Paleoecology of the Cretaceous–Tertiary mass extinction in planktonic foraminifera

Paleoecology of the Cretaceous^Tertiary mass extinction inplanktonic foraminifera

Gerta Keller a;�, Thierry Adatte b, W. Stinnesbeck c, Valeria Luciani d,Narjess Karoui-Yaakoub e, Dalila Zaghbib-Turki e

a Geosciences Department, Princeton University, Princeton, NJ 08544, USAb Institut de Ge¤ologie, 11 Rue Emile Argand, 2007 Neucha“tel, Switzerlandc Geologisches Institut, Universita«t Karlsruhe, 76128 Karlsruhe, Germany

d Dipartimento di Scienze Geologiche e Paleontologiche dell’Universita' degli Studi di Ferrara, 4410 Ferrara, Italye Faculte¤ des Sciences de Tunis, De¤partement de Ge¤ologie, Campus Universitaire, l060 Tunis, Tunisia

Received 10 July 1999; accepted 9 August 2001

Abstract

Paleobiogeographic patterns of the Cretaceous^Tertiary (K^T) mass extinction in planktonic foraminifera inTunisia, spanning environments from open marine upper bathyal, to shelf and shallow marginal settings, indicate asurprisingly selective and environmentally mediated mass extinction. This selectivity is apparent in all of theenvironmental proxies used to evaluate the mass extinction, including species richness, ecological generalists,ecological specialists, surface and subsurface dwellers, whether based on the number of species or the relative percentabundances of species. The following conclusions can be reached for shallow to deep environments: about threequarters of the species disappeared at or near the K^T boundary and only ecological generalists able to tolerate widevariations in temperature, nutrients, salinity and oxygen survived. Among the ecological generalists (heterohelicids,guembelitrids, hedbergellids and globigerinellids), only surface dwellers survived. Ecological generalists which largelyconsisted of two morphogroups of opportunistic biserial and triserial species also suffered selectively. Biserials thrivedduring the latest Maastrichtian in well stratified open marine settings and dramatically declined in relative abundancesin the early Danian. Triserials thrived only in shallow marginal marine environments, or similarly stressed ecosystems,during the latest Maastrichtian, but dominated both open marine and restricted marginal settings in the early Danian.This highly selective mass extinction pattern reflects dramatic changes in temperature, salinity, oxygen and nutrientsacross the K^T boundary in the low latitude Tethys ocean which appear to be the result of both long-termenvironmental changes (e.g., climate, sea level, volcanism) and short-term effects (bolide impact). ß 2002 ElsevierScience B.V. All rights reserved.

Keywords: Tunisia; paleoecology; K^T planktonic foraminifera

1. Introduction

The mass extinction in planktonic foraminiferaacross the Cretaceous^Tertiary (K^T) transition isone of the most severe biotic e¡ects generally at-

0031-0182 / 02 / $ ^ see front matter ß 2002 Elsevier Science B.V. All rights reserved.PII: S 0 0 3 1 - 0 1 8 2 ( 0 1 ) 0 0 3 9 9 - 6

* Corresponding author. Tel. : +1-609-258-4117;Fax: +1-609-258-1671.

E-mail address: [email protected] (G. Keller).

PALAEO 2758 1-5-02

Palaeogeography, Palaeoclimatology, Palaeoecology 178 (2002) 257^297

www.elsevier.com/locate/palaeo

tributed to a large extraterrestrial impact nearChicxulub on the Yucatan Peninsula, Mexico,though the end of the Cretaceous was also atime of extremely stressful environmental condi-tions for any living organism due to the culmina-tion of long-term climatic changes, such as theV6^7‡C cooling during the Maastrichtian fol-lowed by rapid warming of V3^4‡C between400 and 200 kyr before the K^T boundary andsubsequent cooling of V2^3‡C during the last100^200 kyr of the Maastrichtian (e.g., Barrera,1994; Li and Keller, 1998a,c). Few studies, how-ever, have addressed the biotic e¡ects that accom-panied these long-term environmental changesand the e¡ect this may have had in pre-disposinghigh stress assemblages to eventual extinction(e.g., Abramovich et al., 1998, 2002; Li and Kel-ler, 1998b,c; Kucera and Malmgren, 1998; Olssonet al., 2001).

Most K^T boundary studies on planktonic fo-raminifera have concentrated on documenting thepattern of species extinctions immediately belowand above the lithological change and geochemi-cal anomalies that mark the boundary event. Afew studies have attempted to evaluate some as-pects of this mass extinction event on a regionalor global scale, including hiatus distribution(MacLeod and Keller, 199l), species survivorship(MacLeod and Keller, 1994), pre-K^T species ex-tinctions in the Negev (Abramovich et al., 1998)and extinctions in northern Spain (Apellanize etal., 1997) and the northern Tethys (Pardo et al.,1999). The absence of more comphrehensive inte-grated summary results is largely because mostK^T sections are scattered far apart and directcomparisons are di⁄cult due to still unknown re-gional e¡ects.

Recent studies of several new K^T boundarysections in Tunisia now provide the opportunityto evaluate the mass extinction pattern in the lowlatitude Tethys region. The Tunisian sections,which include the El Kef stratotype, are knownto have the most continuous sediment accumula-tion records across the K^T boundary and gener-ally well preserved planktonic foraminiferal as-semblages. The Elles locality, about 75 kmsoutheast of El Kef, has an even more expandedK^T transition than the stratotype section and

di¡ers from the latter in the presence of an eventdeposit consisting of a 20 cm thick, cross-beddedforaminiferal packstone just below the K^Tboundary. Here we detail the K^T transition ofElles II, the most expanded of the Elles outcrops(see Elles I in Karoui-Yaakoub et al., 2002). Weconsider the faunal turnover in this section, aswell as that of El Kef, as representative of themass extinction in the open marine low latitudeTethys environment.

We then present a regional paleoecologicalevaluation of the mass extinction in Tunisia basedon ¢ve sections which span from the shallow Sa-hara Platform in the south to the open marineenvironment of the north (Fig. 1). The databaseconsists of the planktonic foraminiferal speciescensus and relative species abundances of thesesections and the analysis contrasts faunal assem-blages before and after the K^T boundary basedon two time slices, the latest Maastrichtian (upperCF1) and early Danian (P0 to lower P1a). Speci¢cparameters are evaluated and mapped, includingspecies richness, ecological generalists, ecological

Fig. 1. Paleogeography of Tunisia during the late Maastrich-tian and early Tertiary with paleolocations of the K^Tboundary sections (modi¢ed after Burollet, 1967).

PALAEO 2758 1-5-02

G. Keller et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 178 (2002) 257^297258

specialists, opportunists, and surface vs. subsur-face dwellers. This allows us to evaluate the biotice¡ects in assemblages ranging from shallow mar-ginal to open marine settings in the low latitudeTethys region.

1.1. Paleogeography of Tunisia

The paleogeographic and tectonic setting of Tu-nisian sections during the late Maastrichtian toearly Paleocene is shown in Fig. 1 (modi¢edfrom Burollet, 1967). The Seldja section was de-posited in the shallow water Gafsa Basin whichwas connected to the Sahara Platform to thesouth, but separated from the Tethyan realm tothe north by the Kasserine Island. Interchangewith the open sea was therefore restricted by theKasserine Island and probably also by small up-lifted areas to the east and west that acted asbarriers to circulation (Burollet, 1956; Burolletand Oudin, 1980; Sassi, 1974). Sediment deposi-tion occurred largely in restricted seas that £uctu-ated between inner neritic and coastal environ-ments. Tectonic activity and erosion of theKasserine Island contributed to a constant thoughvariable terrigenous in£ux of sediments (Adatte etal., 2002). Planktonic foraminiferal faunas pro-vide a rare glimpse of marine life in shallow

near-shore environments during the K^T transi-tion (Keller et al., 1998).

The El Kef, Elles and Ain Settara sections arelocated to the north of the Kasserine Island. Sedi-ment deposition occurred at upper bathyal to out-er neritic depths at El Kef and middle to outerneritic depths at Elles and Ain Settara, as indi-cated by benthic foraminifera (Galeotti and Coc-cioni, 2002, Fig. 2). All three sections indicatesimilar depositional environments in open marineconditions, but with variable terrigenous in£uxfrom the Kasserine Island (see Adatte et al.,2002). At Elles and Ain Settara, terrigenous in£uxis generally higher than at El Kef with episodes ofbioclastic or terrigenous transport just below andabove the K^T boundary. Elles and El Kef havecomparable sediment records, whereas Ain Set-tara has a condensed boundary clay and possiblya short hiatus (zone P0 is only a few centimetersthick; Luciani, 2002).

About 150 km to the north of El Kef is the ElMelah section which represents the northernmostof the Tunisian K^T boundary outcrops. Sedi-ment deposition occurred at a deeper upper bath-yal depth than at El Kef and terrigenous in£uxwas low (Adatte et al., 2002). As a result, sedi-ment accumulation is signi¢cantly lower than atEl Kef and Elles (Karoui-Yaakoub et al., 2002).

Fig. 2. Paleoenvironmental settings of ¢ve Tunisian K^T sections spanning from the restricted shallow Gafsa Basin Seldja sectionat the edge of the Sahara to the middle and outer shelf depths of the El Kef, Elles and Ain Settara sections just north of theKasserine Island and to the upper bathyal El Melah section to the north (see Fig. 1 for paleolocalities).

PALAEO 2758 1-5-02

G. Keller et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 178 (2002) 257^297 259

With the exception of Seldja where beds are tilted,sediment layers at the other four Tunisian K^Tboundary localities are essentially horizontal andwithout structural complexities. There is easy accessto the sections and foraminiferal preservation isvery good to excellent. Together these ¢ve sectionsprovide an ideal transect representing paleodeposi-tional environments from the shallow inner neritic,to middle and outer neritic, and upper slope envi-ronments (Fig. 2) that may be characteristic of thelow latitude Tethyan realm in general.

1.2. Previous work and database

A number of high resolution quantitativeplanktonic foraminiferal studies have recentlybeen completed for the Tunisian K^T sections,including El Kef (Keller et al., 1995; Molina etal., 1998), Ain Settara (Molina et al., 1998; Lu-ciani, 2002), Elles and El Melah (Karoui-Yaa-koub et al., 2002 and this study) and Seldja (Kel-ler et al., 1998, Fig. 1). Though these studies weredone independently by di¡erent workers, in allbut one (Molina et al., 1998) the same or similarspecies concepts and methods were used and thedatabase of these workers is thus internally con-sistent and forms the basis for the Tunisian pa-leobiogeography of the K^T mass extinction.

There are few taxonomic di¡erences betweenKeller and Luciani (see Luciani, 1997, 2002),and the di¡erences between Keller and Karoui-Yaakoub in the species census data are due tolumper and splitter e¡ects (see discussion in Ka-roui-Yaakoub et al., 2002). Therefore for the Ellessection, only the results of Keller’s analysis (thisstudy) are used, though both Elles outcrop local-ities show nearly identical species census and fau-nal assemblage changes. The quantitative data forthis report are based on Keller’s and Luciani’sstudies for all Tunisian sections.

1.3. Methods

Samples from all ¢ve Tunisian sections werecollected by the same team using the same meth-ods. The sections were cleaned from surface con-tamination by digging a trench to fresh bedrock.Samples were then taken at 5^10-cm intervals in

general, and at closer 1^2-cm intervals across theboundary clay layer. For each section, the samesample set was used for faunal, geochemical andmineralogical studies to insure direct comparisonof results (Adatte et al., 2002; Stu«ben et al., 2002).

Laboratory and analytical methods for plank-tonic foraminiferal studies have been described inKeller et al. (1995). Population counts were basedon sample splits of about 300 specimens fromeach of two size fractions (38^63 Wm and s 63Wm). Duplicate analyses of two size fractionswere done because there is a signi¢cant di¡erencebetween the ¢rst appearances of the earliest Dan-ian species in the two size fractions, with earlier¢rst occurrences in the small 6 63-Wm size frac-tion. This a¡ects the biostratigraphic results ofbiozones P0 and P1a. In addition, the relativeabundances of small species is signi¢cantly largerin the smaller size fraction because they tend tofall through the larger sieve size (s 63 Wm). Con-versely, the larger size fraction (s 63 Wm) wasanalyzed because larger species tend to be under-represented in the smaller size fraction. Quantita-tive results of the two size fractions are shownfor the Elles II outcrop (Tables 1 and 2). Forthe biogeographic maps, relative abundances ofthe s 63-Wm size fraction was used. Species iden-ti¢cations are based on Robaszynski et al. (1983/84), Caron (1985), Nederbragt (1991), Keller et al.(1995) and Olsson et al. (1999).

2. Results I

2.1. Elles II

The biostratigraphy and faunal turnover of El-les II are discussed and illustrated here as charac-teristic of the species richness and relative speciesabundances of the K^T transition in Tunisia, andin the low latitude Tethys in general. The litho-stratigraphy of this expanded sequence is charac-teristic of Tunisian sections, but may also be rel-evant in other regions, assuming that the K^Ttransition evident in Tunisia records global, ratherthan local trends.

