MARINE GEOLOGY OF THE WEDDELL SEA REGION

John B, Anderson Department of Geology Rice University

February,1984 1

MARINE GEOLOGY OF THE WEDDELL SEA REGION

Physiography

The · Weddell Sea shelf, like other parts. of the Antaretie eontinental shelf, is eharaeterized by rugged topography and great depth (average depth 500m). Crary Trough, loeated in the south­ eastern Weddell .Sea, is the physiographie dividing line between the narrow (lOOkm) East Antaretie shelf and broad (several hundred, kilometers) West Antaretie eontinental shelf. The West Antaretie shelf extends beneath the Ronne-Filehner lee Shelf to a deep (up to l700m) areuate depression (Thiel Trough); these iee shelves are grounded at approximately 1100m in this depression (Fig. 1). Figura 1 shows that the southern shelf is isolated from the eontinent on all si:des by this depression. The eontinental shelf in the \vestern

Weddell Sea has been virtually unexplored due to severe sea iee eover in this region.

The upper eontinental slope of the East Antaretie margin is

0 quite steep (7-9 ) and the lower slope and rise is eut by numerous submarine eanyons. In eontrast, the West Antaretie margin is eharaeterized by a more gentle upper slope, and submarine eanyons are fewer and more widely spaeed. The eontinental rise is mueh more extensive in the Western Weddell Sea than on the eastern margin. The abyssal plain is relatively flat, exeept in the . northernmost Weddell Sea where seamounts, ridges, and linear de­ pressions eontribute to the generally .: irregular topography of the region. See Johnson et ale (1981) for a more detailed deserip­ tion of the bathymetry of the Weddell Sea. \'. ~ ,-_-.!!>..;.--./ ;1 . ~ -;' · 1c.· )-" " .~ .". o r- .. " p .; .... r", I '-J ~.i; .~ t

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'._L : 1 i20o,AI-L.J _.1.. ___L.J-L.:.... j 7B O S 25° · •• 15° 10°

Figure 1. Bathymetry of the Weddell Sea (from Johnson et al. 1981) 2

The seafloor topography of the northern Antaretie Peninsula region is extremely rugged and refleets the eombined influenee of tee­ tonic features, voleanism, and glaeial erosion. Figure2 is arecent bathymetrie map of the Bransfield Basin and serves to illustrate this ruggedtopography. The slope and rise bordering Drake Passage are quite steep and narrow. The adjaeent shelf is eharaeterized by a 200m terraee and SOOm terrace; both of these are cut by- ehannels extending from both the peninsula and the South Shetland lslands.

The origin of these terraces and ehannels is problematie. The dom­ inant feature of the region is Bransfield Strait, a deep, linear depression whieh is aetually subdivided, probably by major trans form faults, into several diserete basins with a general no:rtheast­ southwest orientation.

East of the Antaretie Peninsula, major physiographie features inelude the South Seotia Ridge, Powell Basin, South Orkney Plateau,

Enduranee Ridge, and Orkney Deep. All of these features are key segments in the eomplex tectonic history of the region.

Glaeial Regime

The Weddell Sea is the ultimate repository for approximately

20% of the glaeial iee drained from the Antaretie eontinent, in­ eluding both the East and West Antaretie iee sheet (Fig. 3). The eastern shelf reeeives drainage from the East Antaretie lee Sheet

(Dronning Maud Land and Coats Land). Most of this iee drains through the Brunt lee Shelf and Riiser Larsen lee Shelf_

The Filehner lee Shelf is the eonfluenee of several large

East Antaretie ice streams (lee Streams A, Band C of Drewry, 1983; ------...

" . ."

t.--, 0) GRAH~M LAN D ? &,580 L5 ( 54° W " Figure 2. Bathymetry of the Bransfield Strait( from Davey,1972) 3

Fig. 3). The Ronne Ice She1f receives glacia1 drainage from

West Antarctica (Fig. 3). In the western Wedde1l Sea, the prom­

inent glacial feature is the Larsen Ice Shelf. It is a relatively

thin ice shelf, compared to the other ice shelves of the Weddell

Sea, and is the glacia1 terminus of outlet glaciers flowing down

off the mountains o 'f the ' eastern side of the Antarctic Peninsula.

Sea ice conditions are i1lustrated in Fig. 4. The western

Weddell Sea is near1y always covered by perennia1 ice,whereas a

coastal lead typically exists along the eastern coast during the

late summer. The Bransfield Strait is free of ice throughout the

austral summer,as is the northwestern Weddeil Sea in tpe area of

the Powe1l Basin and South Orkney Plateau.

Iceberg drift tracks for the Weddell Sea follow a general

. clockwise pattern. ' Large tabular bergs, some tens of square kilometers

in area, occur throughout the region, but tend to be most concen­

trated over the eastern shelf and in the northwestern sector of

the basin. These icebergs have drafts up to 250m, which is still

less than the average depth of the shel~ so they tend to drift

freely with surface currents. We have measured iceberg drift rates

of 1-1/2 knots/hour in the vicinity of James Ross Island. Iceberg

densities are rather patchy in the Bransfield Strait and depend

largely on weather conditions.

Sea State and Meterological Conditions

Sea conditions in the Weddell Sea are subject to rapid change,

at least in ice-free regions, resulting, mainly from the passage ___ ,

O/W

•

.

,':: :.:·c30EC• TH'RDWEEK

O/W O/W .: MARCH FIRST WEEK

O/W

., .... J '.' JAN. THIRD WEEK t i ~'~':~"" " ' " ..... ~. '.' I ~ ". 'l. ~ ; : By:JOHN B. ANOERSON \ \" \ .,\ \ \

Figure 4. Sea ice conditions for the Weddell Sea(based on average conditions for 1973 through 1978)

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of large,low pressure systems from west to east across the peninsula and onto the central basin. During Deep Freeze 82 we encountered 7m seas for several days in the Bransfield Strait. The seas shiftfrom west to east as low pressure centers pass through the area. Similar sea condi tions occur in the northeastern Weddell Sea as "lows ii pass into this area. Seas tend to remain relatively ca Im in the vicinity of the Powell Basin. The Drake Passage and adjacent Antarctic mar­ gin are known for their rough seas.

The weather can be relatively pleasant during the austral sum­ mer with temperatures ocqasionally rising clbove the freezing point.

However, cold temperatures (sub-zero), strong winds,and blowing snow and ice can persist for days when slow moving "lows" pass through the area.

Physical Oceanography

Figure 5 shows thedistribution of the major water masses in the Weddell Sea and their directions of movement (Klepikov, 1960;

Hollister and EIder, 1969 and Seabrooke et al., 1971). Cold, Fresh

0 0 Shelf Water , -1.89 C to -1.5 C, less than 34.51 O/oo,and d T <27.77) occupies the eastern continental shelf of the Weddell Sea and is be­ lieved to flow in a southwestward1y direction as a pronounced coastal current (Deacon, 1937) at velocities rangj:ng ;" from 10 to 30cm/sec

(Klepikov, 1963). At approximate1y 750 S this coastal current turns seaward and flows westwardly along the outer flank of the continental shelf as a v-shaped river of fresh surface water (GilI, 1973). The freshness of this water mass is largely due ·to seasonal melting of 5 pack ice so that its distribution is, for the most part, restricted to areas where seasonal melting overshadows the effects of freezing.

Smaller amounts of freshwater might be contributed by melting ice shelves such as the Brunt lee Shelf (Thomas and Coslett,1970).

Warm Deep Water ( -0.360 C tö +2.00 C, 34.45-34.69 °/00 and d~ 27.80) enters the Weddell Sea at approximately 15-200 E and flows south along the slope (Fig .. 5)at velocities in excess of 30cm/sec

(Klepikov, 1960). This oxygen deficient (4.5-6.4ml/l) Warm Deep

Water consists of a mixture of Antarctic Circumpolar Water and smaller quantities of North Atlantic Deep Water (Deacon, 1937), and is believed to be the source from whichother Weddell Sea water masses are derived (GilI, 1973). At approximately 74 0 S by 280 W,

Warm Deep Water flows westwardly (Fig. 5) along the outer edge o.f the southwestern continental slope. A sharp thermocline separates dense Warm Deep Water (dT<27.80) from overlying Fresh Shelf Water

(~T<27.77) north of 740 S.

lntense surface freezing (GilI, 1973) and possible sub-basal freezing of the Ronne lee Shelf (Seabrooke et al., 1971) results in high salinities (34.51-34.84 °/(0) and low temeratures (-150 C to

-2.200 C) of waters occupying the southwestern continental shelf area.

Most Saline Shelf Water flows in a northwestwardly direction

(Fig. 5) out across the continental she1f and onto the slope (HolIister and EIder, 1969). West of approximate1y 400 W Saline Shelf Water is sufficient1y dense (dT<27.81) to displace and mix with Warm Deep Water to form Antarctic Bottom Water (T=9.440 C,S-34.66 °/00 ; Sverdrup et al., 1942.) 4QOW

...... Saline Shelf Water (SSW) ~ Fresh Shelf Water (FSW)

(WDW) ., -

Figure 5. Distribution of major water masses in the Weddell Sea (bottom water circulation from. Anderson~1975, surface circulation from Johnson et al.1981). Large open arrows show surface circulation. Dashed line shows position of the Antarctic Divergence. 6

Newly fermed AABW flows dewn the eentinental rise in a nertheast­ ward direetien aeress the abyssal fleer. This deep water eireulatien medel is best illustrated using a near bettem temperature map fer the Weddell Sea (Fig. 6) . AABW flews eut ef the Weddell Sea at an average veleeity ef 3em/sec.,and prebably flews slightly faster where eenstrained by physiegraphie features (Carmaek and Fester,

1975) •

Cireulatien in the seassurreunding the Antarctie Peninsula is net weIl knewn. Hydro. easts taken in the Bransfield Strait and in Pewell Basin indicate relatively thereugh mixing within these basins as based en temperature, salinity,and exygen data.

Teetenie Setting

The Weddell Sea regien eeeupies a strategie leeatien with regard te Gendwanaland reeenstruetiens, arid the Antaretic Peninsula is the "preblem ehild" to be reekened with in sueh fits. Du Teit

(1937) was the first te prepese a reasenable Gendwanaland reeen­ struetien, whieh relied selely en merphelegie fits and geelegieal trends. His medel has eentinued te preve itself a werthy ene, even sinee marine geephysieal data have been eelleeted in the regien. Smith and Hallam (1970) prepesed the first eemputer-aided reeenstruetien ef Afriea-Antaretiea threugh use ef the 500 fathem

( lkm) isebath (Fig. 7). Dietz and Sprell (1970) used the 1000 fathem (2km) isebath in their reeenstruetien (Fig. 8). Their study yielded generally similar results te Smith and Hallam's medel. Dif­ ferenees between thetwe medels eeeur mainly in the area ef the Figure 6. Near-bottom temperature distribution and deep water circulation (modified from Anderson,1972) / / / / \--- t:I .._ ._ .. . . L. -" \ ! i,

, I / '...-- .- - ,/ "- .I I

\

Figure 7 The Smith and Hallam (1970) reconstruction of Gondwanaland. Note the relationship of Africa to Antarctica. 20" 2~" _l- I I -j-

A F R I C A 20"- -1- -1- + +

. -~.- ---.. "-L - - J ~ WEDDfll SEA - - - "- S~.IF je • • .1;. I I ~._ " - ANTARCTICA I - -L I ~" ~'-'-­I

Figure 8 The Di~tz and Sproll (1~7U) reconstruction of Africa -Antarctica. Relative to the Srnith ana Hallam re­ construction, Africa has been rotated to the west relative to East Antarctica. 7

Weddell Seai the Smith and Hallam model does not completely close the Weddell Sea, while the Dietz and Sproll model does. The Norton and Sclater (1979) reconstruction (Fig. ~ 9) differs only slightly from the Smith and Hallam and Dietz and Sproll fit in the area of the Weddell Sea. The continuity of fold belts, as weIl as volcanic

(Karroo and Ferrar Groups) and Precambrian metamorphic terrains is accounted for in all three models. Furthermore, in all three models the Antarctic Peninsula is depicted much as it appears today, i.e., extending northward from West Antarctica towards south America and forming the western boundary of the Weddell Sea. This paleoposi­ tion is supported by marine geophysical (Norton and Sclater, 1979) and paleomagnetic evidence. In the above reconstructions, however, the

Antarctic Peninsula is required to overlap considerable portions of the Falkland Plateau and/or South Africa (depending on the recon­ structive ~odel). Dietz and Sproll (1970) accounted for this over­ lap by dismissing the Antarctic Peninsula as a "Mesozoic accretionary belt", while Smith and Hallam attributed the observable overlap to continental distortion resulting from the breakup of Gondwanaland.

More recent work in this region has shown that the solution to the

Antarctic Peninsula problem is not as simple as that proposed by

Dietz and Sproll or Smith and Hallam.

It has been weIl established that Precambrian basement under­ lies much of southern Africa (Haughton, 1969). In addition, migmatitic gneiss of upper Precambrian or lower Paleozoic age was recovered from Site 330 of leg 36 of the Deep Sea Drilling Project on the eastern Falkland Plateau, which supports the continental nature of thLssubmerged crustal block (Barker et al., 1976). Further supporting JURASSIC

Figure 9 The Norton and Sc1ater (1979) reconstruction of Gon­ dwana1and. This model differs slightly from the Smith and Hallam reconstruction and is preferred by this report. 8

evidence for the continental nature of the Falkland Plateau comes

from the upper Precambrian radiometrie ages reported for the Cape

Merideth gneisses in the Falkland Islands by Rex and Tanner (1982).

Thus, the southern portion of the South American-African segments

of Gondwanaland is now known to be underlain by upper Precambrian

to lower Paleozoic continental basement.

Recent work in the Antarctie Peninsula has shown that the

pre-Middle or Late Jurassie basement of this region, known as the

Trinity Peninsula Series, comprises an accretionary foreare terrain

(DeWit, 1977; Smellie, 1981; Dalziel and Elliot~ 1982). Although

there remains some controversy surrounding the exaet age of the

Trinity Peninsula Series (cf, Tanneret al., 1982), it is generally

feIt to be late Paleozoic to early Mesozoic in age. Isotopic

. (Pankhurst, 1982) and mineralogie (Hamer and Moyes, 1982) evidence

suggests the presenee of older Paleozoic or possibly Precambrian

basement beneath at least part of the Antarctic Peninsula.

Because the exposed basement rocks of the Antarctie Peninsula

(i.e., the Trinity Peninsula Series) predate the breakup of

Gondwanaland, it follows that the Antarctic Peninsula must have

existed in some form prior to the breakup of the supercontinent.

Overlap of the Antarctic Peninsula with the Falkland Plateau and/or

South Africa is questionable not only because of the tectonic prob­

lems associated with overlapping continental (or quasicontinental,

as may be the case of the Antarctic Peninsula) segments floored by

Precambrian basement, but also beeause of · the differences in the

geologie development of these regions. Because of the obvious problems 9 associated with Antarctic Peninsula overlap, numerous alternative models have been proposed in attempts to account for the Antarcti c

Peninsula in a Gondwanaland context.

Heirtzler (1971: see Fig. 10) and Dalziel (1982a) suggested that the Antarctic Peninsula, due to its similarity in shape to the East Antarctic Coast and Caird Coast of the eastern Weddell Sea, once res ted against East Antarctica. Subsequent counterclockwise rotation of the peninsula due to spreading along a failed rift, presently underlying the Weddell Sea, was invoked in Heirtzler's model. Such a reconstruction is consistent with the currently accepted counterclockwise rotation of the Ellsworth Mountains

(Dalziel, 1982a), yet suffers from some serious problems. One major problem is that ·this model requires a tremendous offset .of the east-dipping subduction complex associated with the are terrains of the Andes and Antarctic Peninsula. Another problem is that if the Antarctic Peninsula had rested against East Antarctica, it would have extended into Mozambique if the Dietz and Sproll (1970) or

Smith and Hallam (1970) reconstructions are correct, and would have overlapped the continental shelf of Africa if the Norton and Sclater

(1979) model is correct. There is little evidence to support a rift origin for the Weddell Sea, while marine magnetic anomalies in the northern Weddell Sea argue against this reconstruction (LaBrecque and Barker, 1981). Another alternative reconstruction was suggested by Tarling

(1972) in which the eastern margin of the Antarctic Peninsula was juxtaposed along the western margin of South America. Although TRIASSIC 200 MY CRETACEOUS 100 MY PRESENT '.

