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Structure and tectonics of Kachchh region of western India: An appraisal

R. V. Karanth
Department of Geology, Faculty of Science, M. S. University of Baroda
Vaodara - 390002

Introduction
The Kachchh region is an excellent example of a tectonically controlled landscape whose physiographic features are the manifestation of the earth movements along the tectonic lineaments of the Pre-Mesozoic basinal configuration, that was produced by the primordial fault pattern in the Precambrian basement (Biswas, 1971; 1974). Major E-W structural orientations have played pivotal role in its geomorphic evolution. This region of western Indian subcontinent has a unique history of continued tectonism since the advent of Mesozoic, and its landscape, comprising an assemblage of various tectonogenic geomorphic features is the reflection of movements along the major E-W longitudinal faults viz. Katrol Hill Fault (KHF), Kachchh Mainland Fault (KMF), Banni Fault (BF), Island Belt Fault (IBF), Allah Band Fault (ABF) and Nagar Parkar Fault (NPF) (Fig 1).


Fig 1. Structural Map of Kachchh (after, Biswas, 1987)

These faults were reactivated from time to time (Biswas, 1970, 1980, 1982,1987 and Karanth, 2000). Apart from the clear evidences in the form of diversity of landforms, Paleoseismicity record and several seismic events point to a continued tectonic activity. As a result the Kachchh has experienced several episodes of earth movements due to successive unidirectional tectonic upheavals along these lineaments all throughout the Cenozoic. These have not only contributed to the evolution of a youthful topography, but have further accentuated the structural pattern (Biswas, 1971; Kar, 1988). We have observed that numerous oblique cutting subordinate faults developed during various tectonic events trending N-S, NNE-SSW, ENE-WSW and WNW-ESE have controlled the trends of major drainage network both in the rocky upland as well as in the alluvial tract.

The Kachchh landscape comprises an array of tectonogenic geomorphic elements and is a manifestation of uplifts and residual depressions. Elevated landforms are the areas occupied by Mesozoic and Tertiary rocks, whereas the residual depressions or low-lying regions between the uplifts consist of Quaternary sediment successions marked alluvial river terraces in the rocky mainland and the mud-flats and salt pans in the Great and Little Ranns and Banni Plains. The general forms of the uplifts are marked by domes and asymmetric anticlines, which are confined to the south of the major faults (Fig. 1). All major uplifts are bounded, at least on one side, by a fault or a sharp monoclinal flexure, and on the other side by gently dipping peripheral plains, the strata (Tertiary) in which dip gently into the surrounding residual depression (Biswas, 1980). It is observed that the uplifts exposing folded Mesozoic rocks (Middle Jurassic-Lower Cretaceous), however, are not simple broad-topped upwarps with a faulted margin. They are complicated by flexures along the bounding faults and by secondary uplifts along faults with accompanying flexures within them.

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