Geological expedition to King Edward VII Peninsula and the , BRUCE P. LUYENDYK and CHRISTINE H. SMITH, Institute for Crustal Studies, University of California, Santa Barbara, California 93106

ng Edward VII Peninsula, western Marie Byrd Land, is a ern Ford Ranges were also made. Field research was support- Kargely ice-covered, domal feature containing the sparsely ed by the seventh German National Antarctic Expedition exposed and widely separated rock outcrops of the Rocke- (GANOVEX VII), operating off the Norwegian-registered, ice- feller and Alexandra Mountains and outlying nunataks (figure strengthened ship, Polar Queen. 1). The primary objectives for the 1992-1993 season on King Geophysical program: Echo sounding from Polar Edward VII Peninsula were to extend gravity coverage over Queen apparent gravity features detected in an earlier survey (Beitzel 1972); to obtain samples for paleomagnetic study to augment he Polar Queen traversed to Marie Byrd Land from Gond- existing data from the northern Ford Ranges in Marie Byrd Twana Station on the west side of the , avoiding ice Land (Cisowski and Luyendyk 1991); and to explore the rela- pack seen on real-time satellite imagery. The ship rounded tionship between the Fosdick Metamorphic Complex (Smith Cape Colbeck and entered southwest Sulzberger Bay in mid- 1992) of northern Marie Byrd Land and the Alexandra Com- December 1992. Patchy pack ice in the bay at that time was plex of King Edward VII Peninsula (Adams et al. 1989). Ancil- negotiable by the ice-strengthened ship. By the first week of lary observations of glacial and volcanic features in the north- January, the bay was virtually ice-free. No pack ice was seen on 8 January 1993 during helicopter flights to the Guest

Iff Peninsula some 150 kilometers (km) northeast of King Edward VII Peninsula. The flight altitude of 1,000 meters (m) allowed complete visibility of all of Sulzberger Bay. We obtained echo soundings controlled by global posi- / FORD RANGES tioning system (GPS) during the voyage from the eastern Ross Sea into Sulzberger Bay and on the return trip. Approximately 120 km of soundings were taken immediately west of llthOm$ Sulzberger Basin (figure 2). We merged these data with data 4tcheI Plc Ab from the Deep Freeze 83 cruise and a 1961-1962 Defense Billboard 0-k GUEST PENINSULA Mapping Agency cruise with the aim of producing an updated SGER ICE SlcELF. Mw preliminary bathymetric map. Preliminary interpretations are that the floor of the eastern Ross Sea is smooth and rolling,

5,. becoming more rugged near the Bay of Whales, where irregu- - _a5. x McKinley Pk lar bed forms with 10-m amplitudes are found. The profiles 0 Oioo . fathoms -, suggest that there may be a northeast-tilted fault block south- SULZ EAGER BAY west of Colbeck Basin and that the basin itself could be an

ScottNtic/ ,. ALEXANDRA asymmetric graben faulted on its northeast side. Shirase Bank - c. MThIS appears fault-controlled, as does the bank west of Sulzberger Basin. Short-wavelength, two-dimensional bedforms with EDWARD VII uncertain trends are apparent in places on the bank tops. A Lmcna.ro, PENINSULA trough of possible glacial origin was located between Colbeck -: ROCKEFLER MIND BK Basin and Shirase Bank; echoes from the floor of Saunders Tm,naotPeak Basin are suggestive of glacial deposits (figure 2), consistent with the bottom sampling results here (Anderson 1983). This ROSS SEA trough may have been carved by the Hammond and Boyd glaciers.

Figure 1. Geographical features, including mountain ranges, glaciers, Geophysical program: Gravityproffles ice shelves, and gross bathymetry of the continental margin in the wo on-ice gravity profiles were made by helicopter (figure eastern Ross Sea and off western Marie Byrd Land (100, 500, 1,000 T 1). These comprise 30 stations made with LaCoste and fathom contours). From Defense Mapping Agency JNC-1 24, ed. 2. Romberg meter number 141. A tie was made to the gravity The region is covered by 1:250,000 geologic maps (Wade, Cathey, and Oldham 1977a, 1977b, 1977c; 1978). Sampling locations for base at the German Gondwana Station at Terra Nova Bay in geochronology are marked by circles. The two gray lines over King the western Ross Sea. Position control was by differential GPS Edward VII Peninsula are the location of gravity profiles. using two Magellan 5000 Pro units. Both carrier phase-differ-

