ABSTRACT
The Melbourne region is underlain by a thick conformable sequence of sedimentary marine silty and sandy rocks, deposited in a deep basin during the Silurian and Lower Devonian periods. Silurian and Middle Devonian rocks, forming the basement rocks of the Melbourne region, outcrop to the north and east of Melbourne, and are covered by Quaternary and Tertiary soils to the south and south east. Rocks of Silurian and Lower Devonian age were deposited in the Melbourne Trough in a continuous sequence of deep water sedimentation of muds, silts and sands. The fossil assemblages of the Ordovician and Silurian-Lower Devonian Periods enable the Periods to be sub-divided into units. The units commonly have distinctive lithological characteristics which govern in part the rock mass and rock substance properties. The name Melbourne Formation is proposed for the Upper Silurian rocks in the Melbourne area that were previously called the Dargile Formation.
