Late Cretaceous-Early Eocene Mass Extinctions in the Deep

GeologicalSociety of America SpecialPaper 247 1990

Late Cretaceous-earlyEocene mass extinctions in the deepsoa

Ellen Thomas Departmmtof Eanh and EnvironmentalSciences, Wesleyan University, Middletown Connecticut06457, and TlnmesScience Center,New London, Connecticut 06320

ABSTRACT

Upper Maashichtian through lowermost Eocene deep-seabenthic foraminiferal records from Maud Rise (Weddell Sea,Antarctica) demonstratethat there was no mass extinction of theseorganisms at the end of the Cretaceous.Ihere is no significantdrop in diversity acrossthe Cretaceous/Tertiaryboundary, butjust abovethis boundary there is a peak in relative abundanceof speciesthat may indicate low-nutrient conditions, probably reflecting the decreasein food supply to the ocean floor resulting from the large-scaleextinction of surface-dwellingprimary producers. In contrast, there was a global extinction of bathyal to abyssalbenthic foraminifera at the end of the Paleocene, occurring in fewer than 25,000yr at Maud Rise.Many benthicforaminiferal speciesthat had originated during the Cretaceousbecame extinct, although there was no coeval mass extinction (of comparable importance) of terrestrial organismsand planktonic marine organisms.After this extinction the diversity of benthic faunas on Maud Rise was low for about 260,000yr, and during the period of low diversity, the assemblages were dominatedby speciesthat may indicate the presenceof abundantorganic carbon, and possibly low concentrationsof dissolvedoxygen. The dominancezuggests that the Paleocene/Eocenedeep-sea benthic foraminiferal mass extinction was caused by a decreasein oxygen content of the waters bathing the lower bathyal reachesof the sea floor. Such a changecould have beencaused by a changein the circulation patternsof deep waters: these waters would becomedepleted in dissolvedoxygen if there was a change from predominant formation of deep waters at high latitudes (cooling and sinking) to initiation of, or a strong increaseof, formation at low latitudes(evaporation and sinking). Thus, one of the largest Phanerozoicextinctions at the Earth's zurtaceis not reflectedby the deep-waterforaminifera, and the largest Cenozoicextinction event in the bathyal-abyssalrealm of the oceansis of little importanceto surfacebiota: even someof the largestextinction eventsthat we know do not reachall environmentsof the Earth.

INTRODUCTION "buffer to extinction"(Sheehan and Hansen,1986; Arthur and others,1987), although some authors suggest that bunowing or- At the end of tle Cretaceous,landdwellers and surface- ganismsunderwent a massextinction (Wright lt Hsti and others, dwelling organismsin the oceansunderwent one of the largest 1984,p. 335).Deepwater ostracodes have been reported to have extinctionevents of the Phanerozoic(e.g., Thierstein, 1982; Cle- had a "faunal crash" at the end of the Cretaceous(Benson and mens,1982; Russell, 1982), but extinctionrates in deep-seaben- othen, 1984),but few data areavailable for faunasliving just thic organismsare not well known (Culver, 1987; Thientein, after that "crash,"so mass-mortalitypattems for that group have 1982;Hsii, 1986).Benthic organisms in the deepoceans have not been well established(Steineck, personal communication, beensaid to showlittle or no changeacross the Cretaceous,/Ter- 1989;Benson and otlers, 1985, Fig. l). tiary boundaryQlsii, 1986);detritus feeding has been seen as a Benthicforaminifera, which supplythe mostabundant fos- Thomas, E., 1990, l,ate Cretaceous-early Eocene mass extinctions in the deep se4 lz Sharpton, V. L., and Ward p. D., eds., Global catastrophesin Earth history; An interdisciplinary conference on impacts, volcanism, and mass mortality: ceological Societybf America Special yapr j.+7.

481 482 E. Thomas

sils of deep-water organisms,were reportedly little affectedby the (65"9.629'5,Io12.296'E, present water depth2p14 m) were mass extinction at the end of the Cretaceous (Douglas and drilled on Leg ll3 (January-March1987) on Maud Rise,an Woodruff, l98l; Thientein,1982; Culver, 1987),but this obser- aseismicridge at the eastemend of the Weddell Sea (Barker vation is based on few quantitative data sets. Many earlier andothers, 1988; Fig. l). Site689 is on the northeasternside of worken on benthic foraminifera described the great similarity of the ridge near its crest,Site 690 is on the southwesternflank, Maastrichtian and Danian (lower Paleocene)faunas (e.g., Cush- I 16 km to the southwestof Site 689. LowermostMaastrichtian man, 1946). More recently, differences have been recognized, through Pleistocenebiogenic sediments were recoveredat both although estimatesof extinction rates vary widely (18 to 67 per- sites(Fig. 2).T\e UpperCretaceous through lower Eocenecon- cent species extinction; Beckmann, 1960; Webb, 1973; Beck- sists of calcareouschalks and oozes;fine-grained terrigenous mann and others, 1982; Dailey, 1983; Widmark and Malmgren, materialis presentin partsof the sectionat Site 690 (Barkerand 1988; Keller, 1988b).Several of the estimates(Beckmann, 1960; others,1988, p. 190-l9l). Webb, 1973; Beckmannand others, 1982) must be seenas max- Paleodepthsof the sitescould not be estimatedusing simple imum estimates,simply becausethey were derived from compari- thermal subsidencemodels because Maud Rise is an aseismic sons of faunal lists for the Maastrichtian and Danian. Therefore, ridge; benthic foraminiferalfaunas indicate latest Cretaceous- theseestimates include last appearancesthat occurred a consider- Paleocenedepths of 1,000to 1,500m for Site689, and 1,500to able time before the boundary. 2,000 m for Site 690 (Thomasin Barkerand others,1988; Environmental conditions at the end of the Paleocenecon- Thomas,1990). For severalsites drilled on ODP Leg 114(Sites trast with those at the end of the Cretaceous.At the end of the 698-702; seeFig. I for locations),paleodepths could be esti- Paleocene there were no extinctions among shallow-water and mated using simple thermal subsidencemodels; overall, these surface dwellen comparable in size to the extinctions at the end deptls showedgood agreementwith depthsderived from faunal of the Cretaceous: it was a period of below-average extinction data (Katz and Miller, 1990). Comparisonof the Maud Rise rates (Raup and Sepkoski, 1986). The diversity of marine plank- faunasand the Leg 114 faunasconfirms the depth estimateof tonic microorganisms such as dinoflagellates, calcareousnanno- 1,000to 2,000m for Sites689 and 690 duringthe lateMaastrich- plankton, and foraminifera was increasing after the middle tian-early Eocene.In this study the following bathymetricdivi- Paleocene(e.g., Oberhaensli and Hsii, 1986). At the sametime, sionswere recognized,in agreementwith Berggrenand Miller however, deep-seabenthic foraminifera underwent their largest (1989):neritic-<2OO m; upperbathyal-2O0 to 600m; middle known extinction of the Cenozoic (e.g., Beckmann, 1960; Braga bathyal-600 to 1,000m; lower bathyal-1,000 to 2,000 m; and others,1975;Schnitker,l9T9; Douglasand Woodruff, 1981; upper abyssal-2,000 to 3,0fi) m; lower abyssal) 3,000 m. 1-alsmaand Inhmann , 1984; Culver, 1987), and this extinction Therefore,both sitescan be placedin the lower bathyalinterval has remained unexplained. Some authors suggestthat primary for the tine periodstudied. productivity decreasedat the end of the Paleocene(Shackleton The biostratigraphicinformation was obtained from cal- and others, 1985), and this could have caused the extinction of careonsnannofossils (Pospichal and Wise, 1990a,b, c); only a deepwater dwellen; the suggestionhas not been widely accepted, few datum levelsof planktonic foraminiferawere reliable age however (Miller and others, 1987b; Katz and Miller, 1989). indicaton at thesehigh latitudes (Stott and Kennett, 1990a; One purpose of this study was to contribute to the knowl- Huber, 1990). In addition, data on the paleomagneticrecord *fabriC'ofthe edgeofthe extinction at the end ofthe Cretaceous wereprovided by Hamilton (1990) for the Mesozoic,and Spiess by collecting a quantitative data set on ranges and abundance (1990) for the Cenozoic.The stratigraphicinformation supplied patterns of deep-seabenthic foraminifera from Maud Rise (Wed- by all theseauthors is compiledin Figure2. dell Sea, Antarctica). Another purpose was to compare the In this chapter,dzta ue presentedfor the interval between changesin faunal composition of deep-seabenthic foraminifera at 140 and 260 meten below seafloor (mbsf) at Site 690 and 200 the CretaceouslTertiary (K/T) boundary (a time of collapse of to 260 mbsf at Site 689, correspondingto upper Maastrichtian the primary productivity; Arthur and others, 1987) with faunal (Nephrolithusfrequens Zone; Pospichal and Wise, 1990a) changesat the end ofthe Paleoceneat the samelocation, to asses throughlowermost Eocene (CP9; Pospichal and Wise, 1990c). whether the pattems of faunal changewere similar. This informa- Absoluteages were derivedfrom crossconelation of the paleo- tion should be important in evaluating whether mass extinctions magneticand calcareousnannofossil data with the geomagnetic reach all environments from the surface to the lower bathyal polaritytime scaleof Berggrenand others(1985). At Site689 areasof the ooeans,or whether thesetwo environments (and thus there are unconformitiesat the K/T boundary (Zone CPla, their inhabitants) are largely decoupled. severalhundred thousandsof yean), in the middle Paleocene (Zones CP4 through CP5), and in the topmost Paleocene MATERIAL AI\D METHODS throughlower Eocene(at leastZones CP9 throughCPI I about 6.6m.y.; Fig. 2). Thereis no Ir anomalyat thestratigraphic K/T Sites and Stratigraphy boundaryin Hole 6898, confirmingthe presenceof an uncon- Ocean Drilling Program (ODP) Sites 689 (64o31.009'5, formity (Michel and others, 1990). The upper Maastrichtian- 03"05.996'E, present water depth 2,080 m) and 690 lowermost Eocene record at Site 690 does not contain -''

