Australia

Victoria is also characterized by a belt of old rocks upon which sediments have been deposited called the Lachlan geosyncline. Marine rocks were deposited in quiet water to great thicknesses in Victoria, forming black shales. Some of the sediment was built up by mud-laden currents from higher areas on the sea floor. These current-borne sediments have produced muddy sandstones called graywackes.

At the end of the Ordovician and early Silurian periods (about 425 million years ago) there was widespread folding of the Lachlan geosyncline called the Benambran orogeny. The folding was accompanied by granite intrusions and is thought to be responsible for the composition and texture of the rocks of the Snowy Mountains in Victoria, including Mt. Kosciusko, Australia's tallest peak at 7,310 ft (2,193 m).

The Melbourne trough in Victoria is full of Silurian graywackes and mudstones featuring graptolite fossils, cup or tube-shaped organisms with durable exoskeletons (shells) that congregated in colonies. Mid-Devonian strata (375 million years old) are abundant with armored fishes which are also found in central Australia, North America, Eurasia, and Antarctica. The sandstones of the Grampian Mountains in western Victoria were formed from the erosion of uplifted areas which were deposited in lakes and by rivers during the late Devonian, early Carboniferous periods (about 350 million years ago).