Geometric and strain analyses in folds of the area around Gankot, district Pithoragarh, Uttarakhand, India

Authors

  • Swati Lata Center of Advanced Study, Department of Geology, Banaras Hindu University, Varanasi -221005
  • Ravindra Kumar Center of Advanced Study, Department of Geology, Banaras Hindu University, Varanasi -221005
  • Vaibhava Srivastava Center of Advanced Study, Department of Geology, Banaras Hindu University, Varanasi -221005

DOI:

https://doi.org/10.25299/jgeet.2019.4.2-2.2237

Keywords:

Fold geometry, Strain, Flattening, Shearing, Lesser Himalaya, Multilayered fold

Abstract

The study area around Gankot in Pithoragarh district of Uttarakhand belongs to the Thalkedar Limestone unit of Mandhali Formation, Tejam Group in Inner Sedimentary Zone of Lesser Himalaya, which exposes complexly folded and refolded structures. Geometric analysis carried out on the profile section of the fold tracing using dip isogon and orthogonal thickness parameters revealed presence of all the fold geometry suggested by Ramsay (1967) however the class 3 followed by class 1B are the most dominant classes in the study area when individual layers of the fold were studied. The study of folds as multilayered unit reveals that folds in study area belong to strongly non-analogous fold class of anisodeviatoric folds. In fold, the strain analysis has been done by drawing strain ellipse obtained by Inverse Thickness Method which is useful in estimating flattening strain even when the flattening is imposed obliquely to the fold’s axial trace. The finite two-dimensional flattening strain ratio (Rs) value ranged between 1 and 3.14 with an average Rs value of 1.60. The method of Srivastava and Gairola (2003) has also been used to obtain shear strain and flattening strain for the multilayered folds of study area. The results reveal that the multilayered folds around Gankot area are moderately flattened with mean flatting strain varying between 1.06 and 2.28. A very high degree of variation in shearing ranging about 70o in both clockwise and anticlockwise directions has been noticed. The shear strains (γ) in folds have been found to vary between -2.75 to + 3.27 with an average of +0.33. The shearing and strain patterns are suggestive that the most dominant folding mechanism has been the flexure-shear for the folds of the study area which are overprinted by the fold flattening and other subsequent deformations.

