Mesozoic-cenozoic history of calcareous nannofossils in the region of the southern ocean

Palaeogeography, Palaeoclimatology, Palaeoecology, 67 (1988): 157 179

157

Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

MESOZOIC-CENOZOIC HISTORY OF CALCAREOUS NANNOFOSSILS IN THE REGION OF THE SOUTHERN OCEAN SHERWOOD W. WISE, JR. Florida State University, Tallahassee, FL 32312 (U.S.A.) (Accepted for publication November 3, 1987)

Abstract Wise, Jr., S. W., 1988. Mesozoic-Cenozoic history of calcareous nannofossils in the region of the Southern Ocean. Palaeogeogr., Palaeoclimatol., Palaeoecol., 67:157 179. The Mesozoic Cenozoic evolution of high southern latitude calcareous nannofossil assemblages developed in parallel with that of the Southern Hemisphere ocean basins and the attendant progressive changes in global climate. The equitable Middle to Late Jurassic climates are reflected in a cosmopolitan zonation although distinctive high latitude taxa developed in both polar regions. Monospecific or low diversity provincial assemblages characterized the incipient Early Cretaceous South Atlantic Basins until the introduction of Tethyan elements during the Aptian. Bipolar or austral provincial taxa are useful in erecting a biostratigraphic subdivision for the remainder of the Cretaceous sequence on the Falkland Plateau. In contrast to the middle Cretaceous, the global sample coverage of DSDP holes for the Campanian-Maestrichtian is sufficiently broad to demonstrate a distinct latitudinal distribution of species and assemblages. Provincial austral or bipolar taxa are relatively minor components of the Paleocene Eocene assemblages, but quantitative methods document the existence of definable high latitude assemblages which shifted latitudinally in response to climatic changes. Indirect evidence suggests that calcareous nannofossils were deposited in the interior basins of Antarctica during this interval. Species diversities declined progressively through the Oligocene Miocene epochs in response to the deterioration of Neogene climates and glacial episodes on the Antarctic continent, finally resulting in low diversity assemblages generally dominated by high latitude taxa. Sharp migrations of these assemblages occurred in response to glacialclimatic events. Plio/Pleistocene sediments deposited beneath the expanding Antarctic water mass are essentially barren of calcareous nannofossils, but coccoliths are widely distributed in the Subantarctic region as a result of the amelioration of Holocene climate and the Quaternary descent of the carbonate compensation depth. Two new taxa are described: Stephanolithion bigotii brevispinus n. ssp. from the Upper Jurassic and Gephyrobiscutum diabolum n.g., n. sp. from the lower Campanian.

Introduction

al., 1977; L u d w i g , K r a s h e n i n n i k o v e t al., 1980; s e e s u m m a r i e s b y W i s e e t al., 1980, 1985). T h e s e

Until this past year, exploration by deep sea drilling of pre-Neogene calcareous sequences in the Southern Ocean has been quite limited, therefore much of ..the information on the

d r i l l h o l e s ( Fi g s.1 a n d 2) p e n e t r a t e d d o w n t o middle Jurassic strata, thereby providing a record which predates in part the breakup of

Mesozoic-Cenozoic history nofossils from this region primarily from a series of near the Falkland Plateau 0031-0182/88/$03.50

of calcareous nanhas been derived holes drilled on or (Barker, Dalziel et

G o n d w a n a l a n d . T h e r e a f t e r , t h e p l a t e a u subsided to its p r e s e n t i n t e r m e d i a t e w a t e r depth, w h e r e it was ideally s i t u a t e d to r e c e i v e calcare o u s - r i c h s e d i m e n t s t h r o u g h o u t m o s t of its history from Albian times (middle Cretaceous)

© 1988 Elsevier Science Publishers B.V.

158 :..-

0

• • ".''.:"

~. 4.0 o

l li '~."T •. " ~ - . , , " " " ~ ' " "': ~

{_# ~ '~

ArLANrm ~

5 - 29

\-a

OCEAN ' 512 d

~.

t.

• '

•

-

~

: 50 °

c_ °

t

60 °

/ Z / /} ~,

WEODELL

t:.:.~/

, 70 °

%

60 °

II

SEA

3, 50 °

~E'~.3._.

, 40 °

,

,

30 °

20 °

70 °

I0 °

0°

I0 o

Fig.1. Locations of drill sites and sample localities. onwards. This summary of the Mesozoic-Cenozoic development of Southern Ocean calcareous nannofloras, therefore, is based primarily on the drill sequences from the Falkland Plateau and its environs. Even this record, which spans some 150 million years, is far from complete as will be pointed out during this narrative, therefore it is hoped t h a t significant gaps will be filled as the results of the more recent drilling in Antarctic waters become availabe (Leg 113 Scientific Party, 1987; Barker, et al., this issue; Leg 114 Scientific Party, 1987; plus the upcoming Ocean Drilling Program Legs 119 and 120 to the Kerguelen Plateau planned for the austral summer of 1988). Calcareous nannofossils (from the Greek, meaning "dwarf fossils") are the most common primary constituents of deep sea calcareous oozes, and represent for the most part the calcitic skeletal remains of golden-brown unicellular algae that have inhabited the photic zones of the oceans since Late Triassic times (see summaries by Wise, 1982; Perch-Nielsen,

1985a, b). Their preferred habitat has been in the warmer waters of the low to mid latitudes where they attain their greatest diversity, although some species became adapted exclusively to the mid or high latitudes. As will be noted during the ensuing discussion, provincialism is not uncommon among the high latitude assemblages, particularly in the region of the present day Southern Ocean, and these taxa constitute some of the better regional stratigraphic markers. Initial studies of Southern Ocean land and drill sequences in both the Atlantic and Pacific sectors concentrated on establishing a nannofossil biostratigraphic and taxonomic framework (Edwards, 1971, 1973; Edwards and PerchNielsen, 1975; Burns, 1975; Haq, 1976; Wise and Wind, 1977; Wise, 1983), but these efforts were also accompanied or soon followed by quantitative biogeographic studies aimed at elucidating paleoclimates and paleo-oceanographic history where data permitted (examples, Haq et al., 1977a, b; Haq and Lohmann, 1977; Haq, 1980; Wind, 1979a, b; Roth and Bowdler, 1981;

159

--

_

>-

w

co

Go

--

oJ

L0 6'3 F--

03 t0

03 LO

o~ a0

O O

o

0'~"

o 0

y

z _~_

m~.~ I

o

(2D Z

-~

W

~

o

o

o

o

I.-

©

OOo Y o

-~

I.-

t~

60

~_

J

o

O

o

½

o

~

z

~ 0 b_

z '~ Z

w

F_

N

13-

Z

| W

n~

o

0 ~ -0~ ~t

-8 8

•.,..°. •

W

m~

121 if-

he" 113

m~

o~ Z

m

S

C3 Z <[ d X: __J

C

8 ~ ¢-

m~

0

" C3

i

w z

~v ow

13_ Ww o~ JD o

It_

c~ o o

W (¢')

160

species. Stephanolithion b. brevispinus is essentially a provincial, high latitude form which may have a counterpart in the Volgian stage of Russia (Medd, pers. comm., 1981; K. Cooper, pers. comm., 1987), but is yet unknown in England. The application of an otherwise cosmopolitan zonation to the Falkland assemblages is attributed to a generally equatable world climate relative to today. Nevertheless, a clear contrast between Tethyan and Boreal/ Austral assemblages had been established by the Late Jurassic. A true quantitative global comparison of the compositions and diversities of the Upper Jurassic nannofossil assemblages would better distinguish the high latitude assemblages, but this must await published descriptions of the higher latitude boreal assemblages of the Northern hemisphere.

Thierstein, 1981; Roth and Krumbach, 1986). For the South Atlantic sector, we will discuss these various studies by time period. Jurassic

Biostratigraphy The Upper Jurassic nannofossil assemblages of Falkland Plateau were deposited in shallow interior seas of southwestern Gondwanaland and consist of about 30 species, a diversity which compares favorably with that of the relatively shallow water, boreal localities of England (Wise and Wind, 1977). Wise (1983) was able to zone the Colovian?/Oxfordian to lower Tithonian sequence (Fig.3) using the cosmopolitan open marine zonation of Roth et al. (1983), which had been developed for the low latitude Blake Bahama Basin. In addition, Wise (1977) added as an alternate zonal marker a short-spined stephanolithid (named herein Stephanolithion bigotii brevispinus; see Appendix A), which first appears well above the first appearance datum (FAD) of S. bigotii bigotii and ranges higher in the section than the latter

Biogeography Not well understood are the marine connections into the shallow interior Jurassic seaway of southwestern Gondwanaland which supported the somewhat provincial Late Jurassic nannoflora. Mutterlose (1987) assembled beDATUM LEVEL Cretoceous toxo LAD B/scutum moqnum LAD Biscutum coronum

MIDOLE-EARLYM/~ES]RIO-I[.JBiscutum moqnum EARLY MAESTRICHTIANI Biscutum coronum -EARLY CAMPANIAN

1

EARLY CAMPANIAN SANTON[AN

Morthosferites furcofus

Gartnerago costatum

L ithostrinus f~orolis SANTONIAN-CONIACIAN Ti~'erste~io ecclesk~h'ca

LATE TURONIAN ~ n i f / c u s TURONIAN-LATEALBIAN Eiffellithus turriseiffeli Tronolifhus orionotus

EARLY-MIDDLEALBIAN

EARLYAPTI,tu'~IBARREMIAN

F_ARLYTITHONIAN-

Prediscosphoero columnuto Chiostozygus litterarius/ Micrantho//thus hoschulzii

Vekshinello strodneri Stephanolithion bigoh7 brew'spinus

OXFORDIAN,CALLOVINq? Stephono/ith/on t~'goh'i

~

B/scutum coronum o r LAD Morthosterites furcotus FAD Geph robiscutum diobolum LAD L/thostrinus florolis LAD Thiersteimo ecc/esiostico Marthosten?es furcatus FAD Kom tnerius me nificus FAD Eiffe//ifhus turnseiffe/ii So//as/tes folk/ondensls " ~ Tronol/Thusononotus FAD So//osites fo/k/ondensis FAD Prediscos~ohoero columnuto Lithostrinus f/orolls LAD Cruc/b/scutum so/ebrosum

~Zeu

r

bdotus ember or~

I~AD Veksh/he//o strodnen or PAD SteDhonoh?hlbnb.brevlsDihu~

Fig.3. Mesozoic calcareous nannofossil zones recognized in the region of the Falkland Plateau.

