Small veins containing sulfides occur in older volcanic ice in the Orville Coast, Antarctic Peninsula. Antarctic Journal rocks elsewhere in the Sky-Hi Nunataks. These veins of the United States (this issue). seem to represent peripheral veins that have extended Kellogg, K. S. 1979a. Structural geology of Orville Coast and eastern Ellsworth Land. Antarctic Journal of the United States outward from the stock. (this issue). Future work on the stock is scheduled to include po- Kellogg, K. S. 1979b. New paleomagnetic evidence for oroclinal tassium-argon age dating of this and other plutons in bending of the southern Antarctic Peninsula. Geological So- the field area by Edward Farrar (Queens University, ciety of America Bulletin, September issue. Ontario), as well as petrographic work. Kellogg, K. S., and P. D. Rowley. 1974. Structural geology of Preliminary study of the invertebrate fossils from the the Lassiter Coast. Antarctic Journal of the United States, 9(5): Latady Formation by M. R. A. Thomson (British Ant- 224-25. arctic Survey) indicates that Upper Jurassic (Tithonian) Rose, A. W. 1970. Zonal relations of wallrock alteration and fossils are very abundant. The petrography of the clastic sulfide distribution at porphyry copper deposits. Economic Geology, 65(8): 920-36. rocks of the Latady Formation is being done by T. S. Rowley, P. D. 1978. Geologic studies in Orville Coast and east- Laudon (University of Wisconsin-Oshkosh). Laudon, ern Ellsworth Land, Antarctic Peninsula. Antarctic Journal of Thomson, and J. M. Boyles (University of Texas at Aus- the United States, 13(4): 7-9. tin) will expand on their preliminary field account by Rowley, P. D. In press. Geology of the northern Lassiter Coast collaborating on research on the stratigraphy of the La- and southern Black Coast, Antarctic Peninsula. In Third tady Formation (Thomson, Laudon, and Boyles, 1978). Symposium on Antarctic Geology and Geophysics, ed. C. Crad- In addition to the work on the geology of the Orville dock. Madison: University of Wisconsin Press. Coast and eastern Ellsworth Land, W. R. Vennum has Rowley, P. D.., P. L. Williams, and D. L. Schmidt. 1977. Geology of an Upper Cretaceous Copper Deposit in the Andean Province, completed electron-microprobe, petrographic, and Lassiter Coast, Antarctic Peninsula. U.S. Geological Survey chemical studies of some trachytes from Ross Island. Professional Paper, no. 934. The research studies described in this article have Thomson, M. R. A., T. S. Laudon, and J . M. Boyles. 1978. been supported by National Science Foundation grant Stratigraphical studies in Orville Coast and eastern Ell- DPP 76-12557. sworth Land. Antarctic Journal of the United States, 13(4): 9- 10. References Vennum, W. R. 1979. Evaporite encrustations and yellow and green surficial salts from Orville Coast and eastern Ell- Carrara, P. E. 1979. Evidence of former, more extensive glacial sworth Land. Antarctic Journal of the United States (this issue).

merous locations along the Antarctic coastline (Gibson Evaporite encrustations and 1962; Hirabayashi and Ossaka, 1976; MacNamara anc yellow and green surficial salts Usselman, 1972; Morikawa et al., 1975; Nishiyama anc Kurasawa, 1975; McLeod, 1964; Toni et al., 1973). Cal from Orville Coast and eastern cite, gypsum, thenardite, and mirabilite are the mos common minerals reported, although numerous mor Ellsworth Land complex salts also occur. Evaporation of saline lak waters and contribution of ions by ocean spray hav been called upon to explain the more exotic minerals WALTER R. VENNUM Reported occurrences of evaporite efflorescences an( crusts from the antarctic interior, where salt spray oi Department of Geology saline lake water cannot be a major contributing factor Sonoma State University are scarce and consist of only a few samples (Tasch an( Rohnert Park, California 94928 Angino, 1968; Cameron and Ford; Skidmore an and Clarkson, 1972). The only minerals that have been re U.S. Geological Survey ported are gypsum, calcite, thenardite, mirabilite, an( Menlo Park, California 94025 hexahydrite. During the 1977-78 field season, white encrustation and yellow and green surficial salts were collected fron During the past year, I have studied samples of evap- 72 sites scattered over an area of about 30,000 squan oritic surface encrustations and surficial salts that were kilometers of the Orville Coast and eastern Ellswortl collected during the 1977-78 field season from numer- Land (74°-76°30S164°-74°W). None of these encrusta ous inland sites in the Orville Coast area and eastern tions and surficial salts were collected at sites closer t( Ellsworth Land. As summarized below, my results in- the coast than 70 kilometers in the direction of the pre clude identification of five minerals that previously had vailing northwest wind, and the majority of the sample not been reported from Antarctica. were collected from sites lying at much greater distances Evaporite salts occurring as efflorescences, crusts, and As the majority of the sites lie south and east of th4 thick stratified deposits have been reported from nu- 2,000-meter-high crest of the Antarctic Peninsula, thi

