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

Prakash P. Roday ¹, Yashwant B. Katpatal ¹

Affiliations
1 Department of Applied Geology, The University, Sagar 470003, M.P., IN

Abstract

All methods of computing Rs. the tectonic strain ratio from the various means (of axial ratios of ellipsoidal particles that undergo deformation homogeneously with the matrix-the passive particles) such as arithmetic (̅Rf). geometric (Rg) or harmonic (H) fail to adequately express the real values of Rs. Using the data given by Lisle (1979) for simulated conglomerates, it is shown that ̅Rf_H = H+̅Rf÷2-(H+̅Rf)^-1 is closest to Rs if Rs > Ri. For Ri > Rs (2φ > 90° in a given principal plane), R' (given by ̅Rf_a-̅Rf_a^-2/̅Rf_b-̅Rf_b^-1 or by ̅Rf_a-̅Rf_a^-1/̅Rf_b-̅Rf_b^-2, depending upon whether Ri_b > RS_b or Ri_a > RS_a respectively) gives the value of k and the values of a and b that are closest to that of the superimposed Rs. The data are tabulated and also plotted on a conventional Flinn diagram.

Keywords

Simulated Conglomerates, Passive Elliposidal Particles, Tectonic Strain Ratio, Initial Axial Ratio, Mean Shape.

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Prakash P. Roday ¹, Yashwant B. Katpatal ¹

Affiliations
1 Department of Applied Geology, Dr. H. S. Gour University, Sagar - 470 003, IN

Abstract

Any λ1 λ3 principal sectional boudin shape is considered to depart from the ideal ellipse and its overall shape could be described in terms of the average four values of the exponent, p, one for each quadrant. Based on this, some principal shapes and their geometrical variations are characterised and possible mechanical and kinematic significance of each shape outlined. The values of the exponent, p, were calculated using a digital computer.

Keywords

Boudins, Ellipses, Kinematics, Structural Geology.

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Yashwant B. Katpatal ¹, Prakash P. Roday ²

Affiliations
1 Dept. of Civil Engg., V.R.C.E., Nagpur - 440 011, IN
2 Department of Applied Geology, Dr. H.S. Gour University, Sagar - 470003, M.P., IN

Abstract

Under large finite tectonic deformation and under a condition of low viscosity contrast, the axial orientational fluctuation method based on sine functions alone underestimates the values of a and b measured in the field. It is found that a better estimate of a and b and therefore of Rs could be obtained by using both sine and cosine functions. The parameters l, m and n introduced never equalise a, b and k respectively except when k = n = 0 (I = 1, m = α, k = n = 1 (1 = m but both greater than unity) and k = n = α (1 = α, m = 1). Usage of this method enhances the latitude of the ratios based exclusively on sine functions, thereby giving higher values of a and b despite small degree of orientational fluctuation of axes of ellipsoidal particles.

Keywords

Tectonics, Finite Strain Determination.

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