Rochechouart crater

Rochechouart crater

Map of the crater
Impact crater/structure
Confidence Confirmed[1]
Diameter 23 kilometres (14 mi)[1]
Age 202.7 ± 2.2
Exposed Yes
Drilled N
Location
Coordinates 45°49′27″N 0°46′54″E / 45.82417°N 0.78167°E / 45.82417; 0.78167
Country France
Rochechouart crater

Location of the Rochechouart crater in France

The Rochechouart crater is an impact crater tentatively centered at the hamlet of La Judie 4 km (2.5 mi) west of Rochechouart, France. Its original diameter before erosion is thought to have been about 20–30 km (12–19 mi).[2] Its most recent age estimate is 202.7 ± 2.2 million years ago,[3][4] placing it in the Rhaetian, close to the Triassic-Jurassic boundary.[5] 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.[5]

The crater's 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 whose nature was proved by the impact effects on the rocks, without any circular topographic features being visible.

Hypothetical multiple impact event

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, suggested 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.[2] 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. [6]

References

  1. 1 2 "Rochechouart". Earth Impact Database. University of New Brunswick. Retrieved 2016-02-06.
  2. 1 2 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
  3. ↑ 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.
  4. ↑ Jourdan, F., Reimold, W.U., Deutsch, A., 2012. Dating terrestrial impact structures. In: Jourdan, F., Reimold, W.U. (Eds.), Impact! Elements 8, 49–53.
  5. 1 2 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.
  6. ↑ Steele, Diana (19 March 1998). "Crater chain points to impact of fragmented comet". University of Chicago Chronicle.
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