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References

Agarwal, A., Agarwal, K. K., Bali, R., Chandra, P., Joshi, G., 2016. Back-thrusting in Lesser Himalaya: Evidence from magnetic fabric studies in parts of Almora Crystalline zone, Kumaon Lesser Himalaya. Jour. Earth System Science 125, 873-884.
Agarwal, K.K., Sharma, V.K., 2011. Quaternary tilt-block tectonics in parts of Eastern Kumaon Himalaya, India. Zeitschriftfür Geomorphologie N.F. 55, 197-208.
Agarwal, K. K., Sharma, A., Jahan, N., Prakash, C., Agarwal, A., 2011. Occurrence of pseudotachylites in the vicinity of South Almora Thrust zone, Kumaon Lesser Himalaya. Current Science 101, 431-434.
Agarwal, K.K., Jahan, N., Agarwal, A., 2010. Modification of Fold Geometry in Almora Crystalline Shear Zone, Lesser Himalaya. J. Geol. Soc. India75, 411-414.
Azmi, R.J., Paul, S.K., 2004. Dolomite of Inner Kumaun Lesser Himalaya: Implication on age and correlation. Current Science 86, 1653-1660.
Banerjee, S.,Matin, A., Mukul, M., 2015. Overburden-induced flattening structure in the Himalaya: mechanism and implication Current Science 109, 1814-1820.
Bastida, F., 1993. A new method for geometrical classification for large data sets of folds. Jour. Struct. Geol.15, 69–78.
Bastida, F., Bobillo-Ares, N.C.,Aller, J., Toimil, N.C., 2003. Analysis of folding by superposition of strain pattern. Journal of Structural Geology, 25, 1121–1139.
Bhargava, O.N., Frank, W., Bertle, R., 2011. Late Cambrian deformation in the Lesser Himalaya. J. Asian Earth Sci. 40, 201-212.
Bhattacharyya, K., Ahmed, F., 2016. Role of initial basin width in partitioning total shortening in the Lesser Himalayan fold-thrust belt: Insights from regional balanced crosssections. Jour. Asian Earth Sci. 116, 122-131
Bhattacharya, A.R., 1978. A mathematical expression for the length of a folded layer. Geosci. Journal, IV, pt. 2, 99-104.
Bhattacharya, A. R., 2008. Basement rocks of the Kumaun–Garhwal Himalaya: implications for Himalayan tectonics. Jour. of Earth Sci. India I (I), 1-10.
Chamyal, L. S., 1991. Stratigraphy of the Lesser Himalayan rocks in Kumaun. J. of Earth System Science 100, 293-306.
Chakrabarty, S.K., 2016. Geology of the HimalayanBelt:Deformation,Metamorphism, Stratigraphy. Elsevier.
Dieterich, J.H., Carter, N.L., 1969. Stress history of folding. Am. Jour. Sci. 263, 129-154.
Dubey, A.K., 2014. Understanding an orogenic belt: Structural Evolution of the Himalaya, Springer.
Elliott, D., 1965. The quantitative mapping of directional minor structures. J. Geol. 73, 865–880.
Hudleston, P.J., 1973. Fold morphology and some geometrical implications of theories of fold development. Tectonophysics 16, 1-46.
Hudleston, P.J., Holst, T.B., 1984. Strain analysis and fold shape in a limestone layer and implication for layer rheology. Tectonophysics 106, 321-346.
Jade, S., Mukul, M., Gaur, V.K., Kumar, K., Shrungeshwar, T.S., Satyal, G.S., Kumar, R., Dumka, Jagannathan, S., Ananda, M.B., Dileep Kumar, P., Banerjee, S., 2014. Contemporary deformation in the Kashmir-Himachal, Garhwal and Kumaon Himalaya: significant insights from 1995-2008 GPS time series. Jour. Geodesy 88, 539-557.
Jain, A. K., Anand, A., 1988. Deformational and strain patterns of an intracontinental collision ductile shear zone-an example from the Higher Garhwal Himalaya. J. Struct. Geol.10, 717-734.
Jain, A. K., Ahmad, T., Singh, S., Ghosh, S.K., Patel, R.C., Kumar, R., Agarwal, K.K., Perumal, R.J., Islam, R., Bhargava, O.N., 2012. Evolution of the Himalaya. Proc. Indian Nat. Sci. Acad. 78, 259-275.
Jain, A.K., Dasgupta, S., Bhargava, O.N., Israil, M., Perumal, R.J., Patel, R.C., Mukul, M., Parcha, S.K., Adlakha, V., Agarwal, K.K., Singh, P., Bhattacharyya, K., Pant, N.C., Banerjee, D. M., 2016. Tectonics and Evolution of the Himalaya. Proc. Indian National Sci. Acad. 82, 581-604, doi: 10.16943/ptinsa/2016/48469.
Joshi, M., Tiwari, A.N., 2009. Structural events and metamorphic consequences in Almora Nappe, during Himalayan collision tectonics. Jour. Asian Earth Sci. 34, 326-335.
Katiyar, V., Srivastava, H.B., 2012. Fold profile geometry of the rock of the area around Pithoragarh, Uttarakhand. Jour. of Scientific Research, Banaras Hindu University 56,19-24.
