Sedimentology of the Robertson - Amazon S3...Sedimentology of the Robertson Bay Group, northern Victoria Land, Antarctica THOMAS 0. WRIGHT Department of Geology Allegheny College Meadville,

GONDWANALANDMBLIES

After Smith and Hallam (1970)

A

After Veevers. Jones, Talent (1971)

C

AfterThree possible reassemblies for Gondwanaland.

References

Curray, J . R., and Moore, D. G. 1974. Sedimentary and tectonicprocesses in the Bengal deep-sea fan and geosynclines. In C. A.Burke and C. L. Drake (Eds.), The geology of continental margins.New York: Springer-Verlag.

Harrington, J. H. In press. Reconstruction of the Australian sectorof Gondwanaland from Cambrian to Early Tertiary. Inter-national Union of Geological Sciences Subcommission onGondwana Stratigraphy and Paleontology: Abstracts. In M.M.Cresswell and P. Vella (Eds.), Gondwana V. Rotterdam: A. A.Balkema.

Scotese, C. R., Bambach, R. K., Barton, C., van Der Voo, R., andZiegler, A. F. 1979. Paleozoic base maps. Journal of Geology, 87,217-277.

Shen, Y. B. 1978. Leaiid conchostracans from the Middle Devonianof South China, with notes on their origin, classification andevolution. In Papers for the International Symposium on theDevonian System 1978. Nanking: Nanking Institute of Geologyand Paleontonolgy, Academia Sinica.

Tasch, P. In press. Nonmarine evidence for Paleozoic-MesozoicGondwana correlations: Update. International Union of Geolog-ical Sciences Subcommission on Gondwana Stratigraphy andPaleontology: Abstracts. In M. M. Cresswell and P. Vella (Eds.),Gondwana V. Rotterdam: A. A. Balkema.

Tasch, P. and Jones, P. J . 1979. Carboniferous, Permian, and Triassicconchostracans of Australia—Three new studies. Bureau of Min-eral Resources, Geology and Geophysics, Bulletin 185: 47 pp.

Tasch, P. and Sastry, M. V. A., Shah, S. C., Rao, B. R. J., Rao, C. N.,and Ghosh, S. C. 1975. Estheriids of the Indian Gondwanas:Significance for continental fit. In K. S. Campbell (Ed.),Gondwana Geology, Papers presented at the Third Gondwana Sym-posium, 1978. Canberra, Australia: Australian National Univer-sity Press.

Sedimentology of the RobertsonBay Group, northern Victoria

Land, Antarctica

THOMAS 0. WRIGHT

Department of GeologyAllegheny College

Meadville, Pennsylvania 16335

This study is part of the German Antarctic NorthernVictoria Land Expedition (GAN0vEx-79) to northern Victo-ria Land, Antarctica, sponsored by the West Germanbundesanstalt für Geowissenschaften und Rohstoffe (BGR)

organized by Franz Tessensohn. I was invited to participatein this project as an exchange scientist. The expedition pro-

ceeded by ship (the Schepelsturm) from New Zealand toCape Adare, Antarctica, and began study of the RobertsonBay area on 12 December 1979. We used two Hughes 500Dhelicopters and an S58 Sikorski for logistics. A storm inter-rupted the study and necessitated a detour to McMurdoSound just before Christmas to repair two damaged heli-copters and evacuate an injured crewman. Work resumedin the Robertson Bay Group 3 January 1980. We proceededwithout further incident on all major groups of rocks ex-posed from Cape Adare to the U.S. Antarctic Research Pro-gram (USARP) Mountains. The ship changed positionalong the coast to provide the best support to field camps.A permanent prefabricated hut was erected near the junc-tion of the Lillie and Ebbe Glaciers. The last field camp wasevacuated by 20 February and the ship returned to NewZealand 25 February. All major goals of the expedition weremet, demonstrating that a ship- and helicopter-supportedgeological field study is feasible.

We studied the Robertson Bay Group (generally exposedeast of the Leap Year Glacier) near Robertson Bay, at Mt.

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Mulach, in the Mirabito, Everett, and Morozumi Rangesand a number of other places (figure 1). Other investigatorshave been Rastall and Priestley (1921), Sturm and Carryer(1970), Le Couteur and Leitch (1964), Harrington, Wood,McKellar, and Lensen (1967), and Crowder (1968).

The rocks of the group are remarkably similar through-out the area studied. They consist of folded and cleavedsandstones and shales that have not been metamorphosedbeyond possible very low-grade greenschist stage, exceptwhere in contact with younger intrusives. In all cases stud-ied, we gathered abundant sedimentological evidence indi-cating this entire group consists of alternating turbiditedeposits and pelagic shale. Turbidite thickness ranged froma few centimeters to more than a meter. Graded beds, oftenwith Bouma Tad sequences (a sequence of sedimentary

features commonly found in turbidites) were common. Inaddition, amalgamated beds in coarse units were present, aswere thick intervals of finer-grained material. Generally,the group consisted of a considerable thickness of laterally.persistent alternating beds of ½-meter thick turbidites andintervening silty shale beds of similar average thickness;these beds closely resemble the outer fan turbidite associa-tion of Mutti and Ricci Lucchi (1972).

