiferal assemblagescontain abundant representatives ofthe Midway-type fauna (Berggren andAubert, 1975), such as Angulogaveli-nella avnimelechi, Bulimina midwayen-sis, Cibicidoides cf. alleni, Cibicidoidessuccedens, Loxostomoides applinae,

Osangularia plummerae and Siphogen-erinoides eleganta (Fig. 1), as well asother taxa that were common at c.150–200 m depth (e.g. Bulimina cal-lahani, Bulimina farafraensis, Cibici-doides pharaonis, Cibicidoidespseudoperlucidus, Lenticulina spp.,Oridorsalis plummerae, Spiroplectinel-la esnaensis, Valvulineria scrobiculata;Speijer and Schmitz, 1998). Theupper-depth limit of species such asBulimina midwayensis, Cibicidoides cf.alleni and Osangularia plummerae, islocated at middle sublitoral depths(50–100 m; Van Morkhoven et al.,1986). These data suggest that upperPalaeocene and lower Eocene sedi-ments from Dababiya were depositedin an outer shelf environment (c. 150–200 m depth), in agreement with Spei-

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Fig. 1 Benthic foraminiferal turnover across the Palaeocene/Eocene boundary at Dababiya section. The dashed areas in the lowerEocene correspond to the levels with abundant pyritized foraminifera. Species that make up 4–9% of the assemblages in at leastone sample have been considered as �common taxa�. A. berg. ¼ A. berggreni Subzone.

Terra Nova, Vol 17, No. 6, 526–536 L. Alegret et al. • Palaeoenvironmental turnover across the Palaeocene/Eocene boundary

.............................................................................................................................................................

� 2005 Blackwell Publishing Ltd 527

jer et al. (2000) and Speijer and Wag-ner (2002).

Foraminiferal assemblages

Upper Palaeocene benthic foraminife-ral assemblages from Dababiya(uppermost 1.57 m of Unit Esna 1)are diverse and heterogeneous(Fig. 2). Agglutinated foraminiferaare minor components of the assem-blages (20–47%). Among calcareoustaxa, Anomalinoides praeacutus,Cibicidoides pseudoacutus, Cibicido-ides pseudoperlucidus, laevidentalinids,Lenticulina and Neobulimina faraf-raensis are most abundant (Fig. 1).Assemblages consist of a mixture ofinfaunal (39–62%) and epifaunal mor-phogroups. Planktic foraminiferalassemblages from the Morozovellagracilis Subzones are diverse and richin tropical–subtropical species.

The last occurrences of Angulogav-elinella avnimelechi, Anomalinoidesaegyptiacus and Neobulimina faraf-raensis occurred at the P/E boundary.The agglutinated trochamminids,Karrerulina, Haplophragmoides andRecurvoides increased in abundance,while the percentage of infaunal mor-phogroups, the genus richness, diver-sity and heterogeneity of theassemblages decreased at the base ofthe CIE-interval (base of DQB 1;Fig. 2). The relative abundance oftrochamminids increased within thisbed up to 85%. Planktic foraminiferaare rare, and their assemblages have alow diversity.Samples from the upper part of

DQB 1, DQB 2 and lower half ofDQB 3 are almost barren of benthicforaminifera, whereas planktic fo-raminifera are common in the upperpart of DQB 2 and in the lowermost

part of DQB 3 (sample 2.5), where apeak in the abundance of the genusAcarinina has been identified (Fig. 2).Very few, probably reworked benthicforaminifera were found in DQB 2and in most part of DQB 3, so that wecould not make palaeoenvironmentalinferences based on this group.Samples from the upper half of DQB

3 and the lower half of DQB 4 containmore common benthic foraminifera.Assemblages are dominated by agglu-tinated taxa, mainly trochamminidsand Karrerulina spp., but the calcar-eous taxa Lenticulina spp., Anomalino-ides spp. and Hemirobulina spp. arealso common. Diversity indices remainvery low (Fig. 2). Acarininids domin-ate the planktic foraminiferal assem-blages.The abundance of benthic foramini-

fera, the percentage of infaunal mor-phogroups, the genus richness,

Fig. 2 Benthic foraminiferal indices, d13C values (Dupuis et al., 2003) and percentages of the planktic foraminifera Acarinina andMorozovella across the Palaeocene/Eocene boundary at Dababiya section. A. b. ¼ A. berggreni Subzone; CIE ¼ carbon isotopeexcursion; IETM ¼ initial Eocene thermal maximum.

