Early Oligocene (Rupelian) Dinoflagellate Cysts and Calcareous Nannofossils from Lumpy Clay Member of Maniyara Fort Formation, Kutch, Gujarat, India

The Palaeogene succession of Kutch, Gujarat exhibits huge shallow marine carbonate deposits of Middle Eocene and Oligocene ages. These deposits were mainly dated on the basis of larger benthic foraminifers. The paucity of foraminifers in the intermittent units of the succession resulted in discrepancy in precise dating of these strata. Lumpy Clay Member of Maniyara Fort Formation is one such example. This is considered as unfossiliferous in terms of foraminifers and was dated on the basis of foraminiferal assemblages of underlying Basal and overlying Coral Limestone members. In the present study, palynological biostratigraphy is proposed for the Lumpy Clay Member exposed at Bermoti Village, in Kutch. On the basis of age-diagnostic calcareous nannofossil and dinoflagellate cyst assemblages, the studied succession has been dated as Middle Rupelian (~31 Ma). The palynological data suggests a shallow marine neritic depositional setting, occasionally swept by open oceanic water.