Trypanites ichnofacies and its multifarious significance: A case study from the Miocene Boka Bil Formation of Manipur, India

Bioerosional structures are well preserved in the Miocene Boka Bil Formation, exposed in the Kaiphundai section, Thangjing Hill Range of Manipur, India. Eleven ichnospecies representing the Trypanites Ichnofacies, viz., Entobia cateniformis, E. ovula, Gastrochaenolites anauchen, G. cluniformis, G. lapidicus, G. orbicularis, G. ornatus, G. torpedo, Maeandropolydora sulcans, Trypanites solitarius and T. weisei, are recorded from the two sections of the Boka Bil Formation. Two distinctive ichnoassemblages, Entobia-dominated and Gastrochaenolites-dominated are recognised. The Entobia-dominated assemblage suggests relatively deeper marine conditions in the deeper part of the back reef or fore reef while the Gastrochaenolites-dominated assemblage points shallower marine conditions, underwater depth of a few metres in the back reef to patch-reef zone of a back-reef lagoon