Rochechouart crater

Rochechouart is an impact crater in France.

The crater diameter is still under debate but expected to be about convert|21|km|abbr=on and its current age estimate is given as 214 ± 8 million years, placing it in the Upper Triassic period. Since then the crater has been deeply eroded, and no trace of its original surface morphology is visible anymore.

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

The remnants of this astrobleme have been a big subject of debates 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 proven by the determination of the impact effects on the rocks, without any circular topographic feature visible.

Related impact events

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, discovered that Rochechouart was one of five craters in Europe and North America that formed a chain, indicating the breakup and subsequent impact of an asteroid or comet. The other craters are Manicouagan crater in northern Quebec, Saint Martin crater in Manitoba, Obolon' crater in Ukraine, and Red Wing crater in North Dakota.

Kelley had developed a technique to precisely date impact craters, using laser argon-argon dating of the glass formed by the impacts, and he and Kelley sought Rowley's help to determine how the craters were aligned when the impacts occurred, since due to plate tectonics, the locations have moved large distances in the intervening 214 million years.

Three of the craters - Rochechouart, Manicouagan and Saint Martin - formed a convert|5000|km|abbr=on chain at latitude 22.8° N, while Obolon' and Red Wing lay on identical declination paths with Rochechouart and Saint Martin respectively. 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. [Citation | last = Steele | first = Diana | author-link = | last2 = | first2 = | author2-link = | title = Crater chain points to impact of fragmented comet | newspaper = University of Chicago Chronicle | pages = | year = | date = 19 March 1998 | url = http://chronicle.uchicago.edu/980319/craters.shtml]

Notes

External links

* [http://fr.wikipedia.org/wiki/Astrobl%C3%A8me_de_Rochechouart-Chassenon The Rochechouart impact crater, at fr icon wikipedia: interesting illustrations. ]
* [http://www.virtual-geology.info/eurogeol/rochech.html The Rochechouart impact crater, at virtual-geology.info]
* [http://www.meteoritearticles.com/colrochechouart.html Rochechouart impactite gallery, at meteoritearticles.com]
* [http://www.impact-structures.com/france/rouchechouart1.htm The Rochechouart impact rocks, at impact-structures.com]
* [http://www.museum.hu-berlin.de/min/forsch/forschprojects/impact/rochechouart.asp?lang=1 Structural investigations and numerical modelling]
* [http://www.cieletespace.fr/front/default.asp?name=/front/savoir/archives/visu_article.asp?numBiblio=1522 Rochechouart redécouvre son cratère] (sensational article, not scientifically founded however...)
* [http://www.brgm.fr/divers/rochecho1.htm Une catastrophe écologique au temps des dinosaures]
* [http://perso.wanadoo.fr/groupejarc/chassenon/impact.htm L'impact de la météorite de Rochechouart]
* [http://membres.lycos.fr/astrojan/Robert.htm Rochechouart, un site géologique exceptionnel]
* [http://www.espacemeteorite.com Association "Pierre de lune" - manages a permanent exhibition about the crater]
* [http://www.unb.ca/passc/ImpactDatabase/ Earth Impact Database]