years ago (Boudette et al., 1966; Halpern, 1968; Wade,1969, 1972).

Evidence for the first two events is restricted to west-ern Marie Byrd Land; for the third, it is restricted toeastern Marie Byrd Land. On the basis of this and thedistribution of metavolcanics, Lopatin and Orlenko(1972) concluded that two geologic provinces can bedistinguished in this sector: one includes the FordRanges, and the other includes all of Marie Byrd Landto the east of the Ford Ranges. I disagree and suggestthat the two areas constitute a single geologic provincein which the orogenies during the Paleozoic era pro-gressed in age from older in the west, to younger inthe east. Western Ellsworth Land should be includedwith eastern Marie Byrd Land, and a break betweenprovinces, if any, should be placed between the JonesMountains and the Behrendt Mountains, in the EightsCoast sector.

Laudon (1972) described the similarities of easternEllsworth Land and the Antarctic Peninsula. Mesozoicgeosynclinal deposits are present in both and are lackingto the west in western Ellsworth Land and in all ofMarie Byrd Land. A major tectonic event, probablyduring early Cretaceous, appears to have united the entirecoastal sector of West Antarctica into a single province.Cretaceous and Cenozoic histories of all of the segmentsare quite similar. Additional field and laboratory studiesof the basement complex, particularly in the KohlerMountains-Bear Peninsula area, will be necessary beforethe single province hypothesis for Marie Byrd Land andwestern Ellsworth Land can be accepted with confidence.

An attempt to date and zone the metasedimentary rocksequences, on the basis of acritarch and other microfossilassemblages, was scheduled to begin in this laboratoryin August of this year. If successful to any degree, theproject will be expanded to include the metasedimentarysequences of the Queen Maud Range, TransantarcticMountains. A more meaningful geologic history ofAntarctica during the Precambrian and early Paleozoictimes may be the result of these investigations.

Topographic maps of three quadrangles of Marie ByrdLand, 1:250,000 reconnaissance series, have been issuedby the U.S. Geological Survey. They are: the AlexandraMountains, Guest Peninsula, and Boyd Glacier quad-rangles. The geology will be superimposed on them byJerry Oldham and Carl Cathey, research assistants in thisoffice who have been trained in the art at the U.S. Geo-logical Survey, Federal Center, Denver, Colorado. Themaps will be included in the final reports scheduled forcompletion on July 1, 1974. This work is supported byNational Science Foundation grant GV-22901A.

References

Boudette, E. L., R. F. Marvin, and C. E. Hedge. 1966. Biotitepotassium-feldspar, and whole rock ages of adamellite, Clark

Mountains, West Antarctica. U.S. Geological Survey. Pro-fessional Paper, 550-D: 190-194.

Halpern, M. 1968. Ages of antarctic and Argentine rockshearing on continental drift. Earth and Planetary ScienceLetters, 5(3): 159-167.

Halpern, M. 1972. Rb-Sr total rock and mineral ages fromthe Marguerite Bay area, Kohler Range, and Fosdick Moun-tains. In: Antarctic Geology and Geophysics (R. J . Adie,ed.). Oslo, lJniversitetsforlaget. 197-204.

Klimov, L. V. 1967 (English language translation). Some re-sults of geological observations in Marie Byrd Land, 1966-1967. information Bulletin of the Soviet Antarctic Expedi-tion, 6(5): 473.479.

Krylov, A. Ya., B. G. Lopatin, and 1'. 1. Mazina. In Press Theage of rocks from the Ford Ranges and Ruppert Coast.Information Bulletin of the Soviet Antarctic Expedition, 80.

Lopatin, B. G., and E. M. Orlenko. 1972. Outline of the geol-ogy of Marie Byrd Land and Eights Coast. In: AntarcticGeology and Geophysics (R. J . Adie. ed.). Oslo, Univer-sitetsforlaget. 245-250.

Laudon, T. S. 1972. Stratigraphy of eastern Ellsworth Land.In: Antarctic Geology and Geophysics (R. J . Adie, ed.).Oslo, Universitetsforlaget. 215-224.

Wade, F. A. 1969. Geology of Marie Byrd Land. AntarcticMap Folio Series, 12 (XVII).

Wade, F. A. 1972. Geologic survey of Marie Byrd Land.Antarctic Journal of the U.S., Vu(s) : 144-145.

Antarctic geological studiesCAMPBI:I.L CRADDO(;K

Department of Geology al/c! GeophysicsLJni versi/y of IFisco,ijin, ZUadisoi,

Work continued this year on bringing to publicationthe results of 8 seasons of geological study in parts ofWest Antarctica. Recent effort has been concentrated onthe geology of the Jones Mountains and the EllsworthMountains. Evidence for Tertiary continental glaciationin the Jones Mountains was summarized in a recent paper(Rutford ci al., 1972). Because of the importance ofestablishing an accurate minimum age for this glacia-tion, additional work is underway at the University ofNebraska to check, by fission track dating, the age ofthe volcanic rocks immediately overlying the glaciatedsurface. With the help of Dr. K. B. Sporli, of the Uni-versity of Auckland, work on the stratigraphy of theEllsworth Mountains is nearing completion. In addition,there has begun a special study of the environment andprovenance of the Polarstar Formation (Permian), theyoungest bedrock formation in the Ellsworth Mountains.

