Australia: The Land Where Time Began

A biography of the Australian continent 

Miria Formation

In Australia the Miria Formation is among the stratigraphically youngest known Cretaceous rocks to contain fossils. It is comprised of calcarenite (uncemented chalk) sediments deposited on the calm continental shelf that formed when the marine incursion into the Carnarvon Basin occurred in the Late Cretaceous. In the Miria Formation macrofossils are common, though many are incomplete. The authors1 suggest they may have been broken up by storm activity when deposition was occurring.

Outcrops of the Miria Formation can be recognised by phosphatic steinkerns, that are present in sediments that have been weathered, though the Miria Formation is typically not well exposed. In the Giralia Ranges to the south of Exmouth Gulf outcrops of the Miria Formation are most conspicuous, often being rich in fossils. An extremely diverse range of pelagic cephalopods and benthic molluscs are indicated by faunal records. Other fossils that have been found in the Miria Formation deposits are mosasaurs and sharks, as well as isolated bones of dinosaurs and pterosaurs. An age of the Late Masstrichtian is suggested  by the Ammonites and microfossils. Warm temperatures are indicated by plankton assemblages. 

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
Last Updated 17/12/2011
Triassic Australia
Jurassic Australia
Cretaceous Australia

Steinkerns -the fossilised outline of a hollow organic structure such as a skull or the shell of a mollusc that is formed by the compaction of mud or sediment inside the structure after which the actual structure is dissolved or disintegrates.  


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