In southern Victoria Land, the occurrences of primary radi-oactive minerals appear to be associated with large-scale, oftenconcentric, circular structures which are clearly visible in theJanuary 1986 field season when we attempted to locate theradioactive veins in relation to major structural features of thearea. The circular structures range in size from nearly 50 kilo-meters to smaller features only about 20 kilometers in diameter.Gamma-ray survey flight lines from previous years cross theouter boundaries of other circular structures at a number oflocations, and they also show increased radioactivity in theboundary zones. We believe that the genesis of the uraniumand thorium deposits is related to, and most probably contem-poraneous with, the emplacement of the large-scale circularfeatures.

This research was supported in part by National ScienceFoundation grant DPI 82-16902 and the University of Kansas.

References

Claridge, G.G.C., and I.B. Campbell. 1968. Origin of nitrate deposits.Nature,217, 428-130.

Friedmann, E.I. 1977. Microorganisms in antarctic desert rocks fromdry valleys and Dufek Massif. Antarctic Journal of tilt' U.S., 12(5), 26.

Laird, C.M. 1983. Solar particle flux and nitrate in South Pole snow. In B.McCormac, (Ed.), Weather and climate responses to solar activity varia-timis. Boulder: Colorado Associated University Press.

Miotke, F.D., and R. l-lodenberg. 1980. Salt fracturing and chemicalweathering in the Darwin Mountains and the Dry Valleys, VictoriaLand, Antarctica. Polarforschung, 50(1/2) 45-80. (In German)

Ugolini, F.C. and M.L. Jackson 1982. Weathering and mineral synthesisin antarctic soils. In C. Craddock, (Ed.), Antarctic geoscience. Madison:University of Wisconsin Press.

Zeller, E., and B.C. Parker. 1981. Nitrate ion in antarctic firn as markerfor solar activity. Geophysical Research Letters, 8, 895.

Late Neogene foraminiferal record andgeological history

inferred from Dry Valley Drilling Cores10 and 11,

Taylor Valley, Antarctica

S.E. ISHMAN and P.N. WEBB

Institute of Polar Studiesand

Departtnen t of Geology and Mineralogy0/no State UniversityColumbus, 0/lu) 43210

The Late Cenozoic history of the dry valley region of Ant-arctica has been a focus of study for many workers over the pastthree decades. Drilling projects in the region—Deep Sea Drill-ing Project (DsDP) (Hayes, Frakes et al. 1975; Leckie and Webb1983, 1985), Dry Valley Drilling Project (DvDP) (McGinnis 1981;Webb and Wrenn 1982), Ross Ice Shelf Project (risP) (Webb et al.1979), McMurdo Sound Sediment and Tectonic Study(MSSTS-1) (Webb and Harwood in preparation; Barrett 1986),and Cenozoic Investigation of the Ross Sea 2 (CIROS-2) (Barrett1985)—have contributed to gaining a better understanding ofthe Cenozoic history of the Ross Sea region. Of these projects,DVDI' drillholes 10 and 11 provide the most complete lateMiocene/early Pliocene record for this sector.

Preliminary reports on foraminifera (Wrenn 1977; Webb andWrenn 1982), stratigraphy and sedimentology (McKelvey 1975;Powell 1981), geophysics (Hicks and Bennett 1981), paleomag-netics (Elston and Bressler 1981), and diatoms (Brady 1979)indicate fjord conditions in th Late Neogene Taylor Valley. Thisnearshore environment, close to the Transantarctic Mountainsand outlets of the east antarctic ice sheet, is sensitive to glacia-tion, tectonic uplift, and glacio-eustatic fluctuations. Benthicforaminifera are reliable indicators of environmental change

(Phleger 1960; Murray 1973; Boltovskoy and Wright 1976). As-semblage fluctuations observed in the DVD1' 10 and 11 faunas arerelated to the Late Neogene tectonic and glacial history of theRoss Sea region.

