References

Cochran, J . K. 1973. Sedimentation rate patterns andradium-226 geochemistry of pelagic sediments from theTasman Basin. Tallahassee, Sedimentological ResearchLaboratory, Department of Geology, The Florida StateUniversity. Contribution, 39. 181p.

Cochran, J . K., and J . K. Osmond. in press. Gamma spec-trometry of deep-sea cores: sediment accumulation rates.Deep-Sea Research.

Gartner, S. 1972. Late Pleistocene calcareous nannofossils inthe Caribbean and their interoceanic correlation. Palaeo-geography, Palaeoclirnatology, Palaeoecology, 12: 169-191.

Gartner, S. 1973. Absolute chronology of the Late Neogenecalcareous nannofossil succession in the equatorial Pacific.Geological Society of America Bulletin, 84: 2021-2034.

Geitzenauer, K. R. 1969. The Pleistocene calcareous nanno-plankton of the subantarctic Pacific Ocean. Tallahassee,Sedimentological Research Laboratory, Department ofGeology, The Florida State University. Contribution, 32.llp.

Geitzenauer, K. R. 1968. The Pleistocene calcareous nanno-plankton of the subantarctic Pacific Ocean. Deep-Sea Re-search, 19: 45-60.

Hays, J . D. 1965. Radiolaria and late Tertiary and Quater-nary history of antarctic seas. Antarctic Research Series,5: 125-134.

Kennett, J . P. 1970. Pleistocene paleoclimates and foramini-feral biostratigraphy in subantarctic deep-sea cores. Deep-Sea Research, 17: 125-140.

Leoblich, A. R., and H. Tappan. 1970. Annotated index andbibliography of the calcareous nannoplankton V. Phycol-ogia, 9(2): 157-174.

Opdyke, N. D. 1972. Paleomagnetism of deep sea cores. Re-views of Geophysics and Space Physics, 10(1): 213-249.

Osmond, J . K., and L. D. Pollard. 1967. Sedimentation ratedetermination in deep sea cores by gamma-ray spectrome-try. Earth and Planetary Science Letters, 3: 476-480.

Rona, E., and C. Emiliani. 1969. Absolute dating of Carib-bean cores P6304-8 and P6304-9. Science, 163: 66-68.

Scott, M. R., J . K. Osmond, and J . K. Cochran. 1972. Sedi-mentation rates and sediment chemistry in the south IndianBasin. Antarctic Research Series, 19: 317-334.

Surface ultrastructurcil variation in thepolar planktonic foraminifer

Neogloboquadrina pachyderma(Ehrenberg)

J. P. KENNETT and M. S. SRINIVASANGraduate School of Oceanography

University of Rhode IslandKingston, Rhode Island 02881

The Late Miocene to Recent planktonic foraminiferNeogloboquadrina pachyderma (Ehrenberg) has beenstudied intensively over the past decade mainly be-cause of its value as a paleoclimaticpaleoceanographictool resulting from its importance in the cooler watermasses in both hemispheres and because of its distinctcoiling direction patterns (Bandy, 1967, 1972;Jenkins, 1967; Ingle, 1967; Kennett, 1967). Thisspecies, which is the only planktonic foraminiferalspecies occurring in true polar waters, occurs as farnorth as about 25°S. in the Southern Hemisphere andas far south as about 25°N. in the Northern Hemi-sphere.

We utilized scanning electron microscopy (sEM)to examine the range of variation in surface ultra-structure in over 1 5000 specimens of N. pachydermafrom different water masses and from different inter-vals of time during the Late Cenozoic. We studiedthe ancestry, evolution, and environmental relationsof the species, and its phylogenetic relationships withthe N. dutertrei plexus and N. acostaensis during theLate Cenozoic (Srinivasan and Kennett, 1974, inpress; Kennett and Srinivasan, in press). The appli-cation of SEM ultrastructural studies to planktonicforaminifera enables greater precision in taxonomy

September-October 1974

because it assists in differentiating between phylo-genetic and phenotypic variations (Srinivasan andKennett, 1974).

