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Asymmetric extensional structures and their implications for the generation of melanges

Published online by Cambridge University Press:  01 May 2009

D. T. Needham
D. T. Needham
Affiliation:
Department of Earth Sciences, University of London Goldsmiths' College, Rachel McMillan Building, Creek Road, London SE8 3BU, U.K.
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Abstract

Studies of melanges in the Shimanto Belt of southwest Japan have shown that many of the included blocks exhibit asymmetric geometries, similar to boudins and inclusions in medium grade metamorphic rocks which have been subjected to markedly non-coaxial strains. Deformation is accomplished by mesoscopically ductile processes such as pore-pressure-controlled or diffusionally-controlled grain boundary sliding, although localized fracture and cataclasis also occurs. It is suggested that the melanges developed by the propagation of extensional displacement zones, analogous to shear bands, through sandstone beds, so progressively dismembering them. Studies of the detailed internal geometries of melanges along with the deformation mechanisms active during their formation may help resolve the mode of formation of these problematic units.

Type
Articles
Information
Geological Magazine , Volume 124 , Issue 4 , July 1987 , pp. 311 - 318
Copyright
Copyright © Cambridge University Press 1987

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References

Aoki, Y., Tamano, T. & Kato, S. 1982. Detailed structure of the Nankai Trough from migrated seismic sections. In Studies in Continental Margin Geology (ed. Watkins, J. S., Drake, C. L.), pp. 309–22. American Association of Petroleum Geologists Memoir 34.Google Scholar
Bally, A. W., Bernoulli, D., Davis, G. A. & Montadert, L. 1981. Listric normal faults. In Geologie des Marges Continentales (eds. Blanchet, R., Montadert, L.), pp. 87–101. Oceanologia Acta, Special Publication, Supplement to Volume 4.Google Scholar
Bosworth, W. 1984. The relative roles of boudinage and ‘structural slicing’ in the disruption of layered rock sequences. Journal of Geology 92, 447–56.CrossRefGoogle Scholar
Butler, R. W. H. 1982. Hangingwall strain: a function of duplex shape and topography. Tectonophysics 88, 235–46.CrossRefGoogle Scholar
Byrne, T. 1984. Early deformation in melange terranes of the Ghost Rocks Formation, Kodiak Islands, Alaska. In Melanges: Their Nature, Origin and Significance (ed. Raymond, L. A.), pp. 21–51. Geological Society of America, Special Paper no. 198.CrossRefGoogle Scholar
Cloos, M. 1982. Flow melanges: numerical modelling and geologic constraints on their origin in the Franciscan subduction complex, California. Geological Society of America Bulletin 93, 330–45.Google Scholar
Cowan, D. S. 1978. Origin of blueschist bearing chaotic rocks in the Franciscan Complex, San Simeon, California. Geological Society of American Bulletin 39, 1415–23.2.0.CO;2>CrossRefGoogle Scholar
Cowan, D. S. 1982. Deformation of partly dewatered and consolidated Franciscan sediments near Piedras Blancas Point, California. In Trench–Forearc Geology: Sedimentation and Tectonics on Modern and Ancient Active Plate Margins (ed. Leggett, J. K.), pp. 439–57. Geological Society of London Special Publication no. 10.Google Scholar
Cowan, D. S. 1985. Structural styles in Mesozoic and Cenozoic melanges in the western Cordillera of North America. Geological Society of America Bulletin 96, 451–62.Google Scholar
Coward, M. P. & Potts, G. J. 1983. Complex strain patterns developed at the frontal and lateral tips to shear zones and thrust zones. Journal of Structural Geology 5, 383–99.CrossRefGoogle Scholar
Ford, M. & Ferguson, C. C. 1985. Cleavage strain in the Variscan Fold Belt, County Cork, Ireland, estimated from stretched Arsenopyrite rosettes. Journal of Structural Geology 7, 217–23.Google Scholar
Greenly, E. 1919. The Geology of Anglesey. Geological Survey of Great Britain Memoir 1. 980 pp.Google Scholar
