Swanson Group, Ford Ranges, Marie Byrd Land
to the magnetic iron ore. Symposium on the Bushveld Ig neous Complex and Other Layered Intrusions. Geological Society of South Africa. Special publication, i ( Visser, D. J L., . and G. von Gruenewaldt, editors): 228-241. Vincent, E. A., and R. Phillips. 1954. Iron-titanium oxide minerals in layered gabbros of the Skaergaard intrusion, East Greenland. Part I, chemistry and ore-microscopy. Geochimica et Gosmochimica Ada, 6: 1-26.
Quantitative paleolimnology and other studies in the central Transantarctic Mountains PAUL TASCH
Department of Geology Wichita State University Wichita, Kansas 67208
Lower and upper basalt flow interbeds (Storm Peak) were studied for paleosalinity by geochemical partition of B/Ga and B/V, and by the sedimintary phosphate method. Biotic evidence was used as a further check. All paleosalinities represent much higher than actual values due to concentration in sediments. In the lower flow interbed, salinity increased by 4 parts per thousand and then fluctuated ±1.0 part per thousand. The total range was 27 to 31 parts per thousand. The upper flow interbed presented a steady-state paleosalinity (3.1 parts per thousand) for most of the time, with decreasing paleosalinity (to 21 parts per thousand) in the uppermost bed (Tasch and Gafford, in preparation: part 1, figures 2 and 3; table 1). At Blizzard Heights, the total year value of the fossiliferous interbed, determined chiefly by conchostracan geochronology, was 306 ±20 years (Tasch and Gafford, in preparation: part 2, table 2). These data afford the first year-value determination, and probably constitute a first record, of the Jurassic interbeds of the central Transantarctic Mountains. Because of the unique opportunity these data presented, an electron microprobe analysis was carried out on the basalt flows directly above and below the fossiliferous interbed (Tasch and Gafford, in preparation: part 2, table 3). These two sets of data may permit specialists to evaluate changes in Jurassic magmatic events over a measured time interval. Persistence of and variation in biotic spectra through time has been deciphered in samples from Storm Peak, Blizzard Heights, and Mauger Nuna244
tak (Tasch, in preparation, a; Tasch, 1975). Storm Peak data provide an uncommon glimpse of lake succession across a time lapse at the same site, as well as a seasonal history of each lake. Differences between fossil and modern lacustrine ecosystems (Devonian to Recent) and their significance were recently reviewed (Tasch, 1975). A study of various spoor has been completed (Tasch, in preparation, b). Three crustacean brachiopods occur: Cyzicus, Paleolimnadia, and Cornia. Unexpected was the number of distinct species of the first two genera, which is evidence of gene pool fractionation. The appearance of Cornia was previously unreported from the Jurassic outside the Russian rock column. Russian affinities of antarctic insects have been noted elsewhere (Tasch, 1970). This research was supported by National Science Foundation grant O pp 73-05831. References
Tasch, P. 1970. Antarctic and other Gondwana conchostracans and insects: new data: significance for drift theory. Council for Scientific and Industrial Research. Second Gondwana Symposium, Pretoria, South Africa, 1970. Proceedings, 581692. Tasch, P. In preparation, a. Biostratigraphy, biota and ecosystems of the central Transantarctic Mountains nonmarine deposits. Tasch, P. 1975. Changing antarctic freshwater ecosystems (Devonian-Recent), continental drift, and evolution. Geological Society of America, South Central Section, Ninth Annual Meeting, Austin, Texas. Abstracts with programs, 239-240. Tasch, P. In preparation, b. Jurassic nonmarine spoor (Transantarctic Mountains) and the food web. Tasch, P., and E. L. Gafford. In preparation. Paleolimnological and other studies of the conchostracan bearing beds of the central Transantarctic Mountains. Part 1: paleosalinity. Part 2: geochronology.
