Geologic studies in Orville Coast and eastern Ellsworth Land
to the reconstruction of southwestern Gondwanaland. Tec-
tonophysics, 37: 53-81.
Farrar, E., S. L. McBride, and P. D. Rowley. In press. Ages and tectonic implications of Andean plutonism in the southern
Antarctic Peninsula. In Third Symposium on Antarctic Geology and Geophysics, ed. C. Craddock. Madison: University of
Wisconsin Press. Herron, E. M., and B. E. Tucholke. 1976. Sea-floor magnetic patterns and basement structure in the southeastern Pacific. In Initial Report of the Deep Sea Drilling Project, 35: 263-78.
Washington, D.C.: U.S. Government Printing Office. Kellogg, K. S. 1979. New paleomagnetic evidence for oroclinal bending of the southern Antarctic Peninsula. Geological Society of America Bulletin, September issue. Kellogg, K. S., and P. D. Rowley. 1974. Structural geology of the Lassiter Coast. Antarctic Journal of the United States, 9: 224-25.
Laudon, T. S., L. L. Lackey, P. G. Quilty, and P. M. Ostway. 1969. Geology of eastern Ellsworth Land (sheet 3, eastern Ellsworth Land). In Geologic maps of Antarctica, eds. N. C.
Geologic studies in Orville Coast and eastern Ellsworth Land PETER D. ROWLEY
U.S. Geological Survey Denver, Colorado 80225
Studies of the geology of the Orville Coast and eastern Ellsworth Land (74°-76 030'S/65°-73°W) during 197879 principally involved laboratory work on rock samples and map compilation of structural data. The samples and data were collected during the 197778 austral summer field season, when seven geologists Df the U.S. Geological Survey (usGs) completed reconnaissance geologic mapping of about 30,000 square kilometers of the southern Antarctic Peninsula. This fieldwork showed that the area mapped is underlain by a thick folded sequence of Middle and Upper Jurassic sedimentary rocks (Latady Formation) and interbedded volcanic rocks that are intruded by Upper Cretaceous calcalkaline plutons (Rowley, 1978). The Jurassic rocks represent deposition along the axis and margin of a magmatic arc that formerly occupied the present interior of the Antarctic Peninsula (Rowley and Williams, 1979). During 1978-79, K. S. Kellogg (usGs) compiled structural data and analyzed the paleomagnetism of the igneous rocks of the Orville Coast. He found that the folds are much like those in the Lassiter Coast to the northeast Kellogg and Rowley, 1974), but that, in the Orville Coast area, the folds are better exposed and thrust faults and high-angle faults can be observed. The trends of .he folds, which predate the Late Cretaceous plutonism, lefine an orocline across the area, and paleomagnetic ;tudies indicate that this oroclinal bend of the fold belt
Bushnell and C. Craddock. Antarctic Map Folio Series, folio 12, plate 3. New York: American Geographical Society. Mehnert, H. H., P. D. Rowley, and D. L. Schmidt. 1975. K-Ar ages of plutonic rocks on the Lassiter Coast area, Antarctica. Journal of Research of the U.S. Geological Survey, 3: 233-36.
Rowley, P. D. 1978. Geologic studies in Orville Coast and eastern Ellsworth Land, Antarctic Peninsula. Antarctic Journal of the United States, 13(4): 7-9.
Rowley, P. D., and P. L. Williams. In press. Geology of the northern Lassiter Coast and southern Black coast, Antarctic Peninsula. In Third Symposium on Antarctic Geology and Geophysics, ed. C. Craddock. Madison: University of Wisconsin
Press. Suarez, M. 1976. Plate tectonic models for southern Antarctic Peninsula and its relation to southern Andes. Geology, 4: 211-14.
