Palynological analyses of samples from the Fossil Hill area [of Flinders Diamonds' Calabrinda diamond exploration prospect], in the northern Willochra Basin, have indicated the presence of Late Miocene to Early Pliocene sediments correlated with the Monotocidites galeatus Zone. Floral evidence of a weak marine depositional influence suggests that the basin was open and active until the Early Pliocene, and that these young deposits could be part of a more extensive sedimentary cover (including the Walloway Basin). Such deposition would be contemporaneous with the orogenic activity taking place during Late Miocene to Early Pliocene time. A synthesis of the likely palaeoecology once present at Fossil Hill suggests that to begin with an open grassland developed, with rare woodlands and open forest. Then there ensued a severe restriction of drier rainforest and a reduction in the tree canopy cover of open forest communities in the area. Next the climate became unsuitable for trees as cooler conditions prevailed, and it is possible that the area came under the influence of a winter rainfall regime.