Elles II is located about 75 km southeast of ElKef near the hamlet of Elles in a valley cut by the

PALAEO 2758 1-5-02


Karma river. Following the river upsection towhere the valley forks, Elles I is located in theright side valley fork (see Karoui-Yaakoub etal., 2002) and Elles II in the left side valleyfork. Elles II di¡ers from Elles I primarily in themore expanded K^T transition and the presenceof a 20^25 cm thick bioclastic bed with ripplemarks below the K^T boundary clay and redlayer.

2.2. Lithology and lithostratigraphy

The uppermost Maastrichtian at Elles II con-sists of monotonous gray marls and silty shales.

An important sedimentological change occurs inthe 25^30 cm thick interval directly underlying theK^T boundary red layer (Fig. 3). In this intervalgray marls ¢rst grade into gray calcareous silt-stones and then into gray calcarenites, both ofwhich form layers of 5 cm and 8 cm thick respec-tively. Overlying this interval is a 5^7 cm thickyellow calcarenite consisting primarily of plank-tonic foraminiferal tests (foraminiferal pack-stone). The foraminiferal packstone is yellowish,cross-bedded and burrowed. Burrows are about5 mm in diameter, unbranched and reach a lengthof a few centimeters. Most of the burrows arehorizontal or oblique, but a few are almost verti-cal with the upper end at the top of the packstonelayer. All of the burrows are in¢lled with the yel-low marly sediment and none with the green claythat overlies the foraminiferal packstone. This in-dicates that colonization and in¢lling of burrowsoccurred before deposition of the green clay layer.Because the upper surface of the packstone is alsoan undulating erosional surface, an unconformityis present between the top of the packstone andthe green clay. However, this hiatus appears to bevery short as suggested by the presence of themost expanded zone CF1 known to date (10 mat Elles as compared with 6 m at El Kef; Pardo etal., 1996; Abramovich et al., 2002).

The overlying plastic green clay varies between0.2 to 1 cm thick and ¢lls the depressions in thepackstone. Above the green clay is the 2^4 mmthick rusty red layer that generally marks the K^Tboundary event and contains maximum concen-trations of Ir- and Ni-rich spinels (Rocchia et al.,1995; Robin et al., 1995). No burrows are ob-served across the red and green layers. Overlyingthe red layer is another 1^2 cm thick plastic greenclay layer with a second very thin red layer(Fig. 3). No burrows are observed in this coupleteither.

Upsection, the green clay grades into ¢ssileclays with small Fe concretions. The lowermost10 cm of the clay are black, rich in organic matterand contain rare casts of nuculanid bivalves. Theblack clays grade into dark gray shaley clays over-lain by gray shales which are less ¢ssile. Biotur-bation was noted at 50 cm above the K^T bound-ary (Fig. 3).

Fig. 3. Lithology across the K^T transition at Elles II. Notethe 25^30 cm thick foraminiferal packstone and cross-beddedunit just below the K^T boundary.

PALAEO 2758 1-5-02


Tab

le1A

Rel

ativ

epe

rcen

tab

unda

nces

ofpl

ankt

onic

fora

min

ifer

a(s

63W

m)

belo

wth

eK

^Tbo

unda

ryat

Elle

sII

,T

unis

ia(X

=ra

re)

Bio

zone

sP

lum

mer

ita

hant

keni

noid

es

Sam

ples

:cm

belo

wK

^T0

0^0.

50.

5^1.

51.

5^2.

52.

5^3.

57.

5^8.

511

.5^1

515

^20

25^3

035

^40

45^5

055

^60

65^7

075

^80

85^9

095

^100

Aba

thom

phal

usm

ayar

oens

isX

XA

rche

oglo

bige

rina

blow

iX

XX

1X

XX

XX

XX

Gan

sser

ina

wie

denm

ayer

iX

XX

XX

XX

1X

XX

XG

lobi

geri

nello

ides

aspe

ra4

42

X3

21

52

33

24

42

1G

.su

bcar

inat

usX

X1

G.

yauc

oens

is1

33

43

21

22

34

31

11

2G

.vo

lutu

sX

X1

2X

1X

XX

XG

lobo

trun

cane

llape

talo

idea

XX

XX

11

1X

1X

1X

X3

1X

G.

min

uta

2X

1X

11

1X

X1

XX

1X

XG

lobo

trun

cana

arca

XX

XX

1X

X1

1X

11

11

G.

aegy

ptia

caX

1X

XX

XX

XX

XX

X1

XX

G.

duw

iX

XX

1X

X1

XX

XX

XG

.es

nehe

nsis

XX

XX

X1

XX

XX

XG

.fa

lsos

tuar

tiX

XX

XX

XX

XX

XG

.in

sign

isX

XX

XX

XX

XX

XX

XX

G.

dupe

uble

iX

XX

XX

XX

XX

XX

XX

XX

XG

.ro

sett

aX

XX

XX

XX

XX

1X

XX

11

XG

lobo

trun

cani

taan

gula

taX

XX

XX

XG

.co

nica

XX

XX

XX

XX

XX

XX

X4

XX

G.

pett

ersi

XX

X1

1X

X1

XX

XG

.st

uart

iX

XX

XX

XX

XX

XX

XX

XX

XG

.st

uart

ifor

mis

XX

XX

XX

XX

XX

XX

XX

Gub

leri

nacu

vilie

riX

G.

robu

sta

XX

XX

XG

uem

belit

ria

cret

acea

XX

92

21

1X

11

11

XX

G.

dani

caX

1X

G.

irre

gula

ris

X2

1G

.tr

ifol

iaX

XX

Hed

berg

ella

holm

dele

nsis

41

1X

1X

X1

12

2X

32

X2

H.

mon

mou

then

sis

41

64

11

22

22

21

21

33

Het

eroh

elix

cari

nata

11

X1

23

12

75

64

31

37

H.

dent

ata

11X

819

1615

2212

1621

1314

1012

1613

H.

glob

ulos

a22

1716

1012

912

1116

99

1011

1213

10H

.la

bello

sa2

32

34

66

63

31

23

32

5H

.m

orem

ani

XX

XX

22

1X

H.

nava

rroe

nsis

2630

2323

2115

1819

1014

2017

2111

819

H.

plan

ata

36

12

67

66

76

76

67

68

H.

pulc

hra

11

21

12

22

13

11

1X

H.

stri

ata

3X

XX

X2

XX

PALAEO 2758 1-5-02


Tab

le1A

(con

tinu

ed)

Bio

zone

sP

lum

mer

ita

hant

keni

noid

es

Sam

ples

:cm

belo

wK

^T0

0^0.

50.

5^1.

51.

5^2.

52.

5^3.

57.

5^8.

511

.5^1

515

^20

25^3

035

^40

45^5

055

^60

65^7

075

^80

85^9

095

^100

Pla

nogl

obul

ina

cars

eyae

XX

XX

XX

XX

XX

XX

XX

XX

P.

mul

tica

mer

ata

XX

XX

XX

XX

XX

P.

braz

oens

isX

XX

XX

XX

XX

XX

XX

Plu

mm

erit

aha

ntke

nino

ides

XX

XX

1X

XX

X1

XX

Pse

udog

uem

belin

aco

stul

ata

1221

1620

1618

1619

1612

1615

2118

2116

P.

hari

aens

isX

1X

X1

x1

X1

1X

XX

Xx

1P

.ke

mpe

nsis

32

22

55

23

42

17

54

74

P.

palp

ebra

XX

X1

XX

1X

1X

XX

11

XX

P.

punc

tula

ta2

52

23

71

34

21

75

47

4P

seud

otex

tula

ria

defo

rmis

XX

XX

XX

XX

XX

XX

11

XX

P.

eleg

ans

XX

XX

XX

XX

XX

XX

X1

XX

Rac

emig

uem

belin

ain

term

edia

XX

XX

XX

XX

XX

XX

XR

.po

wel

liX

XX

XX

XX

XX

XX

R.

fruc

tico

saX

XX

XX

XX

XX

XX

XX

XX

XR

osit

aco

ntus

aX

XX

XX

XX

XR

.pa

telli

form

isX

XX

XX

XX

XX

XX

XX

XR

.w

al¢s

chen

sis

XX

XR

ugog

lobi

geri

nahe

xaca

mer

ata

XX

1X

X1

12

14

X1

34

1R

.m

acro

ceph

ala

XX

X1

1X

XX

XX

Rug

oglo

bige

rina

reic

heli

XX

XR

.ro

tund

ata

11

XX

11

1X

XX

XX

1X

XR

.ru

gosa

11

XX

11

22

X3

21

X2

21

R.

scot

tiX

XX

X1

XX

X1

1X

X1

XX

PALAEO 2758 1-5-02


Tab

le1B

Rel

ativ

epe

rcen

tab

unda

nces

ofpl

ankt

onic

fora

min

ifer

a(s

63W

m)

abov

eth

eK

^Tbo

unda

ryat

Elle

sII

Tun

isia

(X=

rare

)

Bio

zone

sP

0P

1a

Sam

ples

:cm

abov

eK

^T0^

0.5

1^2

3^4

4^5

8^10

12^1

518

^20

25^3

035

^40

45^5

055

^60

65^7

075

^80

85^9

095

^100

105^

110

Glo

bige

rine

lloid

esas

pera

4X

1X

XX

XG

.su

bcar

inat

us1

1G

.ya

ucoe

nsis

21

1X

XX

G.

volu

tus

XX

XX

Glo

botr

unca

nella

peta

loid

eaX

XX

G.

min

uta

XX

XG

lobo

trun

cana

arca

XX

XG

.ae

gypt

iaca

XX

XG

.es

nehe

nsis

XX

XG

.ro

sett

aX

1G

lobo

trun

cani

tast

uart

iX

XG

uem

belit

ria

cret

acea

1126

3875

84X

XX

XX

XX

4032

6521

G.

dani

ca2

XX

104

XX

XX

XX

86

X3

G.

irre

gula

ris

1X

X5

7X

XX

XX

XX

27

64

G.

trif

olia

17

23

XX

XX

2H

edbe

rgel

laho

lmde

lens

is1

42

XX

12

H.

mon

mou

then

sis

21

2X

X1

Het

eroh

elix

cari

nata

XX

1X

H.

dent

ata

2018

142

1X

XX

23

1H

.gl

obul

osa

117

51

1X

X2

H.

labe

llosa

52

4H

.na

varr

oens

is16

1414

21

XX

X2

11

H.

plan

ata

34

41

XX

XX

Pla

nogl

obul

ina

cars

eyae

XX

Pse

udog

uem

belin

aco

stul

ata

98

4X

XX

XX

3P

.ha

riae

nsis

XX

P.

kem

pens

is2

22

XX

XX

P.

palp

ebra

1X

XP

.pu

nctu

lata

42

1X

Pse

udot

extu

lari

ade

form

isX

1P

.el

egan

sX

Rac

emig

uem

belin

ain

term

edia

XR

.fr

ucti

cosa

XR

ugog

lobi

geri

nahe

xaca

mer

ata

XX

XX

R.

mac

roce

phal

a2

1X

11

R.

rugo

sa1

X1

XX

Glo

boco

nusa

daub

jerg

ensi

s1

Eog

lobi

geri

naeo

bullo

ides

1E

.ed

ita

3E

.fr

inga

11

PALAEO 2758 1-5-02


Tab

le2A

Rel

ativ

epe

rcen

tab

unda

nces

ofpl

ankt

onic

fora

min

ifer

ain

the

size

frac

tion

38^6

3Wm

belo

wth

eK

^Tbo

unda

ryat

Elle

sII

,T

unis

ia

Bio

zone

sP

lum

mer

ita

hant

keni

noid

es

Sam

ples

:cm

belo

wK

^T0^

0.5

0.5^

1.5

1.5^

2.5

2.5^

3.5

7.5^

8.5

11.5

^15

15^2

025

^30

35^4

045

^50

55^6

065

^70

Glo

bige

rine

lloid

esya

ucoe

nsis

32

35

74

35

21

41

Gue

mbe

litri

acr

etac

ea23

2321

1522

1939

2013

1831

29G

.da

nica

42

34

43

21

22

G.

irre

gula

ris

36

93

36

52

68

2G

.tr

ifol

ia3

21

33

11

15

5H

edbe

rgel

laho

lmde

lens

is3

22

59

44

116

H.

mon

mou

then

sis

129

76

68

57

52

54

Het

eroh

elix

dent

ata

1210

1314

1631

1718

2016

2315

H.

glob

ulos

a9

105

32

2H

.pl

anat

a3

22

H.

nava

rroe

nsis

2230

2537

2726

2030

3435

2437

Pse

udog

uem

belin

aco

stul

ata

64

85

63

6H

eter

ohel

icid

juve

nile

s3

22

32

59

24

Tot

alco

unte

d23

226

726

729

531

125

618

330

424

814

822

922

2

Tab

le1B

(con

tinu

ed)