Swanson Group, Ford Ranges, Marie Byrd Land F. ALTON WADE Antarctic Research Center The Museum Texas Tech University Lubbock, Texas 79409
As a part of the investigation of the geology of Marie Byrd Land, we have completed detailed ANTARCTIC JOURNAL
studies of all available rock specimens from the Swanson Group, Ford Ranges. The resulting data have been combined with field observations made by Wade in 1934 and 1966, and by L. A. Warner (1945) and C. F. Passe! (1945) in 1940. The Swanson Group is a sequence primarily of metasediments that crop out only in the central and southern Ford Ranges. This group has an estimated thickness of 4,300 meters (Warner, 1945). Based on a single radiometric age of a phyllite and of acritarch assemblages, the age of this group has been tentatively set at late Precambrian to early Paleozoic (Lopatin and Orlenko, 1972; Iltchenko, 1972.) The Swanson Group is composed of metagraywackes, slates, and phyllites. One bed of ash fall tuff, two spillites, and two impure limestone-marble beds have been identified. The metagraywackes comprise well over 75 percent of the total thickness. The graywackes are greatly silicic, being composed in general of quartz, feldspars, and rare lithic clasts in a matrix of quartz, muscovite, and chlorite. Based on rock types and relict primary structures, a eugeosynclinal environment of deposition is indicated. The sediments apparently were derived from a complex of highly silicic intrusives and possibly granite gneisses. During what is termed the Ford orogeny, the sedimentary pile was intensely folded along axes that trend on the average west-northwest to eastsoutheast. Accompanying regional metamorphism was not intense. Most of the rocks are representative of the greenschist facies. Locally, low-grade amphibolite fades was attained. Intrusion of granodiorite plutons during this orogeny occurred about 350 million years before present (Wade, 1972). A second orogeny, the Byrd, which is correlated in time with the Cretaceous Andean orogeny farther to the east, resulted in a minimum of deformation of the Swanson Group. However, great volumes of granite were intruded at this time. Low-grade thermal metamorphism of the metasediments occurred. Near contacts there was hydrothermal alteration. This work is reported in detail in a master's thesis by Dona R. Long, and will be summarized in a comprehensive report on the geology of western Marie Byrd Land being prepared by C. A. Cathey, D. R. Long, and me. This research is supported by National Science Foundation OPP 70-02964. References litchenko, L. N. 1972. Late Precambrian acritarchs of Antarctica. In: Antarctic Geology and Geophysics (Adie, R. J . editor). Oslo, Universitetsforlaget. 599-602. Lopatin, B. G., and F. M. Orlenko. 1972. Outline of the geol-
September/October 1975
ogy of Marie Byrd Land and the Eights Coast. In: Antarctic Geology and Geophysics (Adie, R. J . , editor). Oslo, Universitets-
forlaget. 245-250 Passel, C. F. 1945. Sedimentary rocks of the southern Edsel Ford Ranges, Marie Byrd Land, Antarctica. Proceedings of the American Philosophical Society, 89: 123-13 1. Wade, F. A. 1972. Geological Survey of Marie Byrd Land. Antarctic Journal of the U.S., VII(5): 144-145. Warner, L. A. 1945. Structure and petrography of the southern Edsel Ford Ranges, Antarctica. Proceedings of the American Philosophical Society, 89: 78-122.
Geologic studies of Precambrian basement around Molodezhnaya Station, Enderby Land EDWARD S. GREW
Department of Geology and Geophysics Geophysical and Polar Research Center University of Wisconsin, Madison Madison, Wisconsin 53706 Detailed geologic mapping of Precambrian basement exposed around Molodezhnaya Station (67°40'S. 45°50'E.) was done in 1973 while I was the U.S. exchange scientist with the 18th Soviet Antarctic Expedition (SAE). About 20 square kilometers of coastal exposures was examined, most of which is in the Thala Hills (figure 1). Previous work in the area includes geologic and geochronologic studies by Soviet scientists (Klimov, 1965a and b; Kamenev, 1972) and by earlier U.S. exchange scientists with the SAE—E. E. MacNamara (Myers and MacNamara, 1970) and LeRoy Scharon (Scharon et al., 1970). The geology of this part of East Antarctica is described also by Kamenev et al. (1965), by Trail and