161 :: "::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ..~:~:~:~:!:~:~:~::~:

30 °

".::..

"::"':"

:>Kimmeridgian, Lower Tithonian

[:>UpperTithonian

Fig.4. Presumedbelemnitemigrationroutes fromTethys to the Falkland Plateau region during the Late Jurassic (after Mutterlose, 1986, fig. 8).

lemnite data, which are far more plentiful t h a n those for nannofossils, to reconstruct possible migration routes into the Southwest Gondwana Sea. These routes may in turn indicate the development of major seaway connections. According to his data (Fig.4), a circum-Gondwana route was followed from the Tethys through the Indo-Pacific during the Kimmeridgian/early Tithonian, after which a northern route opened across Ethiopia/Madagascar during the late Tithonian. Nannofossil data are still too sparse to confirm this model, but one would expect to find nannofossil evidence of these connections along the ancient Madagascar Seaway.

Jurassic~Cretaceous boundary Although coring was continuous across the Jurassic/Cretaceous boundary at Site 511 on the Falkland Plateau, no distinct contact was observed as sediments on either side of this juncture consist of organic-rich black claystones deposited in restricted environments (Fig.2). The sparse nannofossil assemblages are often characterized by the strong dominance of

a few taxa which bloomed in these peculiar environments. There was little bioturbation of the bottom sediments, and clusters representing the original coccospheres (sensu Covington, 1985) are common (examples, Wise, 1983, pl. 30, fig.l; pl. 33, figs. 3, 4). Because of the lack of a distinctive Jurassic/ Cretaceous contact in Hole 511, some question has remained as to the assignment of the interval from 534 to 554m. The section was dated as Cretaceous by palynomorphs and foraminifera (Kotova, 1983; Krasheninnikov and Basov, 1983), but Wise (1983) noted small numbers of Jurassic nannofossil which may or may not have been reworked. Regardless of where the Jurassic/Cretaceous boundary is placed, the lowermost Cretaceous is missing at Site 511. According to foraminiferal evidence (Krasheninnikov and Basov, 1983), no Berriasian through Hauterivian sediments are present. The hiatus resulted from tectonic events associated with the opening of the South Atlantic Basin (beginning about 127 Ma; Larson and Ladd, 1974). No equivalent nannofossiliferous strata have been documented from the region of the Southern Ocean, and even a purported Valanginian-Hauterivian nannofossil assemblage for the Brenton Beds of South Africa (Stapleton et al., 1977) is now thought to be Jurassic in age (Dingle et al., 1983).

Lower Cretaceous

Biostratigraphy The first dateable Cretaceous sediments at Site 511 are considered Barremian to early Aptian in age (Fig.3) based on the foraminiferal evidence and the absence of the nannofossil Cruciellipsis cuvillieri, which should have been present in Hauterivian sediments at these latitudes considering its distribution in the Northern Hemisphere. The last appearance datum of Crucibiscutum salebrosum appears to be a useful stratigraphic event in the high latitudes. In northern Europe it was originally placed in the Hauterivian by Sissingh (1977),

162

but both Taylor (1982) and Jakubowski (1987) found that it ranges into the lower Barremian in England and the North Sea region. It's abundance peak there, however, is in the Valanginian to lower Hauterivian (Jakubowski, 1987). Since this high latitude form is also abundant at Site 511 along with another bipolar species, Corollithion silvaradion, the biogeographic distribution and stratigraphic range Crucibiscutum salebrosum needs further evaluation. The first appearance datums (FAD's) for Lithastrinus floralis and Prediscosphaera columnuta (= P. cretacea) are well established cosmopolitan events in the middle Aptian and lower Albian respectively (Fig.3). At Site 511, the P. cretacea Zone as delineated by Wise (1983, table 1C) is quite long, some 57 m. It is here subdivided into two zones based on Wise's former subzonal marker, the FAD of Tranolithus orionatus (= T. phacelosus of some authors). Such a subdivision has proven useful at the subzonal level for drill sequences off Portugal (Applegate and Bergen, in press), which further demonstrates that the datum can be widely recognized. The zonation in Fig.3, therefore, is modified accordingly based on the section at Site 511 (see Appendix B). The resulting P. columnuta and T. orionatus Zones are further subdivided by the first and last occurrences of Sollasites falklandensis, a provincial species known only from the Falkland Plateau. The upper Albian is delimited by the FAD of the cosmopolitan Eiffellithus turriseiffelii, which is accompanied by the first specimens of Gartnerego found in the section (Wise, 1983, table 1C).

Paleoenvironment Like the Jurassic, the Barremian to Aptian section on the Falkland Plateau consists of organic-rich, black claystones which give way to increasingly thick chalk beds towards the close of the Aptian (see frontispiece, Ludwig, Krasheninnikov et al., 1983). The onset of carbonate deposition represents increased nannoplankton productivity in the overlying sur-

face waters (Parker et al., 1983), which has been attributed ultimately to the deep water ventilation of the South Atlantic as the Falkland Plateau moved past the tip of South Africa via sea floor spreading (Barker et al., 1977). Prior to this event, the South Atlantic basins were small and rather isolated, thereby fostering the development of high latitude, endemic assemblages. The waters may also have been strongly stratified due to the overflow of saline waters from basins north of the Rio Grande Rise-Walrus Ridge sill where halite deposits were accumulating (McCoy and Zimmerman, 1977). The black shales of the Falkland Plateau may owe their origin at least in part to such a stratification and the overflow of more saline waters from the north. In addition, the presence of numerous micrantholith fragments in the Rhagodiscus angustus Zone (Wise, 1983, table 1C) could reflect fluctuating salinity conditions (Wise and Wind, 1977) at the surface. It is most interesting that black shale deposition ended near the close of the Aptian, which is the time halite deposition ceased north of the Rio Grande-Walvis Ridge (J. Favera, pers. comm., 1987). In detail, chalk deposition on the Falkland Plateau began in a series of pulses, each represented by a laminae several centimeters thick (see Ludwig, Krasheninnikov et al., 1983, frontispiece). These may well represent modulations of the larger depositional regime by the effects of sea level fluctuations or, as suggested by Mutterlose (1987), the influx of warmer surface waters. According to Vail et al. (1977) and Haq et al. (1987), sea levels began to rise appreciably during the mid to late Aptian, thus deepening the water over the Plateau and promoting interchange of open marine surface waters throughout t h e restricted basins to the north. Mutterlose (1987) compared Falkland Plateau nannofossil assemblages and lithologies with similar sequences in Northern Europe, and postulated that both were effected synchronously by a climatic warming event, as indicated by the associated micro- and macrofauna. This apparently coincided with the influx of Tethyan-derived nan-

163

noconids (large calcareous nannofossils) into both regions. 3

Biogeography Middle Cretaceous nannofossil assemblages are sufficiently numerous and well known globally to allow quantitative biogeographic study, and the sections from the Falkland Plateau have served as the southern anchor of such investigations since they were first compared in a nonquantitative way by Wise and Wind (1977, Table 7) with other Southern and Northern hemisphere sections. Among the high latitude provincial forms highlighted by Wind and Wise (1977) was Seribiscutum primitivum, which Thierstein (1974, 1976) reported from the boreal and austral realms of Great Britain, the Crimea, and DSDP Sites 256, 257 and 258 west of Australia. It is common to abundant in the North Sea where it is used as a zonal marker variously by Jakubowski (1987) and Mortimer (1987). Shafik (1985) reports it from northern Australia in association with large numbers of T. orionatus, which together suggest a high paleolatitude and/or nearsurface cool-water regime in the isolated Eromanga Basin. Roth and his colleagues (1981, 1986) mention other occurrences, the bipolar distribution of which are indicated in Fig.5, along with the percent abundance for some upper Albian Cenomanian localities (Roth, 1981). The disparity between northern and southern hemisphere abundances of S. primitivum would not be so great as indicated in Fig.5 if the new Albian data from the North Sea were included where both Jakubowski (1987) and Mortimer (1987) find it abundant. On the Falkland Plateau, however, this taxon remains abundant in selected samples well into the Campanian (Wise, 1983, table 1B). With the exception of Seribiscutum primitirum and Lithastrinus floralis, most of the other middle Cretaceous taxa and assemblages analyzed by Roth and his colleagues do not show the expected latitudinal distribution pattern which characterizes modern open ocean calcareous n a n n o p l a n k t o n (MacIntyre and B~,

0°

Fig.5. Bipolar distribution of S e r i b i s c u t u m p r i m i t i v u m during the middle Cretaceous [updated from Roth and Krumbach (1986, fig. 13) whose percent abundance data are shown for southern England, the Falkland Plateau (DSDP Sites 327 and 330) and the Naturliste Plateau (DSDP Site 258)]. M F = Moray F i r t h [A = a b u n d a n t (Jakubowski, 1987)]; K = Kerguelen Plateau (Thierstein, 1977); Q L = Queensland, Australia (Shafik, 1985).