Bio

zone

sP

0P

1a

Sam

ples

:cm

abov

eK

^T0^

0.5

1^2

3^4

4^5

8^10

12^1

518

^20

25^3

035

^40

45^5

055

^60

65^7

075

^80

85^9

095

^100

105^

110

S.

triv

ialis

11

Par

vula

rugo

glob

erin

aeu

gubi

na1

31

P.

exte

nsa

X24

123

1T

otal

coun

ted

266

250

226

122

137

00

00

00

012

513

577

89

PALAEO 2758 1-5-02


Tab

le2B

Rel

ativ

epe

rcen

tab

unda

nces

ofpl

ankt

onic

fora

min

ifer

ain

the

size

frac

tion

38^6

3Wm

abov

eth

eK

^Tbo

unda

ryat

Elle

sII

Tun

isia

(X=

rare

)

Bio

zone

sP

0P

1a

Sam

ples

:cm

abov

eK

^T0^

0.5

0.5^

1.0

1^2

3^4

4^5

8^10

12^1

518

^20

25^3

035

^40

45^5

055

^60

65^7

075

^80

85^9

095

^100

105^

110

Glo

bige

rine

lloid

esas

pera

12

11

X1

XX

XX

G.

subc

arin

atus

XX

G.

yauc

oens

is1

11

XX

G.

volu

tus

1X

1X

Glo

botr

unca

nella

peta

loid

eaX

XG

.m

inut

aX

XX

XG

lobo

trun

cana

arca

XX

XG

.ae

gypt

iaca

XX

XX

G.

duw

iX

G.

esne

hens

isX

XX

XG

.ro

sett

aX

XX

Glo

botr

unca

nita

stua

rti

XX

Gue

mbe

litri

acr

etac

ea20

2340

3137

3967

4561

5353

5357

4850

4336

G.

dani

ca4

25

66

118

108

63

41

55

54

G.

irre

gula

ris

2517

3049

4334

1229

1420

2220

1212

1013

18G

.tr

ifol

ia4

78

67

52

62

11

13

33

21

Hed

berg

ella

holm

dele

nsis

32

1X

11

1X

XH

.m

onm

outh

ensi

s2

2X

11

1X

XH

eter

ohel

ixca

rina

ta1

11

XX

XH

.de

ntat

a13

116

11

1X

11

XX

X1

H.

glob

ulos

a6

42

12

1X

1X

XH

.la

bello

sa1

1X

XH

.na

varr

oens

is10

154

1X

2X

12

1H

.pl

anat

a1

2X

1X

XX

H.

pulc

hra

XX

Pla

nogl

obul

ina

cars

eyae

XX

Pse

udog

uem

belin

aco

stul

ata

45

X1

21

XX

XX

XP

.ha

riae

nsis

XX

P.

kem

pens

is1

11

1X

XX

P.

palp

ebra

XX

XX

P.

punc

tula

ta1

1X

XX

Pse

udot

extu

lari

ade

form

isX

XX

P.

eleg

ans

XR

acem

igue

mbe

lina

inte

rmed

iaX

Rug

oglo

bige

rina

hexa

cam

erat

aX

XX

XR

.m

acro

ceph

ala

XX

XR

.ru

gosa

XX

XX

Glo

boco

nusa

daub

jerg

ensi

s5

53

Eog

lobi

geri

naeo

bullo

ides

11

X1

11

12

2

PALAEO 2758 1-5-02


2.3. Biostratigraphy

2.3.1. Taxonomic notesRecently, a new classi¢cation of Paleocene

planktonic foraminifera based on wall texturewas published (Olsson et al., 1999). This studygenerally follows this new classi¢cation schemefor the early Danian species though with someexceptions that are explained below.Parasubbotina pseudobulloides (Plummer, 1926):This well-known species is characterized by 5chambers in the last whorl (rarely 6) and rapidlyincreasing chamber size. Well-developed large(s 150 Wm) morphotypes ¢rst appear after theextinction of Parvularugoglobigerina eugubina.But forms with 4.5^5 chambers appear earlier inthe upper half of the P. eugubina range (zone P1a)and later coexist with the well-developed pseudo-bulloides morphotypes. The ¢rst appearance ofthis morphotype marks the subdivision of zoneP1a (Fig. 4). Olsson et al. (1999) assign thesespecimens to a separate group P. a¡. pseudobul-loides. However, since these forms appear to bepart of a continuous variation within the pseudo-bulloides population and separation is di⁄cult atbest, we retain this early morphotype within P.pseudobulloides.Subbotina triloculinoides (Plummer, 1926): This isanother well-known species with 3.5 globosechambers in the last whorl and the last chambercharacteristically enveloping the upper half of thetest. This morphotype ¢rst appears in the middleof zone P1a nearly coincident with Parasubbotinapseudobulloides and marks the subdivision of zoneP1a (Fig. 4), though, as with the latter species,large morphotypes (s 150 Wm) of S. triloculi-noides do not appear until after the extinction ofParvularugoglobigerina eugubina. Olsson et al.(1999) recognize only the larger morphotypeswhich they date as ¢rst appearing at 64.5 Ma.Guembelitria cretacea Cushman, 1933; Olsson etal. (1999) group all triserial morphotypes withinthe species G. cretacea, including the high-spireddanica, the irregularly stacked chambers of irre-gularis and the short-spired trifolia. Although weagree that all three morphotypes share the same¢nely perforate wall texture, globular chambersand overall triserial chamber arrangement, theyT

able

2B(c

onti

nued

)

Bio

zone

sP

0P

1a

Sam

ples

:cm

abov

eK

^T0^

0.5

0.5^

1.0

1^2

3^4

4^5

8^10

12^1

518

^20

25^3

035

^40

45^5

055

^60

65^7

075

^80

85^9

095

^100

105^

110

E.

edit

a1

25

53

1012

910

11E

.fr

inga

1X

22

25

33

6S

.tr

ivia

lisX

Par

vula

rugo

glob

erin

aeu

gubi

na2

24

104

44

44

P.

exte

nsa

11

11

X5

X4

810

65

46

118

Glo

bano

mal

ina

com

pres

saX

11

XX

Tot

alco

unte

d38

341

035

841

427

038

312

624

029

141

239

241

536

833

244

832

636

5

PALAEO 2758 1-5-02


are also very distinct and easily identi¢ed mor-photypes which di¡er in their relative abundancedistributions geographically and through time.They may represent either di¡erent species or eco-logical variants. We continue to separate thesemorphotypes in order to evaluate their strati-graphic and ecological a⁄nities.Parvularugoglobigerina eugubina (Luterbacher andPremoli Silva, 1964): This small species was orig-inally de¢ned as a 5^6 (rarely 8) chambered formwith in£ated subglobular chambers and high openaperture. Blow (1979) described a small specieswith 5^8 compressed chambers and slit-like nar-row aperture, with a similar stratigraphic range,as longiapertura. Olsson et al. (1999) consider thisform a variant of P. eugubina. We retain the sep-aration of these two distinct morphotypes becausetheir geographic distribution may eventually pro-vide paleoecological information.Parvularugoglobigerina extensa (Blow, 1979); Ols-son et al. (1999) consider the species formerlyclassi¢ed as Globoconusa conusa (Khalilov) a jun-ior synonym of P. extensa and we follow thisconvention.

2.3.2. BiozonationThe biozonation of Keller et al. (1995) is used

in this study (Fig. 4). Berggren et al.’s (1995) re-vised zonation uses the same index species for thetwo lowermost Danian zones, but call Keller etal.’s P1a zone PK. Keller et al. (1995) subdividezone P1a (range of Parvularugoglobigerina eugubi-na) based on the ¢rst appearances of Parasubbo-tina pseudobulloides (P. a¡. pseudobulloides of Ols-son et al., 1999) and/or Subbotina triloculinoides.

2.3.2.1. Plummerita hantkeninoides ZoneThis zone marks the end of the Maastrichtian

and spans the range of Plummerita hantkeninoidesas de¢ned by Masters (1984, 1993) and subse-quently by Pardo et al. (1996) (Fig. 4). At EllesII, as well as other Tunisian sections, P. hantke-ninoides is consistently present (except for twosamples), whereas only two occurrences of Aba-thomphalus mayaroensis (the alternative lateMaastrichtian marker species) were noted (at theK^T boundary and at 1 m below, Fig. 5). At EllesI and Elles II the range of P. hantkeninoides spans

the last 7 m and 10 m of the Maastrichtian re-spectively (Abramovich and Keller, 2002) as com-pared with 6 m at El Kef (Li and Keller, 1998a).Agewise the range of this excellent latest Maas-trichtian marker species spans the last 300 kyr ofthe Maastrichtian, or most of chron 29R belowthe K^T boundary, as estimated from the paleo-magnetic record at Agost (see Pardo et al., 1996;Groot et al., 1989). This species is easily identi¢edby its long apical spines and is common in Tuni-sian sections where its stratigraphic range (gener-ally s 6 m) provides a good estimate of the com-pleteness of the latest Maastrichtian interval. TheP. hantkeninoides Zone replaces the A. mayaroen-sis Zone for the top part of the Maastrichtian.

2.3.2.2. K^T boundaryThis boundary is de¢ned by the coincidence of

several characteristic lithological and geochemicalcriteria in all sections in Tunisia (e.g., Fig. 3) andworldwide including: a lithological change frommarls or shales to dark gray or black organic-rich clay; a 2^4 mm thin rusty red layer at thebase of the clay; the presence of spherules, spinelsand anomalous concentrations of Ir and otherplantinum group elements in the rusty red layer.

Paleontological criteria include the extinction ofall ornate large tropical and subtropical species,including all globotruncanids, racemiguembelinidsand rugoglobigerinids (with the possible exceptionof Rugoglobigerina macrocephala) below the redlayer and organic-rich clay layer. This extinctionhorizon is followed by the ¢rst appearance ofDanian species at or near the base of the organ-ic-rich black clay (e.g., Parvularugoglobigerina ex-tensa, Eoglobigerina fringa, Eoglobigerina edita,Eoglobigerina eobulloides, Woodringina horner-stownensis).

2.3.2.3. P0 zoneThis zone spans the part of the basal Danian

organic-rich black clay layer from the extinctionof the tropical^subtropical species group (at therusty red layer) to the ¢rst appearance of Parvu-larugoglobigerina eugubina and/or Parvularugoglo-bigerina longiapertura (Fig. 4). In many earlierstudies zone P0 was considered to span the organ-ic-rich clay layer (e.g., Smit, 1982; Keller, 1988;

PALAEO 2758 1-5-02


Olsson and Liu, 1993; Molina et al., 1998). This isalso supported by the ¢rst occurrence of themarker species in the s 63-Wm size fraction nearthe top of the clay layer (at 65 cm above the redlayer) at Elles I and Elles II (Table 2A, Fig. 5).However, new studies based on the smaller 36^63-Wm size fraction at Elles I and Elles II indicatesmall P. eugubina ¢rst appear 25^30 cm above thered layer, whereas small P. longiapertura ¢rst ap-pear at 45^50 cm (Fig. 6, Table 2B, see also Ka-roui-Yaakoub et al., 2002). This suggests that P0may be restricted to the lower half of this blackclay layer. Zone P0 is noteworthy for its commonpresence of reworked Cretaceous tropical speciesand large abundance of triserial species.

2.3.2.4. P1a zoneThis range zone spans from the ¢rst appearance

of Parvularugoglobigerina eugubina and/or Parvu-larugoglobigerina longiapertura to the extinctionof these taxa. Due to the increased terrigenousin£ux from the nearby Kasserine Island at EllesI and II, as well as at Ain Settara, the P1a zone isabout 5^6 m thick and hence more expanded thanthe 4.5 m observed at El Kef (Keller, 1988). Atthe more distant and deeper water locality of ElMelah, zone P1a is condensed and only 1.4 mthick. Zone P1a can be subdivided into P1a(1)and P1a(2) based on the ¢rst appearance (FA)of Parasubbotina pseudobulloides (Fig. 4).

2.3.3. Faunal turnover

2.3.3.1. Species extinctionsA total of 60 Cretaceous species are pres-

ent in the last 100 cm of the Elles II section in

Fig. 4. Planktonic foraminiferal zonation of Keller et al. (1995) and comparison with Berggren et al. (1995).

PALAEO 2758 1-5-02


Fig

.5.

Pla

nkto

nic

fora

min

ifer

alsp

ecie

sra

nges

acro

ssth

eK

^Ttr

ansi

tion

atE

lles

IIba

sed

onth

es

63-W

msi

zefr

acti

on.

PALAEO 2758 1-5-02


Fig

.6.

Pla

nkto

nic

fora

min

ifer

alsp

ecie

sra

nges

acro

ssth

eK

^Ttr

ansi

tion

atE

lles

IIba

sed

onth

e36

-63-W

msi

zefr

acti

on.

Not

eth

edi

¡er

ence

sbe

twee

nth

esp

ecie

sce

nsus

data

ofth

etw

osi

zefr

acti

ons

inF

igs.

