Manicouagan crater

Manicouagan crater
The crater in winter, photographed by Space Shuttle mission STS-9 in 1983 (north is to the lower right).
Impact crater/structure
Confidence	confirmed[1]
Diameter	100 kilometres (62 mi)
Age	214 ± 1 million years old (Triassic Period)
Exposed	Yes
Drilled	Yes
Location
Location	Rivière-aux-Outardes / Rivière-Mouchalagane, Quebec
Coordinates	51°23′N 68°42′W / 51.383°N 68.7°W / 51.383; -68.7Coordinates: 51°23′N 68°42′W / 51.383°N 68.7°W / 51.383; -68.7
Country	Canada
Manicouagan crater Location of the Manicouagan crater in Quebec
Topo map	Canada NTS 22N
Access	Quebec Route 389

The Manicouagan Crater is one of the oldest known impact craters and is located primarily in Manicouagan Regional County Municipality in the Côte-Nord region of Québec, Canada,^[1] about 300 km (190 mi) north of the city of Baie-Comeau. Its northernmost part is located in Caniapiscau Regional County Municipality. It is thought to have been caused by the impact of a 5 km (3 mi) diameter asteroid about 215.5 million years ago (Triassic Period).^[2] It was once thought to be associated with the end-Carnian extinction event, but the Carnian-Norian boundary is now known to be much older, around 228 million years ago. ^[3]

The crater is a multiple-ring structure about 100 km (60 mi), with its 70 km (40 mi) diameter inner ring its most prominent feature; it contains a 70 km (40 mi) diameter annular lake, the Manicouagan Reservoir, surrounding an inner island plateau, René-Levasseur Island. It is the earth's fifth largest confirmed impact crater.^[4]

Hypothetical multiple impact event

It has been suggested that the Manicouagan crater may have been part of a hypothetical multiple impact event which also formed the Rochechouart crater in France, Saint Martin crater in Manitoba, Obolon' crater in Ukraine, and Red Wing crater in North Dakota. 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 the five craters formed a chain, indicating the breakup and subsequent impact of an asteroid or comet^[5], similar to the well observed string of impacts of Comet Shoemaker-Levy 9 on Jupiter in 1994.

Kelley had developed a technique to precisely date impact craters, using laser argon-argon dating of the glass formed by the impacts, and cited stratigraphic evidence to support an older age of 215 ± 25 Myr (Late Triassic). 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 5,000 km (3,100 mi) 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.^[6]

See also

• Manicouagan Reservoir

Notes

1. ^ ^{a b} "Manicouagan". Earth Impact Database. University of New Brunswick. http://www.passc.net/EarthImpactDatabase/presqu%27ile.html. Retrieved 2009-08-19. 
2. ^ Ramezani, J., S. A. Bowring, M. S. Pringle, F. D. Winslow, III, and E. T. Rasbury (2005). "The Manicouagan impact melt rock: a proposed standard for intercalibration of U-Pb and 40Ar/39Ar isotopic systems". 15th V.M. Goldsmidt Conference Abstract Volume, p. A321.
3. ^ Furin, S., N. Preto, M. Rigo, G. Roghi, P. Gianolla, J. L. Crowley, and S. A. Bowring (2006). "High-precision U-Pb zircon age from the Triassic of Italy: implications for the Triassic time scale and the Carnian origin of calcareous nannoplankton and dinosaurs". Geology, v. 34, pp. 1009-1012. Link
4. ^ "Impact Structures listed by Diameter (Increasing)". PASSC. http://www.unb.ca/passc/ImpactDatabase/CIDiameterSort2.htm. Retrieved 19 August 2010. 
5. ^ 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
6. ^ Steele, Diana (19 March 1998). "Crater chain points to impact of fragmented comet". University of Chicago Chronicle. http://chronicle.uchicago.edu/980319/craters.shtml