McLeod (1969), and by Ravich and Kamenev (1972). The basement consists primarily of well-layered, in part migmatitic, pyroxene, hornblende-biotite, garnet-biotite, and garnet-pyroxene gneisses, and also of charnockitic, enderbitic, and quartz monzodioritic to quartz dioritic gneisses of probable plutonic origin (figure 1). Ultramafic rock, calcsilicate rock, and quartzite form lenses as much as 20 meters thick in the well-layered gneisses. The migmatitic gneisses consist of layers of quartzofeldspathic gneiss as thick as 15 meters that alternate with the well-layered gneisses. Soviet authors refer to such migmatites as coarsely layered migmatites. The gneiss of probable plutonic origin (shadow granites of Soviet authors) crop out in three bodies, two of which are located in the Thala 245
Quantitative paleolimnology and other studies in the central Transantarctic Mountains PAUL TASCH
Department of Geology Wichita State University Wichita, Kansas 67208
Lower and upper basalt flow interbeds (Storm Peak) were studied for paleosalinity by geochemical partition of B/Ga and B/V, and by the sedimintary phosphate method. Biotic evidence was used as a further check. All paleosalinities represent much higher than actual values due to concentration in sediments. In the lower flow interbed, salinity increased by 4 parts per thousand and then fluctuated ±1.0 part per thousand. The total range was 27 to 31 parts per thousand. The upper flow interbed presented a steady-state paleosalinity (3.1 parts per thousand) for most of the time, with decreasing paleosalinity (to 21 parts per thousand) in the uppermost bed (Tasch and Gafford, in preparation: part 1, figures 2 and 3; table 1). At Blizzard Heights, the total year value of the fossiliferous interbed, determined chiefly by conchostracan geochronology, was 306 ±20 years (Tasch and Gafford, in preparation: part 2, table 2). These data afford the first year-value determination, and probably constitute a first record, of the Jurassic interbeds of the central Transantarctic Mountains. Because of the unique opportunity these data presented, an electron microprobe analysis was carried out on the basalt flows directly above and below the fossiliferous interbed (Tasch and Gafford, in preparation: part 2, table 3). These two sets of data may permit specialists to evaluate changes in Jurassic magmatic events over a measured time interval. Persistence of and variation in biotic spectra through time has been deciphered in samples from Storm Peak, Blizzard Heights, and Mauger Nuna244
tak (Tasch, in preparation, a; Tasch, 1975). Storm Peak data provide an uncommon glimpse of lake succession across a time lapse at the same site, as well as a seasonal history of each lake. Differences between fossil and modern lacustrine ecosystems (Devonian to Recent) and their significance were recently reviewed (Tasch, 1975). A study of various spoor has been completed (Tasch, in preparation, b). Three crustacean brachiopods occur: Cyzicus, Paleolimnadia, and Cornia. Unexpected was the number of distinct species of the first two genera, which is evidence of gene pool fractionation. The appearance of Cornia was previously unreported from the Jurassic outside the Russian rock column. Russian affinities of antarctic insects have been noted elsewhere (Tasch, 1970). This research was supported by National Science Foundation grant O pp 73-05831. References
Tasch, P. 1970. Antarctic and other Gondwana conchostracans and insects: new data: significance for drift theory. Council for Scientific and Industrial Research. Second Gondwana Symposium, Pretoria, South Africa, 1970. Proceedings, 581692. Tasch, P. In preparation, a. Biostratigraphy, biota and ecosystems of the central Transantarctic Mountains nonmarine deposits. Tasch, P. 1975. Changing antarctic freshwater ecosystems (Devonian-Recent), continental drift, and evolution. Geological Society of America, South Central Section, Ninth Annual Meeting, Austin, Texas. Abstracts with programs, 239-240. Tasch, P. In preparation, b. Jurassic nonmarine spoor (Transantarctic Mountains) and the food web. Tasch, P., and E. L. Gafford. In preparation. Paleolimnological and other studies of the conchostracan bearing beds of the central Transantarctic Mountains. Part 1: paleosalinity. Part 2: geochronology.