5an

d6.

PALAEO 2758 1-5-02


Fig

.7.

(A)

Rel

ativ

esp

ecie

sab

unda

nces

ofth

ein

dige

nous

Cre

tace

ous

plan

kton

icfo

ram

inif

era

acro

ssth

eK

^Tbo

unda

ryat

Elle

sII

inth

es

63-W

msi

zefr

acti

on.

Not

eth

atal

lof

thes

esp

ecie

s,w

hich

are

cons

ider

edex

tinc

tat

orne

arth

eK

^Tbo

unda

ry,

are

trop

ical

tosu

btro

pica

lan

dar

era

reto

few

oron

lysp

orad

ical

lypr

esen

tdi

rect

lybe

low

the

top

ofth

eM

aast

rich

tian

.T

heir

com

bine

dto

tal

abun

danc

eis

less

than

20%

ofth

eC

reta

ceou

sas

sem

blag

e.T

hus,

the

K^T

boun

dary

mas

sex

tinc

tion

sele

ctiv

ely

elim

inat

edth

ese

subt

ropi

cal

totr

opic

alec

olog

ical

spec

ialis

ts.

(B)

Rel

ativ

esp

ecie

sab

unda

nces

ofC

reta

ceou

ssu

rviv

ors

and

evol

ving

earl

yT

erti

-ar

ypl

ankt

onic

fora

min

ifer

ain

uppe

rmos

tM

aast

rich

tian

and

low

erm

ost

Dan

ian

sedi

men

tsat

Elle

sII

.F

auna

lco

unts

are

base

don

thes

63-W

msi

zefr

acti

on.

Not

eth

atsp

ecie

sin

P0

and

the

low

erpa

rtof

P1a

(1)

are

near

lyab

sent

inth

issi

zefr

acti

onbe

caus

eth

eyar

edw

arfe

ddu

eto

high

stre

ssco

ndit

ions

and

ther

efor

eon

lyco

mm

onin

the

smal

ler

36^6

3-W

msi

zefr

acti

on(F

ig.

8).

PALAEO 2758 1-5-02


Fig

.7

(con

tinu

ed).

PALAEO 2758 1-5-02


Fig

.8.

Rel

ativ

esp

ecie

sab

unda

nces

ofC

reta

ceou

ssu

rviv

ors

and

evol

ving

earl

yT

erti

ary

plan

kton

icfo

ram

inif

era

inup

perm

ost

Maa

stri

chti

anan

dlo

wer

mos

tD

ania

nse

dim

ents

atE

lles

IIin

the

36^6

3-W

msi

zefr

acti

on.

Not

eth

atth

issm

all

size

frac

tion

cont

ains

abun

dant

high

stre

ss,

dwar

fed

spec

ies

whi

char

ege

nera

llyno

tfo

und

inth

ela

rger

(s63

-Wm

)si

zefr

acti

on.

For

this

reas

on,

the

smal

l38

^63-W

msi

zefr

acti

onha

sto

beex

amin

edfo

rth

eK

^Ttr

ansi

tion

inte

rval

tode

term

ine

the

pres

ence

and

abse

nce

ofD

ania

nsp

ecie

sas

wel

las

the

faun

altu

rnov

er.

PALAEO 2758 1-5-02


the s 63-Wm size fraction (Fig. 5) and anotherthree species are present only in the smaller (38^63-Wm) size fraction (Guembelitria danica, Guem-belitria irregularis, Guembelitria trifolia, Fig. 6). Acomparable number of species was identi¢ed at ElKef (57 species, Keller et al., 1995; Keller, 1996),Ain Settara (Luciani, 2002) and El Melah (thisstudy). Most species range through the last meterinterval below the K^T boundary. Though only afew species were not observed in the top 10 cmbelow the K^T boundary (e.g., Gublerina cuvilieri,Rosita wal¢shensis, Globotruncanita angulata, Ru-goglobigerina reicheli), many species reappear inthe top 25 cm (Fig. 5) within the foraminiferalpackstone layer marked by cross-bedding. Thissuggests that there is signi¢cant transportationand reworking of older assemblages within thepackstone and for this reason we excluded thepackstone from our paleobiogeographic database.

Though most species disappear at or below theK^T boundary, 16 species (Heterohelix carinatato Rugoglobigerina rugosa, Fig. 5) are also presentin the lower zone P0 (Fig. 5); these are consideredreworked because many of the specimens showdi¡erential preservation or are broken. In sectionsglobally, these species generally disappear nearthe K^T boundary (MacLeod and Keller, 1994).A total of 16 Cretaceous species range well intothe early Danian and are considered as survivorsas discussed below.

Thus, we consider all but 16 species, or 75%, asextinct at or near the K^T boundary (Gublerinacuvilieri to Rugoglobigerina rugosa in Fig. 5);though the combined relative abundance of thisgroup averages less than 20% of the total assem-blage (Fig. 7A,B). The same species extinctionand relative abundance pattern was observed atEl Kef (Keller et al., 1995, ¢g. 11, p. 243) and atAin Settara (Luciani, 2002). Nearly all of the ex-tinct species have large morphologies, highly or-namented tests, and their geographic distributionsare restricted to low and middle latitudes. Weconsider these taxa as ecological specialists welladapted to tropical and subtropical environments,but intolerant of environmental changes, includ-ing £uctuations in temperature, nutrients, oxygenand salinity as discussed below.

2.3.3.2. SurvivorsThe fact that the mass extinction eliminated

only ecological specialists having relatively nar-row ecological habitats points to a selectivemass extinction pattern. The group of 16 species(or 25%) which range into the lower Danian zonesP0 and P1a are generally common to abundant(s 80%) in the upper Maastrichtian (Fig. 5, Het-erohelix planata to Guembelitria trifolia ; see alsoFig. 6 for ranges of small species in the 38^63-Wmsize fraction, Figs. 7A,B and 8). A similar numberof Cretaceous species range well into the lowerDanian at El Kef, El Melah and Ain Settara (16species). These species are considered Cretaceoussurvivors because they have been observed to beconsistently present in early Danian sediments ofsections worldwide, do not show di¡erential pres-ervation as compared with Danian species, andmany have Danian stable isotope signals (Barreraand Keller, 1990, 1994; Keller et al., 1993; Mac-Leod and Keller, 1994).

Among these 16 species, Pseudoguembelina cos-tulata, and Pseudoguembelina kempensis were notpreviously considered survivors, but are tenta-tively included here because of their consistentoccurrence in Danian sediments ; though furtherstudies are necessary to determine their extinctiondatum. All the survivor taxa are biserial (mostlyheterohelicids), triserial (guembelitrids), trocho-spiral (hedbergellids) and planispiral (globigeri-nellids). Morphologically, these taxa are generallysmall with little or no surface ornamentation.They are geographically widespread and for themost part common to abundant. We considerthem ecological generalists, able to tolerate £uc-tuations in temperature, nutrients, oxygen andsalinity.

It is noteworthy that in the examination ofthe s 63-Wm size fraction, the new Danian speciesas well as most of the Cretaceous survivors areabsent in an interval spaning part of P0 and thelowermost part of P1a (Fig. 7B) as also observedearlier at El Kef (Keller, 1988; Keller et al., 1995),ODP Site 738 (Keller, 1993) and Haiti (Kelleret al., 2001). Nevertheless, in the smaller sizefraction (38^63 Wm) these species are commonto abundant (Fig. 8, Tables 1 and 2). This re-£ects the dwar¢ng of species in environmentally

PALAEO 2758 1-5-02


stressed habitats (see MacLeod et al., 2000). How-ever, it also illustrates that biostratigraphicand faunal turnover conclusions based solely onthe s 63-Wm size fraction are in error.

2.3.3.3. OpportunistsThe populations of most Cretaceous survivors

dramatically decline in the lower Danian zones P0and P1a and never recover. Some Cretaceous spe-cies, however, thrive after the mass extinction oftropical and subtropical species and the decline ofthe ecological generalist survivors. These are thetriserial Guembelitria species in low to middle lat-itudes and the biserial Zeauvigerina waiparaensisin high latitudes (Keller, 1993; Pardo and Keller,1999). These biserial and triserial taxa dominated(s 95%) the faunal assemblages during the earlyDanian in the absence of ecological competitionas a result of the mass extinction and decline ofsurvivor species, and prior to the establishment ofthe newly evolving Danian assemblages.

Guembelitria species are generally present invery low abundances (6 1%) in Cretaceous faunalassemblages of normal open marine conditionsand more abundant (s 10^25%) in shallow neriticnear-shore environments characteristic of variabletemperature, oxygen, salinity and nutrient condi-tions (see Keller et al., 1998). However, wheneveropen marine environmental conditions reach acrisis level and reduce normal population diversitythey produce opportunistic blooms (e.g., K^Tboundary, Cenomanian^Turonian boundary, and

three blooms in the late Maastrichtian, Abramo-vich et al., 1998; Keller et al., 2001). In openmarine conditions, such an opportunistic Guembe-litria bloom began in zone P0 and continuedthrough P1a, though tapering o¡ in the laterpart of P1a (Keller et al., 1994; Luciani, 1997;Molina et al., 1998; Olsson and Liu 1993; Apel-laniz et al., 1997). However, in near-shore shallowneritic environments, such as Seldja on the SaharaPlatform or Brazos River in Texas, the Guembeli-tria blooms began in the latest Maastrichtian sug-gesting that adverse environmental conditions be-gan well prior to the K^T boundary event (Keller,1989; Keller et al., 1998).

In northern and southern high latitude sections,such as in Kazakstan and ODP Site 738, theGuembelitria bloom in the lower Danian is muchreduced (V20^30%) and the biserial species Zeau-vigerina waiparaensis takes its place as the domi-nant opportunistic species (Keller, 1993; Pardoand Keller, 1999). Zeauvigerina waiparaensis Jen-kins was originally considered a Danian species,but was found to be common (V20%) in theupper Maastrichtian of Site 738 (Keller, 1993),as well as in northern high latitude sections (Par-do and Keller, 1999). Opportunistic blooms ofthis species began below the K^T boundary andincreased to 80% in P0 and P1a. This waiparaensisbloom may be linked to a tolerance for low oxy-gen conditions in the increasingly high nutrientenvironment of the early Danian in high latitudesas suggested by increased Ba, a proxy for nu-

Plate I. Ecological generalists. This group is characterized by species of small morphology, weak surface ornamentation, and bise-rial, triserial, trochospiral or planispiral chamber arrangement. All specimens from the top 50 cm below the K^T boundary at ElKef and Ain Settara. Scale bar = 100 Wm.

1, 2. Globigerinelloides aspera (Bolli)3, 4. Globigerinelloides yaucoensis (Pessagno)5, 6. Hedbergella monmouthensis (Olsson)7. Globotruncanella subcarinatus Bronnimann8. Globotruncanella petaloidea Gandol¢9. Heterohelix navarroensis Loeblich10^13. Heterohelix globulosa (Ehrenberg)14. Heterohelix dentata Stenestad15, 16. Guembelitria cretacea (Cushman).

PALAEO 2758 1-5-02


PALAEO 2758 1-5-02


trients, and the absence of a major negative car-bon-13 shift (Barrera and Keller, 1994). This spe-cies is very rare in low latitudes possibly becausevery low nutrient conditions prevailed in the earlyDanian as suggested by the 2^3x carbon-13shift (Keller and Lindinger, 1989; Zachos et al.1989; Oberha«nsli et al., 1998).

2.3.3.4. K^T faunal turnoverThe overall mass extinction pattern at Elles II is

similar to that observed at El Kef (Keller et al.,1995), Ain Settara (Luciani, 2002), Mexico (Lo-pez-Oliva and Keller, 1996), Haiti (Keller et al., inpreparation), Italy (Luciani, 1997), Spain (Canu-do et al., 1991; Apellaniz et al., 1997) and otherlow latitude regions. Over two thirds of the spe-cies disappeared at or near the K^T boundaryand nearly one third of the species survived intothe early Danian. The K^T extinct species group(which here includes species which are rare andmay have disappeared earlier) consists of ecolog-ical specialists which includes all tropical and sub-tropical species. These ecological specialists aregenerally characterized by highly ornamented,large multiserial or keeled morphologies. Theircombined relative abundance is less than 20% ofthe total planktonic foraminiferal assemblages(Fig. 8). In contrast, the K^T survivor group con-sists of ecological generalists, characterized bysmall biserial, triserial, trochospiral or planispiralmorphologies with little surface ornamentation.Ecological generalists dominate the latest Maas-trichtian oceans and their combined relative abun-dance may exceed 80% (Fig. 8).

