Monday, 7 February
Growing Evidence for a Large Asteroid Hitting Cooper basin 300 million years ago?
Four months ago I reported a summary of the preliminary findings by the QGECE Reservoir Program leader Dr Tonguc Uysal and his research collaborator Dr Andrew Glikson that suggested a large asteroid hitting the Cooper basin 300 million years. They had a presentation at the AGEC 2010 on this topic and they have been working about it since then. Today I received an e-mail from Dr Glikson reporting on their recent work. It seems like their original conclusions are being supported by his work since then:
- Investigation of drill holes in Adelaide during 3 - 14 January indicates that the shock metamorphism of the East Warburton Basin sediments and volcanics extends over an area at least 220 km NS and 150 km EW. This implies a buried impact structure larger than 300-km in diameter.
- Seismic tomography research indicates the existence of a sharp crustal low velocity anomaly under the East Warburton Basin (Saygin and Kennett, 2010), in addition to the marked gravity and magnetic anomalies below the basin (Meixner, 1999, 2000).
I am excited about this study because it bears potential implications for the origin of radiogenic K-U-Th enrichment and high temperatures, such as measured under a 3.5–4.5 km-thick insulating sedimentary cover in the Nappamerri Trough between Moomba dome and Innamincka. As the readers of this blog would know very well, this is the region where geothermal gradients as high as 55-60oC/km were measured (Middleton, 1979; Wyborn et al., 2004; Radke, 2009). In this region temperatures of ~225oC occur at 5 km depth over an area about 79,000 km2 large. The presence of a highly radiogenic basement within 3-4 km of the surface is consistent with upward migration and reconcentration of large ion lithophile elements associated with an impact generated hydrothermal cell, as is the case in some impact structures, including Woodleigh (Glikson et al. 2005b), Shoemaker impact structure and Yarrabubba impact structure (Pirajno, 2005).
An interim report on the work of Glikson and Uysal is posted on our web site. Click here to download a copy. While this is a relatively long report, it makes very interesting reading. Glikson and Uysal are condensing it to a size which can be published asa scientific paper.
I should emphasise that this is still work in progress and while the evidence for a large impact is getting stronger every day still more research is needed. This result does not need to be limited to Cooper basin drill cores. An impact of dimensions indicated in this report will result in major ejecta fallout units and tsunami deposits, such as are likely preserved in drill holes and outcrops in the entire central Australia and beyond.
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Click here for the rest of the blog