Tookoonooka
Key facts
- Country
- Australia
- Diameter
- 55 km
- Age
- about 112 to 133 million years (Early Cretaceous)
- Location
- 27.12° S, 142.83° E
Nothing: the structure is deeply buried beneath the gibber plains of south-western Queensland.
Tookoonooka is a large buried impact structure about 55 to 66 km across in south-western Queensland, Australia. It is one of the largest impact structures in the country.
Discovery. The structure was found from seismic data gathered during routine exploration for oil and gas in the Eromanga Basin. The data showed a large round structure with a central uplift and a ring of faulted rock deep beneath the plains. It was first reported in 1989.
Proof of impact. Quartz grains with planar deformation features, the microscopic signature of shock, were found in drill core, confirming an impact.
What it hit. The impactor struck a sequence of Mesozoic sedimentary rocks of the Eromanga Basin, lying over older basement. The crater was buried by younger Cretaceous sediments.
Age. The impact happened while the Cadna-owie Formation, a Cretaceous sedimentary layer, was being deposited. Estimates of the age range from about 112 to 133 million years.
A sea-floor impact? At the time, a shallow inland sea was spreading across this part of Australia. Some geologists have linked unusual layers of broken rock in other parts of the basin to the impact.
Why it matters. Tookoonooka is one of several large buried craters in Australia found by the oil industry. Its broken rocks may also trap oil and gas. The impactor is unknown.
Did you know?
Tookoonooka was found in seismic data from oil and gas exploration.
It is one of the largest impact structures in Australia.
It formed in the Early Cretaceous, when a shallow sea was spreading across inland Australia.