1967). This is probably due to the limited number of middle Cretaceous drill sequences, most of which represent the still narrow, confined Atlantic Ocean. There is little comparable information from the Pacific, and those sections were obtained and studied during the early phases of the Deep Sea Drilling Project before Cretaceous nannofossil zonations were well established. Roth and Krumbach (1986), therefore, interpret most of their quantitative data in terms of paleoproductivity and the distribution of upwelling regimes as summarized in Fig.6. By their analysis, neritic oceanic gradients appear to overshadow latitudinal ones. Roth and Bowdler (1981) and Roth and Krumbach (1986) identify the Falkland Plateau as a zone of documented upwelling and high fertility based on high percentages of Zygodiscus erectus and Biscutum constans. To re-emphasize, however, another characteristic of the mid to high latitudes are restricted basins and blooms of particular, often provincial taxa (Wise, 1983, pl. 30, fig. 1; pl. 33, fig. 4).

164 ,oo-.v..~v

",~/~L~,~

-~- ~

k..I:~:-~3X ~X~,V/

Fig.6. Surface water circulation, upwelling areas, and high southern latitude nannofossil assemblages for the midCretaceous (after Roth and Krumbaeh 1986, figs. 13 and 14). Cross-hatched: assemblage with Seribiseutumprimitivum and abundant Lithastrinus floralis. Solid pattern: high fertility assemblages contain common Zygodiscus ereetus and Biscutum constans. N o t c o u n t e d s e p a r a t e l y by R o t h and Krumb a c h (1986) was Repagulum parvidentatum, w h i c h is c o m m o n to a b u n d a n t in most n a n n o fossiliferous samples at Site 511 b e g i n n i n g with the Rhagodiscus angustus Zone (Wise, 1983, table 1C). It is figured in the light m i c r o s c o p e by J a k u b o w s k i (1987, pl. 1, figs. 4-5), who uses its a b u n d a n c e p e a k in the l o w e r to middle A l b i a n to define a local zone in t h e N o r t h Sea. B e c a u s e the r e l a t i v e d i s t r i b u t i o n of this t a x o n is not k n o w n on a global scale, its paleoenvir o n m e n t a l significance is n o t yet clear. H i g h a b u n d a n c e s , h o w e v e r , m a y well d e n o t e h i g h l a t i t u d e e n v i r o n m e n t s . It d i s a p p e a r s t e m p o r a r ily from the section in the Biscutum constans Subzone w h e r e it is soon r e p l a c e d by Biscutum dissimilis, a n o t h e r high l a t i t u d e species k n o w n o n l y from the S o u t h e r n Ocean.

and a rising c a r b o n a t e c o m p e n s a t i o n depth. This interval, w h i c h c a n n o t be f u r t h e r subdivided, c u l m i n a t e s with a b a r r e n 11 m pelagic clay s e c t i o n before m o d e r a t e l y preserved, upper T u r o n i a n assemblages are e n c o u n t e r e d ; these l a t t e r can be r e f e r r e d to the Kamptnerius magnificus Zone of R o t h (1978). On the F a l k l a n d P l a t e a u , this zonal i n t e r v a l is chara c t e r i z e d b y Thiersteinia ecclesiastica, a dist i n c t i v e h i g h l a t i t u d e form k n o w n o n l y from the S o u t h e r n O c e a n r e g i o n (Fig.7). Once a g a i n seen t o g e t h e r in this p a r t of the section are

Turonian-lower Campanian Biostratigraphy N a n n o f o s s i l assemblages of the u p p e r A1b i a n - C e n o m a n i a n are poorly, p r e s e r v e d at Site 511 due to t h e c o m b i n a t i o n of downflank subsidence of the F a l k l a n d P l a t e a u

Fig.7. Biogeographic distribution of the high latitude coccolith,Thiersteinia ecclesiastica based on its occurrences at DSDP Sites 511 and 258.

165

Repagulum parvidentatum and Seribiscutum primitivum. The top of the Kamptnerius magnificus Zone is marked by the FAD of Marthasterites furcatus, which at Site 511 coincides with the first Micula decussata decussata. This may indicate a slight hiatus or core loss since the latter should appear slightly higher in the section in relation to M. furcatus (Sissingh, 1977). The FAD of Marthasterites furcatus is a cosmopolitan datum used here, as in most regions, to approximate the T u r o n i a n / C o n i a c i a n boundary. Mortimer (1987) presents an extended discussion of the global correlation of this datum and agrees with Crux (1982) t hat it should be placed within the upper Turonian. At Site 511, the LAD of Thiersteinia ecclesiastica is used to delineate a local zone of t hat name, above which this spinose taxon is replaced by the non-spined Broinsonia parca lineage (Wise, 1983, fig. 5). The LAD of Lithastrinus floralis is a cosmopolitan datum used to delineate the subjacent zone of the same name. Within this interval Repagulum parvidentatum attains its greatest abundance, often outnumbering the generally dominant Watznaueria barnesae by an order of magnitude (Wise, 1983, table 1B). The upper S a n t o n i a n lower Campanian Marthasterites furcatus Zone at Site 511 is an e x t r ao r d in ar ily long (140 m) interval, which is here subdivided into two local subzones based on the o ccu r r en ce of Gephyrobiscutum diabolum n. sp. (see Appendices A and B). This minute (3 4~m long) lower Campanian t a xon was previously listed in the Site 511 range chart as "Amphizygus? sp." (Wise, 1983, table 1B). It is "highly a b u n d a n t " at its first appearance datum, which is an order of magnitude higher th an any other Mesozoic nannofossil known from the Falkland P l a t e a u (over 100 specimens per field of view of the microscope at 1000 x and up to 90% of the assemblage). It maintains this high abundance t hr ough several samples until 338m (Sample 511-39-4). 35 cm), where it is absent in displaced material within a disturbed portion of the section (see core photograph, Ludwig et al., p. 94).

Biogeography Gephyrobiscutum diabolum n. sp. has not been recorded elsewhere in the world, therefore its paleoenvironmental significance is not known ot her t han the fact t hat it is clearly a high latitude form. Because of a high global CCD (Thierstein, 1979), there are no other calcareous upper T u r o n i a n to lower Campanian drill sections in the Sout hern Ocean comparable to Site 511. A similar situation existed in the other world oceans because the Late Cretaceous high stand of sea levels shifted the locus of carbonate deposition from the deep sea to the flooded continental shelves and interior seaways (Hay, 1981). For this reason, insufficient oceanic sections exist for a global quantitative analysis of calcareous nannofossil assemblages for the T u r o n i a n to lower Campanian interval. Instead, such studies have been confined to local interior seaways (example, Watkins, 1987).

Campanian-Maestrichtian Biostratigraphy In cont rast to the above, the CCD descended rapidly in the ocean basins during the Campanian (Thierstein, 1979), thereby providing ample high as well as low latitude sections for biostratigraphic and quant i t at i ve biogeographic study. At Site 327 on the Falkland Plateau, the upper C a m p a n i a n - l o w e r Maestrichtian section measured 50 m thick, and contained a plethora of new high latitude taxa, which are described by Wise and Wind (1977). Among these were several t hat are potentially useful as local zonal markers; these are indicated in Fig.8 and furt her illustrated in the light microscope by Wind (1979, pl. 1). Unfortunately, the carbonate section at Site 327 was discontinuously cored t hrough the critical transition across the Campanian/Maestrichtian boundary, therefore a composite section had to be reconst ruct ed from drill and piston cores from three localities on the P l a t e a u (Fig.2). This transition, marked by the extinc-

166

Fig.8. Ranges of key provincial (austral) and cosmopolitan coccolith species across the Campanian]Maestrichtian boundary at DSDP Sites 327 and 511 on the Falkland Plateau (after Wind and Wise, 1983, fig. 2).

tions of th r ee provincial t axa (Fig.8), could be calibrated with the low latitude zonation t h r o u g h the presence of species of Tranolithus and Reinhardtites, which were utilized in the lower latitude zonation of Sissingh (1977). In addition, Wind (1979a, b) was able to trace the overlap of high and low latitude species at DSDP sites in the Indian Ocean. Based largely

on his work, the C a m p a n i a n - M a e s t r i c h t i a n zonation in Fig.3 was derived. The C a m p a n i a n - M a e s t r i c h t i a n zonation in Fig.3 is based on datums provided by distinctive high latitude species of the genus Biscuturn. These are generally more abundant and therefore more readily distinguished t han the more cosmopolitan zonal markers t hat may accompany them. One of these, B. magnum, has been found in England (Crux, 1982), and is therefore bipolar. The zonation in Fig.3, however, is incomplete in t h a t the middle Campanian was not present in the sections studied, therefore the many nannofossil FAD's and LAD's which occur in this interval have not yet been documented at these latitudes. The second weakness is the corresponding lack of an upper Maest ri cht i an section on the Falkland Plateau, where a prominent erosional disconformity separates lower Maest ri cht i an from upper Paleocene strata. Thus the upper Maest ri cht i an can only be inferred by extrapolation of the work in the southwest Indian Ocean by Wind (1979) and a more recent study to the south by Harwood (in Huber et al., 1984) of a Cretaceous/Tertiary boundary sequence on Seymour Island near the tip of the Antarctic Peninsula (Fig.l; see following discussion below). An important lineage t h r o u g h this section is represented by the kidney-shaped genus, Nephrolithus. Wise and Wind (1977) originally assigned all specimens to N. frequens, then the only known species and one which was confined to the upper Maest ri cht i an in other parts of the world. Wise and Wind noted, however, t h a t the specimens ranged deeper in the section at Site 327, perhaps into the Campanian. This enigma was resolved by Wind (1983), who determined t h a t the Falkland specimens represented a new S o u t h e r n Ocean species, N. corystus, which ranged from the upper Campanian t hrough the middle Maestrichtian in his Indian Ocean cores, but did not reach the mid or low latitudes as was the case with N. frequens. Due to the incomplete section on the Falkland Plateau, however, the m a n n e r in which N. corystus gave rise to N. frequens