Thomson, M. R. A., T. S. Laudon, and J . M. Boyles. 1978. Stratigraphical studies in Orville Coast and eastern Ellsworth Land. Antarctic Journal of the United States, 13(4): 9-10.
was formed after emplacement of the Upper Cretaceous plutons. The final report on the paleomagnetic data has been completed (Kellogg, 1979b). (For a summary of these data and conclusions on the structural compilation, see Kellogg, 1979a). A study of glacial erratics and striations by P. E. Carrara (usGs) disclosed that ice in the Orville Coast area formerly was more than 450 meters thicker than at present. The ice spread from a center near the present topographic divide of the southern Antarctic Peninsula, on the northern side of the field area. (For a summary of these data, see Carrara, 1979.) Samples from numerous evaporitic surface encrustations on rocks of the field area were studied by W. R. Vennum (Sonoma State University, California). He discovered an interesting array of minerals, five of which had not been reported previously from Antarctica (Vennum, 1979). A small stock of granodiorite, probably of Late Cretaceous age, which is exposed in the Sky-Hi Nunataks, was mapped in 1977-78 and was found to contain abundant pyrite, widespread hydrothermally altered rocks, and altered shear zones. The granodiorite exposures resemble those of the Upper Cretaceous Lassiter Coast porphyry-type copper deposit, located about 200 kilometers to the east-northeast (Rowley, Williams, and Schmidt, 1977). Preliminary analysis of semiquantitative spectrographic analyses indicates that the pyrite zone in the stock is low in metal additions (minor iron, copper, manganese, molybdenum, and lead), but that the veins locally contain high concentrations of copper, zinc, manganese and lead, as well as minor molybdenum, silver, and other metals. The occurrence seems to represent a noneconomic porphyry-type copper deposit. The exposures of plutonic rock may occur at the level of the outer pyrite zone of Rose (1970), inward from which may be a subsurface ore body of disseminated chalcopyrite. z'1
Small veins containing sulfides occur in older volcanic rocks elsewhere in the Sky-Hi Nunataks. These veins seem to represent peripheral veins that have extended outward from the stock. Future work on the stock is scheduled to include potassium-argon age dating of this and other plutons in the field area by Edward Farrar (Queen's University, Ontario), as well as petrographic work. Preliminary study of the invertebrate fossils from the Latady Formation by M. R. A. Thomson (British Antarctic Survey) indicates that Upper Jurassic (Tithonian) fossils are very abundant. The petrography of the clastic rocks of the Latady Formation is being done by T. S. Laudon (University of Wisconsin-Oshkosh). Laudon, Thomson, and J. M. Boyles (University of Texas at Austin) will expand on their preliminary field account by collaborating on research on the stratigraphy of the Latady Formation (Thomson, Laudon, and Boyles, 1978). In addition to the work on the geology of the Orville Coast and eastern Ellsworth Land, W. R. Vennum has completed electron-microprobe, petrographic, and chemical studies of some trachytes from Ross Island. The research studies described in this article have been supported by National Science Foundation grant DPP 76-12557. References
Carrara, P. E. 1979. Evidence of former, more extensive glacial
Evaporite encrustations and yellow and green surficial salts from Orville Coast and eastern Ellsworth Land WALTER R. VENNUM Department of Geology Sonoma State University Rohnert Park, California 94928
and
U.S. Geological Survey
Menlo Park, California 94025
During the past year, I have studied samples of evaporitic surface encrustations and surficial salts that were collected during the 1977-78 field season from numerous inland sites in the Orville Coast area and eastern Ellsworth Land. As summarized below, my results include identification of five minerals that previously had not been reported from Antarctica. Evaporite salts occurring as efflorescences, crusts, and thick stratified deposits have been reported from nu22
ice in the Orville Coast, Antarctic Peninsula. Antarctic Journal (this issue). Kellogg, K. S. 1979a. Structural geology of Orville Coast and eastern Ellsworth Land. Antarctic Journal of the United States (this issue). Kellogg, K. S. 1979b. New paleomagnetic evidence for oroclinal bending of the southern Antarctic Peninsula. Geological Society of America Bulletin, September issue. Kellogg, K. S., and P. D. Rowley. 1974. Structural geology of of the United States
the Lassiter Coast. Antarctic Journal of the United States, 9(5):
224-25. Rose, A. W. 1970. Zonal relations of wallrock alteration and sulfide distribution at porphyry copper deposits. Economic Geology, 65(8): 920-36. Rowley, P. D. 1978. Geologic studies in Orville Coast and eastern Ellsworth Land, Antarctic Peninsula. Antarctic Journal of the United States, 13(4): 7-9. Rowley, P. D. In press. Geology of the northern Lassiter Coast and southern Black Coast, Antarctic Peninsula. In Third Symposium on Antarctic Geology and Geophysics, ed. C. Craddock. Madison: University of Wisconsin Press. Rowley, P. D.., P. L. Williams, and D. L. Schmidt. 1977. Geology
of an Upper Cretaceous Copper Deposit in the Andean Province, Lassiter Coast, Antarctic Peninsula. U.S. Geological Survey
Professional Paper, no. 934. Thomson, M. R. A., T. S. Laudon, and J . M. Boyles. 1978. Stratigraphical studies in Orville Coast and eastern Ellsworth Land. Antarctic Journal of the United States, 13(4): 910. Vennum, W. R. 1979. Evaporite encrustations and yellow and green surficial salts from Orville Coast and eastern Ellsworth Land. Antarctic Journal of the United States (this issue).
