Australia: The Land Where Time Began

A biography of the Australian continent 

Evergreen Formation

The Evergreen Formation, southeast Queensland, is of fluviatile-lacustrine origin and is a characteristic sequence of the Lower Jurassic, that mainly outcrops in the southern part of the Surat Basin. A number of important vertebrate fossils have been found in this sequence. The fossil record from the Middle Jurassic of Australia is largely confined to the Bajocian -Bathonian. The authors1 suggest the Newmarracarra Limestone in the Perth Basin, of Bajocian age, is probably the most significant, representing an important palaeobiogeographical point of correlation for the Middle Jurassic of Australia. This site has produced many marine invertebrate fossils that are well-preserved. The Walloon Coal Measures from the Clarence-Moreton Basin-Surat Basin, of Bathonian to Callovian age, are important deposits as they contain many Jurassic terrestrial plants and rare vertebrates, mostly in the form of footprints. 

One of the earliest Jurassic sites in Australia, the sediments were deposited at this site in low-energy river systems, lakes and swamps that were widespread across central and eastern Australia in the later Early Jurassic. A series of basal quartzose sandstones, that grade upwards into siltstones and shales, comprise the Evergreen Formation. These are distributed sporadically throughout the Mulgildie Basin, the Eromanga Basin, but mainly in the Surat Basin, of southeastern Queensland. A progressive decline from the high-energy braided stream, that is characterised by the underlying Precipice Sandstone, to meandering rivers of low-energy, floodplains and lakes, represents the characteristic lithology. In the upper part of the unit extensive ironstone beds of the Westgrove Ironstone Member are suggested by the authors1 to indicate the possibility of a connection to the sea in the east by way of the Clarence-Moreton Basin.

Plant microfossils have been used to date the Evergreen Formation to the Pliensbachian-Toarcian.

Sources & Further reading

  1. Kear, B.P. & Hamilton-Bruce, R.J., 2011, Dinosaurs in Australia, Mesozoic life from the southern continent, CSIRO Publishing.
 
Author: M. H. Monroe
Email:  admin@austhrutime.com
Last updated 15/12/2011 


Jurassic Australia

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                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading