Geologist discovers oldest impact structure

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New Delhi: One of the oldest impact structures in the world, created by an asteroid of the size of about one km in diametre about 2,500 million years ago, has been discovered by an Indian geologist in Madhya Pradesh’s Shivpuri district.

The newly discovered Dhala structure, second in India after Lonar, has been named after the village near which it was discovered. It is the eroded remnant of the an impact structure with an estimated present day diametre of 11-km, the largest in Asia. Till date not a single confirmed impact structure has been reported from Japan and China.

“This is the largest confirmed impact structure reported between Mediterranean and south-east Asia,” Jayanta K Pati, the discoverer of the structure said. His discovery has been reported in the late August issue of the Meteoritics and Planetry Science journal of The Meteoritical Society published from the University of Arizona, USA.

It is the only confirmed structure discovered by an Indian in the subcontinent and Far East Asia. Until now, Lonar in Maharashtra was the only confirmed structure but it was discovered by a British Scientist and confirmed by the Americans.

Dhala impact structure spreads over 64 square km of area. There are only 175 known such structures in the world and most are located in North America, Australia and Eurasia. Lonar and Dhala are the confirmed structures in Asia.

Though, a four-km wide crater-like feature called Ramgarh structure in Rajasthan and Shiva structure in the Arabian sea have been suggested as being of possible impact origin, they have not been confirmed yet.

Pati, ex-Head of the Department of Earth and Planetary Sciences of Allahabad University, accidentally discovered it in 2005 while studying some rocks from Bundelkhand craton.

“During the study we found some signatures of shock metamorphism suggesting the presence of an impact structure. So, we send the evidences for their verification to W Uwe Reimold, University of Witwatersrand, South Africa in 2005,” he said.