Deniliquin multiple-ring feature

Deniliquin New South Wales
Deniliquin
Coordinates	35°32′0″S 144°58′0″E

The Deniliquin multiple-ring feature is a distinct deeply buried structure in southeast Australia. It is named after the town of Deniliquin. Its characteristics suggest that it is associated with an asteroid impact structure of diameter 520 km (320 mi), which would make it the largest one on Earth, exceeding the largest known one, the Vredefort impact structure of about 300 km (190 mi) in diameter.^[1][2]

Description

Murray–Darling drainage Basin (Deniliquin is in the larger brown area)

It is located beneath the Murray Sedimentary Basin and partly beneath the Darling Sedimentary Basin, and centered about 32 km (20 mi) northwest of Deniliquin. The principal features of the Deniliquin structure are a multiple ring total magnetic intensity (TMI) pattern with the minimal TMI ring radius of 260 km (160 mi); a central quiet magnetic zone; circular Bouguer gravity patterns; an underlying mantle Moho rise about 10 km (6.2 mi) shallower than under the adjacent Tasman orogenic zone; and radial faults associated with magnetic and demagnetized anomalies. The above features suggest that the Deniliquin feature is a root zone of a large impact structure, a multi-ring impact basin.^[3] Its existence was proposed by Anthony Yeates somewhere between 1995 and 2000, basing in the magnetic patterns in the area.^[1] A 2022 paper by Glikson and Yeates further supports this suggestion basing on recent geophysical data, drill-hole samples and airborne magnetic data.^[3] As of 2023^[update], most evidence comes from the surface data. Further confirmation of the suggestion would require further deep drilling.^[1]

Dating

Its age is estimated between 514±5 Ma and 427–417 Ma.^[3] It was likely located in eastern Gondwana before it split off Australia.^[1] Glikson suggests that it could have triggered the c. 1.4 million years-long Late Ordovician (Hirnantian) glaciation and the corresponding mass extinction event (445.2 and 443.8 Ma), which eliminated about 85% of species.^[2]

See also

• List of impact craters on Earth

References

1. Glikson, Andrew (9 August 2023). "New evidence suggests the world's largest known asteroid impact structure is buried deep in southeast Australia". The Conversation. Archived from the original on 21 August 2023. Retrieved 21 August 2023. (also republished in Australian Geographic, August 16, 2023 )
2. Glikson, Andrew Yoram (June 2023). "An asteroid impact origin of the Hirnantian (end-Ordovician) glaciation and mass extinction". Gondwana Research. 118: 153–159. doi:10.1016/j.gr.2023.02.019. Retrieved 25 May 2023.
3. Glikson, Andrew Yoram; Yeates, Anthony N. (August 2022). "Geophysics and origin of the Deniliquin multiple-ring feature, Southeast Australia". Tectonophysics. 837. doi:10.1016/j.tecto.2022.229454. Retrieved 25 August 2023.