Hanmer, S. 1986. Asymmetric pull-aparts and foliation fish as kinematic indicators. Journal of Structural Geology 8, 111–82.CrossRefGoogle Scholar
Hossack, J. R. 1979. The use of balanced cross sections in the calculation of orogenic contraction. Journal of the Geological Society of London 136, 705–11.CrossRefGoogle Scholar
HsÜ, K. J. 1974. Melanges and their distinction from olistostromes. In Modern and Ancient Geosynclinal Sedimentation (ed. Dott, R. H. Shaver, R. H.), pp. 321–33. Society of Economic Palaeontologists and Mineralogists, Special Publication no. 19.Google Scholar
Knipe, R. J. & Needham, D. T. 1986. Deformation processes in accretionary wedges – examples from the SW margin of the Southern Uplands of Scotland. In Collision Tectonics (ed. Coward, M. P., Ries, A. C.), pp. 51–67. Special Publication of the Geological Society of London no. 19.Google Scholar
Lister, G. S. & Williams, P. F. 1983. The partitioning of deformation in flowing rock masses. Tectonophysics 92, 1–33.Google Scholar
Lister, G. S. & Snoke, A. W. 1984 S–C mylonites. Journal of Structural Geology 6, 617–38.CrossRefGoogle Scholar
Lloyd, G. E., Ferguson, C. C. & Reading, K. 1982. A stress transfer model for the development of extension fracture boudinage. Journal of Structural Geology 4, 355–72.Google Scholar
Mackenzie, J. S., Needham, D. T. & Agar, S. M. (in press.) Progressive deformation in an accretionary complex: an example from the Shimanto Belt of eastern Kyushu, southwest Japan. Geology.Google Scholar
Moddock, R. & Rutter, E. H.. 1986. Experimental deformation of synthetic fault gouges: shear fabrics and microstructures. Abstract, Shear Criteria Meeting, Imperial College, London, 22–24 May 1986.Google Scholar
Meneilly, A. W. & Storey, B. C. 1986. Ductile thrusting within subduction complex rocks on Signy Island, South Orkney Islands. Journal of Structural Geology 8, 457–72.CrossRefGoogle Scholar
Needham, D. T. & Mackenzie, J. S. (in press.). Structural evolution of the Shimanto Belt accretionary complex in the area of the Gokase River, Kyushu, SW Japan. Journal of the Geological Society of London.Google Scholar
Platt, J. P. 1984. Secondary cleavages in ductile shear zones. Journal of Structural Geology 6, 439–42.Google Scholar
Platt, J. P. & Vissers, R. L. M. 1980. Extensional structures in anisotropic rocks. Journal of Structural Geology 2, 397–410.CrossRefGoogle Scholar
Platt, J. P. & Leggett, J. K. 1986. Stratal extension in thrust footwalls, Makran accretionary prism: implications for thrust tectonics. American Association of Petroleum Geologists Bulletin 70, 191–203.Google Scholar
Sakai, T. 1978. Geologic structure and stratigraphy of the Shimantogawa Group in the middle reaches of the Gokase River, Miyazaki Prefecture, Science Reports, Department of Geology Kyushu University 13, 23–38. (In Japanese with English abstract).Google Scholar
Sugisaki, R., Suzuki, T., Kanmera, K., Sakai, T. & Sano, H. 1979. Chemical compositions of green rocks in the Shimanto Belt, Southwest Japan. Journal of the Geological Society of Japan 85, 455–66.Google Scholar
Suzuki, T., Hada, S., Umemura, H., Kado, K., Sakamoto, Y. & Nakagawa, H. 1978. Genetic consideration of the green rocks in the Shimanto Belt, Southwest Japan – with special reference to the mode of occurrence. Chikyu Kagaku (Earth Science) 32, 321–30. (In Japanese with English abstract.)Google Scholar
Taira, A. (in prep.) Sedimentary evolution of the Shikoku subduction zone: Shimanto Belt and Nankai trough. In Formation of Ocean Margins. 1983 Oji Seminar Proceedings.Google Scholar
Tchalenko, J. S. 1970. Similarities between shear zones of different magnitudes. Geological Society of America Bulletin 81, 1625–40.Google Scholar
Wernicke, B. & Burchfiel, B. C. 1982. Modes of extensional tectonics. Journal of Structural Geology 4, 105–15.CrossRefGoogle Scholar
Wood, D. S. 1974. Ophiolites, melanges, blueschists and ignimbrites: Early Caledonian subduction in Wales. In Modern and Ancient Geosynclinal Sedimentation (ed. Dott, R. H., Shaver, R. H.), pp. 334–44. Society of Economic Palaeontologists and Mineralogists Special Publication no. 19.CrossRefGoogle Scholar