Geology of the volcanic rocks of the Ross Island area, Antarctica
work. It is our intention to continue this program into the region of 40° to 50°S. Contribution no. 180 of the Geosciences Division, University of Texas at Dallas. References Daiziel, I. W. D. 1970. Structural studies in the Scotia Arc: the Patagonian and Fuegian Andes. Antarctic Journal of the U.S., V(4) : 99-100. Halpern, M. 1962. Potassium-argon dating of plutonic bodies in Palmer Peninsula and southern Chile. Science, 138(3546): 1261-1262. Halpern, M. 1968. Ages of antarctic and Argentine rocks bearing on continental drift. Earth and Planetary Sciences Letters, 5(3): 159-167. Halpern, M. 1970. Hero Cruise 69-6. Antarctic Journal of the U.S., V(2) :44. Halpern, M. 1971. Evidence for Gondwanaland from a review of West Antarctic radiometric ages. In: Research in the Antarctic. American Association for the Advancement of Science. p. 717-730. Halpern, M. In press. Rubidium-strontium total rock and mineral ages from the Marguerite Bay area, Kohler Range, and Fosdick Mountains. In: Antarctic Geology and Geophysics. Oslo, Universitetsforlaget. Instituto de Investigaciones Geológicas. 1968. Mapa Geologico de Chile (escala 1: 1,000,000). Santiago, Chile. Levi, B., S. Mehech, and F. Munizaga. 1963. Edades radiométricas y petrografia de granitos Chilenos. Instituto de Investigaciones Geolcigicas. Boletin, 12. 42 p. Rex, D. C. In press. Potassium-argon age determinations on volcanic and associated rocks from the Antarctic Peninsula and Dronning Maud Land. In: Antarctic Geology and Geophysics. Oslo, Universitetsforlaget.
Marie Byrd Land and Ellsworth Land geologic survey F.
ALTON WADE
Department of Geosciences Texas Tech University During the past year, work has been progressing on the preparation of the report that will summarize the geology of coastal West Antarctica from Cape Colbeck, Edward VII Peninsula, on the west to the eastern margin of the Hudson Mountains in Ellsworth Land on the east. During three consecutive austral summers, 1966-1967, 1967-1968, and 1968-1969, data and specimens were recorded and collected respectively in the field for subsequent study and analysis. These data, combined with those acquired by this principal investigator during the Byrd Antarctic Expedition II, 1933-1935, and the U.S. Antarctic Service Expedition, 1939-1941, in Marie Byrd Land will all be used in the preparation of the report. Several preliminary reports have been published, and a general summary coauthored by Dr. John Wilbanks was presented by the principal investigator at the SCAR Symposium on Antarctic Geology and Solid Earth Geopiysics, Oslo, Norway, in August 1970. The paper will September—October 1971
be included in the symposium volume, which is now in press. Much work remains to be done, and the final report will not he finished until about August 1972. At present, full time is being devoted to the project by the principal investigator and two graduate research assistants, Carl Cathey and Jerry Oldham. All Cenozoic volcanics have been turned over to Dr. Wesley LeMasurier, University of Colorado at Denver, for study. He participated in the field program in 1967-1968 and has concentrated his studies on that aspect of the project and the Cretaceous volcanics. During June of this year a suite of rooms and a laboratory in the new Texas Tech University Museum were made available for our use. Following the move to the new facilities, work was resumed on June 25. Rock specimens, thin sections, maps, records, and still and moving pictures are being properly cataloged and stored. Through the generosity of Mrs. Paul A. Siple we acquired the Siple collection of antarctic rock specimens, most of which were from Marie Byrd Land. Mr. Gerry Pagano devoted much time and effort to packing and shipping these specimens to us. They will be thin-sectioned, cataloged, and properly stored. Another acquisition was a small collection of specimens collected by Herman Friis at the Japanese base area, Lützow-Holm Bay. He also donated many 2- by 2-in, transparencies of that sector to our collection. It will take many months to finish analyzing and cataloging the many hundreds of specimens, but it is our intent to make them available for study by any interested person.
