In the cool wet winters of the Late Permian, Glossopteris trees were able to grow in the swampy ground.  They are thought to have been deciduous trees and their leaves produced large peat deposits which where later turned into coal beds.  The ground was also able to support ferns and mosses.

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Some of the coal beds, such as the Great North Seam, which lies under present day Sydney, are very thick. It is often more than 3m deep. Others seams only reached a few centimetres before they were buried by new sediment.