Two main ultrastructural types are recognizedreadily: reticulate forms (fig. 1, 1,m) with relativelyunthickened, pitted, microcrystalline surface and morethickened crystalline forms (fig. 1, k, n) with testcovered by distinct euhedral calcite rhombs. Inter-mediate forms link these two types. Reticulate formspredominate in subantarctic (fig. 1, c, e, f) and arctic(fig. 1, i) populations while crystalline ultrastructureis dominant in antarctic (fig. 1, a, b, d, j) and sub-tropical (fig. 1, g) populations. In subtropical popula-tions crystalline forms are distinguished from those ofhigh latitudes by thinner walls, higher pore concen-tration, and a lack of rosette patterned crusts.

These ultrastructural differences reflect a differencein the nature of secondary calcification with reticulatemicrocrystalline ultrastructure representing an earlierstage. Differences in dominance of the ultrastructuraltypes presumably reflects environmental differencesassociated with the various water masses. Overallsimilarity in ulttrastructure within N. pachydermalinks subtropical populations with temperate popula-tions from the Late Miocene to the Recent as onephylogenetitc species that evolved from Globorotaliacontinuosa in the late Middle Miocene to early LateMiocene. It was discovered that changes in the char-acter of secondary calcification on the test surface ofRecent N. pachyderma are related to water masschange. This discovery prompted us to test whethersuch a relationship could be utilized as a paleoceano-graphic or paleoclimatic index. As a result, variationin surface ultrastructure has been examined by SEMof 23 N. pachyderma populations from the LateMiocene to the Holocene or latest Pleistocene at Deep

263

Fi j ure 1. A to N: Neo-gIboquadrina pachyderma(Ehrenberg). A, B, G, and J:Crystalline forms. A: Obliqueventral view (core E474,6407'.10"S.80023'.89"E.,3,598 meters, x240). B:Oblique ventral view (coreE36-14, 58 0 05'S. 150614'E.,2,637 meters, x324). Gt Ven-tral view (NZOIE core 120,43 0 00'S. 175 0 30'W., 812 me-ters, x210). J: Ventral viewshowing small umbilical aper-ture and distinct aperturerim (E32-8, 73°58.0'S. 176007.0'E., 580 meters, x77). Cto F, H, and I: Reticulateforms. C: Oblique ventralview (E15-16, 56 0 03'S. 119055'W., 3,039 meters, c240).D: Ventral view (E124, 60003'S. 140 0 53'W., 3,614 me-ters, x260). E: Ventral view(same location as C, p210).F: Side view, note hightrochospiral nature of the test(same location as C, 058).H: Ventral view (DSDP leg 29,site 284, 40 0 30.48'S. 167040.81'E., 1,068 meters, x273).I: Ventral view (298A, 84°22'N. 169 0 48'E., 3,175 meters,x260). K: Enlarged view ofthe second chamber from theearliest in the last whorl ofa dextral form (location sameas G, x2,100). L: Surface offinal chamber of sinistralform (location same as E,x2,020). M: Surface of finalchamber of dextral form (lo-cation same as H, x2,500). N:Surface of penultimate cham-ber of sinistral form (location

some as H, x2,000).

Sea Drilling Project site 284 in the cool subtropicalwater mass of the South Pacific (Srinivasan andKennett, in press). Fifty specimens were examined ineach sample, allowing quantitative analysis of thetrends.

Oscillations in the ratio of reticulate to crystallineultrastructure in populations of N. pachyderma (fig.2) closely coincide with substantial fluctuations, re-corded by Kennett and Vella (in press), in surficialCenozoic water masses. Reticulate forms are dominantduring warm water episodes; crystalline forms aredominant during cooler water episodes. Variation inultrastructure within N. pachyderma thus is a valu-able tool for Late Cenozoic paleoceanographic analy-sis and also may be applicable within other forms ofplanktonic foraminifera. Particularly severe climaticcool episodes are shown by this method to haveoccurred during the latest Miocene, during the Late

Pliocene, and during the Pleistocene, thus supportingprevious interpretations based on planktonic foramini-fera.

This research was supported by National ScienceFoundation grant GA-35252.

References

Bandy, 0. L. 1967. Foraminiferal definition of the bound-aries of the Pleistocene in Southern California, U.S.A. In:Progress in Oceanography (Sears, M., editor), 4: 27-49(figs. 1-7). New York, Pergamon.