Late Cretnceous-earlyEocene mrBSextinctions in the deep sea /183

Figure l. LocationofSites 689 and 690, and other sitesat high southernlatitudes drilled by the Deep Sea_Drilling Project and the OceanDrilling hogram (ODP). Sites698 through70+ were drilleC Ouring ODP kg 114.

unconformitiesdetectable at the presentlevel of biostratigraphic Berggrenand others, 1985, but late Paleocenein Aubry and precision,and an [r anomalywas detected at the locationof the others,1988). At Site690 the benthicfaunal events occurred at calcareousnannofossil boundary (Michel and others,1990; pos- the boundarybetween Antarctic foraminiferalZones AP4 and pichal and Wise, 1990b). The interval just above the K/T AP5, thoughtto be equivalentto the P6a/P6bboundary (Stott boundary was recognizedby the presenoeof the lowermost and Kennett, 1990a).The benthic extinction also occurredin Paleocenenannofossil zone CPla (with the rndexformBiscutum paleomagneticChron C24R and in calcareousnannofossil Zone sparsum;Pospichal and Wise, 1990b) and by an intervalcontain- CP8,almost exactly in the middleof the intervalbetween the first ing the lowermostPaleocene index speciesEoglobigeinafinga appearanceof Discoastermultiradiatus, the lower boundaryof andE. eobullordescombined with smallheterohelicids (Stott and that zone,and the fint appearanceof Tribrachiatusbramtettei Kennett,1990a). Sedimentation rates were estimated at Site690 thelower boundary ofthe subsequentzone CPga (Pospichal and using paleomagneticdata, resultingin a sedimentationof 14.4 Wise, 1990a).This placesthe age of the benthic extinction at m/m.y. for the uppermostPaleocene (Chron 24R). Sedimenta- about57.5 Ma, in the late Paleocene(in the time scaleof Aubry tion rates for the uppermostCretaceous are more dfficult to and others,1988), and at the Paleocene/Eoceneboundary in the derive,but Hamilton(1990) has suggested a sedimentation rate of zonalscheme of Berggrenand otlen (1935). about7.5 m/m.y. at Site690, and not muchdifferent for Site689 ' At the Maud Risesites the benthicfaunal event occurs at the (below the unconformityat the K/T boundary). samelocation in tle sectionas a major changein dl3c valuesin The location of the Paleocene/Eoceneboundary with re- bulk carbonate(Stott andothers, 1990) and in benthicforaminif- gard to biostratigraphiczonations is difiicult and often discussed era(Kennett and Stotq 1990). This isotopicevent had been corre- (Berggrenand others, 1985; Aubry andothers, 1988). The ben- lated with the Paleocene/Eoceneboundary (Miller and others, thic extinction had been reportedto occur at the boundaryof l987a,b; Shackleton,1986), and at Site690 it occurredat the planktonicforaminiferal zones P5 and P6a(i.e., in the late paleo- Paleocene,/Eoceneboundary in the zonal schene of Berggren cene,according to Berggrenand others,1985) by 1-alsmaand and others (1985), but clearly before the Paleocene/Eocene Lohmann(1983), but Boersma(1984) and Miller and othen boundaryas definedin Aubry and othen (1938); i.e., within (1987b)placed the eventcloser to the boundary,between zones Zone CP8, and preciselyat the planktonic foraminiferalzonal P6a and P6b (the Paleocene/Eoceneboundarv as defined in boundarybetween Zones AP4 andAP5 (equivalentto the bound- 484 E. Thomas

690B 690C Paleo- 6898 Paleo- magnetic magnetic tr tr tr tr IE data tr uI data z IJJ z IJJ z IJJ UJ .= uJ o = c Planktonic Calcareous o o o Planktonic Calcareous lr () o I E o tr o g g Foraminifera o IJJ IJJ o .c o IIJ o .C o Foraminifera Nannotossil o TE IJJ o tr o IE o- o o. o {annofossils z 140 uJ a cP 12 o 16 o cP9 22 IJJ ut st AP5 AP 6a z N 17 t4 o o a. FADA' o ? FAD A. IJJ australiformis .t 210 AP4 60 18 N wilcoxensis cP8 o berygeni 23 AP5 a\FAD A. prae E cP8 19 G FAD A. pentacamerata E J.l .c australitomis L ct I o ,: AP3 l !t 80 220 24 a u E 21 E cP6-? u o @ FAD A. mckannai cC o = AP4 "P". imitatus u .o I N I .o 2i cP 6-7 h-CP 2-3' o = to o AP 1a FAD ah 6l tr I co ds. inconstant IJJ 24 C) JJ 25 o6l AP1I i cpro = I o o A' orae ,0 J IA.FAD l a FAD S. Dseudo- bulloides 25 11 AP3 lpentacameratacP5 at) .9 6l L-roo rh o 26 a 12 ? l-A. mckannai p o z 220 AP2 c g ut G o F cP4 z N lo.,oo uJ F o 9- "P'. initatus o .E E 13 o oo q -o (t SC F AP 1b :cP_3- t! =o o a | -J ):N s cP2 :< : s (t 14 16.rno Eq. 27 (') E 240 S. inconstans o 250 I I J o AP'ta cP 1b (! I FADS.pseudo a O) Ldbuttoiaes ,.eP1e 15 N o cr 'AP C. daniae 6 o A. ma varoensisZone Zone 16 e) 28 o E 260 260 N c" Figure 2. Core recovery,biostratigraphy, and magnetostratigraphyat Sites689 and 690. The core recoverydata are after Barker and others (1988); data on the magnetostratigraphyfor the Cenozoicare after Spiess(1990), and for the Mesozoicare after Hamilton (1990).The nannofosil biostratigraphyis after Pospichaland Wise (1990a,1990b, 1990c), the planktonicforaminiferal biostratigraphy for the Cenozoicis afterStott and Kennett (1990a), and for the Mesozoicis afterHuber (1990). For planktonic foraminifera,Cenozoic datum levelsare given in the figure,because the proposedzones are not yet widely known or accepted. ary between Zones P6a and Pb6). It is difficult to judge whether 1988). This offset is almost 20 n at Site 690, more than at any sections across the Paleccene/Eocene boundary are complete, other site. In addition, the thickness of Chron 24R is $eater at becauseso many sections contain unconformities in this interval Site 690 than at any other DSDP or ODP site, and comparison and there is thus no obvious "standard complete section." The of the isotope records for Site 690 with those of the southern section at Site 690 appean to be the most complete section Atlantic sites (Shackleton, 1986) also suggeststhat the Site 690 available from all Deep Sea Drilling Project (DSDP) and ODP record is the thickest section acrossthis interval. In addition, the sites, if judged on the distance between the boundary between recovery was very good at that site (Fig. 2), and core disturbance nannofossil Zones CP8 and CP9, and the planktonic for- was minimal, with the exception of the interval of overlap be- aminiferal boundary between AP4 and AP5 (equivalent to tween Holes 6908 and 690C (Barker and others, 1988). The P6a/P6b). Theseboundaries were thought to be coeval (Berggren record at Site 689 is of much lower quality, because of the and others, 1985), but later it was realized that there is an offset presenceof several hiatuses (Fig. 2) and poor re@very in some between the two in more complete sections (Aubry and others, intervals. Late Cretaceous-earlyEocene massextinctions in the deep sea 485

