Figure 3. A: stereographic net diagram of poles to foliation for Thala Hills (233 measurements). Contours are 0.5, 3, 6, 9, 12, and 15 percent area. 13( = 7r) axis plunges 100 to S. 71 0E. B: stereographic net diagram of lineations for Thala Hills (153 measurements). Con- tours are 1, 5, 15, 25, and 35 percent area. L, the lineation maximum, B ()c plunges 14° to S. 71°E. C: stereographic net projection of poles to faults and mylonite zones. Triangles indicate left-handed movement sense (19 measurements). p—rough average of poles to faults and mylonite zones, one for each movement sense. o, 0 21 cr31 in- ferred directions of principal stresses. The angle between the two averaged poles is 65°, that between O 3 and 8( = 7T) is 21°, and between O3 and L it is 23°. Dashed lines represent projections of planes perpendicular to the principal stresses.

Halpern (University of Texas, Dallas). Calculated Enderby Land near Molodezhnaya Station, Antarctica. Ant- ages (y = 1.47 x 10 11 per year) on seven samples arctic Journal of the U.S., V(4): 158-159. of quartzo-felds path ic gneiss range between about Ravich, M. G., and Ye. N. Kamenev. 1972. Kristallicheskiy fundament A ntarkticheskoy platformy (Crystalline fundament of 700 and 2,275 million years, assuming an initial the Antarctic Platform). Leningrad, Gidrometeoizdat. 6581). strontium-87/strontium-86 ratio of 0.705. Nine of Scharon, LeRoy, C. Scharnberger, Thomas Early, and Akira eleven samples of the charnockitic gneiss gave an Shimoyana. 1970. International cooperation for paleomag- isochron with a slope of 987 ± 60 million years and netic insight into antarctic tectonic history. Antarctic Journal of the U.S., V(5): 210-224. an initial ratio of 0.719 ±0.0015 (95-percent con- Trail, D. S., and I. R. Mcleod. 1969. Geology of Enderby Land. fidence level). Antarctic Map Folio Series, 12 (sheet 11). New York, Ameri- I am making a petrologic study with the electron can Geographical Society. microprobe of gneisses having the mineral assem- blages quartz-plagioclase-K feldspar-biotite-ortho- pyroxene±garnet and quartz-plagioclase-K feld- spa r-biotite-garnet ± sillimanite± cord ierite. W. I. Manton, University of Texas, Dallas, is making a uranium-thorium-lead isotope study of allanite and monazite from pegmatite. I thank P. K. Senko, chief of the 18th SAE, and other members of the expedition at Molodezhnaya Geology and petrography of for their logistics support, their cooperation, and their generous assistance for my field work. The DVDP hole 1, Hut Point Peninsula, research was supported by National Science Foun- Ross Island dation grant opp 72-05797.