90· E

Figure 10 The Heirtzler (1971) reconstruction. More recent data on sea floor spreading patterns discredit this model. Note the position of the Antarctic Peninsula relative to East Antarctica. 10 this model has been reeently advoeated by Harrison et a1. (1979,

1980), Powell et al. (1980), and Miller (1981, 1982, 1983), it has 'drawn ertiieism from Dalziel (1980) and Godoy a~d Po.dozio (1980). The Tarling and Harrison et al. models, as shown in

F~gures 11, 12, Lrequire the existenee of an extensive double-are system along western South Ameriea prior to Gondwanaland breakup.

During and after breakup, these models require the development of an extensive left-latera1 shear zone perpendieular to the assoeiated treneh axis in order to move the Antaretie Peninsula south to its present loeation. These. models also require large displaeements of West Gondwanaland, relative to the more aeeepted Smith and Hallam

(1970) and Norton and Sclater (1979) reeonstruetions, in order to aeeommodate the Antaretie Peninsula along southwestern South Ameriea.

Other reeonstruetions of the paleoposition of the Antaretie

Peninsula have been proposed by E11iot (1972), Suarez (1976), and

Barker and Griffiths (1972, 1977). These reeonstruetions are based on a linear to sublinear (or euspate) relationship of the Antaretie

Peninsula to the tip of South Ameriea in order to provide eontinuity of the are terrains of these regions. They require modifieation by later events in the Seotia Are Region in order to attain the present eonfiguration of the Antaretie Peninsula relative to the southern

Andes.

Barker et al. (1976), DeWit (1977), and Dalzie1 (1982b) have suggested a fourth alternative reeonstruetion of the Antaretie

Peninsula. Their models suggest that prior to breakup of Gond­ wanaland the Antaretie Peninsula was rotated approximately 900 eountereloekwise from its present position and was eonneeted at ?

Figure 11. Tarling's (1980 ) Gondwanaland reconstruction Figure 12 The Harrison et ale (1979) model of the paleo­ deve10pment of the Antaretie Peninsula. This model, similar to Tar1ing ' s (1972), requires an extensive double-are terrain whieh is later dis­ rupted by large-sea1e 1eft-1ateral faulting. 11 l . its tip to the southern Andes. Da1zie1's (1982b) version of this

model is shown in Fig. 13.. This reconstruction is appea1ing as

it ac counts for known age progressions in forearc terrains of this

region and a110ws for continuity of the subduction re1ated arc

terrains of the southern Andes and Antarctic Peninsula.

The pa1eoconfiguration of the island of Madagascar, 1ike that

of the Antarctic Peninsula, is intimately related to the larger

problem of re1ating East and West Gondwana1and. Most accepted

Gondwana1and reconstructions p1ace the western margin of Madagas­

car adjacent to the coasts of present-day Kenya and Tanzania

(e.g., Smith and Hallam, 1970; Norton and Sclater, 1979). In

these reconstructions, the eastern margin of Madagascar is juxta­

posed with the southwest margin of Peninsular India. Alternative

reconstructions of the Antarctic Peninsula, such as those of Powell

et ale (1980) and Mi11er (1981, 1982b, 1983), which position the

Antarctic Peninsula along the western margin of South America, a110w

a simi1ar Kenya-Tanzania-Madagascar configuration, yet require a

southward shift of India to maintain a reasonab1e geometry. Similar

Antarctic Peninsula models by Tar1ing (1972) and Harrison et ale

(1979) require a southward displacement of Magagascar to a position

adjacent to the S'Outh Africa-Mozambique margin in order to maintain

a southwestern India-Madagascar relationship (see Figs. 11, 12). A1-

though there is no consensus on the past configuration of the Antarctic

Peninsula, there is evidence from paleomagnetic da ta (Embleton and

McElhinney, 1975, 1982; McE1hinney and Embleton, 1976; McE1hinney

et a1., 1976) and from marine magnetic anoma1ies (Norton and Sc1ater,

1979) which supports the more accepted Kenya-Tanzania-Madagascar

relationship. '.--

-. ~

L __ •• • _ . _ _ ••_ ••. ....l

Figure 13. Dalziel's (1983) model of the paleoconfiguration of the Antarctic Peninsula with respect to South America. 12

In arecent paper, Tarling (1981) proposed a novel reeon­ struetion of Gondwanaland based on an alternative position of

Madagasear. By dismissing the above eited marine magnetie and paleomagnetie data for Madagasear, Tarling proposed that the island had maintained its present eonfiguration relative to

Afriea, even when it was part of Gondwanaland. His model, shown in Fig. 14, requires a 2500-3000 km northeastward displacement of West Gondwanaland relative to Antaretiea-India-Australia in order to maintain a proper Madagasear-India relationship. The large displacement results in the juxtaposition of the Falkland

Plateau and the East Antaretie Prineess Martha Coast. In this eonfiguration, a eontinuous are terrain between the Antaretie

Peninsula and the Southern Andes, similar in geometry to the present Aleutian-Kamehatka Peninsula Are, eould be reeonstrueted by rotating the Antaretie Peninsula into the Weddell Sea (cf.

Heirtzler, 1971; Dalziel, 1982a). Although the Tarling model provides an alternative to the more aeeepted Gondwanaland reeon­ struetions, it may not be eonsistent with present paleomagnetie and marine geophysieal data; it remains to be seen as to whether it will pass these tests.

Timing of Major Plate Tectonic Events

The initial breakup of Gondwanaland is believed to have oeeurred sinee Mid to Late Jurassie time (Simpson et al., 1979;

Bergh, 1977 and Rabinowitz et al., 1983), with the development

of the Wedde11 Basin oeeurring mainly during pre-Late Jurassie to

Cretaeeous time (LaBreeque and Barker, 1981; LaBreeque and Keller, 13

1982)and the Seotia Sea was probably not present prior to mid­

Oligoeene time (Barker and Dalziel, 1983). The South Orkney Plateau,

Powell Basin and Bransfield Strait are all eonsidered to be l relatively young features, indeed the Bransfield Basin may be as young I as 2 m.y. old (Weaver et al., 1982; Dalziel, 1983). The Continental Margin

\ Marine geophysieal surveys on the Weddell Sea eontinental I margin have been eonfined to the eastern half of the basin beeause of severe sea iee eonditions in the western Weddell Sea. In 1962

Behrendt published an important paper deseribing the subglaeial

topography of the Filchner lee Shelf region as based on gravity

measurements obtained from the ice. The earliest marine seismic

surveys were conducted during the austral summer of 1977 by scientists

from the Norwegian Polar Institute (NPI) (Orheim, 1977; Fossum

et al. 1982; Haugland, 1982) and during Islas Orcadas Cruise 1277

(Gordon and LaBreeque, 1977). To date, only preliminary findings

of the Norwegian multichannel survey have been published (Haugland,

1982) •

Aeromagnetic and seismic surveys of the Weddell Sea were carried out

during the Soviet Antarctic Expeditions of 1975-82 (Grikurov, 1980;

Kamenev and Ivanov, 1983). During the 1978 austral summer the Ger-

man Federal Institute of Geosciences and Natural Resources (BGR) conducted

a multichannel seismic refleetion and sonobuoy refraction survey

of the continental margin of the northeastern Weddell Sea (Hinz

and Krause, 1982 and Hinz, 1983). Also in 1978, single channel

seismic reflection and sonobuoy da ta were acquired in the same area 14

during Is1as Orcadas Cruise 1578 (LaBrecque, et a1., 1978), and I in 1981 the Japanese Techno10gy Research Center (TRC) obtained mu1tichanne1 seismic ref1ection profiles of the 10wer continenta1

l­ margin off Queen Maud Land (Okuda et al., 1983). Most recent1y, I during the austral summer of 1982/83, the German research vesse1 Polarstern was- used to acquire marine geophysical data (magnetics

and MCS survey) in the Bransfield Strait and the Antarctic Penin­

sula region.

The mu1tichanne1 seismic ref1ection records co11ected on the

10wer continenta1 margin of Queen Maud Land by Hinz and Krause

(1982) show a re1ative1y undeformed sequence of low velocity «3 km/s)

sediments resting unconformab1y on a deformed sequence of higher

velocity (4-6 km/s) deposits (Fig. 15). The older sequence is

characterized by seaward dipping reflectors and has been named the

"Explora Wedge" by Hinz and Krause (1982). They infer that this

sequence is comprised of Late Jurassie vo1canic and vo1canic1astic

sedimentary rocks deposited during the early rifting stage of basin

development. The Explora Wedge is truncated by an unconformity

(the "Weddell Sea Continental Margin Unconformity") of possib1e

Late Jurassic age (Hinz and Krause, 1982). The overlying sequence

consists of four units (WS-l through WS-3B, Fig. 15), each separated

by unconformities (Hinz and Krause, 1982).

The continental margin of the eastern Weddell Sea includes at

least two sedimentary basins, the Brunt Basin and the Weddel1

Basin. The Brunt Basin is situated between approximately 730 S and

750 S and contains between 1.5 and 2.5 km of sedimentary deposits BGR-78-19

0 ..... _ .. ____ • 0 CI) 1 1 E See floor 2 --' 2 eddell See I ... .., "'0 3 - 3 c: 4 0 4 ::-:::-- 5 (J 5 S~~ - ORA 4.3-4.8 km/sec 6 CI) ..... ----.. 6 2 3 2 6 10 20 km 3.1_3.8 . - . sec. -CI) 7 a: 8 sec.

Figure 15. ~nterpreted Seismic reflection profile across the Queen Maud Land continental slope (from Hinz and Krause,1982) 15

with seismie veloeities of less than 4.0 km/s (Haugland, 1982).

The center of the basin is oeeupied by the Brunt M9gatrough, whieh may contain as mueh as 14.5 km of sedimentary deposits (Kamenev and Ivanov, 1983). Haugland (1982) deseribes the strata in this area as a typical prograding shelf sequenee laeking signifieant tectonie features.

Roqueplo (1982) eondueted a detailed seismic stratigraphie study of the eastern Weddell Sea shelf using the 1977 Norwegian /' (NPI) reeords. Her seismie stratigraphie eolumn is shown in Fig. 16.

The lowermost seismie unit drapes a-coustic basement (draping unit) , is finely laminated, and dips seaward at 10 to 20 • Its maximum thickness is estimated to be 460m. The draping unit is overlain by a relatively thiek (~900m) prograding unit (sequenee A) with 20 to jO seaward dips and illustrating a broad, lobate pattern. This unit rests direetly on aeoustie basement in the vicinity of Crary

Trough. Sequenee A was eroded' .. to erea te a wides pread, rela tively planar unconformity (uneonformity Ul, Fig. 16) ". In the Brunt

Megatrough area, Sequenee A is uneonformably overlain by an onlap sequenee (Sequenee B, Fig. lG). The lower part of Sequenee B is lamina ted while the upper part of the sequence has very few in- ternal refleetors (Fig. 16). The two units appear to be faeies

equivale~ts, with the massive unit grading offshore into laminated deposits. Sequenees A and B were deeply eroded to ereate the

"Weddel1 Sea Glaeial Uneonformity" (uneonformity U2 , Roqueplo, 1982; Fig. 16) whieh is widespread on the shelf. It was this glacial erosional event whieh resulted in the great depth and irregular ~

NPI-lINE 3 RECEHT DEPOSITS N S W.d ...... Olec'.' Unc.n'o,,,,U, •• c:.

1 On'.p ,/ ..,.....,.,..-- S.q ... nc /". P'08' •• '''' 'h",I.1 D .... lc ...... nc. ./ -- 1------_1 OOkm •

~ ___~~~I~ " NPI-LlNE I N SE - --.:. ~~ PROORAOIN ~\~~ UNIT UNIT 11 .JHIT I •• c. :.:.:.:.:.~.\ \ _~..wA ~~~~.~I~~n... '...•..•... .,...# # ...... • ...... , ...... ~t /»))3;;;~:6 -- t!1 '\ ORAPING /,T 1 UNIT ,.ROQRADIHO 'UNIT ''\

tOOkm T------BA'SEMENT

Figure 16. Seismic stratigraphy and representative interpreted seismic reflection profiles for the eastern Weddell Sea shelf(from Roqueplo,1982) 16

topography of the modern seaf100r (Roquep10, 1982; E1verhoi and

Maisey, 1983; Anderson, in press) •

Roquep10 (1982) noted that the unconformity (U1) which separates the prograding sequence (Sequence A) from the on1ap sequence (Sequence B) is widespread on the eastern she1f, re1ative1y planar, and appears to coincide with aperiod of submarine canyon de­ ve10pment on the continenta1 slope. These features, plus the fact the unconformity is buried beneath an on1ap sequence, imp1ies that it was formed during a 10wer sea level stand. She further specu1ates that this event coincides with the wor1d-wide eustatic event at 29 m.y. (Vai1 et a1., 1977). If so, then the deposits which fi11 the Brunt Megatrough are main1y older than 01igocene, and are of non-g1acia1 origin.

Sou~ of the Brunt Megatrough, acoustic basement is exposed on the continenta1 she1f (Roquep10, 1982; E1verhoi and Maisey, 1983)

(Fig. 17). The high magnetic susceptibi1ity of basement rocks in the area indicates an igneous origin (Roquep10, 1982) . A deep de­ pression, Crary Trough, separates the portion of the she1f from the broad continenta1 she1fof the western Wedde11 Sea. Crary

Trough may possib1y mark the position of a major fault system sepa­ rating East and West Antarctica (E11iot, 1972). Behrendt (1962) did measure a :arge positive gravity anoma1y over this feature, whichindicates either a zone of crusta1 thinning or an intrusive body.

Seismic profiles across Crary Trough (Fig. 18) show acoustic

basement outcropping on the eastern she1f, and westward dipping ..oooo.ooo; ...... ~...... '" oa.,TA SE~ c,u'PCD GY TU. SEE L.M: 3oF~ ~XA~ ...... ' ...... I EEJo' ...... I ' .. : ...... " ......

GLAC\AL ~ Ol.CNt-:C

(lJNI'T S ,,11)

f" o 50 ",., .. + 35W 30 w

Figure 17. Distribution of major seismic facies in the eastern Weddell Sea (compiled from Norwegian data provided courtesy of Dr George Maisey). 0 0 , -Q) rn ...I a -w > CRARY TROUGH < a:: J- w :e ~:=-- ~ ~: > ." , < • ~ 1. 1. 2 • •• ~ - R1 - R2 0 50 100 150 - 200 250 300Km

1.7 - 2.0 5 , b Km ~ 10 ~O

15 . Figure 18. Interpreted seismic profiles across Crary Trough a. Norwegian single channel profile (from Roqueplo,1982) b. Russian MCS profile (from Ivanov,1983) 17 reflectors in the western flank of the trough wh±ch have been exposed by erosion. The results from two sonobuoys deployed in the trough show a sediment thickness of about 2km near the axis of the trough and about 4.Skm in the western flank of the trough

(Haugland, 1982). Most of these sediments have seismic velocities between 2.6 and 4.0 km/s (Haugland, 1982). An MCS (12-channe1) profile co11ected along the front of the Ronne lce She1f by Russian sceintists in 1980 (Fig. 18) shows that sedimentary deposits of the Southern Weddell Sea shelf thicken to approximate1y 10 km, and preliminary results from a British Antarctic Survey (BAS) aero­ magnetic study over the Ronne lce She1f are consistent with sediment thicknesses of 14 to lSkm beneath the ice she1f (G. Renner, pers. cornrn. to Behrendt, 1983).

Several grab samples and piston ~ores collected from the western flank of Crary Trough and from the southern Weddell Sea she1f near Berkner lsland, contain unlithified, quartzose, eo1ian dune sands (Rex et al., 1970; Anderson, 1972). They apparently outcrop on the western flank of Crary Trough (Fig. 18) and are considered to have an East Antarctic source (Anderson, in press). This is based on an absence of volcanic material in these sands. Also, the westward dipping reflectors of the Crary Trough region indicate that the continental shelf located east of Berkner lsland was ac­ creted from East Antarctica. Dramatic difference in the thickness of sediment deposits on the continental she1f of the eastern Weddell

Sea implies that major structural elements intersect the she1f and

are responsible for these differences (Anderson, in press) . 18

As in the Ross Sea, f1uvia1 de1taic sedimentation was oc­ curring on the Wedde11 Sea continenta1 she1f during what is be1ieved to have been the ear1y glacia1 history of the region, hence more temperate glacia1 conditions are imp1ied (Anderson, in press) .

Major deltas were situated in the area of the Brunt Megatrough and west of Crary Trough. De1taic and glacial marine sedimentation ended with a major advance of both the East and West Antarctic ice sheets onto the eastern continenta1 she1f (Anderson et a1., 1980;

E1verhoi, 1982; Anderson et a1., 1983). Theshe1f was deep1y eroded during this event creating a modern seaf100r unconformity ( lt Wedde11

Sea G1acia1 Unconformitylt) (Roquep10,1982; E1verhoi and Maisey, 1983) .

To date, no geophysica1 resu1ts have been pub1ished on the western Wedde11 Sea. The continenta1 she1f there is re1ative1y broad

(averaging 300 km in width) and is covered by sea ice throughout the year, hence access by ship is extreme1y 1imited. The she1f is situated within an extensive back-are terrain of the Pa1mer Magmatic

Are, and has probab1y accumulated a re1ative1y thick sedimentary sequence,derived from this are, since Jurassie time (E11iot, 1983).

Thick post-ear1y Jurassie vo1canic1asic deposits outcrop extensive1y a10ng the entire1ength of the western Wedde11 Sea coast (Latady

Formation, Laudon et a1., 1983) and undoubted1y extend seaward be­ neath the continenta1 she1f of the western Wedde11 Sea.

Antarctic Peninsu1a-Be11ingshausen Sea Region

The tectonicevolution of the Antarctica Peninsula - Scotia

Are has been recent1y reviewed in a number of papers (Barke~ et a1., 1982

Da1zie1, 1981, 19a2, 1983; Da1zie1 and E11iot, 1982; DeWit~ 1977;

Norton, 1982; Thomson et a1., 1983). The region's deve10pment has 19 been dominated by subduction, which dates back to the Early

Mesozoic, and possibly to Late Pa1eozoic (Da1zie1, 1983). During its early development, the Bellingshausen continental margin was an active margin, and fore-are and back-are basins have flanked the penins~la since Late Jurassie time (Elliot, 1983). Oblique subduction of the Aluk Ridge crest, from west to east, occurred during Late Cretaceous through Early Miocene time (Herron and

Tucholke, 1976; WeisseI et al., 1977),so the active margin was gradually transformed to a passive margin as the ridge-crest was consumedand the 10cus of magrnatism was shifted to the north and east. Bransfield Strait is a relatively recent (less than 2.0 m.y.) spreading center (Weaver et al., 1982; Dalziel, 1983).

Marine geophysical surveys of the reg-ion were first carried out in the Bransfield Strait .and included gravity and magnetic surveys (Griffiths et al., 1964; Davey, 1972') and seismic refraction measurements (Cox, 1964; Ashcroft, 1972; Watters, 1972). Single channel sparker profiles were obtained from the southern end of the Bransfield Strait during the USCGC Glacier Deep Freeze 81 Ex­ pedition (Anderson and Myers, 1981). The Bellingshausen margin was surveyed during the U.S. Eltanin Cruise 43, R/V Vema Cruise

1806, and R/V Conrad Cruise 1503, but only single channel data were acquired during these cruises and these surveys were mainly restricted to the deeper part of the margin (Tucholke and Houtz,

1976). During the 1980-81 field season, the Japanese Research

Center obtained multichannel seismic data in the Bellingshausen

Sea, including one line that extended onto the continental shelf near Adelaide Island. 20

The results of the early BAS surveys showed the Bransfield

Basin to contain between 2.5 and 3.0 kilometers of sediment resting on oceanic crust (Cox, 1964; Davey, 1972; Ashcroft, 1972), while

the shelf north of the South Shetland Islands has upwards of 5.5

to 6.0 kilometers of sediments underlying it (Ashcroft,1972, Davey,'

1972), (Fig. 19). Without multichannel seismic data, little can

be said about the seismic stratigraphy in these areas. Single

channel seismic records from the Bransfield Strait (Deep Freeze 81

data) show acoustic basement exposures at relatively shallow water

depths (less than approxiately 600 meters) a·t the western end of

the Bransfield Basin. The relatively thick sediment fill of the

basin implies rapid sedimentation rates, given the young age (-2 m.y.)

of this feature.

Birkenmajer (1983) recognizes three major unconformities within the Plio-Pleistocene section of King George Island which

he attributes to episodic tectonic activity. The oldest of these

unconformities occurs in Early Pliocene time and perhaps reflects ' the

initial rifting of the basin. The second occurs in the Middle Pliocene

section and is associated with the formation of acidic stratocone

volcanics. The upper-most unconformity probably spans the lower

Pleistocene and is of glacial origin.

The multichannel line acquired during the 1980/81 Japanese

survey (Fig. 20) shows a basement high situated near the shelf edge. This. feature is interpreted as a paleo-island arc, and unformably

resting on it is a thick, seaward dipping accretionary sequence,

which represents passive margin development in the area (Kimura, 1982).

In this area, the Aluk Ridge was subducted beneath the peninsula SECTION 2 NW SE C D I ~OO 250 200 150 100 50 o I I I ADMIRALIT~ BA Y bRANS~'ELD TRINITY: KING GEORGE I. STRAIT P.ENINSULA SECTION 1 SECTION 3 I o. .' -'l 3 3 ' I",I'I~::-I :, SEA LEVEL o 1.8-4. O . ::~"'~' 5' 5't -.. 4.0 "V,.;.,";~I'.:: 'I,' ---": .... ~-"\ ..:, ...... " ... , (",-"--', 'I'" ~,:; " \'-'"' , .,.:..' .....-T,,; --,-J';'! ..... ' -... ,.'\ 1,_,-' - '_l. j _ ..... ', ',1';\,"""\'.. - • ~ f1·'::'-;\,t~"- ....\!J 5 5 ~I 5. ~"'s:a:-<~ ,'; '; ;-~,,~, 6.0 .. , ,'',.~ f1 (~,.~:.:.:.:.: ... ~~!,- , ...... ,.,; ':'~' ~'{:~~~, "!..\(I: ~~~, . 10 :t':-::;~f:::~~~:?:~:::~:f:!;7::f.:ti:~:~T~:~1 :.J.~.!;:.":~:::~~f6".·6··~}::~~.!\~ ~I:' -:."'~" 6. 2 ;-,S'~~~~: I ~~1 ~:lf ~ ~ ~ ~~; ~~ ~ ~ ~ ~ ~~ ~~ ~ ~ ~ ~~ ~ ~ ~ ~ ~ ~~ ~~ ~~ ~~ ~~ ~ ~~; ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~; ~H ~ ~; ~~ ~~ ~ ~ ~; ~~~;~;~;~; ~ ~ 1~1 ~;;; ~;;;;; ~;;;~;;;;;;~; i; ii i= i~.~ :J~Z,S.'-~: ~~~~~2 ~:-: :~~1 10 km km .. :.::: :::~::?::~~~~~~~;;;~~;~;~;~;~;~;~~~~~~~~:.:~ .'7~';;~~~~;~~~~~~~;~~;::::' .::::::::;:::~::;:;:~:;;;;;;~;~; ;~jl;~~r!:-'--;~i ;,'...,'" I;''; ;~::;'~-,~ ~-. 15 ...... 77 .. " - ,\, 15 '-' !!:';;;':':':':':':'::::::':':':':;:':':':':':':':':". l' - ...... ,. '"' ,~' .-, I, !!::::::::::::.:.:.:.:::::::::::::::::::::.-.~.. :.:.:.:.:.:.: ...... :.:.:.... - , 20 20 ···1··························. ~;:::::~~:::::: .. 25 8.0 25

Figure 19. Interpreted seismic refraction profile across Bransfield Strait (from Ashcroft, 1972). . SP Une 9 SP Llne 9 4900 6700 SP 6600 SP 6000 SP 7000 .-' m I Contlnental Shelf 10 sec' j ------. ContlnentaJ Shelf 10 km e" . ~q 1 A ~ack-a;'c 'ö --- .. _------... -- Basln B 2 I __ ,.,. .. ------~---- - Sediments P aleo-lsland-arc 3 " B rench lower Siope .: 6 ~entary Complex : ? c BASEMENT 6 !OCEANIC BASEMENT I Paleo-trench muhlple

i Figure 20. Interpreted seismie refleetion profile aeross the Bellingshausen eontinental margin (from .Kimura,1982) t\ , ...... x 18 Z. 16 x'

6

I .:=

Figure _21 Seismic refraction profiles across the South Orkney Plateau (from Harrington et al., 1972). ~l.$"L .-.;...:;;:...... ~; .; -- -'!. ...~.~~ . .. "" ~ ~ __~-~,. - -•._ .... _ ". ..'li! -,.,._. .- , ', - • ~- " ... ~ . !, .•.• ._ .. .. -.. . '" ~_,i~,": . .. . -----

~~ - ' .. f. . ~ . _., .. t t," ...... ~tIr ~ ,~ . ..,. ..-.. t,·· ,- • • . , ..: :-. . ~ ~f' . .~. 110" • •'1 ... '. " . . ~ ,,' » ...4f ... ~~~ .... .',r,' ...... ) ",. .,: A ~ . ..-": .. ,I­ ~ ...... -- ." ,.. .;:" :-e-~-e~' · - 1 1 • • " ; .. - -., ; .. •• : f ' .~.· :.:~rr ~-=-ii;::;'-~~ .. '- ' .. ',~ : . ".

Figure 22 Single channel profile taken across the South Orkney Plateau (provided courtesy of Dr. Peter Barrett) . . See Figure 5. 28 for profile loeation. 22

elay of late Eoeene - early Oligoeene age (Ciesielski and Jones, 1979) .

Beeause this deposit eontains sedimentary elasts and has probably moved down slope from outerops situated above this site,

it is not possible to infer the approximate level of these deposits within the plateau.

CLIMATIC AND GLACIAL HISTORY OF THE REGION

Antaretie Peninsula Region

Cretaeious and Lower Tertiary sedimentary deposits -: erop out all along the Antaretie Peninsula and, for the most part, refleet marine and terrestrial sedimentation, primarily in deltaie environ­ ments of magmatie are terrains (Elliot, 1983). The best and most

eomplete exposures oeeur on Seymour Island (Fig. 23). Here the upper Cretaeeous Marambio Group, Paleoeene Cross Valley Formation,

and the Upper Eoeene (to Lower Oligoeene?) La Meseta Formation

eomprise the most eomplete well-exposed seetion of Upper

Cretaeeous to Lower Tertiary rocks known in the Southern Hemisphere

(Zinsmeister, 1982). The sequenee was deposited primarily in delta

plain-to-delta front environments and ineludes a rieh plant and

animal fossil assemblage.

The most eomplete Tertinry sequenee in the region oeeurs on

King George Island (Fig. 2:3;). Reeent field investigations by

Polish seientists (Birkenmajer, 1981a, bi 1982a, bi 1983iand

Birkenmajer et al., 1983) has provided a mueh improved stratigraphie

sequenee for this area (Fig. 24). Aeeording to their work, plant

fossil bearing deposits eontainiQg seattered drops tones N \

70·

>t-rr I Volcanic rocks ~Ui" "''' / )[/ Volcaniclastic rocks

o 300 L
----~~k-m--~----~I

75· 60·W

Figure 23. Geographie map of the Antaretie Peninsula(from Thomson et ale 1983) STRATIGRAPHY MAIN FV. ENTS

>- 0::: <{ Z 0::: ll.J I . I­ CAPE <{ Raised marine iSYREZOL ::::> terraces (125-255ml I GROUP !INTRUSIONS) eS ____ ? ,"-_1_-1- w L LEGRU BAY GROUP z c. 300m· w u " o CHOPIN RIOGE GROUP ll.J -J 300m + Z a.. E _____ ? ___ __=_ __ 11. _ .. _, ll.J (!) ADMIRALTY BAV GROUP o (INTRUSIONS) ll.J Z -~- -~- -/J~ . w - (i\- ...... Z ' ll.J W -~- Z U BARANOWSKI GLACIER GROUP ll.J °o 11'Om -:-.~- ".lU (!) . ....J PARADISE . COVE GP 170 - 280m -1;'- o I----.:O=----IIC:::::::::::::::::::: ======ll.J I I == .A OWW DUFAYEL ISLANO GROUP ...... wuZ 107 - 150m +

<{ I ,W a.. -Joz <{ W w · a.. u

marine !.\ land '$ '" plant ...... lahar -type A A I:J. marin. ',J. $ subaerial . fauna f05Silli agglom.rat. ' tillit. tilli,./mora;ne

Figure 29. Stratigraphy of King George Island (fro~ Birkenmajer, 1982) 23 may be as old as Eocene, and certainly Oligocene age (Dufayel Island

Group, Paradise Cove Group, ane Baranowski Glacier Group) and indicate a temperate climate with local ice caps and/or valley glaciers situated in the Peninsula region by this time. Miocene sedimentary deposits of the Point Hennequin Group contain abundant remains of

Nothofagus, horsetails and ferns.

During the Pliocene,two glacial episodes occurred in the area.

The older Polonez Glaciation (4.2 m.y.) was perhaps the most ex­ tensive late eenozoic glaciation in Antarctica, when an ice sheet is believed to have spread from ·the Weddell Sea across the peninsula (Fig. 25; Birkenmajer, 1982a, b). This glacial event is perhaps correlative with the Queen Maud Glaciation of the Trans­ antarctic Mountains (Birkenmajer, I982a, b). It was followed by

~he Wesele Interglacial during which time only temperate glaciers existed in the peninsula region. The meltwaters produced by these temperate glaciers eroded deep channels on the islands "and probably carved the stream-like valleys that characterise the 200m platform of the

Bransfield Basin (Fig. 2).

Birkenmajor (1982a,b) concludes that King George Island was

raised approximately 200m during t~e WeseIe Interglacial as a result

of isostatic and tectonic forces. It is also important to note

that th€' submerged valleys of the 200m platform may" connect with

submarine canyons of the . Bellingshausen margin; the heads of these

canyonsare presently centered near the 200 meter isobathe During

Pliocene time the submarine fans fed by these canyons experienced EASTERN ANTARCTICA

+

WESTERN ", A NT A R C T I CA (). >< ~o U'

probabi. maximum .xt.nsion of ic.- cap

Figure 25. Glacial setting during the Polonez Glaciation (from Bir.kenmajer, 1982) 24

renewed turbidite sedimentation. We have examined turbidite sands

from DSDP-35 sites in detail and found them to be of glacia1 ori­

gin, probab1y glacia1 f1uvia1. We exp1ain this episode of fan re­

activation as resu1ting from a 200 m eustatic event (Anderson et a1,

submitted paper). Miocene turbidite sands from these same sites

are interpreted as being primari1y of non-g1acia1 origin.

In Late P1iocene time, King George Is1and was again covered by

an ice cap (Legru G1aciation of Birkenmajor, 1982 a,b). By this time the

Bransfie1d Strait had evo1ved (Da1zie1, 1983), so separate ice caps

covered the peninsula and the South Shet1and Is1ands (Birkenmajor,

1982 a, b, Fig. 26).

The Quaternary glacia1 his tory of the South Shet1and Is1ands has been the focus of extensive research conducted by British and

American geo10gists (Everett, 1971; John, 1972; Sugden and John, 1973;

Sugden and C1apperton, 1977; Cur1, 1980). Their resu1ts are sum- . marized in figure 27.

