Upper cretaceous planktic foraminiferal biozonation for the austra realm

Marine Micropaleontology, 20 ( 1992 ) 107-128

107

Elsevier Science Publishers B.V., Amsterdam

Upper Cretaceous planktic foraminiferal biozonation for the Austral Realm Brian T. Huber Department of Paleobiology, NHB-121, National Museum of Natural History, Smithsoman Institution, Washington, DC20560, USA (Received June 5, 1992; revision accepted August 28, 1992 )

ABSTRACT Huber, B.T., 1992. Upper Cretaceous planktic foraminiferai biozonation for the Austral Realm. Mar. Micropa,'em,tol., 20: 107-128. A new planktic foraminiferal zonal scheme is presented for subdivision of Upper Cretaceous pelagic carbonate sequences in the circum-Antarctic region. Definition of the zones and subzones is based study of foraminifera from 13 deepsea sections that were poleward of 50 °S paleolatitude and within the Austral Biogeographic Realm during Late Cretaceous time. The proposed biostratigraphic scheme includes seven Upper Cretaceous zones, with an average stratigraphic resolution of 4.4 m.y., and six subzones, which are all within the Maastrichtian Stage, with an average stratigraphic resolution of 1.4 m.y. The considerably higher resolution in the Maastrichtian Stage is a result of good foraminiferal preservation, availability of high quality magnetostratigraphic sections, and complete composite stratigraphic recovery in the Atlantic and Indian Ocean sectors of the Antarctic Ocean. Diminished resolution in the pre-Maastrichtian sediments of southern high latitude sections results from: ( ! ) incomplete recovery of the middle Campanian, lower Santonian and most of the Cenomanian-lower Coniacian intervals, (2) presence of local and regional hiatuses, (3) paleobathymetric shallowing with increasing age at some sites, resulting in impoverished older planktic assemblages, and (4) poorer preservation with increasing burial depth. Cross-latitude correlation of the Campanian and older austral sequences may be improved with future drilling by recove~ of sections that span existing stratigraphic gaps. Correlation of high latitude bioevents with chemostratigraphic events and their intercalibration with the magnetostratigraphy and the Geomagnetic Polarity Time oLatut"--'....... al~: ll~.~.u~.uA"'4 ¢,-.,.~uth,~*t,~Vu~.LL~.,,-,,,,-,,,,-.~,u----o---r'h .... ctratiaranhic .... resolution in existing high latitude sequences.

Introduction Reconstruction of the Cretaceous paleoenvironmental history of Antarctica and the surrounding oceans has been hampered by a poorly resolved chronostratigraphic framework, preventing accurate cross-latitudinal correlation of identified stratigraphic events. This situation vastly improved with the recent recovery of a number of Upper Cretaceous peCorrespondence to: B.T. Huber, Department of Paleobiology, NHB-12!, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA.

lagic carbonate sections during Ocean Drilling Program (ODP) cruises to the Atlantic and Indian Ocean sectors of the Southern Ocean (ODP Legs 113, 114, 119 and 120). For the first time, southern high-latitude foraminiferal datums have been integrated with good quality magneto- and chemostratigraphic records, enabling establishment of a reliable magnetobiochronologic framework particularly for late Campanian through late Maastrichtian time. Hence, the uncertainty in high to low latitude correlation of foraminiferal first and last appearance datums (FAD's and LAD's) has considerably diminished for this time interval.

0377-8398/92/$05.00 © 1992 Elsevier Science Publishers B.V. All rights reserved.

108

B.T.HUBER

However, magnetostratigraphic data are lacking for early to middle Campanian and older Cretaceous sections in the high latitudes, and thus, biochronologic resolution is significantly reduced in comparison. The increased number and quality of Upper Cretaceous carbonate sections from the circure-Antarctic region enables establishment of a more highly refined foraminiferal zonal scheme for the Austral Realm. The biozonation proposed in this study is based on compilation of planktic foraminiferal range data from five DSDP and eight ODP sites, all of which occupied pale.latitudes greater than 50°S during'the Late Cretaceous (Fig. 1 ). Some taxonomic identifications and datum levels have been revised as a result of re-examination of material from those sites.

90°W

900E

Southern high latitude Upper Cretaceous sections Foraminiferal samples analyzed during this study are from sites located on the Falkland Plateau (DSDP Sites 327, 511 ), Maud Rise, (ODP Sites 689, 690), Northeast Georgia Rise (ODP Sites 698, 700), Kergnelen Plateau (ODP Sites 738, 747, 748, 750), Naturalist° Plateau (DSDP Sites 258, 264), and Lord Howe Rise (DSDP Site 208; Fig. 1 ). The present day latitude, longitude, and water depth of each site are listed in Table 1. Most of these oceanic rises and plateaus originated as relatively shallow features during Early or middle Cretaceous time, but sank to middle to upper bathyal pale.depths by the late Maastrichtian. With a possible exception in middle CampanJan time, all sites iemained above the foraminiferal lysocline. The predominant lithologies at the austral sites are limestone or chalk, although some intervals at Sites 258, 327 and 511 contain a high terrigenous component. The stratigraphic record in the southern high latitudes is nearly complete for the uppermost Campanian-upper Maastrichtian, spotty and discontinuous in the upper Turonian-middle Campanian, and very poorly represented in the Cenomanian-middle Turonian (Fig. 2). A TABLE 1 Present day latitude, longitude, and water depth of DSDP and ODP sites discussed in the text LEG

180" Fig. 1. Pale.geographic reconstruction of the southern hemisphere continents during the late Maastrichtian (70 Ma) showing the location of high latitude sites that have yielded Late Cretaceous planktic foraminifera. Numbered locations refer to DSDP and ODP sites and SI denotes the location of Seymour Island. Stippled pattern outlined with a heavy line denotes land areas and thin line represents the 2000 m is.bath. Plate tectonic reconstruction from Scotese and Denham's (1988) Terra Mobilis program.

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UPPER CRETACEOUS PLANKTIC FORAMINIFERAL BIOZONATION

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Fig. 2. Lithostratigraphy and age ranges of Upper Cretaceous DSDP and ODP sections cored in the region ofthe Southern Ocean. Age assignments that have been revised in the present study are denoted by an asterisk.

middle Campanian disconformity extends throughout the region of the Southern Ocean. This Southern Ocean Hiatus has been associated with a shallowing of the CCD (Wise, 1983; Basov and Karashenninikov, 1983) and bottom current erosion related to opening of a marine connection between Australia and Antarctica (Huber and Watkins, in press). In-

completeness of the Cenomanian-Santonian foraminiferal record is due mostly to poor sample preservation or paleodepths that were too shallow for accumulation of pelagic carbonate sediments. The following is a summary of the lithostratigraphic, biostratigraphic, and, where a,vaUable, magnetostratigraphic information oh-

I I0

rained for each of the southern high latitude sites.

Falkland Plateau DSDP Hole 32 7A Although over 380 m of Cretaceous sediment was penetrated in DSDP Leg 36 Hole 327, most of the sequence was cored discontinuously and core recovery averaged only 50%. The section includes 52 m of upper CampanJan-lower Maastrichtian nannofossil chalk yielding abundant and very well-preserved foraminifera, a condensed 12 m interval of Santonian zeolitic clay bearing few moderately to poorly preserved foraminifera, and about 2 m of claystone with rare, poorly preserved foraminifera (Barker et al., 1977; Sliter, 1977). Major hiatuses span the upper Maastrichtian, middle Campanian, and Turonian-Coniaeian intervals (Fig. 2). Sliter (1977) was unable to identify any existing planktic foraminiferal zones in this sequence because of the absence of diagnostic marker species. Henoted that keeled planktic taxa, including Praeglobotruncana, Rotalipora and Globotruncana, and other morphotypes with ornate surface textures, such as Racemeguembelina, Pseudotextularia, Plummerita and Trinitella, are very rare or absent at Site 327. Instead, the assemblages are dominated by long ranging "simple" morphotypes (sensu Caron and Homewood, 1983), such as Heterohelix,

Globigerineiloides, Hedbergella, Archaeoglobigerina and Whiteinella and are low in species richness. Although several species of Rugoglobigerina were reported to occur in the upper Campanian-Maastrichtian interval (Sliter, 1977), these were subsequently placed in a new species, Archaeoglobigerina australis, by Huber (1990). Sliter ( 1977) described one new species, Globigerinelloides impensus, from Hole 327A and noted that it was restricted to the upper Campanian interval. The absence of numerous index taxa from the Upper Cretaceous sequence was attributed

B.T. HUBER

to the influence of cooler high-latitude surface currents over the Falkland Plateau site and formed the basis for recognition of the Austral Biogeographic Province (Sliter, 1977).

