Rochechouart crater

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Artist's rendition of Rochechouart crater shortly after its formation

Rochechouart is an impact crater in France.[1] Its diameter is estimated to be about 21 km (13 mi). Its most recent age estimate is 201 ±2 million years ago,[2] placing it close to Triassic-Jurassic boundary.[3] Since then the crater has been deeply eroded, and no trace of its original surface morphology is visible. The crater appears to be too small to account for the Triassic–Jurassic extinction event.[3]

A 30 cm (12 in)-sized shatter cone in the Saint Gervais granite found near the centre of the impact

Its centre is tentatively located at the hamlet of La Judie 4 km (2.5 mi) west of Rochechouart, in the Haute-Vienne département; its surface extent includes the communes and villages of Rochechouart, Chaillac, Étagnac, Pressignac, Lésignac-Durand, Saint-Quentin-sur-Charente, Chéronnac, Chassenon and Chabanais.

The remnants of this astrobleme have been a major subject of debate among geologists since their discovery in the early 19th century. The explanation was only given in 1969 by the French geologist François Kraut, who definitely proved the impact origin of the breccias.

The Rochechouart impact crater was the first crater the nature of which was proven by the determination of the impact effects on the rocks, without any circular topographic features being visible.

Hypothetical multiple impact event[edit]

It has been suggested by Geophysicist David Rowley of the University of Chicago, working with John Spray of the University of New Brunswick and Simon Kelley of the Open University, that Rochechouart may have been part of a hypothetical multiple impact event which also formed the Manicouagan crater in northern Quebec, Saint Martin crater in Manitoba, Obolon' crater in Ukraine, and Red Wing crater in North Dakota.[4] All of the craters had previously been known and studied, but their paleoalignment had never before been demonstrated. Rowley has said that the chance that these craters could be aligned like this due to chance are nearly zero.[5]

References[edit]

  1. ^ "Rochechouart". Earth Impact Database. University of New Brunswick. Retrieved 2009-08-16. 
  2. ^ Schmieder, M.; Buchner, E.; Schwarz, W. H.; Trieloff, M.; Lambert, P. (2010-10-05). "A Rhaetian 40Ar/39Ar age for the Rochechouart impact structure (France) and implications for the latest Triassic sedimentary record". Meteoritics & Planetary Science 45 (8): 1225–1242. Bibcode:2010M&PS...45.1225S. doi:10.1111/j.1945-5100.2010.01070.x. Retrieved 2011-11-18. 
  3. ^ a b Smith, Roff (2011-11-16). "Dark days of the Triassic: Lost world". Nature 47 (7373): 287–289. Bibcode:2011Natur.479..287S. doi:10.1038/479287a. Retrieved 2011-11-18. 
  4. ^ Spray, J.G., Kelley, S.P. and Rowley, D.B. (1998). "Evidence for a late Triassic multiple impact event on Earth". Nature, v. 392, pp. 171-173. Abstract
  5. ^ Steele, Diana (19 March 1998). "Crater chain points to impact of fragmented comet". University of Chicago Chronicle. 

External links[edit]

Coordinates: 45°49′27″N 0°46′54″E / 45.82417°N 0.78167°E / 45.82417; 0.78167