Letters to Nature

Nature 392, 171-173 (12 March 1998) | doi:10.1038/32397; Received 30 January 1998; Accepted 19 February 1998

Evidence for a late Triassic multiple impact event on Earth

John G. Spray1, Simon P. Kelley2 & David B. Rowley3

  1. Department of Geology, University of New Brunswick, Fredericton E3B 5A3, Canada
  2. Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK
  3. Department of Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, USA

Correspondence to: John G. Spray1 Correspondence and requests for materials should be addressed to J.G.S. (e-mail: Email: jgs@unb.ca).

Evidence for the collision of fragmented comets or asteroids with some of the larger (jovian) planets and their moons is now well established following the dramatic impact of the disrupted comet Shoemaker–Levy 9 with Jupiter in 1994 (ref. 1). Collisions by fragmented objects result in multiple impacts that can lead to the formation of linear crater chains, or catenae, on planetary surfaces2. Here we present evidence for a multiple impact event that occurred on Earth. Five terrestrial impact structures have been found to possess comparable ages (approx214 Myr), coincident with the Norian stage of the Triassic period. These craters are Rochechouart (France), Manicouagan and Saint Martin (Canada), Obolon' (Ukraine) and Red Wing (USA). When these impact structures are plotted on a tectonic reconstruction of the North American and Eurasian plates for 214 Myr before present, the three largest structures (Rochechouart, Manicouagan and Saint Martin) are co-latitudinal at 22.8° (within 1.2°, approx110 km), and span 43.5° of palaeolongitude. These structures may thus represent the remains of a crater chain at least 4,462 km long. The Obolon' and Red Wing craters, on the other hand, lie on great circles of identical declination with Rochechouart and Saint Martin, respectively. We therefore suggest that the five impact structures were formed at the same time (within hours) during a multiple impact event caused by a fragmented comet or asteroid colliding with Earth.