Lisle, R.J., 1992. Strain estimation from flattened buckled folds. J. Struct. Geol.14, 369–371.
Patel, R.C., Kumar, Y., Lal, N., Kumar, A., 2007. Thermotectonic history of the Chiplakot Crystalline Belt in the Lesser Himalaya, Kumaon, India: Constraints from apatite fission-track thermochronology. J. Asian Earth Sci. 29, 430-439.
Patel, R.C., Adlakha, V., Singh, P., Kumar, Y., Lal, N., 2011. Geology, Structural and Exhumation history of the Higher Himalayan Crystallines in Kumaon Himalaya, India. J. Geol. Soc. India 77, 47-72.
Ramsay, J.G., 1967. Folding and Fracturing of Rocks. McGraw Hill, New York,568.
Ramsay, J.G., Huber, M.I., 1987. The Techniques of Modern Structural Geology: Folds and Fractures, Vol. 2. Academic Press, London, 309–700.
Rao, D.R., Sharma, R., 2009. Petrogenesis of the Granitoid Rocks from Askot Crystallines, Kumaun Himalaya. Jour. Geol. Soc. India 74, 363-374.
Rao, D.R., Sharma, R., 2011. Arc magmatism in eastern Kumaun Himalaya, India: A study based on geochemistry of granitoid rocks. Island Arc 20, 500-519.
Shah, J., Srivastava, D.C., Joshi, S., 2012. Sinistral transpression along the Main Boundary Thrust in Amritpur area, Southeastern Kumaun Himalaya, India. Tectonophysics 532-535, 258- 270.
Roberts, D., Stromgard, K.E., 1972. A compression of natural and Experimental strain pattern around fold-hinge zones. Tectonophysics 14, 105-120.
Rupke, J.L., 1974. Stratigraphy and structural evolution of the Kumaun Lesser Garhwal Himalaya, Sedi. Geol. 11, 81-265.
Sanderson, D.J., 1976. The superposition of compaction and plane strain. Tectonophysics 30,35-54.
Singh, P., Patel, R.C., Lal, N., 2012. Plio-Plistocene in-sequence thrust propagation along the Main Central Thrust zone (Kumaon-Garhwal Himalaya,India): New thermochronological data. Tectonophysics 574-575, 193-203.
Srivastava, H.B., 1995. Two Dimensional Strain estimation from weakly deformed rocks. Annal. Tecto. IX, 3-6.
Srivastava, H.B., 2003. Strain determination from concentric folds. Tectonophysics 364, 237-241.
Srivastava, H.B., Sinha, L.K., 1987. Study of fold profile geometry in the rocks of Stengel area, Garhwal Himalaya, U.P., Bull. Ind. Geologists Asso. 20, 139-145.
Srivastava, H.B., Sinha, L.K., Katiyar, V., 2011. Mesoscopic structures from the area around Satengal, Lesser Garhwal Himalaya. Jour. of Scientific Research, Banaras Hindu University, 55, 25-34.
Srivastava, V., Gairola, V.K., 1997. Classification of multilayered folds based on harmonic analysis: example from central India. J. Struct. Geol. 19, 107–112.
Srivastava, V., Gairola, V.K., 1999. Geometrical classification of multi-layered folds.Tectonophysics 301,159-171.
Srivastava, V., Gairola, V.K., 2003. Recent classification schemes for multilayered folds: An overview. Milestones in petrology (Ed. Mohan, A.), Memoir of the Geological Society of India 52, 395-408.
Tewari, M., 2008. Additional Neoproterozoic sponge spicules from Gangolihat Dolomite, Kumaun Lesser Himalaya, India. Himal. Geol. 29, 49-55.
Tiwari, M., Pant, I., 2009. Microfossils from the Neoproterozoic Gangolihat Formation, Kumaun Lesser Himalaya: Their stratigraphic and evolutionary significance. J. Asian Earth Sci. 35,137-149.
Twiss, R.J., Moores, E.M., 2007. Structural Geology, W. H. Freeman, New York.
Valdiya, K. S., 1980. Geology of Kumaun Lesser Himalaya. Wadia Institute of Himalayan Geology.
Valdiya, K.S., Pande, K., 2009. Behavior of basement-cover decoupling in compressional deformation regime, northern Kumaun (Uttarakhand) Himalaya. Proc. Indian Nat. Sci. Acad. 75, 27-40.
Verma, A.K., Bhattacharya, A.R., 2011. Reorientation of lineation in central crystalline zone, Munsiari-Milam area of the Kumaon Greater Himalaya. J. Earth Sys. Sci.120, 449- 458.
Zagorčev, I.S., 1993. The geometric classification of folds and distribution of fold types in natural rocks. J. Struct. Geol.15, 243–251.

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Published

2019-07-25

Issue

Vol. 4 No. 2-2 (2019): Special Edition (Geology, Geomorphology and Tectonics of India)

Section

Special Edition (Geology, Geomorphology and Tectonics of India)

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