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,•1 I I I j II III lilt III Ommi 2 3 OmmI 2 3 4 5 6 7 8 9 10 Figure 1. Popcorn-like mass of calcite from an unnamed Figure 2. Hollow nodular masses of gypsum from the Haub- nunatak in the northwestern Merrick Mountains. erg Mountains. contribution of ions directly from ocean spray or indi- study area in 1969-70, 1970-71, and 1972-73 (Rowley, rectly from coastal snow blown far inland is believed to Williams, and Schmidt, 1977). These salts also occur at be negligible. scattered locations throughout the Orville Coast and A total of 104 samples-90 of the white crusts, 6 of eastern Ellsworth Land (Rowley, 1978). The green salts the yellow salts, and 8 of the green salts—was analyzed are composed of atacamite [Cu 2(OH)3C1], atacamite using X-ray diffraction techniques (CUM, radiation, Ni with traces of brochanite [Cu4(SO4)(OH)6], and mixtures filter). of atacamite and plancheite [3CuSiO 3 H201, brochan- The white salts occur either as scaly-to-granular crusts tite-antlerite [Cu3(SO4)(OH)4], and also brochantite- with locally developed bead-like surfaces (figure 1) or as plancheite. hollow nodular or bulbous masses (figure 2), with each Stewart (1964) does not mention alunite, brochantite, mass being as much as 90 millimeters in diameter. They fibroferrite, natrojarosite, or plancheite in a list of ant- are predominately gypsum, calcite, or gypsum-calcite arctic minerals. In addition, further literature search has mixtures, but also contain lesser ammounts of aragonite shown that these five minerals have not previously been and thenardite. They occur exclusively on nunatak sum- reported from Antarctica. mits, exposed windswept slopes, windward sides of ridge My work has been supported by National Science crests, or windswept notches in ridge crests. In addition, Foundation grant DPP 76-12557. they are much more extensively developed on strongly fractured or frost-shattered rocks. References These facts suggest that their formation is associated Cameron, R. E., and A. B. Ford. 1974. Baseline analysis of soils with the melting of snow driven into cracks by ground from the Pensacola Mountains. Antarctic Journal of the United blizzards; the water later returns to the rock surface by States, 9(4): 116-19. capillary action, eventually depositing dissolved ions as Gibson, G. W. 1962. Geological investigation in southern Vic- toria Land, Antarctica. Pt. 8, Evaporite salts in the Victoria crusts during periods of high evaporation. Conse- Valley region. New Zealand Journal of Geology and Geophysics, quently, the presence of these salts constitutes evidence 5: 361-74. for slow chemical weathering under present meteoro- Hirabayashi,J., and J. Ossaka. 1976. The x-ray diffraction pat- logical conditions and indicates that transportation of terns and their mineral components of evaporites at Prince salt-bearing solutions can take place in frigid climates Olav Coast, Antarctica. Japanese Antarctic Research Expedition under arid conditions. Report, no. 32. No correlation exists between source rock and type of MacNamara, E. E., and T. Usselman. 1972. Salt minerals in soil salt present in the crust, or between type of salt devel- profiles and as surficial crusts and efflorescences, coastal Enderby Land, Antarctica. Geological Society of America Bul- oped and either elevation of the collecting site or dis- letin, 83: 3145-50. tance of the collecting site from the coast. Natrojarosite McLeod, I. R. 1964. The saline lakes of the Vestfold Hills, ENaFe3(SO4)2(OH)6 is present as yellow surface stains on 1 Princess Elizabeth Land. In Antarctic Geology, ed. R. J . Adie, about 30 percent of the encrustations examined. pp. 65-72. New York: John Wiley. The yellow surficial salts found include alunite Morikawa, H., I. Minato,J. Ossaka, and T. Hayashi. 1975. The [KA I 3(SO4)2(OH)6}, fibroferrite [Fe(SO4)(OH . 51-1201, distribution of secondary minerals and evaporites at Lake and natrojarosite. All three of these minerals have Vanda, Victoria Land, Antarctica. National Institute of Po- formed through the oxidation in place of pyrite dissem- lar Research (Tokyo) Memoirs, special issue no. 4, pp. 45- inated in black shale and slate and/or granodiorite. 59. Nishiyama, T., and H. Kurasawa. 1975. Distribution of second- Green surficial salts were observed in numerous places ary minerals from Taylor Valley. Dry Valley Drilling Project by U.S. Geological Survey field parties while they mapped Bulletin, 5: 120-33. the Lassiter Coast and Black Coast to the north of the Rowley, P. D. 1978. Geologic studies in Orville Coast and east-