DSDP SiW 511 A 237 m thick sequence of Upper Cretaceous sediment was drilled at Site 511 of Leg 71, located 80 km southwest of Site 327. Core recovery was continuous and much improved over Site 327, averaging 65% in the Upper Cretaceous interval. The youngest Cretaceous unit is a 14 m thick nannofossil chalk ranging from late Campanian-early Maastrichtian in age (Wind and Wise, 1983) and bounded above by a hiatus that spans from the middle Maastrichlian through the upper Paleocene. Underlying; the chalk unit is a 10 m thick zeolitic claystone tha~ is nearly devoid of calcareous microfossils. Wise (1983) assigned this interval tc the upper Campanian. As at Hole 327A, mo~;t of the middle Campanian record is missing at Site 511 because of a major disconformity, perhaps resulting from a shallowing of the CCD (Wise, 1983; Basov and Krasheninnikov, 1983). The lower Campanian, on the other hand, is represented by a thick ( 137 m) and stratigraphically continuous sequence of mixed zeolitic and nannofossil claystone. Below this is a 33 m clayston¢ unit ranging from Santonian to late Coniacian in age, and followed by a disconformity that separates Coniacian sediments above from 10 m of Turonian claystone below. The oldest unit in the Upper Cretaceous sequence is an I 1 m thick claystone unit of late Cenomanian age. Disconformities separate this unit from the overlying Turonian claystone and an Albian calcareous chalk below. The magnetic polarity stratigraphy obtained by Salloway (1983) from the Upper Cretaceous cores of Site 511 cannot be used as a means of correlation with the Geomagnetic Polarity Time Scale (GPTS) because of uncertainties with magnetic chron assignments and conflicts in correlation with the microfos-

UPPER CRETACEOUSPLANKTIC FORAMINIFERAL BIOZONATION

si! biostratigraphy. Four normal and four reversed zones were recognized by Salloway in the upper Campanian-lower Maastrichtian section, but three of the reversed and one of the normal zones are represented by single samples. Salloway (1983) identified the long Cretaceous normal interval from Cores 71-51128 through -511-55, although the microfossil biostratigraphies of Wise (1983) and Krasheninnikov and Basov (1983) place the Santonian/Campanian boundary, which corresponds with the top of the long Cretaceous normal zone (Kent and Gradstein, 1985), within Core 71-511-41. Perhaps a reanalysis of the Site 511 magnetostratigraphy using a closer sample spacing would resolve some these discrepancies. Foraminiferal preservation is extraordinarily good in much of the Upper Cretaceous sequence at Site 511, as the shells are often transluscent and without evidence of secondary overgrowth or recrystallization. Planktic foraminifera are abundant in the upper Campanian-lower Maastrichtian nannofossil chalk, common in most of the Cenomanian, Turonian, and upper Santonian-lower Campanian sections~ but rare to absent in the Coniacianlower Santonian interval (Krasheninnikov and Basov, 1983). Planktic:benthic ratios are variable, and occasionally quite low in the Cenomanian-early Campanian samples. Where there is stratigraphic overlap between the Site 327 and Site 511 sections, the planktic foraminiferal assemblages are identical. Again, age diagnostic species are mostly lacking and no low latitude zones could be identified. Of the southern high-latitude Upper Cretaceous sections the sequence recovered at Site 511 is the longest and most complete. Hence, all of the planktic foraminiferal CenomanianCampanian biozones for the Austral Realm are based on biostratigraphic range data from this site. As is typical of the austral sections, total species richness is low throughout and the assemblages are dominated by non-keeled, longer ranging taxa. Species of Heterohelix, Globiger-

111

inelloides, Hedbergella and Archaeoglobigerina dominate most of the Upper Cretaceous assemblages at Site 511. Several species that were endemic to the Austral Realm, including

Archaeoglobigerina austraZis, Globigerinelloides impensus and Hedbergella sliteri, first appear in the upper Campanian sediments. Keeled planktie taxa are quite rare in the Cenomanian-lower Campanian sequence at Site 511 and altogether absent from the upper Campanian-lower Maastriehtian interval. Cenomanian samples have yielded weakly to non-earinate forms of Praeglobotruncana delrioensis, fragments of Rotalipora, but no specimens of Dicarinella. Very rare specimens of Praeglobotruncana stephani sporadically occur in lower Turonian samples. This species ranges below the first appearance of Marginotruncana marginata, which occurs in sediments assigned to the upper Turonian and ranges to the lowermost Campanian. Other bicarinate species occurring in relatively low abundance in the Santonian-lower Campanian section inelude Archaeoglobigerina cretacea, Globotruncana bulloides and G. linneiana.

Maud Rise Holes 689B and 690C of ODP Leg 113 were drilled 116 km apart on the Maud Rise (Fig. 1 ). Both sites recovered a nearly complete history of uppermost Campanian-Maastrichtian pelagic carbonate sedimentation and a good magnetic polarity record (Figs. 2 and 3 ). A 64 m thick sequence of foraminiferal-nannofossil chalk was recovered from Hole 689B above oceanic basalt (Barker et al., 1988). Recovery was low (33%) at this site because of the presence of chert stringers and nodules dispersed throughout much of the sequence. Foraminiferal preservation is good to excellent in all but the lowermost samples from this hole (Huber, 1990). Recovery in a 69 m section of chalk at Hole 690C (66%) was much better and foraminiferal preservation is excellent in most samples studied.

I 12

B.T. I-IUBER

SITE 690 65 ° S

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Fig. 3. Magnetobiostratigraphiccorrelationof planktic foraminiferalzonal marker species of Maastrichtian age from O D P sites689, 690, and 700 in the southern South Atlantic.Datums are placed at the levelof samples containing the marker taxa,and datum intervalsrepresentthe sampling uncertaintyfrom the sample in which the marker speciesfirstor lastoccurs to the next underlying or overlying sample in which the species is absent. Light stipplein recovery columns represents the amount of sediment recovered for each core. Dashed line depicts the level of the Cretaceous/Tertiary boundary. Data from IHamilton, 1990; 2Huber, 1990; SHuber, unpubl, data; #Haflwood and Clement, 1991; ~Huber, 1991.

UPPER CRETACEOUS PLANKTIC FORAMINIFERAL BIOZONATION

Z

Tethyan L2

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A. mayaroensis

A. mayaroensis

1| 3 Austral 4

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A. mayaroensis

Abathomphalux mayaroensis

G. gansseri

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G. subcarinatus G. petaloidea A. intermedius

G. aegyptiaca H. rajogopalani

G. havanensis

Globotruncanella havanensis

R. circumnodifer

G. havanensis

Z

< L Z

A. australis

G. calcarata

G. impensus

G. ventricosa

Globigerinelloides impensus

Archaeoglobigerina

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cretacea

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spp.

D. primitiva M. si~ali H. helvetica Ik: archaeocretacea R. cushmani R. reicheli R. brotzeni

Whiteinella baltica

F. maslakovae It. Iwlvetica W. archaeocretacea

Praeglobotruncana spp.

Rotalipom spp.

Fig. 4. Revised magnetobiostratigraphy of Site 208 based on reinterpretation of the magnetic polarity data of Keating et al. (1975). Planktic foraminiferal datums based on Webb (1973) and personal observation.

The Maud Rise holes are by far the best biostratigraphic reference sections yet obtained in the re on ot L,l~o , . , u , . , ~ . u ~,.~,,.. ,,.,. the Maastrichtian time period. Recognition of paleomagnetic reversal events for Subchrons C29R through C33N (Hamilton, 1990) enabled development of a high resolution age model for both sequences and precise age determinations of planktic foraminifer first and last appearance datums (Huber, 1990). Results demonstrate that many high-latitude datums are diachronous relative to the low latitudes, with several species (e.g.,

Pseudotextularia elegans, Globigerinelloides subcarinatus, Globotruncanella petaloidea, G. area and Globotruncana subcircumnodifer) having migrated from the low to high-latitudes, while at least one species (Abathomphalus mayaroensis) migrated from the south polar region equatorward (Huber, 1992; Huber and Watkins, in press). Huber (1990) proposed a new biostrati-

graphic zonation for the upper CampanianMaastrichtian in the Austral Realm (Fig. 4) ~,,~o..a

,.~,,!,~ o f , h ~ M a u ~ Ri~p ~t!.ldy ~ n d

comparison with Sites 327 and 511. The G. impensus Zone was defined based on the total range of the nominate taxon, although coting at the Maud Rise stopped before the FAD of G. impensus was recovered. Magnetcbiostratigraphic correlation of Sites 689 and 690 indicate that the LAD of this species is within upper Suochron C33N (Fig. 3). This is approximately the same age as the Campanian/Maastrichtian boundary using either the GPTS ofHaq et al. (1987), for which an age of about 74 Ma was determined (Huber, 1990), or the GPTS of Kent and Gradstein (1985), which would give an age of about 75 Ma for this datum (Huber, 199 la). On the other hand, Pospichal and Wise (1990) concluded that Campanian sediments were not reached-on the Maud Rise since no specimens of the Campanian nannofossil species Aspidal-

