In the Dubbo Region the geological history spans a period of 450 million years and covers four separate episodes:
Fossils in the older rocks of the Lachlan Fold Belt are all of marine origin. Along the Molong Rise during Ordovician time, lime-secreting algae and corals formed fringing reefs in the shallow water around the volcanic islands. Beds of limestone created from these reefs outcrop in the Wellington area and east of Gollan. Fossils are rare due to the limestone mostly having been recrystallised.
For a more complete description of the Geology of Dubbo, see our book,Plants and Animals of the Dubbo Region