ABSTRACT

The Triassic Gosford Formation in the Sydney Basin, Australia, is interpreted as a fluvial deposit in in-channel and floodplain environments. The upward transitions from one sub-environment to another are plotted on a 5 5 matrix and a transition tree constructed. This suggests that the Gosford Formation accumulated in well defined depositional environments, the distribution and migration of which were controlled by a relatively small number of natural processes.

All the transitions in the matrix can be accounted for in terms of the fluvial in-channel processes of channel diversion, meander migration, meander cut-off and channel falling, and the overbank processes of floodplain construction and crevassing. This confirms the interpretation of the deposit as fluvial. The ratios of the transition frequencies supports the concept of deposition by streams of low to moderate sinuosity based on the relative proportions of free grained and coarse grained lithofacies,