Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

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A Paradoxical Situation in Determining Relative Competence from Wavelength/Arclength Ratios Within Buckle Folded Multilayers


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1 Department of Geological Sciences, Jadavpur University, Kolkata-700 032, India
     

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By measuring the ratio of wavelength to arclength of folds in closely associated disharmonically folded competent layers, it is possible to determine which layer has undergone a greater layer-parallel strain and has a smaller competence. This method may lead to a paradoxical situation. For example when foliated quartzite and mica schist layers are folded together, the mica schist laminae show a much larger buckle shortening than the quartzite layers. On the other hand, the geometry of folds in quartzite indicates that quartzite was more competent than the mica schist. The structure can be explained by different modes of buckling, general buckling in quartzite layers and internal buckling in strongly anisotropic mica schists.

Keywords

Arc Length, Wavelength, Multilayer, Buckling, Internal Buckling.
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  • BIOT, M.A. (1964) Theory of internal buckling of a confined multilayer structure. Geol. Soc. Amer. Bull., v.75, pp.563-568.

  • BIOT, M.A. (1965a) Further development of theory of internal buckling of multilayers. Geol. Soc. Amer. Bull., v.76, pp.833-840.

  • BIOT, M.A. (1965b) Mechanics of Incremental Deformations. John Wiley & Sobs, New York, London and Sydney.

  • COBBOLD, P.R. (1976) Mechanical effect of anisotropy during large finite deformation. Bull. Soc. Geol. France, v.18, pp.1497-1510.

  • COBBOLD, P.R., COSGROVE, J.W. and SUMMERS, J.M. (1971) Development of internal structures in deformed anisotropic rock. Tectonophysics, v.12, pp.155-178.

  • GHOSH, S.K. (1968) Experiments on buckling of multilayers which permit inter-layer gliding. Tectonophysics, v.6, pp.207-249.

  • HUDLESTON, P.J. (1986) Extracting information from folds in rocks. Jour. Geol. Educ., v.34, pp.237-245.

  • HUDLESTON, P.J. (1973) An analysis of single layer folds developed experimentally in viscous medium. Tectonophysics, v.16, pp.189-214.

  • RAMBERG, H. (1964) Selective buckling of composite layers with contrasted rheological properties, a theory for the formation of several orders of folds. Tectonophysics v.1, pp.307-341.

  • RAMSAY, J.G. (1967) Folding and Fracturing of rocks. McGraw-Hill. New York.

  • RAMSAY, J.G. and HUBER, M.I. (1987) The techniques of Modern Structural Geology, 2: Folds and fractures. Academic Press, London.

  • SHERWIN, J. and CHAPPLE,W.M. (1968) Wavelength of single layer folds: a comparison between theory and observation. Amer. Jour. Sci., v.266, pp.167-179.


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  • A Paradoxical Situation in Determining Relative Competence from Wavelength/Arclength Ratios Within Buckle Folded Multilayers

Abstract Views: 203  |  PDF Views: 1

Authors

S. K. Ghosh
Department of Geological Sciences, Jadavpur University, Kolkata-700 032, India
Sudipta Sengupta
Department of Geological Sciences, Jadavpur University, Kolkata-700 032, India

Abstract


By measuring the ratio of wavelength to arclength of folds in closely associated disharmonically folded competent layers, it is possible to determine which layer has undergone a greater layer-parallel strain and has a smaller competence. This method may lead to a paradoxical situation. For example when foliated quartzite and mica schist layers are folded together, the mica schist laminae show a much larger buckle shortening than the quartzite layers. On the other hand, the geometry of folds in quartzite indicates that quartzite was more competent than the mica schist. The structure can be explained by different modes of buckling, general buckling in quartzite layers and internal buckling in strongly anisotropic mica schists.

Keywords


Arc Length, Wavelength, Multilayer, Buckling, Internal Buckling.

References