Geology of the volcanic rocks of the Ross Island area, Antarctica SAMUEL B. TREVES
Department of Geology University of Nebraska and Institute of Polar Studies The Ohio State University Field work in the 1970-1971 season primarily concerned the geology of the summits of Mounts Erebus, Terror, Terra Nova, Bird (all on Ross Island) and Discovery (on the Scott Coast). Petrographic evaluation of thin sections of rocks and consideration of data collected at these locations show that the rocks and geology of the summit areas of the Ross Island area are very similar to the rocks and geology of the lower flanks and coastal areas of the Ross Island area volcanoes. The results of the study of the summit areas confirm the earlier established geologic history and sequence of eruptive events that was previously estab193
lished for the coastal and flank areas (Treves, 1962, 1965 5 1967 5 1968 5 1969 ) 1970, 1971). That sequence is olivine basalt, basalt, and trachyte, which is referred to as the older sequence, and a later sequence consisting of olivine basalt and basalt, which is referred to as the younger sequence. In the Ross Island area basalts are the most common type of rock, and trachytes are the second most common type. This feature is quite characteristic of oceanic islands and has been discussed in detail by Chayes (1963). Rarer rock types, such as limburgites, mugearites (?),and even rarer types, do occur but are not abundant. If the rarer types are excluded, the remaining trachytes, basalts, and pyroclastic rocks may be divided into seven types that are easily recognized and mapped. These types are the olivine-pyroxene basalt, plagioclase basalt, hornblende basalt, pyroxene trachyte, hornblende trachyte, anorthoclase trachyte, and the pyroclastic rocks. The pyroclastic rocks are mostly trachytic tuffs and volcanic breccias. Incomplete chemical data from many sources indicate that the rocks are all undersaturated, although nepheline has not been positively identified in any of the thin sections. Smith's classic paper (1954) on the specimens collected in 1910-1913 by members of the British Antarctic Expedition clearly established the nature of the assemblage, and my results and those of others confirm this early view. It seems clear that we are dealing with a typical alkaline-olivine basalt association that is typically and widely developed in ocean basins and on continents. This suite of rocks, however, stands in marked contrast to the tholeiitic Ferrar Dolerites and perhaps the Ferrar Volcanics of southern Victoria Land. The relationship of the Ross Island volcanic rocks to the many small vents of southern Victoria Land, such as the Brando vent of the Radian Glacier area and the vents of Taylor Valley, is not clear. Some of the petrographic and chemical data suggest that some of them are related to the Ross Island suite. As a result of the work done in this and subjacent areas by the writer and others it is now possible to suggest that the Ross Island volcanic province is part of a larger province that stretches from the McMurdo Sound area north along the coast of southern Victoria Land through Cape Adare to the Balleny Islands. Future work in the Ross Island area will be concerned with the micromineralogy of the rocks and their relationship to other nearby volcanic centers and to the other centers of the Ross Island province. References Chayes, F. 1963. Relative abundance of intermediate members of the oceanic basalt-trachyte association. Journal of Geophysical Research, 68: 1519-1534. Smith, W. C. 1954. The Volcanic Rocks of the Ross Archipelago. London, British Museum. 107 p.
194
Treves, S. B. 1962. The geology of Cape Evans and Cape Royds, Ross Island, Antarctica. American Geophysical Union. Geophysical Monograph, 7: 40-46. 1965. Volcanic rocks of Ross Island. U.S. Antarctic Projects Officer. Bulletin, VI(7) : 58-60. 1967. Volcanic rocks from the Ross Island, Marguerite Bay, and Mt. Weaver areas, Antarctica. JARE Scientific Reports, 1: 136-149. ________ 1968. Volcanic rocks of the Ross Island area. Antarctic Journal of the U.S., 111(4): 108-109. _____ 1969. Volcanic rocks of the Ross Island area. Antarctic Journal of the U.S., IV(5) : 207-208. 1970. Volcanic rocks of the Ross Island area. Antarctic Journal of the U.S., V(4) : 103. 1971. Geology of the summit areas of volcanoes of the Ross Island province, Antarctica (abstract). Geological Society of America. North-Central Section Meeting, Lincoln, Nebraska, p. 283-284.