3. Results II

3.1. K^T paleoecology

Planktonic foraminiferal assemblages of Tuni-sian sections representing paleodepths between in-ner neritic (V10^20 m, Sedja), middle neritic toouter neritic (100^250 m, Elles and Ain Settara),outer neritic to upper bathyal (200^500 m,El Kef), and predominantly upper bathyal(s 250 m, El Melah, Fig. 2) reveal consistent dif-ferences between shallow restricted marine andopen marine environments both before and afterthe K^T boundary mass extinction. Moreover,Cretaceous foraminiferal assemblages in shallowrestricted and open marine environments re-sponded di¡erently to the environmental stressesthat led to the mass extinction. In contrast, thereis little di¡erence in the evolving early Danianassemblages between open marine and shallowrestricted marginal environments. A number ofdi¡erent proxies, including species richness, eco-logical generalists, specialists and opportunists,and depth ranking, can be used to evaluate theextent and nature of the K^T mass extinction.

3.1.1. Time slice selectionTo facilitate comparison of the pre-K^T and

post-K^T planktonic foraminiferal assemblages,two time slices were chosen. The pre-K^T timeslice is represented by the top 50^100 cm of theuppermost Maastrichtian zone CF1 (Plummeritahantkeninoides). The entire zone CF1 is estimatedto span the last 300 kyr of the Maastrichtian (part

Plate II. Ecological specialists: surface dwellers. This group is heterogeneous and includes trochospiral, biserial and multiserialtaxa which are highly ornamented, of predominantly medium sized morphologies, though a few larger species are also surfacedwellers. All specimens from the top 50 cm below the K^T boundary at El Kef. Scale bar = 100 Wm.

1, 2. Rugoglobigerina rugosa (Plumber)3, 4. Rugoglobigerina scotti Bronnimann5^7. Rugoglobigerina hexacamerata Bronnimann8. Pseudotextularia deformis (Kikoine)9, 10. Rosita contusa (Cushman)11. Planoglobulina brazoensis Martin12. Pseudoguembelina hariaensis Nederbragt13. Pseudoguembelina palpebra Bronnimann and Brown

PALAEO 2758 1-5-02


PALAEO 2758 1-5-02


PALAEO 2758 1-5-02


of chron 29R below the K^T boundary; Pardoand Keller, 1999) and the time slice chosen spansapproximately the last 25^50 kyr of the Maas-trichtian, assuming that no hiatus is present andthat sediment accumulation was constant. Plum-merita hantkeninoides, the index species for zoneCF1, is easily identi¢ed and present in all lowlatitude sections. Within this time slice interval,relative species abundances are averaged to reducebias of extreme £uctuations.

The post-K^T time slice is represented by thelowest Danian zones P0 and lower part of P1a(Parvularugoglobigerina eugubina, basal 50^100cm of the Danian), and is estimated to span the¢rst 50^75 kyr of the Danian (part of chron 29Rabove the K^T boundary), assuming constantsediment accumulation. As in the CF1 time slice,relative species abundances are averaged withinthis time slice to reduce bias of extreme £uctua-tions. Though the ¢rst Danian zone P0 representsthe early Danian time slice, this thin zone com-monly contains reworked Cretaceous species andmay be absent or very thin (a few centimeters atAin Settara). Reworked specimens are identi¢edby their di¡erential preservation, discoloration, orisolated occurrences and have been excluded inthe species richness dataset.

3.2. Paleoenvironment based on species richness

Species richness (the number of species presentin any given sample) is a measure of ecological

diversity and is the most commonly used proxyfor evaluating mass extinctions. However, thisproxy makes no distinction between a speciesthat is rare (often only one specimen), and onethat is abundant. It is therefore only a ¢rst ap-proximation of a mass extinction. For example,the presence or absence of a species in any givensample is also dependent on its numerical abun-dance; rare species may not be observed and theirabsence interpreted as extinctions (e.g., Signor^Lipps e¡ect). Alternatively, the presence of rareand isolated specimens may be due to reworking.These problems have resulted in the controversialinterpretations of sudden vs progressive mass ex-tinction patterns.

In order to avoid this controversy, we estimatespecies richness for the two time slices as the max-imum number of species present in any sampleirrespective of where the last occurrence wasnoted. This means that any species which is notedonly at the base of the time slice, or is an isolatedoccurrence, is counted as present throughout thetime slice (up to the K^T boundary without con-sideration of the reworking potential). This willtend to exaggerate the mass extinction e¡ect andbias it towards a more catastrophic interpretation.The alternative option of excluding these specieswould result in the opposite bias. Since there is noway to evaluate the true species richness, we pre-fer to err on the side of the maximum mass ex-tinction e¡ect. Any bias introduced by the pres-ence of very rare and isolated species will be

Plate III. Ecological specialists : subsurface dwellers. This group is characterized by generally large and highly ornamented mor-phologies, heavily encrusted tests with nods, ridges and keels (globotruncanids, racemiguembelinids). All specimens from the top50 cm below the K^T boundary at El Kef, except for number 4 which is from Ain Settara. Scale bar = 100 Wm.

1. Racemiguembelina intermedia (De Klasz)2. Racemiguembelina fructicosa (Egger)3. Racemiguembelina powelli (Smith and Pessagno)4. Planoglobulina multicamerata (Plummer)5. Pseudotextularia elegans (Rzehak)6. Gublerina cuvilieri Kikoine7, 8. Globotruncana dupeublei Caron9^11. Globotruncanita stuarti (de Lapparent)12. Globotruncana rosetta (Carsey)13. Globotruncana arca (Cushman)14. Globotruncana aegyptiaca Nakkady15, 16. Globotruncana insignis (Gandol¢)

PALAEO 2758 1-5-02


PALAEO 2758 1-5-02


obvious in the biogeographic distribution of therelative abundances of all species extinct.

3.2.1. Species richness patternsNear the end of the Maastrichtian (zone CF1),

planktonic foraminifera in middle neritic to upperbathyal depths are diverse averaging 57^60 specieswith no signi¢cant di¡erences (Fig. 9A). In con-trast, the restricted shallow marine environmentof the Gafsa Basin has a lower diversity of 35species, 17 of which are present in most samples.Another 18 species, which include predominantlyopen marine surface and subsurface dwellers (e.g.,globotruncanids (Globotruncana arca, Globotrun-cana esnehensis, Globotruncana aegyptiaca, Glo-botruncanita stuarti, Globotruncana rosetta), Gub-lerina robusta, Racemiguembelina fructicosa,Rugoglobigerina scotti, Keller et al., 1998) arepresent in few samples. The presence of these lat-ter taxa in the Gafsa Basin is likely due to amarine incursion as a result of a rising sea level(climate warming in chron 29R; see Li and Keller,1998c), or local tectonic activity of the KasserineIsland.

In the early Danian P1a(1) (lower part of Par-vularugoglobigerina eugubina range, Fig. 4), Creta-ceous species richness of open marine environ-ments was reduced to about 15 species (Fig. 5)and in shallow restricted marine environments toabout 11 species (Fig. 9B). In both environments,however, the Cretaceous species assemblages aresimilar consisting of heterohelicids, globigerinel-lids, guembelitrids and hedbergellids. Thus therewas a greater mass extinction in open marine en-vironments than in near-shore environments, andextinctions were selective as is evident when spe-cies richness is divided by ecological proxies.

3.2.2. Ecological generalistsThis group includes a relatively small number

of species having a nearly global paleogeographicrange (V15^20 species, including heterohelicids,globigerinellids, hedbergellids, globotruncanellidsand guembelitrids, Plate I). All of these speciesare of relatively small size and simple morphol-ogy, and their tests have little or no surface orna-mentation. During the late Maastrichtian, thesmall biserial heterohelicids (Heterohelix globulo-sa, Heterohelix navarroensis, Heterohelix dentata)generally dominated (70^80%) planktonic fora-miniferal assemblages and hedbergellids werecommon. In the early Danian, many of these spe-cies were consistently present, though reduced toa few percent and generally dwarfed (V30^50%smaller than Cretaceous populations; Keller,1988; MacLeod et al., 2000). The exception arethe triserial Guembelitria species which were rarein open marine environments during the Maas-trichtian, but common to abundant in shallowrestricted environments, and dominated bothopen marine and shallow restricted environmentsin the early Danian. The consistent presence ofthese Cretaceous species in early Danian sedi-ments in Tunisian sections, as well as globally(MacLeod and Keller, 1994), indicates that thesespecies were survivors (see discussion above) aswell as ecological generalists able to tolerate sig-ni¢cant £uctuations in temperature, salinity, oxy-gen and nutrients.

Species richness of ecological generalists in thelatest Maastrichtian CF1 zone averaged 20 speciesin open marine and 14 species in restricted shal-low marine environments (Fig. 9C,D). In the earlyDanian P1a(1) zone, 15 and 11 species werepresent in these environments respectively. Thus,when viewed solely on the basis of species extinc-tions (ignoring the relative abundances of species),the mass extinction had a relatively small e¡ect onecological generalists. Moreover, there appears tohave been no signi¢cant di¡erence in the species

Fig. 9. K^T paleobiogeography of Tunisia based on species richness of Cretaceous planktonic foraminifera of inner neritic, mid-dle and outer shelf and upper bathyal environments. Pre- and post-K^T environments are compared based on averaged samplesof time slices in the upper zone CF1 (last 25^50 kyr of Maastrichtian) and earliest Danian zone P1a(1) (lower Parvularugoglobi-gerina eugubina zone, ¢rst 50^75 kyr of Danian. (Age estimates are based on the assumption of constant sedimentation rates andno hiatus.) Note that the major faunal changes in each species richness group occurred across the K^T boundary with no survi-vors among ecological specialists. In contrast, ecological generalists (e.g., small heterohelicids, hedbergellids, globigerinellids andguembelitrids) su¡ered the least with about 25% extinct at this time.

PALAEO 2758 1-5-02


extinction rate between open marine and shallowrestricted environments. Ecological generaliststhat disappeared at or near the K^T boundaryincluded various small heterohelicids (e.g., Hete-rohelix carinata, Heterohelix moremani, Hetero-

helix pulchra, Heterohelix labellosa, Heterohelixstriata).

3.2.3. Ecological specialistsThis proxy includes all tropical and subtropical

Table 3Depth ranking of planktonic foraminifera based on stable isotopes (+) and morphology

Surface Subsurface

v6 Guembelitria cretacea+ v Heterohelix glabrans+v6 danica v planata+v6 irregularis+ v pulchra+v6 trifolia+ v Globotruncanella petalloidea+v6 Heterohelix globulosa+* v subcarinatus+v6 dentata* 7 Globotruncana aegyptiaca+v6 navarroensis+ 7 arca+v labellosa 7 conica+v? punctulata 7 falsostuarti+v striata+ 7 duwiv Pseudoguembelina costulata+ 7 dupeublei

excolata+ 7 insignisv? kempensis 7 mariei7 palpebra+ 7 rosetta7 hariaensis 7 Globotruncanita angulata+7 Planoglobulina brazoensis+ 7 conica+7 carseyae 7 stuarti+7 Pseudotextularia deformis+ 7 stuartiformis+7 Rosita contusa+ 7 Abathomphalus mayaroensis+7 Rugoglobigerina rugosa+ 7 intermedius7 rotundata+ 7 Globotruncanella citae+7 scotti+ 7 Rosita patelliformis7 hexacamerata 7 plicatav? macrocephala 7 wal¢shensis7 milamensis 7 Pseudotextularia elegans+7 pennyi 7 Racemiguembelina fructicosa+7 reicheli 7 powelli+7 Plummerita hantkeninoides 7 intermedia+

7 Planoglobulina multicamerata7 Gublerina acuta+7 cuvilieri+7 robusta

Surface or subsurfacev Hedbergella monmouthensis+*v holmdelensis+*v6 Heterohelix globulosa+*v6 dentata*v Globigerinelloides aspera+v yaucoensisv volutus

Some species may have adapted to surface waters in shallow environments and subsurface waters in deeper open marine environ-ments as indicated by their isotopic ranking as well as geographic distribution (*). Species are grouped into ecological generalists(v) able to tolerate wide variations in temperature, salinity, oxygen and nutrients; some of these can be classi¢ed as ecologicalopportunists (6) able to thrive in adverse conditions; ecological specialists (7) are adapted to narrowly restricted environmentsand include most tropical-subtropical species, but also some taxa thriving in higher latitudes.

PALAEO 2758 1-5-02


Fig. 10. K^T paleobiogeography of Tunisia based on depth ranked species richness of planktonic foraminifera (see Fig. 9 forcomplete caption). Note that only surface dwellers survived the K^T mass extinction in either open marine or restricted marginalmarine environments.

PALAEO 2758 1-5-02


species (Plates II and III). They are characterizedby restricted paleogeographic range and generallynarrow tolerance limits for temperature, salinity,oxygen and nutrients. Ecological specialists aregenerally of large size, complex morphology,and with highly ornamented tests; they mayhave keels, ridges, spines, and generally largenumbers of chambers, large apertures, and mosthave heavily calci¢ed tests (e.g., globotruncanids,racemiguembelinids, planoglobulinids, rugoglobi-gerinids, pseudotextularids, Plates II and III).None of these species dominate foraminiferalpopulation during the Maastrichtian and their rel-ative abundances were generally less than 5% (Liand Keller, 1998a,b). The diversity of ecologicalspecialists was highest in tropical and subtropicalenvironments, but these species may have mi-grated outside these regions during times of cli-mate warming. As a result, they may be found astemporary incursions into higher latitudes duringwarm climates.