Samplc preparation and data collcctian difficult to quantify.The faunasare generally very divene (com- monly >60 speciesper 300 specimens),with many rare species Samples(15 cm3) weretaken at intervalsof 1.5 m; addi- (<5 percenton the total fauna).The mostcommon species have tional samplesat distancesof 0.35 m were taken in intervalsin very long ranges,and the shorter-rangedspecies are rare; thus, which major changesoccurred. Samples were dried tt 75 "C, rangesof manyspecies that might be stratigraphicallyuseful can- soakedin Calgon,and washedthrough a sievewith openingsof not be determinedprecisely in a statisticallyvalid way, and pre- 63 pm;residues were dried at7soc.The sizefraction larger than cisetiming of many first and last appearancesis difiicult if not 63 pm was usedto obtain good representationof small species impossible.In addition,a first or a last appearanceof a speciesat (Thomas,1985; fthroeder andothen, 1987).The preservationof a specificsite may not representorigination or extinction:deep- benthicforaminifera is goodto excellentover the studiedinterval; seabenthic species migrate both geographicallyand bathymetri- thereis no dissolutionas observedfrom fragmentationand fluc- cally (Woodrutr, 1985; Kurihara and Kennett, 1988). In tuationsin planktonic/benthicratios, and the isotopicvalues do addition, the literaturecan not be easilyinterpreted because of not indicate recrystallization(see also discussionin Stott and major taxonomicconfrrsion in many taxa. Therefore,a simple othen,1990 and Kennett and Stott, 1990). statementabout how many percentof all speciesof deep-sea At the startof the study,rarefaction curves were drawn for benthicforaminifera became extinct at a specifictime is equivo- somesamples (plots of numberof speciesvenus number of spec- cal: "extinction" ratesare rates of local last appearances,not imens)to determinethe samplesize needed to recovermost of tle necessarilyof extinctions(which areglobal by definition).In this speciespresent. The curvesbecame parallel to the specimenaxis chapterI disregardedall speciesthat occur in one sampleonly, at about 270 specimensin the more diversesamples, about 200 and then countedfint and last appearancesin all samples.All of specimensin the lessdiverse samples; about 300 specimenswere thesefirst and lastappearances (also of rarespecies) are included pickedfrom all samples.Part of eachsample was spread in a tray in TablesI and,2. to estimatehow much materialwould be neededto collect300 specimens,and then a split wasmade of the estimatedsize. The DISCTJSSIONOF RESIJLTS taxonomywas discussed and all raw data(counts) were presented togetherwith rangecharts in Thomas(1990). The most used The recordof late Maastrichtianthrough Eocene deep-sea taxonomicreferences for the Cenozoicwere Plummer(1926), benthicfaunal events from Site690 is morecomplete than that at Berggrenand Aubert (1975), and Morkhoven and othen (1986); Site 689, so the recordat the former site was usedto determine for the Mesozoic,references were Cushman(1946), Dailey thesequence offaunal events. The fragmented record ofSite 689 (1983),and Nyong and Olson (1984). waslater correlatedto the morecomplete Site 690 record.Faun- Calcareousbenthic foraminifera dominated in all samples, al events(last appearances and first appearances)clearly were not and calcareoustaxa were placedin morphologicalgroups. The spreadout evenlyover time, but wereconcentrateAatafew times three groups distinguishedare: (1) the spiral group (including (Fig. 3). The extinctionat the end of the Paleoceneis the most most trochospiraland someplanispiral species); (2) the biserial- significantevent for benthicforaminifera in the period from late triserial group, including speciesthat belongin the superfamily Maastrichtianthrough early Eocene,in contrastto planktonic Buliminacea(to which the recentlow-oxygen/high-nutrient indi- taxa,where the extinctionat the end of the Cretaceousis by far catorssuch as bolivinids and uvigerinidsalso belong); and (3) the the most important (e.g.,Smit, 1982;Thientein, 1982;Keller, cylindrical group (uniserialspecies with a cylindrical shape). 1988a).At Site690, very few species(8.3 percent)last appear Thesemorphological groups were then compared with the classi- closeto the K/T boundary(Table 1), whereasat the shallower fication of morphologicalgroups as describedby Corlis and Site689, the percentageoflast appearancesis higher,but still not Chen (1988). The spiral group agreesclosely with the group of indicativeof a major catastrophe(12.7 percnnt;Table l). Of the epifaunalspecies listed by tlese authors,and tle triserial-biserial sevenspecies with a last appearancenear the K/T boundaryat group with the infaunalspecies. There are few dataon the envi- Site 690, only threehave a coevallast appearanceat Site 689: ronmentalpreference of the morphologicalgroup of cylindrical Coryphostomaincrassata, Praebalimina reussi, and Spiroplec- species,consisting of Stilostomelhspp., Pleurostomelh spp., and tamminaafr. spectnbilis. Coryphostoma incrassata bwme extinct uniseriallagenids (Thomas, 1985), because these species arerare worldwideat the end of the Cretaceous(Morkhoven and othen, in the recentoceans. Therefore these specimens were not included 1986);P. reussihadits lastappearance close to the K/T boundary in the countsof epifaunaor infauna"but wereplotted by them- at lowerbathyal Site 516 (Walvis Ridge, South Atlantic; Dailey, selves(see below). Thesecylindrical speciesmight be placedin 1983) but survivedthe boundaryat the upper bathyal El Kef the group of infaunalspecies in the future (Corlis, written com- section(Keller, 1988b).The UpperCretaceous guide fossil Boli- munication,1989) if this placementis supportedby additional vinoidesdraco draco became extinct at the K/T boundary(Hil- data.There is a significantconelation (p >97.5) betweenthe rela- termannand Koch, 1960; Morkhoven and others, 1986), but this tive abundancesof the infaunaland the cylindricalgroup in the is largelya neritic to upperbathyal species. The speciesoccurs in Maud Risesamples. a few samplesjust below the K/T boundaryat Site 689, but Faunalevents in deep-seabenthic foraminiferal faunas are thereis only onespecimen in onesample at Site690. Only one 486 E. Thomas

TABLE1. FIRSTAPPEARANCES (FAs) AND LAST APPEARANCE TABLE2. FIRSTAPPEARANCES(FAs) AND LAST (LAs)ACROSS TH E CRETACEOUS/TERTTARY BOUNDARY APPEARANCES(LAs) AcRoSS THE LATE PALEOCENE AT SITES689 AND 690' EXTINCTIONINTERVAL'

lnterval at 689 FAs LAs Interval at 690 FAs LAs Interval at 689 FAs LAs lnterval at 690 FAs LAs

0.5 m.y.after 2 5 0.5m.y. after 6 3 After ? ? 0.5 m.y.after 106 AcrossIVT 2 3 Across1(T 5 0 Acrossevent 0 18 Acrossevent o12 0.5m.y. before 6 3 0.5m.y. before 2 4 Before ? 2 0.5 m.y.before 010

Total 10 11 13 Total 10 28 *Note thatthere is a shortunconformity across the boundaryat Site -At Site 689 the length of a 1 m.y. interval across the boundary could 689. not be estimated because of the presenceof unconformities. Totalfaunal events at Site689: 22 (27.8percent). Total faunal events at Site 689: ? Totallast appearan@s over 1 m.y.around the l(T boundary:1j (19.9 Totallast appearancesover 1 m.y.around the event:>18 (35.2 percent). percent). Totaffaunal events at Site690: 20 (23.8percent). Total faunal events at Site 690: 38 (50.1 percent). Totallast appearances over 1 m.y.around the l(T boundary:7 (8.S Total last appearances over 1 m.y. around the e\€nt: 28 (37.3 percent). percent).

Numberof faunalevents Numberof faunal events Calcareous (o Calcareous -tr CN {annotossils -tr (o c}| (n o (, uo (, o (Jl 140rn 200ni 2L cP 12 3i. cP9 h o lx)t u z fr 'li \ u tt II \ U l+{+ : oum t\ 21Om cP8 *+ I cP8 x+r tr. o L lc o o IU -9 'l80m o f,zzom E o o 2 o o cP 6-7 u

3 = 4 o cP 6-7 o o o -CP 2-3' I I s lUUtn^^^ ! w a f zso- cP 1b 3 CL f CL o o o J o UH5 o 1z T ?20m 24Om o u o cP4 z z U N s .co _vr J_ ul 9 a

F C. daniae o Zone \ = site6eo 1 Site 689 2.64m 260m t Figure3. Numberof faunalevents plotted cumulatively versus sub-bottom depth for Sites690 (left) and 689 (right). The horizontal lines mark the position of the Cretaceous/Tertiary(K/T) and Paleo- cene/Eocene(P/E) boundariesas established by calcareousnannofossil biostratigraphy (Pospichal and Wise,1990a, 1990b, 1990c) and planktonic foraminiferal biostratigraphy (Stott and Kennett, 1990a). Notethat the section of Site689 is plottedat a differentdepth scale. The left curve(x) givesthe number of last eventsper sample,plotted cumulatively from the first samplestudied in this chapter;x marksa sampleposition. The right curue(+) givesthe someof first and last app€arances. Late Cretaceous-early Eocene mass extinctiow in the deepsea 487 species(Buliminn simplex)had its first appearance at the K/T from the least bioturbated intervals, and were taken boundaryat both sites. several lens of centimeters away from the boundary itself, above and below This patternoffaunal eventsat the K/T boundary doesnot the samples with high Ir contents (Michel and others, 1990). In conformto the patternduring a largecatastrophe (Table l, Figs. addition, there was little or no reworking of planktonic forami_ 3 and4);one would expectto seea recordof a large numberof nifera (which are much more common than benthics and easyto last appearances,followed by a periodoflow diversity,and clus_ recoglize as either Cretaceousor Tertiary) acrossthe boundary. teringoffint appearancesduring a periodofrecovery. Thereis a In contrast to the events at the K/T boundary, the pattems dron in diversity acrossthe K/T 11311 boundaryat both sites of faunal events and of diversity of deep-seabenthic foraminifera (Fig. 4), but this drop is not significantlylarger than the normal in the latest Paleocenecorrespond closely to the pattern expected fluctuationsin diversity.There is no concentration oflast appear_ for a major catastrophe:a precipitous drop in diversity followed angssat the boundary,nor of first appearancesjust above it: by a period of unusually low diversity (Fig. a); many last appear_ rather,a few first and last appearancesoccurjust below, across, ances at and just below the faunal boundary, followed by a andabove the boundary (Table l). Although thereis an increase period of many first appearances(Fig. 3,Tabti2y.Many species in the sumoffirSt andlast appearances in the interval closeto the (including Gavelinella beccaiiformis, Gavelinella hWhalu.s,Neo_ K/T boundary (especiallyat Site 6g9; Fig. 3), this period of flabellina semireticuhta, Neoflabellina jarvisi Bolivinoides delica- increasedfaunal tumover startedseveral trunAre* of thousands tulus, ffiramidina rudita, putknin coryelti, Aragonin velnscoensis, of yearsbefore the boundary,similar to what hasbeen described Titaxia paleocenica, Tritaxia havanensis,Gyroidinoides quadra_ for planktonicforaminiferal extinctions (Keller, l9g9). The lack tw Dorothia trochoifus, Neoeponideshiilebrandti and Neoepo_ of an interval with extinctionsat the boundary, and of first ap_ nides lunata) have a coeval last appearanceat both sites,but also pearancesjust aboveit, might be a resultof strong bioturbation at many other locations over a wide range of paleodepths in the acrossthe boundary(Barker and others,lgSg). This is improba_ Atlantic Ocean (Tjalsma and Lohmann, l9g3; Boersma,l9g4), ble,however, because the samplesused in this studywere selected the equatorial Pacific (Miller and others, l9g7b), and in the

Number of species Numberof species Calcareous Calcareous O.J O) @ Ul ('| ,lannolossils (! O) @ -: up (, (, 14An 2L 200ni u cP9 cP 12 o o U u z u o u I OUm ztum cP8 cP8 oL *'-,,-,r'-ft '"-'r o -9 "!80m -'" o (E * r'-* o (g 22Om o o = ':,]f;' o u = -9o cP 6-7 '-'-f lt -9o ,c 2OOm q t:: .Ct l 230m cP 1b CL r,------'a--' t o a. o cP5 7 o rj o ,-- '1. 220m o u z+um cP4 z 'r o U N \ o I.. o F -cP_3- G cP2 *!.---t' '?- s F 24Om "* o @ J .t 250m cP 1b E r- af:91t *-{t E C. daniae F o \ Zone site6eo * site68e 5 '=i ZOUM 26Om > +. Diversity(expresed IigT.t as.numberof speciesper 3fi) plottedvenus sub.bottom depth for Sites689 and Tecimens) 690. The horizontallines mark tie positionor tm ct trc**7r".tl"ry (K/T) and Paleoce.nelEocene (P/E) boudaries_asptlbtislredby iulor** nunnofosilbiostratigraphy (pospichal a-ndWise, 1990a, 1990b, 1990c) and -ofplanktonic foraminiferal Uiosuatlgraphy fffou"r, 1990;Stott and Kennetl 1990a);note that the section Site 6g9 is plottedat u oire.en"iJepil'scare.

