Ordovician covers the time between 490 and 434 million years ago, just after Cambrian period. During Ordovician, the climate got cooler, probably pretty much as it is today.
Australia was still connected to Gondwana continent. Its eastern third was still under the deep ocean, although inland north Queensland, Gulf Savannah and Cape York peninsula had by now emerged from the water. Across central Australia, the shallow sea called Larapinta Seaway crossed the continent from west to east and divided it to a southern and a northern part.
Sedimentation in the shallow sea produced limestones and sandstones composed from sand eroded from the Precambrian rocks. In the southern part, near Canberra, was a volcanic arc that produced mainly andesites.
NOTE: This website is written in British English, which is the English we use in Australia. You will find words like "traveller", "harbour" and "realise", and they are all correct in the language used in Australia.