Abstract
Magnetic profiles obtained during the Hesant 92/93 cruise with the R/V Hesperides show large amplitude anomalies (up to 1000 nT) along a 100 km wide band in the northern margin of the Powell Basin. The anomalies, which are also locally identified in the eastern and western margins, are attributed to the continuation of the two branches of the Antarctic Peninsula Pacific Margin Anomaly (PMA). Interactive modelling of two-dimensional bodies in four profiles oriented NNW-SSE allows us to determine the main features of the magnetic source bodies within the continental crust. These are elongated in a N60/degE trend, and their base is located at a depth exceeding 15 km. Equivalent magnetic susceptibilities mostly between 0.07 and 0.1 (SI) are obtained. These values are consistent with the hypothesis that remanent magnetisation of the magnetic source bodies is sub-parallel to the present geomagnetic field (norÍmally magnetised). The general trends of the bathymetry a nd the geometry of the acoustic basement on multichannel seismic profiles are consistent with the upper surface of magnetic bodies. In order to match the observed anomalies it is also necessary to consider a second tabular shaped body with induced magnetisation in almost all the profiles, which could represent layers 2 and 3 of the oceanic crust of the Powell Basin. Three different geometries of connection between the anomalies in the Powell Basin margins and the PMA branches are discussed. The most plausible one is the occurrence of two branches, although they are closer together than in the Bransfield Strait. The northern branch would continue along the fragments of continental crust of the South Scotia Ridge located at the northern boundary of the Powell Basin, whereas the southern branch would be located only in the eastern and western passive margins of the Powell Basin. The apparent splitting of the southern branch of the anomalous body indicates that it was emplaced before Oligo cene times, when the opening of this basin occurred, and that it was subsequently fragmented during the Cenozoic. A possible time of formation of the PMA body would be during the long Cretaceous normal polarity interval, which also coincides with a peak in magmatic activity along the Antarctic Peninsula.
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References
Aldaya, F. and Maldonado, A., 1994, El margen de la placa antártica entre las Shetland y las Orcadas del Sur, V Simposio de Estudios Antárticos. Universidad de Barcelona (in press).
Barber, P. L., Barker, P. F. and Pankhurst, R. J., 1991, Dredged Rocks from Powell Basin and the South Orkney Microcontinent, in Thomson, M. R. A., Crame, J. A. and Thomson, J. W. (eds.), Geological Evolution of the Antarctica. Cambridge University Press, Cambridge, U.K., pp. 361–367.
Barker, P. F., 1982, The Cenozoic Subduction History of the Pacific Margin of the Antarctic Peninsula: Ridge Crest-Trench Inter-actions, J. Geol. Soc. London 139, 787–801.
Barker, P. F. and Burrell, J., 1977, The Opening of Drake Passage, Marine Geology 25, 15–34.
Barker, P. F., Dalziel, I. W. D. and Storey, B. C., 1991, Tectonic Development of the Scotia Arc Region, in Tingey, R. J. (ed.), Antarctic Geology. Clarendon Press, Oxford, pp. 215–248.
British Antarctic Survey, 1985, Tectonic Map of the Scotia Arc Sheet (Misc) 3, Edition 1, Scale 1.3 000 000.
Canals, M., Acosta, J., Grácia, E., Escartín, J. and Grupo ORCA, 1992, Caracterización geoló gica de la región de enlace entre la Cuenca de Bransfield y la Dorsal Sur de Scotia (Antártida), Acta Geol. Hisp. 27, 879–110.
Casas, B., Avalo, J. A., Marín, V., Merino, J. and Socías, I., 1992, Levantamiento magnético en la Isla Livingston, Islas Shetland del Sur, in López Martínez, J. (ed.), Geologia de la Antártida Occidental. III Congreso Geológico de Espanã y VIII Congreso Latinoamericano de Geología (Salamanca), pp. 241–250.
Dalziel, I. W. D., 1984, Tectonic Evolution of a Forearc Terrane. Southern Scotia Ridge, Antarctica, Geol. Soc. Am. Spec. Pap. 200, 32 pp.
