Original paper

Tectonic geomorphology and evidence for active tilting of the Bela, Khadir and Bhanjada islands in the seismically active Kachchh palaeorift graben, Western India

Chowksey, V.; Maurya, D.M.; Khonde, N.; Chamyal, L.S.

Abstract

The Bela, Khadir and Bhanjada islands form a part of a linear chain of four major islands bound by the E-W trending Island Belt Fault (IBF) in the northern part of the seismically active Kachchh palaeorift basin. The islands are discrete tilt blocks comprising south dipping Mesozoic and Neogene rocks and are practically uninvestigated as far as their geomorphic characteristics and neotectonic activity along the IBF is concerned. The islands abruptly rise above the rann surface which is a flat salt encrusted surface representing the floor of the Holocene sea and presently having an average elevation of ∼5 m amsl. The major geomorphic components of the Bela, Khadir and Bhanjada islands studied are the north facing escarpment forming the northern margins of the islands, south sloping tectonically controlled backslopes, raised intertidal flats, notches and other marine erosional features attributed to the palaeo-sea that occupied the rann surface until ∼2 ka. The crest of the northern escarpments form major drainage divide between the short north flowing drainages and the south flowing drainages developed over the backslopes. The raised intertidal flats exhibit terraced surfaces that are tilted southwards and comprise mainly laminated clayey silts with thin layers of fine sand. In addition, erosional features like two levels of notches, platforms and sea caves are observed along the base of the northern escarpments. The presence of raised marine depositional and erosional features at the base of the escarpments point to mid-late Holocene uplift of the islands in a tilted manner due to tectonic activity along the IBF.

Keywords

tectonic geomorphologytilted blockraised marine landformsnotchesholoceneisland belt fault (ibf)kachchhwestern india