Palaeoenvironmental turnover across the Palaeocene/Eocene boundary • L. Alegret et al. Terra Nova, Vol 17, No. 6, 526–536

.............................................................................................................................................................


Table 1a Benthic foraminiferal species counts in upper Palaeocene samples from Dababiya. For considerations on relative

abundance of branching foraminifera (e.g. Bathysiphon, Rhizammina), we divided the number of pieces by 4, considering that on

average about four pieces are representative of one specimen.

DBH 0 DBH 0.25 DBH 0.5 DBH 0.75 DBH 1 DBH 1.25 DBH 1.35 DBH 1.40 DBH 1.43 DBH 1.45 DBH 1.5 DBH 1.515

Ammobaculites sp. 1 1 1 1

Ammodiscus spp. 3 4 6 2 2 4 3 1 3

Ammomarginulina sp. 2

Bathysiphon spp. 12 6 4 8 3 5 4 32 4 1 9

Clavulinoides spp. 1

Glomospirella spp. 2 2 1 2

Haplophragmoides spp. 24 23 21 27 15 12 15 21 3 4 5 9

Hyperammina sp. 1

Karrerulina horrida 4

Karrerulina spp. 5 3 4 2 1 2 4 18 23 105 2

Marssonella oxycona 1

Psammosphaera sp. 3

Recurvoides spp. 14 28 10 49 12 3 6 38 9 8 6

Repmanina charoides 2 3 1 2 1 3

Rhizammina spp. 3 3 2 5 1 2 3 5 3

Saccammina sp. 2 2 4 8 2 3 1

Spiroplectammina spp. 1 1 1 3 4 2

Spiroplectammina spectabilis 3 1 2 1

Spiroplectinella esnaensis 1 1

Subreophax sp. 2 1 1

Textularia spp. 2 2 2

Trochamminids 15 42 26 39 23 20 22 38 17 5 95 26

Alabamina wilcoxensis 7 5 3 3 1 1 1 2

Angulogavelinella avnimelechi 5 7 3 20 17 7 2

Anomalinoides praeacutus 1 3 31 3 12 5 6 5 2

Anomalinoides aegyptiacus 3 5 17 5 15 8 9 2 14

Anomalinoides ammonoides 1 5 1 2 2 5 2 1

Anomalinoides midwayensis 2

Anomalinoides rubiginosus 2 4 3 2 5

Anomalinoides zitteli 1 3 1 1 1

Anomalinoides spp. 2 6 2 4 6 2 1 4

Astacolus spp. 2 3 2 3

Bulimina spp. 1 1 2

Bulimina midwayensis 1 2 2 3 2 2 1

Bulimina cf. velascoensis 1

Cibicidoides cf. hyphalus 1

Cibicidoides cf. alleni 2 5 13 5 3 5

Cibicidoides cf. dayi 1

Cibicidoides pharaonis 2 3 1 3 3 4 1

Cibicidoides pseudoacutus 1 9 7 2 7 16 10 20 18

Cibicidoides pseudoperlucidus 13 13 16 3 22 29 27 1 8 10

Cibicidoides proprius 7 2 4 3 3 4

Cibicidoides sp. A 1 1 2 1 2

Cibicidoides spp. 9 3 1 1 8 8 10 5 9 14

Coryphostoma spp. 1

Coryphostoma cf. midwayensis 1

Coryphostoma cf. incrassata 1

Glandulina spp. 1 2 2 1

Globobulimina spp. 1 1

Globocassidulina subglobosa 11 2 8 9 1 8 7

Guttulina spp. 1 1 1

Globorotalites sp. 1

Gyroidinoides beisseli 1 20 8 4 4 14 13 6 5

Gyroidinoides depressus 7 8 1 1 4 2 1 3 1

Gyroidinoides globosus 1 1 1 1 1

Gyroidinoides girardanus 2 1 1 1

Gyroidinoides spp. 1 13 2 1 1 3 4 1 3

Laevidentalina spp. 11 12 8 5 10 15 18 4 4 21

Lagena spp. 2 3 5 6 1 2


.............................................................................................................................................................


diversity and heterogeneity of theassemblages increase towards theupper part of the CIE interval (upperpart of DQB4 and DQB5; Fig. 2),where assemblages are dominated bycalcareous foraminifera (87–95%),mainly by Lenticulina spp.The local first occurrence of several

species is recorded in the upper part ofthe CIE-interval (Fig. 1). Samplesfrom the upper part of DQB 4towards the top of the section containup to 28–38% of buliminids (e.g.Bulimina midwayensis, B. farafraensis,B. callahani, Loxostomoides applinae,Stainforthia spp.) and Lenticulinaspp., as well as other calcareous taxathat are common to abundant. Genusrichness, diversity and heterogeneityof the assemblages increase in thisinterval, but they do not reach the pre-CIE values (Fig. 2).Above the DQBeds, four levels

(samples 5.5, 6.5, 7.5 and 8.5) are richin pyritized foraminifera, and containabundant agglutinated taxa (e.g.Haplophragmoides, trochamminids)and abundant buliminids (Buliminakugleri, Fursenkoina spp. and Globob-ulimina spp.).

Palaeoenvironmental inferences

Upper Palaeocene

Benthic foraminiferal assemblages arediverse and consist of mixed infaunaland epifaunal morphogroups, suggest-ing intermediate trophic levels duringthe latest Palaeocene at Dababiya.They contain abundant specimenswith large and heavily calcified tests,such as Cibicidoides pseudoacutus andCibicidoides pseudoperlucidus, indica-ting that oxygen levels were high, andthat oxygen deficiency at the sea floorprior to the IETM was confined to theshallowest (middle shelf) part of thebasin in the Upper Nile Valley (Speijerand Wagner, 2002; Ouda and Berg-gren, 2003).

CIE interval (lowermost Eocene)

Dupuis et al. (2003) reported the pres-ence of Angulogavelinella avnimelechiwithin the CIE-interval (up to sampleDBH 3.4), but they suggested thatthese specimens are reworked, andthat the extinction of A. avnimelechioccurred at the base of the CIE-

interval, as in other neritic sectionsin this part of the Tethys (e.g. Speijeret al., 1995). Therefore, the extinctionof A. avnimelechi was coeval with themain phase of extinction of deep-seabenthic foraminifera, and the extinc-tion of Stensioeina beccariiformis(Thomas, 1998).Some of the species whose last

occurrence coincides with the P/Eboundary in the nearby Gebel Aweinasection, such as Anomalinoides mid-wayensis (Speijer and Schmitz, 1998),also occur as rare, poorly preserved,probably reworked specimens withinthe DQBeds.In the lowermost part of the CIE

(lower part of DQB 1), the acme ofagglutinated foraminifera and theabsence of planktic foraminifera mayhave been caused by intense dissolu-tion, which has been observed tooccur at the beginning of the CIE-interval across the world (Ortiz, 1995;Thomas and Shackleton, 1996; Tho-mas, 1998). The absence of calcareousforaminifera not only at Dababiya butalso at the nearby Qreiya section(Ouda and Berggren, 2003) may berelated to the release of methane and