The Ear1y P1eistocene re cord is missing in the South Shetland

Is1ands, so our know1edge of this important time interval is very

poor. During the Late P1eistocene, two major glacia1 episodes

(IIIinoian nad Wisconsin Glaciations) and one major interglacia1

episode (Sangamon Interg1acia1) are recorded on the is1ands. During

the older glacia1 episode an ice cap approximate1y 250 X 65 km in

extent covered the islands and adjacent marine pIatform(Fig. 28,

Sugden and John, 1973). In the 1ater glacial episode separate ice

caps covered the is1ands of the region; (Everett, 1971; Sugden and ' South Orkney Islands "--:"'\( P r ~J

EAST ERN A NTARCTICA

• +

WESTERN A NTARCTI CA >< ~o \$I

mair1' 1000 '.' iee-slreams ", -~ ,-.---~ '-----, '--.... , -" probable maximum 1 I "e)(terision 0( ' iee -cop ~

'probable ~ ~~Iv . \ drift - paths + '--_/",",- /, ~ of ie.b.rgs 1800 , ...... ,

Figure 26. Glacial setting during the ~egru Glaciation (from E irkenmajer,1982) I ,------r------r------.--.------,.--.- -- .---r------, Period Age j SlIr,r,cstcd Evcnts Climate Sea level and ~ndicated from the I Epoch Present

I To Gradual thinning of ice caps Warmer Lowering Present with Fluctuat­ 265 yrs Minor re-advance ~265 yrs BP ions BP Deposition of 2.5-3 m beach. Cooler ...... Retreat of ice Warmer 500 yrs. Local re-advance 500 yrs. BP I .. f 6 ,,~ b h Cooler Halt(?) BP Depos~t~on 0 m eac. I I I, ...... r...... ;~ ...... 7000- Formation of ~~.5-20.5 m raised Warming Standstill ~ I < 9000 beach. or J ~ yrs. BP trans­ w ! H gression. ! < i g De-glaciation, ice withdrawl Warmer (?) ~45-55 m , to about present position I, ...... " ." .... "." .. " .. "."." ... .. " ...... "".""". " .... "." .... . i I Wisconsin Local glaciation, expansion of Warmer Lowering ~ : island ice caps ! - Cl) Sangamon Non-glacial interval beaches Cooler up to c I Cl) (? ) formed up to 275 m Warmer 275 m u I o I ~ Deglaciation, rapid melting, tJl 'r1 meltwater channels. Warmer Higher I Cl) T""""I moraine Cooler ±lOO m : o 'r1 surfaces and platforms 300 m .-l I p.. abJve 55 m Fluctuat- ing. o I ~ I Vegetative cover < :2 I I H I I H Falling and volcanic activity. Temperate Nu,nerous I ~ ~I "'-l J or fluctuat­ I H C; I i warmer ions. Alluean Orogeny (7) I u 1

l _. __-L-_~ __ -'I'-- ______'_ __. ______. ______.. ______. ___ .-'-______

Figure 27. Climatic events in the Antarctic Peninsula(from Curl,1980) r \ ,.. ,.. "

----+0 le ( 511111( ,At.U . -.- -- [KY[NT "NO a(HAVIOUA . OF tCE "'01 IlHO ....

~, \ / ~ I ? '? 2? Jf'

Figure 28 A reconstruction of the ice cap of the maximum glacial phase in the South Shetland Is1ands, based on erosional 1andforms. The seaward limits of the ice cap are assumed to have been determined by the 100 fathom (185 m) 1ine. (Reproduced by courtesy of the British Antarctic Survey) (from Sugden and C1apperton, 1980). 25

John, 1973; Curl, 1980).

During Recent time there ·have been two minor readvances of

island ice caps in the region. One occurred approximately 500 to

600 years aga (Sugden and John, 1973) and the other around 265 years

ago (Curl, 1980).

Weddell Sea Region

The early glacial history o~ the Weddell Sea is poorly resolved.

A few piston cores have penetrated Pliocene and Miocene sediments,

and even some reworked Oligocene sediments near the Maud Rise, however,

the glacial-climatic record is difficult to infer from these deep

sea sediments. I attempted to reconstruct the glacial record using

variations in ice-rafted detritus, calcium carbonate content, and

benthic foraminiferal assemblages in abyssaldeposits ., (Anderson, 1972) 0

. Now that I more fully understand the complexities involved in inter­

preting deep sea sediments, I am ~orced to abandon much of my earlier

concepts and results; more on this problem later.

If we examine the single channel seismic records collected by

Norwegian scientists, we see that sedimentation oh the Weddell Sea

continental shelf experienced a dramatic change sometime in the

not too distant paste This change occurred when the Weddell Sea

Glacial Unconformity was formed (Fig. 16). Prior to the formation

of 1~his feature, the shelf experienced active progradation, with a

large delta being situated somewhere in the vicinity of Brunt

Megatrough (Fig. 17). Thus, if a glacial maritime setting existed

at this time it was a temperate one, with meltwater streams, not glaciers, delivering sediments to the sea. 26

This rapid shelf progradation probably took place on a shelf which was situated at more normal shelf depths «180 m deep). This is implied by the eustatically controlled downlap - onlap geometry of delta sequences (Fig. 16) and the fact that the Weddell Abyssal

Fan was apparently active during this time (Anders on , in press) .

Presently the canyons that fe d this fan were isolated on the upper slope, their heads having been eroded during the glacial erosional event.

Based on our understanding ofthe Antarctic Peninsula glacial record, this situation could have existed throughout Miocene time when temperate vegetation existed on -the South Shetland Islands.

The glacial regime of the region changed dramatically as the ice sheet advanced onto the continental shelf, lowering the shelf by erosion and isostat~cdownwarping to create the present deep

(SOOm), irregular topography that exists today (Anderson, in press). The tills that were deposited on the shelf during t~is glacial maximum (maxima) were clearly derived from ice flowing from both East and West Antarctica- (Anderson et al, 1983; Fig. 29).

It is far easier to explain an advance of the ice sheets, especially the East Antarctic terrestrial ice sheet, onto the shelf if the shelf is subaerially exposed than to have the ice sheet advance onto a marine platf,)rm. I , believe that this glacial advance occurred during the Pliocene and was probablytriggered by a glacial eustatic drop in sea level resulting from build-up of both northern and southern hemisphere glaciers. This is based on changes in the $ 0 0' fiQ' 4~~~~~!IIi::_- r .... i:~. . ..I'5';~ " ,. ,!?-, ., . ~~3O"W'.r::r.P. , ~~~~,\._ ..20:-· L. 'S' I.Y-- : ~(~ . .. t:,' . ~ :",L ',,' •• ~;W ·61 " , ... -> ~ ~ .\i ""'-., ",':" ' '':'-~f::' : ; . . '. :,:" . '&-~'- _o ...... ~ ,::-~ . 62 ' '63 ' ,;; .... ':- , ,<;-- - ; . •&tl> : . ,,-~:---:~:: \ ~ ~ . : ~ Q , .~ --.66.0 G\ -, -~\:~ ' - • G2 ;67 - ... • GI GIS ti8 ' • ti8",. \. 4e~· t!l Gt7 ;:> . .. ,~ • .., 2,20,\ :. \ .. .. :: ..r~ " 69" i\ r) ... "0 2 ·22 '\ I .~. I ' " 0 3·... l\}( 1t , " 0 3,\-2 , • 3-3-\ .;~:idf~'- • 3 ,'.-\ -{ : ( 1 _ _ .: r -?:< I..l ~ ~0 _ !> . 11" * t6 ::·'i·. ~~~l~:­ ;" . ' _ > ~ _ ;_. ~~" ,,"./~.{"'J- \;!. ~. ." ,'. .: A n . ;...... ~"- ...... ~ .,' [.---'- ~.~~ s, ' ,n' 0 2t I ~ ~\ ...- 30 .,. ' ,' • tI-",+,,,,t- 73 ': t --. • _,_ . ; _I")~ n - ...~~ ' ... 14' 14' _ Jz . _' C ' ~ « :( - . > A~ : 4', 0:: . ,. , ~~ ,,,,:: . '- .. , ,, '1'11'. . i" \)t"~ . ]5 , .J,U- !; f-O <.: 1!> ' ~j ~t- ~ .J '"...... ' ' \:(( ' ~. . UJ . " ., . .. . 76° . " . .": , ,16 ' '.' ". , y.. ,jr Y -- _ . lil" . '.. ' .;,-( , ~ . n ' n-; AO+o"'t: ICl SH l L~ ... .'. ' .. >l.\~, :" ;> ' ; Q~~~ "'/ _ GOU' . , ', ,'F '/'(' . ·• •·c- ., ,~,~ .", o.' .. ' ~' .7; .J .,~ 78 " S ~ \ ._ ' .' ( ',\.t:; . ,. 25 ' :1O"W 15 -- 10 " "66. ' , ,J+~ . ::," JO:W ~,+' ,. ' . • . I ~~. - ::. ~. _) f".... H ... d . ,':l SIIHf \ 19" ' - ' . '--...... ~ Figure 29. Mineralogie plot for basal tills from the eastern Weddell Sea. Six till provinces are recognized whose distribution is shown on the adjoining map. Q/F=Quartz/Feldspar, I=Igneous rock fragments, S=Sedimentary rock fragments. (from Andrews, in pre~eration) 27

character of abyssa1 sedimentation in the region, most notab1y an apparent increase in fan activity (Anderson et a1, submitted).

At some point the expanded ice sheet was no longer ab1e to sustain its marine terminus, probab1y as sea level rose at the end of the Wisconsin, and it retreated back to its present coasta1 position (in the case of the East Antarctic lee Sheet) or ice she1f configuration (in the case of the West Antarctic lee Sheet). Given

the existing polar glacia1 regime of the continent and the great depth of the continental she1f, terrigenous sediment supp1y to the she1f and deepsea f100r was cut-off. Anderson

(in press) ca11s this the major turning point in the evolution of the Antarctic continental margin and in abyssa1 sedimentation.

For examp1e, the Wedde11 Abyssa1 Fan, which was thefoca1 point of

terrigenous deposition on the We::1de11 abyssa1 f100r prior to this

time,became inactive as the canyons which fed< it were iso1ated on

the slope. The timing of this retreat is uncertain. E1verhoi (1982) 14 has obtained Wisconsin age dates (C ) on glacia1 and glacial marine

sediments on the eastern Wedde11 Sea she1f. Behrendt (1962) has

used gravity data ~o infer that Crary Trough is still in isostatic

disequilibrium, and Anderson (1970) sites the very thin veneer

of modern sediments covering glacial and glacia1 marine sediments

on the shelf as evidence of arecent withdrawa1 of the ice sheet from

the she1f. 28

Bellingshausen Basin

Four sites were drilled on the Bellingshausen continental

rise and abyssal floor during DSDP Leg 35. (F'i:.'g~;- -30). Turbidi ty currents

played an active sedimentologic role in delivering terrigenous

sediments to these sites duringMiocene time, making it difficult

to interpret the pelagic and hemipelagic record. By Pliocene I time the influx of terrigenous sediments to these sites became more variable, which probably reflects glacial eustatically controlled

fluctuations in sea level and supply of terrigenous sediments to

submarine canyons of the region. Significant quantities of ice-

rafted debris began reaching -these sites in Miocene time, but an

extensive ice cover probably did not exist in the region until

late middle Miocene (Tucholke et al, 1976). During Pliocene and

Quaternary time there were apparently several glacial fluctuations

(Tucholke et al, 1976). c J) I/(H . 11~IHt. L{" H. . \IlI )(JC~

BElLi I>GSHAUSEN ABYS SAl PlAI N ANTARCTIC COIHlN ENTAl RISf sm m I slTEm sm J2( I SITE J2'j 60 ~ OI. '·". {1' Z'J.S ' W I f>q ' 0 ' .... \ . qfl." "'.:". I 65 "02.8'\ 1) ~ "" WATU O[ PTH S026 (1'1) ...ai[R O[PTH 4993 (m) WAHR Q(PTH 4449 (11) WAT[R O[PTH J'"'' .

DESCk l PII OI

( 14" ..... 1 ,I'i ( 10I 1. ')( . II ) dutn.-,.' c@o .. S . wltfl ~ -.: .tt~ "'" lJy~,.\ 01'10"', ' \orted

''''rrht'f'l(ll'd 'Icly~to'''''' ,"J ~ 11 t',to,,"-; .. ',' I';I'-"oI",f"U D \ 'lfYCl,1.f C:"brl-,

CHERT CI'yH~ 8 wllf'l l .,."r' ',f 1'1'1'1".., 1'" . \ ~ AA"")fO~Sl lS ',I\H. ' I ·., ·I..,

E]UA:;AlT

""""',1,,",,\ . ~ IIt·.1ft...... ,, ~ , I.I~· ~. I ""'0' . ,... ,.... ' .. .., 100 wsr·leHT,...,. ..: l"'On~ " · :'·,1 QIIt OlDEA

'--~-~ ,------..-.--- -:::--:.~=::-- --- :;.;;;;c...... _------

IIOGE fLANK

(1ft... ""1.. ' Tlllrp, '972) ElLSWOITH MTS

F...... 1. ~«I plrylÜ>fNPlly 0/ the Southuu hcijk &uiIt Md /oatiOll 0/ Lq 35 Site. (Il/tn HHZm Md 1Mrp. 1972).

Figure 30. DSDP Leg 35 site locations and core descriptions (from Hollister and Craddock,1976) 29

Sedimentation on the Continental Margin

Weddell .Sea Margin

Piston cores were collected from the Weddell Sea continental margin and the continental margin of the northern Antarctic

Peninsula region during Eltanin cruises 6;7 and 12; IWSOE 69 and

70; Islas Orcadas cruises 1277 and 1578; and Deep Freeze 81 and 82.

A number of short gravity cores were collected dur:hng IWSOE 68 and the 1977-78 Norwegian Expedition. These cores have been studied by several investigators (Anderson, 1970, 72; Anderson et al. 1979, 80,

82, 83a, b; Kurtz and Anderson, ,1979; Wright, 1980; Harlan, 1981;

Fisco, 1982; Elverhoi, 1982; Wright and Anderson, 1982 and Wright et al. 1983). Ongoing studies with which I am familiar include those of Singer, Smith, Baegi, and Scientists involved in the recent

(1983-84) Polarstern expedition.

Cored sediments from the eastern Weddel1 Sea continental shelf include relict basal tills and glacial marine sediments capped by a thin layer of Holocene Muds (below 300m) and sands and gravels

(above 300m). Sediment distribution patterns for the area are shown in figure 31.

Sedimentation on the continental shelf involves a comp1ex interplay of glacial, oceanographic, and mass flow processes. Pre­ sently, marine currents, particularly impinging geostrophic currents, and mass flow processes are the main sedimentary agents, however, glacial sedimentation clearly dominated at sometime in the not too distant past (Anderson et ale 1979, 1980, 1982a, b, 1983a, ~; 400W

WEDDELL SEA

\ I

1 80°

, . . , ' .

Figure 31. Sediment distribution patt:=n for the eastern I Weddell Sea continental shelf(from Anderson , et ale 1983). 30

Anderson, in press; Wright and Anderson, 1982; Wright et al. 1983;

and Orheim and Elverhoi, 1981) ~

Marine processes, including mass movement, have clearly domi­ nated sedimentation on thecontinental slope, even during the more re cent glacial maximum. Slumps, debris flows and turbidites are widespread on the slope and are interbedded with laminated silts assumed to be contourites (Anderson et al. 1979; Kurtz and Anderson,

1979; Wright and Anderson, 1982). Turbidites on the she1f are derived from glacial sediments, through mass flow transition pro­

cesses, and are therefore of little or no paleoclimatic significance

(Wright and Andersoti, 1982; Andrews, in preparation). This process

is apparently confined to the steep continental slope in the north­ eastern Weddell Sea.

Cores from the southern Weddel1 Sea slope penetrated inter­ bedded laminated silts (contourites) and diamictons (debris flows).

The absence of transitional flow deposits in ,this area is attributed

to the more gent1e slope (Wright and Anderson, 1982).

In the northeastern Weddell Sea, geostrophic currents impinge on the upper slope, scowering it ' to produce sands (traction current

deposits) and gravelly sands (lag deposits). This process and mass movement have probably played active ro1es in slope sedimentation

in the Weddell Sea for some time.

The Wedde1l Sea continental rise is mainly floored by laminated

silts with small but variable concentrations of ice-rafted debris

and calcium carbonate. paleoglacial and paleo-oceanographic inter- 31

pretation of these deposits is complicated,as discussed in the chapter on abyssal sediments.

Northern Antarctic Peninsula Region

Piston cores collected during Deep Freeze 81 and 82

(Fig. 32) are presently being studied in detail by two Rice graduate students, Jill Singer and Mike Smith. They are both in the early stages of their work, so I will not attempt to describe their initial results. Both studies should be weIl underway by the end of this summer. In general, the Bransfield Basin is presently filling with siliceous sediments at a rapid rate (Fig. 33) . This bio genie sedimentation was likely masked by glacial sedimentation during glacial maxima and by turbidity current and meltwater sedi­ mentation during glacial minima . consequently, the sedimentary record of climatic change may be quite conspicious. Keep iI. mind that sedimentation rates have probably been high, so a high resolution re cord for at least the last 2 million years likely exists . 0 0 0 0 0 ,.... C\I ('I) ~ Ln CO CO CO CO CO , I , , ,I • ~ , I « , I • • , I <6 W , , '" • \C) • \ ... CI) , ...... - , ..• , .. I , ... -- 'e, I I -- ,- . --- - -..;;,j ~ , I --I ------( ...... I I , rf.l \ r , I • W s:: 0 I \ " 1 o \\ Cl ..-1 1.0 \ \l \ \ • .p \ • 1.0 0 \ , • •• Cl cU ~ ,, u 6 , 0 • • w o , , • I , I -- , I 0 • rl .... .- , j 10 • ~ .. , • (I) "- I I • • I • I \ H I \ • • o \ u I. \ \ • • • • I \ , \ • • •••••• \ , • ...... " .... • • • \ ,, • , ••• ., \ . \ ,.. \ , ce, "" \ . 9-, 0\ \ ~\, • • \'0 · .... . \9- , ''''''. 0 , , . . .~..... '"'''''' . "~,.""""""""""""""", o co Ir

\ ,',.' J

r;'~ ~:~ _,Nt\, "

~j ~!, } 1 (I;\ l;k ;~ et~f ~"" ;~ -'1~~. "Ii. ~ ~ ~., i 0101277 ro< -, t1;] 1-":-1 .101578 AIWSOf .. ELTANIN ~~_.~:.~ !'i:

; ,~. K L ,..f ' r o' ,.~ 3crE r~ } 4S"E f · ~ . ; . n ~ ' .E Figure 33 . Surface sediment distribution for the Weddell Sea Region . ö ~, t;:: 32

Sedimentation on the Continental Rise-Abyssal Floor

Seismic Studies

G~ophysical data collected in the Weddell Sea have been

examined by LaBrecque and others (1980; ), Haugland , (1982), Maisey (1979), and Hinz and Krause (1982), but none of these studies were concerned with the sedimentary framework of the I basin. LaBrecque et al. (1980) suggest that the basin is filled with turbidites, but provide no additional information. Seismic reflection

J profile data collected during the Islas Orcadas cruise 1578

were examined by Fisco (1982). She compared the Weddell Sea records

to records from the Bellingshausen region, where Tucholke and Houtz

(1976) have described seismic characteristics of various types of

deposits.

Finely laminated sedimeTIts occur on the upper and central con­

tinental rise ofthe Weddell Sea, and are interpreted as turbidite

deposits (Fig. 34). The individual laminae are fairly continuous,

and can be traced for relatively long distances. These laminae are

broken occasionally by submarine channels which appear to have mi­

grated eastward through time, building thick, poorly laminated levee

deposits on their western edges (Fig. 34). Tucholke and Houtz (1976)

have noted a similar easterly migration of channels in

the Bellingshausen Basin. C~~'f\'J'\Q\ pu;,\t" \jvr ISLAS ORe .:. DA S • •• i · .)~ •• .. •• • • • • 157E • ;:- ~ T H O M S r

I i ~~= ~'~ ' ~: ~~'ft'~;i::f; ". :, :; :!tJ;f(~ tj'l~ft~ti A '. .'1 ~2C:O ', ;

:cCO

':4CO

i f ;, ::2CO 2~ :,.'! i ' ~ , " ' ~!: " .. i, ::h ,.T ~~ '~;· I r : ·dl;I~.i ::: lh~i,j; H 'I., l; ~i~ . ,. ~ ,.( ',' ; 272°"1 z_- " o~ •'-2 58° !! I: e I = ~ !'E:: & & i Jl

l igure 34. Seismic reflection prc~iles collected during Islas Orcadas Cruise 1578 showing laminated deposits presumed to be turbidites. A channel and associated point bar and levee are also shown. Profile provided courtesy of Dr. John La Brecque. 33

Piston Core Studies

Piston coring of the Wedde11 Sea abyssa1 f100r was conducted during the 1969 and 1970 International Weddell Sea Oceanographic

Expedition (IWSOE), during Eltanin cruises 7 and 12, and during

Islas Orcadas cruises 1277 and 1578 (Fig. 35). Studies of these cores were conducted by several workers (Anderson, 1972, 1975a, b;

Wright, lS80; Wright and Anderson, 1982; Fisco, 1982; Wright et al,

1983; Defelice and Wise, 1980; and Ledbetter and Ciesie1ski, 1982).

Figure33 shows a surface sediment distribution map for t~e

Weddell Sea and surrounding area. Major features of this map are:

1) the extensive region of terrigenous si1ts and c1ays

which occupies the entire basin and extends some dis­

tance north,

2) the Drake Passage Scour Zone.

3) the limited and shallow distribution of calcareous

sediments? and 4) the far northern distribution of siliceous biogenic

sediment, with the exception of those that fil1 the

Bransfie1d Basin.

Figures 36 through 39 show lithologic descriptions for piston cores taken on four transects across the Weddell Basin.

The eastern most transect was taken across Maud Rise.

Cores 39 and 37 penetrated sandy and silty turbidites ponded behind this feature. Maud Rise is an eroded feature with Pliocene and Miocene biogenic sediments (most1y siliceous) buried beneath ----.. ------

0101277 .IOIS78 AIWSOE .. ELJANIN

o· 30-E 4S·E

Figure 35. Piston core locations for the Weddell Sea.

~ pe /518-52 pe /518-55 pe /518 -56 K EY SYMBOLS USED FDR CDRE DESCRIPTIONS ::- ~ ..'l, . '.r .. 'eU, .. ,1 •• ,. ~lfj, ~e:~~ ...., •. ,I_,r,IU I .. ):s [ T ~~1 i I ~ ~ ,,!lI( ". ,., ~ "IIc_" n ...... , I' .IUI ~ ... \ .. " ...... ~ ~ • l .. ,llI ...... , .• ,.u.u •••• •'1' ~ .. ~ ~ 0 · ~ L:::.;.:l W·· ....· ~ .. ," .... . ~ al •• _ ' ...... ~ ~ ' ••t , _. ' ''1' .. '_ t.IU•• ' ...... , \, . 1011 La o c h_" ( I ., , •• ".tU" " I•• " , h, I~€tfl ~ ''' C ' O ''''''''II ~O ''I.' Milli Mn \,,_ 0 11 , • .... ~ ••• t, --~~~(I I.t • • " •••• ,. ,I",,'t" "' E0 ~" i.,u.",I, u ~, •• I" ::t --:c~'i~ Ir, ••• 141> " """ lf.F.1 t .... ,lhl, U "1-1, 1 ~ hll" ,1 1 1 , ~ .-:: n° ~ ~ , e _;~ [2] ;'0' ~ _.l, 11 _, ,~ ~~~~ ..... " .. ~ij/l J. o • ~ •••• I . ... I e.'"'' 1\ < .- < S" ."I I, "U_" ." \ Tor '.r.'"' .•• · .... ·••· ~....~ ~ ...... ,.ul, ,. 01,_1, ".,." •• @ ~ • • I " ...... f'''l /._= ~ I '. ~ - - -' I ~, H··' ..· / ~

~' , ' ~ ------;\ --- , :-" /~ .. :...... ~ . / " , .. \ / . - tt...... -'\...... ". . 4 1 t "'" - '.- ,': Lithologie deseriptions for Islas Oreadas Cruise 1578 ___ _ 4 ~ Figure 36.

~ Fig. 35). Use same key ,- g piston eores (profile D of --- :-=- 1"- for figures 36 through 38 (from Cassidy et al., 1979, ~-. _ .' -_. 1980) . J I_V 8-44 '~'b' ·I., PC /518 - 4J 1) ,"9 • .; ? 15l8- .J ~· 1,18 ';y 15'8-41 ,578 - 40 15'8-41 1 .. 1 1 ~ ...... : [. I c .> ~ . ~:J~- ~ ': t , LI ... " .- I' 1 I' ~ , _ "" \ ' ,:!. ~ , I "'lU~~. ------'...... :... I (. I···li rr:~~ . - -"7 ~r..,--, ' ~"- L:.:~ - ~ ... ! f- r-:-F- ) /' f t - ; ~ i·~···: "'. ..: ...... -- I ...... • 11 --~ . >! ~ . ~~ . .?.. , ':' - J( , ~ ;" ! --- . " 0'.Y ...,: ) f----- ( I ...... - .:v " . j ~ ... ), ~~;!'~~' v· y " , v. - I ---... f---- ~- ~- ': -:: -~ ; v.. , ~ '. H ~..:r::::-.. i ;:.'! ~~ -,:: I i.. ~. 41_ :,,;::::.... . r " «, . v 1 ~. -~ --, . - ...... f· 1/ , . , -I .. .! .... ' --- ~,··I ... JJ~ , I ,>' ..~ . :.=:: ~~. ~~{~~~ " I~ ~l";"',';";" ~ ~ -. :~ .~ ~ •• ', .oe II. V . ' . ~ ~".:.",:,. H : ~ '. ".~ . - • t-- '0' ...... 'v I ~, ~K\ ",p r--- .. ~~.:~ . '.~ -:-.;: ;' ::-': v ...... • '\ ,-. ,...... ,- , / .. v ... -,/ ) ," ~ . ;. . r F- ""'J . ~ . Y ~~~;f ~" ) ~.~~ ~--;~; . k.4. ~ .... ' ...... ,...... ;, Y . -,Y I-- ~~~, L.;·, -".v: ~. : ~~ :-::. ;.1_ -.,~- ' V .', V ";'.y.' ";=::1{_: v . ' . ,", .. r , ~ ~ . '. ,~ ., 'f', V; v 4 . V ~ __" _ ~ <00 ; -;-:~~~ '=7i~ 1 ( ) 5 " I .:.:-:

~ --'C:-" I ',' Figure 37. Lithologie deseriptions of piston eores eolleeted during Islas Oreadas Cruise 1578 (profile C of figure 35). /518-/2 /5!B-/4 /518-9 /518-/0 /518-1/ /5!B-6 /5!B-1 /518-8 !. - ~~ ~d::li _.<

;~:::~ .~ ~ c t;f,

~~ , ---

: :::::: ~: . c::; ~ : t~ ,

Figure 38. Piston core descriptions for cores collected during Islas Orcadas Cruise 1578 (profile B of figure 35). 1211-J1 1211- J6 12"'-J5 1211-J4 1211-JJ 1""-J2 12"-J/ /211-Ja 12"-29 1 ~ElrrCA.~ ,:r~li !~,., <.-::~~ ''' · ..· · :E ·''.. ~ .. : :v. ~~ 1~ ~l- : ::..:; <, .-: (.,., ~r : :< : ;- , .. -.~ .. -...... " ... ~ ...' . -.'

"' ... . -..

V . V . " ••••••• 0' ",.r- ~ .- ?.p - ­ ~ "."o-.V "'-'. "1" ." " .".".V ·.·-".·.v". ... v .~ .· . - "'"oo.V ." . -".' 4VI : ; : : : ~ a ii' <;:1 .•.. "::~ h :.-: .-:-: - ~ .-: V --:- .-:v: -,., . .., ~ ~~~~ . -: '.

:-:-. Ia- ~

Figure 39. Lithologie deseriptions of piston eores eolleeted during Islas Oreadas Cruise 1277 (profile A of ·i:~~1 figure 35). -=.:=-;- 34

a thin foraminiferal lcig. Erosion of this feature by circumpolar currents is implied (Ledbetter' and Cies:Lelski, 1982), although some disagreement exist between these authors and Defelice and Wise

(1980) as to the age of these sediments~ lt is also odd that a significant lag surface was not created by this erosion; the Quater­ nary sediments eroded from this area would be meters thick and contains at least a few percent sand and gravel' (l·RD). Fisco (1982) estimates that a lag surface 0.3 and 30 cm thick should have been produced by this erosional event. Furthermore, this erosional event is not seen in the Weddell Sea (Anderson et al. in preparation) which is.: the source of this AABW. Transects Band C show that the zone of siliceous mud and ooze deposition bordering the Weddell Basin to the north has not fluc­ tuated southward during the time span represented by thes e cores (Pliocent-Recent). An important question that we must address is whether ·these cores record the dramatic glacial events described in the earliersection, surely these events were as spectacular as any that have likely occurred since the Antarctic ice sheet evolved. lf indeed these events .p,re recorded they have left only a subtle imprint on the abyssal record. From my own experience in attempting to interpret Weddell Sea abyssal sediments, and that of my students (Harland, 1980; Fisco, 1982), I arr. left pesimistic,.about our chanceso of obtaining a good sedimentary record from the abyssal floor. The problem sterns largely from the fact that the Weddell Basin has for some time been the site of widespread turbidite deposition (see previous section). lndeed, most of the terrigenous silts and 35

elays penetrated in piston eores from the region were probably derived in. this manner. Note the sedimentary elasts· are eornrnon in eores from the region (Figs. 36-39). Fiseo exarnined Weddell Sea abyssal sediments in detail and eonstrueted a list of eriteria that ean be usedto distinguish fine-graineä turbidites and debris flows from hemipelagie and pelagie sediments (Fig. 40). This requires eareful, time-eonsurning work, but unless these distinetions are made we will not be able to diagnose glaeial and paleo-oeeanographie events from the deep sea sedimentary reeord. 12:3

:fEI;TIPELlGIC DE~RIS PLO'o" SAlm l:SIU' r.:m J ~~'9I!)I':'!! Tt';t3IDI~ SZOIr.~lT bior.enlc bio~en1e debr. any sediment . terrl~8nous, 'terrigenous, SOl'RC! debris e~em. ehem. ~reei~. ty). or SOureE biegenie. or bio«enie, or "'r.ei~ 1tation. ",indblown, IR!:) ehem. ,pt. eheo. :!l!'t. wlndblown terrl~enous r :~~"PC'R'" settlln~ settl1n~ debrls tlow turbidlty t~b1dlty ··!:~'lfA."IS·~ t~oW!;h water t~ou-?;h water, transport eurrent tlow eurrent tlow co l1lD".n , ~owth :ppt • • 1:1'indbl., (turbid eloud) or ~~t. on eurrent trans- -- bottom !'ort un80rted silt unBorted, all unsorted. all graded. wall unsorted fine and elay, slzes. homoga. slzeB. matrix sorted. sand silt to elay S:::DI:,~rr large shes normal eompae- greatar than to eoarse silt sbecl :::.A.RAC':ER trom biota or tion (water- 20~. com:pacted. sized. no IRD, sometillles more ISUCS ehem. ppt.. rieh). luger oeeasional!y us~. less than silt at ba.sa homogeneous, grains usu. reversed 10;. elay than at top, normal co~ae- IRe grading. eomponant :e-t.:n miero­ ti on (water- containing few elasts or nods or CaCO, rieh) sadimentary lag at base oecasionallY'i elasts very llttle or no IRe

burrowed, burrowed. mottled. homo~.usually usually homo~eneous, homo~eneous. or mixed look, massive, laIIlinatad Or If no fauna or laminated sometimes (inn-equent on bOttOlll, If no fauna . evidenea of a ,:;' lam, x- laminated on bottomr rigid plug, .) ash laminae, elasts in zonat: dropstones or seattered

basal ~urrowed. burrowed,or sharp or sharp, erosive sharp, gradational gra.datlonal iburrowed, sometime. with eroeive, CO:ruCTS lag or 8ed. wlth elasts, elasts a.t base or gradecl upper sharo If eros. sharp lt eros. sharp or sharp or graded sharp or or bürrowecl & or burrowed & burrowed gra.ded &biot. __ . __.. ._ ~a.dational grada.t1onal

any thickness any thiekness 20-300 cm P-I00 c:Il 20-100 CIIl ~ uaually IUsually usually '!'~ CK:-r:.:ss

~Dn1::NT- 1 ~A'!'IOH very ow 10w to mediwr. variable high high va.ria.'ola terr. usu. medium llT3 component

Figure 40. Criterea for distingwishing mass flow deposits from pelagic and hemipelagic deposits (from Fisco,1982).

os==:r=:r- 36

Two primary objectives in drilling the Weddell Sea will be to examine Antarctic Bottom Water flow history and the glacial record. These are worthy objectives, but we must concern ourselves with whether they are best achieved in the Weddell Basin or elsewhere.

