干旱区生态环境知识资源中心

This article presents chronological investigations on interfault fibrous gypsum using the technique of Electron Spin Resonance (ESR) dating, essentially to demonstrate the robustness of the technique as a dating tool on fibrous gypsum precipitates in a semi-arid region. Samples of fibrous gypsum collected from Katrol hill range, Kachchh consist of those from fractures and bedding planes, and those along the inferred fault plane. The slow progressive uplift along the region resulted in erosion, unloading and dissolution of near-surface evaporite deposits and formation of extensional joints parallel to bedding and across. These openings became favourable sites for the fibrous gypsum to develop perpendicular to the wall of factures as well as fault plane. ESR chronometry. studies deduce that gypsum growth along the bedding plane and fractures took place around 300 ka, while ESR dating studies on fault plane gypsum indicate an age around 70 ka. The young age of the normal fault plane indicates that it developed on account of the ongoing compressive stresses which resulted in normal faults perpendicular to the principal stress and later got immediately filled by sulphate-rich solutions. The ongoing compressive stresses active on the region have finally resulted in further uplift of the footwall back limb to its present topography.