Table 1a Continued

DBH 0 DBH 0.25 DBH 0.5 DBH 0.75 DBH 1 DBH 1.25 DBH 1.35 DBH 1.40 DBH 1.43 DBH 1.45 DBH 1.5 DBH 1.515

Lenticulina spp. 12 7 15 15 16 20 18 7 13 29

Loxostomoides applinae 6 10 10 22 18 18 19 7 5

Neoflabellina sp. 1

Nuttallides sp. 1

Nuttallinella spp. 3 1 2

Oolina spp. 1 1 2 1

Oridorsalis plummerae 5 4 7 5 7 6

Oridorsalis umbonatus 2 1 8 3

Oridorsalis sp. 4 1 2 1 2

Osangularia spp. 1

Praebulimina sp. 1 1 1

Praebulimina cf. reussi 4 1

Neobulimina farafraensis 8 9 4 31 2 3

Praeglobobulimina sp. 1 1

Praeglobobulimina quadrata 1

Pullenia jarvisi 2 1 1 3

Nonion havanense 1 1 5 2 2

Ramulina globulifera 1 1 2

Rotamorphina cushmani 1 2 1

Saracenaria sp. 1 1 1

Siphogenerinoides sp. 1 1

Siphogenerinoides cf. eleganta 3 3

Stensioeina beccariiformis 1 1

Stillostomella sp. 5 2 1 4 1 2 4 1 3

Valvalabamina lenticula 6 3 6 1 3 3 2 3 3

Valvulineria scrobiculata 3 10 8 4 5 4 5 1

Total 231 278 289 294 244 259 284 167 183 41 206 230


.............................................................................................................................................................


Table

1b

Benthicforaminiferalspeciescountsin

lower

Eocenesamplesfrom

Dababiya.PYR

¼Pyritizedtests.Forconsiderationsonrelativeabundance

ofbranchingforaminifera

(e.g.,Bathysiphon,Rhizammina),wedivided

thenumber

ofpiecesby4,consideringthatonaverageaboutfourpiecesare

representativeofonespecim

en.

DBH1.59DBH1.75DBH2DBH2.5

DBH3.25DBH3.5

DBH3.75DBH4DBH4.25DBH4.5

DBH4.75DBH5DBH5.5

DBH6DBH6.5

DBH7DBH7.5

DBH8DBH8.5

DBH9

Ammod

iscu

sspp.

2

Bathysipho

nspp.

14

21

25

141

85

31

102

10

Bathysipho

nspp.

PYR

34

36

Boliv

inop

sissp.

2

Clav

ulinoide

sspp.

73

11

Gau

dryina

cf.ellisorae

2910

13

13

Gau

dryina

sp.A

327

1210

21

Gau

dryina

sp.juvenile

215

1010

2

Gau

dryina

spp.

113

2412

1

Glomospirella

spp.

14

1

Hap

loph

ragm

oide

sspp.

62

21

31

Karrerulin

aspp.

1058

4620

1

Psam

mosph

aera

sp.

14

Pseu

doclav

ulinasp.

3

Recu

rvoide

sspp.

54

63

21

2711

9

Repm

aninach

aroide

s1

3

Repm

aninach

aroide

sPYR

2

Rhizam

minaspp.

21

2

Sigm

oilopsissp.

11

Spirop

lectam

minaspp.

2

Spirop

lectinella

esna

ensis

12

17

310

21

91

110

Subreo

phax

sp.

11

1

Trochamminids

40340

265

3628

243

225

42

3026

112

1311

3988

6

TrochamminidsPYR

31

1814

1729

52

Vulvu

linamex

ican

a3

12

95

183

Alaba

minawilc

oxen

sis

17

913

2

Ano

malinoide

sacutus

31

1

Ano

malinoide

sprae

acutus

510

45

126

152

7

Ano

malinoide

sam

mon

oide

s2

12

11

Ano

malinoide

smidway

ensis

1

Ano

malinoide

srubigino

sus

21

1

Ano

malinoide

ssp.A

86

21

34

Ano

malinoide

ssp.B

5517

1

Ano

malinoide

szitteli

15

444

3729

3138

924

536

Ano

malinoide

sspp.

22

31

1

Astacolus

spp.

13

Band

yella

sp.

1

Bulim

inaspp.

123

Bulim

inacalla

hani

27

24

115

14

Bulim

inafarafrae

nsis

61

141

22

Bulim

inaku

gleriPYR

521

86

19

Bulim

inamidway

ensis

15

33

43

45


.............................................................................................................................................................


