The Murray Basin was forested throughout the Tertiary, becoming open woodlands and grasslands in Plio-Pleistocene time. Precipitation was very high through the early Tertiary, with step-like decreases beginning in the late Oligocene- early Miocene. In the mid-late Miocene. widespread rainforest disappeared and was replaced with eucalypt wet sclerophyll forest which was burnt on a regular basis. For a brief interval in the late Miocene- early Pliocene, there is a resurgence of Nothofagus (the Nothofagus phase) which forms a well defined stratigraphic horizon. The Nothofagus phase is well marked in the major river systems of the western slopes of the Eastern Highlands, but it has also been found in the western Murray Basin. The climate was wetter at this time, which is thought to correlate with the late Miocene- early Pliocene maximum marine transgression. An assemblage with a high chenopod type and Asteraceae pollen content is deceptively like modern assemblages of arid regions, but close examination reveals a salt-marsh environment associated with the early mid Miocene marine transgression. Throughout the Tertiary and into the early Pleistocene, the only indications of salinity are associated with marine / marginal marine environments. There is no evidence of dryland salinity, as seen today.