Cooper, R. A., J. B. Jago, A. J. Rowell, and P. Braddock. In press. Age northern Victoria Land, . In C. Craddock (Ed.), Antarctic and correlation of the — Bowers Supergroup, geoscience. Madison: University of Wisconsin Press. northern Victoria Land. In R. L. Oliver, J. B. Jago, and P. R. James Laird, M. C., and J. D. Bradshaw. In press. New data on the Early (Eds.), Antarctic Earth Science, Australian Academy of Science, Paleozoic Bowers Supergroup. In R. L. Oliver, J . B. Jago, and P. R. Canberra. James (Eds.) Antarctic Earth Science, Australian Academy of Science, Henderson, R. A., and D. I. MacKinnon. 1981. New Cambrian inar- Canberra. ticulate Brachiopoda from Australasia and the age of the Tasman Shergold, J. H., R. A. Cooper, D. I. MacKinnon, and F. L. Yochelson. Formation. Alcheringia, 5, 289-309. 1976. Late Cambrian Brachiopoda, Mollusca, and Trilobita from Laird, M. C. 1981. Lower Paleozoic rocks of Antarctica. In C. H. Hol- northern Victoria Land, Antarctica. Palaeontology, 19, 247-291. land (Ed.), Lower Paleozoic of the Middle East, Eastern and Southern Tessensohn, E, K. Duphorn, K. Jordan, G. Kleinschmidt, D. Skinner, Africa, and Antarctica. New York: John Wiley and Sons. U. Vetter, T. 0. Wright, and D. Wyborn. 1981. Geological comparison Laird, M. C., J. D. Bradshaw, and A. Wodzicki. 1982. Stratigraphy of of basement units in North Victoria Land, Antarctica. Geologisches the Upper Precambrian and Lower Paleozoic Bowers Supergroup, Jahrbuch, 41, 31-88.

sandstone units (figure 3). Fifty or more measurements of Sedimentary petrology of - trough crossbedding and of ripple mark directions within each fluvial rocks in Allan Hills, sandstone unit at several localities indicate flow generally to- central Victoria Land ward the west; dispersal varies as much as 180° from one cycle to another. Large coalified and silicified logs and Glossopteris leaves are locally abundant. Coal beds, up to 2 meters thick, are of high rank because of heating by the intrusion of Ferrar JAMES W. COLLINSON and DEANA CHAPMAN PENNINGTON Dolerite. An abrupt change in lithology and one to three well-de- Institute of Polar Studies veloped ferricrete horizons at the top of the Weller Formation The Ohio State University suggest that a major disconformity separates the Weller and the Columbus, Ohio 43210 overlying Feather Sandstone. The lower Feather Sandstone (120 meters thick), which is a NOEL R. KEMP massive cliff-forming, medium-grained, quartzose sandstone, was deposited by sand-dominated braided streams. Vertical- Tasmanian Museum and Art Gallery tube burrows, also noted by Ballance (1977), 0.5 cen- Hobart, Tasmania, Australia 7001 (Skolithos) timeters in diameter and 20-30 centimeters long, are abundant.

Sedimentologic studies of Permian-Triassic fluvial rocks in Allan Hills (76°42S 159°50E) were conducted to compare the sequence there with equivalent sequences elsewhere in Victoria 6km Land. The Allan Hills sequence, first described and mapped by JURASSIC 1-o Ballance (1977), was found to be greatly similar to the strati- El Coal D graphic section described by McElroy (1969), Barrett, Grindley, 500m Shale and Webb (1972), and McKelvey et al. (1972) in southern Vic- toria Land, but dissimilar to equivalent rocks in northern Vic- Sandstone toria Land (Collinson and Kemp 1982). The stratigraphic se- Unconformity quence in Allan Hills is shown in figure 1. 400m LASHLY A five-person field party, including Collinson and Kemp, B. L. Roberts (geologic field assistant), and W. H. Hammer and B FORMAT 10 N\01, J. M. Zawiskie (vertebrate paleontologists), worked from 8-15 300m January 1982 from a tent camp emplaced by helicopter from McMurdo Station. Stratigraphic sections of each formation were TRIASSIC FLEMING measured, described, and sampled. More than 750 crossbed- 200 m MEMBER ding directions were analyzed to determine paleocurrent dis- persal. Figure 2 was compiled from modal analysis by Chapman PERMIAN FEATHER FORMATION\ of 29 thin sections. The lowest stratigraphic unit exposed in the Allan Hills, the lOOm upper 73 meters of the Permian Weller Formation, is repre- WELL ER FORMATION sented by meandering stream, floodplain, and floodbasin de- posits. These consist of 5 to 10 meter-thick fining-upward cycles of feldspathic sandstone, carbonaceous shale and coal. Point- bar accretion beds dip 10-15° and extend from top to bottom of Figure 1. Stratigraphlc sequence in Allan Hills.

