24 _16

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LA-10 2A-9 ioceno

00L. Eoceneodwhg - 34Oligocene

p:qon.400021-17

—TT— 23-19

0004000

o Miocene

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.

5000

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ow

5 s00o '

Figure 1. Distribution of Cenozoic cores used to investigate the paleo-oceanographic history of the southern ocean andthe glacial history of Antarctica. Maximum ages are shown for each core.

represented by reduction in diatom numbers andglacial-marine sediments related to year-round seaice near the continent. It is possible that zones devoidof fauna are due to conditions cold enough to di-minish radiolarian productivity and to increase therate of dissolution of calcium carbonate but notcold enough to increase foraminiferal productivity toproduce a biogenic component in the sediment.

ReferencesHayes, D. E. and W. C. Pitman III. 1970. Marine geo-

physics and sea-floor spreading in the Pacific-Antarcticarea: A review. Antarctic Journal of the U.S., V(3)70-76.

Heirtzler, J . R., G. 0. Dickson, E. M. Herron, W. C. Pit-man III, and X. Le Pichon. 1968. Marine magnetic ano-malies, geomagnetic field reversals, and motions of theocean floor and continents. Journal of Geophysical Re-search, 73: 2119.

Huddlestun, P. (in press). Pleistocene paleoclimates basedon Radiolaria from subantarctic deep-sea cores.

Kennett, J . P. 1970. Pleistocene paleoclimates and fora-miniferal biostratigraphy in subantarctic deep-sea cores.Deep-Sea Research, 17: 125.

Kennett, J . P. and N. D. Watkins. 1970. Geomagneticpolarity change, volcanic maxima, and faunal extinctionin the South Pacific. Nature, 227: 930-934.

Margolis, S. V. and J . P. Kennett. (in press). Antarcticglaciation during the Tertiary recorded in subantarcticdeep-sea cores.

182

Numerical Abundance ofBenthic Taxa in Antarctic Seas

EGBERT G. DRISCOLL and RUTH ANN SWANSON

Department of GeologyWayne State University

Analysis and statistical treatment of multiple 0.6 m2grab samples taken on Eltanin Cruise 38 are nearlycomplete. Three stations have been examined. Sta-tion 7, represented by 12 grabs, is generally typicalof fine-grained clastic sediments adjacent to thecontinental slope of Antarctica. Diatom-radiolarian-sponge spicule ooze, typical of non-clastic sedimentssouth of the Antarctic Convergence, is represented bythe 10 grab samples from station 8. Foraminiferanooze is present at station 11, north of the Conver-gence; 20 grab samples were taken at this station.

The abundance per square meter of specimenslarger than 1 mm among the major taxonomic groupsat each station is listed in the table. Hydroida is anexception, the abundance being presented in centi-meters of axial skeleton.

ANTARCTIC JOURNAL

4.5844.16

2.631.800.830.83

0.410.832.360.280.130.13

1.955.964.860.96

0.960.131.38

15.965.83

3.612.36

0.700.960.701.112.212.211.250.280.410.281.950.131.801.531.25

47.86

10.3330.83

1.831.83

0.160.160.331.330.33

0.331.002.501.500.830.160.660.160.83

11.005.830.16

4.003.330.161.661.000.500.661.663.001.501.000.50

0.330.160.163.002.66

41.96

5.9143.16

2.502.330.160.080.08

0.081.663.662.832.750.837.008.755.163.000.912.160.581.16

12.755.500.080.163.663.660.081.830.331.41

1.584.331.501.161.500.160.910.080.834.834.66

59.04

Taxon Station Station Station7811

Porifera..............................Hydroida............................Anthozoa............................

Gorgonacea ................Zoantharia ......................

Actinaria....................Madreporaria ............

Turbellaria...........................Nemertina..........................Nematoda..........................Bryozoa..............................Brachiopoda......................

Inarticulata....................

Discinidae..................Articulata ........................

Sipunculida........................Mollusca............................

Pelecypoda ......................

Gastropoda....................

Pteropoda.................Other Gastropoda ......

Cephalopoda* Echiuroidea........................Polychaeta..........................Crustacea ............................

Copepoda*O ...........stracoda* Malacostraca .................

Peracarida..................Cumacea...............Tanaidacea ............

Isopoda..................Amphipoda ............

Euphausiacea*..Unknown Crustacea ......

Echinodermata ..................Ophiuroidea ...................Echinoidea ......................Holothuroidea ...............Crinoidea........................

Hemichordata....................Enteropneusta ................Pterobranchia................

Chordata............................Ascidiacea......................

Total Number of Animals(exclusive of Hydroida)

*Not included in calculation of the total number of benthic or-ganisms.

Estimates of the abundance of individual specimensper unit area at any given station commonly havelittle meaning because of the limited number of sam-ples available. It is believed that the figures listedabove represent the best available estimates of thenumerical abundance of various benthic taxa in thethree sediment types examined.

A secondary goal of the present research projectwas to estimate the quantitative abundance of inver-

tebrate skeletal elements which might contribute toa macrofossil community in deep-sea sediments. Re-sults of this project were negative. Approximately6.3 X 106 cm3 of sediment was taken in 42 grab sam-ples from the three stations discussed above. Ninechitinous cephalopod beaks and two fragile, emptypelecypod valves were separated from this sedimentin the course of animal sorting. These skeletal re-mains constitute the only potential macrofossils otherthan the large benthic Foraminifera which are abun-dantly present at station 7. It is concluded thatmacrofossils may be expected to be essentially absentfrom lithifled deep-sea sediments.

Paleomagnetic and Associated Studiesof Eltanin Deep-Sea Sedimentary Cores

N. D. WATKINS* and J . P. KENNETT*

Department of GeologyFlorida State University

Measurement of the paleomagnetism of the El-tanin deep-sea sedimentary cores has been completedthrough Cruise 39. Determination of regional sedi-mentation rates south of Australia to the AntarcticContinent is now complete.

Separation of the sand-sized fraction for exami-nation of Radiolaria and Foraminifera also yields anyvolcanic glass shards present (see cover). Micropa-leontological confirmation of the ages of magneticpolarity changes in the cores, and qualitative de-termination of the abundance of the volcanic glass-which is wind-blown--provides data pertinent to di-verse geological and geophysical hypotheses.

Fig. 1 shows that in three selected Eltanin coresfrom the western Pacific, the relative abundance ofvolcanic glass in the sand-sized fraction correlateswith two independently defined parameters.

During the Brunhes geomagnetic polarity epoch(t = 0 to 0.69 m.y.), more rapid temperature fluc-tuations relative to earlier periods, as determined byforaminiferal studies for at least one area (Fig. 1,left), correlate with a much greater volcanic ashfraction. The implication is that the rapid climaticoscillations may be due, in part, to a decrease insolar radiation at the earth's surface resulting fromvolcanic maxima which Lamb (1968) has shown tobe related to Historical climatic fluctuations. The

* Now at Graduate School of Oceanography, Narragan-sett Marine Laboratory, University of Rhode Island.

September-October 1970 183