Ida Granite: a new formation of the Granite Harbour Intrusives, Beardmore Glacier region JOHN GUNNER
Institute of Polar Studies and Department of Geology The Ohio State University The name Ida Granite is given to intrusions of aplitic quartz monzonite and granite (Williams et al., 1954) and associated aplite and tourmaline-bearing pegmatite dikes typically exposed at Mount Ida and Granite Pillars on the west side of the lower Beardmore Glacier (see fig.; Lindsay et al., in press). The main intrusion of Ida Granite in this area has the form of a stock with steep marginal contacts and a roof apparently exposed at Granite Pillars. The rock is typically light gray, fine- to medium-grained, and nonporphyritic. Patches of pegmatitic tourmaline-bearing material about 5 cm across occur in places, notably at Granite Pillars, and scattered euhedral grayish-blue phenocrysts of plagioclase are present in some localities. In thin section the Ida Granite typically has an aplitic or granitoid fabric consisting of microcline, quartz, and plagioclase with accessory biotite and/or muscovite and trace amounts of epidote, magnetite, sphene, and zircon. The Ida Granite contrasts strongly in texture, mineralogy (table 1), and chemistry (table 2) with the Hope Granite (Gunn and Walcott, 1962) that surrounds it. The Hope Granite is typically coarser grained, contains more abundant phenocrysts and xenoliths, and is richer in calcium, magnesium, and total iron and poorer in silica (table 2) than the Ida Granite. ANTARCTIC JOURNIL
Marie Byrd Land and Ellsworth Land geologic survey F.
ALTON WADE
Department of Geosciences Texas Tech University During the past year, work has been progressing on the preparation of the report that will summarize the geology of coastal West Antarctica from Cape Colbeck, Edward VII Peninsula, on the west to the eastern margin of the Hudson Mountains in Ellsworth Land on the east. During three consecutive austral summers, 1966-1967, 1967-1968, and 1968-1969, data and specimens were recorded and collected respectively in the field for subsequent study and analysis. These data, combined with those acquired by this principal investigator during the Byrd Antarctic Expedition II, 1933-1935, and the U.S. Antarctic Service Expedition, 1939-1941, in Marie Byrd Land will all be used in the preparation of the report. Several preliminary reports have been published, and a general summary coauthored by Dr. John Wilbanks was presented by the principal investigator at the SCAR Symposium on Antarctic Geology and Solid Earth Geopiysics, Oslo, Norway, in August 1970. The paper will September—October 1971
be included in the symposium volume, which is now in press. Much work remains to be done, and the final report will not he finished until about August 1972. At present, full time is being devoted to the project by the principal investigator and two graduate research assistants, Carl Cathey and Jerry Oldham. All Cenozoic volcanics have been turned over to Dr. Wesley LeMasurier, University of Colorado at Denver, for study. He participated in the field program in 1967-1968 and has concentrated his studies on that aspect of the project and the Cretaceous volcanics. During June of this year a suite of rooms and a laboratory in the new Texas Tech University Museum were made available for our use. Following the move to the new facilities, work was resumed on June 25. Rock specimens, thin sections, maps, records, and still and moving pictures are being properly cataloged and stored. Through the generosity of Mrs. Paul A. Siple we acquired the Siple collection of antarctic rock specimens, most of which were from Marie Byrd Land. Mr. Gerry Pagano devoted much time and effort to packing and shipping these specimens to us. They will be thin-sectioned, cataloged, and properly stored. Another acquisition was a small collection of specimens collected by Herman Friis at the Japanese base area, Lützow-Holm Bay. He also donated many 2- by 2-in, transparencies of that sector to our collection. It will take many months to finish analyzing and cataloging the many hundreds of specimens, but it is our intent to make them available for study by any interested person.
