Tookoonooka is a large meteorite

Meteorite

A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...

 impact crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 (astrobleme) situated in southwestern Queensland

Queensland

Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. It lies deeply buried within Mesozoic

Mesozoic

The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...

 sedimentary rocks of the Eromanga Basin

Eromanga Basin

The Eromanga Basin is a large Mesozoic sedimentary basin in central and northern Australia. It covers parts of Queensland, the Northern Territory, South Australia, and New South Wales, and is a major component of the Great Artesian Basin...

 and is not visible at the surface.

Tookoonooka was discovered using seismic

Seismology

Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,...

 data collected during routine petroleum exploration

Oil exploration

Hydrocarbon exploration is the search by petroleum geologists and geophysicists for hydrocarbon deposits beneath the Earth's surface, such as oil and natural gas...

 and first reported in a publication in 1989, with proof of the impact theory coming from the discovery of shocked quartz

Shocked quartz

Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure , the crystalline structure of quartz will be deformed along planes inside the crystal...

 in drill core. Estimates of the crater diameter range from 55 km (34.2 mi) to 66 km (41 mi). The impact occurred during deposition of the Cretaceous

Cretaceous

The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 Cadna-owie Formation, the age of which is variously estimated at being between 123–133 Ma, or 115–112 Ma. Tookoonooka is associated with several small oil fields.

The seismic data reveal a similar nearby structure of the same age referred to as Talundilly. Although it seems likely that Tookoonooka and Talundilly are paired impact craters, proof that the later is of impact origin is not possible without drilling.