The sedimentary record on the continent and continental shelf reveals that several major glacial-interglacial episodes occurred during the Plio-Pleistocene, yet the abyssal sediments of the Weddell

Sea bear no conspicuous record of· these events. Again, part of the problem lies in the fact that piston coring to date has been con­ centrated in the area of the Weddell Abyssal Fan where pelagic and hemipelagic sedimentationhas been frequently interrupted by turbi­ dite deposition. We have defined the limits of mass flow deposits using available piston cores (Fig. 41). The southern limits of the fan are poorly constrained due to inadequate core coverage; this is, in turn, due to perennial ice cover in this area.

The northwestern Weddell Sea was cored during Eltanin Cruises

7 and 12 and during Deep Freeze 82 (Fig. 32, 35). We have examined these cores and found them to contain fewer turbidites than cores collected from the northeastern Weddell Sea. Two cores (12-6 and

7-12) were selected for detailed analysis to see whether the Late

Pleistocene glacial events that have been recorded in the South

Shetland Islands (see Climatic and Glacial History section) are imprinted in the abyssal record (Fig. 42). The history of AABW flow out of the region is also being investigated. Both cores span the Brunhes magnetic epoche -

~ .ond lurbldil.' UIIID 1111 .. mud turbldil ••

r I I/A ... '111 l. - C";\ . t ;;no' r".'l·.t;',:·, "," k:; \ I f .45"' ~ f Figure 41 Distribution of mass flow deposits in the Weddell Sea (from Fisco,1982). CORE E 12- 6 CORE E 7-12 \4el.(cm/sec) IRD% M' veL(cm/sec) IRD% 60 70 8.0 , ~ Ip 15 0 5 10 15 20 5 100 5 10 , t 'L- • I:>' . . , 0!:E I I .....-,--...... 0-_-' o T I Cac03 1 I 10 __ car3

200 200 -r(~~~ -e -- u I ~l -&&J F./Mn ct: FelMn 300 o~o 1 ~ ...% CL4

Figure 42. Example of variations in grain size, calcium carbonate content, and Fe/Mn micronQdule content in Weddell Sea abyssal cores. 37

Our method for determining bottom water velocity from grain

size data (Singer and Anderson, in press) differs from that of

Ledbetter (1979) and Huang and Watkins (1976), the latter proeedure

is based on false assumptions about the meaning of the grain size

parameter skewness. The veloeities determined from mean grain size

(Ledbetter's method) vary signifieantly (2 -to 17 ern/sec). However,

our flume experiments have raised some serious questions about the

reliability of grain size parameters as paleoveloeity gauges (Singer

and Anderson, in press). Also, aeeumulation rates of iee-rafted

debris (IRD) , whieh has been used extensively as a paleoelimatie

tool varies signifieantly within both eores. But again, our

applieation of this method in the past is based on grossly oversim­

plified models for abyssal sedimentation. The same holds true for

· CaCo variat~ons, Fe/Mn aeeumulation and development of laminations. 3 These issues need to be addressed in our assessment of drilling

sites and objeetives, partieularly those of the abyssal floor.

Lastly, I need to address the problem of a paueity of miero­

fossils in Weddell Sea abyssal sediments. The distribution of both

ealeareous and silieeous mierofossils with the sampled sedimentary

eolumn is quite patehy. This is probably due to dilution of the

pelagie and hemipelagie reeord by turbidites. More detailed miero­

paleontologie work needs to be earried out onavailable piston

eores, and probably more co re need to be gathered to assess this

problem. Ande~~on, J't:8~, 1972~ The marine geology of the Weddel I Sea. _ ~ISS, su rnl tted to the. Depart. of GeoJogy of the Florida Stat. Uni v ., :-.C§ff1 J,' ,i d;:., ' .' _:;;. ~ 2;:: 0 pp. ------...'. • -" _ - '1""

Anderson, 'J .B., 1975a, Ecology and distribution of fo "f . the Weddell Sea of Antarctica: Micropaleo t 1 ram~n~ era in p. 69~96. n 0 ogy, V. 21,

Anderson, J.B., 1975b, Factors controlling CaCO dissolution in the Weddell Sea from foraminiferal distributü~n patterns: Marine Geology, V. 19, p. 314-332.

, An der so n, J. B., T h e Ar: t are t i ce,:. n t i re n t .;.. 1 ~=; h t? : f : i 'I T i n ge >., R, J. (ed.), Geology of Ant~. r·ctic~., O ::~ for ' d Un i'.) , Pr':! == , i n pr·e ·5·;.

Anderson, J. 8. ~ and Myers, N. C., 1981, USCGC Glac i er Deep Fret?zt? 81 expedition to the Amund~en Sea and 8r an s fi ~ ld Strai t: " Antarcti c- ,Jour. of Hle U.S., ~.) . 1 6, p. 11:3-119.

Arlderson,. J. 8., BraKe, C., Domack, E., ~1 :" " er" ::" N. ,~nd loJr i gh t, R. , 1983b, Development of apolar glacial-mari ne sedimentation in 0 deI f r· OrTl An t ar c t i ': G! I,B. t e r· n a. r ::. ., . d e p 0 -:;. i t .:. .ö<. n d ,~1 .... c i 0 1 0 i~ i ': a 1 i n­ formation: in 8. F. Moln i a (ed. ) ,Gla cia~ -Mari n e S~di~ent­ ation, Plenum Press, New York, p , 233-264.

Anderson, J. 8., Andrews, 8., Domack, E., and Myers, N., 1983a, Evidence for widespread advance of both the east and West Antar'ct i ': i .-~ ,·:.heets I~nto the cont i nental ':;hel f dl.Jr i ng the more recent glacial 'history of the continent: Abs. and Pr· CI 9 r· ~. m s f r· c,m t h e G €- c. l. So c. c. f Am e r· . I n d i a n .... I="~ 1 i .; , I n d i .=-. n a p. 515.

Anderson, J. 8., Kurtz, D. D., DomacK, E. W., and 8alshaw,K. M., 1980, Glac i~ l and glacial marine sediments of the Antarctic c CI n tin o? n t a. 1 ':. h e J!..I e .:.: ,J C".J r n ·a 1 ':' f 13 e cd 0';' ::.', I.). 88, n CI. 4, p. :3 9 ';' - 414.,

Ander ·:.c,n, ,J. 8.~ 1< I.Jrtz, D. · D., I"..!ea ver· , F.~ .;;'.nd 1.·. .Ie .a l.,1er·, ~1., 1982, Sed imentation on the West Antarct i c continental margin in Craddock, C., ed., Antarctic Geosc i ence: Mad i son, Wi sconsin, Univers i t y of Wi sconsin Press, p. 1003-1012.

------~_._--_.. _ .._- --- Anderson, J.B., Kurtz, 0.0., and Weaver, F.M., 1979, Sedimentation on the Antarctic continental s lope: SEPM .spec. Pub. No. 27, p. 265-283. Anderson, J.B., Kurtz, D., Weaver, F., and Weaver, M., 1982, Sedimenta­ tion on the West Antarctic Continenta1 Margin: in C. Craddock (ed.) Antarctic Geoscien~e, University Wisconsin Press, Maaison, p. 1003-1012.

A':;hcroft,I,.,,- A., 1972, Cr'lj:;t,~l;.trl.Jctur€' of the S.:lu+.h She+'iand Islands and 8ransfield Strai t: Brttish Antarctic Survey, Sc _i e fl t i f i.: F.: e P ':l r t s, n c.. 6.:). 4 3 pp.. ------_._------

BarKer, P. F., 1972, A:,prea,dir.. ~ .:enter in tht? E,~,st 3coti:o, ~3e . :;. , : E~,r' th:o,r.. j Pl,~,net,~r':~' Scienee Letter':, ').15, p. 123-13'2.

Bar I< e r', P. F., i) a 1 z i e l, I. t'-'. D., an d 0 t, her' s , 1 976, T h e e v 0 1 u t ion of the S. W. ~tlantic Ocean basin: Leg 36 data: Ini tial R.ports o~ the Deep Sea - Dl"'itltng Pl"'oJect, U. S. Govel"'nment Pri~ting Office, Washington, D.C., v. 36, p. 993. t;.--

Barker,. F'. F., and Griffiths, D. H., 1'7'72, The e',JohJtic.fl of the Scotia Ridge and Scotia Sea: Philosophical Transac~tons of the Royal Soeiety of Londen, Sero A, no. 271, p. 151-183.

Barker, P. F., and Griffi ths, D. H., 1977, Towards a more certain reconstruction of Gondwanaland: F'hi losophieal Transactions of

the Royal Society of London, Sero B, no. 279 J p. 143-161.

Barker, P. F., and Hi 11, r. A., 1981, Backare e:>

BarKer, P. F., Ba,r't,,?r' , P. L., ,:O.nd ~::in.~, E. C., 1982, Ridge .:re-:,t­ t ren c h C 0 1 1 i :' ion c.6 t h eS,:. u t h ~=: c 0 t i a R i d 9 e (a b ':, • ), in,} am es, P. R., ,J ':.. 9 0, ,J. 8., ,:0, n d I] 1 i ',) e r', R. L" e d ';:, ., 4 t hIn t ern a t ion a 1 Symposium on Antarctic EarthScience, 1982: Adelaid. Univer­ si t y, Au s t r' al i a, p. .:.. ,

.. _------~--~.- Sehrendt, J. C., 1962, Geophysical and glaciological studie~ in the Filchner lee Shelf are~ o~ Antarctica: Jour. of the Geophs. Research, v. 67, p. 221-234.

- - ---'------8ehr end t:, .J. C., 1 983, Ar. e t her e p eo t r .:l 1 t? um r t? ':,0 ure e ~ i n An i:~ r .: t i - c~? USGS Circular 909. p. 3-24 .

. Bergtr,- H. W., 1977, Me'5'::Iz'::Iic sea floor c'T , Drc,nning t'1aud L.:o,nd, - Ant,~rctica: f'·latur·e, ',), 269, rio. 5630, p •.686-687.

Birkenmajer, K. r 1983, Extent and cause of the P1iocene glaciations in West Antarctica: Bu11. deo L' Acad. Polonaise des Sciences, V. 30, p. 9-20 • BirkenrTI.:<. .jer, ~~., 1'7'81 .;.., Go?ologica1 ~:o?lations. ,:,-f Lions Rump, f

8 i r· k e nm.;...j e r', ~:., 1 '7' :=: 1 b, L i t h 0 ':, t r' a t i 9 r' ,~, p h /' 0 f t h e F' 0 i n t H e n n e q u i n Group (Miocene Volcanics and Sediments) at King George Island (South Shetland Islands, Antarctiea): Studia Geo1ogiea Polonia, v. 72, p. 59-73.

8irkenmaJer, K., 1982a, Late Cretaeeous(?) and Tertiary glaci­ ations of Antarctica: Evidenee from South Shet1and Is1and ( .:;., b '=, • ), i n ,J ,:;.,m e '=, ,. F'. R., ...T . :;., 9 0, ,} . E:., .~. n d D 1 i 'vi >? r' , ~:. L., >? d :'. , 4th International Symposium on Antaretic Earth Seienee, 1982: Adelaid>? Uni'}ers.i Au,;:.tr':..l i,:;." p. 15 t ::r,, I '

8irl<~nmcd~r, ~<., 1982b, F'lic;eeno? ti11ite-bear'in l;l ';:'IJI:I:e·;:.':.il:,n ,:,f King G€'(::lrge r ·::. .vand i '3outh She-t ' ""nd 1 ,:,j ",nd", Antarctica): Studia Geologica Po1onia, v. 7 ~, p. 7-72 •

• • "" . _____~ ...... ___~. =-"""" __ "...... ,'''''-c ______~. __...... __~-_. __ ~~ - -- BirKenrnajer' , K., Gazdzlcki, A., arid 1.,Jr·ona, R., 1'7'83, Cr·eta.ceolJs and Tertiary fossi ls in glacie-marin~ strata at Cap~ Mo?lvi 1 lo?, Antarctica: Nature, v. 303, ne. 5, p. 56-59. ---- ~ --...... ---

Bishop, D. r/J, and I·)a.rt Ede8 J . O. R., 1971, E ::q:.l ,:;.,nat':Jr;.' t€'xt for' the ~ i?ctonic rria.p of Africa::"re·3, .:o-:.o"dj1'\a~d · b)" the' South.,..n Gro_up.2. Tectonics of Africä: Pari ';', UNESCO, p. 561-585.

-~------~ Cie:. i>?l:ki, P. F., a.nd ,J .XI€- ' :.,:3~ ,J., 1''779, ~;ediiTIent .3.g e ';;. caf ARA - ' ,- C' t ,-, ... .L - r - .. I' - ,_T c.IJ r rl .a 1, .-, t' t. "I' ..._- r :. 1 E ': .. 0 r· i: .=-. Ij' .~. ":: L: r· tj ; : . e J.:':': I' I ':. .. Ci n '_' ö:=t r· e :. : H n I.. .;j. . 1_ 1_ '_ ~ t Unite-d St ,~. t>?s, I.}. 1 4 , p. 14:=:-150.

-' Ciesi~1ski:- p .F-:-:~d Weam,F:"M:-; - 1974, Ear1y p1iocene temperature changes in the Antarctic Seas: Geo1ogy. V. 2, p. 511-515.

------'''-'''- Cox, M. J. G., 1964~ B@ismic re--fraction mo?asurements in 8ransfi>?ld Str'.",it: 8ulletin eof the 8r' it.ishAntar·cti ..: ~3ur'.}e :: . ' : no. 4, p. 1-12.