114

ithus parcus constrictus and Eiffellithus eximius were found in situ. They instead suggested that coring terminated in lower Maastrichtian sediments, probably close to the Campanian/Maastdchtian boundary. The upper and lower boundaries of the Globotruncanella havanensis Zone were redefined by Huber (1990) since the defining ta_xa used in Douglas's (1969) original definition are absent from the high-latitude sites (see next section). Keeled species are absent from the lower part of this zone, but these morphotypes make a conspicuous appearance in the upper part. The FAD ofA. mayaroensis is in the middle of Subchron C3 I R at both Maud Rise sites, providing an age estimation of 70.5 Ma for this datum using the GPTS of Kent and Gradstein (1985). The base of the A. mayaroensis Zone is used to delineate the early/late Maastrichtian boundary at the southern high-latitude sites, whereas Caron (1985) indicates a latest Maastrichtian age for this zone. The FAD of the nannofossil Nephrolithusfrequens occurs at nearly the same level as A. mayaroensis in both Maud Rise holes, and both species show a similar time-transgressive migration from the high to low latitudes (Pospichal and Wise, i 990; Huber, 1990; Huber and Watkins, in press). Northeast Georgia Rise ODP Site 698 Continuous rotary drilling in Hole 698A (ODP Leg 114) penetrated 72.5 m of Cretaceous sediment, but only 13.2 m of the section (18.2%) was recovered (Ciesielski et al., 1988). The sequence includes 28 m of lowerupper Maastrichtian nannofossil chalk containi~g occasional chert stringers and 44 m of upper Campanian-lower Maastrichtian limestone, also containing sporadic chert layers. Foraminiferal preservation is moderate in the chalk sequence, but poor in the limestone unit (Huber, 1991a). Because of poor recovery and lack of paleomagnetic data, Site 698 is not considered as an

B.T. HUBER

important reference section in the Southern Ocean region. Nevertheless, the zonal scheme defined for the Maud Rise sequence could be applied at Site 698, as the relative order of first and last appearances is the same (Huber, 199 l a). As at the other austral sites, assemblages from the G. impensus Zone and lower G. havanensis Zone are low in species diversity assemblages and dominated by Heterohelix spp., G. multispina and A. australis. Keeled morphotypes are completely absent from these intervals, wheras Rugotruncana circumnodifer and Globotruncana sp. cf. G. arca, appear in the upper G. havanensis Zone, and are followed by consistent occurrences of A. mayaroensis in the upper Maastrichtian. Globigerinelloides subcarinatus and G. petaloidea both make their diachronous first appearances within the A. mayaroensis Zone.

ODP Site 700 The Cretaceous sequence recovered from Leg 114 Hole 700B consists of a 158 m thick upper Turonian-upper Maastrichtian limestone that varies in amount and type of nonbiogenic constituents (Ciesielski et al., 1988 ). Recovery in this hole averaged 67%. Calcareous nannofossil and magnetobiostratigraphic correlations indicate that significant stratigraphic breaks occur in the upper and lower Campanian parts of the section, while a short hiatus occurs at the Cretaceous/Tertiary boundary (Crux, 1991; Huber, 1991a). Foraminiferal preservation ranges from moderate in the Maastrichtian sediments to poor or very poor in the Campanian and older samples (Huber, 1991 a). A well-defined magnetic polarity stratigraphy was obtained fr~n,, t~e Upoer Cretaceous section of Site 700 (Hailwood and Clement, 1991 ). Magnetobiostratigraphic correlation with the Maud Rise sites (Fig. 3) demonstrates regional synchroneity of planktic foraminiferal datums within the Atlantic sector of the Austral Realm. Of greatest biostratigraphic utility for the upper Campanian-Maastrich-

UPPER CRETACEOUS PLANKTIC FORAMINIFERAL BIOZONATION

tian interval are G. impensus (LAD in upper Subchron C33N near the Campanian/Maastrichtian boundary), R. circumnodifer (FAD in middle to upper Subchron C32N), A. intermedius and A. mayaroensis (FAD's in middle Subchron C3 IR) and G. subcarinatus (FAD in upper Subchron C3 I R). The FAD of P. elegans was not recorded at Site 700, as uppermost Maastrichtian sediments were not recovered (Crux, 1991 ). Planktic foraminiferal assemblages from the G. impensus, G. havanensis and A. mayaroensis Zones are identical to those from the other austral sites. The are dominated by A. austrails, heterohelieids and Globigerinelloides, and total diversity is quite low. Inasmuch as foraminiferal preservation is very poor in the older Campanian samples, species identifications and stratigraphic ranges are mostly uncertain. Only Laeviheterohelix pulchra, Hedbergella loetterli and Archaeoglobigerina cretacea have been identified with confidence (pers. observation). The Santonian/Campanian boundary is placed at about 460 mbsfbased on the LAD of Marginotruncana pseudolinneiana, which is within Subchron C34N. This species and other marginotruncanids occur in moderate abundance throughout the Santonian interval (pers. observation). The oldest microfossil-bearing sediments were dated as late Turonian based on the presence of Praeglobotruncana gibba, Dicarinella hagni and several species of Marginotruncana ( Premoli-Silva, 1991 ).

Kerguelen Plateau ODP Site 738 The upper 41 m of the Cretaceous sequence at Site 738 is composed of a calcareous chalk with occasional stringers of chert (Barron et al., 1989). This unit ranges from the late early through late Maastrichtian (wei and Thierstein, 1991; Huber, 199 lb). Foraminiferal preservation is moderate to good in the middle part of this unit, but poor in the upper and

| ]5

lower intervals owing to the more indurated nature of the sediment (Huber, 1991b). The Cretaceous/Tertiary boundary at this site is considered to be biostratigraphically complete (Thierstein et al., 1991 ). Underlying the chalk is a strongly lithified limestone containing poorly preserved or unidentifiable planktic foraminifera. This sequence was determined to range from the lower Turonian through lower Maastrichtian based on nannofossil content (Wei and Thierstein, 1991 ). Recovery in the chalk unit is low (49%), and the sequence is interrupted by a hiatus that truncates the base of the A. mayaroensis Zone. The late Maastric~.ian planktic foraminiferal assemblages are identical to those from the South Atlantic sector of the Austral Realm. Particularly noteworthy is that G. subcarinatus and P. elegans have the same order of appearance above the base of the A. mayaroensis Zone as elsewhere in the Austral Realm. Poor preservation has prevented recognition of foraminiferal zones below the A. mayaroensis Zone.

ODP Site 74 7 Cretaceous sediments were recovered from two holes at Site 747. Hole 747A penetrated 67 m of upper Campanian-Maastrichtian nannofossil chalk with a recovery of about 75%. Although the youngest Cretaceous sediments were assigned to the lower Maastrichtian by Quilty (1992), the presence ofA. mayaroensis in Section 120-747A-21X-I indicates that the lowermost part of the upper Maastrichtian was recovered (Huber, unpubl, data). Nonetheless, a hiatus spanning most of the upper Maastrichtian separates the top of Core 12021R from Danian sediments at the base of Core 120-20R. The oldest sediments at Hole 747A contain G. impensus and are therefore correlated with the upper Campanian (Quilty, 1992). An additional 41 m ofnannofossil chalk was rotary cored n t n t , l~ ,-,,,~, u,., ,,-.~ . . . . of this sequence was recovered owing to the difficulty with drilling through chert beds (Schlich et al., 1989 ). The latter interval ranges

116

from the lower Coniacian through upper Campanian, and is interrupted by significant disconformities spanning part of the upper Campanian, most of the lower Campanian, and from the upper Coniacian through upper Santonian (Watkins, 1992). Foraminifera are abundant throughout the Cretaceous section and preservation is generally good in Cretaceous samples from Hole 747A, but poor to moderate in samples from Hole 747C (Huber, unpubl, data). The faunal transitions at Site 747 parallel the other austral sites, with the LAD of G. impensus at approximately the Campanian/Maastrichtian bounda~T followed by the FAD of R. circumnodifer in the late early Maastrichtian and the ensuing appearances of G. area, A. intermedius and A. mayaroensis ( Quilty, 1992 ). The FAD of G. subco: inatas was not identified at Site 747 since most of the upper Maastrichtian is missing. Except for the occurrence of very rare Globotruncana falsostuarti, the Site 747 are typical of coeval assemblages recovered from the southern South Atlantic region. Late Campanian-early early Maastrichtian assemblages lack keeled morphotypes, and are dominated by A. australis, Globigerinelloides and heterohelicids, and the austral endemic species Hedbergella sliteri occurs throughout most of the lower Maastrichtian sequence.

ODP Site 748 A thick (~ 510 m) Cretaceous sequence comprised of glauconitic, bioclastic packstones, wackestones, and grainstones was penetrated in Hole 748C. Calcareous nannofossils indicate that the marine portion of the section ranges from early or middle Campanian through late Maastrichtian in age, and hiatuses occur within the upper Maastrichtian, middle Maastrichtian, middle to upper Campanian, apd at the base of the Campanian (Watkins, 1992). As the depositional environment was shallow marine *~hroughout, planktic foraminifera are very rare and composed of small,

B.T. HUBER

poor to moderately preserved heterohelicids, Globigerinelloides and hedbergellids (Quilty, 1992).

ODP Site 750 The Cretaceous section encountered at Site 750 includes 93 m of Maastrichtian nannofossil chalk underlain by 145 m of Santonianearly Maastrichtian calcareous chalk and 30 m of upper Turonian-lower Santonian marly calcareous chalk (Schlich et al., 1989). Chert stringers are dispersed throughout these sediments. Hiatuses are recognized at the Cretaceous/Tertiary boundary, between the upper and lowermost Campanian, between the upper Santonian and lower Coniacian, and below the upper Turonian (Fig. 2). The oldest sedimentary unit is composed of silty claystone that is lacking in calcareous microfossils. Recovery was low ( ~ 35%) in the rotary drilled middle and upper Maastrichtian interval, and diminished further in the older Cretaceous units following a switch to spot coring. Foraminiferal preservation is good in the Maastrichtian samples, but is generally poor in samples from below (Quilty, 1992). Maastrichtian planktic foraminiferal assemblages at Site 750 are identical to assemblages of the same age elsewhere in the Austral Realm and the species show the same stratigcaphic succession of appearances and extinctions. Following the extinction of G. impensus, assemblages consist primarily of heterohelicids, hedbergellids, Globigerinelloides and A. australis (Quilty, 1992). Double keeled taxa appear in the upper part of the lower Maastrichtian first with R. circumnodifer, followed by A. intermedius, with A. mayaroensis appearing in the upper Maastrichtian. The FAD of G. subcarinatus occurs above the FAD of A. mayaroensis, and P. elegans is restricted to the top of the Maastrichtian section. Identification ofpre-Maastrichtian faunas is incomplete owing to their poor preservation state. Nevertheless, observations by Quilty (1992) suggest that: ( 1 ) upper Campanian as-

UPPER CRETACEOUS PLANKTIC FORAMINIFERAL BIOZONATION

semblages are similar to those of the lower Maastrichtian except for the presence of G. impensus, (2) the upper Turonian-Santonian interval is characterized by Laeviheterohelix

pulchra, Globigerinelloides ultramicra, Archaeogiobigerina bosquensis, Costellagerina pilula, (3) keeled morphotypes including Concavotruncana algeriana, C canaliculata and C. imbricata are very rare in the Turonian-Santonian samples, and (4) Praeglobotruncana delrioensis occurs in the oldest foraminifer-bearing sediments in Core 120-750CI IW. The latter species identification is doubtful, as specimen preservation is very poor and there is no other microfossil evidence for a Cenomanian age for this core.

Naturaliste Plateau Sites 257, 258 and 264 all penetrated Upper Cretaceous sediments on the Naturaliste Plateau, but cores of this age at Site 257 are barren of planktic foraminifera, and thus are not discussed.

DSDP Site 258 A 411 m middle Albian to Santonian sequence was drilled at Site 258 (Davies et al., 1974). The Upper Cretaceous section at this hole is very incomplete, as recovery was low (~40%) and the entire upper SantonianMaastrichtian interval is missing owing to a disconformity (Fig. 2). The upper 149 m of the sequence is composed of Turonian-lower Santonian nannofossil chalk with occasional layers of silicified limestone. The Cenomanian sediment below this is only 2 m thick and consists of zeolitic clay. Herb (1974) reported that planktic foraminifera are common and well-preserved in most Coniacian-Santonian samples, but nearly absent and poorly preserved in the Turonianlowermost Coniacian interval. Well-preserved foraminifera were again recovered in the brief Cenomanian section. Keeled species comprise a conspicuous pro-

1 17

portion of the Coniacian-Santonian assemblages, though the dominant taxa include heterohelicids, hedbergellids, Globigerinelloides ehrenbergi and Archaeoglobigerina bosquensis. Herb (1974) identified keeled taxa Margino-

truncana marginata, M. coronata, A. cretacea, G. lapparenti, G. tricarinata (=G. linneiana ) and G. angusticarinata. The Cenomanianlower Turonian interval is mostly composed of hedbergellids and Globigerinelloides, but rare specimens of Praeglobotruncana stephani and P. algeriana were also identified (Herb, 1974).

DSDP Site 264 Hayes et al. (1975) recovered one core (Core 28-264-11 ) from DSDP Leg 28 Hole 264 containing 8 m of nannofossil chalk bearing moderately to well preserved ,~pecies identified as Laeviheterohelix pulchra, Globigerinelloides asperus, Hedbergella planispira and H. delrioensis, Marginotruncana coronata and Globotruncana linneiana. Based on these identifications and study of the calcareous nannoplankton assemblages, this core was assigned a Santonian to lowermost Campanian age. However, reinspection of six samples from Sections 28-264-11-1 and -2 reveals that the assemblages are predominantly composed ofbiserial and planispiral taxa including Heterohelix globulosa, H. punctulata, H. planata and Globigerinelloides messinae, with moderately common occurrences of Archaeoglobigerina austral& Hedbergella sliteri and Globigerinelloides impensus. Rare occurrences of Hedbergella holmdelensis and G. linneiana were also noted. Based on the revised foraminiferal identifications and the absence of H. delrioen-

sis, M. coronata, Archaeoglobigerina cretacea and Laeviheterohelix glabrans, sediments from Core 28-264-11 are assigned to the middle of the late Campanian G. impensus Zone. This revised age determination has been corroborated by J. Pospichal (pers. commun., 1992) based on the identification of the nannofossils Reinhardtites aff. anthophorus (=R. levis of some authors), Biscutum coronum, B. dissi-

118

B.T. HUBER

milis and Eiffelithus eximius, but absence of Marthasterites furcatus in Sample 28-264-11-

LEG 21, SITE 208

1,101-103 cm.

PLANKTONIC FORAMINIFER DATUM INTERVALS o

Lord Howe Rise DSDP Site 208 The only hole in the South Pacific that has penetrated Upper Cretaceous pelagic carbonate sediments was drilled at DSDP Site 208 on the Lord Howe Rise in 1545 m water depth (Burns et al., 1973). Two cores containing a total of 10.5 m of nannofossil chalk were recovered at this site. Keating et al. ( 1975 ) analyzed samples from those cores to determine their magnetic polarity, but they did not account for the presence of a hiatus at the top of the Cretaceous sequence. As a result, the youngest Cretaceous reversed polarity interval was identified as Subchron C29R and the oldest normal interval was correlated with Subchron C30N. An alternative interpretation is shown in Fig. 5. The reversed polarity interval that includes the first appearance datum (FAD) of Abathomphalus mayaroensis (see Webb, 1973) is assigned to Subchron C31R based on correlation with Sites 689, 690 and 700. Below this datum are short intervals of normal then reversed polarity followed by a longer interval of normal polarity. These are correlated with Subchron C32N based on the presence ofR. circumnodifer, but absence of A. mayaroensis. Thus, the cores are now considered to range from upper lower Maastrichtian to lower upper Maastrichitan.

