EVIDENCE FOR A LATE TRIASSIC MULTIPLE IMPACT EVENT ON EARTH

Evidence for the collision of fragmented comets or asteroids with some of the larger (jovian) planets and their moons is now well establishe d following the dramatic impact of the disrupted comet Shoemaker-Levy 9 with Jupiter in 1994 (ref. 1). Collisions by fragmented objects resu lt in multiple impacts that can lead to the formation of linear crater chains, or catenae, on planetary surfaces(2). Here we present evidenc e for a multiple impact event that occurred on Earth. Five terrestrial impact structures have been found to possess comparable ages (similar to 214 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 stru ctures are plotted on a tectonic reconstruction of the North American and Eurasian plates for 214 Myr before present, the three largest stru ctures (Rochechouart, Manicouagan and Saint Martin) are co-latitudinal at 22.8 degrees (within 1.2 degrees, similar to 110 km), and span 43. 5 degrees 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 dec lination with Rochechouart and Saint Martin, respectively. We therefor e 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.