ANTARCTIC JOURNAL - REVIEW 1993 10

IAFTER ANDERSON, 1983 Mountains. Byrd Coast Gran- o 10 20 30 40 5060 ite is ubiquitous throughout CONTOURS IN HUNDREDS OF METERS I I I I I I I the Ford Ranges, the Ruppert NAUTICAL MILE:s ICE FRONT Coast to the north (Bradshaw 30 et al. 1991), and on the King MOUNTAINS G L A C I E R S 2% 5 4 GROUNDING LINE Edward VII Peninsula. Ford Granodiorite does not crop 15.W out south of the Denfield .30-. 76 76S Mountains in the Ford Ranges 10------15 0W GUEST PENINSULA and may extend north to the / Ruppert Coast. SULZBERGSR BANK Metamorphic roof pen- H IRASE -6 ( dants and contact metamor- POLARQUEEN BANK phosed sediments (Swanson ROSS Formation?) occur within the SEA L granitic batholith of the Rock- 77S 77S tic, efeller Mountains (Adams et 12 10 160 SAUNDERS al. 1989). A progression of 18 BASIN • 0 - . -.SULZBERGEF -. •• %• metamorphic grade within - BASIN L Swanson Formation sedimen- Li (CO1BECK L2 T. BASIN tary rock of King Edward VII I ALEXANDRA MTNS Peninsula is observed from the I•::?\ more distant low greenschist - : EDWARD VII ,- .•.., N grade argillaceous rocks of PENINSULA ROSS ICE SHELF \ ROCKEFELLER MTNS Clark Peak and La Gorce Peak in the Alexandra Mountains, through the andalusite-slates Figure 2. Map from Anderson (1983) of bathymetry from Deep Freeze 83, in the vicinity of King Edward of Drummond Peak, to the VII Peninsula and Sulzberger Bay. The tracks of the Polar Queen are labeled. garnet zone(?) metamorphic rocks of Mount Nilsen and ential and field-differential solutions were computed. Ice Breckinridge Peak further south in the central parts of the thickness was measured on site by portable radar echo sound- Rockefeller Mountains batholith. ing. The data are being combined with the 1966-1967 gravity In contrast, high-temperature gneisses and migmatites survey of Beitzel (1972) to produce a gravity map for King occur in the Alexandra Mountains on the north side of King Edward VII Peninsula and the Ford Ranges. The profile lead- Edward VII Peninsula. The rocks show close similarities in ing south from Scott Nunatak exhibits a 50 to 60 milliGals protolith (pelitic/psammitic) and metamorphic grade (high- (mGal) bouguer low over the Butler Glacier, a reading that is est amphibolite to granulite) with the much larger Fosdick due to either low-density sediments under the glacier or metamorphic complex in the northern Ford Ranges (Smith underestimation of the ice thickness for the bouguer correc- 1992). The Fosdick metamorphic complex was studied during tion. The profile leading north from the Rockefeller Mountains the Ford Ranges crustal exploration (FORCE) project of the shows an increase of nearly 50 mGals in bouguer gravity over 1989-1990 and 1990-1991 seasons (Luyendyk et al. 1992). It Sulzberger Bay; this is also seen in the data of Beitzel (1972) has Late Cretaceous argon-40/argon-39 (40Ar/39Ar) cooling and suggests thinner crust under the bay. The gravity gradient ages (Richard et al. in press). Together, the Fosdick and and topographic trends here suggest structural control for the Alexandra mountains exposures constitute the only high- edge of the peninsula north of the Alexandra Mountains. grade metasedimentary rocks in Marie Bird Land. A detailed Geological program: Geologic setting of western Marie petrological comparison of the two localities is underway. Byrd Land Geological program: Uranium-lead and utcrops in the region comprise Early Paleozoic low-grade paleomagnetic sampling O metasedimentary rocks of the Swanson Formation amples for uranium-lead (U-Pb) geochronology were col- (Bradshaw, Andrews, and Field 1983; Adams 1986) and Late Slected from five locations. K-feldspar granites of the Byrd Paleozoic and Mesozoic intrusive rocks of the Ford Granodi- Coast Granite intrusive suite were collected from the southern orite and Byrd Coast Granite (Weaver, Bradshaw, and Adams Ford Ranges at Mount Douglass and the Billboard in the 1991). Exposures of gneiss, schist, and migmatite occur in the Sarnoff Mountains. Comparable rocks from the northern Ford Fosdick Mountains in the northern Ford Ranges and Alexan- Ranges are 103-105 million years old (D. Kimbrough unpub- dra Mountains on King Edward VII Peninsula (Adams and lished data 1992). Garnet- muscovite -biotite granite was col- Weaver 1990; Smith 1992). Late Cenozoic volcanic rocks lected from Mackey Rock south of the western Fosdick Moun- (LeMasurier and Wade 1990) are restricted to the Fosdick tains; similar rocks from Neptune Nunataks and the Chester

