Australia: The Land Where Time Began

A biography of the Australian continent 

Arcadia Formation

Red beds, predominantly red shales up to 500 m thick, interbedded with cross-bedded sandstones (formed by stream channels) comprise the Arcadia Formation that outcrops in the Bowen Basin of southeast Queensland. Flowing across vegetated floodplains meandering streams deposited sediments that became the Arcadia Formation. Oxidising conditions and a palaeoclimate that was semiarid, probably with seasonal fluctuations of temperature  that were marked, and possibly summer monsoons, is indicated by the red colour of the sediments. During the earliest Triassic the palaeolatitude of the Bowen Basin is suggested by Kear to have been more than 80^o S and to have been several hundred kilometres inland from the coast. An age of predominantly of Induan-Olenekian is indicated by the spore and pollen record, as well as macroflora and vertebrates.

The Arcadia Formation (Rewan Group) is one of the earliest fossil sites of Triassic age in Australia. It is comprised of terrestrial sediments in a series that covers the time period from the latest Permian to the Early Triassic in inland Australia, a time when the transition occurred from the moist swampy conditions in which coal formed to a seasonal climate that characterised the interior of the continent in the Early Triassic that was more arid.

Sources & Further reading

1. Kear, B.P. & Hailton-Bruce, R.J., 2011, Dinosaurs in Australia, Mesozoic life from the southern continent, CSIRO Publishing.