Ninety-four samples from the lower parts of DVDP 10 and 11(sub-133 meters and sub-193 meters, respectively) yielded atotal of 43 genera and 88 species of foraminifera. The fauna isdominated by calcareous benthic taxa. No agglutinated formsare present and only three planktonic species occur. Diversityfor individual samples ranged from 3 to 42 species. The bio-stratigraphic zonation erected for DVDP 10 and 11 is composed offour assemblage zones (based on species present and equi-tability) (figure 1). Assemblage zones are separated by intervalzones that are barren of foraminifera.

The Troc/ioelphidieila uniforamina zone (figure 1) contains theonly planktonics recovered from DVI)P 10 and 11; Streptochiluslatuin Brönniman and Resig, Neogloboquadrina pacizyderma(Ehrenberg), and Candeina antarctica Leckie and Webb. This isthe first report of S. latum in the high latitudes. In the southwestPacific its range is restricted to the late Miocene (BrOnnimannand Resig 1971) making it valuable for dating these cores (ap-proximately 7 million years). In addition, diatom data supportthe age for this assemblage zone with the occurrence ofThalassiosira torokina and Actinocyclus ingens as well as the ab-sence of Pliocene marker species Nitzsc/iia praeinterfrigidaria andThalassiosira oestrupi. Although it has no biostratigraphic utilityhere, Candeina antarctica occurs in the T. uniforamina zone,marking its youngest occurrence (previously believed to beearly Miocene; Leckie and Webb 1985). The benthic speciesTroc/ioelphidiella uniforamina Leckie and Webb is the middle/lateMiocene representative of the late Oligocene/PlioceneTrochoelphidiella Webb lineage, a group endemic to the antarcticregion (Webb 1974; Leckie and Webb 1985). This zone repre-sents relatively deep water (600-900 meters) with bathymetricfluctuations indicated by increase in Ehrenbergina spp. abun-dances (up to 25 percent).

The Epistominella vitrea zone (figure 1) exhibits low speciesdiversity (fewer than 20 species), poor equitability, and lacksTrochoelphidiella uniforatnina Leckie and Webb and members ofthe Miliolidae. With exception of E. vitrea, Astrononion echolsi

1986 REVIEW 13

Present401

-4-sc

-500

Figure 1. Schematic presentation of ages for the lower part of DVDP10 and 11 (sub-135 meters and sub-195 meters, respectively), for-aminiferal biozonations, and foraminiferal distribution (occur-rences designated by stippled pattern).

Kennett and Globocassidulina suhglohosa (Brady) are the mostabundant taxa at 17 percent and 37 percent, respectively, in thiszone.

The Trochoelphidiella onyxi zone is recognized only in DVDP 10(figure 1). Because the assemblage is very similar to the mid- tolate-Pliocene fauna described from Wright Valley (Webb 1972,1974) and Brown Peninsula (Eggers 1979; Leckie and Webb 1979;Webb and Andreasen, (Antarctic Journal, this issue), a mid- tolate-Pliocene age has been assigned to this zone. The faunaldistinction of this zone is the occurrence of Trochoelphidiella onxyiWebb.

The Trifarina spp. zone (figure 1) occurs only in DVDP 11. Fourspecies have their first appearance in this zone; Trifarina earlandi(Parr), Trifarina pauperata (Heron-Allen and Earland), Stainforthiaconcava (Hoglund), Gyroidina subplanulata Echols, and Oolina aff

0. melo d'Orbigny. These species compose up to 50 percent ofthe assemblage. Assemblages of this zone are also characterizedby a pronounced increase in species test size. Greatest diversityoccurs in this zone (44 species), although many of these are rareoccurrences of Nodosariidae. This zone represents relativelyshallower conditions (100-500 meters) than interpreted for theunderlying zones.

Separation of assemblage zones by interval zones points tofluctuating marine paleoenvironmental conditions throughoutthe successions. These changing conditions are produced byglacial oscillations within the fjord basin. Sedimentology anddiatom distribution suggest a contrasting environment for DVDP

10 and 11, based on their proximity to the grounding line of theLate Neogene Taylor Glacier. DVDP 11 represents a nearshorefacies proximal to a grounding line as suggested by the occur-rence of massive diamictites and poor distribution of diatoms.Conversely, DVDP 10 represents a more marine facies, locatedfurther from the grounding line, and characterized by variedlithologies and higher occurrence of marine diatoms. Diatomdistribution in DVDP 10 and 11 also serves as a sea-ice indicator,absence often indicating thick and semipermanent ice-cover.Interval zones, sedimentology, foraminiferal assemblage

Palsopositlon (—GM.)400

S.). 0

-400- .vD. II

-BOB-

-1200

Uplift Nate.DVDP 11

ir

5.05.04.03.03.01.00V..,. (N.)

Figure 2. (Upper) Cartoon depicting paleoposition of DVDP site 11with respect to its present position; (Lower) calculated uplift ratesshowing high- and low-end values (stippled area) and the sporadicuplift values (geniculate line) interpreted from foraminiferalbathymetric data. ("Ma" denotes "million years ago:' "m" denotes"meter.")

ISIIUS.i-L...) (.)

-leo

-I..

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14 AN1ARCTIC JOURNAl.

zones, and distribution of diatoms indicate a series of environ-mental cycles up-core in DVDP 10 and 11. These cycles reflect thefaunal and floral sensitivity to subtle environmental fluctua-tions (figure 1).

Paleoenvironmental conditions recognized in DVDP 10 and 11indicate a major overall shallowing trend in the early Pliocene,overprinted by late Miocene/Pliocene glacio-eustatic fluctua-tions. The tectonic history of the dry valley region involves aperiod of uplift from the late Jurassic. Uplift for the past 55million years (Cenozoic) is calculated at approximately 100meters per million years (Fitzgerald and Gleadow 1985) basedon apatite fission-track techniques. Paleodepths of Taylor fjordindicated by Miocene/Pliocene benthic foraminifera and sedi-ments suggest an uplift rate of approximately 87 meters permillion years (Ishman 1985) with respect to present sea-level(figure 2). Bathymetric stability indicated in the lowermostTrochoelphidieila uniforamina zone (figure 1), and distinctbathymetric shallowing initiated with the Epistominelia vitreazone and continuing through the Trifarina spp. zone, provideevidence for the onset of rapid uplift in the early Pliocene.Environmental cycles observed throughout the late Miocenesuccession of DVDP 10 and 11 represent regional eustatic eventsrelated to oscillations in the east antarctic ice sheet outletglaciers penetrating the dry valleys.

This work was supported in part by National Science Founda-tion grant DFP 82-14174.

References

Barrett, P.J. 1985. Plio-Pleistocene glacial sequence cored at CIROS 2,Ferrar Fjord, Western McMurdo Sound. New Zealand Antarctic Record,6(2), 8-19.

Barrett, P.J. (Ed.) 1986. Antarctic Cenozoic history from the MSSTS-1 dril-Ihole, McMurdo Sound. (New Zealand Department of Scientific andIndustrial Research, Wellington: Department of Scientific and Indus-trial Research Bulletin.)

Boltovskoy, E., and R. Wright. 1976. Recent foraminifera. The Hague: Dr.W. Junk b.v. Publishers.

Brady, H.T. 1979. The dating and interpretation of diatom zones in DryValley Drilling Project Holes 10 and 11 Taylor Valley, South VictoriaLand, Antarctica. In T. Nagata (Ed.), Memoirs of National Institute ofPolar Research, Vol. 13. Tokyo: National Institute of Polar Research.

Bronnimann, P., and J. Resig. 1971. A Neogene Globigerinacean bio-chronologic time-scale of the southwestern Pacific. In E. L. Winterer etal. (Eds.), Initial Reports of the Deep Sea Drilling Project, Vol. 7. Wash-ington, D.C.: U.S. Government Printing Office.

Eggers, A.J. 1979. Scallop Hill Formation, Brown Peninsula, McMurdoSound, Antarctica. New Zealand Journal of Geology and Geophysics,22(3), 353-361.

Elston, D.P., and S.L. Bressler. 1981. Magnetic stratigraphy of DVDI'Drill Cores and Late Cenozoic history of Taylor Valley, TransantarcticMountains, Antarctica. In L.D. McGinnis (Ed.), Dry Valley DrillingProject, Vol. 33. Washington, D.C.: American Geophysical Union.