D.·a 1 z I. e, 1 I • W• D • , l o. 'qn- -, romment'-' o~ "Me-sozoic evolution of the- Ant~,r ctie .:;.. F'enin:,u1,:.. and the ~=;oüther'n ' Ande ''''": Ge010g)'", I."', 8~ p. 2,~,O-261. Dalziel,_I. C,.). D., 1·?:32.3., The ear· l::." (pr'Eo- mid-,Jura·:.s i ,:) hi·:.t,:,r·:.·· of tho:. '-',nt i - "'-r - ,J;_ - . - . , - ~, --- . ~. H l. 1"". \::' ';;) I '_' n: .~ ·r· e '.} I e 1.. '. .1 ~. n d p r' ,-, q r· 0:. s ·::. r' 0:. p ,-, r· t i n Cr· -3.ddock r: o:. ,j ..... k_ .-t · - ,-. - .___ . __ ~- - _ - . -- .? . _ .' _., - ., H n ',.:J. r '- - I '- ,-' '::' '_' '=. '_ I '::' n '_ '::': ~·1:J. d I .: . C) n. 1.,,1 J .:. C CI n .:. in. Un J '·.!er··:.J ty e,f 1;,1 i -=.'-'-'rl·=.I· ...., Pr.\::,- .:.: n 111- 1--:' ~ ' . --_ . - J! I I -'-" r"" ":-'-' ,

Da 1 - i 0:. 1 r ! 1 D 1 ,-,,-,.-, .... - TI. " - 4 - ! ... t • 'A • • ,. 7' .:• ..:.:. L.I .. f lee I .... CI 1 Ij 1: i CI n I:' t t h e :3 c .:' t i .;., Are: .:.. r e t} j E- '.... .1 (.~. tl'S • >, i n .J ·:'.fTi Er S., ~' . ~:.. ,} . ~. I~ 1:1 t .J. E:,. .3. n d 0 1 i 1. .1 ~ r', P. L 0:. ,-l '=. 4 t t- I ~ I- -. - t : -- 1 ,...... ~ - " . . - ., - -' - . , ,I ,I '- \::' r n .::'. - : '_' n .::'. .=, .:.' mpa': . I lJ m CI n H n t ·3. r· ei::l e E .3. r· t h ~; ,:ien::e. l'-.~I~-_-:.;:. ••.,...... -"-J. j- I" ·t / , 1 - H ',., \::' ; .~. '\::' _; n J '.) e r· : . J _ ::.' , H lJ .:. ": r· ·3. i .3., p. 4 1

Dalziel, I. W. D., 1983, The evolution of the Scotia Are: A re'Jiel:.v: Antar/:ti: Ear·th Seience, Austral j .3.n Academy ''Jf Science Press, Canberra, p. 283-288. - _.~--- ._--- --~--_._._-- _._------' D-3.1 z i e 1, r. 1.,.1. Ö., ~. nd E'l i j .:. t , Co. H., 1 '7'82, 1.. •.,It;.:: . t An tÖ1.r· e t i C:,l. -Pr ob­ 1 em. C h- i 1 d O-t Gcrn dIAI~. n ' a 1 a.:n d : ~:~ !?rr i ': s- , _ ~. ~ 1 , . p • 3 - 1 '7' •

, 'Oavey, F. J:,,,,,J.% Z, Marine gravit:>, measurem~nt ·:. in Bran~.field str-ai t .arL'j ,itdj-a-c€'nt .."r·eas- in Adie, F.:~ .J., ed., Ant~retic - - ­ Ge,:.10'~Y a~ Ge''Jph ;,' sic '3: 0310, Univ€'r·:.i tet ·:.tor·laget, p. 3'7'-46. --.,- -- 0-~'~-'------

,------~...... _-~, --~- -- - ,. Oeacon~ G .. E.· R. ~ '937, Tile n.yd.rQ 1Qgy ' of tn. Southern -___ O_C8!!!l~_~ Jseov.~y__ ~~_~ts., v. 19, 124-. p. - ..-~ ...,. . -...... -- ._-~- ._._... ~-~---..~-~-~~~~-.....:...~---- ~...... DeFelice, D.R., and Wise, S.W., Jr.,l98l, Surface lithofacies, biofacies, and diatom diversity patterns as models for de1ineation of climatic chang in the Southeast Atlantic Ocean: Marine Micropa1eo., V. 6, p. 29-70.

---. ------j'-~ ~ ._------~,------_.------~, - de Wit, M. J., 1977, The evolution of the Scotia are as a Key to the reeonstruction _ of ~outhwestern Gondwanaland: Tectono~ physic:., /.,I. 37, ~(. ~ 53-81.

Diet~, R. S:, and Sp~o11, W. P., 1970, F i t between Africa and An t ar' c t J C ~: .;.. c ,:.rl t _i rl e nt aT dr- i f t re c an S t r· u e t i on: Sc i e n ce, v. 167. p. 1612-1614. ------Drewry, D. J ., 19.83, Antarctica: . Glaciol.ogica1 and Geophys ical Folio: Scott Polar Institute, University of Cambridge.

------'-. ------Du Toit, A., 1937, Gur wandering continents: and 8oYd, 366p • . Ed j n bu r g~l, I] I iv€' r Elliott, J. L., 1'7'72, . Contin€'nt .al dr. ift .:'.nd b.:'.s.i n de \i elopmeont i n Southea.st Au:.tral i .:öI., Th€' Austr' al i an Petr'c,] €,IJm Ex p l ora. t i lXI ~ ~ 4' ~ ~1 ,ournaJ 1 , '..J . 1 .:., no • . _-:~ , p ' :~-' -:' •

Elverhoi, A., 1981, Evidenee for a late Wisconsin. glaeiation of the Weddell Sea: Nature, V. 293', p. 641-642.

-- -'-'-' _.. , -_. ---_.. _---- • Elvehoi, A.3.nd i· ·"1ai ·=. e ~,· , G., 19:33, Glal: i a l erc,:.ion and mCli' prlo l ogy of the eastern and sou theastern Wedde ] l Sea Shelf: Antarctic E .:.. r· t h ~= ; e i e f"1 '..: e, t; IJ ~. t r ';:',; j .~. n A c .~ . Ij €' rn / ' 1:1 f :=; eie n .: e F' r· e : . s, C .~. n b E' r· r· .=s. , p. 4:3:::;-4:=:7.

Embleton, 8. J. J., and McElhinny, M. W., 1975, The pa l €'opüsi tion of t·· ·lada l~2t. ·sc ·:öl. r: pa l .t:· i:.rT;.:..gn;.2 t i C . €, ',i i de ne e f r orT; t hel =.. ~. · l c, Gr o u p : E art h. r' :.öo' n €' t. :=; c i . Let t ., ..) . :2 -;", p. :: :2 .;.- :::4 1 •

- Embleton, 8. ,J. J., and ~1cElhinn)l, 11. IAI., 1982, ~1ar i ne magno?t i l: anomalies, paleomagneti '~ and tt-.€' dr' ift t-, j · ~tor- :-, " e,f (3ünlj :).J .::~nö. · - 1 ar~9_: _ E. .ar ~~ t": ... _ F2,an o? t. ~;~~: _ ~~ . t't ~ , 'l. !_5~~ , p. 141-150.

. Fiseo, M.P.P., 1982, Sedimentation on th7 Weddel1 ~ea eontinental margin and abyssal plain. Antarct~ea: Thes~s. Riee University, Houston, Texas, 107 ~p. ------~~~~- ._--- - - .. ;.--- ._--- .. Fossum, B. A., Maiie y , G. H., and Torsen, H. O. 1982 Marine G~o- P h YS .l cal Research i n the Weddell Sea during " the Nürwo?g i a n - An ta./·e ti ': r::e ·:.;;'ar·ch E :; ;:p.::·d i tj on e,f 1'7'705-77, i n C r' adde,,:~~ , C:., ed., Antarct i c Geosci~nce: Madison, Wisconsin, Un iversi ty ~f C·J j ':;. ': CI n ';. i n F' r i~ :. ~ , p . • ::;: '7' ;' -:.4 i:14 . •

Gi1i ~~ ~E ~·- i9 i3,-Ci ~cu1ation and bottom ·water production in the Weddel1 Sea: Deep Sea Res., V. 20, p .• 111-140.

GOdoy, E., and Podoz~o, M., 1980, Comment on " Mesozoic evolution of the Antarcti~ Pe~insula ~nd the so. Andes": Geology, v. 8, p. 2t,l-262.

Gordon, . A.L. and LaBreeque, J .. L . ~ . , 1977, Islas Oreadas Cr.uise 12: Capetown to Buenos Aires: Antaretie Jour. U.S., V. 12, p. 60-62.

Griffiths, D.H., Riddihough, R.P., Cameron, H.A.D., and Kennett, P., 1964, Geophysieal investigation .. of the Seotia Are: - British Antaretie Survey Seientifie Rept. No. 46, 43 pp. Gr i KIJ r CI I.) , G. E., 19:32, S t r' IJ I: hJ r· t? ,;)f An t ~.r·l: t i ': .~:'.n d ou tl i ne clf i t s t?1.)C)~ U ti I:)n., . i n Craddcfl:~::, C., eod., An t.",rc ti c Geoo 'sc i enl:e: ' ..1 _-' 1 __ '" ' II---r- ' LI ·· · · .. ·IJ· . r- J ! -:\ I..J "; . '_ I Ii ...... '=.' _ '_I f ':- In, n ! u,;. r· .:;, t " ),, 1-' + J. I .: C 1-' n'= I n -' r· p ,- .-- ~ ':;1 1 - '=1 C' 4 _. - ___ ._. ____ -- __ __~~ _ . _ ~ _-=- _ ~_ _~ - _. _' - _' I _ =:=' =-, ~I, ,',' !_' _' •

Harner, ~. D., and Moyco, A. 8., 1982, Cornposi tion and or i gin of oarnet from the Antarctic Peninsula Volanic Greup of Trini t y ~eninsula: Journal of the Geological Soc i ety ef Lendon,

_IJ ._-_._1 ~'"'Q .~P- __• _ ""'13i ___ : "'''11··_. ~-='''1 _. ______"____ . ______..-.- .. __

Harlan, J.G., 1981, Glacial marine sedimentation in the Weddell Sector of the East Antarctic Rise: Thesis. Rice University, Houston, Texas, 57 pp.

--- . ----~----~~--

Harringte.n, P. 1<._, 8ar~:: er, P. F., .~nd Griffiths, D. H., 1-:;'72, Crustal structure of tht? S6. Orkney Island Area from seismic r· e f r· .:.. c t j Ci n .:.. n d m.~ I;J n t? t i c rn e .:'.:. ure me rl t: 1 i n Ad i e, F' . .J., e d. ~ An t .:.. r c t i c (3 e .;) 1 I~ 'J y .~. n d Gt?--rDp h :~' ':;-i C:·: CI:. 1 0, LI ni') t? r ·s i t e t ·s f I:' r-1:0. '~ e t , p. 27-:32. -- - .. _------...... --- ...~----~ -- H~rrisQn,C . G •. A., Barron , D. J.! and Ha y , W. W., 1979, M@sozoic el.)olution of ~he 'A nt a r ctic Penfnsula and theo So. And@s: Geo T- __ . . I ...., . 1 '-1-'4 --,...,,-, UY7, .). ..., p. .:..... - .:...... ~.

• • ":;1 H~r·-~· i-son ,(: . G. A. ~ -S:;;~ ,~"n, D •.;~d ~H ay.- , I,.J ' - '/J~~ - 1't80, M@~clzcd c t"vol u t ~ ~n._Q,-f, thi'!-- Ar:H arct i c P@n i n'SlJ 1.:0. Öj.nd tl"'11~ ~; o. Arlde:-: a

repl~ y : ~ 262-263. y --_____Geo10gy,wo .• _..,... • ..,---....--_.....,. v.___ 8. ,_. ___ p., ,...... -",._...... ____ , ____ _

-'------._~- -~-----_. _.-

Haugnton, S .. H. J.-t9.~·?,. . Gt"'::fr.:,,~i caT Hi 'ster-)' ,;)f ·;.v. Afr-i I:.:": Gecd 0- gical Soc i ~ "!2' .;)_f :=" Afr·-i,:a. , .]obanne:bur·g. , _._- ',- ---.---'- -~ ~- - - Haugland, K., 1982, Sä"ismic reconD.~anc~--äurvey in the Weddell . . Sea, in C. Craddock, (ed.), Antarctic Geoscience: University Wisconsin Press, Madison, p.404-413.

Hayes, -D .-:8 .--, and-Frakes~ -- L-~ A:-;- 197S-, - General -synthesiS ot Deep , Sea Drilling Project Leg 28: in Initial Reports of Deep Sea Drilling Project, U.S. Government Printing Office, Washing­ ton, D. C., V. 28, p. 919-942.

_.. _~----~ Heirtzler, 0.R., 1971, The evolution of the southern oceans: in L.O. Quam (ed.), Research in the Antarctic: Amer. Assoc. Adv. Sci., Pub. No. 93, W~shington, D. C., p. 66.7-684. Herron, E.M., and Tucho1ke, B.E., 1976, Sea-f1oor magnetic patterns and basement structure in the southern Pacific: in C.D. Ho11ister and C. Craddock, (eds.), Initial Reports of the Deep Sea Drilling project, U.S. Governmetn Printing Office, Washington, D. C., V.35, p. 263-278.

--" ~ - - --..:....._. ----. .---,- _. --- ._------Hinz', X., and Kraus~, W., 19H2, The continenta1 margin of Queen Maud Land/Antarctica: Seismic seouences, structural elements, and geolog ica1 development': Geol. Jb., v. 23, p. ·17-41.

Hinz, K., 1983, Resu1ts of geophysica1 investigations in the Wedde11 Sea and in the Ross Sea, Antarctica:. Proc. 11th Wor1d Petro­ leum Congress, London, p. 1-13. ------=,.,-====-- .,. ------==,=~-=.-= .- -= Hol list.,.. C. 0., end Eid.,.. R. B., 1969, Contour. currents In the Weddel I 5e&: Deep-Sea Res!arch, v. ~6, p. 99-102.

Huang, T.C., and Watkins, N.D., 1977, Antarctic Bottom Water velocity: contrasts in the associated sediment record between the Brunhes andMetayame epochs in the South Pacific. Mar. Geo1ogy. V. 23, p. 113-132. ~~-··~-K~e~;;· ,~~~E~· ;.=, and Ivanov-:-V.; L 7:-i9-83~-Str~ct.~~~ - and out~ine oi - -- . geo1ogic history of the southern Wedde11 Sea Basin.: in R.L. Oliver, P.R. James and J.B. Jago (eds.), Antarctic Earth . Science, Aus.tra1ian . Academy of Science, Canberra, p. 194-196.

f< i rrr IJ r· .?, !-(., 1 q 8 2, Ge<:,: ':' 9 i C:<. 1 .~ n d (3 e 0 p h ;'--;:. i ': ." 1 S;.1j r· ',I e :; i n t t-: !? Berl tngs.h .".IJ-:.en 8.a:=. ; rt, ':Itf Ant.:o.r·cti i ca: Ant3.r·ct i c Rel:ord, . 1.). 75, p. 12-24.

------~ ...... _- -- ...... -~_.------Kleplkov. V. V. , '960, Sottom wafers of the Weddel I Sea: Sovlet AntarctTc E)(ped. I nf. Bull., v. 2, p. 227- 230. . Kurtz, D.- ;--an'd - Änderson-; --J: :a. ; - 1~79 : -' Recogni~ion and sed~mentO.log~c descriptionof recent debr~s f10w depos~ts from the Ross and Wedde11 Seas, Antarctica: Jour. Sed. Pet., V. 49,. p. 1159-1170. L·~.

La Br'ecque, ,J. ....I , .~ n d H.3. ~.. ' €' :;., Cl. E., 1'7' 7':;-, S e .a f 1 00 r s p r e a Ij i n 9 h i .:. t or ::.. ' e,f the Agu1has 8.as i n, Earth and P1anetary Sei€'nee Lettei's, ,..... 45, p.411-42:3.

La 8 r' e e q IJ e, \"T. L., a. n d ~< eIl er', tv l., 1 '? f: 2, A ge 0 p h :,.:. i e .:'.1 .:. t Ij d ::.. ' .:. f t hel nd cl-A t 1 a rr t i e :::: a.:· in. i n er."" d d 0 cl-: , C., e d ., An t ."" r ': t i e Ge c,=· ': i e n e e: M a d' iso n, 1.1.1 i ·s c on s in, LI n i ,.) er· :· i t :,..- 0 f 1,.,1 i .; ': on .:. j n F' i e: ': ' ~ p. :3;=:7-3'i6.. _" ___ _~ ..~ --- - ._. ~-.' ~ .... _----

Lau don, T. ~;., Th.':JrTi·:I:;n, t··~. P. t~., !.' .! i 1 1 i "'.rTi·::· ~ P. L., 1"1 j 1 1 i!<>? r, , K. L., Rowley, P. D .• and 8oyles. J. M., 1983, The Jurassie Lat.""d::,' F':Jr·rT!''''.tion, ·:.c,!~thv. .Ie: .ter·n A~lt .:..rcti,: Penin ·:.ul .",,: in 01 j'. .'er · , R. L., James, P. R., and Jago, J. 8., eds., Antarctic Earth . Science, Austral ian Academy of Seienee. Canberra. p. 308-314. -,--- -_. -~-- ~-"'""'-.....,---- -~. - - --~- -. ' .