167 could not be observed directly. Wind (1979a), therefore, suggested three hypotheses illustrated in Fig.9, to which a fourth has been added: (A) N. corystus either evolved in the high latitudes directly into N. frequens and the latter then migrated toward the tropics as global climates cooled; (B) N. corystus occupied the high latitude niche throughout the Maestrichtian while N. frequens migrated north; (C) the two taxa co-existed in the high southern latitudes until the end of the Maestrichtian; (D) the two taxa co-existed for a short time prior to the extinction of N. corystus, after which N. frequens migrated north. The last hypothesis is supported by Wind's observation (Wind, 1979a, fig. 2) that N. corystus and N. frequens co-existed at DSDP Site 249 off South Africa for a short interval during the late middle Maestrichtian. In addition, Harwood (in Huber et al., 1984) noted a similar overlap in his Maestrichtian sample 28b from Seymour Island, above which only N. frequens was noted in his sample 38. A

Biogeography Wind (1979a, b) undertook a quantitative analysis to show the biogeographic distribution of Campanian Maestrichtian Atlantic nannofossil assemblages, and concluded that the dominant controlling influence was the latitudinal paleotemperature gradient. He distinguished three latitudinal biogeographic provinces, including a southernmost Falkland Plateau Province (Wind, 1979a, fig. 8). This was in contrast to Roth and Bowdler's (1981) depiction of the middle Cretaceous world, for which they discerned only weak latitudinal gradients overriden by stronger neritic oceanic gradients and local influences such as upwelling. Wind's distributions for key high and low latitude biostratigraphic markers that converge at the Falkland Plateau are summarized in Fig.10 (from Wind, 1979a, fig. 11). Thierstein (1981) carried out a global analysis for the latest Cretaceous oceanic assemblages and confirmed the general latitudinal B PALEOLATITUDE

PALEOLATITUDE

LOW w t~

~

MIDDLE

LOW

HIGH

"'::: :

MIDDLE

' "::i:!:i:i:i:i:i:i:i:i:i:i:i:i:!:i:i:i:!:!~,

"'::iiii!il ii!iiii!iiiiiiiii!iiiiiiiiiii!iiiiii!ii!i!iii

::Nephrolithus frequens.:

Z ~ ~lifhus

HIGH

frequens~

====================================================

~

O

Nephrolithus I corysfus-

.< I

(3:

132

t.d W

O

D

C ============================================ ......

================================================================

: Z FT O

I

"'"'""i': ....... '"::"

F(,9 1,1

3<

_J

Fig.9. Four possible distribution patterns for species of the Nephrolithus (modified from Wind, 1979a, fig. 11, A C). Hypothesis "D" is favored by the data of Harwood (in Huber et al., 1984).

168

PALEOLATITUDE LOW --

i

MIDDLE

~::~..:::?..:'.. .~

zl

HIGH I

2

~

~--I or" I (/3

I

gothicus~ i --Uniplanorius 'trifl'dus--~~ " ~.ond /-).

B IT n,"

i

~_ ~ii":quadr '

177 :::::::::::::::::::::::::::::::::::::::::::

if)

iii~eeinho'rdtites'::::::ii::::i::!i!::!~--~ ~-::::::::::::::::::::::::::::::::::::::::::::::::: ¢ ILl I"T

I

.J

I

o_

I

or. i...~9

132

I

,~,,o,,,f,¢,,,,t,,s

~,,~

*" iiiilll~llllllll .~

W

F- Eiffelllfhuseximiu~

IIIIIIIIIIIIIII

Monomorginatuspectinorus and Misceomorg/notus p/eniporus Fig.10. D i s t r i b u t i o n of additional upper C a m p a n i a n and M a e s t r i c h t i a n species used in b i o s t r a t i g r a p h i c zonations (from Wind, 1979a, fig. 11, d f).

paleotemperature control of distributions with the exception of dissolution resistant taxa whose biogeography is strongly modified by paleodepth of deposition (example, Micula decussata). His plot for the distribution of Nephrolithus frequens (Thierstein, 1981, fig. 22) includes the older occurrences of N. corystus, which exceed 20% of the assemblage on the Falkland Plateau. Cenozoic

Biostratigraphy As mentioned previously, Danian strata are missing on the Falkland Plateau, therefore

nannofossil assemblages from this earliest Tertiary stage have only been described in the Southern Ocean region from limited occurrences in the Bellingshausen Sea (Haq, 1976) and the sub-Antarctic of the South Pacific sector (Edwards, 1973). The recent coring of a Cretaceous/Tertiary boundary sequence on Maud Rise (Fig.l), however, will help fill this gap in the stratigraphic puzzle (see Barker et al., this issue). The zones recognized to date for the Cenozoic sequence in the vicinity of the Falkland Plateau are summarized in Fig.ll, which is a composite from several incomplete sections drilled at DSDP Sites 327, 330, 511, and 513. As with the Mesozoic zonation presented previously, this scheme includes a number of provincial zones and datums interspersed with more cosmopolitan markers that aid correlation with lower latitude zonations. Due to the more abbreviated nature of the sections studied, this zonation is less complete than those developed for the Subantarctic Paleogene of the New Zealand (Edwards, 1971; Waghorn, in Perch-Nielsen, 1985b, fig. 4). The nannofossiliferous Cenozoic section on the Falkland Plateau begins near the base of the upper Paleocene with the Fasciculithus tympaniformis Zone (= F. involutus Zone of Wise and Wind, 1977, and CP4), which is succeeded by the provincial Heliolithus universus Zone. The latter is dominated by the nominate species, and has been encountered in a piston core from the southernmost segment of the Southwest Indian Ridge, southwest of the Falkland Plateau (Wise et al., in press). The Discoaster multiradiatus Zone in Hole 329 contains a relatively diverse assemblage with abundant D. multiradiatus in some intervals, which is indicative of the relatively warm and equatable global climate of that time. Included, however, is the distinctive high latitude taxon, Hornibrookina australis, which has a well developed bipolar distribution. Ancestral forms have been described from the Danian of New Zealand and Tunisia (Perch-Nielsen, 1985a). The Eocene is poorly represented in the

169

AGE

I

•

ZONE

DATUM LEVEL

SUBZONE

Em/7/bmo huxley/ i i i ~i~i i i ii~iiiiiii ?iiiiii!ii i¸ iiiiiiiiiiiii?iii

EARLY MIOCENE ~ b i s e c t u s

F~et/cu/ofenestra b/secto Ch/osmolithus o/tus t?et/cu/ofenestro davies/'/" EARLY OLIGOCENE C/ous/coccus fenestratus B/ock#es sp/nosus Reticulofenestro oomoruens/s LATE EOCENE I--~-hmolithus recurvus LATE OLIGOCENE

i

LAD He#culofenestrG b/sectG bLcecta Last common Ch/bsrnohTiTuso/tus

-~

Retlcu/ofenestro umb/hco C/ous/coccus fenestrotu5 /sthmo/#hus recurvus Discooster sa/ponens/s Refi'cu/ofenestro oarnaruensls /sthmo/#hus recurvus

MIDDLE EC

EARLY EO

L LATE PALEI

Fig.ll. Cenozoic calcareous nannofossil zones recognized in the region of the Falkland Plateau.

Falkland Plateau drill holes due to hiatuses or difficulties encountered in drilling the sections, a problem rectified during the recent Subantarctic ODP Leg 114 (Leg 114 Scientific Party, 1987). It should be possible to recognize in this region many of the conventional lower to middle Eocene zones of Okada and Bukry (1980) in t h a t several of the pertinent zonal marker species have been recognized reworked in piston cores from the area. For example, Discoaster lodoensis is reworked along with upper Paleocene to middle Eocene taxa in VEMA Core 31-74 from the Falkland Plateau (Ciesielski and Wise, 1977), whereas Chiasmolithus gigas and Nannotetrina quadrata are present in ISLAS ORCADAS Core 15-59 taken off the South Orkney Islands (Fig.l) (Toker et al., in press). The presence of these index taxa, particularly the warm water loving species of the discoasters, is attributed to the generally equatable climates that prevailed during the early and middle Eocene. This began to change appreciably by the late Eocene when such taxa became quite scarce at these latitudes (Edwards and Perch-Nielsen, 1975; Wise, 1983).