I 488 E. Thomas

Biserial/Triserialspecies, o/o Biserial/Triserial species, o/o .-l N) L't Calcareous t\) cn ! Calcareous o('o(, o c ('lOCN Nannolossil! .'{ N }C ;={ ;{ {annotossilsrl ){ ;s }s )s 2l 140m 200ni u cP 12 o \-----._ cP9 U zu U o -? U 160m 21Om cP8 o cP8 -9 --'--*P-a o a Erao. 22Qm = o cP 6-7 o .i* o -9 u Il cP 6-7 (E o -(:P r-?,' 1 o 5!zuum ! 3230m cP 1b ! o ":::L -9o cP5 Il {_ t CL 220m I 2a0m E $ o cP4 z N c o -cP_3- u cP2 € (t 240m 250m cP 1b J 5 .^nOl ,t C. daniae s*e6eo Zone A- Site 689 zovm 260m Figure5. Percentageof specimensin the assemblagethat belongto infaunalspecies, as estimated from test morphology(Corlis and Chen,1988). The horizontallines mark the positionof the Cretaceous/ Tertiary (K/T) and Paleocene/Eocene(P/E) boundariesas establishedby calcareousnannofossil biostratigraphy(Pospichal and Wise, 1990a,1990b, 1990c)and planktonicforaminiferal biostratigraphy(Huber, 1990; Stott and Kennett,1990a); note that the sectionat Site689 is plottedat a different depthscale. southernoceans (Katz and Miller, 1988).The sameis true for concentrationsof organiccarbon (e.g., Corliss and Chen,1988; severalof the earliestEocene fint appearances,such as tlose of SenGupta and others,l98l; Caralp,1984;Lutze and Coulbourn, Abyssaminapoagi, Pulleniabulloides, Globocassidulina sabglo- 1984;Bernard, 1988). [t is not easyto distinguishbetween effects bosa,and Anomalina spissiformis. At Site 690, most of the last oflow oxygenand high nutrientsor organiccarbon because tlere appearancesoccuned within an interval of lessthan 25,000yr commonlyis a correlationbetween these two factors.According (usingthe time scaleof Aubry andothers, 1988, and paleomag- to Corlissand Chen (1988), there is a strongconelation between neticdata on the locationof Chron C24fromSpiess,in combina- percentageof Holoceneinfaunal speciesalong a depth transect tion with calcareousnannofossil data from Pospichaland Wise, from a few hundredsof metersto 4,000 m depth in the Norwe- 1990c).This is an unusuallyshort period for faunal eventsin gian Seaand the flux oforganic carbonto the seafloor; infaunal deep-seabenthic foraminifera, which are conservativeorganisms speciesdominate where the flux of organiccarbon is morethan 3 living in a (usually)conservative environment (Thomas, 1985, to 6 g'm-2'y1-1. 1986;Thomas and Vincent,1987; Miller andKatz,1987;Bol- At Site 690 there are no changesin preservationof the tovskoy,1987). faunasin the samplesacross the Paleocene/Eoceneboundary and Major differencesbetween the developmentsin the bathyal the K/T boundary,suggesting that the faunal changesare not environmentat Maud Riseat the K/T boundaryand in the latest artifactsof preservation.There are no dataindicating that Maud Paleoceneare obvious notjust in the frequenciesoffaunal events, Rise underwentstrong vertical motions (exceptgradual subsi- but also in the characterof the dominantspecies in the assem- dence);thus, changesin the epifaunal/infaunalratio cannotbe blages,especially ofinfaunal and epifaunal species (Figs. 5,6,7). explainedby depth fluctuationsof the sites.Epifaunal species Epifaunal speciesare dominantat locationswhere the oxygen dominatein the Cretaceouspart of the sections,although fluctua- contentof deepwaters is highandlor thereis a low concentration tions in relative abundanceof infaunal speciesoccur, and are of nutrients;infaunal speciesdominate in the presenceof high strongerat the shallowerSite 689. Just above the K/T boundary Late Cretarcous-emly Eocene mnss extinctions in the deep sea m Spiral species,To Spiral species,g6 Calcareous O Calcareous IQ (I --J tlannofossils (no(, \ RHH$' d'S u N d.{ 14Om z }t il 200rri q cP 12 cP9 o u 4 z U o o U 160m 21Om cP8 =-*_ cP8 o L u o c -9 o o

(t,5180m E Izzomo cP 6-7 z = o tr o o cP 6-7 ? B 4 o v(:P o r o "-. naua f 20Om ! CL =zJUm cP 1b o € E. o o UFC cl

zz9m o 24Om c cP4 N z o F -cP 3- .* .E E cP2 F o o 240m ,5 250m =--{ cP 1b =

E C. daniae m Zone E F* site6eo 260m 260m Figure 6. of specimensin the assemblagethat belongto epifaunalspecies, as estimated from test -Pelcentaqe morphology(Corliss and Chen,1988). The horizontallines maik the positionof the Cretaceous/ Tertiary (K/T) and Paleocene,/Eocene(P/E) boundariesas establisheriby .a*r** nannofossil biostratigraphy(Pospichal and Wise, 1990a,1990b, 1990c) and planttonic foraminiferalbiostratigraphy(Huber, 1990;Stott and Kennett, 1990a); note that thesection at Site689 is plottedat a difrer;t depthscale.

there is a pronouncedpeak in relative abundanceof epifaunal (Tjalsrnaand Lohmann,1983; Miller and others,l9g7b; Katz speciesat both sitesand a concomitant decreasein relativeabun_ andMiller, 1988)described high relative abundances of the epi_ danceof infaunal species.The peak is lessobvious at Site 6g9, faunal speciesNuttallides truempyi jwt after the extinctions.At possiblyas a resultof the unconformity acrossthe K/T boundary. Site690 the intervalof extremelyhigh relativeabundances of in- The relative abundanceof infaunal speciesthen recovers,and faunal speciesis very short (about 260,000 yr), and thus this increasesagain slightly above paleocene the upper/lower bound_ interval might not have been sampledin sectionswith much ary (Fig. 4,215 mbsfat Site690; pospichal andWise, 1990). A lower sedimentationrates, or it might not be representedin the largeincrease in the relative abundanceofthe infaunalspecies (to sedimentsin sectionswith unconformitiesor low recovery. about 85 percent) occurs at paleocene the level of the latest The relativeabundance of infaunalspecies decreases higher extinctions:during the period of very low diversity(Fig. 4) the in thesection at theMaud Rise sites, but remainsat higherlevels faunais dominatedby infaunal speciesof the Supirfamily Buli_ than in the lower part of the sectionthroughout the studied minacea(mainly the smallspecies Tappaninaselmensis, Bulimina interval(uppermost Paleocene-lowermost Eocene). The diversity simplex,Siphogenerinoides brevispinosa, andin a few samples did not fully regainthe high valuesof the late Maastrichtianani Aragoniaaragonenis; Fig. 5). earlyPaleocene, and reached its peakfor the Cenozoicduring the Such extremedominance by buliminid speciesshortly after earlymiddle Eocene(Thomas, 1990). the benthic foraminiferal extinction has not been described Thelast-appearance rates at theK/T boundaryat Sites6g9 before,but 'l;-alsma(1976) and Tjalsmaand Lohmann(19g3, and 690 (rememberthat theseare rates of local last appearances, Fig. 46) documenteda much less extremeincrease in relative and not necessarilyextinctions) resemble rates published for Tri- abundanceof buliminids at that time at Site 329 (paleodepth nidad(18 percentextinction; Beckmann, 1960) and preliminary 1750 m, FalklandPlateau), and Boersma(1994) describeda valuesfor centralPacific Site 465 and Walvis Ridge Sites525 decreasein specirnensize just after the extinction.other authors and527(Widmark and Malmgren, 1988; extinction rate of l0 to .----<-

