Initial Reports of the Deep Sea Drilling Project, Vol. 71. Washington,D.C.: U.S. Government Printing Office.

Ciesielski, P.F., M.T. Ledbetter, and B.B. Ellwood. 1982. The develop-ment of Antarctic glaciation and the Neogene paleoenvironment ofthe Maurice Ewing Bank. Marine Geology, 46, 1-51.

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Plafker, G., S. Bartsch-Winkler, and A.T. Ovenshine. 1977. Paleoglacial

implications of coarse detritus in DSDP Leg 36 cores. In P.F. Barker,I.W.D. Daiziel etal., Initial Reports of the Deep Sea Drilling Project, Vol.36. Washington, D.C.: U.S. Government Printing Office.

Rabinowitz, P.D., M. Delach, M. Truchan, and A. Lonardi. 1978.Bathymetry Chart Argentine Continental Margin. AAPG ArgentineMap Series.

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Paleoclimatological indices in thesouthern ocean based on

morphological parameters in theradiolarian genus Antarctissa

A. GRANLUND

Department of GeologyStockholm University

S-106 91 Stockholm, Sweden

Relationships between radiolarian assemblages and climaticparameters have been noted by many workers (Hays 1965;Keany 1973; Lozano and Hays 1976). Such relationships havebeen used for establishing paleoclimatologic equations (transferfunctions) (Williams and Keany 1977). In this study, the mor-phology of the radiolarian genus Antarctissa (A. denticulata—A.strelkovi complex) is analyzed in relation to physical parameters.The Antarctissa complex is very abundant in the southern ocean;it is one of the most common representatives of the Antarcticradiolarian fauna (Hays 1965; Nigrini 1967; Petrushevskaya1967; Keany 1973; Lozano and Hays 1976; Williams and Keany1977). This group is, therefore, suitable for a morphometricstudy.

The study area is a latitudinal transect from the southernIndian Ocean sector of the southern ocean (45°S to 65°S). A pilotstudy of five core-top samples from each of the South AtlanticOcean, South Pacific Ocean, and southern Indian Oceanshowed that morphologic gradients do not differ among theseoceans. Since more core-top material is available from thesouthern Indian Ocean, this ocean was chosen to represent thesouthern ocean.

Initially, 50 core-top samples were selected for this study.Only those 21 samples that contained more than 100 specimensof Antarctissa per gram sediment were included. These samplesare from an area between 45°S and 65°S. The remaining 29samples mainly came from the north of 45°S.

To determine whether the core-tops are Recent, counts weremade of the relative abundances of Cycladophora davisiania. Innone of the samples, C. davisiana exceeded 5 percent. Thus,they reflect Recent conditions (Lozano and Hays 1976). Theabsence of Stylatractus universus in all samples indicated thatthey are not older than 400,000 years (Hays and Shackleton1976). The greater than 60-micrometer fraction was used for themorphologic study. The samples were prepared using an im-proved version of Moore's (1973) settling technique (Granlund1983), which provides 32 slides with equally distributed radi-olarian faunas from each sample. For the measurements, 10slides, containing about 100 specimens, were randomly se-lected from each sample.

Seven morphological characters were measured on eachspecimen (cephalis width, contour width, thorax width, length

Correlation coefficients for two morphological parameters versus some physical parameters for the South Indian Ocean transect In thesouthern ocean

Physical parametersMorphological SilicaPhosphate .Oxygenparameters TemperatureTemperatureTemperature(micromoles(micromole (microlitersA° Bb Cc

per liter)per liter) per liter)

—0.200

—0.153

Width of cephalis(in micrometers)(Vi) _0.662d

Width of thorax(in micrometers)(V2) 0.715'

_0.631e_0.685d

0.696'_0.723d

0.223_0.695d0.6430

0.309- 0.5320.487

a Annual average temperature, °Cb Winter temperature, °C

Summer temperature, °Cd Denotes significance at the 0.1 percent level.

Denotes significance at the 1.0 percent level.Denotes significance at the 5.0 percent level.

96 ANTARCTIC JOURNAL

Width of cephalis and width of thorax compared to annual average surface-water temperature.

to maximum width of cephalis, length of cephalis, length tomaximum width of thorax, and total length). The measure-ments were carried out using a microcomputer-based measur-ing device. This system permits very rapid acquisition of mor-phologic data. In total more than 7,000 measurements weremade.

Several physical parameters (silica, phosphate, dissolvedoxygen, salinity, summer surface-water temperature, wintersurface-water temperature, annual average surface-water tem-perature, water-depth, average number of Antarctissa per gramsediment, and latitude) (Reid 1981) were compared with thesemorphological dimensions to determine possible relationships.

Analyses revealed close correlations between surface-watertemperature and the morphological parameters. The width ofthe cephalis and the width of the thorax showed the highestcorrelation with annual average surface-water temperature (ta-ble) and are used to illustrate morphological gradients (figure).The width of the thorax ranges between 90 micrometers attemperatures of about 0°C and 60 micrometers at 8°C. Similarly,the width of the cephalis ranges between 55 urn at temperaturesof about 0°C and 40 micrometers at 8°C.

The correlationship between temperature and morphologicalparameters thus determined is potentially useful for paleo-climatological studies in the southern ocean. This may be es-pecially so in antarctic waters, where calcareous organisms(planktonic foraminifera and coccoliths), which are widely usedfor palecimatic analyses, are rare.

I thank Dennis Cassidy (Florida State University) who gener-ously provided the core-top samples used in this study; BjörnMalmgren (Stockholm University) who gave valuable com-ments and suggestions on the manuscript; and Otto Hermelin(Stockholm University) who helped me with the figures.

ReferencesGranlund, A. 1983. An approach to a statistically random settling tech-

nique for micropaleontology. Stockholm Contributions in Geology.Hays, J.D. 1965. Radiolaria and late Tertiary and Quaternary history of

antarctic seas. Biology of the antarctic sea, II: Antarctic Research Series.Washington, D.C.: American Geophysical Union.

Hays, J.D., J.A. Lozano, N.J. Shackleton, and G. Irving. 1976. An 18,000B.P. reconstruction of the Atlantic and Western Indian Ocean sectorsof the antarctic ocean. In R.M. Cline and J.D. Hays (Eds.), Investiga-tions of Late Quaternary paleoceanography and paleoclimatology. Geo-logical Society of America Memoir, 145.

Hays, J. D., and N.J. Shackleton. 1976. Globally synchronous extinctionsof the radiolarian Stylatractus universus. Geology, 4, 649-652.

Keany, J. 1973. New radiolarian paleoclimatic index in the Plio-Pleistocene of the southern ocean. Nature, 246, 139-141.

Lozano, J.A., and J.D. Hays. 1976. Relationship of radiolarian as-semblages to sediment types and physical oceanography in Atlanticand Western Indian Ocean sectors of the antarctic ocean. In R.M.Cline, and J. D. Hays, Investigations of Late Quaternary paleoceanographyand paleoclimatology. Geological Society of America Memoir, 145.

Moore, T. C., Jr. 1973. Method of randomly distributing grains for micro-scopic examination. Journal Sedimentary Petrology, 43, 904-906.

Nigrini, C. 1967. Radiolana in pelagic sediments from the Indian andAtlantic Oceans. Scripps Institution of Oceanography Bulletin, 11, 1-125.

Petrushevskaya, M. C. 1967. Radiolyarii otryadov SpumellariaiNasselaria antarkticheskoi ovlasti (po materiallam Sovietskoi ant-arkticheskoi ekspeditsii). [Antarctic spummeline and nasseline radi-olarians (in collections of the Soviet Antarctic Expedition)]. In E.N.Pavlovskii (Ed.) Issl. Fauny Morei, Nau Ka Lenningrad, 3, 3-186.

Reid, J. L. 1981. On the mid-depth circulation of the world ocean. In B.A.Warren and C. Wunsch (Eds.) Evolution of Physical Oceanography.London: MIT Press.

Williams, DR and J. Keany. 1977. Comparison of radiolarian/planktonicforaminiferal paleoceanography of the subantarctic Indian Ocean.Quaternary Research.

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