Geological evolution of Victoria

This is a very simplified, generalised depiction of the major rock-forming events in Victoria.

Geological time scale

Geological time scale
Victorian rocks are mostly Phanerozoic in age so formed late in the earth’s history. There are virtually no examples of Precambrian rocks that represent the first 4,000,000,000 years of the earth’s history. By volume and aerial extent (although much is under thin cover), the predominant rocks in Victoria formed during the Ordovician.


Cambrian to Ordovician
During the Cambrian, Victoria was like the Atlantic Ocean. Oceanic crust (olive green in the accompanying figures) formed as the earlier continents drifted apart. Rivers and river delta systems to the west fed dumped sediments (sand and clay particles) out into the ocean. An example of a preserved part of the shoreline and delta systems is the Grampians. Analogies are the Niger River Delta or the Mississippi Delta today. The sand and clay particles eventually settled on the ocean floor. Through the late Cambrian and Ordovician, thick piles of sediment accumulated on the ocean floor, these are known as turbidite deposits (light blue and yellow). This pile of sediments make up the majority of Victoria (by volume and area) today.


Continents collided in the Silurian and the vast pile of turbidites was folded and faulted to create vast mountain ranges. A similar process today is creating the Himalaya’s as the Indian Plate crashes into the Asia Plate.


Towards the end of the mountain building as the crust thickend from the folding, the lower crust began to melt and the molten magma rose up towards the surface. It mostly cooled and crystallised beneath the surface forming granites (red). On rare occasions, the molten rocked reached the surface and formed volcanoes (such as Mt Macedon).


During a period of colder climate, Australia experienced a big freeze during the Permian. Glaciers scoured Victoria and some pocket remains of them (dark blue) can be found in central Victoria. During this time, southern Australia was connected to Antarctica.


Cretaceous to Recent
Southern Australia/Antarctica began to crack and separate. Large faults developed and the two continents began to pull away from each other. Downthrown faults along the southern edge of Australia filled with sediments, including limestone sandstone, shale and coal (light green). The climate changed and Victoria warmed resulting in higher rates of erosion. Widespread river gravels (yellow) were dispersed across central Victoria. Basaltic volcanoes (orange) erupted and in part covered the ancient river system. Many volcanic cones are prominent in southwestern Victoria today.