Biozonation

Of the thirteen Upper Cretaceous biozones that are currently used to subdivide deep-sea sequences in the Tethyan Realm (Fig. 5 ), only the .4. mayaroensis Zone can be identified at sites within the Austral Realm. Such is also the case for the middle latitude biozonation of Wonders (1992), who has recognized nine

~

m

sgo, ~ ~ii i l normal polarity ~nannofossil :::=::

chalk ~

chert

°e

W

~

~a ~

uncertain polarity

II i

I reversed polarity

recovered interval ~::~stratigraphic uncertainty C~] first app. interval

..... .

hiatus

Fig. 5. Planktic foraminiferal biostratigraphic zonal schemes for the Tethyan, Transitional, and Austral Biogeographic Realms. ~Caron, 1985; ~'Robaszynskiet al., 1979;~onders, 1992;~Huber, 1990;5thisstudy. planktic foraminiferal zones at Leg 122 sites in the Indian Ocean. Prior to the recent phase of high-latitude drilling, no zonal schemes had been developed for inter-oceanic correlation of Upper Cretaceous marine sequences from within the Austral Realm. Biozonations had been proposed for New Zealand (Webb, 1971 ), southern South America (Natland et al., 1974; Malumian and Masiuk, 1978), and the Antarctic Peninsula (Huber, 1988), but these were based on studies of nearshore terrigenous clastic sequences, and could only be applied locally. Upper Cretaceous biozones were not recognized or proposed for DSDP Sites 327 and 511 for reasons including the absence of zonal marker taxa, incomplete stratigraphic recovery, and uncertainty in correlation to the few other existing deep-sea sites in the southern high-latitudes. The three planktic foraminiferal zones defined at Maud Rise Sites 689 and 690 (Fig. 5) were subsequently identified at the Northeast Georgia Rise (Huber, 1991a ), and on the Kergeulen Plateau (Huber, 1991 b). Since a number of datum events have been found in the

UPPERCRETACEOUSPLANKTICFORAMINIFERALBIOZONATION

-~~ ZONE X <

SUBZONE

i~

119

~

~~ ~~

~ ~ ~

- -

_-- :: ~

P. elegans L Abathomphalus G. subcarinatus

mayaroensis

~ <

G. petaloidea A. intennedms E Globotr~ca~ella R. circumnodifer havanensis A. australis L

!iliiiiiiililill iiiiliiiiiiiiiiiiiiiiiiiiiiiiiiilililililililiiiiiiiiii ...............................

GlobigerineUoidesimpensus .................................

< r~

E

~ Z

L

Marginotruncana marginata

L E L

Whiteinella baMca

CON. • TUR.

Archaeoglobigerinacretacea

E L

CENO.-

....... ii::i- i iiili_. .................................

Praeoglobotruncanaspp.

E

Fig. 6. Ranges of nominate zonal taxa and some other biostratigraphic marker species relative to the Austral biozonation. Horizontonal lines on range bars denote datum levels used to define zonal boundaries, dashed lines denote interval where species is absent, and question mark indicates range uncertainty. TABLE 2 Location, sample interval, subbottom depth, and magnetochron of first and last appearance datums used to define the Austral zonal boundaries DATUM

SITE

CORE SAMPLE

SUBBOTrOM DEFFH (m)

SUBCHRON

FAD P. e / e g ~

69012

15X-5,76-78 ern

249.67

C29R"

FAD G. subcminmm

690C

18X-l, 119-123 ¢ ~

272.59

C31R a

FAD A. m a y m ~ n m

i 690C

18X,CC

278.30

C31R"

19X-l, 119-123 a n

2~..09

C31R'

290,80

C321~ C331~

FAD,4. ~

F~U~ ~ ~m,nnoa0~

¢O0C

19K CC

LAD O. W

fO0C

22X-3, 107-111 zm

314.50

F A D {7./m/mt~a

511

~ , 1312

219.00

LAD ~ ~ a

511

3@1, 24-2g era

299.74

FAD AL c r a m ~

511

45-1, 90-92 ,-m

385.90

C341~

511

48-I, 24-27 em

413.74

C34N ~

laD/~g,/~zot~

spl,.

? .9

same relative order within the upper Campanian-upper Maastrichtian throughout the Southern Ocean region (see above), refinement of Huber's (1990) b.~ostratigraphic scheme is warranted. Moreover, comparison of

well-preserved assemblages of Campanian and older planktic foraminifera from the Falkland Plateau, the Northeast Georgia Rise and the Naturaliste Plateau has revealed a similar sequence of correlatable bioevents. Compilation of this information forms the basis for proposal of the new zonal scheme for the Upper Cretaceous. The biostratigraphic ranges of marker species found in these zones are depicted in Fig. 6 and these taxa are illustrated in Plates I and II. The core sample, subbottom depth, and magnetic polarity of oiostratigraphic datum levels used to define the Austral biozones are summarized in Table 2.

Praeglobotruncana spp. Total Range Zone Definition: Interval comprising the total range of Praeglobotruncanaspp.

120

Author: This study. Associated species: Laeviheterohelix pulchra, $chackoina cenomana, Hedbergella amabilis,

n,T ~nER

H. crassa, Whiteinella bornholmensis and W. brittonensis. Age: Late Albian--early Turonian.

UPPER CRETACEOUSPLANKTICFORAMINIFERALBIOZONATION

Remarks: Praeglobotruncanids are uncommon at all of the studied sites. The oldest occurrence of Praeglobotruncana in the south polar region is marked by the FAD of P. delrioensis in the upper Albian at Site 258 (Herb, 1974) and the Falkland Plateau (Sliter, 1977). The LAD ofPraeglobotruncana stephani denotes the top of the Praeglobotruncana Zone (Fig. 6), occurring in lower Turonian sediments at Site 258 (Herb, 1974) and Site 511 (pers. observation; PI. II; Figs. 5 and 6). Dicarinella algeriana and D. hagni cooccur with P. stephani at Site 258, but dicarinellids have not been observed at Site 511. Assemblages from the Praeglobotruncana spp. Zone are characterized by low species diversity, dominance by small hedbergellids, presence of relatively few biserial and planispiral forms. Whiteinella baltica first occurs in the middle of this zone and becomes moderately abundant at higher levels. Archaeoglobigerina bosquensis first occurs in the upper part of the Praeglobotruncana spp. Zone in low abundance. 327A-15-1, 45-47 cm through 36-327A-14-6, 69-71 cm and DSDP Site 511 samples 71-51149-5, 44-46 cm through 71-511-48-1, 24-27 cm.

Whiteinella baltica Interval Zone Definition: Interval, with W. baltica, from the LAD of Praeglobotruncana spp. to the FAD of Archaeoglobigerina cretacea. Author: This study. Associated species: Laeviheterohelix pulchra,

12 |

Globigerinelloides alvarezi, Schackoina cenomana, Hedbergella flandrini, Whiteinella archaeocretacea, W. bornholmensis, Archaeoglobigerina bosquensis, Marginotruncana marginata, M. pseudolinneiana, Globotruncana bulloides and G. linneiana. Age: Late Turonian-early Santonian. Remarks: Whiteinella baltica is moderately common throughout the W. baltica Zone, as are L. pulchra and G. alvarezi. Rare specimens of Hedbergella amabilis and Whiteinella archaeocretacea occur in the lower part of this zone. Marginotruncanids and globotruncanids are also rare and no single keeled taxa have been identified. Archaeoglobigerina bosquensis is a rare but persistent element of samples from this zone, whereas S. cenomana is much more sporadic in its occurrence. Reference section: DSDP Site 511, Samples 71511-48-1, 24-27 cm through 71-511-45-1, 9092 cm.

Marginotruncana

marginata

Concurrent

Range Zone

Definition: Interval from the FAD of Archaeoglobigerina cretacea to the LAD of Marginotruncana marginata. Author: This study. Associated species: Laeviheterohelix pulchra, Heterohelix globulosa, 11. punctulata, Globigerinelloides alvarezi, Hedbergella atlantica, H. crassa, Archaeoglobigerina bosquensis and Globotruncana bulloides. Age: Santonian-early Campanian. Remarks: Archaeoglobigerina cretacea is rela-

PLATE I

1. Laevtheterohelix eiabrans (Cushman), 113-690C- 19X- I~ I i 9-123 cm. 2. Pseudotextularia elegans (Rzhehak), 113689B-25X-5, 105-107 cm. 3. Gublerina acuta de Klasz, 113-690C-18X-4, 95-99 cm. 4, 5. Globigerinelloides impensus Sliter, 113-690C-22X-4, 118-122.6. Globigerinelloides subcarinatus (BriSnnirnann), i i 3-690C- 17X-3, 119-123 cm. 7, 8. Hedbergella crassa (Bolli), 113-690C-18X-4, 95-99 cm. 9, 10. Hedbergella amabilis Loeblich and Tappan, 71-511-47-6. 38-40 cm. 11. Schackoina cenomana (Schacko), 71-711-49-5, 44-46 cm. 12, ! 3. Whiteinella bornhobnensis (Douglas and Rankin), 71-4205, 27-29 cm. 14, 15. Hedbergella atlantica Petters, 7 !-511-40-!, 38-40 cm. 16, 17. Archaeoglobigerina bosquensis Pessagno, 71-511-42-5, 27-29 cm. 18, 19. Whiteinella baltica Douglas and Rankin, 71-511-47-6, 38-40 cm. 20. Archaeoglobigerina australis Huber, 71-511-24-5, 69-71. Scale bars for all figures represent 50/~m.

122

a.T. HU~ER

truncanids occur sporadically in the lower through middle M. marginataZone, whereas they have a more consistent &stribution in the

tively uncommon in the lower part of this zone, but increases in abundance within the upper part. Marginotruncana marginata and globo~

~ii~,~

,i

~

~

, ~ .:;~::ii:,::

i~i ~ ~i,~z~ii~i~i~i~i~!~!~

~i!~ ~ i i ~

~::;;~:::i,:/i~:/,~i!~

i~i~!i~ii~

!i~,~

.....

