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Timing of events in an Early Cretaceous island arc–marginal basin system on South Georgia

Published online by Cambridge University Press:  01 May 2009

P. W. G. Tanner  and
D. C. Rex
P. W. G. Tanner
Affiliation:
British Antarctic Survey, Madingley Road, Cambridge CB3 0ET, England
D. C. Rex
Affiliation:
Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, England
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Summary

19 new K–Ar mineral ages of 78-201 Ma and 3 Rb–Sr whole rock isochron ages of 81 ± 10, 127±4 and 181±30 Ma are presented from units of continental crust, mafic complex and island arc assemblage on South Georgia. The Drygalski Fjord Complex, part of the possible floor of the marginal basin in the southern part of the island, includes granodiorite and gabbro plutons of minimum age 180–200 Ma. Together with older metasediments they have been affected by a major thermal event at about 140 Ma, thought to have resulted from the emplacement of a mafic complex (Larsen Harbour Formation) during the initial opening of the marginal basin. Rocks of the Larsen Harbour Formation are cut by the Smaaland Cove intrusion dated by Rb–Sr whole rock isochron at 127±4 Ma. An island arc assemblage exposed to the SW of South Georgia consists of pyroclastic rocks cut by monzodiorite and andesite intrusions, which give radiometric ages of 81–103 Ma. These data suggest that the marginal basin opened during the late Jurassic (pre-140 Ma); that part of an earlier (early Mesozoic) magmatic arc is preserved in continental crust making up part of the floor of the basin; and that subduction continued beneath the island arc until at least the Senonian time. The younger plutons in the arc were emplaced at roughly the same time as turbidite facies rocks at deep levels in the marginal basin were being affected by penetrative deformation and metamorphism. The timing of events on South Georgia agrees closely with that deduced for the continuation of the same island arc–marginal basin system in South America. The 180–200 Ma plutons correlate with an older suite of plutonic rocks reported from the Antarctic Peninsula and southern Andes; they are part of a once-continuous magmatic arc related to subduction of the Pacific plate beneath Gondwanaland during the early Mesozoic.

Type
Articles
Information
Geological Magazine , Volume 116 , Issue 3 , May 1979 , pp. 167 - 179
Copyright
Copyright © Cambridge University Press 1979

