Bluff Downs fossil site

This is because there is a minimum age control in the form of a basalt layer (the Bluff Downs Flow) directly overlies the fossiliferous deposit.

The fossils were likely deposited between 5.2 and 3.6 million years ago during the late Pliocene period,[2] which matches dates estimated through biocorrelation.

They form large plateaux which were noted by Twidale as peripherally dissected, and of a vesicular amygdaloidal nature with vivianite, zeolites and chalcedonic silica commonly found within amygdales.

The Allingham Formation, named by Archer and Wade in 1976, is a lake and stream deposit within the Nulla Basalt Province, containing the fossils which the Bluff Downs Local Fauna are attributed to.

There were several different depositional events[9] and analysis of the sediments suggests that during the early Pliocene, a stream widened to form a shallow lake.

The Bluff Downs Local Fauna, named and described by Archer in 1976, includes numerous vertebrate species found at the Bluff Downs Fossil Site,[2] many of which are similar to but slightly older than the Chinchilla fauna (associated with Chinchilla Fossil Site, also in Queensland), according to more ancestral physical features.

The Bluff Downs Local Fauna originally identified by Archer featured 22 taxa with 12 mammals,[10] but this has since been expanded by further discoveries at the site.

Other taxa of note include; The palaeoenvironment of Bluff Downs during the Pliocene featured large water bodies and riparian forests.

There was persistent freshwater in the region as fossils of Chara flora, crustaceans and fish have been found and short-necked chelids also indicate presence of well developed rivers, creeks and lagoons with abundant aquatic fauna.

This forest would have been river-based (riparian) rainforest, and formed a minor component of the palaeoenvironment, as the paucity of possum fossils despite the use of screen washing of sediments suggests.