~

i~'!/;~

~ :~:f;::i~:i~i

~ ;! ~

~ ~

~ ~!~ ~ ~

,

~/i!" ~:;:;:~ ' : ! : , ; : ~ ! i i i ~ '

,~ ~

~

~,~,

~;~

~

m.:;::

UPPERCRETACEOUSPLANKTICFORAMINIFERALBIOZONATION

upper levels. The most common taxa include hedbergellids, G. alvarezi and A. bosquensis. Biserial and planispiral taxa become increasingly abundant toward the top of the zone, while W. baltica diminishes in abundance. The LAD of the latter species occurs several cores below the LAD of M. marginata at Site 511. No single keeled taxa have been observed within this zone at any of the Southern Ocean sites. Reference section: DSDP Site 511, Sample 71511-45-1, 90-92 cm through 71-511-36-1, 2428 era.

Archaeoglobigerina cretacea Interval Zone Definition: Interval, with A. cretacea, from the LAD ofMarginotruncana marginata to the FAD of Globigerinelloides impensus. Author: This stu,ly. Associated species: Laeviheterohelix pulchra, Heterohelix globulosa, Globigerinelloides alvarezi, Hedbergella atlantica, H. crassa, Archaeoglobigerina australis, Globotruncana bulloides and G. linneiana. Age: Early Campanian-eady late Campanian. Remarks: The nominate taxon occurs persistently in moderate abundance in the lower 0art of this zone, but is rare to absent in the upper part. Although it has been reported to range into the lower Maastrichtian in the tropical belt (Robaszynski et al., 1984; Caron, 1985), A. cretacea has not been found above the lower Campanian in the southern high-latitudes. Laeviheterohelix pulchra, H. globulosa and

PLATE II

| 23

Hedbergella atlantica are common throughout most of the zone, while H. crassa, G. bulloides and G. linneiana are less abundant and more sporadic in their occurrence. Reference section: DSDP Site 511, Sample 71511-36-1, 24-28 em through 71-511:26-CC.

Globigerinelloides impensus Total Range Zone Definition: Interval comprising the total range of G. impensus. Author: Huber, 1990. Associated species: Heterohelix globulosa, Globigerinelloides alvarezi, G. messinae, Hedbergella holmdelensis, Archaeoglobigerina australis, Globotruncana linneiana in the lower part and Laeviheterohelix glabrans in the upper part. Age: Late early Campanian-latest Campanian. Remarks: Assemblages from this zone are dominated by heterohelicids, G. impensus, G. messinae and A. australis. The lower part of the G. impensus Zone is missing at all Southern Ocean sites because of a disconformity; the FAD of G. impensus has been truncated by this disconformity at all sites. The LAD of G. impensus falls within Subchron C33N and is estimated at about 75.1 Ma based on magnetobiostratigraphic correlation with the Kent and Gradstein (1985) time scale (Huber, 1991 ). Reference sections: DSDP Site 511, Sample 71511-26-CC through 71-511-24-1, 78-80 era; ODP Hole 690C, Sample 113-690C-22X-4, 118-122 cm through 113-690C-22X-3, 107I l l cm.

1. Archaeoglobigerina cretacea ( d'Orbigny ), 71-511-34-4, 1-3 cm. 2. Marginotruncana marginata (Reuss), 71-511-36-5, 33-35 cm. 3, 4. Praeglobotruncana delrioenszs (Plummer), 71-511-49-5, 44-46 cm. 5, 6. Praeglobotruncana stephani (Gandolfi), 71-511-48-1, 24-27 cm. 7. Rugotruncana circumnodifer (Finlay), 113-690C-18x-5, 46-49 cm. 8. Globotruncana arca (Cushman), 113-690C-18X-3, 98-102 cm. 9, 10. Globotruncana linneiana (d'Orbigny), 71-511-33-1, 20-24 cm. 11, 12. Globotruncana bulloides Vogler, 71-511-29-1, 10-13 cm. 13, 14. Globotruncanella havanensis (Voorwijk), 113-689B-25X-5, 105-107 cm. 15. Globotruncanella petaloidea (Gandolfi), 113-690C-18X-1, 119-123 cm. 16. Abathomphalus intermedius (Bolli), 113-690C- 18X-5, 46-49 cm. 17. Abathomphalus mayaroensis (Bolli), 113°690C- 17X3, 119-123 cm. Scale bars for all figures represent 50/tin.

124

Globotruncanella havanensis Partial Range Zone

Definition: Interval, with G. havanensis, from the last occurrence of Globigerinelloides impensus to the first appearance of Abathomphalus mayaroensis, including the partial range of Globotruncanella havanensiso Author: Huber, 1990. Associated species: Laeviheterohelix glabrans, Heterohelix planata, H. globulosa, Globigerinelloides messinae, G. rnultispina, Archaeoglo. bigerina australis and A. mateola. Age: Early Maastrichtian. Remarks: Although G. havanensis occurs sporadically in this zone, the upper and lower zonal boundaries are easily recognized. The most common species include A. australis, Globiger-

inelloides messinae, G. multispina, Heterohelix planata and H. globulosa. Douglas (1969) originally defined the lower boundary ofthe G. havanensis Zone by the LAD of Radotruncana calcarata and the top of this zone by the FAD of Giobotruncana aegyptiaca, but neither of these two species occur in the southern highlatitudes. This zone is approximately equivalent in extent to the combined G. havanensis and Globotruncana aegyptiaca Zones used in Caron's ( 1985 ) Tethyan zonal scheme. Reference section: ODP Hole 690C, Sample 113-690C-22X.3, 107-111 cm through 113690C- 18X-CC.

B.T.~ER

been recorded from Austral Realm samples from this subzone. The base of the A. australis Subzone occurs near the top of Subchron C33N at Sites 689, 690 and 700 (Huber, 1990). Reference section: ODP Hole 690C, Sample 113-690C-22X-3, 107-111 cm through 113690C- 19X-CC.

Rugotruncana circumnodifer Partial Range Subzone

Definition: Interval from the first appearance of R. circumnodifer to the first appearance ofAbathomphalus intermedius. Author: This study. Associated species: Heterohelix planata, H. globulosa, Glogigerinelloides messinae, G. multispina, Hedbergella sliteri, Archaeoglobigerina australis, A.mateola and G. havanensis. Age: Late early Maastrichtian. Remarks: The FAD of R. circumnodifer correlates with Subehron C32N at all high-latitude paleomagnetic reference sections (Fig. 2). Other keeled species first appearing within this subzone in the Southern Ocean region include Globotruncana subcircumnodifer and Globotruncana arca (=Globotruncana bulloides of Huber, ! 990, 1991 ). Both of the latter species are relatively rare and occur sporadically in the high-latitude sections. Reference section: ODP Site 690, Sample ! 13690C-19X-CC through 113-690C-19X-1, 119123 cm.

Archaeoglobigerina australis Interval Subzone Abathomphalus intermedius Partial Range Definition: Interval, with A. australis, from the last occurrence of Globigerinelloides impensus to the first appearance of Rugotruncana circumnodifer. Author: This study. Associated species: Laeviheterohelix glabrans, Heterohelix planata, H. globulosa, Globigerinelloides messinae, G. multispina, Hedbergella sliteri and Archaeoglobigerina mateola. Age: Early Maastrichtian. Remarks: No keeled planktic foraminifera have

Subzone

Definition: Interval from the first appearance of A. intermedius through the first appearance ofA. mayaroensis. Author: This study. Associated species: Heterohelix globulosa, H. planata, Globigerinelloides messinae, G. multispina, H. sliteri and Rugotruncana circumnodifer. Age: Late early Maastrichtian.

UPPER CRETACEOUS PLANKTIC FORAMINIFERALBIOZONATION

Remarks: This subzone comprises a very short interval within Subchron C31R, occurring within Holes 689B, 690C, 747A and 750B. The morphology of A. intermedius is transitional between G. havanensis and A. mayaroensis. It is distinguished from G. havanensis by the presence of tegilla and one well-developed peripheral keel and paralleled on the ventral side by a faint keel which may disappear on the final one or two chambers. Surface costellae on ,4. intermedius are often aligned perpendicular to the coiling axis in the ventral side and parallel to the direction of coiling on the spiral side. Early forms of A. mayaroensis may be difficult to distinguish from A. intermedius. This transition is characterized by a decreased convexity of the dorsal side, flattening of the dorsal and ventral chambers, and strengthening of the ventral keel. Reference section: ODP Hole 690C, Sample 113-690C-19X-1, 119-123 cm through 113690C- 18X-CC.

