Lithofacies association and depositional environment of Late Jurassic-Early Cretaceous sequence (Jhuran and Bhuj formations) of central part of Kachchh mainland

Abstract

This paper is an attempt to understand the distribution of the lithofacies association, coarse clastic textural and mineralogical character and diagenetic nature in order to understand the provenance and depositional environment of the Late Jurassic to Early Cretaceous sequence representing the Jhuran and Bhuj formations of central part of the Kachchh Mainland where sufficiently good outcrops are present. The Late Jurassic Jhuran Formation is represented by interbedded shale-sandstone association (LFA-1), fossiliferous shale with thin s an d p it interbeds (LFA-2), sandstone with interlayered shale (LFA-3) and interbedded siltstone-shale association (LFA-4), where as the Early Cretaceous Bhuj Formation comprises of lithofacies cross-bedded sandstone association (LFA-5), interbedded sandstone-siltstone association (LFA-6). Siity sandstone with interlayered shale (LFA-7) and bioturbated sandstone lithofacies association (LFA-4). The palaeocurrent analyses of crossbedding structure indicate a southwesterly to southerly direction of sediment movement. The textural analysis of sandstones suggests unimodal to bimodal distribution and a medium tofine grained, moderate to well sorted, symmetrically skewed, sub-angular to sub-rounded nature of the frame work components. The depositional environments as interpreted from the present study include the shallow marine, littoral-pro-deltadelta front to lower deltaic plains-fluvial-upper deltaic plains for Jhuran and Buij formations, respectively. The mineral composition and the nature of depositional textures and diagenetic modification of the sandstone suggest a recycled orogenic provenance area located to the north and northeast possibly from the Nagar-Parkar massif and Aravallis, respectively.