23 ern Ellsworth Land, Antarctic Peninsula. Antarctic Journal of Stewart, D. 1964. Antarctic mineralogy. In Antarctic Geology, ed. the United States, 13(4): 7-9. R. J. Adie, pp. 395-401. New York: John Wiley. Rowley, P. D., P. L. Williams, and D. L. Schmidt. 1977. Geology Tasch, P., and E. E. Angino. 1968. Sulphate and carbonate salt of an Upper Cretaceous copper deposit in the Andean Prov- efflorescences from the Antarctic interior. Antarctic Journal ince, Lassiter Coast, Antarctic Peninsula. U.S. Geological Sur- of the United States, 3(6): 239-4 1. vey Professional Paper, no. 984. Toni, T., S. Murata, V. Yoshida, J . Ossaka, and N. Yamagata. Skidmore, M. J ., and P. D. Clarkson. 1972. Physiography and 1973. On the evaporites found in Miers Valley, Victoria glacial geomorphology of the Shackleton Range. British Ant- Land, Antarctica. U.S. Army Cold Regions Research Engi- arctic Survey Bulletin, 30: 69-80. neering Laboratory Translation, no. 390.

McLellands biotite. Our Rb-Sr date is in agreement Investigation of an anomalous with the K-Ar date reported by McLelland, but does not date for Lonely Ridge confirm his Rb-Sr date. The available age determinations, therefore, indicate granodiorite, Nilsen Plateau, that the Lonely Ridge granodiorite crystallized 620 ± 13 Transantarctic Mountains million years ago and that biotite in this rock has re- tained radiogenic 40Ar and 87 Sr for the past 470 million years. The mineral dates coincide with the waning stage of the Ross orogeny, which included widespread mag- ROBERT P. FELDER and GUNTER FAURE matic activity from about 540 to 510 million years ago (Faure et al., in press). The associated thermal and dy- Institute of Polar Studies namic metamorphism could have caused loss of radi- The Ohio State University ogenic daughters that had accumulated in the biotite Columbus, Ohio 43210 between the time of initial crystallization and the end of the Ross orogeny. This research has been supported by the Division of The Lonely Ridge granodiorite is part of the basement Polar Programs of the National Science Foundation complex of the Nilsen Plateau, which is located between through grant DPP 77-21505. the Amundsen Glacier and Scott Glacier. Mirsky (1969) and Craddock (1970) published potassium-argon (K-Ar) and rubidium-strontium (Rb-Sr) dates obtained by McLelland (in press) on biotite separated from an un- altered specimen of the Lonely Ridge granodiorite. The References K-Ar date is 472 .t 10 million years (compatible with magmatic activity of the Ross orogeny), whereas the Rb- Craddock, C. 1970. Radiometric age map of Antarctica. In Ge- Sr date is 846± 35 million years. ology of Antarctica, plate 19. Antarctic Map Folio Series, folio This is anomalous because dates obtained by these 12. New York: American Geographical Society. methods on biotite are commonly in close agreement Faure, G., R. Eastin, P. T. Ray, D. McLelland, and C. H. Shultz. owing to similar retentivity of biotite for radiogenic In press. Geochronology of igneous and metamorphic 40Ar and 87 Sr (Hart, 1964). A whole-rock Rb-Sr isochron rocks, central Transantarctic Mountains. In Proceedings, date of 620± 13 million years, reported by Faure et al. Fourth International Gondwana Symposium. Calcutta, India. Felder, R. P. 1979. Isotopic and petrographic study of the (in press), presumably indicates the time of crystalliza- Lonely Ridge granodionite, Nilsen Plateau, Antarctica. Un- tion of the Lonely Ridge granodiorite. published B. Sc. thesis, Department of Geology and Min- We have obtained a Rb-Sr date of biotite from a spec- eralogy, The Ohio State University. imen of the Lonely Ridge granodiorite collected by Hart, S. R. 1964. The petrology and isotopic-mineral age re- McLelland. The specimen (O.S.U. 480, McLelland 208) lations of a contact zone in the Front Range, Colorado.Jour- was chosen because it fits the whole-rock Rb-Sr isochron nal of Geology, 72: 493-525. and displays less cataclastic deformation than any of the McLelland, D. In press. Geology of the basement complex, other available specimens (Felder, 1979). Nilsen Plateau, Antarctica. In Special Transantarctic Volume, ± 17 million eds. J. F. Splettstoesser and M. D. Turner. Washington, Our results indicate a Rb-Sr date of 470 D.C.: American Geophysical Union. y for the decay years, based on a value of 1.42 x 1 0-11 Mirsky, A. 1969. Geology of the Ohio Range-Liv Glacier area. constant of 87R and a value of 0.704 for the initial 87Sr/ In Geology of Antarctica, plate 16, sheet 17. Antarctic Map 86 Sr ratio. Using these constants, we obtained a date of Folio Series, folio 12. New York: American Geographical 848 ± 35 million years from the analytical data of Society.

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