Table

1b

Continued


DBH3.25DBH3.5


DBH4.75DBH5DBH5.5

DBH6DBH6.5

DBH7DBH7.5

DBH8DBH8.5

DBH9

Bulim

inatuxp

amen

sis

1

Cibicido

ides

deco

ratus

11

Cibicido

ides

pharao

nis

1125

1016

122

123

323

Cibicido

ides

pseu

doacutus

32

12

Cibicido

ides

pseu

dope

rluc

idus

11

21

24

2

Cibicido

ides

prop

rius

11

21

61

1

Cibicido

ides

sp.A

67

83

1

Cibicido

ides

spp.

11

11

61

24

53

34

3

Cibicido

ides

succed

ens

114

411

75

21

Coryph

ostomaspp.

11

Chilo

stom

ellasp.

21

Fursen

koinaspp.

613

161

32

Gland

ulinaspp.

3

Globo

bulim

inaspp.

22

24

36

403

Globo

cassidulinasubg

lobo

sa2

21

12

1

Guttulin

aspp.

11

11

Gyroidino

ides

beisseli

11

12

44

23

2

Gyroidino

ides

depressus

52

52

1

Gyroidino

ides

girardan

us2

Gyroidino

ides

spp.

21

23

Laev

iden

talin

aco

lei

85

88

132

10

Laev

iden

talin

aspp.

21

1

Lage

naspp.

31

12

51

Lenticulinaspp.

1132

9483

97104

9460

6311

108

1871

1494

Lenticulinaspp.

PYR

13

Loxo

stom

oide

sap

plinae

13

26

134

131

154

91

3

Loxo

stom

oide

sap

plinae

PYR

33

7

Hem

irob

ulinapa

chyg

aster

11

Hem

irob

ulinasp.

63

41

1

Nod

osaria

long

iscata

12

43

35

119

63

111

Nodosariids

22

116

54

75

23

Non

ione

llaspp.

13

38

Orido

rsalis

plum

merae

1320

67

241

613

817

Orido

rsalis

umbo

natus

12

32

1324

27

7

Orido

rsalissp.

2

Osang

ularia

plum

merae

11

45

1224

816

29

Osang

ularia

spp.

1

Pleu

rostom

ella

sp.

11

Prae

bulim

inasp.

1

Prae

glob

obulim

inaqu

adrata

13

Pulle

niajarvisi

1

Pyramidulinalatejuga

ta-pau

percula

14

13

25

11

4

Pyramidulinasemispino

sa2

32

3



.............................................................................................................................................................

the increase in its oxidation productCO2, reacting to HCO�

3 and thuscausing strong CaCO3 dissolutionduring the early stage of warming(Dickens et al., 1997; Thomas, 1998).The occurrence of severe dissolutionat such shallow depths, however, isnot expected by carbon cycle model-ling (e.g. Dickens et al., 1997; Zachoset al., in press).The composition of the assemblages

from the lower part of DQB 1 indicatesa period of environmental stress: theabundance of trochamminids, Haplo-phragmoides and Recurvoides may beinterpreted as an acme of taxa thattolerate low oxygen conditions as wellas changes in the food supply (Sliter,1975; Koutsoukos et al., 1991; Ly andKuhnt, 1994; Kuhnt et al., 1996; Goo-day, 2003). Opportunistic species ofHaplophragmoides also peak in relativeabundance in an interval with strongdissolution above the Palaeocene–Eo-cene extinction of benthic foraminiferain Spanish bathyal sections (Ortiz,1995; Orue-Etxebarria et al., 1996).The presence of dark laminated shalessuggests oxygen deficiency during theearly phase of the CIE. The strongdecrease in the percentage of infaunalmorphogroups might indicate oligo-trophic conditions during this interval.We do not interpret the peak in agglu-tinated foraminifera as an indicator ofsea-level fluctuations, but as a result ofstressful conditions such as oxygendeficiency, carbonate dissolution, andchanges in the food supply.Higher in the section, the high