ANTARCTIC JOURNAL - REVIEW 1993 11 Mountains from U-Pb zircon ages of 240 million years volcanic flow breccias ranges from less than 1 centimeter (Richard et al. in press). U-Pb samples were also taken at Scott (cm) to more than 10 cm; successive flows are generally 1-3 m Nunatak and Tennant Peak. Oriented samples of Byrd Coast thick. Ultramafic nodules are present within basal flows. Granite for paleomagnetic study were obtained from Mount Observations of gneissic rocks associated with the breccias Bowman and Clark Peak in the Alexandra Mountains near the were ambiguous; some gneissic xenoliths may occur within Butler Glacier (figure 1), Washington Ridge, Tennant Peak, and the flows. Sparse occurrence of gneissic fragments (ice-trans- Breckinridge Peak in the Rockefeller Mountains, Mount Grace ported?) resting upon the volcanic rock may indicate that a McKinley (McKinley Peak), and Mount Douglass (figure 1). slightly higher ice level existed at some postvolcanic stage. Geological program: Geology of Scott Nunatak Geological program: Glacial geology ield observations revealed a fundamental contrast in pro- laciated summit plateaus are present throughout the Ftolith between the adjacent Scott Nunatak and Prestrud Gregion mostly at 700-800 m above mean sea level, but Rock. Scott Nunatak consists of migmatized psammitic- ranging up to 1,100 m. These constitute a strongly dissected pelitic gneisses with a peak metamorphic assemblage of gar- uplifted peneplain (van der Wateren personal communica- net-hypersthene-sillimanite-plagioclase -quartz -biotite. Cor- tion). In the northern Ford Ranges, the plateau has glacial dierite is locally present. Spinel occurrence indicates that striations indicating glacial flow from south to north in con- metamorphic grade is slightly higher than in the Fosdick trast to present flow from east to west. Glacial erratics support metamorphic complex (Smith 1992) in the northern Ford an interpretation of different transport directions in the past Ranges. In contrast, Prestrud Rock, separated from the base of as do striation data (Richard and Luyendyk 1991). Swanson Scott Nunatak by a narrow ice ramp and bergschrund, con- Formation erratics are seen in the Fosdick and Chester moun- sists largely of granodioritic gneiss. An enclave or septa of tains. These are interpreted to have been transported from metasedimentary rock within the granodioritic gneiss has a the south because the Swanson Formation crops out only in biotite- quartz- plagioclase assemblage. Based on lithologic the southern Ford Ranges and King Edward VII Peninsula. and metamorphic contrast between Prestrud Rock and Scott Volcanism occurred during glaciation in the Fosdick Nunatak, a fault (down to the north) is inferred to separate Mountains. Mount Perkins is a stratovolcano atop the summit the two outcrops. Another structural break probably sepa- plateau in the eastern Fosdick Mountains and dates from 1.4 rates the migmatites of the Alexandra Complex and the low million years ago (40Ar/39Ar age by W. McIntosh). It is subaer- greenschist-grade metasediments of the Swanson Formation ial, as far as can be seen, and it is glacially eroded on its sides. in Clark Peak 37 km to the south. Lavas overlie glacial moraines at several locations in the Fos- dick Mountains. A basaltic cinder cone, north of Mount Avers, Geological program: Northern Ford Ranges sits atop or at the south edge of the Balchen Glacier and does e (along with F.M. van der Wateren) returned by heli- not appear to be substantially eroded, implying continued Wcopter to remote localities of the Fosdick, Chester, and volcanism after the last glacial maximum. Sarnoff mountains in the northern Ford Ranges. Mitchell A summit plateau and terrace landscape in the Alexandra Peak, a solitary nunatak on the Guest Peninsula, consists of and Rockefeller mountains at roughly the same elevations as garnet-sillimanite- cordierite migmatite and associated anate- that in the Ford Ranges appears to be almost completely ctic granitoid intrusions. The summit plateau of Marujupu buried beneath ice and snow. Ice-free nunataks are much less Peak in the Fosdick Mountains presents a glaciated surface of elevated above the present ice surface than in the northern uniform elevation; we interpret that the summit was dissect- Ford Ranges. Striations on ice-free nunataks define a drainage ed by downcutting of the Ochs Glacier streams, which flank pattern quite similar to the present radial one. We assume Marujupu Peak on both sides. The western Chester Moun- that it dates from the Last Glacial Maximum (isotopic stage 2; tains consist of highly fractured and hydrothermally(?) altered 24,000-12,000 years old), overprinting and destroying any Ford Granodiorite. East-west glacial striations in the lower older overriding evidence (van der Wateren, Luyendyk, and parts of the western Chester Mountains are compatible with Smith unpublished data). present-day glacier flow directions. This work was supported by National Science Founda- Basaltic flows were deposited upon glaciated topography tion grant OPP 88-17615 to B. Luyendyk. Thanks go to expedi- on the summit of Mount Avers in the central Fosdick Moun- tion leader Norbert Roland and members of the German tains (76°40S 145°35W). The flows drape the summit slope 1992-1993 GANO\TEX VII expedition, to representatives of (approximately 250 slope) from an elevation of approximately ItaliAntartide, to Reiber Shipping, to the crew of Polar Queen 1,048 m to 1,005 m. No glacial striations upon bedrock could (Norway), to Helicopter Resources (Australia), and to field be found. Deposits consist of autobrecciated flow rocks, red- guides M. Conway and B. Stait (New Zealand). F.M. van der dish brown scoria, volcanic bombs, and ropy-textured vol- Wateren participated in the glacial geology observations. canic glass. They are typically red-oxidized, with rare yellow Gunther Druivenga made the radar ice thickness measure- discoloration from hydrothermal(?) alteration. Flow breccias ments in support of the gravity survey. (Contribution 0149- are clast-supported, made up of glassy, angular to rounded 36TC of the Institute for Crustal Studies.) vesicular lava fragments. Size of glass fragments within the

