Ichnology of Early Cretaceous, cyclic bioturbated Ghuneri Member (Bhuj Formation) from the Kachchh Basin, western India

The Early Cretaceous Ghuneri Member (Bhuj Formation) is a prominent sandstone unit outcropping along the Kachchh-Rift Basin. The post-rift sediments of Ghuneri Member comprised asymmetrical bioturbated cycles deposited in a wave-dominated deltaic environment. An ideal bioturbated cycle included coarsening-up thickening-up cycles, varying from shale/siltstone/fine-grained sandstone to medium/coarse-grained massive to cross-bedded sandstones. The basinal scale outcrops offer an excellent opportunity to analyze ichnological variations spanning proximal to the distal part of the wave-dominated delta in Ghuneri Member. The paper deals with trace fossil data from twenty-six sections of Ghuneri Member, with twenty-eight ichnospecies from twenty-two ichnogenera. Ichnological data shows a moderate to high diversity trace fossils corresponding to ichno-assemblages of regim between fair-weather and storm-wave bases. Integration of ichnological data with sedimentological data indicates fluctuating wave and storm energy within normal marine conditions. The bioturbation style signifies the availability of colonization window as a prime reason for preserving bioturbation in wave-dominated settings. Thus, the cyclic units of Ghuneri Member offer better insight into the ichnology of the Early Cretaceous wave-dominated deltaic environment.