Abathomphalus mayaroensis Partial Range Zone

Definition: Interval from the first appearance of A. mayaroensis to the Cretaceous/Tertiary boundary. Author: Bolli, 1957; modified in this study.

Associated species: Laeviheterohelix glabrans, Heterohelix globulosa, H. planata, Gublerina acuta, Globigerinelloides subcarinatus, Hedbergella sliteri, Globotruncaella petaloidea, Rugotruncana circumnodifer and Abathomphalus intermedius. Age: Late Maastrichtian. Remarks: The FAD of A. mayaroensis correlates with the middle of Subchron C31R at all circum-Antarctic paleomagnetic reference sections (Figs. 3 and 4). This datum is slightly younger at Site 516 ( 35 °S paleolatitude), occurring just below the Subchron C3 IN/C31R boundary (Berggren et al., 1983). Magnetos-

125

tratigraphic correlation of this datum is Umited to two reports from the Umbfian Appenines in Italy, where the FAD ofA. mayaroensis was recorded in Subchron C30N (PremoliSilva, 1977; Monechi and Thierstein, 1985), indicating that this species underwent a timetransgressive migration from polar to tropical latitudes. Globotruncana arca and G. subcircumnodifer are rare and sporadic within their range up to the middle part of this zone, and A. australis and .4. mateola become increasingly rare and then absent in the upper part of the zone. Reference section: ODP Hole 690C, Sample I 13-690C- 18X-CC through 113-690C-15X-4, 84-86 cm.

Globotruncanella petaloidea Concurrent Range Subzone

Definition: Interval, with G. petaloidea, from the first appearance of A. mayaroensis to the first appearance of G. subcarinatus. Author: This study. Associated species: Heterohelix globulosa, H. planata, Gublerinea acuta, Globigerinelloides messinae, G. multispina, H. sliteri, R. circumnodifer and Abathomphalus mayaroensis. Age: Late Maastrichtian. Remarks: Although the FAD of G. petaloidea does not coincide with the FAD of A. mayaroensis at the southern South Atlantic magnetostratigraphic reference sections, both datums occur within Subchron C31R (Fig. 3). Globotruncanella petaloidea is distinguished from G. havanensis by having a more petaloid equatorial outline and no more than four chambers in the final whorl. The FAD of Gublerina acuta (=Gublerina robusta of Huber ( 1990, 1991 ) occurs in the lower part of this subzone. Reference section: ODP Hole 690C, Sample 113-690C-18X-CC through 113-690C-18X-l, 119-123 cm.

126

B.T. HUBER

Globigerinelloides subcarinatus Partial Range Subzone

Definition: Interval from the first appearance of G. subcarinatus to the first appearance of P. elegans. Author: This study. Associated species: Heterohelix globulosa, Gublerina acuta, Globigerinelloides messinae, G. multispina, H. sliteri, R. circumnodifer and Abathomphalus mayaroensis. Age: Late Maastrichtian. Remarks: The FAD of G. subcarinatus consistently occurs shortly above the FAD of A. mayaroensis at all circum-Antarctic sites, within the upper part Subchron C31R. This distinctive datum is much younger than in lower latitudes, where G. subcarinatus has been reported to range into the upper Campanian (Sliter, 1989) and lowermost Maastrichtian (Caron, 1985 ). Reference section: ODP Hole 690C, Sample 113-690C-18X-1, 119-123 cm trough 113690C-15X-5, 76-78 cm.

Pseudotextularia

elegans

Partial

Range

Subzone

Definition: Interval from the first appearance of P. elegans to the Cretaceous/Tertiary boundary. Author: This study. Associated species: Heterohelix globulosa, H. planata, Globigerinelloides multispina, G. subcarinatus, Globotruncanella havanensis and Abathomphalus mayaroensis. Age: Latest Maastrichtian. Remarks: This subzone comprises a very short interval just below the Cretaceous/Tertiary boundary. It has been recorded only in circumAntarctic sections with complete upper Maastrichtian recovery, occurring at Sites 689, 690, 738 and 750. The FAD of P. elegans has been correlated with upper Subchron C30N where paleomagnetic data are available (Huber, 1990, 1991b). The morphological concept of

Nederbragt ( 1991 ) is used for P. elegans at all Southern Ocean sites. Reference section: ODP Hole 690C, Sample 15X-5, 76-78 cm through 113-690C-15X-4, 84-86 cm.

Concluding remarks Past studies of Upper Cretaceous marine sequences in the southern high-latitudes were hampered by uncertainty in chronostratigraphic correlation and low biostratigraphic resolution. This situation has dramatically improved with completion of a series of ODP legs drilled in the South Atlantic and Indian Ocean sectors ofthe Southern Ocean. Maud Rise sites 689 and 690 have provided excellent reference sections spanning the uppermost Campanian through the Maastrichtian. Both sites yield well-preserved and abundant calcareous plankton and good magnetic polarity records, and thus have enabled an unprecedented accuracy in cross-latitude correlations. High quality magnetostratigraphic data were also obtained from Upper Cretaceous sediments at Site 700, although biostratigraphic resolution at this site diminishes in the early Maastrichtian and older sediments as a result of worsening microfossil preservation. Analysis of planktic foraminiferal assemblages from Site 208 on the Lord Howe Rise and sites 738, 747 and 750 on the Kerguelen Plateau provides the basis for recognition of six datum levels that are used to mark the boundaries of six planktic foraminiferal subzones proposed in this study. Restudy of the excellently preserved planktic foraminifera from site 327 and 511 on the Falkland Plateau, and their correlation with DSDP sites 258 and 264 on the Naturaliste Plateau reveals four additional datum levels that are proposed as zonal boundary markers for the Cenomanian-Campanian interval in the Austral Realm. Further biostratigraphic refinement is needed in the Cenomanian-Campanian interval. Major stratigraphic gaps still span most of

UPPER CRETACEOUS PLANKTIC FORAMINIFERAL BIOZONATION

the Cenomanian, parts of the Turonian, Coniacian, Santonian and the mid Campanian intervals. Poor microfossil preservation, hiatuses, and/or incomplete core recovery prevail at all of the sites in the south polar region that have been drilled to date. To add to cross-latitude correlation problems, a drilling gap remains that spans 38 °-50°S paleolatitude in all Southern Hemisphere oceans, and a magnetostratigraphic framework has not yet been established in pre-Maastrichtian sediments in the middle and high-latitudes. Future southern high-latitude drilling should target sites on the Agulhas and Crozet Plateaus to the south and southeast of Africa in an effort to link low- and high-latitude zonal schemes. These aseismic, intermediate depth plateaus were situated in the high middle latitudes during the Upper Cretaceous and are known to have a pelagic carbonate sedimentary record dating back to the Cenomanian (Saito et al., 1974). Drilling of Cretaceous sediments on the Agulhas and Crozet Plateaus would also provide unique insight on the history of gateway op~ning between the Indian and Atlantic oceans and development of intermediate and deep water masses between these two basins. Acknowledgeme~s Thanks are extended to Chris Hamilton for help with drafting the figures, the curatorial staff of the DSDP/ODP core repositories for making the core samples available, and an anonymous reviewer for the editorial comments. References Barker, P.F., Dalziel, I.W.D. et al., 1977. Init. Rep. DSDP, 36, 1079 pp. Barker, P.F., Kennett, J.P. et al., 1988. Proc. ODP, Initial Reports, 113, 785 pp. Barron, J.A., Larsen, B. et al., 1989. Proc. ODP, Init. Pep., 119, 942 pp. Basov, I.A. and Krasheninnikov, V.A., 1983. Benthic foraminifers in Mesozoic and Cenozoic sediments of the