490 E. Thomas

25 percent).In general,however, data on extinction rates of Kefsectionare about 50 percent(Keller, 1988b), and thus con- deep-seabenthic foraminifera are widely divergent,ranging from siderablyhigher than for Sites689 and 690; extinction at the about17 to 82 percentsurvivor species (Webb, 1973; Beckmann shallowerSite 689 appearsto be greaterthan at the deeperSite and others, 1982). This divergenceis probably partly due to 690 (Table l). This differencein last-appearancntlteaccording inconsistenciesin methodsof estimatinglast-appearance rates, as to depth is in agreementwith Beckmannand others'(1982) well as to differencesin taxonomicconcepts. For example,for observationthat there is more severeextinction in "Midway- DSDP Site 208 (Lord Howe Rise, off New Zealand),Webb type" (shelfto upperslope) faunas than in "Velasco-type"(lower (1973) estimatedan extinctionrate of 54 percentof the species, slopeand abyssalplain) faunasat the endof the Cretaceous. but he counted3@ specimensper sample-benthic and plank- The large extinction of planktonic speciesat the K/T tonic specimens.In the Maastrichtian,about 75 to 80 percentof boundaryhas been well documented(e.g, review by Thientein, the faunaconsists of planktonicforaminifera, so that fewer than 1982;Keller, 1988b; Smit and others, 1988); these data, in com- 100 benthicspecimens were counted. If the diversityat Site208 bination with data on carbonisotopic ratios in surfaceand bot- resemblesthat at Sites689 and 690, at least270 specimensare tom dwellers (Arthur and others, 1987; Zachosand Arthur, neededto obtainan estimateof the true diversityand representa- 1986;Zachos and others, 1989), show that the productivity in the tion of the majority of species(see METHODS). A reestimateof surfacewaters collapsed at the K/T boundary.The benthicfora- the extinctionrates, using Webb's (1973) tableswith presenoe- miniferal faunalchanges at the K/T boundaryat Sites689 and absencedata, results in an extinctionrate of 14 percent,with 40 690 areexactly the type ofchangesthat would be expectedto out of 106 speciCItoo rareto be useful. result from such a collapse:a disappearanceof someinfaunal On the other hand, part of the wide divergencein last- (high carbonflux) species(P. reussi C. incrassata),and an over- appearancerates is probably real-a result of different last- all increasein relative abundanceof epifaunal(low nutrient) appearancerates at difrerentdepths, with higherrates occurring at speciesjust after the boundary.The lack of a massextinction in shallowerdepttrs. Last appearancerates for the upperbathyal El benthicorganisms such as deep-water foraminifera, which prob- o/o Cylindrical species, Cylindrical sp€cies, o/o N Cn \| O Calcareous N(,l{ 6 Calcareous o(,o(Jl crou o \lannolossilr )s ;'q d's ds ;t U b{;qN ;s z 140m 200m u cP 12 o o { cP9 u U z /- r o ^--.-.---.-- g 160m 21Om cP8

cP8 U

L 180m Szzom -o cP 6-7 -9 ,(E o u 6 cP 6-7 o o -CP 2-?' o E * 200m u 6 23Om cP 1b =U 6 o .o J -9o .ct cP5 CL E o o a24Am c $zzom u z o cP4 2 N l o c .: =cP 3- u I € E cP2 o o 240m 250m = cP1b aogl t E F C. danlae @ Zone site'eo = F Site 689 260m 260m Figure7. Percentageof specimensin the asemblagethat belongto cylindricalspecies. The horizontal linesmark the positionof the Cretaceous/Tertiary(K/T) and Paleocene/Eocene(P/E) boundariesas establishedby calcareousnannofossil biostratigraphy (Pospichal and Wise, 1989a,b, c) andplanktonic foraminiferalbiostratigraphy (Huber, 1990;Stott and Kennett,1990a); note that the sectionofSite 689 is plottedat a differentdepth scale. Late Cretaceous-earlyEocene mass.extinctionsin the deep sea 491

ably subsistlargely as detritusfeeden, is in agreementwith the boundary(such as G. beccariiformrs)became extinct in the lar€sfi theory that detritusfeeding offers a bufferto extinction(Sheehan Paleocene;many of the speciesthat becameextinct wereefihr and Hansen,1986). In addition,bathyal to abysal benthicspe- nal species.These extinctions, however, have remainedunex- ciescommonly live in an environmentof very low food supply, plained(e.g., Culver, 1987).There is a maj61change in the and thusare well suitedto surviveperiods of low productivity. carbon isotoperecord at the sametime as the benthic fruml In the interval below the K/T boundary,there are fluctua- extinction (worldwide, Shackleton,1987; Miller and otherS tions in ratio of infaunal to epifaunalspecies (Thomas, 1990), 1987a;KaE and Miller, 1990),which had beeninterpreted as suggestingthat fluctuationsin productivity were common,and pos.siblyresulting from a global decreasein surfaceproductiviry may have led to expansionand contraction of the oxygen- (Shackletonand others,1985). Miller and others(1987b) and minimum zone. Therefore,many of the benthic foraminiferal Katz and Miller (1990),however, documented that the gradient specieswere able to survivethe evengreater fluctuation in pro. in 6l3C valuesbetween surface and deepwaten did notchange ductivity at the end of the Cretaceous.In my opinion, faunal significantlyduring this period (in contrastwith the situationat changesof deepseabenthic foraminifera at the end of the Cre- the K/T boundary;Zachosand Arthw, 1986),and thought that a taceous(small increase in relativeabundance ofepifaunal species, decreasein productivitycould not explainmore than a part of tbe and minor extinction,mainly of infaunalspecies) can be consid- observedchanges in the 613Crecords. They concludedthat th ered to be secondary,resulting from the collapseof surface largechanges in the 6l3C recordin the upperPaleocene probably productivity. The causeof KlT extinctionwas thus a surface reflect(at leastpartially) a changein 6l3C of meanocean wats event,whether it was a bolide impact (e.g.,Alvarez, 1986;this as a result of changesin the input or output ratio of organfo volume)or relatedto large-scalevolcanism (Officer and others, carbonto carbonatecarbon (Miller and Fairbanks,1985). 1987;and this volume).The effecson the lower bathyalfauna on Comparisonof the benthicfaunal events at the K/T bound- Maud Riseappear to be secondary,and there is no evidenceof a ary with those in the latest Paleocenesuggests that the major disturbanceof the deep-waterenvironment itself. Paleocene/Eoceneextinction of deep-seabenthic foraminiferal The situationin the latestPaleocene (planktonic foraminif- speciesdid not resultfrom a drop in surface-waterproductivity. eral ZonesP6t/b) wasvery different at that time therewas no The speciesthat becameextinct in the latestPaleocene had sur- extinctionof planktonicspecies comparable in sizeto the end- vived the collapseof productivity at the end of the Cretaceorq Cretaceousextinction, and diversitiesof calcareousnannofossils, and thus it appearsunlikely that they would becomeextinct as planktonic foraminifera, and dinoflagellateswere increasing the result of a much smaller drop in productivity in the late (Oberhaensliand flsti, 1986).At Maud Rise,calcareous nanno- Paleocene:it has been well establishedthat the extinction of fosils indicated maximum surface-watertemperatures at the planktonic taxa at the end of the Cretac€ouswas much more samelevel as the benthicforaminiferal extinction (pospichal, per- severethan any decreasein divenity during the Cenozoic.In sonalcommunication, 1989). The diversityof planktonicforami- addition,the Maud Risefaunal patlerns of benthicforaminifera at niferal speciesat Maud Rise increaseddramatically during the the time of Paleoceneextinction do not indicatea dccreasen late Paleocene,and remainedhigh during the early and early productivity: there is an increasein the relative abundanceof middle Eocene(Stott and Kennet! 1990a).Warm-water indica- infaunal(high organiccarbon) species, such as might be expected tor speciespenetrated to high latitudesin the southernAtlantic from an increasein productivity,or a decreasein oxygencontent Ocean(Oberhanesli and llsii, 1986;Boersma and othen, l98Z), of the deepwaters, resulting in lessoxidation of organicmaterial. and oxygen isotopic recordsindicate the strongestincrease in Thusit appeanthat the late Paleoceneevent was largely a deep temperaturesof the Cenozoicfor bottom waters and surface waterevent (affecting waters at lower bathyaldepths or deeper), water (Shackleton,1986; Oberhaensli and Toumarkine,1985; in contrastwith the K/T boundaryevenL which was largely a Oberhaensli,1986; Corliss and Keigwin, 1986;Miller andothers, surface-waterevent. This suggests that the causeof the latePalo 1987a;Prentice and Matthews,1988). In addition,it wasa pe- ceneextinction should be soughtin changesin the deepoceanic riod of leasttemperature difference between surface and bottom environment, and such changesare most likely circulation waters(Shackleton, 1986). These characteristics of the isotopic changes,which occurin the right time range(less than 25,000 yr) recordsare alsopresent in the isotopicrecords from Maud Rise for the late Paleoceneextinction. sites(Kennett and Stott, 1990; Stott and others, 1990), with the Many scientists,from Chamberlin (1906) through Hay strongestincrease in temperaturesofdeep and surface waters, and (1988),have suggested that the deepwaters of the oceansmay in the lowest deepto-surfacetemperature gradients at the time of the pasthave formed differently from the way in which theyform the benthicfaunal extinction. now, i.e.,by sinkingof dense,cold, well-oxygenated and nutrient- The Paleocene/Eocenebenthic foraminiferal extinction was depletedwaten at high latitudesin tle northernAtlantic (Worth- global (Beckmann,1960; Braga and others, 1975; Schnitker, ington, 1972) andat high southernlatitudes in the WeddellSea 1979;ljalsma and Inhmann, 1983;Miller and others,1987b; (Fosterand Carmack,1976).In the absenceof largepolar ice Katz and Miller, 1990),and representsthe largestCenozoic fau- caps,deep waters might haveformed by evaporationand forma- nal turnover in deepseabenthic foraminifera,larger than the tion of dense,warm, salty deepwaters (Brass and othen, 1982; K/T boundaryevent. Many speciesthat had survivedthe K/T Barron, 1987; Prenticeand Matthews, 1988). Severallines of 492 E. Thomas isotopic evidence,however, sr ggestthat deep to intermediate Eocene(Kennett and Stott, 1990).Miller and othen (1987b) watersformed at high latitudesduring the Late Cretaceous(Bar- suggestedthat deepwaters formed at highlatitudes during the late rera and others,1987; Banera and Huber, 1990) and the late Paleocene,and that circulationmay have changedin the early Paleocene(Miller and others, 1987b),even in the abseneeof Eoceneor at the Paleocene/Eoceneboundary. More recentdata largeice caps.A majorproblem in evaluatingthe evidencefor the (Katz and Miller, 1990;Miller and Katz, 1988)on materialre- existenceof largedeep-water masses of salty,warm water is the coveredon ODP l-eg ll4 in tle southemmostAtlantic indicate fact that the intermediatewaten (down to depthsof severalki- that during the late Paleoceneand early Eocenethe southern lometen) may have formed by sinking at high latitudes,while oceanswere filled with nutrient-depleted(i.e., young) bottom deeperwaten formedby evaporationand sinking at low latitudes water, which presumablyformed by sinking at high southern (e.g.,Manabe and Bryan, 1985; Hay, 1988,Fig. 5B).Thus, data latitudes.These authors also concluded however, that the south- from sitesat intermediatedepths (such as lower bathyalSites 689 ern supply of "young" deepwater was reducedor evenelimi- and 690) might indicateformation of deepwaters by sinking, natednear the Paleocene/Eoceneboundary (58 to 57 Ma), and while deeperbasins were filled with saltier, warmer bottom they agreedthat this circulation changecould have triggered waters. worldwidebenthic foraminiferal extinctions. Deep-seabenthic faunas at Sites689 and 690 were domi- Maud Rise,however, is currentlynot in the path of newly natedby epifaunalspecies during the lateMaastrichtian and early formed Antarctic Bottom Water. becausethe site is too far to- Paleocene,suggesting the existenceofwell-oxygenated waters at ward the east,and is bathed with the relatively Warm Deep lgwer bathyaldepths in the Maud Risearea; preliminary data on Water flowing into the Weddell Sea from the lndian Ocean the ostracodefaunas from Maud Risesupport the hypothesisthat (Seabrookeand others, l97l; Anderson,1975; Pudsey and oth- the bathyal waterswere well oxygenated(P. Steineck,written en, 1988).Therefore, data from the Maud Risesites may not be communication,1989). During the Paleocene,however, there indicative of conditionsat the hypotheticalPaleocene-Eocene wereseveral episodes in which the relativeabundance of infaunal sitesof formationof high-latitudedeep waters; recent deep waten speciesincreased, especially during the late Paleocene(see e.g., riseup aroundMaud Risefrom depthsof 1,500to 2,000m to the Fig.5, 210 mbsfat Site690, corresponding to the middlepart of surface.whereas bottom watersare formed in the northwestern the late Paleocene,about 6l Ma in the time scaleof Berggrenand end of the WeddellSea (Comiso and Gordon,1987). More data others, 1985). Theseevents culminated in the late Paleocene and precisestratigraphic correlations are neededbefore the exact extinction event of deep-seabenlhic foraminifera,when many extentof oxygen-poordeep waters can be evaluated.In my opin- epifaunalspecies that had survivedsince the Cretaceousbecame ion, however,the largebenthic faunal extinctionin the late Pa- extinct.These episodes can best be explainedby eitherthe begin- leoceneis best explainedby a major changein deepwater ning of, or the strongincrease in, formationof warm salinebot- formationalprocesses. Formation of warm, salty deepwater can tom waters,so that the volumeof thesewarm and salinewaters provide the circulationchange necessary to causethe observed increaseduntil their upper limit reached(at least)the levelsof faunalchanges. Sites689 and 690. Thesewaters would have a relativelyhigh temperatureat their formation,and thus a low oxygencontent. In CONCLUSIONS addition, cold oxygenatedwaters probably formed somewhere closeto the Maud Rise sites,so that they would not havehad l. The frequencyoflast appearancesand first appearances time to becomemore depleted in oxygenduring their shorttravel of deep-seabenthic foraminifera from Maud Rise(Weddell Sea, to the sites.Warm waiersformed at low latitudes,however, had Antarctica)and the divenity patternsindicate that therewas no to travel a long distancebefore reaching Maud Rise, and thus mas extinction of theseorganisms at the Cretaceous/Tertiary becameeven more depletedin oxygenby the time they anived boundary.A short increasein relative abundanceof epifaunal there.The faunasdominated by the speciesTappanina selmensis speciesjust after the boundarycan be explainedas a secondary can be seenas the Paleocene/Eoceneequivalent of more recent effectof the collapseof primary productivity. faunasdominated by bolivinidsor uvigerinids.Preliminary data 2. The frequencyoflast appearancesand first appearances, on the ostracodefaunas from Maud Riseshow the presenceof combinedwith the patternsof changesin diversityfor the latest non analogostracode faunas during the short interval of low- Paleocene,show that there was a massextinction of deep-sea diversitybenthic foraminiferal faunas; these ostracode faunas re- benthicforaminifera at that time (57.5 Ma). A largeincrease in semble(on the genericlevel) much youngerdeep-thermospheric relative abundanceof infaunal speciesjust after the extinction faunasfrom the Mediterranean(P. Steineck,written communica- suggeststhat the extinctionwas caused by a changein deep-water tion, 1989). circulation,and that moreoxygenated deep waters at lower bath- Oxygenand carbon isotoperecords from Maud Rise and yal depthswere replaced with warmer,less oxygenated waters. [t the southernOceans are in agreementwith this interpretationof is improbablethat the extinctionswere caused by decreasedpro- the benthicforaminiferal data. The benthicforaminiferal oxygen ductivity, becausethe speciesthat becameextinct had survived isotoperecord from the Maud Risesites suggests that production the almostcomplete collapse of primary productivityat the end of warm deep watersincreased during the earliestpart of the ofthe Cretaceous. Late Cretaceous-earl! Eocene mAssextinctions in the deep sea 493