merous locations along the Antarctic coastline (Gibson 1962; Hirabayashi and Ossaka, 1976; MacNamara anc Usselman, 1972; Morikawa et al., 1975; Nishiyama anc Kurasawa, 1975; McLeod, 1964; Toni et al., 1973). Cal cite, gypsum, thenardite, and mirabilite are the mos common minerals reported, although numerous mor 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 Reported occurrences of evaporite efflorescences an( crusts from the antarctic interior, where salt spray oi saline lake water cannot be a major contributing factor are scarce and consist of only a few samples (Tasch an( Angino, 1968; Cameron and Ford; Skidmore an Clarkson, 1972). The only minerals that have been re ported are gypsum, calcite, thenardite, mirabilite, an( hexahydrite. During the 1977-78 field season, white encrustation and yellow and green surficial salts were collected fron 72 sites scattered over an area of about 30,000 squan kilometers of the Orville Coast and eastern Ellswortl Land (74°-76°30'S164°-74°W). None of these encrusta tions and surficial salts were collected at sites closer t( the coast than 70 kilometers in the direction of the pre vailing northwest wind, and the majority of the sample were collected from sites lying at much greater distances As the majority of the sites lie south and east of th4 2,000-meter-high crest of the Antarctic Peninsula, thi
tonophysics, 37: 53-81.
Farrar, E., S. L. McBride, and P. D. Rowley. In press. Ages and tectonic implications of Andean plutonism in the southern
Antarctic Peninsula. In Third Symposium on Antarctic Geology and Geophysics, ed. C. Craddock. Madison: University of
Wisconsin Press. Herron, E. M., and B. E. Tucholke. 1976. Sea-floor magnetic patterns and basement structure in the southeastern Pacific. In Initial Report of the Deep Sea Drilling Project, 35: 263-78.
Washington, D.C.: U.S. Government Printing Office. Kellogg, K. S. 1979. New paleomagnetic evidence for oroclinal bending of the southern Antarctic Peninsula. Geological Society of America Bulletin, September issue. Kellogg, K. S., and P. D. Rowley. 1974. Structural geology of the Lassiter Coast. Antarctic Journal of the United States, 9: 224-25.
Laudon, T. S., L. L. Lackey, P. G. Quilty, and P. M. Ostway. 1969. Geology of eastern Ellsworth Land (sheet 3, eastern Ellsworth Land). In Geologic maps of Antarctica, eds. N. C.