During the latest Maastrichtian zone CF1, spe-cies richness was dominated by ecological special-ists (V60%). An average of 37 ecological special-ist species were present in open marineenvironments and 21 in the shallow Gafsa Basin(Fig. 9E,F), but only four of these were consis-tently present (Fig. 9E, Plummerita hantkeni-noides, Rugoglobigerina reicheli, Rugoglobigerinarugosa, Planoglobulina carseyae, Keller et al.,1998). The other 17 species were sporadicallypresent and probably re£ect marine incursions.There were no survivors in this group; all dis-appeared at or before the K^T boundary. Thispattern characterizes the highly selective natureof the mass extinction in planktonic foramini-fera.

3.2.4. Species depth rankingDepth ranking of species into surface and sub-

surface (thermocline and deeper dwellers) basedon stable isotopes is a proxy for watermass strat-i¢cation. Species can be depth ranked based ontheir stable isotope values, though less than halfof the Maastrichtian species have been isotopi-cally depth ranked at this time; for the remainingspecies, depth ranking has been inferred frommorphological characteristics, which is therefore

more subjective (Table 3; discussion in Li andKeller, 1998a).

3.2.5. Ecological generalists ^ surface orsubsurface dwellers?

Most ecological generalists are surface dwellers,or able to live in either surface or subsurface con-ditions depending on the marine environment.Such species include the ecological generalistsHeterohelix globulosa and Heterohelix dentata,and possibly also Hedbergella holmdelensis, Hed-bergella monmouthensis and Globigerinelloidesyaucoensis. Other species which may also fallinto this group include the small, £at and thin-walled heterohelicids Heterohelix glabrans, Hete-rohelix. planata, and Heterohelix pulchra, and thesmall planispiral Globigerinelloides aspera, Globi-gerinelloides volutus, Globotruncanella subcarinatusand Globotruncanella petaloidea. Taxa which areprimarily considered as surface dwellers aremarked with an asterisk in Table 3 and includedas surface dwellers in Fig. 10.

3.2.6. Surface dwellers ^ ecological specialistsThis group is distinct from the surface dwelling

ecological generalists by their larger size, morecomplex and ornamented morphology, and gen-erally restricted paleogeographic distribution.They are distinct from subsurface dwellers inthat they include generally smaller morphologies,less heavily ornamented and thinner tests (e.g., allrugoglobigerinids, some large biserial species),and no heavily calci¢ed thickened keels (Plate II).However, there are exceptions; some keeled formssuch as Rosita contusa are isotopically light andhence surface dwellers.

Surface dwellers, with ecological specialists andgeneralists combined, were nearly half of the spe-cies assemblage (27^30 species) in open marineenvironments during the late Maastrichtian in Tu-nisia suggesting a well-strati¢ed water column.Though in the restricted Gafsa Basin, surfacedwellers dominated with 25 out of a maximumof 30 species (Fig. 10A). But 11 of the surfacedwellers were rare and only sporadically present(Keller et al., 1998). They probably re£ect an in-£ux of open marine species with periodic marineincursions into the shallow Gafsa Basin.

PALAEO 2758 1-5-02


Fig. 11. K^T paleobiogeography of Tunisia based on relative percent abundances of Cretaceous planktonic foraminiferal popula-tions grouped into ecological generalists and ecological specialists (see Fig. 9 for complete caption). Note that ecological special-ists were rare (6 5%) near the end of the Maastrichtian and did not survive the K^T boundary event, whereas ecological general-ists were abundant before and after the K^T event.

PALAEO 2758 1-5-02


Plate IV. Ecological opportunists. This group is characterized by the triserial guembelitrids and small biserial heterohelicids. Bothmorphotypes are small, thin-walled and have little or no surface ornamentation. All specimens from zone P0 at El Kef and AinSettara. Scale bar = 100 Wm.

1^5. Guembelina cretacea (Cushman)6. Guembelina danica (Hofker)7, 8. Guembelina irregularis (Morozova)9. Heterohelix navarroensis Loeblich10, 11. Heterohelix globulosa (Ehrenberg)12. Heterohelix dentata Stenestad

PALAEO 2758 1-5-02


Fig. 12. K^T paleobiogeography of Tunisia based on ecological opportunists grouped into biserial (heterohelicids) and triserial(guembelitrids) populations (see Fig. 9 for complete caption). Note that biserials dominated the latest Maastrichtian with lessthan 5% surviving into the early Danian. Opportunistic triserial species thrived only in shallow marginal marine environmentsduring the latest Maastrichtian, but dominated both open marine and restricted marginal settings in the early Danian.

PALAEO 2758 1-5-02


Fig. 13. K^T paleobiogeography of Tunisia based on relative percent abundances of depth ranked assemblages grouped into sur-face and subsurface dwellers (see Fig. 9 for complete caption). Note that surface dwellers dominated (s 90%) before and afterthe K^T event, whereas relatively few (5^10%) subsurface dwellers were present in open marine environments and none survivedthe K^T event.

PALAEO 2758 1-5-02


During the early Danian zone P1a(1), as manyas 15 Cretaceous species, all of them surfacedwellers and ecological generalists of the generaHeterohelix, Guembelitria, Hedbergella, Globigeri-nelloides and Pseudoguembelina (Pseudoguembeli-na costulata) may have survived in open marineenvironments (Fig. 10B, Table 3). Eleven of thesespecies may also have survived in the restrictedGafsa Basin; the exception are the globigerinellidswhich were rare and may not be survivors in thisenvironment (Keller et al., 1998).

3.2.7. Subsurface dwellers ^ ecological specialistsSubsurface dwellers are a distinct group char-

acterized by their heavily calci¢ed tests with extracalcite in test ornamentation, thickened keels andlarge size (Plate III). This group includes mostglobotruncanids, all racemiguembelinids and var-ious other large biserial and multiserial taxa(Table 3). As noted above, a few ecological gen-eralists may have been subsurface dwellers. Thesespecies are generally small and thin-walled andmay have been able to adapt to either surface orsubsurface environments (Table 3).

During the latest Maastrichtian zone CF1, sub-surface dwellers (including ecological generalists)were slightly more diverse than surface dwellers inthe open marine environments of Tunisia(Fig. 10C). This suggests a well-strati¢ed water col-umn. But there were only 10 subsurface dwellingspecies in the Gafsa Basin and all of these were rareor sporadically present, suggesting periodic marineincursions. There were no survivors in this group inthe early Danian in either open marine or restrictedshallow environments (Fig. 10D). This indicatesthat surface dwellers, and particularly the ecologi-cal generalists among them, were generally moreadapted for survival, probably because of theirgreater tolerance for changes in temperature, oxy-gen, nutrients and salinity.

3.3. Paleoecology based on relative speciesabundances

Overall, the relative percent abundance of aspecies or species group is a better proxy of envi-ronmental change than the presence or absence ofa species or species group. This is evident in a

comparison of the two types of proxies. For ex-ample, the strong species richness trends observedamong ecological generalists and specialists, orsurface and subsurface dwellers, are even morepronounced when the relative percent abundancesof the species are taken into consideration.

3.3.1. Generalists versus specialistsDuring the latest Maastrichtian zone CF1, the

relative abundance of ecological generalists inopen marine and restricted shallow basin environ-ments averaged over 95% of the total planktonicforaminiferal assemblages. In contrast, ecologicalspecialists (including surface and subsurfacedwellers) averaged less than 5% in open marine,and 6 2% in the Gafsa Basin (Fig. 11A,C). Thisindicates that already prior to the K^T boundaryevent, ecological specialists were a rare and en-dangered group with very high diversity andvery low numerical abundance. These overspecial-ized species were thus prone to extinction.

During the early Danian zone P1a(1) Creta-ceous ecological generalists decreased to 40^50%in open marine environments (Fig. 11B), and theremaining assemblage consisted of the evolvingearly Danian species. In the shallow restrictedGafsa Basin, the Cretaceous ecological generalistsremained dominant (s 90%). Ecological special-ists did not survive (Fig. 11D). This indicates thatalthough the K^T mass extinction was restrictedto ecological specialists, most Cretaceous general-ists also died out, though much later in the earlyDanian. Species populations of generalists de-clined dramatically in open marine environments,but not in the restricted shallow Gafsa Basin.Though this generalization is somewhat mislead-ing as is evident when the ecological generalistgroup is further evaluated below.

3.3.2. Ecological opportunistsEcological generalists were dominated by two

groups of ecological opportunists : (a) the smallbiserial heterohelicids generally tolerant of low-oxygen environments (Heterohelix globulosa, He-terohelix dentata, Heterohelix navarroensis, Pseu-doguembelina costulata) and (b) the very small tri-serial guembelitrids (Guembelitria cretacea,Guembelitria trifolia, Guembelitria irregularis,

PALAEO 2758 1-5-02


Guembelitria danica) generally thriving in highstress near-shore environments (Plate IV). Usingthese two groups as proxies reveals that the bise-rial opportunists dominated both in open marine(70^75%) and shallow restricted basins (60^80%)in Tunisia, but relative abundances are more var-iable in the latter (Fig. 12A). All biserials su¡eredstrong declines in the early Danian (from 70^75%to 6 5%, Fig. 12A,B) and all were extinct by theend of P1a or in P1c (MacLeod and Keller, 1994).This suggests that a well-strati¢ed ocean prevailedin CF1 with a well-developed oxygen minimumzone, but in the early Danian this ecological nichewas reduced probably as a result of a cooler well-mixed watermass.

The triserial opportunists are also revealing.During the latest Maastrichtian CF1 they wererare (6 2%) in open marine environments, butrather abundant in the shallow restricted GafsaBasin (20^40%, Fig. 12C). But in the early DanianP1a(1) (and particularly zone P0) they dominated,though still maintained a preference for shallownear-shore environments (90%) as compared toopen marine (50^80%, Fig. 12D). The amplitudedi¡erence in the £uctuations is probably due togreater competition with evolving Danian speciesin more open marine environments. The preferredenvironmental conditions of triserial guembelitridspecies are not yet well understood, though thereappears to be a high tolerance for salinity, nu-trient and temperature £uctuations. In the GafsaBasin guembelitrid dominance is associated with awarm humid climate, high rainfall, low salinityand high organic matter in£ux (Keller et al.,1998).

3.3.3. Relative abundances in depth rankedassemblages

The overall percent abundance of surface dwell-ers during the latest Maastrichtian was nearlythe same in open marine (90^95%) and the re-stricted Gafsa Basin (98%) and this group con-tinued its relative abundance into the early Dan-ian (Fig. 13A,B). As noted above, surfacedwellers before and after the K^T boundarywere dominated by di¡erent opportunistic taxa:the low oxygen tolerant heterohelicids thrived inopen marine environments and the guembelitrids

thrived in shallow marginal marine environments.Although this proxy suggests there was littlechange in the relative abundance of surface dwell-ers across the K^T boundary, in fact, guem-belitrids replaced heterohelicids (see Fig. 12). Incontrast, subsurface dwellers were a minor com-ponent of open marine (5^10%) environmentsduring the latest Maastrichtian and there wereno survivors in the early Danian (Fig. 13C,D).

Surface and subsurface dwellers thus re£ect rel-atively consistent high stress environments inopen marine as well as shallow restricted basinenvironments before and after the K^T boundary.Ecological opportunists suggest that in open ma-rine environments high stress conditions probablyincluded an expanding oxygen minimum zone,whereas in shallow restricted basins they includedsalinity, temperature and nutrient £uctuations.

4. Discussion

4.1. Species survivorship and reworking

Foraminiferal experts generally agree that amajor mass extinction occurred across the K^Tboundary in low to middle latitudes. But theydisagree about the nature of the mass extinctionpattern. Some workers contend that all but one tothree species became extinct as a result of thebolide impact and that the presence of other Cre-taceous species in Danian sediments is due to re-working (e.g., Olsson and Liu, 1993; Peryt et al.,1993; Olsson, 1997). Other workers contend thatmany more species survived, though they alsoagree that reworking is signi¢cant in Danian sedi-ments (e.g., MacLeod, 1996a,b; Luciani, 1997).

The survivorship of Cretaceous species has beendiscussed in many publications (MacLeod andKeller, 1994; MacLeod, 1996c; Keller, 1996),and also addressed in the El Kef blind test (e.g.,MacLeod, 1996a,b; Canudo, 1997; Masters,1997; Orue-Etxebarria, 1997; Keller, 1997; Ols-son, 1997; Smit and Nederbragt, 1997). At issuehere is not whether many Cretaceous species arepresent in Danian sediments ; nearly all workershave reported their presence, but whether they aresurvivors or reworked. Keller (1988) ¢rst noted

PALAEO 2758 1-5-02


that at El Kef the large ornamented tropical spe-cies disappeared at or near the K^T boundary,whereas the small weakly ornamented ecologicalgeneralists ranged well into the lower Danianzone P1a and appeared to be K^T survivors (seealso Keller et al., 1995). Since that time, this pat-tern has been substantiated in many low latitudesections worldwide and the question is no longerwhether, but how many, of the ecological general-ists survived. Current estimates range from as lowas three to ¢ve (Smit and Nederbragt, 1997; Ols-son, 1997) to as many as 16 species (e.g., Mac-Leod and Keller, 1994; Luciani, 1997, 2002;Apellaniz et al., 1997; Molina et al., 1998; Pardoet al., 2002; Karoui-Yaakoub et al., 2002).