| 27 southwestern Atlantic as an indicator ofpaleoenvironment, Deep Sea Drilling Project Leg 71. Init. Rep. DSDP, 71: 739-787. Berggren, W.A., Hamilton, N., Johnson, D;A., Pujol, C., Weiss, W., Cepek, P. and Gombos, A.M., Jr., 1983. Magnetobiostratigraphy of Deep Sea Drilling Project Leg 72, Sites 515-518, Rio Grande Rise (South Atlantic). Init. Rep. DSDP, 72: 939-947. BoUi, H.M., 1957. The genera Praeglobotruncana, Rotalipora, Globotruncana, and Abathomphalus in the Upper Cretaceous of Trinidad. (Studies in Foraminifera.) U.S. Nat. Mus. Bull., 215:61-82. Burns, R.E., Andrews, J.E. et al., 1973. Init. Rep. DSDP, 21,931 pp. Caron, M., 1985. Cretaceous planktonic foraminifera. In: H.M. Bolli, J.B. Saunders and IC Perch-Nielsen (Editors), Plankton Stratigraphy. Cambridge Univ. Press, pp. 17-86. Caron, M. and Homewood, P., 1983. Evolution of early planktic foraminifera. Mar. Micropaleontol., 7: 453462. Ciesielski, P.E, Kristoffersen, Y. et al., 1988. Proc. ODP, Init. Rep., 114, 815 pp. Crux, J.A., 1991. Calcareous nannofossils recovered by Leg 114 in the subantarctic South Atlantic Ocean. Proc. ODP, Sci. Results, 114: 155-177. Davies, T.A. and Luyendyk, B.P. et al., 1974. Init. Rep. DSDP, 26, 1129 pp. Douglas, R.G., 1969. Upper Cretaceous planktonic foraminifera in northern California. Micmpaleontology, 15(2): 151-209. Hailwood, E.A. and Clement, B.M., 1991. Magnetostratigraphy of Sites 699 and 700, East Georgia Basin. Proc. ODP, Sci. Results, 114: 337-353. Hamilton, N., 1990. Mesozoic magnetostratigraphy of Maud Rise, Antarctica. Proc. ODP, Sci. Results, 113: 255-260. Hayes, D.E., Frakes, L.A. et al., 1975. Init. Rep. DSDP, 28, 1017 pp. Herb, R., 1974. Cretaceous planktonic foraminifera from the eastern Indian Ocean. Init. Rep. DSDP, 26: 745769. Huber, B.T., 198~. Upper Campanian-Paleocene foraminifera from the James Ross Island region (Antarctic Peninsula). In: R.M. Feldmann and M.O. Woodburne (Editors), Geology and Paleontology of Seymor Island, Antarctica. Geol. SOc. Am. Mere., 169: 163251. Huber, B.T., 1990. Maestrichtian planktonic foraminifer biostratigraphy of the Maud Rise (WeddeH Sea, Antarctica): ODP Leg 113 Holes 689B and 690C. Proc. ODP, Sci. Results, 113:489-513. Huber, B.T., 1991a. Planktonic foraminifer biostratigraphy of Campanian-Maestrichtian sediments from ODP Leg 114, Sites 698 and 700, southern South Atlantic. Proc. ODP, Sci. Results, 114: 281-297.

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Huber, B.T., 199 lb. Maestrichtian planktonic foraminifer biostratigraphy and the Cretaceous/Tertiary boundary at ODP Hole 738C (Kerguelen Plateau, southern Indian Ocean). Proc. ODP, Sci. Results, 119: 451-465. Huber, B.T., 1992. Paleobiogeography of CampanianMaastrichtian foraminifers in the southern high latitudes. Palaeogeogr., Palaeoclimatol., Palaeoecol., 92: 325-360. Huber, B.T. and Watkins, D.K., in press. Biogeography of Campanian-Maastrichtian calcareous plankton in the region of the Southern Ocean: paleogeographic and paleoclimatic implications. In; J.P. Kennett (Editor), Paleoceanographic and Biotic Evolution of the Antarctic: A Global Change Perspective. (Antarctic Research Series.) Am. Geophys. Union,,, Washington, D.C. Keating, B., Helsley, C.E. and Pessagno, E.A., 1975. Late Cretaceous reversal sequence. Geology, 3: 73-76. Kent, D.V. and Gradstein, F.M., 1985. A Cretaceous and Jurassic geochronology. Geol. Soc. Am. Bull., 96:14 ! 91427. Krasheninnikov, V.A. and Basov, I.A., 1983. Stratigraphy of Cretaceous sediments of the Falkland Plateau based on planktonic foraminifers, Deep Sea Drilling Project, Leg 71. lnit. Rep. DSDP, 71: 789-820. Malumian, N. and Masiuk, V., 1978. Foraminiferos pianct6nicos dei Cretficico de Tierra dei Fuego. Asoc. Geol. Arg. Rev., 33( I ): 36-51. Monechi, S. and Thierstein, H.R., 1985. Late Cretaceous-Eocene nannofossil and magnetostratigraphic correlations near Gubbio, Italy. Mar. Micropaleontol., 9:4 ! 9-440. Natland, M.L., Gonzalez, P.E., Ca~6n, A. and Ernst, M., 1974. A system of stages for correlation of Magallanese Basin sediments. Geol. Soc. Am. Mem., 139: 1126. Nederbragt, A.J., 199 I. Late Cretaceous biostratigraphy and development of Heterohelicidae (planktic foraminifera). Micropaleontology, 37: 329-372. Pospichal, J.J. and Wise, S.W., 1990. Maestrichtian calcareous nannofossil biostratigraphy of Maud Rise ODP Leg 113 Sites 689 and 690, Weddell Sea. Proc. ODP, Sci. Results, 113: 465-487. Premoli Sil,'a I., 1977. Upper Cretaceous-Paleocene magnetic stratigraphy at Gubbio, Italy; II. Biostratigraphy. Geol. Soc. Am. Bull., 88:371-374. Premoli Silva, I., 1991. Oldest Cretaceous planktonic foraminifers from Hole 700B. Proc. ODP, Sci. Results, ! 14: 299-302. Quilty, P.G., 1992. Upper Cretaceous planktonic foraminifers and biostratigraphy, Leg 120, southern Kerguelen Plateau. Proc. ODP, Sci. Results, 120:371-392. Robaszynski, F., Caron, M. (Coordinators) and European Working Group on Planktonic Foraminifera. 1979. Atlas of Mid Cretaceous Planktonic Foramini-

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fera ( Boreal Sea and Tethys). Cah. Micropaleontol., 1 and 2, C.N.R.S., Paris, pp. 1-185 and 1-181. Robaszynski, F., Caron, M., Gonzales Donoso, J.M., Wonders, A.A.H. and the European Working Group on Planktonic Foraminifera, 1984. Atlas of Late Cretaceous Globotruncanids. Rev. Micropal~ontol., 26 (3/ 4): 145-305. Saito, T., Burckle, L.H. and Hays, J.D., 1974. Implications of some pre-Quaternary sediment cores and dredgings. In: W.W. Hay (Editor), Studies in Paleooceanography. SEPM Spec. Publ., 20: 6-36. Salloway, J.C., 1983. Paleomagnetism of sediments from Deep Sea Drilling Project Leg 71. Init. Rep. DSDP, 71: 1073-1091. Schlich, R.W., Wise, S.W., Jr. et al., 1989. Proc. ODP, Init. Rep., 120, 648 pp. Sliter, W.V., 1989. Biostratigraphic zonation for Cretaceous planktonic foraminifers examined in thin section. J. Foraminiferal Res., 19: 1-19. Scotese, C.R. and Denham, C.R., 1988. Terra Mobilis: plate tectonics for the Macintosh. Earth in Motion Technologies, Austin, TX. Sliter, W.V., 1977. Cretaceous foraminifers from the southwestern Atlantic Ocean, Leg 36, Deep Sea Drilling Project. Init. Rep. DSDP, 36: 519-573. Thierstein, H.R., Asaro, F., Ehrmann, W.U., Huber, B.T., Michel, H., Sakai, H. and Schmitz, B., 1991. The Cretaceous/Tertiary boundary at Site 738, southern Kerguelen Plateau. Proc. ODP, Sci. Results, 119: 849-867. Watkins, D.K., 1992. Upper Cretaceous nannofossils from Leg 120, Kerguelen Plateau, Southern Ocean. Proc. ODP, Sci. Results, 120: 343-370. Webb, P.N., 1971. New Zealand Late Cretaceous (Haumurian) foraminifera and stratigraphy: a summary. N.Z.J. Geol. Geophys., 14: 795-828. Webb, P.N., 1973. Upper Cretaceous-Paleocene foraminifera from Site 208 (Lord Howe Rise, Tasman Sea), DSDP, Leg 21. Init. Rep. DSDP, 21: 541-573. Wei, W. and Thierstein, H.R., 1991. Upper Cretaceous and Cenozoic calcareous nannofossiis of the Kerguelen Plateau (Southern Indian Ocean) and Prydz Bay (East Antarctica). Proc. ODP, Sci. Results, 119: 467493. Wind, F.H. and Wise, S.W., Jr., 1983. Correlation of upper Campanian-lower Maestrichtian calcareous nannofossil assemblages in drill and lower piston cores from the Falkland Plateau, Southwest Atlantic Ocean. Init. Rep. DSDP, 71:551-563. Wise, S.W., Jr., 1983. Mesozoic and Cenozoic nannofossils recovered by Deep Sea Drilling Project Leg 71 in the Falkland Plateau region, Southwest Atlantic Ocean. Init. Rep. DSDP, 71: 481-550. Wonders, A.A.H., 1992. Cretaceous planktonic foraminiferal biostratigraphy, Leg 122, Exmouth Plateau, Australia. Proc. ODP, Sci. Results, 122: 587-599.