Friday, October 16, 2009 3:24:12 PM
If Chatterjee is right this could be the largest, multi-ringed impact crater the world has ever seen, with a diameter of ~500 km. The diameter of the so far known largest impact crater, the Vredefort Crater in South Africa has a diameter of about 300 km. Furthermore the Shiva crater has an age that makes it a suspect for the killing of the dinosaurs ca. 65 million years ago.
According to Chatterjee it is the remnant of a giant meteorite impact that left high-resolution stratigraphic signals in the sedimentary and volcanic rocks such as shocked quartz, iridium anomaly, nickel-rich spinels, sanidine spherules, magnetic nanoparticles, high pressure fullerenes, megatsunami deposits, and melt lavas. If the author and his team are right, this is the largest crater known on our planet. The bolide may have been perhaps 40 kilometres in diameter - as compared to the bolide of between 8 and 10 kilometres that hit Yucatan Peninsula, and is commonly thought to have killed the dinosaurs.
The impact was so powerful that it led to several geodynamic anomalies: it fragmented, sheared, and deformed the lithosphere mantle across the western Indian margin and contributed to major plate reorganization in the Indian Ocean. It initiated rifting between India and Seychelles in the west and created the Laxmi Ridge; it shattered the Indian plate easterly along the Narmada-Son Rift extending 1500 km across, dividing the Indian shield into a southern peninsular block and a northern foreland block. Because of topographic barrier of the Western Ghat Mountain range, the impact-triggered tsunami was restricted along the Narmada-Son Rift at the KT boundary.
The team hopes to go India later this year to examine rocks drill from the center of the putative crater for clues that would prove the strange basin was formed by a gigantic impact.
The rest of us are waiting to hear more.
PS of 21 October 2009:
The hypothesis met with sharp criticism. See
PS of 2 November 2009 - More about the Shiva Crater: