Bedrock gorges in the central mainland Kachchh: Implications for landscape evolution

摘要

Kachchh possesses a fault-controlled first-order topography and several geomorphic features indicative of active tectonics. Though coseismic neotectonic activity is believed to be the major factor in the evolution of the landscape, detailed documentation and analysis of vital landscape features like drainage characteristics, bedrock gorges and terraces are lacking. The present study is a site-specific documentation of gorges developed in the central part of the mainland Kachchh. We analyzed and interpreted four gorges occurring on either side of Katrol Hill Fault (KHF). The Khari river gorge is endowed with six levels of bedrock terraces, some of which are studded with large potholes and flutings. Since no active development of potholes is observed along the rivers in the present day hyper-arid conditions, we infer an obvious linkage of gorges to the humid phases, which provided high energy runoff for the formation of gorges and distinct bedrock terraces and associated ero-sional features. Development of gorges within the miliolites and incision in the fluvial deposits to the south of the KHF indicates that the gorges were formed during Early Holocene. However, ubiquitous occurrence of gorges along the streams to the south of KHF, the uniformly N40°E trend of the gorges, their close association with transverse faults and the short length of the exceptionally well developed Khari river gorge in the low-relief rocky plain to the north of KHF suggests an important role of neotectonic movements.