Cretaceous species survivorship is also substan-tiated based on carbon and oxygen isotope mea-surements of species. In low latitudes, where thecarbon isotope shift is between 2^3x across theK^T boundary, many Cretaceous species thatlived in the Danian have a signi¢cantly greaternegative isotopic shift than those that lived inthe Maastrichtian (e.g., Barrera and Keller,1990, 1994; Keller et al., 1993). At higher lati-tudes, where the carbon isotopic change is small,this test is less reliable. In these sections, the con-tinued and consistent presence of certain Creta-ceous species in Danian sediments, but absence ofothers, is a good indicator of survivorship.

However, the stable isotope test for species sur-vivorship has its pitfalls and must be applied withgreat care. For example, recently Kaiho and La-molda (1999) claimed that, based on stable iso-tope measurements of individual species at Cara-vaca, Spain, there is no evidence of Cretaceousspecies survivorship. Details of their data, how-ever, reveal that the specimens analyzed were tak-en within the ¢rst 5 cm of the Danian zone P0 atthree intervals : at the K^T boundary, at 2 cm and5 cm above the boundary. This interval (zone P0)contains an abundance of reworked Cretaceousspecies as discussed by Canudo et al. (199l).Moreover, numerous studies have shown thatthe basal Danian zone P0 almost always containsmany reworked Cretaceous specimens, which gen-erally cannot be distinguished from in situ speci-mens, and hence should be avoided when testingfor Cretaceous survivors. Kaiho and Lamolda

(1999) thus unwittingly analyzed reworked Creta-ceous specimens and correctly obtained a Creta-ceous signal which they correctly interpreted asreworked. But they incorrectly concluded thattheir analysis of these reworked specimens pro-vided evidence against survivorship of Cretaceousspecies and for a catastrophic mass extinction ofnearly all species at the K^T boundary.

During the last decade, the argument for signif-icant survivorship among Cretaceous ecologicalgeneralists into the Danian (Keller, 1988, 1989;Keller et al., 1995) has gained much support,largely due to the accumulation of a global em-pirical database that documents the consistentpresence of Cretaceous ecological generalists inthe Danian (MacLeod and Keller, 1994; Keller,1993; MacLeod, 1996a,b; Luciani, 1997, 2002;Apellaniz et al., 1997; Molina et al., 1998). Inaddition, Tertiary stable isotope signals obtainedfrom individual Cretaceous species in Daniansediments have provided convincing evidence ofsurvivorship for many species (Barrera and Kel-ler, 1990; Keller et al., 1993). Although there isstill no agreement as to the total number of spe-cies that survived, about 15 species may now becounted as K^T survivors (Globotruncanella sub-carinatus, Globigerinelloides aspera, Heterohelixglobulosa, Heterohelix complanata ( = Heterohelixlamellosa), Heterohelix navarroensis, Heterohelixdentata, Heterohelix planata, Hedbergella mon-mouthensis, Hedbergella holmdelensis, Pseudo-guembelina costulata, Pseudoguembelina kempensis(?), Guembelitria cretacea, Guembelitria trifolia,Guembelitria danica, Guembelitria irregularis).

4.2. Pre-K^T extinction?

Still highly controversial is the pre-K^T speciesextinction pattern and, in fact, some workersquestion whether there is any foreshadowing ofthe boundary extinction event (Smit, 1982, 1990;Olsson and Liu, 1993; Molina et al., 1998; Apel-laniz et al., 1997; Luciani, 1977). It is generallyargued that the species which are shown to dis-appear below the K^T boundary at Elles I and IIand also at El Kef I and II, are simply extremelyrare, but in fact survived up to the boundaryevent. A time-consuming multiple hour search

PALAEO 2758 1-5-02


for each of these species in a sample just belowthe K^T boundary by two El Kef blind test in-vestigators is reported to have revealed at leastone specimen of each species (Olsson, 1997;Orue-Etxebarria, 1997). It is suggested that theserare occurrences of isolated specimens at the K^Tboundary prove that these species also survivedup to the K^T boundary event. However, no con-sideration has been given to the fact that isolatedspecimens may equally well be present due to re-working as is evident at Elles I and Elles II in theforaminiferal packstone. Even though the rework-ing argument is generally rejected for isolatedspecimens below or at the K^T boundary, thissame argument is commonly used to interpretthe presence of Cretaceous species in Danian sedi-ments as reworked.

In our paleobiogeographic distribution studywe avoided arguments regarding pre-K^T extinc-tions by taking the worst-case scenario, namelythat all species present in the CF1 time slice in-terval were extinct by K^T boundary time. Theargument regarding pre-K^T extinctions is un-likely to be solved based on the narrow intervalof 50^100 cm below and above the boundary thatmost workers choose to analyze and we used inthis study. Few workers have examined the envi-ronmental and faunal changes during the lateMaastrichtian. Though, stable isotope studiesdemonstrate profound climatic changes duringthe last 500 kyr of the Maastrichtian with max-imum cooling near the chron 30N/29R boundaryabout 500 kyr before the K^T boundary followedby rapid 3^4‡C warming between 200 and 400 kyrbefore the K^T boundary and cooling duringthe last 200 kyr of the Maastrichtian (Stott andKennett, 1990; Barrera, 1994; Li and Keller,1998a,b). Recent studies by Li and Keller(1998a,c) at El Kef and DSDP Site 528, by Abra-movich et al. (1998) in Israeli sections and at EllesII have demonstrated major biotic turnovers thatmark the progressive biotic e¡ects associated withthese rapid climatic changes.

5. Conclusions

Paleoecologic patterns of the K^T mass extinc-

tion in planktonic foraminifera in Tunisia, span-ning environments from open marine upper bath-yal, to shelf and shallow marginal settings,indicate a surprisingly selective and environmen-tally mediated mass extinction. This selectivity isapparent in all of the environmental proxies usedto evaluate the mass extinction, including speciesrichness, ecological generalists, ecological special-ists, surface and subsurface dwellers, whetherbased on the number of species or the relativepercent abundances of species. The following con-clusions can be reached for shallow to deep envi-ronments:

b About three quarters of the species disap-peared at or near the K^T boundary.

b Only ecological generalists, able to toleratewide variations in temperature, nutrients, salinityand oxygen, survived.

b Among the ecological generalists, only sur-face dwellers survived.

b Ecological opportunists survived (biserial andtriserial morphotypes).

b Only selected ecological opportunists sur-vived.

b Opportunistic biserial species thrived duringthe latest Maastrichtian in well strati¢ed open ma-rine settings, but dramatically declined in relativeabundances in the early Danian.

b Opportunistic triserial species thrived only inshallow marginal marine environments during thelatest Maastrichtian, but dominated both openmarine and restricted marginal settings in theearly Danian.

This highly selective mass extinction pattern re-£ects dramatic changes in temperature, salinity,oxygen and nutrients across the K^T boundaryin the low latitude Tethys ocean. Are these envi-ronmental changes solely the result of a majormeteor or comet impact on Yucatan at the K^Tboundary? Or are they the cumulative result ofrapid climatic changes, major volcanism and im-pact(s) across the K^T transition? Though an an-swer to these questions is beyond the scope of thisstudy, the single impact scenario can not explainwhy the ecosystem did not recover for severalhundred thousand years after the K^T boundary,or why high stress conditions began long beforethe K^T boundary. New studies of the Haiti and

PALAEO 2758 1-5-02


Mexican K^T sections suggest a multi-event sce-nario of impacts, volcanism and climatic changesbeginning in the late Maastrichtian and continu-ing well into the early Danian (Stinnesbeck et al.,1999, 2001; Stu«ben et al., 2002; Keller et al., inpreparation).

Acknowledgements

We thank Dr. M. Bel Haj Ali, Director of theTunisian Geological Survey, for hosting the 1998International Workshop on the K^T boundary inTunisia and for supporting the field excursion andDr. Habib Bensalem for arranging logisticalsupport and guidance for the field excursion whichmade collection of samples from Ain Settara andElles possible for participants. We are grateful tothe reviewers Dr. Robert W. Scott and Dr. W.J.Zachariasse for their many helpful suggestions.This study was supported by grants from NSFINT 95-04309, DFG Grant Sti 128/4-1 and theSwiss National Fund No. 8220-028367.

References

Abramovich, S., Almogi-Labin, A., Benjamini, C., 1998. De-cline of the Maastrichtian pelagic ecosystem based onplanktic foraminifera assemblage change implications forthe terminal Cretaceous faunal crisis. Geology 26, 63^66.

Abramovich, S., Keller, G., 2002. Planktic foraminiferal popu-lation changes during the Late Maastrichtian at Elles. Tuni-sia. Palaeogeogr. Palaeoclimatol. Palaeoecol. 178, 145^164.

Adatte, T., Keller, G., W. Stinnesbeck, 2002. Late Cretaceousto early Paleocene climate and sea-level £uctuations in Tu-nisia. Palaeogeogr. Palaeoclimatol. Palaeoecol. 178, 165^196.

Apellaniz, E., Baceta, J.I., Bernaola-Bilbao, G., Nun‹ez-Betelu,K., Orue-etxebarria, X., Payros, A., Pujalte, V., Robin, E.,Rocchia, R., 1997. Analysis of uppermost Cretaceous-low-ermost Tertiary hemipelagic succesions in the Basque Coun-try (Western Pyrenees): evidence for a sudden extinction ofmore than half planktic species at the K/T boundary. Bull.Soc. Ge¤ol. France 168, 783^793.

Barrera, E., 1994. Global environmental changes preceedingthe Cretaceous-Tertiary boundary early-late Maastrichtiantransition. Geology 22, 877^880.

Barrera, E., Keller, G., 1990. Foraminiferal stable isotopeevidence for gradual decrease of marine productivity andCretaceous species survivorship in the earliest Danian.Paleoceanography 5, 867^890.

Barrera, E., Keller, G., 1994. Productivity across the Creta-ceous-Tertiary boundary in high latitudes. Bull. Geol. Soc.Am. 106, 1254^1266.

Berggren, W.A., Kent, D.V., Swisher, C.C., III, Aubry, M.-P.,1995. A revised Cenozoic geochronology adn chronostratig-raphy. In: Berggren, W.A., Kent, D.V., Aubry, M.-P.,Hardenbol, J. (Eds.), Geochronology, Time Scales andGlobal Stratigraphic Correlation. SEPM Spec. Publ. 54,129^212.

Blow, W.A., 1979. The Cainozoic Globigerinindae. Brill, Lei-den, 1413 pp.

Burollet, P.F., 1956. Contribution a l’e¤tude stratigraphique dela Tunisie Centrale. Ann. Mines Ge¤ol. Tunis 18, 388.

Burollet, P.F., 1967. General geology of tunisia. In: Martin, L.(Ed.), Guidebook to the Geology and History of Tunisia.Petrol. Explor. Soc. Libya, 9th Annu. Field Conf., 67 pp.

Burollet, P.F., Oudin, J.L., 1980. Paleocene et Eocene en Tu-nisie; pe¤trole et phosphates; Ge¤ologie compare¤e des gise-ments de phosphates et de pe¤etrole; colloque international.Documents B.R.G.M. 24, 205^216.

Canudo, J.I., Keller, G., Molina, E., 1991. Cretaceous-Tertiaryboundary extinction pattern and faunal turnover at Agostand Caravaca, SE Spain. Mar. Micropaleontol. 17, 141^319.

Canudo, J.I., 1997. El Kef blind test I results. Mar. Micro-paleontol. 29, 73^76.

Caron, M., 1985. Cretaceous planktic foraminifera. In: Bolli,H.M., Saunders, J.B., Perch-Nielsen, K. (Eds.), PlanktonStratigraphy. Cambridge University Press, Cambridge, pp.17^86.

Galeotti, S., Coccioni, R., 2002. Changes in coiling direction ofCibicidoides pseudoacutus across the Cretaceous/Tertiarytransition of Tunisia: palaeoecological and biostratigraphicimplications. Palaeogeogr. Palaeoclimatol. Palaeoecol. 178,197^210.

Groot, J.J., De Jonge, R.B.G., Langereis, C.G., TenKate,W.G.H., Smit, J., 1989. Magnetostratigraphy of the Creta-eous-Tertiary boundary at Agost (Spain). Earth Planet. Sci.Lett. 94, 385^397.

Kaiho, K., Lamolda, M.A., 1999. Catastrophic extinction ofplanktonic foraminifera at the Cretaceous-Tertiary bound-ary evidenced by stable isotopes and foraminiferal abun-dance at Caravaca, Spain. Geology 27, 355^358.