Swanson Group, Ford Ranges, Marie Byrd Land F. ALTON WADE Antarctic Research Center The Museum Texas Tech University Lubbock, Texas 79409
As a part of the investigation of the geology of Marie Byrd Land, we have completed detailed ANTARCTIC JOURNAL
studies of all available rock specimens from the Swanson Group, Ford Ranges. The resulting data have been combined with field observations made by Wade in 1934 and 1966, and by L. A. Warner (1945) and C. F. Passe! (1945) in 1940. The Swanson Group is a sequence primarily of metasediments that crop out only in the central and southern Ford Ranges. This group has an estimated thickness of 4,300 meters (Warner, 1945). Based on a single radiometric age of a phyllite and of acritarch assemblages, the age of this group has been tentatively set at late Precambrian to early Paleozoic (Lopatin and Orlenko, 1972; Iltchenko, 1972.) The Swanson Group is composed of metagraywackes, slates, and phyllites. One bed of ash fall tuff, two spillites, and two impure limestone-marble beds have been identified. The metagraywackes comprise well over 75 percent of the total thickness. The graywackes are greatly silicic, being composed in general of quartz, feldspars, and rare lithic clasts in a matrix of quartz, muscovite, and chlorite. Based on rock types and relict primary structures, a eugeosynclinal environment of deposition is indicated. The sediments apparently were derived from a complex of highly silicic intrusives and possibly granite gneisses. During what is termed the Ford orogeny, the sedimentary pile was intensely folded along axes that trend on the average west-northwest to eastsoutheast. Accompanying regional metamorphism was not intense. Most of the rocks are representative of the greenschist facies. Locally, low-grade amphibolite fades was attained. Intrusion of granodiorite plutons during this orogeny occurred about 350 million years before present (Wade, 1972). A second orogeny, the Byrd, which is correlated in time with the Cretaceous Andean orogeny farther to the east, resulted in a minimum of deformation of the Swanson Group. However, great volumes of granite were intruded at this time. Low-grade thermal metamorphism of the metasediments occurred. Near contacts there was hydrothermal alteration. This work is reported in detail in a master's thesis by Dona R. Long, and will be summarized in a comprehensive report on the geology of western Marie Byrd Land being prepared by C. A. Cathey, D. R. Long, and me. This research is supported by National Science Foundation OPP 70-02964. References litchenko, L. N. 1972. Late Precambrian acritarchs of Antarctica. In: Antarctic Geology and Geophysics (Adie, R. J . editor). Oslo, Universitetsforlaget. 599-602. Lopatin, B. G., and F. M. Orlenko. 1972. Outline of the geol-
September/October 1975
ogy of Marie Byrd Land and the Eights Coast. In: Antarctic Geology and Geophysics (Adie, R. J . , editor). Oslo, Universitets-
forlaget. 245-250 Passel, C. F. 1945. Sedimentary rocks of the southern Edsel Ford Ranges, Marie Byrd Land, Antarctica. Proceedings of the American Philosophical Society, 89: 123-13 1. Wade, F. A. 1972. Geological Survey of Marie Byrd Land. Antarctic Journal of the U.S., VII(5): 144-145. Warner, L. A. 1945. Structure and petrography of the southern Edsel Ford Ranges, Antarctica. Proceedings of the American Philosophical Society, 89: 78-122.
Geologic studies of Precambrian basement around Molodezhnaya Station, Enderby Land EDWARD S. GREW
Department of Geology and Geophysics Geophysical and Polar Research Center University of Wisconsin, Madison Madison, Wisconsin 53706 Detailed geologic mapping of Precambrian basement exposed around Molodezhnaya Station (67°40'S. 45°50'E.) was done in 1973 while I was the U.S. exchange scientist with the 18th Soviet Antarctic Expedition (SAE). About 20 square kilometers of coastal exposures was examined, most of which is in the Thala Hills (figure 1). Previous work in the area includes geologic and geochronologic studies by Soviet scientists (Klimov, 1965a and b; Kamenev, 1972) and by earlier U.S. exchange scientists with the SAE—E. E. MacNamara (Myers and MacNamara, 1970) and LeRoy Scharon (Scharon et al., 1970). The geology of this part of East Antarctica is described also by Kamenev et al. (1965), by Trail and McLeod (1969), and by Ravich and Kamenev (1972). The basement consists primarily of well-layered, in part migmatitic, pyroxene, hornblende-biotite, garnet-biotite, and garnet-pyroxene gneisses, and also of charnockitic, enderbitic, and quartz monzodioritic to quartz dioritic gneisses of probable plutonic origin (figure 1). Ultramafic rock, calcsilicate rock, and quartzite form lenses as much as 20 meters thick in the well-layered gneisses. The migmatitic gneisses consist of layers of quartzofeldspathic gneiss as thick as 15 meters that alternate with the well-layered gneisses. Soviet authors refer to such migmatites as coarsely layered migmatites. The gneiss of probable plutonic origin (shadow granites of Soviet authors) crop out in three bodies, two of which are located in the Thala 245