Ledbetter" M. T., 1979, Fluctuations of Antarctic Bottorn Water . Velocity in the Vema Channel during the .·last 160,000 years: Marine Geology, V. 33, p. 71-89.

Ledbetter; M: T :- ana CyesJ:e.Lsj{~ ,P-.,l!' .. -, .L~ H~, .l::SOl:l:OID-Current: t:!,L·UI:U.un along a traverse in the South Atlantic sector of.. the Southern Ocean: ~arine Geology, V. 46, p. 329-341.

- "-_.- ,---~-- - ...... :...._-- ~----_._- ~ - ._.- t1o:EThinne /· , - M-. I.At., Emblo?t:on 8 .T .r r'-l " Land PI_-' 77I' , ,.1. P., '::\"7'::' F" 1 - - - - -' .,. -. .., ....:\ .", • , -- 1 7 ( 'J , . Q. I ",,_'rrr~':fft · ~t- I ·· '::- e--I,I 1- ~ '"'I "" 1-" - t I' .. ~1 r:; d I den _..:.f ,-,- r '.1. 1 -'- ':;" _I r I 0+' . 1 a d ao;;l .:" ·:.c.",,r in GeD~D"_- .·:" · , 4 p 4' C'C'_4C'''? ...,I:.n w.:..nal_ .:C.nd: -1" ;.••) ~ • _1._' ,_'.'.

--~ ---_._-~ ---_.-. -- t'-1 i 11 er, H., 19:31, Pa l .:..ozo i ·:.ch · e:-~.J -':'Id- fr· ~J- hrr;e -· ;,;zel i s.,:he Oroo;:leneo·::.en:..m pazifisch~~ Rand Gondwanas (abs. in Engl ish): Geolog i sches Rundschau, p. 70, p. 519-528.

-- - ._-_._-'-_._------Mjller, H. 1982, Geologie comparision between th~ Antaretlc Penin­

sula an d sGuthern South America in L~r~.~..Jljl_~,_,~.., f. ,-_:'., e,j . , Antarct i c Geoseience: Madison, Wiseonsin, Universi ty of t,JI·:.ecln" , n Pr·e·:.·:., p. 12:-"-1:34.

------~------~ ------_.------. ------Mi 11er, H., 1983, Correlation of oroqenies between South Amer i ca .:;..n d t h e ?m t ·::or c ': ; ;:: .=.; F' .~~ n i .:;:: IJ 1 ."'. : - - - ..1 :" h r ~ . I I '::: h ' 1'3 ,::. Co 1 0:. 9 i \" I.J n .j Fr .3. 1 .~. CI n t CI 1 c,,;. i t? ~ A td-j .~. n ,j 1 IJ n ,;" I.). 1.:6 .~S, p. 5 (I - '!' 4. (E n '~ 1. .;t. t, s. • > t··~ 0 I" ton· , I. O ,! : ';'::: 2 ~ P .:;. : e om 0 t i om be t '... Ho· o? n H t r : C Ö', :3 c,u t h Am e r i c .Ö'. ~ .:<. n dAn t .:0. r· o:t i C .:0. H, .j i m;:"1 j' c .:<. t i c" ns f (J r· t h e A n t .:<. r· ': t i c P e n i n ·su 1 .:0. , in Craddock, C., ed. , Antirctic Geoscience: Madison, Wiscons i n, Un iv ers i t y o~ Wi scons i n Press, .p. 99-106.

Nelr teIn, I. Cl., ·:..n d :::;c 1 .:.. t e r· , .J. (3., 1 '?7"~', A mode 1 t h e e 1,101 u t i on of the Ind i an Oco?an and the breakup of Gondwanaland: Journal of Geophys i eal Research , v. 84, no. 12, p. 6803-6830.

'-'kl.lda ...,. ··{"'rr· a"':..~' ; T Sat n , S., Sa~~i . T •• .and Oi~; av.. 'a, N., 1983, ~ T;~h~~~ i c~·~;:;~~~me~~ of ~he Weddel 1 · gea~ Techno1ogy ?@searc~ tent@r. Japan National Oi 1 Corporation Ro?port. 35pp.

or h e im, 0., 1';> 7 7, Pr e 1 i m i n ar ::.. r e p 0 r t 0 f t hel .? 7 6/77 Na r·t, ..1 e 9 i an Re> - search Expedition: Reprint of the Nar~k Polarinstitutt Arkok 19 76, Os10, p. 327-332.

Pankhurst, R. J., 1~82, Rb-3r geochronolQY of Graham Land, Antarc­ ticÖ'.: .JolJr n.~l l::if tho:. Geo.Tagic.:o.l g';:1Ci et:;.· l:rf Landon, '..I. 13 ·'t·~ p. 701 -71 1 .

Powe 11, C. r·1cA., )c,hn ·::.cin , E;. D., .;:.. nd '. .'o?@ ')er·:., .}. .J., 1 '?:30, Are­ vised fit · o~ East and We>st Go~dwanaland: Tectonophysics, v. 63, p. 13-2,.. - ---~-~--~

Ro? x , D. C., · ~. n d T:o.n n e r· ,. P. t..,J. G., 1 '7' 8 2, Pr· e c am b r· i an ag e f 0 r gne> i ·;::.se·;::.. :..t Cape t'ler·edi th in the F .:..l kl.:<.nd r ·;::.l.:..n.j·:;., in Craddock, C., ed., Antarctic Geoscience: Madison, Wisconsin, University of W i ~censin P~ess, p. 107-108.

. -. i I - d r· l.l ~ r - . . E' ,.-.".? F·o ·s ·:;. i bl ein te r- RI e ;'::, F.: . I/". I ~ r.': 1.;. r: ,;t CI 1 ... '=., :='. ',." .; .::4. n .. , I' . d.{ , I ., .L ~ , A- , 9 1 a e i .:<.1 Ij une:; a n d .:;. f r· ,:,m 3 I) 0 met er·:. 'AI.:<. t e r· d e p t hin t h ii l.. .J e d d e 1 1 Se a, An t .:<. r C t i c~. : Ge 0 1. ::;;.:. c. Am t? r. E: l.l I 1 ., ".!. E 1, p. 3 4 6 5 - :3 4 7:: •

------_. R0 q u e p 1 ':;), C., 1'7' 8:2 , _ Sei. ~· rn i cs t rat i 9 rap h.)' 0 f t h e e a ~. t c 0 n tin e n t .3, 1 ·shelf c.f the Wedde;1 3ea, Antar·ct i ca (Ma~.ter / s the ·:;i ·:;): Housten, Te xas, P i ce Uni versi ty. Seabrooke J M--- H· t-t - , • ., u ord, G. L., and EIder R B 1971 ;ormatfon of Antarctlc Bottom Water in the'Wedderi 2~;~. JOUI'. of Geophys. Research, v.76~ p. 2/64-

-_...... -- 3m eIl i e,. ,}. ' 1 .-,,-. 1 .-. 1 t t ~' I 7Q, \.. omp e.e arc- . rench s ) stem recognized i n G';:1 r, dt ....l. :'. r, 2. .:;. E- " i.l e n c ~ ." r. ~ t 1-, (:. Co rl t -. r· .- .. ,. ,- P - r ' n - ..l ' -. f'" 1 . , "1 -- -, • • -" .",. ~ .. _ ':! , : ; : .' ..=, . • '.:Je 0 .;:1 I;j I C .) . , ~1.:o. 9 .:<. z i n 'Ö' , " 1 1 ::? I n CI. ::, ~ . 1 ~: .;. - 1 5'7' • / '::m i t h, A. 13., .:0. n d HaI 1 d.m ~ A., 1 '7' 7 0, T h >? fit cd: t r, i? -:. C, u t h >? r i ! ': ':. iI - tin>? r: t ':;. : r···j.;. t: ure, '.... . '2 2 5 , . n o. 1, p. 1 3 -;:- - 1 4 4 •

::: IJ are z, t"·1., 1 ':='7.5, F' 1 .:0. t: e tee t ':' rt i ' '.: m Cl d elf c, r· :; 0 u t h >? j' n A n t .:0. r· ': t i c .., Pe n in':;. u 1 ·Öl. .0<, n d i t·'; r· e i ·Öl. t i on t ':' '5 ':' IJ t: h ,:;. ;. n An.j e::: t3 E' Co 1 C";) /' , -', p. '211-114. .'__ .. _. _ ,. _ _. ------.------

T an n e r', P. c 1.....1. ::::: ., 1? :=: '2, ' ~, 0::' .:' 1 O:O'~ i e e \.) Co 1 IJ t i Cl n ,:,f :::; .:0 u t. h G '2 .::' r· 9 i .:l. , i n C, .:O.ddocV., C • ., ed., An t .::O.I·C ti C Ge 0 ':·':: i enee: il::O.d i '::'Oi'l, V.I i:.,:on·::. i i"i, Un i '')i?r''5 i t/ of IN i :;:.I:c:,n·:. in F're ·§:.·:" p •. 167-17.6.

/, Tanner, P. W. G., F'anKhurst, R. J., and Hyden, G., 1982, Radio­ metrie evidenee for the age of the subduction complex in the South OrKney and South Shetland Islands, W. Antarctica: Journal of the Geological Society of London, v. 139, p. 683- ,!.90 • I ,- -,~~------p. 92-

f -. ------.. Ta r 1 i n g, D. H., 1 '7' 81 ,: MCI de-I s f ':. r·· t he fra gm e- n tat ion 0 f GCI n dl,,1 a rl - aland, in C·r·essVJe.Tl, t1. M." an·d 'v'€-lla,· P., eds., GondVJana Five: Rotterdam, A. A. 8al~~~a, p ~ 261-266,

\ Thomas, R.H. and P.H. Coslett, 1970, Bottom melting of- ice shel~ and' the mass balance of Antarctiea: Nature, ·V. 228, p. 47-49.

- Thomsön-; M--:-R.A., Pankhurst:; R-:J., andCTcirkson, · P.D.,· 1983. The Antarctie Peninsula - a LateMesozoic - Cenozoic Are: a review: in R.L. Oliver, P.R. James and J.B. Jago (eds.), Antarctic Earth Science, Australian Academy of Science, Canberra,p. 289-294.

-.-_._------_... - --- Tucholke, B.E. " and Houtz, R.E., 1976, Sed.imentary framework of . the Bellingshausen Basin from seismic profiles data: Initial Reports of the Deep Sea Drilling Project, U.S. Governtnent printing Office, Washington, D. C., V. 35, p. 197-227.

_._------Tucholke, B.E., Hollister, C.D., Weaver, F.M;, and ~ennum, ,W.R;, 1976, Continental rise and abyssal pla~n, sed~me~ta~~on ~n. the southeast Pacific Basin - Leg 35 Deep Sea Dr~ll~ng prc;>Ject: in Initial Reports of the Deep Sea Drilling project, Wash~ngton D.C., V. 35, p. 359-400. Vail, P.R., Mitchum, R.M., Jr., Thompson, S., III, 1977 Seismic stratigraphy and global changes of sea level. pa;t 4: global cycles and relative changes of sea level: in C.E. Payton (ed.), Seismic Stratigraphy - Applications to Hydro­ carbon Exploration, A.A.P.G. Mem. 26, p. 83-97.

I,.,) a t t t? r .:., D. G., 1 '~ 7 2, Ge 0 p h ::,' s i C.3. 1 In'''! I? s t i '~ .3. t i ':' n oJ f a ::;e c t i 0:0 n 0:0 f t h 'Ö'::;ou t h :::;c Co t i a. R i dge ~ in Ad i e ~ F.:. ,J. ~ e;j., An t ·?-r· c t i c 13 ... 0:0 1 c,,~ / ~. n d Ci o? 0 P h :. ': i C=:·: CI '" 1 0:0, Un i '.} '2 r =:· i t e t ::J 0 r· 1 a ,:;& t, p. 33-3 t : .

Weissel, J. K., Hayes, D. E., ·and HoE'r·r·on, E. 1'1 .,1977, Plate t oE' c t I:' nie s.:~ .. n t h e s· i ':;.: t h e d j; P ,. ·3.0: e me n t s t. e ho,1e I? n Au s 1: r ~. 1 i3. , ~'.J e 1.',1 Zealand and Antarct i ca s i nce the late Cretaceous: Marine Geo:olo:ogy, v. 25, p. 231-277.

Wright, R., 1980, Sediment gravity transport on the Weddell Sea continental margin: . Thesis, Rice University, Houston, Texas, 96 pp.

Wright, R., ~ and AndersQn, J.B., 1982., The importance of sediment gravity flow to sediment transport and sorting in .a glacial marine environmen~, Weddell Sea, Antarctica: Bull. Geol • . . Soc. Arner •. ,V. ' 93,p. 951-963.

-----~ . - Wright; R.-; Ailaerson,- J".B., -and---!"l.SCO; P.~. -, .l~UU, iJl.strl.outl.on ana association of sediment gravityflow deposits- and glacial/ glacial marine sediments around the contin~ntal margin of Antarctica: in B.F. Molnia (ed.), Glacial-Marine Sedimentation, Plenum Press, N. Y., P O. 265-300 • . ·

Zinsmeister, W. J., 1982, Review of the Upper Cretaceo:ous" - Lo:ower Te r t i .3, r· :;,' ':;. e q IJ e n ': e 0 n ::; e y m ':' IJ r· I s 1 ·3. n d, An t .:0. r c t i c .~ . : ,J 0 IJ r· n -3. 1 0 f the Geolcl gi ':3.1 ":30ci et ::.. · e,f London, v. 139, p. 77'?-785. I

I PROPOSED DRILLING SITES I

I Location: Bransfield Basin Objectives: (1) To study the Quaternary glacial history

I of the Antarctic Peninsula I (2) To study the development of this basin (3) To investigate geochemical process

(short term diagenesis and petrogenesis)

Because of their relatively high latitude position, maritime

setting, and re1atively limited drainage basins, the valley glaciers

of the Antarctic Peninsula have probably responded to climatic

fluctuations which had little effect on the East and West Antarctic

Ice Sheets. The manner in which marine sedimentation has responded

to these changes has probably been far more dramatic than the re-

sponses of abyssal sediments, hence the sedimentary re cord should

be more reliably interpreted. And lastly, sedimentation has apparently 6 -1) been quite rapid in the Bransfield Strait «~, / 10 yrs. . Land studies in the islands surrounding the Antarctic Penin-

sula have revealed a complicated glacial his tory for the region

and require better chronostratigraphic control. A major objective

in drilling the Bransfield Strait would b~ to acquire a high reso-

lution record of the glacial history of the region, and thus the

more subtle climatic history of the continent. 2

Because of its unique tectonic setting, the Bransfield Strait

provides a unique setting in which to examine sedimentation within

a rapidly evolving basin, and to confirm existing tectonic models.

Preliminary studies (Rob Dunbar) have shown that the flux of organic

carbon and silica to the basin is quite high. This coupled with

the high heat flow in the sediments provides a unique setting in

which to study early diagenesis of siliceous sediments and petro­

genesis.

Location: Western Flank of the South Orkney Plateau (4 sites)

Objective: (1) To re cover as complete a Neogene record as

possible from nearly exposed sequences on

the western flank of the Plateau. Problems

of particular interest are the Neugene

climatic record, and the origin of the

South Orkney Plateau.

Location: Northwestern Weddell Sea Continental Shelf

I (possibly several short holes) I Objective: (1) To examine the Quaternary glacial history of the region and relate it to the results I of land studies in the region. Test Birkenmajer's 1982 models, which are similar

to Denton et al., 1982, for glacial grounding

events in the region. This would be ac­

complished by drilling through basal' tills, 3

and associated unconformities and conducting

mineralogie provinance analyses of these tills,

and as~ociated glaeial marine sediments.

(2) To core outcrops in the area in an attempt

to obtain aNeogene sequenee.

Loeation: Northwestern Weddell Sea Continental Rise

Objective: To examine the deep-sea paleo-oceanographic

record, specifically that of AABW production

his tory (See text for discussion of problems

with such studies). - --- - ...... ---,.... .- ---

t

60·5 •• + ~o,. •• 110

0101277 .,01578 AIWSOE .. fLTANIN

PROPOSED DRILLING SITES John B. Anderson University o·

4S·E