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References

Bell, C. M., Mair, B. F. & Storey, B. C. 1977. The geology of part of an island arc marginal-basin system in southern South Georgia. Bull. Br. antarct. Surv. 46, 109–27.Google Scholar
Bruhn, R. L. & Dalziel, I. W. D. 1977. Destruction of the early Cretaceous marginal basin in the Andes of Tierra del Fuego. In Island Arcs, Deep Sea Trenches and Back-arc Basins, Maurice Ewing Series, vol. 1, pp. 395–405. American Geophysical Union.CrossRefGoogle Scholar
Dalziel, I. W. D., De Wit, M. J. & Palmer, K. F. 1974. Fossil marginal basin in the southern Andes. Nature, Lond. 250, 291–4.Google Scholar
Dalziel, I. W. D., Dott, R. H., Winn, R. D. & Bruhn, R. L. 1975. Tectonic relations of South Georgia Island to the southernmost Andes. Bull. geol. Soc. Am. 86, 1034–40.2.0.CO;2>CrossRefGoogle Scholar
De Wit, M. J. 1977. The evolution of the Scotia arc as a key to the construction of southwestern Gondwanaland. Tectonophysics 37, nos. 1–3, 53–81.Google Scholar
Dott, R. H., Winn, R. D., De Wit, M. J. & Bruhn, R. L. 1977. Tectonic and sedimentary significance of Cretaceous Tekenika Beds of Tierra del Fuego. Nature, Lond. 266, 620–2.CrossRefGoogle Scholar
Gledhill, A., Rex, D. C. & Tanner, P. W. G. (in the press). Rb-Sr and K-Ar geochronology of rocks from the Antarctic Peninsula between Anvers Island and Marguerite Bay. In 3rd Symp. Antarctic Geology and Geophysics (ed. Craddock, C.), Madison, Wisconsin.Google Scholar
Halpern, M. & Rex, D. C. 1972. Time of folding of the Yaghan Formation and age of the Tekenika Beds, southern Chile, South America. Bull. geol. Soc. Am. 83, 1881–6.Google Scholar
Karig, D. E. 1971. Origin and development of marginal basins in the Western Pacific. J. Geophys. Res. 76, 2542–61.CrossRefGoogle Scholar
Karig, D. E. 1974. Evolution of arc systems in the Western Pacific. Ann. Rev. Earth Planet. Sci. 2, 51–75.CrossRefGoogle Scholar
Karig, D. E. & Moore, G. F. 1975. Tectonically controlled sedimentation in marginal basins. Earth Planet. Sci. Lett. 26, 233–8.CrossRefGoogle Scholar
Katz, H. R. 1972. Plate tectonics and orogenic belts in the south-east Pacific. Nature, Lond. 237, 331–2.Google Scholar
Katz, H. R. 1973. Contrasts in tectonic evolution of orogenic belts in the south-east Pacific. Jl R. Soc. N.Z. 3, 333–62.Google Scholar
Katz, H. R. & Watters, W. A. 1966. Geological investigation of the Yaghan Formation (upper Mesozoic) and associated igneous rocks of Navarino Island, southern Chile. N.Z. Jl Geol. Geophys. 9, 323–59.CrossRefGoogle Scholar
Mair, B. F. (in the press). The Larsen Harbour Formation and associated intrusive rocks of southern South Georgia. Bull. Br. antarct. Surv.Google Scholar
Pettigrew, T. H. (in the press). The geology of Annenkov Island. Bull. Br. antarct. Surv.Google Scholar
Pettigrew, T. H. & Willey, L. E. 1975. Belemnite fragments from Annenkov Island. Bull. Br. antarct. Surv. 40, 33–6.Google Scholar
Rex, D. C. 1976. Geochronology in relation to the stratigraphy of the Antarctic Peninsula. Bull. Br. antarct. Surv. 43, 49–58.Google Scholar
Simpson, P. & Griffiths, D. H. (in the press). The structure of the South Georgia continental block. In 3rd Symp. Antarctic Geology and Geophysics (ed. Craddock, C.), Madison, Wisconsin.Google Scholar
Steiger, R. H. & Jäger, E. 1977. Subcommission on geochronology: convention on the use of decay constants in geo- and cosmo-chronology. Earth Planet. Sci. Lett. 36, 359–62.Google Scholar
Stern, C., de Wit, M. J. & Lawrence, J. R. 1976. Igneous and metamorphic processes associated with the formation of Chilean ophiolites and their implication for ocean floor metamorphism, seismic layering, and magnetism. J. Geophys. Res. 81, 4370–80.Google Scholar
Stone, P. (in the press, a). The geology of South Georgia. IV. Barff Peninsula and Royal Bay areas. Scient. Rep. Br. antarct. Surv.Google Scholar
Stone, P. (in the press, b). Geological observations in the Cooper Bay-Wirik Bay area, South Georgia. Bull. Br. antarct. Surv.Google Scholar
Storey, B. C., Mair, B. F. & Bell, C. M. 1977. The occurrence of Mesozoic ocean floor and ancient continental crust on South Georgia. Geol. Mag. 114, 203–8.CrossRefGoogle Scholar
Suárez, M. & Pettigrew, T. H. 1976. An Upper Mesozoic island-arc-back-arc system in the southern Andes and South Georgia. Geol. Mag. 113, 305–28.Google Scholar
Tanner, P. W. G. (in the press). Geological evolution of South Georgia. In 3rd Symp. Antarctic Geology and Geophysics (ed. Craddock, C.), Madison, Wisconsin.Google Scholar
Thomson, M. R. A., Tanner, P. W. G. & Rex, D. C. (in the press). Fossil and radiometric evidence for ages of deposition and metamorphism of sedimentary sequences on South Georgia. In 3rd Symp. Antarctic Geology and Geophysics (ed. Craddock, C.). Madison, Wisconsin.Google Scholar
Trendall, A. F. 1959. The geology of South Georgia: II. Scient. Rep. Falkld Isl. Depend. Surv. 19.Google Scholar