Geologic studies in Orville Coast and eastern Ellsworth Land PETER D. ROWLEY
U.S. Geological Survey Denver, Colorado 80225
Studies of the geology of the Orville Coast and eastern Ellsworth Land (74°-76 030'S/65°-73°W) during 197879 principally involved laboratory work on rock samples and map compilation of structural data. The samples and data were collected during the 197778 austral summer field season, when seven geologists Df the U.S. Geological Survey (usGs) completed reconnaissance geologic mapping of about 30,000 square kilometers of the southern Antarctic Peninsula. This fieldwork showed that the area mapped is underlain by a thick folded sequence of Middle and Upper Jurassic sedimentary rocks (Latady Formation) and interbedded volcanic rocks that are intruded by Upper Cretaceous calcalkaline plutons (Rowley, 1978). The Jurassic rocks represent deposition along the axis and margin of a magmatic arc that formerly occupied the present interior of the Antarctic Peninsula (Rowley and Williams, 1979). During 1978-79, K. S. Kellogg (usGs) compiled structural data and analyzed the paleomagnetism of the igneous rocks of the Orville Coast. He found that the folds are much like those in the Lassiter Coast to the northeast Kellogg and Rowley, 1974), but that, in the Orville Coast area, the folds are better exposed and thrust faults and high-angle faults can be observed. The trends of .he folds, which predate the Late Cretaceous plutonism, lefine an orocline across the area, and paleomagnetic ;tudies indicate that this oroclinal bend of the fold belt
Bushnell and C. Craddock. Antarctic Map Folio Series, folio 12, plate 3. New York: American Geographical Society. Mehnert, H. H., P. D. Rowley, and D. L. Schmidt. 1975. K-Ar ages of plutonic rocks on the Lassiter Coast area, Antarctica. Journal of Research of the U.S. Geological Survey, 3: 233-36.
Rowley, P. D. 1978. Geologic studies in Orville Coast and eastern Ellsworth Land, Antarctic Peninsula. Antarctic Journal of the United States, 13(4): 7-9.
Rowley, P. D., and P. L. Williams. In press. Geology of the northern Lassiter Coast and southern Black coast, Antarctic Peninsula. In Third Symposium on Antarctic Geology and Geophysics, ed. C. Craddock. Madison: University of Wisconsin
Press. Suarez, M. 1976. Plate tectonic models for southern Antarctic Peninsula and its relation to southern Andes. Geology, 4: 211-14.
Thomson, M. R. A., T. S. Laudon, and J . M. Boyles. 1978. Stratigraphical studies in Orville Coast and eastern Ellsworth Land. Antarctic Journal of the United States, 13(4): 9-10.
was formed after emplacement of the Upper Cretaceous plutons. The final report on the paleomagnetic data has been completed (Kellogg, 1979b). (For a summary of these data and conclusions on the structural compilation, see Kellogg, 1979a). A study of glacial erratics and striations by P. E. Carrara (usGs) disclosed that ice in the Orville Coast area formerly was more than 450 meters thicker than at present. The ice spread from a center near the present topographic divide of the southern Antarctic Peninsula, on the northern side of the field area. (For a summary of these data, see Carrara, 1979.) Samples from numerous evaporitic surface encrustations on rocks of the field area were studied by W. R. Vennum (Sonoma State University, California). He discovered an interesting array of minerals, five of which had not been reported previously from Antarctica (Vennum, 1979). A small stock of granodiorite, probably of Late Cretaceous age, which is exposed in the Sky-Hi Nunataks, was mapped in 1977-78 and was found to contain abundant pyrite, widespread hydrothermally altered rocks, and altered shear zones. The granodiorite exposures resemble those of the Upper Cretaceous Lassiter Coast porphyry-type copper deposit, located about 200 kilometers to the east-northeast (Rowley, Williams, and Schmidt, 1977). Preliminary analysis of semiquantitative spectrographic analyses indicates that the pyrite zone in the stock is low in metal additions (minor iron, copper, manganese, molybdenum, and lead), but that the veins locally contain high concentrations of copper, zinc, manganese and lead, as well as minor molybdenum, silver, and other metals. The occurrence seems to represent a noneconomic porphyry-type copper deposit. The exposures of plutonic rock may occur at the level of the outer pyrite zone of Rose (1970), inward from which may be a subsurface ore body of disseminated chalcopyrite. z'1
