Stratigraphy and Depositional Environment of Sediments of the Goradongar Formation, Goradongar Range, Patcham Island, Kachchh

The Middle Jurassic (Bathonian-Callovian) rocks of the Goradongar Formation of the Goradongar range ~144.4 m thick succession constitutes of Goradongar Flagstone, Gadaputa Sandstone, Raimalro Limestone and Modar Hill members in an ascending order. The successions contain variable thick bands of pure clastic (arenaceous), non-clastic (allochemic limestone), mixed siliciclastic-carbonate rocks, shales and intraformational conglomerates. Mixed siliciclastic-carbonate sediments dominate the succession which are further classified according to their compositional variation and identified as micritic sandstone, allochemic sandstone, sandy allochem limestone, micritic mudrock and sandy micritic. The mixed siliciclastic-carbonate succession of the formation is intercalated by shales; and at certain stratigraphic levels it becomes pure clastic or non-clastic. The nonclastic successions are further analysed for microfacies which includes pelloidal grainstone, bioclastic grainstone, bioclastic packstone, pelloidal packstone and oolitic packstone. These rock units are characterized by sedimentary structures such as planar laminations, cross bedding and ripple (wave and current) marks; while certain bands are highly fossiliferous and bioturbated which display change in depositional regime. Variation in sediment composition, textural immaturity, and associated sedimentary structures of the Goradongar succession indicate the fluctuations in rate of sediment supply, energy levels and bathymetric conditions; and suggest two depositional regimes: lower shoreface to offshore transition and offshore.