The global cooling and climatic deterioration which accompanied the formation of a moderate-sized ice sheet on the Antarctic continent during the early Oligocene (see discussions by Wise et al., 1985; Olausson, this issue; Robin, this issue) had resulted in a decreased diversity of the calcareous nannofloras, and this in turn is reflected in the use of a larger number of provincial datum levels to zone the Oligocene sections (Fig.ll). Wise (1983) used a high latitude datum, the last common Chiasmolithus altus, to help subdivide the upper Oligocene. The upper Oligocenelower Miocene sections in the southwest Atlantic, however, were strongly affected by dissolution from ridge flank subsidence (Site 513) or by erosion and reworking of Oligocene taxa as a result of the opening of Drake Passage (Site 329). Some ambiguity remains, therefore, as to the correlation of the Oligocene Miocene boundary with the high latitude coccolith zonation. The lower Miocene is poorly known because the Oligocene/Miocene boundary was interval cored at Site 329, and only one isolated core

170 was assigned to that interval. Further climatic deterioration during the middle Miocene accompanied the formation of the East Antarctic Ice Sheet, and the diversity of the nannoflora dropped below levels that allow a useful zonation to be established for the remainder of the Miocene (Wise et al., 1985, appendix 2). The exceptionally thick, middle to upper Miocene section at Site 329 (Fig.2) is dominated mainly by alternations of two taxa, Coccolithus pelagicus and Reticulofenestra perplexa, the latter representing the colder surface waters. During the latest Miocene and the onset of West Antarctic glaciation, surface waters in the region became inhospitable for calcareous nannoplankton, and only minor Pliocene occurrences of calcareous nannofossils have been reported from localities close to the present day Polar Front (example, Site 514; Wise, 1983). Holocene assemblages of the Emiliania huxleyi Zone, however, are today widespread over promontories in the vicinity of the Polar Front, including the Falkland Plateau, and reflect in part the sharp global descent of the CCD which began during the Pliocene.

well defined migration of high-latitude nannoflora into the mid-latitudes during the middle Oligocene. This latter followed a previous minor cooling during the early Oligocene. These initial studies could today be further refined in view of the large number of additional new sites that have been drilled by DSDP/ODP. Haq (1980) studied the Miocene of the Atlantic basins in more detail, using holes from various DSDP cruises between Legs 1 and 47. The long section from DSDP Hole 329 on the Falkland Plateau (Fig.2) was the only one available to them from the high latitude South Atlantic. There a somewhat temperate Coccolithus pelagicus dominated assemblage was replaced by a colder, Reticulofenestra perplexa (= Dictyococcites antarcticus of Haq) association at about 15 Ma in the middle Miocene, coincident with the development of the East Antarctic Ice Sheet. These two assemblages and a third (the R. pseudoumbilica and R. haqii assemblage) alternated through several climatic cycles thereafter as glacial conditions waxed and waned on Antarctica through the remainder of the middle and late Miocene (Haq, 1980, fig. 12).

Paleo-oceanograph y During the 1970's, Haq and his colleagues undertook a major effort to decipher Cenozoic paleo-climatic trends for the Atlantic Basins through a quantitative analysis of shifts in biogeographic patterns through time. Their Paleogene study spanned the first 15 DSDP cruises and was summarized by Haq and Lohmann (1976) with subsequent updates to include the South Atlantic Basin and Falkland Plateau by Haq et al. (1977a, b). They compared their results with those from terrestrial floral and oxygen isotope patterns, and found general agreement within the limits of their resolution (Haq and Lohmann, 1976, fig. 15). They postulated a maximum equatorward migration (cooling) of high- and mid-latitude nannofloras in the mid-late Paleocene (58 Ma), a major poleward migration (warming) at the early-middle Eocene boundary (49 Ma), and a

Nannofossil deposition in Antarctic intracratonic basins An important discovery of the present decade has been a report by Harwood (1984) of reworked Paleogene nannofossils in Pliocene samples from the Sirius Group, a series of glacial tills along the Transantarctic Mountains (McKelvey et al., in press). Toker et al. (in press) identify a specimen figured by Harwood (1984, fig. 2[9]) as Chiasmolithus solitus, a lower to middle Eocene coccolith abundant in deep sea carbonate oozes surrounding the Antarctic continent. Harwood's finding, accompanied by other Paleogene siliceous and calcareous microfossils, support the suggestion by Webb et al. (1984) that Eocene carbonate sediments were deposited within the interior seaways (Wilkes-Pensacola Basins) of Antarctica prior to the advent of continental

171

glaciation. Calcareous microfossils would subsequently have been eroded from those basins and deposited with the Sirius Formation tills by the East Antarctic Ice Sheet as it overrode the Transantarctic Mountains, perhaps when the mountain range stood at a lower elevation. Another interesting reworked Eocene nannofossil assemblage has been reported by Gazdzicka and Gazdzicki (1985) from King George Island off the n o r t h e r n Antarctic Peninsula (Fig.l). The nannofossils were found adhering to the tests of planktonic foraminifera recovered from a Chlamys coquina (previously known as the "Pecten conglomerate", but now designated the Low Head Member of the Polonez Cove Formation). The Chlamys bed is believed to be Oligocene in age and glacio-marine in origin (Birkenmajer and Gazdzicki, 1986). The nannofossil assemblage was originally considered to be Oligocene in age as well (Gazdzicka and Gazdzicki, 1985), but Toker et al. (in press) concluded t h a t it is a reworked middle Eocene assemblage, as suggested by Birkenmajer (1987; see also Birkenmajer and Gazdzicki, 1986). Birkenmajer (1985, fig. 12) further suggests t h a t the material could have been ice-rafted from the interior of the Antarctic continent, where it would have originally been deposited within an interior basin. These two occurrences, if interpreted correctly (particularly in the case of the Sirius Group), provide the most direct evidence yet to suggest that carbonate deposition may have occurred in the intracratonic basins of Antarctica prior to the formation of continental ice caps. Confirmation of this hypothesis must await more direct exploration of these basins, such as by drilling through the present ice cover into the sedimentary sequence below.

S u m m a r y and c o n c l u s i o n s The Mesozoic-Cenozoic evolutionary development of high southern latitude calcareous nannofossils parallels the development of the Southern Hemisphere ocean basins and climates. Equitable Middle to Late Jurassic

climates resulted in widely dispersed taxa that permit the application of a cosmopolitan zonation for the Falkland Plateau. Shallow restricted basins over southern Gondwanaland, however, did support high latitude species and one of these can be used as an alternate provincial zonal marker. The restricted embryonic Early Cretaceous South Atlantic Basin supported sporadic blooms of monospecific or low diversity assemblages composed of high latitude bipolar taxa. The influx of more diverse, warmer Tethyan assemblages did not occur until the Aptian. Bipolar or austral taxa remain conspicuous members of the assemblage and are useful as local zonal markers, particularly in the Campanian-Maestrichtian. In contrast to the middle Cretaceous, the global sample coverage from DSDP holes is sufficient for the uppermost Cretaceous to show a distinct latitudinal distribution of species and assemblages. The larger ocean basins and wider dispersal of the continents also lessened local influences such as upwelling on the general distributional patterns. Provincial taxa are present but remained minor components of the Paleocene-Eocene Southern Ocean assemblages. Quantitative methods, however, clearly distinguish high latitude from low latitude assemblages and reveal fluctuations through time that mirrored changes in paleoclimates. Indirect evidence suggests that calcareous nannofossils were deposited in the interior basins of Antarctica during the early Cenozoic. Species diversities declined during the Oligocene in response to climatic cooling and the glaciation of the Antarctic continent, and local provincial zonations are used for much of this epoch. Miocene diversities dropped dramatically to the point that conventional zonations cannot be applied at high southern latitudes. Important climatic events are discernible, however, through statistical analysis of the assemblages. These are generally dominated by high latitude taxa. Plio-Pleistocene sediments deposited beneath the expanding Antarctic water mass are essentially devoid of calcareous

172 nannofossils, but are widely present in the S u b a ntar ctic region as a result of the amelioration in Holocene climates and the descent of the CCD th at had begun during the Pliocene.

Remarks: " G e p h y r o " is from the Greek mean-

Acknowledgments

1-6; Plate II, 1-5)

I am grateful to Professor Eric Olausson and the Organizing Committee of the Hans Petterson Symposium II for their invitation to present this paper and to the FSU Foundat i on for a travel g r an t to attend. Mr. Thomas Fellers operated the scanning-transmission electron microscope, and Mrs. Rosemarie Raymond drafted the figures. Mr. Wuchang Wei prepared the plates and assisted in the p re p ar atio n of the manuscript. I particularly t h a n k Dr. F r a n k H. Wind (Texaco, Inc., Denver) for the use of Figs. 9 and 10 from his unpublished Ph.D. dissertation. The study was supported by NSF grant DPP 84-14268 and an equipment g r an t from the Amoco Foundation.

Amphizygus(?) sp., Wise, 1983, p. 494, table lB.

ing bridge. The genus is assigned to the Family Biscutaceae Black (1971).

Gephyrobiscutum diabolum Wise, n. sp. (Plate I,

Appendix A -- systematic paleontology Calcareous nannofossil species mentioned in the text are listed at the end of this appendix. In addition, the following new taxa are described:

Genus

Gephyrobiscutum Wise, n. gen.

Type species: Gephyrobiscutum diabolum Wise, n. sp.

Diagnosis: Elliptical coccoliths with a podorhabdid rim enclosing an open central area bisected by a bar along the minor axis. The bar is composed of two solid elements t h a t extend from the rim to join along a suture near the center.

Diagnosis: A small species of Gephyrobiscutum characterized by a thin, wall-like central area bar from which two long horns project distally at each end where the bar intersects the rim. From the point of intersection with the rim, the tip of each bar element is extended a short distance along the rim dextrally (as seen in distal view) to form a 90 ° corner angle with the bar. Description: This taxon is quite small, between about 3 and 4 ~m long. The width of the central opening is approximately one third the width of the coccolith (or about the width of the rim). The bar alignment ranges from nearly parallel (Plate I, 1, right) to within about 15° (Plate I, 3) of the minor axis. The central suture along which the bar elements meet may be quite near (Plate I, 2) or somewhat off (Plate I, 4) the mid point of the bar. The devil-like " h o r n s " are quite long and may project distally as much as 1.4 ~m above the distal shield (Plate I, 6). The shields are well separated (Plate I, 6) and consist of between 16 and 20 petaloid elements. On the distal surface of the distal shield of well preserved specimens, each element is rimmed by a raised ridge except along the outer margin. The elements are widest at the ends of the ellipse as is characteristic of most members of this family. In proximal view (Plate II, 1-3), the central area is lined by a row of small t abul ar elements, and small

PLATE I

Gephyrobiscutum diabolum n. gen., n. sp., DSDP Sample 511-33-1, 50cm; all figures scanning-transmission electron micrographs (STEM). 1-5. Distal views: 1, paratype, 9500 x ; 2, holotype, 24,800 x ; 3, paratype, 25,000 x ; 4, paratype, 16,000 ×. 6. Lateral view; paratype, 29,000 x.

