Global InformationAcraman impact structure information
| Acraman crater | |
|---|---|
 Acraman lake (circle), ringed by Lake Gairdner and others, outlining the Acraman crater depression | |
| Impact crater/structure | |
| Confidence | Confirmed |
| Diameter | up to 90 km (56 mi) |
| Age | ~590 Ma Late Ediacaran |
| Exposed | Yes |
| Drilled | No |
| Bolide type | Chondrite |
| Location | |
| Location | Gawler Ranges |
| Coordinates | 32°1′S 135°27′E / 32.017°S 135.450°E |
| Country | Australia |
| State | South Australia |
  Location of the impact structure in South Australia | |
Acraman impact structure is a deeply eroded impact crater in the Gawler Ranges of South Australia.[1] Its location is marked by Lake Acraman, a circular ephemeral playa lake about 20 kilometres (12 mi) in diameter. The discovery of the impact structure and independent discovery of its ejecta were first reported in the journal Science in 1986.[2][3] The evidence for impact includes the presence of shatter cones and shocked quartz in shattered bedrock on islands within Lake Acraman.
The impact structure is deeply eroded, and its original size must be inferred by indirect means. Some authors estimate an original diameter of up to 85 to 90 kilometres (53 to 56 mi),[4] while other suggest a smaller size, perhaps only 35 to 40 kilometres (22 to 25 mi), closer to that of the depression in which Lake Acraman is centred.[5] The larger size estimate would imply an energy release of 5.2 × 106 megatons of TNT.[4]
The impact event is estimated to have occurred about 590 million years ago during the Ediacaran; this age is not derived from the crater itself but from the position of ejecta within nearby sedimentary basins.[4]
The Lake Acraman Impact Structure is listed on the South Australian Heritage Register.[6]
- ^ "Acraman". Earth Impact Database. Planetary and Space Science Centre University of New Brunswick Fredericton. Retrieved 9 October 2017.
- ^ Williams, G.E. (1986). "The Acraman Impact Structure: Source of Ejecta in Late Precambrian Shales, South Australia". Science. 233 (4760): 200–3. Bibcode:1986Sci...233..200W. doi:10.1126/science.233.4760.200. PMID 17737291. S2CID 30059305.
- ^ Gostin, V.A.; Haines, P.W.; Jenkins, R.J.F.; Compston, W.; Williams, I.S. (1986). "Impact Ejecta Horizon Within Late Precambrian Shales, Adelaide Geosyncline, South Australia". Science. 233 (4760): 198–200. Bibcode:1986Sci...233..198G. doi:10.1126/science.233.4760.198. PMID 17737290. S2CID 11307364.
- ^ a b c Williams, G.E.; Gostin, V.A. (2005). "Acraman-Bunyeroo impact event (Ediacaran), South Australia, and environmental consequences: twenty-five years on". Australian Journal of Earth Sciences. 52 (4–5): 607–620. Bibcode:2005AuJES..52..607W. doi:10.1080/08120090500181036. S2CID 128751351.
- ^ Shoemaker, E.M.; Shoemaker, C.S. (1996). "The Proterozoic impact record of Australia". AGSO Journal of Australian Geology and Geophysics. 16: 379–398. Bibcode:1990LPICo.746...47S.
- ^ "Lake Acraman Impact Structure". South Australian Heritage Register. Department of Environment, Water and Natural Resources. Retrieved 26 June 2017.