Lack of biostratigraphically useful fossils and discon-tinuous outcrop precluded the establishment of a completestratigraphic column. The group is at least 2,000 metersthick and may be much thicker. The age is reported asPrecambrian by most workers, but it must be latest Pre-cambrian based on metazoan trace fossils (worm burrowsand feeding trails) found in a number of localities. Younger

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Figure 1. Sketch map showing areas covered by GANOVEX in northern Victoria Land. Shaded areas are mentioned in text.

1980 REvIEw 7

ages are possible, but no other fossils were found to date thesequence more precisely.

Paleocurrent directions measured in approximately 30 lo-calities indicate that all turbidites were deposited from southto north. Flute casts (figure 2), crossbeds, tool marks, andripple-mark orientations were used for paleocurrent deter-minations and were corrected for present dip of the beds.

Preliminary thin section petrography of the coarser rockscollected indicates sedimentary and metamorphic sourceareas for the Robertson Bay Group, but unlike previousstudies, a minor mafic volcanic rock fragment componentwas observed consistently (figure 3).

The Robertson Bay Group rocks have been metamor-phosed to corderite/biotite/hornblende hornfels by De-vonian intrusives. The mechanism of emplacement seemsto be by stoping. We saw no evidence for major forcibleinjection. This, plus the absence of sediments derived fromuplifts normally associated with orogeny, limits this eventto granitic intrusives. Thus, the "Borchgrevink" Orogeny, aproposed mountain-building event, does not seem to be atrue orogeny, at least in north Victoria Land.

These preliminary findings will be augmented by furtherresearch on the samples. Relationships to rocks in the

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Figure 2. Flute casts on bottom of a turbidite bed. Hammer isused for scale. Robertson Bay, northern Victoria Land.

Figure 3. Photomicrograph of coarse-grained Robertson BayGroup turbidite. Note sedimentary (a) and igneous (b) rockfragments. Fragments are approximately 2 millimeters indiameter.

USARP Mountains (Wilson Group in the Daniels Range)and the Bowers Graben (Bowers Supergroup between theLeap Year and Rennick Glaciers) were also investigated byGANOVEX. The new data may shed more light on Pre-cambrian events that helped form this rock group.

This work was supported in part by National ScienceFoundation grant EAR 78-23645 and in part by the BGR ofWest Germany.

References

Crowder, D. F. 1968. Geology of a part of northern Victoria Land,Antarctica. U.S. Geological Survey Professional Paper, 600-D,95-107.

Harrington, H. J . , Wood, B. L., McKellar, I. C., and Lensen, G. J.1967. Topography and geology of the Cape Hallette District,Victoria Land, Antarctica. New Zealand Geological Survey Bulletin,80, 100 pp.

LeCouteur, P. C., and Leitch, E. C. 1964. Preliminary report on thegeology of an area south-east of the Upper Tucker Glacier, north-ern Victoria Land. In R. J . Adie (Ed.), Antarctic Geology. Amster-dam: North-Holland Publishing Co.

Mutti, E., and Ricci Lucchi, F. 1972. Turbidites of the northernApennines: Introduction to facies analysis. International GeologyReview, 20, 125-166.

Rastall, R. H., and Priestley. R. E. 1921. The slate-graywacke forma-tion of Robertson Bay: British Antarctica ('Terra Nova') expedi-tion, 1910, natural history report. Geology, 1, 121-129.

Sturm, A. G., and Carryer, S. 1970. Geology of the region betweenMatusevich and Tucker Glaciers, northern Victoria Land.Antarctica. New Zealand Journal of Geology and Geophysics, 13,408-435.

Hyaloclastite of DVDP 3, Hut PointPeninsula, Antarctica

SAMUEL B. TREVES

Department of GeologyUniversity of Nebraska

Lincoln, Nebraska 68588

Dry Valley Drilling Project (DVDP) was drilled 3 metersnorth of DVDP 2 (77 0 50' 59.59"S 166 040' 26.68"E) at the baseof Observation Hill during WINFLY of the 1973-74 field sea-son (Kyle and Treves 1974). Drilling produced about 380meters of core. The rocks penetrated consist of 10 flows and5 fragmental units. The oldest unit is a hyaloclastite and is214 meters thick. It is the subject of this report.

From top to bottom the hyaloclastite consists of 21 me-ters of mixed volcanic breccia that is primarily a blocky

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