Fitzgerald, P.G., and A.J.W. Gleadow. 1985. Uplift history of the Trans-antarctic Mountains, Victoria Land Antarctica. (Abstract) Workshop onCenozoic Geology of the Southern High Latitudes, 1, 16.

Hayes, D.E., Frakes, L.A., et al. 1975. Initial Reports of the Deep SeaDrilling Project, Vol. 28. Washington, D.C.: U.S. Government PrintingOffice.

Hicks, SR., and D.J. Bennett. 1981. Gravity models of the lower TaylorValley, Antarctica. New Zealand Journal of Geology and Geophysics, 24,555-562.

Ishman, S.E. 1985. Foraminiferal hiostratigraphy and paleoecology of DryValley Drilling Cores 10 and 11, Taylor Valley, Antarctica. (Masters thesis,Ohio State University, Columbus, Ohio.)

Leckie, R.M., and P.N. Webb. 1979. The Scallop Hill Formation andassociated Pliocene marine deposits of southern McMurdo Sound.Antarctic Journal of the U.S., 14(5), 54-56.

Leckie, R.M., and P.N. Webb. 1983. Late Oligocene and early Neogeneforaminifers of Deep Sea Drilling Project Site 270 Ross Sea, Ant-arctica. Geology, 11, 578-582.

Leckie, R.M., and P.N. Webb. 1985. Late Paleogene and early Neogeneforaminifers of Deep Sea Drilling Project Site 270 Ross Sea, Ant-arctica. In J.P. Kennett, C.C. von der Borch, et al. (Eds.), Initial Reportsof the Deep Sea Drilling Project, Vol. 90. Washington, D.C.: U.S. Gov-ernment Printing Office, 1093-1119.

McGinnis, L.D. 1981. Dry Valley Drilling Project. Antarctic ResearchSeries, Vol. 33. Washington, D.C.: American Geophysical Union.

McKelvey, B.C. 1975. Preliminary site reports DVDI' Sites 10 and 11,Taylor Valley. Dry Valley Drilling Project Bulletin, 5, 16-60.

Murray, J.W. 1973. Distribution and ecology of living hent/iic foraminifera.New York: Crane, Russak and Company, Inc.

Phleger, F.B. 1960. Ecology and distribution of Recent foraniinifera. Bal-timore: Johns Hopkins Press.

Powell, R.D. 1981. Sedimentation conditions in Taylor Valley, Ant-arctica, inferred from textural analysis of DVDP cores. In L.D. McGin-nis (Ed.), Dry Valley Drilling Project, Vol. 33. Washington, D.C.: Amer-ican Geophysical Union.

Webb, P.N. 1972. Wright Fjord, Pliocene marine invasion of an antarcticdry valley. Antarctic Journal of the U.S., 7(5), 225-234.

Webb, P.N. 1974. Micropaleontology, paleoecology and correlation ofthe Pecten Gravels, Wright Valley, Antarctica, and description ofTrochoelphidiella onxyi, n. gen., n. sp. Journal of Foraminiferal Research, 4,184-199.

Webb, P.N., T.E. Ronan, J.H. Lipps, and T.E. Delaca. 1979. Mioceneglaciomarine sediments from beneath southern Ross Ice Shelf, Ant-arctica. Science, 203, 43537.

Webb, P.N., and J.H. Wrenn. 1982. Upper Cenozoic micropaleontologyand biostratigraphy of Eastern Taylor Valley, Antarctica. In C. Crad-dock (Ed.), Antarctic geoscience. Madison: University of WisconsinPress.

Webb, P.N. and J.E. Andreasen. 1986. Potassium/argon dating of vol-canic material associated with the Pliocene Pecten Conglomerate(Cockburn Island) and Scallop Hill Formation (McMurdo Sound).Antarctic Journal of the U.S., 21(5).

Webb, P. N., and D. H. Harwood. In preparation. Relationships betweenseismic (sonic) velocity, lithostratigraphy, grain size distribution, bio-stratigraphy and paleobathymetry in the upper Oligocene glacigenesediments of MSST-1 Drillhole, McMurdo Sound.

Wrenn, J.H. 1977. Cenozoic subsurface micropaleontology and geology ofEastern Taylor Valley, Antarctica. DeKalb, Illinois: Northern IllinoisUniversity.

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