1. Introduction The accommodation history of rift basins is strong- ly linked to their mechanical subsidence regime with episodic pulses of extension that create space for sediment accumulation at very fast rates (Mar- tins-Neto & Catuneanu, 2009). A sequence-strati- graphical model for rift basin defnes the dominant stratigraphical patterns that are commonly encoun- tered in tectonic settings and provides a framework for understanding the process-response relation- ship between controls on accommodation and the resultant stratigraphical architecture of rift basins (Martins-Neto & Catuneanu, 2009). The Kachchh Basin in western India is a peri-con- tinental embayment in an east-west-trending gra- ben between the Nagar Parkar-Allah bund and North Kathiawar faults, which is flled by synrift sedimentary rocks within two major cycles: a trans- gression with the opening of the rift and a regression with rift failure during the Late Cretaceous (Biswas, 1999). The Jurassic strata formed in a shallow-ma- rine, inner-shelf environment during transgression (Biswas, 1999), where normal faults controlled the creation of accommodation space for syntectonic deposition in a rift basin (Biswas, 1983, 2005). The basin margin successions have been stud- ied by various workers for their lithostratigraphy Geologos 25, 1 (2019): 31–41 DOI: 10.2478/logos-2019-0003 Genetic sequence stratigraphy on the basis of ichnology for the Middle Jurassic basin margin succession of Chorar Island (eastern Kachchh Basin, western India) Jehova L. Darngawn, Satish J. Patel*, Jaquilin K. Joseph, Apuva D. Shitole Department of Geology, The M.S. University of Baroda, Vadodara, Gujarat, India *corresponding author, e-mail: sjpgeology@gmail.com Abstract Synrift basin margin successions are greatly infuenced by eustatic sea level changes, tectonics and accommodation space flled in by sediments. The Middle Jurassic (Bajocian–Callovian) of Chorar Island (western India) comprises a ~109-m-thick synrift basin margin succession of clastic, non-clastic and mixed siliciclastic-carbonate rocks which are here analysed and categorised into nine lithofacies. The succession is bioturbated to varying intensities; 16 identifed ichnogenera can be assigned to environmentally related groups of fve trace fossil assemblages, which include Gyro- chorte, Hillichnus, Rhizocorallium, Skolithos and Thalassinoides. These ichnoassemblages document the Skolithos and Cruz- iana Ichnofacies which marks a change in energy conditions, sedimentation dispersal patterns and bathymetry in a shal- low-marine environment. The Bajocian–Callovian succession is further analysed on the basis of sedimentological and ichnological data that show two genetic sequences consisting of Transgressive Systems Tract and Highstand Systems Tract bounded by Maximum Flooding Surface. The synrift basin margin succession of the Middle Jurassic of Chorar Island shows cyclicity in deposition; the Bajocian–Bathonian succession represents progradational to retrogradational coastlines, while the Callovian succession documents an aggrading progradational coastline. Key words: Synrift basin, Bajocian–Callovian, lithofacies, ichnofacies, base level Genetic sequence stratigraphy on the basis of ichnology for the Middle Jurassic basin margin succession in Chorar Island Jehova L. Darngawn et al.