Geology of the volcanic rocks of the Ross Island area, Antarctica SAMUEL B. TREVES
Department of Geology University of Nebraska and Institute of Polar Studies The Ohio State University Field work in the 1970-1971 season primarily concerned the geology of the summits of Mounts Erebus, Terror, Terra Nova, Bird (all on Ross Island) and Discovery (on the Scott Coast). Petrographic evaluation of thin sections of rocks and consideration of data collected at these locations show that the rocks and geology of the summit areas of the Ross Island area are very similar to the rocks and geology of the lower flanks and coastal areas of the Ross Island area volcanoes. The results of the study of the summit areas confirm the earlier established geologic history and sequence of eruptive events that was previously estab193
lished for the coastal and flank areas (Treves, 1962, 1965 5 1967 5 1968 5 1969 ) 1970, 1971). That sequence is olivine basalt, basalt, and trachyte, which is referred to as the older sequence, and a later sequence consisting of olivine basalt and basalt, which is referred to as the younger sequence. In the Ross Island area basalts are the most common type of rock, and trachytes are the second most common type. This feature is quite characteristic of oceanic islands and has been discussed in detail by Chayes (1963). Rarer rock types, such as limburgites, mugearites (?),and even rarer types, do occur but are not abundant. If the rarer types are excluded, the remaining trachytes, basalts, and pyroclastic rocks may be divided into seven types that are easily recognized and mapped. These types are the olivine-pyroxene basalt, plagioclase basalt, hornblende basalt, pyroxene trachyte, hornblende trachyte, anorthoclase trachyte, and the pyroclastic rocks. The pyroclastic rocks are mostly trachytic tuffs and volcanic breccias. Incomplete chemical data from many sources indicate that the rocks are all undersaturated, although nepheline has not been positively identified in any of the thin sections. Smith's classic paper (1954) on the specimens collected in 1910-1913 by members of the British Antarctic Expedition clearly established the nature of the assemblage, and my results and those of others confirm this early view. It seems clear that we are dealing with a typical alkaline-olivine basalt association that is typically and widely developed in ocean basins and on continents. This suite of rocks, however, stands in marked contrast to the tholeiitic Ferrar Dolerites and perhaps the Ferrar Volcanics of southern Victoria Land. The relationship of the Ross Island volcanic rocks to the many small vents of southern Victoria Land, such as the Brando vent of the Radian Glacier area and the vents of Taylor Valley, is not clear. Some of the petrographic and chemical data suggest that some of them are related to the Ross Island suite. As a result of the work done in this and subjacent areas by the writer and others it is now possible to suggest that the Ross Island volcanic province is part of a larger province that stretches from the McMurdo Sound area north along the coast of southern Victoria Land through Cape Adare to the Balleny Islands. Future work in the Ross Island area will be concerned with the micromineralogy of the rocks and their relationship to other nearby volcanic centers and to the other centers of the Ross Island province. References Chayes, F. 1963. Relative abundance of intermediate members of the oceanic basalt-trachyte association. Journal of Geophysical Research, 68: 1519-1534. Smith, W. C. 1954. The Volcanic Rocks of the Ross Archipelago. London, British Museum. 107 p.
194
Treves, S. B. 1962. The geology of Cape Evans and Cape Royds, Ross Island, Antarctica. American Geophysical Union. Geophysical Monograph, 7: 40-46. 1965. Volcanic rocks of Ross Island. U.S. Antarctic Projects Officer. Bulletin, VI(7) : 58-60. 1967. Volcanic rocks from the Ross Island, Marguerite Bay, and Mt. Weaver areas, Antarctica. JARE Scientific Reports, 1: 136-149. ________ 1968. Volcanic rocks of the Ross Island area. Antarctic Journal of the U.S., 111(4): 108-109. _____ 1969. Volcanic rocks of the Ross Island area. Antarctic Journal of the U.S., IV(5) : 207-208. 1970. Volcanic rocks of the Ross Island area. Antarctic Journal of the U.S., V(4) : 103. 1971. Geology of the summit areas of volcanoes of the Ross Island province, Antarctica (abstract). Geological Society of America. North-Central Section Meeting, Lincoln, Nebraska, p. 283-284.
Ida Granite: a new formation of the Granite Harbour Intrusives, Beardmore Glacier region JOHN GUNNER
Institute of Polar Studies and Department of Geology The Ohio State University The name Ida Granite is given to intrusions of aplitic quartz monzonite and granite (Williams et al., 1954) and associated aplite and tourmaline-bearing pegmatite dikes typically exposed at Mount Ida and Granite Pillars on the west side of the lower Beardmore Glacier (see fig.; Lindsay et al., in press). The main intrusion of Ida Granite in this area has the form of a stock with steep marginal contacts and a roof apparently exposed at Granite Pillars. The rock is typically light gray, fine- to medium-grained, and nonporphyritic. Patches of pegmatitic tourmaline-bearing material about 5 cm across occur in places, notably at Granite Pillars, and scattered euhedral grayish-blue phenocrysts of plagioclase are present in some localities. In thin section the Ida Granite typically has an aplitic or granitoid fabric consisting of microcline, quartz, and plagioclase with accessory biotite and/or muscovite and trace amounts of epidote, magnetite, sphene, and zircon. The Ida Granite contrasts strongly in texture, mineralogy (table 1), and chemistry (table 2) with the Hope Granite (Gunn and Walcott, 1962) that surrounds it. The Hope Granite is typically coarser grained, contains more abundant phenocrysts and xenoliths, and is richer in calcium, magnesium, and total iron and poorer in silica (table 2) than the Ida Granite. ANTARCTIC JOURNIL