173 PLATEI

174 P L A T E II

Gephyrobiscutum diabolum n. gen., n. sp., paratypes, DSDP Sample 511-33-1, 50 cm. 1 3. STEM micrographs, proximal views: 1, 20,000 x ; 2, 31,000 x ; 3, same specimen, 20,000 x. 4. Phase contrast light, 5500 x. 5. Cross-polarized light, 5500 x.

granular elements form a substrate beneath t h e c e n t r a l bar. S p e c i m e n s a p p e a r d a r k in p h a s e c o n t r a s t l i g h t ( P l a t e II, 4), a n d t h e shields r e m a i n a t e x t i n c t i o n w h e n r o t a t e d in c r o s s - p o l a r i z e d l i g h t ( P l a t e II, 5). T h e bar, h o w e v e r , is h i g h l y b i r e f r i n g e n t u n d e r crossed nicols w h e n t h e m a j o r a n d m i n o r a x e s of t h e c o c c o l i t h a r e a l i g n e d p a r a l l e l to t h e p o l a r i z i n g d i r e c t i o n s ( P l a t e II, 6), a n d this c h a r a c t e r i s t i c allows t h e

m i n u t e s p e c i m e n s to be r e c o g n i z e d r e a d i l y in t h e light m i c r o s c o p e . Remarks: T h e specific n a m e is f r o m t h e Latin, m e a n i n g devil. T h i s is t h e m o s t a b u n d a n t t a x o n y e t e n c o u n t e r e d in d i v e r s e Mesozoic s a m p l e s e x a m i n e d by this writer. I t is the o n l y s u c h species logged in t h e c a t e g o r y " h i g h l y a b u n d a n t " on o u r r a n g e c h a r t s (over 100 s p e c i m e n s p e r field of v i e w a t m a g n i f i c a t i o n s of 1000 x ; see Wise, 1983, t a b l e 1B). T h i s h i g h

175 abundance at its first appearance datum renders this an excellent provincial stratigraphic marker. Occurrence: Highly a b u n d a n t (example, Plate I, 1) to few in the lower Campanian of DSDP Hole 511, Falkland Plateau. Size: 3.2 4.2 ~m long, 2.4-3.0 pm wide; Holotype 3.2 x 2.5 ~m. Holotype: Plate I, 2. Paratypes: Plate I, 1, 3 6; Plate II, 1-5. Type locality: DSDP Sample 511-33-1, 50 cm.

Genus StephanoHthion Noel, 1956

Stephanolithion bigotii brevispinus Wind and Wise, n. ssp.

Stephanolithion bigotii Deflandre, Wise and Wind, 1977, pl. 79, figs. 1-3, pl. 89, figs. 1 3. Stephanolithion bigotii Deflandre (short lateral spines), Wise, 1983, pl. 34, figs. 3, 4. Diagnosis: A small species of Stephanolithion characterized by numerous short lateral arms and, where preserved, a tall central spine. Description: The rim of the elliptical specimens average 4-5 pm in length. About 25-30 vertical elements comprise the distal cycle. About a third to nearly a half of these elements may extend outwards at the top of the rim to form relatively short lateral spines of various lengths. These lateral spines may approach in length the width of the central area, but are generally far shorter t han that. Differentiation: Medd (1979) subdivided S. bigotii into two subspecies based on size. The smaller of these, S. bigotii bigotii, is similar in size to S. bigotii brevispinus, but differs in having only 6-7 lateral spines which are approximately equal in length to the width of the central area. Stephanolithion bigotii brevispinus generally has 9-12 lateral spines, most of which are considerably less t han the width of the central area. Stephanolithion bigotii maximum Medd is larger in size (greater t han 6 ~m long) and has only 6-7 lateral spines. It has been suggested (K. Cooper, pers. comm., 1987) t h a t Corollithion helotatus Wind

and

Wise (1977) may be conspecific with

Stephanolithion brevispinus based on similarities in the construction of the central spine and its four basal supports. We, however, see no convincing evidence for lateral spines on the holotype of C. helotatus, and note t hat the vertical elements of the rim of this species are exceedingly thin and tilt inwards. Those of S. brevispinus are t hi cker and tend to flare outwards. It is conceivable, however, t hat C. helotatus could be an end member with no lateral spines within the S. bigotii plexus, in which case it could be treated as a n o t h e r subspecies of S. bigotii. Occurrence: Rare to few in the Lower Tithoni a n - O x f o r d i a n of DSDP Holes 330 and 511 on the Falkland Plateau. Size: Rim 3.3 5 ~m long, 2.3 3.6 pm wide. Holotype: plate 34, fig. 3 of Wise (1983). Paratypes: plate 79, figs, 1 3 and plate 89, figs, 1 3 of Wise and Wind (1977). Type locality: DSDP Sample 511-66-2, 24 cm.

Appendix B---zonation The zonation for the Falkland Pl at eau area summarized in Fig.3 includes several name changes of defining taxa as well as the following modifications to the schemes compiled by Wise and Wind (1977) and Wise (1983):

Stephanolithion bigotii brevispinus Zone Definition: Interval from the FAD of Stephanolithion bigotii brevispinus to the FAD of Zeugrhabdotus embergeri. Reference locality: DSDP Hole 511, 554-599 m. Remarks: This is a provincial, high-latitude al t ernat e zone t hat can be used in place of the more cosmopolitan Vekshinella stradneri Zone of Roth et al. (1983). This zone was referred to informally as the Stephanolithion sp. Zone by Wise (1983).

Prediscosphaera columnuta Zone Definition: Interval from the FAD of Prediscosphaera columnuta to the FAD of Tranolithus orionatus.

176

Reference locality: D S D P H o l e 511, 454-491 m. Remarks: T h i s zone e n c o m p a s s e s t h e lowerm o s t two s u b z o n e s of t h e Prediscosphaera cretacea Z o n e as d e l i m i t e d by Wise (1983) for the F a l k l a n d P l a t e a u . It, t h e r e f o r e , s p a n s t h e l o w e r h a l f of t h e P. cretacea or P. columnuta Zones of m a n y a u t h o r s .

Tranolithus orionatus Zone Definition: I n t e r v a l f r o m t h e F A D of Tranolithus orionatus to t h e F A D of EiffeUithus turriseiffelii. Reference locality: D S D P H o l e 511, 434-451 m. Remarks: T h i s zone e n c o m p a s s e s t h e upperm o s t t w o s u b z o n e s of t h e Prediscosphaera cretacea Zone as d e l i m i t e d by Wise (1983) for the F a l k l a n d P l a t e a u . T h u s it s p a n s t h e u p p e r h a l f of t h e P. cretacea or P. columnuta Zone of m a n y a u t h o r s . To a c c o m m o d a t e this c h a n g e , the n a m e of t h e f o r m e r T. orionatus S u b z o n e of Wise (1983) is h e r e c h a n g e d to r e a d "Repagulum parvidentatum S u b z o n e " .

Gartnerago costatum S u b z o n e of t h e Marthasterites furcatus Zone Definition: I n t e r v a l f r o m t h e L A D of Lithastrinus floralis to t h e F A D of Gephyrobiscutum diabolum n. sp. Reference section: D S D P H o l e 511, 349-363 m. Gephyrobiscutum diabolum S u b z o n e of t h e Marthasterites furcatus Zone Definition: I n t e r v a l f r o m t h e F A D of Gephyrobiscutum diabolum n. sp. to t h e L A D of Marthasterites furcatus or t h e F A D of Biscutum coronum. Reference section: D S D P H o l e 511, 226-348 m. Species list Chiasmolithus altus Bukry and Percival, 1971 Chiasmolithus gigas (Bramlette and Sullivan) Hay and Mohler, 1967 Rhagodiscus angustus (Stradner) Reinhardt, 1971 Hornibrookina australis Edwards and Perch-Nielsen, 1975 Watznaueria barnesae (Black in Black and Barnes) PerchNielsen, 1968