Small veins containing sulfides occur in older volcanic rocks elsewhere in the Sky-Hi Nunataks. These veins seem to represent peripheral veins that have extended outward from the stock. Future work on the stock is scheduled to include potassium-argon age dating of this and other plutons in the field area by Edward Farrar (Queen's University, Ontario), as well as petrographic work. Preliminary study of the invertebrate fossils from the Latady Formation by M. R. A. Thomson (British Antarctic Survey) indicates that Upper Jurassic (Tithonian) fossils are very abundant. The petrography of the clastic rocks of the Latady Formation is being done by T. S. Laudon (University of Wisconsin-Oshkosh). Laudon, Thomson, and J. M. Boyles (University of Texas at Austin) will expand on their preliminary field account by collaborating on research on the stratigraphy of the Latady Formation (Thomson, Laudon, and Boyles, 1978). In addition to the work on the geology of the Orville Coast and eastern Ellsworth Land, W. R. Vennum has completed electron-microprobe, petrographic, and chemical studies of some trachytes from Ross Island. The research studies described in this article have been supported by National Science Foundation grant DPP 76-12557. References
Carrara, P. E. 1979. Evidence of former, more extensive glacial
Evaporite encrustations and yellow and green surficial salts from Orville Coast and eastern Ellsworth Land WALTER R. VENNUM Department of Geology Sonoma State University Rohnert Park, California 94928
and
U.S. Geological Survey
Menlo Park, California 94025
During the past year, I have studied samples of evaporitic surface encrustations and surficial salts that were collected during the 1977-78 field season from numerous inland sites in the Orville Coast area and eastern Ellsworth Land. As summarized below, my results include identification of five minerals that previously had not been reported from Antarctica. Evaporite salts occurring as efflorescences, crusts, and thick stratified deposits have been reported from nu22
ice in the Orville Coast, Antarctic Peninsula. Antarctic Journal (this issue). Kellogg, K. S. 1979a. Structural geology of Orville Coast and eastern Ellsworth Land. Antarctic Journal of the United States (this issue). Kellogg, K. S. 1979b. New paleomagnetic evidence for oroclinal bending of the southern Antarctic Peninsula. Geological Society of America Bulletin, September issue. Kellogg, K. S., and P. D. Rowley. 1974. Structural geology of of the United States
the Lassiter Coast. Antarctic Journal of the United States, 9(5):
224-25. Rose, A. W. 1970. Zonal relations of wallrock alteration and sulfide distribution at porphyry copper deposits. Economic Geology, 65(8): 920-36. Rowley, P. D. 1978. Geologic studies in Orville Coast and eastern Ellsworth Land, Antarctic Peninsula. Antarctic Journal of the United States, 13(4): 7-9. Rowley, P. D. In press. Geology of the northern Lassiter Coast and southern Black Coast, Antarctic Peninsula. In Third Symposium on Antarctic Geology and Geophysics, ed. C. Craddock. Madison: University of Wisconsin Press. Rowley, P. D.., P. L. Williams, and D. L. Schmidt. 1977. Geology
of an Upper Cretaceous Copper Deposit in the Andean Province, Lassiter Coast, Antarctic Peninsula. U.S. Geological Survey
Professional Paper, no. 934. Thomson, M. R. A., T. S. Laudon, and J . M. Boyles. 1978. Stratigraphical studies in Orville Coast and eastern Ellsworth Land. Antarctic Journal of the United States, 13(4): 910. Vennum, W. R. 1979. Evaporite encrustations and yellow and green surficial salts from Orville Coast and eastern Ellsworth Land. Antarctic Journal of the United States (this issue).
merous locations along the Antarctic coastline (Gibson 1962; Hirabayashi and Ossaka, 1976; MacNamara anc Usselman, 1972; Morikawa et al., 1975; Nishiyama anc Kurasawa, 1975; McLeod, 1964; Toni et al., 1973). Cal cite, gypsum, thenardite, and mirabilite are the mos common minerals reported, although numerous mor 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 Reported occurrences of evaporite efflorescences an( crusts from the antarctic interior, where salt spray oi saline lake water cannot be a major contributing factor are scarce and consist of only a few samples (Tasch an( Angino, 1968; Cameron and Ford; Skidmore an Clarkson, 1972). The only minerals that have been re ported are gypsum, calcite, thenardite, mirabilite, an( hexahydrite. During the 1977-78 field season, white encrustation and yellow and green surficial salts were collected fron 72 sites scattered over an area of about 30,000 squan kilometers of the Orville Coast and eastern Ellswortl Land (74°-76°30'S164°-74°W). None of these encrusta tions and surficial salts were collected at sites closer t( the coast than 70 kilometers in the direction of the pre vailing northwest wind, and the majority of the sample were collected from sites lying at much greater distances As the majority of the sites lie south and east of th4 2,000-meter-high crest of the Antarctic Peninsula, thi