Galindo-Zaldívar, J., Jabaloy, A., Maldonado, A. and Sanz de Galdeano, C., 1994, Transtensional Deformation and Internal Evolution in the South Scotia Ridge, Terra Antarctica 1, 303–306.
Galindo-Zaldívar, J., Jabaloy, A., Maldonado, A. and Sanz de Galdeano, C., 1996, Continental Fragmentation along the South Scotia Ridge Transcurrent Plate Boundary (NE Antarctic Peninsula), Tectonophysics 258, 275–301.
Garrett, S. W., 1990, Interpretation of Reconnaisance Gravity and Aeromagnetic Surveys of the Antarctic Peninsula, J. Geophys. Res. 95, 6759–6777.
Garrett, S. W., 1991, Aeromagnetic Studies of Crustal Blocks and Basins in West Antarctica: A Review, in Thomson, M. R. A., Crame, J. A. and Thomson, J. W. (eds.), Geological Evolution of Antarctica. Cambridge University Press, Cambridge, pp. 251–256.
Garrett, S. W., Renner, R. G. B., Jones, J. A. and McGibbon, K. J., 1986/87, Continental Magnetic Anomalies and the Evolution of the Scotia Arc, Earth Planet. Sci. Lett. 81, 273–281.
Garrett, S. W. and Storey, B. C., 1987, Lithospheric Extension on the Antarctic Peninsula During Cenozoic Subduction, in Coward, M. P., Dewey, J. F. and Hancock, P. L. (eds.), Continental Exten-ausion Tectonics. Geological Society, Sp. Pub. 28, pp. 419–431.
Ghidella, M. E., Raymond, C. A. and Labrecque, J. L., 1991, Verification of Crustal Sources for Satellite Elevation Magnetic Anomscript alies in West Antarctica and the Weddell Sea and their Regional Tectonics Implications, in Thomson, M. R. A., Crame, J. A., Thomson, J. W. (eds.), Geological Evolution of Antarctica. Cambridge University Press, Cambridge, pp. 243–250.
Grunow, A. M., Kent, D. V. and Dalziel, I. W. D., 1991, New Paleomagnetic Data from Thurston Island: Implications for the Tectonics of West Antarctica and Weddell Sea Opening, J. Geophys. Res. 96, 17935–17954.
Grunow, A. M., Dalziel, I. W. D., Harrison, T. M., Heizler, M. T., 1992, Structural Geology and Geochronology of Subdustion Complexes Along the Margin of Gondwanaland: New Data from the Antarctic Peninsula and Southernmost Andes, Geol. Soc. Am. Bull. 104, 1497–1514.
Harrington, P. K., Barker, P. F. and Griffiths, 1972, Crustal Structure of the South Orkney Islands Area from Seismic Refraction and Magnetic Measurements, in Adie, R. J. (ed.), Antarctic Geology and Geophysics. Universitesforlaget, Oslo, pp. 27–32.
Herron, E. M. and Tucholke, B. E., 1976, Sea-Floor Magnetic Patterns and Basement Structure in the Southeastern Pacific, in Hollister, C. D., Craddock, C., et al. (eds.), Initial Reports Deep Sea Drilling Project. Washington D.C. 35, 263–278.
I. A. G. A., 1991, International Geomagnetic Reference Field, 1991 Revision, Pure Appl. Geophys. 173 (3), 301–307.
Jeffers, J. D. and Anderson, J. B., 1990, Sequence Stratigraphy of the Bransfield Basin, Antarctica: Implications for Tectonic History and Hydrocarbon Potential, in StJohn, B. (ed.), Antarctica as an Exploration Frontier- Hydrocarbon Potential, Geology and Hazards. AAPG Studies in Geology, Texas, Houston, U.S.A. 31, pp. 13–30.
King, E. C. and Barker, P. F., 1988, The Margins of the South Orkney Microcontinent, J. Geol. Soc. London 145, 317–331.