20 ANTARCTIC JOURNAL

QUARTZ

- -,

F±LUSIAH L1THIC FRAGMENTS

Figure 2. Triangular composition diagram indicating mean sand- stone composition of: "A" denotes Weller Formation; "B" denotes Lower Feather Formation; "C" denotes Upper Feather Formation, Fleming Member; Lashly Formation, units A + B; "E" denotes Lashly Formation, unit C; and "F" denotes Lashly Formation, unit D.

Figure 3. Point-bar accretion beds in Weller Formation. Beds dip from right to left in center and foreground. Similar structures have been reported in the Feather Formation in southern Victoria Land by Barrett, Grindley, and Webb (1972). A ferruginous horizon at the top of the lower Feather may and Collinson, Stanley, and Vavra (1981). Deposition probably represent a regional disconformity separating Permian from occurred in low sinuosity braided streams on a muddy Triassic. This level marks the lowest appearance of volcanic floodplain. detritus in the sequence, an abrupt change in mean paleocur- Member B (54 meters thick), a massive medium- to fine- rent direction from west-northwest to north, and a change from grained volcaniclastic sandstone containing abundant fossil homogenous sandstone to cyclical sandstone and shale. The logs, was deposited by sand-dominated, braided streams. change in paleocurrent direction has been documented at sev- Member C (137 meters thick) consists of fining-upward cycles eral localities in southern Victoria Land by Barrett and Kohn of medium- to fine-grained volcaniclastic sandstone, car- (1975). The upper part of the Feather Formation (53 meters bonaceous siltsone and mudstone, and coal. Well-developed thick) is here assigned to the Fleming Member of the Feather point-bar accretion beds indicate deposition by high sinousity Formation as suggested by Barrett et al. (1971) in southern streams. Carbonaceous beds contain abundant fossil plants of Victoria Land. Kyle (1977) noted the occurrence of Lower Tri- the Middle to Upper Triassic flora, which has been assic palynomorphs in the upper part of the Fleming Member. described from the Allan Hills by Townrow (1967). The Lashly Formation (325 meters thick) can be divided into Member D (85 meters thick) represents a major lithologic four members, which are similar to members A-D described by change from the volcaniclastic sandstones of members A-C, to Barrett and Kohn (1975) for areas to the south. The base of the quartzose sandstone (figure 2). The member consists of thick formation is marked by a decrease in grain-size and an abrupt fining-upward cycles of resistant crossbedded sandstone and increase in volcanic detritus, which gives the generally fine- carbonaceous siltstone and shale with the Dicroidium flora. The grained sandstone a greenish tint and slope-forming charac- highest part of the Lashly in the Allan Hills is a 36-meter-thick teristics. The Lashly appears to be conformable with the under- resistant coarse- to medium-grained sandstone. A spectacular lying Feather, but a ferruginous horizon at the contact suggests unconformity (figure 1) with local relief of 500 meters occurs the possibility of a disconformity. The northerly paleocurrent between the Lashly, Feather, and Weller Formations and the direction remains unchanged across the boundary but gradu- Mawson Formation of Jurassic age (Ballance and Watters 1971). ally swings to northeast higher in the Lashly. As noted by Barrett and Kohn (1975) in southern Victoria Member A (49 meters thick) is represented by fining-upward Land, the Triassic sequence in the Allan Hills is strikingly sim- cycles of medium- to fine-grained volcaniclastic sandstone and ilar to the Fremouw and Falla Formations in the central Trans- greenish-gray siltstone and mudstone with abundant root antarctic Mountains (Barrett 1969; Collinson, Stanley, and casts. Mud drapes on some rippled sandstone surfaces contain Vavra 1981). This similarity and similarities in dispersal direc- mudcracks, indicating subaerial exposure. Sedimentary cycles tions suggest that Triassic fluvial systems may have occupied a in member A and in the underlying Fleming Member are similar single elongate depositional basin. to cycles described from the lower of sim- This work was supported by National Science Foundation ilar age in the central Transantarctic Mountains by Barrett (1969) grant DPP 80-20098.

