Geologic Survey of Marie Byrd Land Million Years

References 6. There were widespread intrusions of granitic Faure, G., C. H. Shultz, and R. H. Carwile. 1971. Isotope plutons during the entire Cretaceous period with composition of strontium in volcanic rocks from Deception activity at a maximum in mid-Cretaceous time. These Island. Antarctic Journal of the U.S., VI(5): 197-198. plutons are exposed in Edward VII Peninsula, Ford Gast, P. W. 1967. Isotope geochemistry of volcanic rocks. In: Basaltc: the Poldervaart Treatise on Rocks of Basaltic Ranges, Kohler Mountains, and Bear Island. New Composition, Vol. 1. New York, Interscience Publishers, potassium-argon age determinations that supplement 325-358. those already published (Boudette et al., 1966; Wade, 1969; Halpern, 1968, in press) are listed in the table. 7. The Cenozoic period is characterized by periodic eruptions of alkali basalt and pyroclastics. This vol- canic activity has continued for approximately 50 Geologic survey of Marie Byrd Land million years. The advent of glaciation was early in F. ALTON WADE the period and, according to LeMasurier (1972), has continued without significant deglaciation since The Museum Eocene time. Texas Tech University The insular units that comprise this portion of Detailed studies and analyses of the rock specimens Antarctica are of continental crustal material. It is from Marie Byrd Land and of the field data recorded believed that they were at one time united with the during the field seasons 1966-1967 and 1967-1968 East Antarctic craton. The basement rocks of Oates are still in progress. These are being supplemented Land appear to resemble most closely those of Marie by studies of rock specimens and field data obtained Byrd Land. Too little is known, however, of the during the 1934 Byrd Antarctic Expedition II and early geologic history of Oates Land for a reliable the U.S. Antarctic Service Expedition, 1940. A com- correlation to be made. There is some indirect evi- plex and rather unique geologic history of Marie dence for block faulting in Marie Byrd Land. The Byrd Land is being unravelled. Based on available islands may have been formed by such a process, and data, it appears that the sequence of events is as the block segments may have moved into their present follows: positions prior to the Cretaceous orogeny. 1. A thick sequence of marine sediments, mostly The formation and intrusion of the Cretaceous quartz sands, argillaceous quartz sands, subgray- granite-like plutons with no apparent preliminary wackes, and thin shale beds was deposited in a sub- processes other than subsidence present somewhat of siding basin during late Precambrian-early Paleozoic a problem. It is hoped that detailed microtextural time. Ages of these sediments are based on the as- studies of the older rocks will provide pertinent data. semblages of microfossils in specimens from the Ford Ranges (litchenko, in press) and from Drummond Potassium-argon ages of granitoid rocks from Marie Byrd Peak, Edward VII Peninsula (unpublished report, Land. this laboratory). Latitude Longitude Age 2. Intense folding and metamorphism of the se- Locality (deg., mm., (deg., (million Mineral quence of sediments occurred in late Ordovician time sec. S.) min. W.) years) (Lopatin and Lorenko, in press). This is the time of Webster Bluff 76 06 30 14508 88 ± 3.4 whole rock the Ross orogeny in East Antarctica. Mount Franklin 7805 30 15448 95.9-4--3.5 biotite 3. Intrusion of large granodioritic plutons in mid- Chester Mountains 7640 14530 98.4±3.6 biotite Paleozoic time in the northern Ford Ranges: Mount McKinley Peak 7752 148 10 101 ±4 biotite June, 352 million years (Halpern, in press); Mount The Billboard 7704 14538 101 ±4 biotite Wunneburger June, 328 million years; Saunders Mountain, 348 Rock 7442 11302 101 ± 4 biotite million years; Radford Islands, 355 million years; Early Bluff 75 11 20 11349 101±4 biotite Mount Swan, 334 million years (table). This igneous Prezbecheski activity was probably late synkinematic. Island 77 02 14836 107 ± 4 biotite 4. Farther to the east in the Kohler Mountains, Phillips Mountains (west nun.) 76 15 14542 134 ± 5 biotite Bakutis Coast sector, intrusive igneous activity oc- Jeffrey Head 74 33 45 11145 143 ± 11 biotite curred during late-Paleozoic time: Mount Strange, Mount Isherwood 7459 11336 283 ± 10 biotite 265 million years (Halpern, in press), and Mount Wiener Peaks 7649 14426 299 ± 11 biotite Isherwood, 283 million years (table). Mount June 76 16 145 02 328-L5 biotite Mount Swan 7658 14348 334 ± 12 biotite 5. No record has been noted of any geologic proc- Saunders esses other than erosion during the Triassic and Juras- Mountain 7651 14548 348±12 biotite sic Periods. Radford Island 7654 14645 355±12 biotite