The 1:5,000,000 Geologic Map of Antarctica (Crad-dock, 1972a) has been published and it was announcedin a number of journals and displayed at four national orinternational geological meetings.* Along with Folio 12(Bushnell and Craddock, 1970) and my field work, thismap provided the basis for a new interpretation of ant-

258 ANTARCTIC JOURNAL

arctic tectonics (Craddock, 1972b) and new insight intothe tectonic evolution of Gondwanaland (Craddock, inpress, a).

As U.S. member of the Scientific Committee on Ant-arctic Research working group on Geology, I supervisedthe preparation of the fourth and fifth annual reports tothe Scientific Committee on Antarctic Research on U.S.Antarctic Research Program earth sciences activities(Craddock, 1972c, in press, b) and the compilation of alexicon of stratigraphic names introduced by meinbers ofU.S. antarctic expeditions (Wegner and Craddock,1972).

I have been serving as a member of the AntarcticAdvisory Panel of the Deep Sea Drilling Project andtook part in planning the 6 legs we hope to see completedin antarctic oceans. Two of these legs were successfullyaccomplished during the 1972-1973 season. I hope toParticipate in the next leg, scheduled to begin in January1971.

At the request of the U.S. Geodynamics Committee,I contributed a section on Antarctica to a draft of theproposed U.S. Geodynamics Program

References

Bushnell, V. C., and C. Craddock (eds.). 1970. Geologicmaps of Antarctica. Antarctic Map Folio Series, 12.

Craddock, C. 1972a. Geologic Map of Antarctica, 1:5,000,000,42 x 48 inches. American Geographical Society, New York.

Craddock, C. 1972b. Antarctic tectonics. Antarctic Geologyand Geoph)'cIcs. Universitetsforlaget, Oslo. 449-455.

Craddock, C. (ed.). 1972c. Earth sciences investigations inthe U.S. Antarctic Research Program for the period July 1,1971, to June 30, 1972. National Academy of Sciences. 44 p.

Craddock, C. In press, a. Tectonic evolution of the Pacificmargin of Gondwanaland. Proceedings of the Third Inter-national Gonduana Symposium, Canberra.

Craddock, C. (ed.). In press, b. Earth sciences investigationsin the U.S. Antarctic Research Program for the period July1, 1972, to June 30, 1973. National Academy of Sciences.

Rutford, R. H., C. Craddock, R. L. Armstrong, and C. M. White.1972. 'Tertiary glaciation in the Jones Mountains. AntarcticGeology and Geophysics, Universitetsforlaget, Oslo. 239-244.

Wegner, W.. and C. Craddock. 1972. Lexicon of stratigraphicnames introduced by members of U.S. antarctic expeditions.National Academy of Sciences. 129 p.

* It can be obtained for $6 plus $1 handling, from theAmerican Geographical Society, Broadway at 156th Street, NewYork, New York 10032.

Neotectonics in the antarctic Pacificsector

WESLEY E. LEMASURIER

I)ii'isioti of Natural and Phyiical Sciences(Jniversit)' of Colorado. Denier

Recent tectonic activity in Antarctica is difficult todemonstrate. One can not observe direct evidences of dis-placement, such as fresh fault scarps in alluvial fans oroffset stream courses and roads. Furthermore, the conti-nent appears to be aseismic, which suggests that tectonicactivity is at a standstill. In Marie Byrd Land, however,there are intraglacial volcanoes whose ages and elevationssuggest rapid tectonic uplift so recent that the upliftlikely is continuing today. Together with new evi-dence for Plio-Pleistocene tectonic uplift in the McMurdoSound Region (Webb, 1972 among others), this givesreason to consider the possibility that the Pacific sectorof Antarctica still is tectonically active.

The most compelling evidence for Quaternary tecto-nism in Marie Byrd Land lies in the geologic relation-ships of four volcanoes found near the coast of theAmundsen Sea. All four stand 2000 to 3000 metersabove the ice sheet's present level. Their ages, composi-tion, internal structure, and external form have been de-scribed (LeMasurier, 1972a, 1972b, 1972c) and brieflyare reviewed here. Mount Murphy, apparently the oldestof the four, yielded a K-Ar whole rock date of 0.82(±0.11) million years. Two thousand meters above icelevel, it is composed entirely of palagonite breccias(evidenced by excellent exposures in the walls of largecirques). The palagonite breccias indicate that MountMurphy was formed entirely by eruptions beneath thecontinental ice sheet. Toney Mountain also stands 2000meters above the ice. It is composed entirely of subaerialflow rock and 2 samples each have yielded K-Ar datesof 0.5 million years. Mount Takahe is composed en-tirely of palagonite breccia, stands 2100 meters aboveice level, and 3 samples were too young to be dated(i.e. less than 0.2 to 0.3 million years). Mount Siplenever has been visited, but it is believed to be composedof palagonite breccias because of its low height and basaldiameter ratio (LeMasurier, 1972b), and to be Quater-nary in age because the mountain's degree of glacial dis-section is far less than Mount Murphy and more thanMount Takahe (Andrews and LeMasurier, 1973).Mount Siple stands about 3000 meters above ice level.

If one assumes, as a limiting case, that ice level re-mained stationary throughout the Quaternary, then itwould appear that Toney Mountain has remained nearlystationary since its formation. Alternatively, it may havesubsided from a still higher elevation, during the last500,000 years. Mount Murphy and Mount Takahe, 75

September-October 1973 259