3. Comparisonof the faunal recordsof deep-seabenthic Berggren,W. A., andAube( J., 1975,Pateocene benthonic foraminiferal biostra- foraminiferaacross the Cretaceous/Tertiaryboundary (mass ex- tigraphy,paleobiogeography, and paleoecologyofAtlantic-Tethyan regions; tinction at the surface,not in the deepsea) and the uppermost Midway-type fauna: Palaeogeography,Palaeoclimatology, Palaeoecology, v.18,p.73-192. Paleocene(mass extinction in the deepsea" not at the surface) Berggren,W. A., and Miller, K. G., 1989,Cenozoic srrggeststhat bathyaland abyssalbenthic eventhe largermass-extinction periods do not influ- foraminiferalzonation: Mioopaleontology, v. 35, p. 308-320. enceall the environmentson Earth,from the surfaceto the deep Berggren,W. A., Kent, D. V., Flynn,J. J., and Van Couvering,J. A., 1985, waters.Mass extinctions, in thesedifferent environments are ap- Cenozoicgeochronology: Geological Society of America Bulletin, v. 96, parentlynot related. p. 1407-1418. Bernard,J. M., 1986,Characteristic assemblages and morphologiesof benthic foraminiferafrom anoxic, ACKNOWLEDGMENTS organic-richdepositq Jurassic through Holocene: Journalof ForaminiferalResearch, v. 16,p. 207-215. Boersma,A., 1984, Oligoceneand other Tertiary benthic foraminifersfrom a Drilling at Sites689 and690 wasmade possible thanks to depth traversedown Walvis Ridge,DSDP Leg 74, southeastAtlantic, ,rt the effortsof the captainand crew of theJoides Resolution and Hay, W. W., and othen, Initial Repors of the Deep SeaDrilling Project, the technicalpersonnel from the OceanDrilling Volume 75: Washington, D.C., U.S. Govemment Printing Offrce, Program.I thank p. 1273-r3M. the scientificparty on l"eg 113 for their input, and USSAC-NSF Boersma,A., Premoli-Silva"I., and Shackleton,N. J., 1987, Atlantic Eocene for financial support.Stirling Ince and PeterGorgone were of planktonic foraminiferalpaleohydrographic indicators and stable isotope greathelp in word procesing,and Nina Siegaland Rex Garnie- paleoceanography:Paleoceanography, v. 2, p. 287-331. wicz in sampleprocessing. The manuscriptwas greatly improved Boltovskoy,E., 1987,Tertiary benthic foraminiferain bathyal depositsof the by commentsfrom A. Quatemary world ocean: Journal of Foraminiferal Research,v. 17, Boenmaand J. Zachos. p.279-28s. Braga,G., DeBiase,R., Grunig, A., and Proto-Decima,F., 1975,Foraminiferi RETERENCES CITED bentonici del Paleocenee dell'Eocenedella SezionePossagno: Schweize- rischePalamntologische Abhandlungen, v. 97, p. 85-l ll. Brass,G. W., Souitham,J. R., and Peterson,W. H., 1982,Warm salinebottom Alvarez,W., 1986,Toward a theoryof impactcrises: EOS (Transactions, Ameri- waterin theancient o@an: Nature, v. 296,p.620423. canGeophysical Union), v.67, no. 35,p. 649-658. Caralp,M. H., 1984,Irrpact de la matidreorganique dans des zonesde forte Anderson,J. 8., 1975,EcologSr and distributionof foraminiferain the Weddell productivit6sur certainsforaminifCres benthiques: Oceanologica Acta, v. 7, Seaof Antarctica:Micropaleontology, v. 21, no. I, p. 69-96. p. 509-515. Arthur,M. A., Zachos,J. C., andJones, D. S., 1987,Primary productivity and Chamberlin,T. C., 1906,On a possiblereversal of deepseacirculation and its the Cretaceous/Tertiaryboundary event in the oceans:Cretaceous Research, influenceon geologicclimates: Journal of Geology,v. 14,p.363-373. v.8,p.43-54. Clemens,W. A., 1982,Patterns of extinctionand survivalof the terrestrialbiota Aubry, M.-P., and six others, 1988, Paleogenechronology; An integratedap duringthe Cretaceous/Tertiarytransition, tz Silver,L. T., and Schultz,P. H., proach:Paleoceanography, v. 3, p. 707-7 42. eds.,Geological implications of impactsof largeasteroids and mmets on the Barker,P. F., and others,editors, 1988, Proceedings of the OceanDrilling pro, Earth:Geological Society of AmericaSpecial Paper l$, p. 4O7413. gram Initial Reports: College Station, Texas, Ocean Drilling program, Comiso,J. C., and Gordon,A. L., 1987,Recuning polynyas over the Cosmonaut v.113A,785p. Seaand the Maud Rise:Journal of GeophysicalResearch, v.92, no. C3, Barrera,E., and Huber,B. T., 1990,1897169, r3g1r2g, and Sr/Ca ratiosof p.2819-2833. Maestrichtianforaminifer species from the Maud Rise,Ocean Drilling pro- Corliss,B. H., and Chen,C., 1988,Morphotype pattems of Norwegiandeepsea gram lrg 13,rn Barker,P. F., and others,Proceedings of the OceanDrilling benthic foraminifera and ecological implications: Geology, v. 16, Programinitial reports:College Station, Texas,Ocean Drilling program, p.716-719. v. I l3B (in press). Corliss,B. H., and Keigwin,L. D., 1986,Eoc€ne-Oligocene paleoceanography, iz Barrear,8., Huber,B. T., Savin,S. M., andWebb, P. N., 1987,Antarctic marine Hsri, K. J., ed., Mesozoicand Cenozoicoceans: American Geophysical temperatures;late Campanianthrough early Paleocene:paleoceanography, UnionGeodynamics Series, v. 15,p. l0l-118. v.2,p.2148. Culver,S. J.,1987, Forarrinifer4n Lipps,J. H., ed.,Fossil prokaryotes and Barron,E. J., 1987,Eocene equator-to-pole surface ocean temperatures; A signifi- protists: Knoxville, Univenity of TennesseeStudies in Geology,v. 18, cant climateproblem?: Paleoceanography, v. 2, p. 729-740. p.169-211. Beckmann,J.-P., 1960,Distribution of benthonicforaminifera at the Cretaceous- Cusbman,J. A.,1946, UpperCretaceous Foraminifera of the Gulf coastalregion Tertiary boundaryof Trinidad (West Indies),ltt Reportof the 2lst Session, ofthe UnitedStates and adjacentareas: U.S. Geological Survey professional Norden;Part 5, The Cretaceous-Tertiaryboundary: Inlemational Geological Prpr 2M,241 p. Congress,p.57-69. Dailey, D. H., 1983,late Cretaceousand Paleocenebenthic foraminifen from Beckmann,J.-P., Bo[i, H. M., Kleboth,P., and Proto-Decima, F., 1982,Micropa- DeepSea Drilling ProjectSite 516, Rio GrandeRise, western South Atlan- leontologyand biostratigraphy ofthe Campanianto paleoceneofthe Monte tic, iz Barker,P. F., and othen, Initial Reportsof the Deep SeaDrilling Giglio, BergamoProvince, Italy: Univenita di padova,Memorie di Scienze ProjecqVolume 74: Washington,D.C., U.S. GovernmentPrinting Office, Geologische35, p. 9l-172. p.7s7-782. Benson,R. H., Chapman,R. E., and Deck,L. T., 1984,paleoceanographic events Douglas, R. G., and Woodruff, F., 1981, Deep sea benthic foraminifera,r'z and deepseaostracodes: Science, v.224, p. 1334-1336. Emiliani, C., ed.,The oceaniclithosphere; The sea:New York, John Wiley - , I 985, Evidencefrom the ostracodesof major eventsin the SouthAtlantic and Sons,v. 7, p. 1233-1327. and worldwide over the past80 million yean, rir Hsii, K. H., and Weissert, Foster,T. D., and Carmack,E. C., 1976,Temperature and salinity structure in the H. J., eds.,South Adantic paleoceanography:Cambridge Univenity press, WeddellSea: Journal of PhysicalOceanography, v. 6, p. 36-44. p.325-35O. Hamilton,N., 1990,Mesozoic magnetostratigraphy of Maud Rise,Antarctica, rz 494 E. Thomas