Larter, R. D. and Barker, P. F., 1991a, Neogene Interaction of Tectonic and Glacial Processes at the Pacific Margin of the Antarctic Peninsula, in MacDonald, D. I. M. (ed.), Sedimentation, Tectonics and Eustacy. Sp. Pub. of the I.A.S, Blackwell 12, pp. 165–186.
Larter, R. D. and Barker, P. F., 1991b, Effects of Ridge Crest- Trench Interaction on Antarctic- Phoenix Spreading: Forces on a Young Subducting Plate, J. Geophys. Res. 96, B12, 19583–19607.
Lawver, L. A., Royer, J., Sandwell, D. T. and Scotese, C. R., 1991, Evolution of the Antarctic Continental Margins, in Thomson, M. R. A., Crame, J. A., Thomson, J.W. (eds.), Geological Evolution of Antarctica, Cambridge University Press, Cambridge, pp. 533–539.
Livermore, R., McAdoo, D. C. and Marks, K. M., 1994, Scotia Sea Tectonics from High-Resolution Satellite Gravity, Earth Planet. Sci. Lett. 123, 255–286.
Maldonado, A., Aldaya, F., Balanyá, J. C., Galindo-Zaldívar, J., Livermore, R. A, Monseñe, F. M., Rodriguez-Fernádez, J., Roussanov, M., Sanz de Galdeano, C., Surinãch, E. and Viseras, C., 1993, Tectonics and Paleoceanography in the Northern Sector of the Antarctic Peninsula: Preliminary Results of HESANT 1992/93 Cruise with the B/O HESPERIDES, Scientia Marina 57, 79–89.
Maldonado, A., Larter, R. and Aldaya, F., 1994, Forearc Tectonic Evolution of the South Shetland Margin, Antarctic Peninsula, Tectonics 13 (6), 1345–1370.
Maslanyj, M. P., Garret, S. W., Johnson, A. C., Renner, R. G. B. and Smith, A. M., 1991, Aeromagnetic Anomaly Map of West Antarctica (Weddell Sea Sector), BAS Geomap Series. Sheet 2, Cambridge, 34 pp.
McAdoo, D. C. and Marks, K. M., 1992, Gravity Fields of the Southern Ocean from GEOSAT Data, J. Geophys. Res. 97, 3247–3260.
Pankhurst, R. J., 1982, Rb-Sr Geocronology of Graham Land, Antarctica, J. Geol. Soc. London 139, 701–712.
Pankhurst, R. J. and Smellie, J. L., 1983, K-Ar Geochronology of the South Shetland Islands, Lesser Antarctica: Apparent Lateral Migration of Jurassic to Quaternary Island Arc Volcanism, Earth Planet. Sci. Lett. 66, 214–222.
Parra, J. C., González-Ferrán, O. and Bannister, J., 1984, Aeromagnetic Survey Over the South Shetland Islands, Bransfield Strait and Part of the Antarctic Peninsula, Rev. Geol. Chile 23, 3–20.
Parra, J. C., Yañez, G. and USAC-Group., 1988, Aeromagnetic Survey on the Antarctic Peninsula and Surrounding Seas: Integration of the Data Obtained at Different Altitudes, Ser. Cient. INACH 38, 117–131.
Smellie, J. L. and Clarkson, P. D., 1975, Evidence for Pre-Jurassic Subduction in Western Antarctica, Nature 258, 701–702.
Watters, D. G., 1972, Geophysical Investigation of a Section of the South Scotia Ridge, in Adie, R. J. (ed.), Antarctic Geology and Geophysics. Universitetsforlaget, Oslo, pp. 33–38.
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Suri/ntildeach, E., Galindo-Zaldivar, J., Maldonado, A. et al. Large Amplitude Magnetic Anomalies in the Northern Sector of the Powell Basin, NE Antarctic Peninsula. Marine Geophysical Researches 19, 65–80 (1997). https://doi.org/10.1023/A:1004240931967
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DOI: https://doi.org/10.1023/A:1004240931967