Wallumbilla Formation

The Wallumbilla Formation is an Aptian geologic formation found in Australia. Plesiosaur remains are among the fossils that have been recovered from its strata.
Description.
The formation is present in the Northern Territory, Queensland, South Australia, and New South Wales. It is a sedimentary unit, principally made up of mudstone and siltstone, with calcareous concretions. Its maximum thickness is 600 metres. Its age is somewhere from Aptian to Albian, that is between 125 and 101 Mya. The formation is part of the Wilgunya Sibgroup, which in turn is part of the Rolling Downs Group of the Eromanga and Surat Basins. The named beds are the Coreena, Doncaster, Jones Vally, Ranmoor, and Trimble Members.