Barker,P. F., and others,hoceedings of the OceanDrilling program:Col- circulation and benthic foraminiferalchanges near the Paleocene,/Eocene legeStation, Texas, Ocean Drilling Program,v. I l3B (in press). boundary:Paleoceanography, v. 2, p. 7 41-761. Hay,W. W, 1988,Paleoceanography; A review for the GSA Centennial:Geolog- Morkhoven,F.P.C.M., van, Berggren, W. A., andEdwards, A. S., 1986,Cenozoic ical Societyof AmericaBulletin, v. 100,p. 193,$-1956. cosmopottandeepwater benthic Foraminifera: Par1 France, Bulletins Cen- Hiltermann,H., andKoch, W., 1960,Oberkeide Biostratigraphiemittels Foram- tresRecherches Exploration-Production Elf-Aquitaine Memoin I l, 421 p. iniferen, m Report of the 2lst Session,Norden; Part 5, Pre-euatemary Nyong, E. E., and Olsson,R. K., 1984,A paleoslopemodel of Campanianto micropaleontology:International Geological Congress, p. 69-76. lower MaestrichtianForaminifera in the North AmericanBasin and adjacent Hsii, K. J., 1986,Cretaceous/Tertiary boundary event, rn llsii, K. J., ed, Meso, continentalmargin: Marine Micropaleontology,v. 8, p. 437477. zoic and CenozoicOceans: American GeophysicalUnion Geodynamics Oberhaensli,H., 1986, l,atest Cretaceous-earlyNeogene oxygen and carbon SEries,v. 15,p.75-84. isotopicrecord at DSDP sitesin the Indian Ocean:Marine Mioopaleontol- Hsti K. J., and othen, 1984, Initial reportsof the Deep SeaDrilling projecg ogy,v. 10,p, 9l-l 15. Volume73: Washington,D.C., U.S.Govemment hinting Office,289 p. Oberhaensli,H., and llsii, K. J., 1986,Paleocene-Eooene paleoceanography, iz Huber, B. T., 1990,Maestrichtian planktonic foraminifer biostratigraphy of the Ilsii, K. J., ed., Mesozoicand CenozoicOceans: American Geophysical Maud Rise, Weddell Sea'Antarctica, Ocean Drilling ttoject l€g ll3, iz Union GeodynamicsSeries, v. 15, p. 85-200. Barker,P. F., and others,Proceedings ofthe OceanDrilling ProjecfiCollege Oberhaensli,H., and Toumarkine,M., 1985,The Paleoceneoxygen and carbon Station,Texas, Ocean Drilling Program,v. I l3B (in press). isotopehistory ofSites 522,523, and 524 from the cenrralSouth Atlantig rz Katz, M. R., and Miller, K. G., 1988,Paleocene to Eocenebenthic foraminiferal Ilsii, K. H., and Weissert,H. J., eds.,South Atlantic Paleoceanograpby: tumover, Atlantic sector,southern oceans: Geological Society of America CambridgeUnivenity Press,p. 125-147. Abtractswith Programs,v.20,p. A251. Officer,C. B., Hallam,A., Drakg C. L., andDevine J. D., 1987,late Cretaceous - , 1990,Early Paleogenebenthic foraminiferal assemblage and stable isotope and paroxysmalCretaceous/Tertiary extinctions: Nature, v. 326, no. 6109, compositionin the southernocean; Ocean Drilling ProgramIeg ll4, in p. 143-149. Ciesielski,P. F., and others,Proceedings of the Ocean Drilling project: Plummer,H. J.,1926, Foraminiferaof the Midway Formationin Texas:Austin, CollegeStation, Texas, Ocean Drilling Program,v. l14B (in press). Univenity of TexasBulletin 26114, l7l p. Keller, G., 19884 Extendedperiod of K/T boundary mas extinction in the Prentice,M. L., and Matthews,R. K., 1988,Cenozoic ice-volume history; Devel- marinerealm [abs.], lir Globalcatastrophes in Earthhistory; An interdircipli- opmentof a compsiteoxygen isotope recor* Gmlog5r,v. 16,p. 963-966. nary conferenceon impacg volcanism,and massmorlality, Snowbird Utah: Pospichal,J., and Wise, S. W., 1990a"Paleocene to middle Eocenecalcareous Houston,Texas, Lunar and PlanetaryInstitute Contribution 673, p. 88-89. nannofossilsof ODP Sites689 and690, Maud Rise,Weddell Seq iz Barker, - , 1988b,Biotic tumoveramong benthic forarrinifera across the Cretaceous/ P. F., and othen, Proceedingsof the OceanDrilling Program:College Sta- Tertiary boundary;El Kef, Tunisia: Palaeogeography,Palaeoclimatology, tion, Texas,Ocean Drilling Program,v. I l3B. Palaeoecology,v.6( p. 153-171. - , 1990b, Calcareousnannofossils across the K,/T boundary,ODP Hole - , 1989, ExtendedCretaceous/Tertiary boundary extinctions and delayed 690C,Maud Rise,Weddell Sea" r'z Barker, P. F., andothers, Proceedings of population changein planktonic foraminiferafrom BrazosRiver, Texas: the OceanDrilling Program:College Station, Texas, Ocean Drilling Pro- Paleoceanography,v. 4, p. 287-332. gram,v. ll3B. Kennetf J. P., and Stotq L. D., 1990,koteus and Proto-Oceanus;Paleogene - , l990q Maestrichtiancalcareous nannofossil bimtratigraphy of Maud Rise oceansas revealed from Antarcticstable isotope resuls, Ocean Drilling teg ODP Lrg I13, Sites689 and 6X), inBarke4 P. F., and othen, Proceedings I13, rlryBarker, P. F., andothen, Proceedings of theOcean Drilling Program: of the Ocean Drilling Program:College Station, Texas,Ocean Drilling ColegeStation, Texas, Ocean Drilling Program,v. I l3B (in press). Program,v. ll3B. Kurihara,K., andKennee J. P., 1988,Bathymetric migration of deep.seabenthic Pudsey,C. J., Barker, P. F., and Hamilton, N., 1988, Weddell Sea abyssal foraminiferain the Southwct Pacificduring the Neogene:Journal of Foram- sediments;A recordof Antarcticbottom waterflow: MarineGeolog5r, v. 81, iniferalResearch, v. 18,p.75-83. p.289-314. Lutze,G. F., and Coulboum,W. T., 1984 Recentbenthic foraminifera from the Raup,D. M., andSepkosh, J. J., 1986,Periodic extinction of familiesand genera: continentalmargin of northwestAfrica; Communitystructure and distribu- Science,v. 231,p. 833-836. tion: Marine Mioopaleontolqgy,v. 8, p. 361-401. Russell,D. A., 1982,A paleontologicalconsensus on the extinctionof the dino- Manabe,S., and Bryan, K., 1985, COlinduced changein a coupledocean- saun?,rz Silver, L. T., and Schule, P. H., eds.,Gmlogical implicationsof atmospheremodel and its paleoclimaticimplications: Journal of Geophysi- impactsoflarge asteroidsand cometson the Earth: GeologicalSociety of cal Research,v. 90, no. C6, p. I 1689-11707. AmericaSpecial Paper 190, p. 401-,105. Michel,H. V., Asaro,F., Alvarca W., andAlvarea L., 1990,Geochemical studies Schnitker,D., 1979,Cenozoic deepwater benthic foraminiferq Bay of Biscay,in of the Cretaceous/Ter@ boundary in ODP Holes 6898 and 69{J(.,in Montadert,L., and othen, Initial reporc of the Deep SeaDrilling Project, Barker,P. F., and othergProceedings of the OceanDrilling Project Collqe Volume 48: Washington, D.C., U.S. Government Printing Office, Statio4 TexagOcean D'riling Project v. I l3B (in press). p.377414. Miller, K. G., and Fairbanks,R. G., 1985,Oligocene-Miocene global carbonand Schroeder,C. J., Scot! D. 8., and Medioli, F. S., 1987,Can smallerbenthic abyssalcirculation changes, lin Sundquist, E., and Broecker,W. S.,eds., The foraminiferabe ignoredin paleoenvironmentalanalyses?: Joumal of Foram- carboncycle and atmmphericCO2; Naturalvariations Archean to Present: iniferalResearch, v. 17,p. l0l-105. AmericanGmphysical Union MonographSerieg v. 32,p.469-4f,l6. Seabrooke,J. M., Hufiord G. L., and Elder,R. B., 1971,Formation of Antarctic Miller, K. G., and Kata M. E., 1987,Oligocene to Miocenebenthic foraminiferal bottom water in the WeddellSea: Journal of GeophysicalResearch, v. 76, and abyssalcirculation changes in the North Atlantic: Micropaleontology, no.9,p.2l&-2178. v. 33,p.97-149. SenGupt4 B. K., t ee,R. F., and Mallory, S.M., 1981,Upwelling and an unusual - , 1988,Deepwater changesnear the Paleocene-Eoceneboundary; Stable assemblageof benthic foraminifera on the northem Florida mntinental isotoperesults from the SouthernOcean: Gmlogical Societyof America slope:Joumal ofPaleontology,v. 55, p. 853-857. Abstractswith Programs,v.2Q p. A251. Shackleton,N. J., 1986,Paleogene stable isotope events: Palaeogeography, Pa- Miller, K. G., Fairbants, R. G., and Mountain, G. S., 1987a,Tertiary isotope laeoclimatology,Palaeoecology, v. 57, p. 9l-102. synthesis,sea level history, and continentrl margin erosion:Paleooeanog- - , 1987, The carbon isotoperecord of the Crnozoiq History of organic raphy,v. 2,p. l-20. carbonburial and ofoxygenin the oceanand atmospherg fu Brooks,J., and Miller, K. G., Janecek,T. R., Kae, M. E., and Keil, D. J., 1987b, Ab),ssal Fleel A. J., eds.,Marine petroleumsource rocts: GeologicalSociety of Late Cretaceous-earlyEocene mass extinctions in the deep sm 495