Bandy, 0. L. 1972. Origin and development of Globorotalia(Turborotalia) pachyderma (Ehrenberg). Micropaleontol-ogy, 18(3): 294-318 (plates 1-8).

Ingle, J . C., Jr. 1967. Foraminiferal biofacies variation andthe Miocene-Pliocene boundary in Southern California.Bulletin of American Paleontology, 52: 236.

264 ANTARCTIC JOURNAL

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Figure 2. Percent fluctuations of Neogloboquadrina pachyderma(solid line) and percent fluctuations in reticulate ultrastructuralforms (dashed) of N. pachyderma in the Late Miocene to Pleisto-cene sequence corded at DSDP site 284 (temperate South Pacific).High frequencies of Al. pachyderma represent cool intervals; lowfrequencies represent warm intervals. Characteristics of secondarycalcification determined by examination of 50 specimens in eachsaàple (shown at right) using a scanning electron microscope.Note generally reciprocal relations between the two parameters.N.Z. Late Cenozoic stages are shown at right and Pleistocene dis-

conformity is near the top of the sequence.

Jenkins, D. G. 1967. Recent distribution, origin, and coilingratio changes in Globigerina. pachyderma (Ehrenberg).Micropaleontology, 13(2) : 195.

Kennett, J . P. 1967. Paleo-oceanographic aspects of theforaminiferal zonation in the Upper Miocene-Lower Plio-cene of New Zealand. Bologna, Committee on Neogene,4th International Congress. Giornale di Geologia, 2(35)143.

Kennett, J . P., and M. S. Srinivasan. In press. Surface ultra-structural variation in Neogloboquadrina pachyderma(Ehrenberg): phenotypic variation and phylogeny in theLate Cenozoic. In: 0. L. Bandy Memorial Volume (Kol-pack, R., and D. Gorsline, editors).

Kennett, J . P., and P. Vella. In press. Late Cenozoic plank-tonic foraminifera and paleoceanography at DSDP site 284in the cool subtropical South Pacific. In: Initial Reportsof the Deep-Sea Drilling Project (Kennett, J . P., et al.),29. Washington, D.C., U.S. Government Printing Office.

Srinivasan, M. S., and J . P. Kennett. 1974. SEM ultrastruc-tural variation in planktonic foraminifera: value in evolu-tionary and phenotypic studies. American Association ofPetroleum Geologists Bulletin, 1: 86 (abstract).

Srinivasan, M. S., and J . P. Kennett. In press. Evolution andphenotypic variation in the Late Cenozoic Neoglobo quad-rina dutertrei plexus. In: Professor Asano CommemorationVolume (Takayanagi, Y., and T. Saito, editors). NewYork, Micropaleontology Press.

Srinivasan, M. S., and J . P. Kennett. In press. Secondarycalcification of the planktonic foraminifer Neoglobo quad-rini pachyderma as a climatic index. Science.

Late Eocene temperatures indicated bysilicoflagellates from the Oamaru

diatomite, New Zealand

YORK T. MANDRA*California Academy of Sciences

andSan Francisco State University

A. L. BRIGGERCalifornia Academy of Sciences

HIGH00HI MANDRA*

This paper reports the results of analyses of newdata in our continuing studies of Late Eocenesouthern ocean water temperatures (Mandra et al.,1969, 1973c), silicoflagellates as indicators of paleo-temperatures (Mandra, 1958; Mandra et al., 1972),and Late Eocene silicoflagellates from the Bain's andTotara localities of the Oamaru diatomite of NewZealand (Mandra et al., 1971a, 1973a).

Hornibrook (1971) reviews the evidence for NewZealand Tertiary climates as published by the closeof 1969. Fig. 1 summarizes the portion of his con-clusions that relates to our present study. He reportsthat marine water temperatures, based on oxygenisotope studies, during the Runangan stage (ArnoldSeries, Late Eocene) at 41°S. in New Zealand wereapproximately 22°C. For the same time and place

* Mailing address: 8 Bucareli Drive, San Francisco, Cali-fornia 94132. This is contribution 54, Biogeology Clean Lab-oratory, University of California, Santa Barbara.

September-October 1974 265