| Popis: |
The Early Cretaceous Ghuneri Member (Bhuj Formation) in the Kachchh Basin represents deposition in a wave-dominated deltaic environment. It is characterized by asymmetrical bioturbated cycles of low to high bioturbated sandstone units. Systematic ichnological analysis of the Ghuneri Member across Kachchh basin indicates twenty-four recurring trace fossils categorized in fair-weather and storm-weather trace fossil ichnoassemblages. Fair-weather ichnoassemblages consist of shallow tier Gyrochorte, Lockeia and Planolites, middle tier Paleophycus, Polykladichnus, Rhizocorallium, Rosselia, Taenidium, and deep tier Chondrites. Storm-weather ichnoassemblage comprises of middle to deep tier Arenicolites, Diplocraterion, Psilonichnus Skolithos, Ophiomorpha, and Thalassinoides along with occasional escape traces of Conichnus conicus. Based on ichnofabric analysis, five categories are delineated, namely (a) low bioturbated ichnofabric, (b) structureless sand ichnofabric, (c) bioturbated top ichnofabric, (d) high bioturbated units with glossifunguites ichnofacies surface and (e) amalgamated bioturbated unit ichnofabric. These ichnofabrics occur in cyclic order representing the taphonomic pathways for the genesis of bioturbation cycles in Early Cretaceous wave-dominated deltaic environment of Kachchh Basin. |