Karoui-Yaakoub, N., Keller, G., Zaghbib-Turky, D., 2002.The Cretaceous^Tertiary (K^T) mass extinction in plankticforaminifera at Elles I and El Melah. Tunisia. Palaeogeogr.Palaeoclimatol. Palaeoecol. 178, 233^255.

Keller, G., 1988. Extinction, survivorship and evolution ofplanktic foraminifera across the Cretaceous-Teritary bound-ary at El Kef, Tunisia. Mar. Micropaleontol. 13, 239^263.

Keller, G., 1989. Extended period of extinctions across theCretaceous-Tertiary boundary in planktonic foraminiferaof continental shelf sections: Implications for impact andvolcanism theories. Geol. Soc. Am. Bull. l0l, 1408^1419.

Keller, G., 1993. The Cretaceous/Tertiary boundary transitionin the Antarctic Ocean and its global implications. Mar.Micropaleontol. 21, 1^45.

PALAEO 2758 1-5-02


Keller, G., 1996. The Cretaceous-Tertiary mass extinction inplanktonic foraminifera: biotic constraints for catastrophetheories. In: MacLeod, N., Keller, G. (Eds.), Cretaceous-Tertiary mass extinctions. W.W. Norton and Co., NewYork, pp. 49^84.

Keller, G., 1997. Analysis of El Kef blind test I. Mar. Micro-paleontol. 29, 89^93.

Keller, G., Lindinger, M., 1989. Stable isotope, TOC andCaCO3 records across the Cretaceous-Tertiary boundaryat El Kef, Tunisia. Paleogeogr. Paleoclimatol. Paleoecol.73, 243^265.

Keller, G., Barrera, E., Schmitz, B., Mattson, E., 1993. Grad-ual mass extinction, species survivorship, and longterm en-vironmental changes across the Cretaceous/Tertiary bound-ary in high latitudes. Geol. Soc. Am. Bull. 105, 979^997.

Keller, G., Stinnesbeck, W., Lopez-Oliva, J.G., 1994. Age de-position and biotic e¡ects of the Cretaceous/Tertiary bound-ary event at Mimbral, NE Mexico. Palaios 9, 144^157.

Keller, G., Li, L., MacLeod, N., 1995. The Cretaceous/Terti-ary boundary stratotype section at El Kef, Tunisia: howcatastrophic was the mass extinction? Paleogeogr. Paleocli-matol. Paleoecol. 119, 221^254.

Keller, G., Adatte, T., Stinnesbeck, W., Stu«ben, D., Kramar,U., Berner, Z., Li, L., Salis Perch-Nielsen, K., 1998. TheCretaceous-Tertiary transition on the Sahara platform ofsouthern Tunisia. Geobios 30, 951^975.

Keller, G., Adatte, T., Stinnesbeck, S., Stueben, D., Berner, Z.,2001. Age, chemo- and biostratigraphy of Haiti spherule-rich deposits: a multi-event K^T scenario. Can. J. EarthSci. 38, 197^227.

Keller, G., Han, Q., Adatte, T., Burns, S.J., 2001. Paleoenvir-onment of the Cenomanian-Turonian transition at East-bourne, England. Cretaceous Research 22, 391^422.

Kucera, M., Malmgren, B.A., 1998. Terminal Cretaceouswarming event in the mid^latitude South Atlantic Ocean:evidence from poleward migration of Contusotruncana con-tusa (planktonic foraminifera) morphotypes. Paleogeogr.Paleoclimatol. Paleoecol. 138, 1^15.

Li, L., Keller, G., 1998a. Maastrichtian climate productivityand faunal turnovers in planktic foraminifera in South At-lantic DSDP Sites 525A and 21. Mar. Micropaleontol. 33,55^86.

Li, L., Keller, G., 1998b. Diversi¢cation and extinction inCampanian-Maastrichtian planktic foraminifera of North-western Tunisia. Ecl. Geol. Helv. 91, 75^102.

Li, L., Keller, G., 1998c. Global warming at the end of theCretaceous. Geology 26, 995^998.

Luciani, V., 1997. Planktonic foraminiferal turnover across theCretaceous-Tertiary boundary in the Vajont valley (South-ern Alps, northern Italy). Cretac. Res. 18, 799^821.

Luciani, V., 2002. High resolutoin planktonic foraminiferalanalysis from the Cretaceous/Tertiary boundary at Ain Set-tara (Tunisia): Evidence of an extended mass extinction.Paleogeogr. Paleoclimatol. Paleoecol. 178, 299^319.

Lopez-Oliva, J.G., Keller, G., 1996. Age and stratigraphy ofnear-K/T boundary clastic deposits in northeastern Mexico.In: Ryder, G., Fastovsky, D., Gartner, S. (Eds.), The Creta-

ceous-Tertiary Event and Other Catastrophes in Earth His-tory. Spec. Pap. Geol. Soc. Am. 307, 227^242.

MacLeod, N., Keller, G., 199l. How complete are the K/Tbounary sections? Geol. Soc. Am. Bull. 103, 1439^1457.

MacLeod, N., 1993. The Maastrichtian-Danian radiation oftriserial and biserial planktic foraminifera Testing phyloge-netic and adaptational hypotheses in the (micro) fossil rec-ord. Mar. Micropaleontol. 21, 47^100.

MacLeod, N., Keller, G., 1994. Comparative biogeographicanalysis of planktic foraminiferal survivorship across theCretaceous/Tertiary boundary. Paleobiology 20, 143^177.

MacLeod, N., 1996a. Testing patterns of Cretaceous-Tertiaryplanktonic foraminiferal extinction at El Kef (Tunisia).Spec. Pap. Geol. Soc. Am. 307, 287^302.

MacLeod, N., 1996b. K/T redux. Paleobiology 22, 311^317.MacLeod, N., 1996c. Stratigraphic completeness and planktic

foraminiferal survivorship across the Cretaceous-Tertiary(K/T) boundary. In: Moguilevsky, A., Whatley, R. (Eds.),Microfossils and Oceanic Environments. University ofWales, Aberystwyth, pp. 327^353.

MacLeod, N., Ortiz, N., Fe¡erman, N., Clyde, W., Schulter,C., MacLean, J., 2000. Phenotypic response of foraminiferato episodes of global environmental change. In: Culver, S.J.,Rawson, P. (Eds.), Biotic response to Global Change: thelast 145 million years. Cambridge University Press, Cam-bridge, pp. 51^78.

Masters, B.A., 1984. Comparison of planktic foraminifera atthe Cretaceous-Tertiary boundary from the El Haria shale(Tunisia) and the Esna shale (Egypt). In: Proceedings of the7th Exploration Seminar, March 1984: Cairo, EgyptianGeneral Petroleum Corporation, pp. 310^324.

Masters, B.A., 1993. Re-evaluation of the species and subspe-cies of the genus Plummerita Bro«nimann and a new speciesof Rugoglobigerina Bro«nimann (Foraminiferidae). J. Fora-minifer. Res. 23, 267^274.

Masters, B.A., 1997. El Kef blind test II results. Mar. Micro-paleontol. 29, 77^79.

Molina, E., Arenillas, I., Arz, J.A., 1998. Mass extinction inplanktic foraminifera at the Cretaceous/Tertiary boundaryin subtropical to temperate latitudes. Bull. Soc. Ge¤ol. France169, 351^372.

Nederbragt, A.J., 199l. Late Cretaceous biostratigraphy anddevelopment of Heterohelicidae (planktic foraminifera). Mi-cropaleontology 37, 329^372.

Oberha«nsli, H., Keller, G., Adatte, T., Pardo, A., 1998. Dia-genetically and environmentally controlled changes acrossthe K/T transition at Koshak, Mangyshlak (Kazakstan).Bull. Soc. Ge¤ol. France 169, 493^501.

Olsson, R.K., 1997. El Kef blind test III results. Mar. Micro-paleontol. 29, 80^84.

Olsson, R.K., Liu, G., 1993. Controversies on the placement ofthe Cretaceous-Paleogene boundaryand the C/P mass extinc-tion of planktonic foraminifera. Paleogeogr. Paleoclimatol.Paleoecol. 8, 127^139.

Olsson, R.K., Hemleben, C., Berggren, W.A., Huber, B.T.,1999, Atlas of Paleocene Planktonic Foraminifera., Smith-sonian Contrib. Paleobiol. 85, 252.

PALAEO 2758 1-5-02


Olsson, R.K., Wright, J.D., Miller, K.G., 2001. Paleobiogeog-raphy of Pseudotextularia elegans during the latest Maas-trichtian global warming event. J. Foram. Res. 31 (3), 275^282.

Orue-Etxebarria, X., 1997. El Kef blind test IV results. Mar.Micropaleontol. 29, 85^88.

Pardo, A., Ortiz, N., Keller, G., 1996. Latest Maastrichtianand K/T boundary foraminiferal turnover and environmen-tal changes at Agost, Spain. In: MacLeod, N., Keller, G.(Eds.), The Cretaceous/Tertiary Mass Extinction: Biotic andEnvironmental Events. W.W. Norton and Co., New York,pp. 155^176.

Pardo, A., Keller, G., 1999. Aspectos paleoceanographicos ypaleoecologicos del Limite Cretacico/Terciario en la Penin-sula de Mangyshlak (Kazakstan): Inferencias a partir deforaminiferos planctonicos. Revista Espanola de Micropa-leontologia, 31 (2), 265^278.

Peryt, D., 1993. The Cretaceous/Paleogene boundary andplanktonic foraminifera in the Flyschgosau (Eastern AlpsAustria). Paleogeogr. Paleoclimatol. Paleoecol. 104, 239^252.

Robaszynski, F., Caron, M., Gonzalez Donoso, J.M., Won-ders, A.A.H., European Working Group on Planktonic Fo-raminifera, 1983/84. Atlas of late Cretaceous Globotrunca-nids. Rev. Micropale¤ontol. 26., l45^305.

Robin, E., Froget, L., Gayraud, C., Rocchia, R., 1995. Lesspinelles me¤te¤oriques a' la limite Cre¤tace¤-Tertiaire du sited’El Kef, Tunisie. International Workshop on Cretaceous-Tertiary Proceedings, El Kef section, Tunis 1992. Edition duService Ge¤ologique de Tunisie, O⁄ce National des Mines,Tunis, pp. 121^140.

Rocchia, R., Donze, P., Froget, L., Jehanno, C., Robin, E.,1995. L’iridium a' la limite Cre¤tace¤-Tertiaire du site d’El Kef

Tunisie. International Workshop on Cretaceous-TertiaryProceedings, El Kef section, Tunis 1992. Edition du ServiceGe¤ologique de Tunisie, O⁄ce National des Mines, Tunis,pp. 103^120.

Sassi, S., 1974. La se¤dimentation phosphate¤e au Paleoce'nedans le Sud et le Centre-Ouest de la Tunisie. The'se de Doc-torat e's-Sciences, Universite¤ Paris-Sud, Orsay, 292 pp.

Smit, J., 1982. Extinction and evolution of planktic fora-minifera after a major impact at the Cretaceous/Tertiaryboundary. Spec. Pap. Geol. Soc. Am. 190, 329^352.

Smit, J., 1990. Meteorite impact, extinctions, and the Creta-ceous/Tertiary boundary. Geol. Mijnb. 69, 187^204.

Smit, J., Nederbragt, A.J., 1997. Analysis of the El Kef blindtest II. Mar. Micropaleontol. 29, 94^100.

Stinnesbeck, W., Keller, G., Adatte, T., Stu«ben, D., Kramer,U., Berner, Z., Desremeaux, C., Moliere, E., 1999. Beloc,Haiti, revisited: multiple events across the Cretaceous-Ter-tiary transition in the Caribbean? Terra Nova, 11, 303^310.

Stinnesbeck, W., Schulte, P., Lindenmaier, F., Adatte, T.,A¡olter, M., Schilli, L., Keller, G., Stu«ben, D., Berner, Z.,Kramar, U., Burns, J., Lo¤pez-Oliva, J.G., 2001. Late Maas-trichtian age of spherule deposits in northeastern Mexico:Implication for Chicxulub scenario: Canadian Journal ofEarth Sciences 38, S. 229^238.

Stott, L.D., Kennett, J.P., 1990. The paleoceanographic andclimatic signature of the Cretaceous-Paleogene boundary inthe Antarctic: stable isotope results from ODP Leg 113.Proc. ODP Sci. Results 113, 829^848.

Stu«ben, D., Kramar, U., Berner, Z., Stinnesbeck, W., Keller,G., Adatte, T., Heide, K., 2000. Trace elements and stableisotopes in foraminifera of the Elles II K/T pro¢le: indica-tions for sea level £uctuations and primary productivity.Palaeogeogr. Palaeoclimatol. Palaeoecol. 178, 321^345.

PALAEO 2758 1-5-02


Date post:	10-Nov-2023
Category:	Documents
Upload:	princeton
View:	0 times
Download:	0 times