Uplift induced structurally controlled landscape development: example from fault bounded Jumara and Jara domes in Northern Hill Range, Kachchh, Western India

摘要

The Kachchh palaeo-rift graben at the western continental margin of India is currently undergoing active coseismic deformation in response to the periodic release of NE-SW oriented compressive stresses along the E-W trending intra-basinal faults. The seismically active Kachchh Mainland Fault (KMF) is the largest intra-basinal fault that is characterized by a narrow zone comprising a chain of domes and anticlines forming the rugged hilly topography of the Northern Hill Range (NHR) in the upthrown block. The present paper deals with the Jumara and Jara domes which have received considerable attention with respect to the Mesozoic biostratigraphy, however, no study has been carried out on geomorphological and neotectonic aspects. The major geomorphological units in the area include a low relief but rugged structurally controlled topography over the domes, the KMF scarp, the precipitous Jaramara scarp, the back slope over the Jaramara scarp and the rugged hilly topography over the large Ukra intrusive body that shows a complicated structural contact relation with the Mesozoic rocks ranging from concordant to discordant. Our detailed field studies supplemented by geomorphological analysis using DEM, topographical profiles, drainage characteristics and longitudinal profiles reveal the dominant control of sustained uplift along the KMF under compression in the development of the present youthful and structurally controlled landscape. Our study also suggests that the imposing E-W trending Jaramara scarp is formed due to the long-term retreat of the KMF scarp in response to uplift, while the present low relief scarp along the KMF is largely the result of post-Miocene uplift. The incision in Quaternary miliolite deposits in the Jara river gorge, deeply incising nature of the rivers, several large and small knickpoints and scanty occurrence of Quaternary miliolite deposits indicate an uplift of similar to 25 m during the Late Quaternary time.