percentages of acarininids (>95% ofthe planktic foraminiferal assem-blages) and the near lack of othertropical–subtropical planktic fo-raminifera (e.g. large morozovellids)in DQB 2 (Fig. 2) suggest that theeffects of the thermal maximum andthe carbonate dissolution were notoverwhelming during deposition ofDQB 2, but may have returned duringdeposition of DQB 3.The composition of benthic for-

aminiferal assemblages in the upperhalf of DQB 3 and the lower half ofDQB 4, together with the high per-centage of acarininids suggest oceanicenvironmental stress, probably relatedto low oxygen conditions, high tem-perature, moderate carbonate dissolu-tion and high productivity in this area.We suggest that the IETM level inDababiya mainly includes the firstTa

ble

1b

Continued


DBH3.25DBH3.5


DBH4.75DBH5DBH5.5

DBH6DBH6.5

DBH7DBH7.5

DBH8DBH8.5

DBH9

Pyramidulinasp.FLeRoy

1953

31

36

22

Rotamorph

inacu

shman

i1

Siph

ogen

erinoide

ssp.

1

Siph

ogen

erinoide

scf.eleg

anta

21

32

43

32

14

Siph

onod

osaria

annu

lifera

915

127

24

11

Stainforhiasp.1Speijer1994

24

2

Stillostomella

alex

ande

ri1

11

1

Tapp

aninaselm

ensis

11

Trifarinaesna

ensis

32

Turrilina

brev

ispira

11

11

3

Uvige

rina

spp.

11

1

Valva

laba

minalenticula

11

21

Valvu

lineria

scrobicu

lata

315

2020

117

114

310

89

622

Valvu

lineriacf.scrobicu

lata

45

11

2

Total

73402

319

460

57310

343

320

389

337

418

138

321

250

344

118

207

281

394



.............................................................................................................................................................

250 cm above the P/E boundary, i.e.DQB 1, 2, 3, and the lower half ofDQB 4 (Fig. 2).

Upper part of the CIE interval andabove the DQBeds (lower Eocene)

Indicators of a high food flux and/orlow oxygenation at the sea floor, suchas buliminids and Lenticulina spp.,make up 28–38% of the assemblagesfrom DQB 4 towards the top of thesection. Buliminids in the presentoceans tolerate reduced oxygen con-centrations, but their high relativeabundance is thought to be mainlycaused by an abundant food supply,not by low oxygenation (Fontanieret al., 2002; Gooday, 2003; Alegretand Thomas, 2004). Moreover, theincreased percentages of infaunalmorphogroups indicate an increase inthe nutrient flux to the sea floor. Wethus infer moderate to high produc-tivity rather than low oxygen levels inthe sea bottom waters from the upperpart of the CIE-interval (DQB 4)towards the top of the section.The four pyrite-rich levels above the

DQBeds contain low-diversity assem-blages with abundant agglutinatedtaxa (e.g. Haplophragmoides, troc-hamminids) and numerous high-foodindicators such as buliminids. Thesedata suggest that the moderate trophicconditions recorded from the upperpart of the CIE interval towards thetop of the section were occasionallyinterrupted by periods of high pro-ductivity and/or low oxygen condi-tions at the sea floor. Similar dysoxicand eutrophic conditions were docu-mented by Speijer and Schmitz (1998)in the nearby Gewel Aweina section(Egypt), and related to periods ofupwelling that persisted for at least1 Myr after the P/E boundary.

Conclusions

Benthic foraminifera from DababiyaQuarry (Egypt) indicate an outer shelfdepth of deposition during the latePalaeocene and early Eocene. Benthicforaminiferal assemblages exhibit amajor faunal turnover across theIETM that may be linked to carbon-ate dissolution, low dissolved oxygenlevels at the sea floor and a highorganic flux. The extinction of An-gulogavelinella avnimelechi, amongother species, occurs at the base ofthe CIE, and thus may be correlatedto the main phase of extinction ofbenthic foraminifera in the deep sea.Severe carbonate dissolution oc-

