Structural Studies in the Scotia Arc: relatively mature sandstone. Only plant fossils were Livingston Island found and it is not yet known whether any of these are diagnostic. Although tentatively correlated with the Trinity Peninsula Series by Hobbs (1968) on IAN W. D. DALZIEL lithic grounds, the rocks are remarkably similar to the Lamont-Doherty Geological Observatory Cretaceous sediments at Cape Legoupil, directly Columbia University across the Bransfield Strait on the Antarctic Penin- sula, as described by Halpern (1965; see also Adie, The South Shetland Islands lie on the southern limb 1964). of the Scotia Arc, separated from the Antarctic Pen- The rocks of the Miers Bluff Formation, dip north- insula by the Bransfield Strait (Fig. 1). During the west at a low or moderate angle. They were regarded 1968-1969 antarctic summer, the author and his as- by Hobbs (1968) as a normal upward-facing succes- sistant, S. J. Brocoum, spent approximately seven sion. However, the present study has shown that they weeks in the southeastern part of Livingston Island, lie on the inverted limb of a recumbent fold of nappe the largest of the group, carrying out geological and proportions which is refo!ded by at least two later sets geophysical studies pertinent to the tectonic history of of structures. The hinge line of the recumbent fold the Arc. This particular location was selected in order can he deduced from cleavage/bedding relations to to study the so-called False Bay schists, which were strike northeast-southwest parallel to the trend of the tentatively assigned a Precambrian age by Hobbs Scotia Arc at this point, and the fold faces southeast. (1968), and a deformed but unmetamorphosed sedi- The structural history of the Miers Bluff Formation is mentary sequence, the Miers Bluff Formation (Hobbs, similar to that of the Cape Legoupil Formation as 1968). out1in€d by Miller (1966). The False Ba y schists occur oil eastern side of Two other projects were undertaken during the False Bay. They are mainly hornblendic, look like field season. Approximately 1 50 cores were collected part of a reuiona1lv metamorphosed assemblage, but for paleomagnetic study from the Miers Bluff Forma- occur only as xenoliths within a coarse-grained ton- tion, the tonalite body, and numerous crosscutting alite. As pointed out by Hobbs (1968), there is no dikes. Also, a portable hi gh- gain seismnogra)h was op- conclusive evidence oil Island concerning erated for 10 days before it was damaged in transit. their age. In an attempt to settle this question, mate- References rial was collected for radiometric dating, which is now Adie, R. J . 1964. Geological history. In: Antarctic Research. being undertaken by Martin Halpern of the South- Butter-worths, London, P. 118-162. west Center for Advanced Studies. Specimens of the Halpern, M. 1965. The geology of the General Bernardo OHiggins area, northwest Antarctic Peninsula. Antarc- tonalite are also being dated; it is presumabl y a tic Research Series, 6: 177-209. member of the Andean intrusive suite. Hobbs, C. J . 1968. The geology of the South Shetland Most of the available time in the field was spent Islands: TV. The geology of Livingston Island. British sttl(lving the Miers Bluff Formation, t1iic1i forms the Antarctic Surzey. Scientific Report, no. 47, 34 p. Hurd Peninsula between South Bay arid False Bay. It Miller, H. 1966. Kleintektonische Untersuchungen in der Umngebung der Station "General Bernardo OHiggins," is a flvsch-type sequence of alternating shales and Nordwestspitze der Antarktisclien 1-lalbinsel Geological thin graywackes which also contains numerous beds of Research, 55: 809-819. South Ceongia \,t South \ ha. is \ SCOTIA \ SEA \ \ The Scotia Arc showing location \ 5. 1/- South of Livingston Island and (inset) Sout h - Sandwich Orkney Islands the geology of the southwest- False Islands ern part of the island. +507 Bluff LEGEND N :17(2 ri Livingston Deception Island Antarctic C Cape Legoupil 17 Peninsula Miers Bluff Formation N False Bay schists Tonalite July—August 1969 137.