144 ANTARCTIC JOURNAL It is estimated that reports on Marie Byrd Land present in lesser proportions are basalt, andesite, and Ellsworth Land will be completed on or before shale, sandstone, and siltstone. The sandstones, with September 1, 1973. This work is supported by Na- few exception, are lithic sandstones, or litharenites tional Science Foundation grant GV-22901. (fig.) according to the classification of Folk (1968). The sandstones of the Trinity Peninsula Series of Carboniferous(?) age (Adie, 1957) are markedly dif- References ferent from those of the Latady Formation. Elliot Boudette, E. L., R. F. Marvin, and C. E. Hedge. 1966. (1965) has shown that the Trinity Peninsula series Biotite, potassium-feldspar, and whole rock ages of adamel- lite, Clark Mountains, West Antarctica. U.S. Geological sandstones are arkoses. Feldspar, dominantly plagio- Survey. Professional Paper, 550-D: 190-194. clase, and quartz are much more abundant than rock Halpern, M. 1968. Ages of Antarctic and Argentine rocks fragments, which are mostly particles derived from bearing on continental drift. Earth and Planetary Science rhyolite and granite, but include subordinate sedi- Letters, 5(3): 159-167. mentary and metamorphic rocks. A fine-grained Halpern, M. In press. Rubidium-strontium total-rock and mineral ages from the Marguerite Bay area, Kohler Range matrix comprising half the rock is typical of Trinity and Fosdick Mountains, West Antarctica. In: Antarctic Peninsula Series sandstones. Geology and Geophysics (R. J. Adie, ed.). Oslo, Uni- Rocks of both the Latady Formation and the versitetsforlaget. Trinity Peninsula Series are commonly poorly ex- Jitchenko, L. N. In press. Late Precambrian acritarcha of Antarctica. In: Antarctic Geology and Geophysics (R. J. posed. The two units are similar in appearance; both Adie, ed.). Oslo, Universitetsforlaget. are dark colored, are tightly folded, and have well Lopatin, B. G., and E. M. Lorenko. In press. Outlines of the developed slaty cleavage. Fossils are rare and poorly geology of Marie Byrd Land and Eights Coast. In: Antarc- preserved in all known exposures of the Trinity Penin- tic Geology and Geophysics (R. J. Adie, ed.). Oslo, Uni- sula Series and in many exposures of the Latady For- versitetsforlaget. LeMasurier, W. E. 1972. Volcanic record of antarctic glacial mation. Comparison of sandstone composition is the history: implications with regard to Cenozoic sea levels. most useful method for distinguishing between the In: Polar Geomorphology (C. Embleton, ed.). Institute of two formations. British Geographers. Special Publication, 4. This work was supported by National Science Wade, F. A. 1969. Geology of Marie Byrd Land. Antarctic Map Folio Series, 12; plate XVII. Foundation grant AG-187.

References Adie, R. J . 1957. The petrology of Graham Land, III. Metamorphic rocks of the Trinity Peninsula Series. Falk- Composition of Jurassic sandstones, land Island Dependencies Surveys. Scientific Reports, 20. Lassiter Coast 26 p. Elliot, D. H. 1965. Geology of North-west Trinity Peninsula, Graham Land. British Antarctic Survey. Bulletin, 7. 24 p. P. L. WILLIAMS and P. D. ROWLEY U.S. Geological Survey Denver, Colorado Quartz Sandstone comprises 10-60 percent of measured stratigraphic sections of the Latady Formation of Late Jurassic age in the Lassiter Coast and adjacent areas of southern Palmer Land. Other rock types present are carbonaceous siltstone, shale, and mud- stone; conglomerate is absent (Williams, 1970; Wil- liams and Rowley, 1971; Williams et al., in press). Major components of the sandstones are, on the aver- age, quartz, 20 percent; feldspar, 17 percent; rock fragments, 33 percent; and quartz-sericite matrix, commonly with minor amounts of carbonate, 30 per- cent. Plagioclase feldspar (An 20-30) is slightly more abundant than potassium feldspar, which is almost entirely orthoclase with rare grains of microcine. Rock fragments are dominantly felsic volcanic rocks; Feldspar Rock fragments

Composition of clastic particles of sandstones of the Trinity Publication authorized by the Director, U. S. Geological Peninsula Series (0) (after Elliot, 1965) and the Latady Survey. Formation (i). Generalized from Folk (1968).

September-October 1972 145