References SAMUEL B. TREVES and M. Z. ALL

Kamenev, Ye. N. 1972. Geological structure of Enderby Land. Department of Geology In: Antarctic Geology and Geophysics (Adie, R. J . , editor). Oslo, University of Nebraska Universitetsforlaget. 579-583. Kamenev, Ye. N., L. V. Klimov, and 0. G. Shulyatin. 1965. Lincoln, Nebraska 68508 Geologicheskoye stroyeniye Zemli Enderbi i Berega Printsa Ulafa (Geological structure of Enderby Land and of the Prince Olaf Coast). The Antarctic, The Committee Reports, 1964. Moscow, "Nauka" Publishing House. 5-27. Dry Valley Drilling Project (DvDP) hole 1 was Klimov, L. V. 1965a. Geologicheskoye issledovaniya v rayone drilled during the 1972-1973 austral summer on Berega Printsa Ulafa v 1964 g. (Geological investigations in the south flank of Twin Crater, an extinct volcano the region of the Prince Olaf Coast in 1964). Soviet Antarctic near McMurdo Station, Ross Island (Treves and Expedition Information Bulletin, 51: 55-63. Kyle, 1973). Core recovered from the hole totaled Klimov, L. V. 1965b. Geologicheskoye stroyeniye zapadnoy chasti Zemli Enderbi (Geologic structure of the western part 196.54 meters. The rocks penetrated consisted of of Enderby Land). Trudy of the Soviet Antarctic Expedition (7th 40 lava flows, nine pyroclastic units, and one dike. cruise of d/e Ob 1961-1962), 44: 160-174. The flows are rather thin and most are oxidized. Myers, P. B., Jr., and E. E. MacNamara. 1970. Rocks of coastal They exhibit phenocrystic kaersutite, augite, and 248 ANTARCTIC JOURNAL Modal analyses of flow units, DVDP hole 1, olivine, and range from basalt to andesite. The Hut Point Peninsula, Ross Island pyroclastic units range from tuff to lapilli tuff to blocky breccia; two units show conglomeratic phases. The dike is andesitic. The table summarizes our petrographic results to date and indicates the modal mineralogy and nomenclature of the flow ç bC units and the dike (unit 28). Briefly, the basalts t) .2 contain modal labradorite, andesites contain modal 1 .) . bJJ a andesine, and trachytic andesites exhibit trachytic H H C texture and contain modal oligoclase or andesine. Triangular plots of plagioclase-pyroxene-amphi- bole and plagioclase-pyroxene-olivine suggest that all of the flows are differentiates of common 3.03 1.00 A 28 22 Tr 0 40 2 2.27 4.82 A 30 25 2 28 magma type. The earliest differentiate is a py- 3 1.17 5.58 B 30 22 8 24 roxene-olivine basalt; the last is trachytic, kaersu- 4 0.49 6.78 A 24 26 () 4 29 tite andesite. These petrographic and mineralogic 5 0.87 7.67 A 26 21 4 2 15 data are compatible with field data (Treves, 1967) 6 1.11 8.17 A 40 25 2 6 and chemical data (Goldich et al., in press). 7 4.58 12.21 A 37 24 2 11 7 4.58 13.18 A 38 24 2 11 In the field, the units of hole 1 were assigned 9 2.31 15.08 A 38 25 2 12 to five eruptive sequences and correlated with the 10 1.75 17.10 A 37 17 5 15 rocks of DVDP hole 2 (Treves and Kyle, 1973). Sub- 11 1.77 18.43 A 35 17 5 2 17 sequently, DVDP hole 3 was drilled (1973-1974 12 1.41 20.04 A 35 18 5 2 18 13 2.36 22.09 A 30 18 0 22 field season) (Kyle and Treves, 1974), and addi- 14 3.18 23.91 A 32 17 0 22 tional laboratory work was done on the rocks of 15 3.10 27.26 A 30 20 6 0 20 holes 1, 2, and 3, and on the rocks of the surface 16 2.97 32.33 B 38 19 0 17 exposures of Hut Point Peninsula (Kyle and 17 3.83 32.95 B 58 24 2 0 0 18 7.24 39.04 B 50 26 2 0 0 Treves, 1974). These data indicate that the tenta- 18 7.24 41.01 B 47 26 3 0 tive correlation of Treves and Kyle (1973) needs 19 1.72 44.14 A 42 11 4 0 21 revision. A revision based on the data presented 20 4.43 48.14 A 42 20 3 0 11 here, on some chemical data, and on some recent 21 1.91 50.95 A 43 19 3 0 10 radiometric dates was presented by Treves and 22 4.54 53.51 A 33 19 4 0 19 23 2.52 57.94 B 35 18 3 0 25 Ali (1974). 24 3.78 59.03 A 36 26 3 0 6 1 24 3.78 62.00 56 12 5 0 11 This research was supported by National Science 25 0.88 63.00 34 13 8 0 37 Foundation grant ot,,p 74-20304. 27 3.40 81.53 B 43 20 10 2 0 28 6.30 81.62 66 16 2 0 0 28 6.30 87.18 C 64 15 4 0 0 29 5.44 88.55 D 60 18 0 0 References 29 5.44 91.43 A 53 19 2 0 29 5.44 91.45 A 53 25 2 0 30 0.85 93.93 E 25 29 0 18 18 Goldich, S. S., S. B. Treves, N. H. Suhr, and J. S. Stticklcss. 31 2.29 94.51 E 25 30 0 17 18 In press. Geochemistry of the Cenozoic volcanic rocks of 33 1.34 104.80 E 24 33 0 16 7 Ross Island and vicinity Antarctica. Journal of Geology. 34 6.87 111.37 E 22 29 0 23 6 Kyle, P. R., and S. B. Treves. 1974. Geology of DVDP 3, Hut 35 0.71 112.27 E 21 34 0 20 a Point Peninsula, Ross Island, Antarctica. In: Thy Valley Drilling 37 7.05 121.88 22 30 0 17 13 Project Bulletin 3. DeKaib, Northern Illinois University. 13- 40 3.86 131.36 A 61 18 0 0 48. 41 0.50 131.84 53 10 8 0 20 Kyle, P. R., and S. B. Trcves. 1974. Geology of Hut Point Penin- 43 0.36 133.76 A 60 19 0 sula, Ross Island. Antarctic Journal of the U.S., IX(5): 232- 45 0.55 134.41 A 56 22 0 234. 46 3.22 137.11 C 52 19 2 0 Treves, S. B. 1967. Volcanic rocks from the Marguerite Bay, 47 3.81 138.12 1) 50 22 0 0 Ross Island, and Mt. Weaver areas, Antarctica. Tokyo, De- 48 2.31 142.51 C 57 18 0 partment of Polar Research, Japanese Antarctic Research Expedition. Scientific Reports, 1. Treves, S. B., and M. Z. Ali. 1974. Geology and petrography of DVDP 1, Hut Point Peninsula, Ross Island, Antarctica. In: Thy Valley Drilling Project Bulletin 4. DeKalb, Northern A= Kaersutite basalt B= Kacrsutjte andesite Illinois University. 60-61 (abstract). C=Trachytic kaersutite 1)= Pyroxene basalt Treves, S. B., and P. R. Kyle. 1973. Geology of DVDP I and andesite E= Pyroxene-olivine basalt 2, Hut Point Peninsula, Ross Island, Antarctica. In: Dry Valley Drilling Project Bulletin 2. DeKalb, Northern Illinois Univer- sity. 11-82. September/October 1975 249