Stephanolithion bigotii bigotii Deflandre, 1939 Stephanolithion bigotii brevispinus, Wind and Wise n. ssp. Stephanolithion bigotii maximum Medd, 1979 Reticulofenestra bisecta bisecta (Hay, Mohler, and Wade) Roth, 1970 Prediscosphaera columnata (Stover) Perch-Nielsen, 1984 Biscutum constans (Gorka) Black in Black and Barnes, 1959 Nephrolithus corystus Wind, 1983 Gartnerago costatum (Gartner) Bukry, 1969 Prediscosphaera cretacea (Arkhangelsky) Gartner, 1968 Cruciellipsis cuvillieri (Manivit) Thierstein, 1971 Micula decussata decussata Vekshina, 1959 Gephyrobiscutum diabolum Wise, n. sp. Biscutum dissimilis Wind and Wise in Wise and Wind, 1977 Thiersteinia ecclesiastica Wise, 1983 Zeugrhabdotus embergeri (No~l) Perch-Nielsen, 1984 Sollasites falklandensis Filewicz et al. in Wise and Wind, 1977 Lithastrinus floralis Stradner, 1962 Nephrolithus frequens Gorka, 1957 Marthasterites furcatus (Deflandre in Deflandre and Fert) Deflandre, 1959 Nannotetrina quadrata (Bramlette and Sullivan) Bukry, 1973 Reticulofenestra haqii Backman, 1978 Corollithion helotatus Wind and Wise in Wise and Wind, 1977 Emiliania huxleyi (Lohmann) Hay and Mohler in Hay et al., 1967 Fasciculithus involutus Bramlette and Sullivan, 1961 Kamptnerius magnificus Deflandre, 1959 Discoaster multiradiatus Bramlette and Riedel, 1954 Tranolithus orionatus Stover, 1966 Broinsonia parca (Stradner) Bukry, 1969 Repagulum parvidentatum (Deflandre and Fert) Forchheimer, 1972 Coccolithus pelagicus (Wallich) Schiller, 1930 Reticulofenestra perplexa (Burns) Wise, 1983 Seribiscutum primitivum (Thierstein) Filewicz, Wind and Wise in Wind and Wise, 1983. Reticulofenestra pseudoumbilica (Gartner) Gartner, 1969 Crucibiscutum salebrosum (Black) Jakubowski, 1986 Corollithion silvaradion Filewicz, Wind and Wise in Wise and Wind, 1977 Chiasmolithus solitus (Bramlette and Sullivan) Locker, 1968 Vekshinella stradneri Rood, Hay and Barnard, 1971 Fasciculithus tympaniformis Hay and Mohler in Hay et al., 1967 Eiffellithus turriseiffelii (Deflandre in Deflandre and Fert) Reinhardt, 1965 Heliolithus universus Wind and Wise in Wise and Wind, 1977

References Applegate, J. and Bergen, J.A., in press. Mesozoic nannofossils from ODP Leg 103. In: G. Boillot, E. L. Winterer et

177 al., Proc. ODP Sci. Results, 10. ODP, College Station, Tex. Barker, P. F., Dalziel, I. W. D. et al., 1977. Evolution of the Southwestern Atlantic Ocean Basin: results of Leg 36, Deep Sea Drilling Project. In: P. F. Barker, I. W. D. Dalziel et al., Initial Reports of the Deep Sea Drilling Project, 36. U.S. Government P r i n t i n g Office, Washington, D.C., pp. 991 1014. Birkenmajer, K., 1985. Onset of Tertiary continental glaciation in the Antarctic Peninsula sector (West Antarctica). Acta Geol. Pol., 35: 1- 30. Birkenmajer, K., 1987. Oligocene Miocene glacio-marine sequences of King George Island (South Shetland Islands), Antarctica. Palaeontol. Pol., 49: 9-36. Birkenmajer, K. and Gazdzicki, A., 1986. Oligocene age of the Pecten conglomerate on King George Island, West Antarctica. Bull. Pol. Acad. Sci., Terre, 34: 219-226. Burns, D. A., 1975. Nannofossil biostratigraphy for Antarctic sediments, Leg 28, Deep Sea Drilling Project. In: D. E. Hayes, L. A. Frakes et al., Initial Reports of the Deep Sea Drilling Project, 28. U.S. Government P r i n t i n g Office, Washington, D.C., pp. 589 598. Ciesielski, P. F. and Wise, S. W., 1977. Geologic history of the Maurice Ewing Bank of the Falkland Plateau (Southwest Atlantic sector of the Southern Ocean) based on piston and drill cores. Mar. Geol., 25: 175-207. Covington, M., 1985. New morphologic information on Cretaceous nannofossils from the Niobrara Formation (Upper Cretaceous). Geology, 13:683 686. Crux, J. A., 1982. Upper Cretaceous (Cenomanian to Campanian) calcareous nannofossils. In: A. R. Lord (Editor), A Stratigraphical Index of Calcareous Nannofossils. Ellis Horwood, Chichester, pp. 81 135. Dingle, R. V., Siesser, W. G. and Newton, A. R., 1983. Mesozoic and Tertiary Geology of S o u t h e r n Africa. Balkema, Rotterdam, 354 pp. Edwards, A. R., 1971. A calcareous n a n n o p l a n k t o n zonation of the New Zealand Paleogene. In: A. Farinacci (Editor), Proc. 2nd Planktonic Conf., Roma, 1970, 1, pp. 381 419. Edwards, A. R., 1973. Calcareous nannofossils from the southwest Pacific, Deep Sea Drilling Project, Leg 21. In: R. E. Burns, J. E. Andrews et al., Initial Reports of the Deep Sea Drilling Project, 21. U.S. Government P r i n t i n g Office, Washington, D.C., pp. 641-691. Edwards, A. R. and Perch-Nielsen, K., 1975. Calcareous nannofossils from the southern Southwest Pacific. In: J. P. Kennett, R. E. Houtz et al., Initial Reports of the Deep Sea Drilling Project, 29. U.S. Government P r i n t i n g Office, Washington, D.C., pp. 469-539. Gazdzicka, E. and Gazdzicki, A., 1985. Oligocene coccoliths of the Pecten conglomerate, West Antarctica. Neues Jahrb. Geol. Palaeontol. Monatsh., 12: 727-735. Harwood, D. M., 1984. Diatoms from the Sirius Formation, T r a n s a n t a r c t i c Mountains. Antarct. J. U.S., 5: 98-100. Haq, B. U., 1976. Coccoliths in cores from the Bellingshausen abyssal plain and Antarctic c o n t i n e n t a l rise. In: C. D. Hollister, C. Craddock et al., Initial Reports of the Deep Sea Drilling Project, 35. U.S. Government P r i n t i n g Office, Washington, D.C., pp. 557 567.

Haq, B. U., 1980. Biogeographic history of Miocene calcareous n a n n o p l a n k t o n and paleoceanography of the Atlantic Ocean. Micropaleontology, 26: 414-443. Haq, B. U., Hardenbol, J. and Vail, P. R., 1987. Chronology of fluctuating sea levels since the Triassic. Science, 235: 1156- 1167. Haq, B. U. and Lohmann, G. P., 1976. Early Cenozoic calcareous n a n n o p l a n k t o n biogeography of the Atlantic Ocean. Mar. Micropaleontol., 1:119 194. Haq, B.U., Lohmann, G. P. and Wise, S. W., 1977. Calcareous n a n n o p l a n k t o n biogeography and its paleoclimatic implications: Cenozoic of the Falkland plateau (DSDP Leg 36) and Miocene of the Atlantic Ocean. In: P. F. Barker, I. W. D. Dalziel et al., Initial Reports of the Deep Sea Drilling Project, 36. U.S. Government P r i n t i n g Office, Washington, D.C., pp. 745 760. Haq, B. U., Perch-Nielsen, K. and Lohmann, G. P., 1977. Contribution to the Paleocene calcareous nannofossil biogeography of the central and southwest Atlantic Ocean (Ceara Rise and Sao Paulo Plateau, DSDP Leg 39). In: K. Perch-Nielsen, P. R. Supko et al., Initial Reports of the Deep Sea Drilling Project, 39. U.S. Government Printing Office, Washington, D.C., pp. 841 848. Hay, W. W., 1981. Sedimentological and geochemical trends resulting from the breakup of Pangaea. In: Proc. 26th Int. Geol. Congr., Geology of Oceans, Paris, July 7 17, 1980. Oceanol. Acta, 4 (suppl.): 135 147. Huber, B. T., Harwood, D. M. and Webb, P. N., 1984. Upper Cretaceous microfossil biostratigraphy of Seymour Island, Antarctic Peninsula. Antarct. J. U.S, 19:72 74. Jakubowski, J., 1987. A proposed Lower Cretaceous calcareous nannofossil zonation scheme for the Moray Firth area of the North Sea. In: H. Stradner and K. Perch-Nielsen (Editors), Proc. Int. N a n n o p l a n k t o n Assoc., Vienna Meet., 1985. Abh. Geol. Bundesanst. (Wien), 39: 99-119. Kotova, I. Z., 1983. Palynological study of Upper Jurassic and Lower Cretaceous sediments, Site 511, Deep Sea Drilling Project Leg 71 (Falkland Plateau), In: W. J. Ludwig, V. A. K r a s h e n i n n i k o v et al., Initial Reports of the Deep Sea Drilling Project, 71. U.S. Government P r i n t i n g Office, Washington, D.C., pp. 879 906. 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. In: W. J. Ludwig, V. A. K r a s h e n i n n i k o v et al., Initial Reports of the Deep Sea Drilling Project, 71. U.S. Government P r i n t i n g Office, Washington, D.C., pp. 789 820. Larson, R. L. and Ladd, J. I., 1974. Evidence for the opening of the South Atlantic in the Early Cretaceous. Nature, 246:209 212. Leg 113 Scientific Party, 1987. Glacial history of Antarctica. Nature, 328: 115-116. Leg 114 Scientific Party, 1987. Palaeoceanography of the subantarctic South Atlantic. Nature, 328:671 672. Ludwig, W. J., Krasheninnikov, V. A. et al., 1983. Initial Reports of the Deep Sea Drilling Project, 71. U.S. Government P r i n t i n g Office, Washington, D.C., 1187 pp. MacIntyre, A. and B6, A. W. H., 1967. Modern Coccolitho-

