The Miria Formation is a

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

geologic

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

, in

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to ...

. Possible indeterminate

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ...

remains have been recovered from it, as well as those of sea turtles, and possible azhdarchid

pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the Order (biology), order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cre ...

s. The lithology of the unit consists of calcarenite with abundant phosphatic nodules. The formation is a layer between 0.6 and 2.1 metres in thickness, a surface deposited during the end of the Cretaceous in the late

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interv ...

period around sixty five million years ago. The composition is foraminiferal

calcisiltite Calcisiltite is a type of limestone that is composed predominantly, more than 50 percent, of detrital (transported) silt-size carbonate grains. These grains consist either of the silt-size particles of ooids, fragments of fossil shells, fragments o ...

and

calcarenite Calcarenite is a type of limestone that is composed predominantly, more than 50 percent, of detrital (transported) sand-size (0.0625 to 2 mm in diameter), carbonate grains. The grains consist of sand-size grains of either corals, shells, o ...

and is rich in

macrofossil Macrofossils, also known as megafossils, are preserved organic remains large enough to be visible without a microscope. The term ''macrofossil'' stands in opposition to the term microfossil. Microfossils, by contrast, require substantial magnific ...

s of a diverse range of species. The specimens of ammonites date the Miria Marl of the Giralia Anticline layer to a period of formation at a major extinction event in the Cretaceous. The formation shows the K/T boundary very distinctly, and is the only place on the Australian continent to present the globally correlated phenomenon. The site contains fossil remains of the ammonites that were widely dispersed across the globe in the Cretaceous and that confidently date the stratigraphy of the formation across the greatest known mass extinction event. The Miria Marl layer has revealed highly diverse fossil deposits of shark teeth and coral species that are also found in the former

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final st ...

n land masses in southern India and the Antarctic.

References

{{Reflist Geologic formations of Australia Cretaceous System of Australia Maastrichtian Stage Limestone formations Sandstone formations Siltstone formations Marl formations Shallow marine deposits Fossiliferous stratigraphic units of Oceania Paleontology in Australia Geology of Western Australia