Reworked Carboniferous Palynofossils from Panna Formation, Bombay Offshore Basin: Clue to a Hidden Target for Hydrocarbon Exploration

A reworked Carboniferous palynofossil assemblage from the subsurface sections of the Early Eocene basal clastics of Panna Formation, Bombay offshore basin has been discovered. This assemblage is recorded at various stratigraphic levels of the studied well sections along with the indigenous Early Eocene dinoflagellate cysts and sporepollen taxa. Initial studies have suggested more than one possibility of explaining the provenance of reworked sediments containing the Carboniferous palynofossils. One possibility is that these might have been derived from the erosion of Early Palaeozoic sediments present in the Deccan volcanic province. Alternatively, these sediments could result from long distance transport of reworked material from Saudi Arabia-Africa region in the west which were deposited in the Bombay offshore region during Early Eocene. Available evidences, for and against these two possibilities are discussed. Our studies show that the Carboniferous reworked assemblage is confined to the Heera-Bassein block. The reworking in the Panna Formation might have taken place by palaeorivulets cutting through the thin Deccan Trap flows, exposed in the faulted blocks. A model explaining the mechanism of reworking has been presented. Organic matter studies indicate the presence of mature sediments below the Deccan Trap, which suggest a possible hidden basin to be a new exploration target for hydrocarbon.