curred in the lowermost part of theCIE (DQB 1). In this interval there isan acme of agglutinated foraminifera,which suggests that there may havebeen a lack of oxygen as well aschanges in the food supply to the seafloor; the strong decrease in the per-centage of infaunal morphogroupssuggests oligotrophic conditions dur-ing the earliest phase of the CIE.Carbonate dissolution related to re-lease and oxidation of methane duringthe earliest phase of warming is aplausible hypothesis to account for thepresence of dissolution levels in thelowermost Eocene in Dababiya and inother sections across the world,although the very large depth rangeover which dissolution occurred isdifficult to explain (Dickens et al.,1997; Thomas, 1998; Zachos et al., inpress).Composition of the benthic fo-

raminiferal assemblages suggestsmoderate to high productivity andincreased levels of dissolved oxygentowards the upper part of the CIE andafterwards. The environmental andfaunal recovery was occasionallyinterrupted by periods of environmen-tal stress at the sea floor, as inferredfrom four levels located above theDQBeds.

Acknowledgements

We thank M.P. Aubry and Ch. Dupuis forsupplying part of the samples, and EllenThomas and two anonymous referees fortheir helpful comments, which were mater-ial in improving the manuscript. Thisresearch was funded by CGL2004-00738/BTE project of the Spanish Ministerio deCiencia y Tecnologıa. L. Alegret thanksthe Ministerio de Educacion, Cultura y

Table 2 Habitat preferences of the most

abundant calcareous (Corliss, 1985;

Corliss and Chen, 1988) and agglutin-

ated (Jones and Charnock, 1985) benthic

foraminiferal taxa at Dababiya.

Epifaunal calcareous

Rounded trochospiral

Anomalinoides rubiginosus1

Plano-convex trochospiral

Angulogavelinella avnimelechi

Anomalinoides sp. B

Anomalinoides zitteli

Cibicidoides pharaonis

Gyroidinoides girardanus1

Valvalabamina lenticula

Valvulineria scrobiculata2

Biconvex trochospiral

Anomalinoides aegyptiacus3

Anomalinoides midwayensis

Anomalinoides praeacutus

Cibicidoides cf. alleni

Cibicidoides pseudoacutus

Cibicidoides pseudoperlucidus

Cibicidoides succedens

Oridorsalis plummerae4

Osangularia plummerae

Epifaunal agglutinated

A: Tubular or branching

Bathysiphon5

Rhizammina

Irregular

Trochamminids6

Infaunal calcareous

Cylindrical tapered

Bulimina callahani

Bulimina farafraensis

Bulimina kugleri

Bulimina midwayensis

Fursenkoina spp.

Globobulimina spp.

Hemirobulina spp.

Laevidentalinids

Neobulimina farafraensis

Nodosariids

Siphogenerinoides eleganta

Siphonodosaria annulifera

Stainforthia spp.

Flattened tapered

Loxostomoides applinae

Spherical/globose

Globocassidulina subglobosa

Biconvex trochospiral:

Gyroidinoides beisseli7

Oridorsalis umbonatus8

Biconvex planispiral

Lenticulina spp.9,10

Infaunal agglutinated

C1: Elongate multilocular

Gaudryina spp.

Karrerulina spp.

Spiroplectinella esnaensis

Table 2 Continued

Flattened trochospiral:

Haplophragmoides11,12

Streptospiral

Recurvoides13

1Widmark and Malmgren (1992); 2Speijer and

Schmitz (1998); 3Speijer and Wagner (2002);4Widmark and Speijer (1997); 5Peryt et al. (1997);6Galeotti et al. (2004); 7Alegret et al. (2001);8Rathburn and Corliss (1994); 9Corliss (1991);10Thomas and Shackleton (1996); 11Kuhnt et al.

(1996); 12Kaminski et al. (1999); 13Kuhnt and

Kaminski (1993).



.............................................................................................................................................................

Deporte for the postdoctoral grant EX2003-0007. S. Ortiz thanks the Spanish Comuni-dad de la Rioja for the predoctoral grant.

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Received 1 September 2004; revised versionaccepted 23 June 2005



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