Jointing and Fracturing Characteristics of Central Kachchh Mainland, Kachchh, Western India

Abstract

The studies carried out at different locations in Central Kachchh Mainland indicate that prolific jointing is conspicuous in Mesozoic and Cenozoic rocks. The present investigation aims at documenting the characteristic joint sets cutting the rocks of different age groups and explore their possible genetic implications. Detailed lineament analysis has been carried out to compare major lineament patterns in the area and the characteristic joint sets observed in the field. Rocks of all age groups are highly jointed, but most intensive jointing is seen in the Mesozoic litho·units. Five different joint sets can be deciphered by their average azimuthal distribution, i.e., N125°±10°, N60°±100, NI50°±100, N180°±100 and N90°±10°. The directional analysis shows that there are three general trends i.e. NNE-SSW, NW-SE and ESE-WNW, with other subsidiary directions. The length-azimuth relationship shows that the highest density of lineaments correspond to the length inbetween 800 m and 3000 m. NNE-SSW and NW-SE trending lineaments are dominant in the length range of 800 m to 3000 m. The most significant part of the length-azimuth analysis is that WNWESE lineaments are increasingly prominent as length increases. This is because of the fact that most of the major structures in Central Kachchh Mainland are oriented in WNW-ESE and E-W directional domains.

The genesis of NNE-SSW and NNW-SSE lineaments can broadly be correlated with the faults and fractures developed transverse to the major east-west trending structures. The occurrence of nearly E-W and N-S sets suggest their close association with the flexuring activity along the major and minor faults within the Katrol Hill Zone (KHZ). Presence of NNE-SSW, NNW-SSE, E-Wand N-S sets in the Mesozoic sediments of KHZ in general and in the Quaternary sediments along the eastern extremity of KHZ in particular suggests sustained tectonic instability in this region during the Quaternary.