178 phoridae of the Atlantic Ocean. I. Placoliths and cytoliths. Deep-Sea Res., 14: 561-597. McCoy, F. W. and Zimmerman, H., 1977. A history of sediment lithofacies in the South Atlantic Ocean. In: K. Perch-Nielsen, P. R. Supko et al., Initial Reports of the Deep Sea Drilling Project, 39. U.S. Government Printing Office, Washington, D.C., pp. 1047-1080. Mortimer, C. P., 1987. Upper Cretaceous calcareous nannofossil biostratigraphy of the Southern Norwegian and Danish North Sea area. In: H. Stradner and K. Perch-Nielsen (Editors), Proc. Int. Nannoplankton Assoc. Vienna Meeting, 1985. Abh. Geol. Bundesanst. (Wien), 39: 143- 175. Mutterlose, J., 1986. Upper Jurassic belemnites from the Orville Coast, Western Antarctica, and their palaeobiogeographical significance. Br. Antarct. Surv. Bull., 70: 1 22. Mutterlose, J., 1987. Temperature controlled migration of calcareous nannofossils in the NW-European Aptian. INA Newsl., 9:57 (abstract). Parker, M. E., Arthur, M. A., Wise, S. W. Jr. and Wenkam, C. R., 1983. Carbonate and organic carbon cycles in Aptian-Albian black shales at Deep Sea Drilling Site 511, Falkland Plateau. In: W. J. Ludwig, V. A. Krasheninnikov et al., Initial Reports of the Deep Sea Drilling Project, 71. U.S. Government Printing Office, Washington, D.C., pp. 1051-1072. Perch-Nielsen, K., 1985a. Cenozoic calcareous nannofossils. In: H. M. Bolli, J. B. Saunders and K. Perch-Nielsen (Editors), Plankton Stratigraphy. Cambridge Univ. Press, pp. 427-554. Perch-Nielsen, K., 1985b. Mesozoic calcareous nannofossils. In: H. M. Bolli, J. B. Saunders and K. Perch-Nielsen (Editors), Plankton Stratigraphy. Cambridge Univ. Press, pp. 329-426. Roth, P. H., 1978. Cretaceous nannoplankton biostratigraphy and oceanography of the northwestern Atlantic Ocean. In: W. E. Benson, R. E. Sheridan et al., Initial Reports of the Deep Sea Drilling Project, 44. U.S. Government Printing Office, Washington, D.C., pp. 731 759. Roth, P. H., 1981. Mid-Cretaceous calcareous nannoplankton from the Central Pacific: implications for paleoceanography. In: J. Thiede, T. L. Vallier et al., Initial Reports of the Deep Sea Drilling Project, 62. U.S. Government Printing Office, Washington, D.C., pp. 471 489. Roth, P. H. and Bowdler, J. L., 1981. Middle Cretaceous calcareous nannoplankton biogeography and oceanography of the Atlantic Ocean. Soc. Econ. Paleontol. Mineral. Spec. Publ., 32: 517-546. Roth, P. H. and Krumbach, K. R., 1986. Middle Cretaceous calcareous nannofossil biogeography and preservation in the Atlantic and Indian Oceans: Implications for paleoceanography. Mar. Micropaleontol., 10: 235-266. Roth, P. R., 1986. Mesozoic palaeoceanography of the North Atlantic and Tethys Oceans: In: C. P. Summerhayes and N. J. Shackleton (Editors), North Atlantic Palaeoceanography. Geol. Soc. Spec. Publ., 21: 35-66. Roth, P. H., Medd, A. and Watkins, D., 1983. Jurassic calcareous nannofossil zonation, an overview with new

evidence from Deep Sea Drilling Project Site 534. In R. E. Sheridan, F. M. Gradstein, et al., Initial Reports of the Deep Sea Drilling Project, 76. U.S. Government Printing Office, Washington, D.C., pp. 573-580. Shafik, S., 1985. Cretaceous coccoliths in the middle Eocene of the western and southern margins of Australia: evidence of a significant reworking episode. BMR. J. Aust. Geol. Geophys., 9:353 359. Sissingh, W., 1977. Biostratigraphy of Cretaceous calcare. ous nannoplankton. Geol. Mijnbouw, 56: 37-50. Stapleton, R. P. and Beer, E. M., 1977. Micropalaeontological age for the Brenton Beds. In: Papers on Biostratigraphic Research. Bull. Geol. Surv. S. Afr., 60: 1-10. Taylor, R. J., 1982. Lower Cretaceous (Ryanzanian to Albian) calcareous nannofossils. In: A. L. Lord (Editor), A Stratigraphical Index of Calcareous Nannofossils. Ellis Horwood, Chichester, pp.40-80. Thierstein, H. R., 1974. Calcareous nannoplankton: Leg 26, Deep Sea Drilling Project. In: T. A. Davies, B. P. Luyendyk et al. (Editors), Initial Reports of the Deep Sea Drilling Project, 26. U.S. Government Printing Office, Washington, D.C., pp. 619-667. Thierstein, H. R., 1976. Mesozoic calcareous nannoplankton biostratigraphy of marine sediments. Mar. Micropaleontol., 1: 325-362. Thierstein, H. R., 1979. Paleoceanographic implications of organic carbon and carbonate distribution in Mesozoic deep-sea sediments, In: M. Talwani, W. B. F. Ryan and W. Hay (Editors), 2nd Maurice Ewing Symposium: Deep Drilling in the Atlantic Ocean. Am. Geophys. Union, Washington, D.C., pp. 249 274. Thierstein, H. R., 1977. Mesozoic calcareous nannofossils from the Indian Ocean, DSDP Legs 22 to 27. In: J. R. Heirtzler, H. M. Bolli, T. A. Davies, J. B. Saunders and J. Sclater (Editors), Indian Ocean Geology and Biostratigraphy. American Geophys. Union, Washington, D.C., pp. 339-351. Thierstein, H. R., 1981. Late Cretaceous nannoplankton and the change at the Cretaceous Tertiary boundary. Soc. Econ. Paleontol. Mineral. Spec. Publ., 32: 355-394. Toker, V., Barker, P. F. and Wise, S. W., in press. Middle Eocene carbonate-bearing marine sediment from Bruce Bank off the northern Antarctic Peninsula. In: Fifth Int. Symp. Antarctic Earth Sciences. Cambridge Univ. Press, Cambridge. Watkins, D. K., 1986. Calcareous nannofossil paleoceanography of the Cretaceous Greenhorn Sea. Geol. Soc. Am. Bull., 97:1239 1249. Wind, F. H., 1979a. Late Campanian and Maestichtian calcareous nannoplankton biogeography and high-latitude biostratigraphy. Thesis, Florida State Univ., 333 pp. Wind, F. H., 1979b. Maestrichtian-Campanian nannofloral provinces of the southern Atlantic and Indian oceans. In: M. Talwani, W. Hay and W. B. F. Ryan (Editors), Deep Drilling Results in the Atlantic Ocean: Continental Margins and Paleoenvironment (Maurice Ewing Ser., 3). Am. Geophys. Union, Washington, D.C., pp. 123-137. Wind, F. H., 1983. The Genus Nephrolithus Gorka, 1957 (Coccolithophoridae). J. Paleontol., 57: 157-161.

179 Wind, F. H. and Wise, S. W. Jr., 1983. Correlation of Upper Campanian Lower M a e s t r i c h t i a n calcareous nannofossil assemblages in drill and piston cores from the Falkland Plateau, Southwest Atlantic Ocean. In: W. J. Ludwig, V. A. K r a s h e n i n n i k o v et al., Initial Reports of the Deep Sea Drilling Project, 71. U.S. Government Printing Office, Washington, D.C., pp. 551 564. Wise, S. W., Jr., 1982~ Calcareous nannofossils: an update. In: Proc. Third North Am. Paleontol. Conv., 2: 588a 588j. Wise, S. W., Jr., 1983. Mesozoic and Cenozoic calcareous nannofossils recovered by Deep Sea Drilling Project Leg 71 in the Falkland Plateau region, Southwest Atlantic Ocean. In: W. J. Ludwig, V. A. K r a s h e n i n n i k o v et al., Initial Reports of the Deep Sea Drilling Project, 71. U.S. Government P r i n t i n g Office, Washington, D.C., pp. 481 550. Wise, S. W., Jr. and Wind, F. H., 1977. Mesozoic and Cenozoic calcareous nannofossils recovered by DSDP Leg 36, drilling on the Falkland Plateau, SW Atlantic sector of the Southern Ocean. In: P. F. Barker, I. W. D. Dalziel et al., Initial Reports of the Deep Sea Drilling Project, 36. U.S. Government P r i n t i n g Office, Washington, D.C., pp. 296 309.

Wise, S. W. Jr., Ciesielski, P. F., MacKenzie, D. T., Wind, F. H., Busen, K. E., Gombos, A. M., Haq, B. U., Lohmann, G. P., Tjalsma, R. C., Harris, W. K., Hedlund, R. W., Beju, D. N., Jones, D. L., Plafker, G. and Sliter, W., 1980. Paleontologic and paleoenvironmental synthesis for the Southwest Atlantic Ocean basin based on Jurassic to Holocene faunas and floras from the Falkland Plateau. In: C. Craddock (Editor), Antarctic Geoscience. Univ. Wisconsin Press, Madison, pp. 155 163. Wise, S. W., Jr., Gombos, A. M. and Muza, J. P., 1985. Cenozoic evolution of polar water masses, southwest Atlantic Ocean. In: K. J. Hsii and H. J. Weissert (Editors), South Atlantic Paleoceanography. Cambridge Univ. Press, pp. 283 324. Wise, S. W., Jr., Tjalsma, R. C. and Dailey, D. H., in press. Late Paleocene carbonate deposition on the southwest Indian Ridge. In: Fifth Int. Syrup. Antarctic E a r t h Sciences. Cambridge Univ. Press, Cambridge. Vail, P. R., Mitchum, R. M., Jr., Todd, R. G., Widmeir, S., Thompson, S., III, Sangree, J. B. and Hatlelid, W. G., 1977. Seismic stratigraphy and global changes of sea level. In: C. E. Payton (Editor), Seismic Stratigraphy Applications to Hydrocarbon Exploration. Am. Assoc. Pet. Geol., Mem., 26:49 212.