ANTARCTIC JOURNAL - REVIEW 1993 12 References LeMasurier and J.W. Thomson (Eds.), Volcanoes of the antarctic plate and southern oceans (Antarctic Research Series, Vol. 48). Adams, C.J. 1986. Geochronological studies of the Swanson Forma- Washington, D.C.: American Geophysical Union. tion of Marie Byrd Land, West , and correlation with Luyendyk, B.P., S.M. Richard, C.H. Smith, and D.L. Kimbrough. 1992. Northern , East Antarctica, and South Island, New Geological and geophysical investigations in the northern Ford Zealand. New Zealand Journal of Geology and Geophysics, 29, Ranges, Marie Byrd Land, West Antarctica. In Y. Yoshida, K. 345-358. Kaminuma, and K. Shiraish (Eds.), Recent progress in antarctic Adams, C.J., P. Broady, P.J. Cleary, and S.D. Weaver. 1989. Geological earth science. Tokyo: Terra Scientific. and biological expedition to Edward VII Peninsula, Marie Byrd Richard, S.M., and B.P. Luyendyk. 1991. Glacial flow reorientation in Land, West Antarctica-1987/88: Field observations and initial the southwest Fosdick Mountains, Ford Ranges, Marie Byrd Land. results. New Zealand Antarctic Record, 9(2), 5-34. Antarctic Journal of the U.S., 26(5), 67-69. Adams, C.J., and S.D. Weaver. 1990. Age and correlation of metamor- Richard, S.M., C.H. Smith, D.L. Kimbrough, P.G. Fitzgerald, B.P. phic basement in Edward VII Peninsula Marie Byrd Land, West Luyendyk, and M.O. McWilliams. In press. Cooling history of the Antarctica, and correlation with Northern Victoria Land and northern Ford Ranges, Marie Byrd Land, West Antarctica. Tecton- Southern New Zealand. Zentralblatt für Geologie und Paläontolo- ics. gie, 1(112), 75-86. Smith, C.H. 1992. Metapelites and migmatites at the granulite facies Anderson, J.B. 1983. Preliminary results of the Deep Freeze 1983 pis- transition, Fosdick metamorphic complex, Marie Byrd Land, West ton-coring program. Antarctic Journal of the U.S., 18(5), 157-158. Antarctica. In Y. Yoshida, K. Kaminuma, and K. Shiraish (Eds.), Beitzel, J.E. 1972. Geophysical investigations in Marie Byrd Land, Recent progress in antarctic earth science. Tokyo: Terra Scientific. Antarctica. (Unpublished Ph.D. thesis, University of Wisconsin.) van der Wateren, F.M. 1993. Personal communication. Bradshaw, J.D., P.B. Andrews, and B.D. Field. 1983. Swanson Forma- Wade, F.A., C.A. Cathey, and J.B. Oldham. 1977a. Reconnaissance tion and related rocks of Marie Byrd Land and a comparison with geologic map of the Guest Peninsula quadrangle, Marie Byrd the Robertson Bay Group of Northern Victoria Land. In R.L. Oliver, Land, Antarctica. USARP: Antarctic Geologic Map, A-7. P.R. James, and J.B. Jago (Eds.), Antarctica earth science. Canberra: Wade, F.A., C.A. Cathey, and J.B. Oldham. 1977b. Reconnaissance Australian Academy of Science. geologic map of the quadrangle, Marie Byrd Land, Bradshaw, J.D., I.W.D. Daiziel, V. DiVenere, S.B. Mukasa, R.B. Antarctica. USARP: Antarctic Geologic Map, A-6. Pankhurst, B.C. Storey, and S.D. Weaver. 1991. The southern rim Wade, F.A., C.A. Cathey, and J.B. Oldham. 1977c. Reconnaissance of the Pacific: New work on the pre-Cenozoic rocks of Marie Byrd geologic map of the Alexandra Mountains quadrangle, Marie Byrd Land. In Abstracts-Sixth International Symposium on Antarctic Land, Antarctica. USARP: Antarctic Geologic Map, A-5. Earth Sciences, 9-13 September, 1991. Tokyo: National Institute for Wade, F.A., C.A. Cathey, and J.B. Oldham. 1978. Reconnaissance geo- Polar Research. logic map of the Gutenko Nunataks quadrangle, Marie Byrd Land, Cisowski, S., and B.P. Luyendyk. 1991. Paleomagnetic study of Antarctica. USARP: Antarctic Geologic Map, A- 11. igneous and metamorphic rocks from the Ford Ranges, Marie Weaver, S.D., J.D. Bradshaw, and C.J. Adams. 1991. Granitoids of the Byrd Land, West Antarctica. EOS, Transactions of the American Ford Ranges, Marie Byrd Land, Antarctica. In M.R.A. Thomson, Geophysical Union, 72(44), 129. J.A. Crame, and J.W. Thomson (Eds.), Geological evolution of LeMasurier, W.E., and F.A. Wade. 1990. Fosdick Mountains. In W.E. Antarctica. Cambridge: Cambridge University Press.