LondonSpecial Publication 26, p. 423434. - , 1986, Changes in composition of Neogene benthic foraminiferal faunas in Shackleton,N. J., Corfield,R. M., andHall, M. A., 1985,Stable isotope data and equatorial Pacific and North Atlantic: Palaeogmgraphy, Palaeoclimatology, the ontogenyof Paleoceneplanktic foraminifera:Journal of Foraminiferal Palaeocology, v. 53, p. 47 4I. Researc\ v. 15, p. 321-336. - , 1990, late Cretaceous through Neogene deepsea benthic foraminifera, Sheehan,P. M., andHansen, T. A., 1986,Detritus fe€ding as a bufferto extinction Maud Rise, Weddell Sea, Antarctic4 inBarket, P. F., and others, koceed- at the end of the Cretaceous:Geology, v. ld p. 868-870. ings of the Ocean Drilling Program: College Station, Texas, Ocean Drilling Smit, J., 1982,Extinction and evolutionof planktonicforaminifera after a major Program, v. I l3B (in press). impact at the Cretaceous/Tertiaryboundary, iz Silver, L. T., and Schultz, Thomas, E., and Vincent, E., 1987, Equatorial Pacific deepsea benthic foraminif- P. H., ds., Gmlogicalimplications of impacs of largeasteroids and comets era; Faunal changes before the middle Miocene polar cooling: Geology, on the Earth:Gmlogical Society of AmericaSpecial Paper 190,p.329-352. v. 15, p. 1035-1039. Smit, J., Groot, H., de Jonge,R., and Smit, P., 1988,Impact and extinction Tjalsma, R. C., 1976, Cenozoic foraminifera from the South Atlantic, DSDP lrg signaturesin completeCretaceous-Tertiary (K/Q boundarysections [abs.], 36, in Barker, P. F., and othen, Initial reports of the Deep Sea Drilling iz Global catastrophesin Earth history;An interdisciplinaryconference on Projecl Volume 36: Washington, D.C., U.S. Government Printing Office, impacts,volcanism, and mas mortality, Snowbir4 Utah: Houston,Texas, p.493-s18. Lunar and PlanetaryInstitut€ Contribution 673, p. 182-183. ljalsma R. C.,and lnhmarin, G. P., 1983, Paleocene-Eocene bathyal and abyssal Spiess,V., 1990,Cenozoic magnetostratigraphy of ODP Leg I 13 drill siteson benthicforaminifera from the Atlantic Ocean:Micropaleontology, Special Maud Rise,Weddell Sea, Antarctica, ur Barker,P. F., and others,Proceed- Publication4,94 p. ingsof the OceanDrilling Program:College Station, Texas, Ocean Drilling Webb, P. N., 1973, Upper Cretaceous-Paleoceneforaminifera from Site 208, Program,v. ll3B (in press). Lord Howe Rise,Tasman Sea, DSDP l*g 21, in Burns,R. E., and others, Stott, L. D., and Kennet! J. P., 1990a,Cenozoic planktonic foraminifera and Initial Reportsof the Deep SeaDrilling Project,Volume 2l: Washington, Antarctic Paleogenebiostratigraphy; ODP Leg I 13, Sites689 and 6X), in D.C.,U.S. Government Printing Office, p.541-573. Barker,P. F., and othen, Proceedingsof the OceanDrilling Program:Col- Widmark, J. V., and Malmgren,B. A., 1988, Cretaceous/Tertiaryboundary; legeStation, Texas, Ocean Drilling Program,v. ll3B (in press). Benthonicforaminiferal changesin the deep sea: GeologicalSociety of - , 1990b,The paleoceanographicand paleoclimaticsignature of the Creta- AmericaAbstracs with Programs,v.20, p. 4223. ceous/Tertiaryboundary in the Antarctic;Stable isotope results from ODP Woodruff, F., 1985,Changes in Miocenedeepsea benthic foraminiferal distribu- l.eg ll3, rn Barker,P. F., and othen, Proceedingsof the OceanDrilling tion in the Pacific Ocean;Relationship to paleoc€anography,iz Kennett, Program:College Station, Texas,Ocean Drilling Program,v. ll3B (in J. P., ed., The Miocene Ocean; Paleoceanographyand biogeography: press). GmlogicalSociety of AmericaMemoir 163, p. 131-176. Stott, L. D., Kennett,J. P., Shackleton,N. J., and Hall, M. A., 1990,The Worthington,L. V., 1972,On the North Atlantic circulation:Baltimore, Mary- evolutionof Antarctic surfacewaters during the Palmgene;Inferences from land JohnsHopkins Oceanographic Studies, v. 6, p. I 10. the stableisotopic composition of planktonicforaminifera, ODP Leg I13, tz Zachos,J. C., andArthur, M. A., 1986,Paleoceanography ofthe Cretaceous/Ter- Barker,P. F., and others,Proceedings of the Oc€anDrilling kogram: Col- tiary boundaryevenq Inferences from stableisotope and other data:Paleo- legeStation, Texas, Ocean Drilling Program,v. I l3B (in press). ceanography,v. I, p. 5-26. Thientein, H. R., 1982, Terminal Cretaceousplankton extinctions;A critical 7.achos,J. C., Arthur, M. A., and Dean,W. E., 1989,Geochemical evidence for assessmenqrz Silver,L. T., and Schultz,P. H., eds.,Geological implications supressionof pelagicmarine productivity at the K/T boundary:Nature, of impacs of largeasteroids and comets on the Earth: GeologicalSociety of v.337,p. 6l-64. AmericaSpecial Paper 190, p. 385-399. Thomas,E., 1985,late Eoceneto Recentdeepsea benthic foraminifers from the Maruscnrr AccEprEDBy rHE Socrsry Ocrosnn 24. 1989 centralequatorial Pacific Ocean, rz Mayer,L., and others,Initial Reportsof the Deep SeaDrilling Program,Volume 85: Washington,D.C., U.S. Gov- emmentPrinting Office, p.655494.