1983 REVIEW 21 References Geology and Geophysics, 14, 605-614. Collinson, J. W. and N. R. Kemp. 1982. Sedimentology of the Takrouna Ballance, P. F. 1977. The Beacon Supergroup in the Allan Hills, central Formation, a Permian-Triassic fluvial deposit in northern Victoria Victoria Land, Antarctica. New Zealand Journal of Geology and Land. Antarctic Journal of the U.S., 17(5), 15-17. Geophysics, 20, 1003-1016. Collinson, J. W., K. 0. Stanley, and C. L. Vavra, 1981. Triassic fluvial Ballance, P. F., and W. A. Watters. 1971. Mawson Diamictite and the depositional systems in the Fremouw Formation, Cumulus Hills, Carapace Sandstone, formations of the Ferrar Group at Allan Hills Antarctica. In M. M. Cresswell, and P. Vella (Eds.), Gondwana V. and Carapace Nunatak, Victoria Land, Antarctica. New Zealand Jour- Rotterdam: A. A. Balkema. nal of Geology and Geophysics, 14, 512-527. Kyle, R. A. 1977. Palynostratigraphy of the Victoria Group of South Victoria Land, Antarctica. New Zealand Journal of Geology and Barrett, P. J. 1969. Stratigraphy and petrology of the mainly fluviatile Permian and Triassic Beacon Rocks, Beardmore Glacier Area, Antarctica. (Ohio State Geophysics, 20, 1081-1102. University. Institute of Polar Studies. Report 34.) Columbus: The McElroy, C. T. 1969. Comparative lithostratigraphy of Gondwana se- Ohio State University Press. quences in eastern Australia and Antarctica. In Gondwana stratigra- International Union of Geological Sciences Symposium. Buenos Barrett, P. J. , C. W. Grindley, I. N. Webb. 1972. Beacon Supergroup of phy. East Antarctica. In R. J. Adie (Ed.), Antarctic geology and geophysics Aires, October 1-15, 1967. (UNESCO Earth Sciences 2), Paris, symposium on Antarctic and solid earth geophysics. Oslo: 441-461. Universitetsforlaget. McKelvey, B. C., P. N. Webb, M. P. Gorton, and B. P. Kohn. 1972. Stratigraphy of the Beacon Supergroup between the Olympus and Barrett, P. 1. and B. P. Kohn. 1975. Changing sediment transport direc- tions from to Triassic in the Beacon Super-group of south Boomerang Ranges, Victoria Land. In R. J. Adie (Ed.), Antarctic Victoria Land. In K. S. W. Campbell (Ed.), Gondwana geology. Canber- geology and geophysics symposium on Antarctic and solid earth geophysics. ra: Australian National University Press. Oslo: Universitetsforlaget. Townrow J. A. 1967. Fossil plants from Allan and Carapace nunataks, Barrett, P. J. , B. P. Kohn, R. A. Askin, and J. C. McPherson. 1971. Preliminary report on Beacon Supergroup studies between the and from the upper Mill and Shackleton Glaciers, Antarctica. New Hatherton and Mackay Glaciers, Antarctica. New Zealand Journal of Zealand Journal of Geology and Geophysics, 10, 456-473.

occurrences are found. While we found no vertebrate fossils, Gondwana rocks of the Allan Hills we did succeed in collecting a comprehensive suite of plant fossils of very high quality. This material will enhance the cur- rent basis of biostratigraphic zonation and may also provide SANKAR CHATTERJEE new details of gross morphology of the Gondwana flora of Antarctica. The Museum, Texas Tech University The stratigraphy of Allan Hills was discussed by Ballance Lubbock, Texas 79409 (1977), Borns and Hall (1969), and Gunn and Warren (1962). (See figure 1.) The outcrop is in the shape of a crescent, the horns HAROLD W. BORNS, JR. pointing nearly due north to enclose the blue ice of the bay (approximate coordinates 76°62S 159°40E). The arch of the Institute for Quaternary Studies crescent has a tail-like projection which is directed to the south- University of Maine west. Topography produces a repetition of beds, the oldest in Orono, Maine 04473 the central valley region, south and southwest of the bay. Pa- leocurrent vectors indicate flow to the northwest over most NICHOLAS HOTTON III areas. The age of the different formations is based on plant fossils of the Glossopteris flora, which indicate Permian age, and National Museum of Natural History the Dicroidium flora of Triassic age (Townrow 1967). The follow- Smithsonian Institution, Washington, D.C. 20560 ing is the sequence of Gondwana rocks in the Allan Hills as currently understood. 1. Feistmantel Formation (Permian). Unlike other Gondwana The Gondwana System exposed at Allan Hills, southern Vic- basins in Antarctica, the basal tillite bed (Metschel Formation) is toria Land, consists of flat-lying rocks of continental prove- absent here. The oldest mappable unit, recognized by Ballance nance that range in age from Permian to Jurassic. Two units are (1977) is a 30-meter thick Fiestmantel Formation. The dominant recognized: a lower one, the Victoria Group, mainly fluvial lithology is laminated shale and fine sandstone which are com- clastics, and an upper, the Ferrar Group, of volcanic origin. monly in rhythmic alternation. The beds are parallel or micro- During the 1982-1983 field season, our investigation centered crosslaminated, with occasional large-scale cross-bedding. On on the stratigraphy and paleontology of the Victoria Group, as it weathered sandstone surfaces, dome-shaped, concentric struc- was deposited while the ancient Gondwanaland was still unit- tures from 0.5 to 2 meters across are common. They are usually ed. Correlation of Gondwana rocks of southerly continental brown in color and may represent algal mats. Leaf impressions masses is traditionally based largely on fossils of land plants, of both Glossopteris and Gangamopteris are found in the shale. A but remains of terrestrial animals offer finer resolution as new thin conglomerate occurs at the base and contains faceted gra- ANTARCTIC JOURNAL 22