Mount Erebus Volcano Observatory: Seismic observations MICHAEL J. SKov and PHILIP R. KYLE, Department of Geoscience, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801

eismometers were first deployed on Mount Erebus in ital data-acquisition system, providing, for the first time, the S 1973; the first successful observations were made in 1974, ability to transfer seismic data from Mount Erebus to the however, using an array of seismometers installed within 1 United States daily. Prior to the installation of the digital data- kilometer (km) of the lava lake (Kyle et al. 1982). A permanent acquisition system, seismic data could be retrieved only dur- seismic network was established during the 1980-1981 field ing the austral summer months when flights off the ice are season as part of the International Mount Erebus Seismic possible. Study (IMESS) (Rowe and Kienle 1986). The network has also The network currently consists of six, short-period, verti- included nonseismic instrumentation, including an induction cal-component seismometers arranged into two triangles. loop to examine the emission of electrically charged gases One triangle is located around the summit region; the second, and infrasonic detectors to capture explosion events (Dibble lower on the mountain. These stations employ very-high-fre- etal. 1984). quency radio-telemetry to transmit data to the recording sys- During the 1992-1993 field season, major changes were tem at McMurdo Station. A seventh station is temporarily made to the Mount Erebus seismic monitoring system. Prior located in McMurdo and is wired directly to the data logger. to this field season, the seismic data was radio-te!emetered to The digital recording system is based on a design by a New Zealands Scott Base where it was recorded on an analog, group within the International Association of Seismology and multichannel, magnetic tape recorder (Kienle et al. 1981). Physics of the Earths Interior (IASPEI). This design employs a This system was replaced by a personal-computer based, dig- 16-channel, 12-bit analog-to-digital converter and event-trig-

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