Discovery of distal ejecta from the 1850 Ma Sudbury impact event
William D. Addison, Kakabeka Falls, Ontario P0T 1W0, Canada; et al. Pages 193-196.
Impact ejecta has been found from the Sudbury, Ontario, Canada, structure, the second largest and third or fourth oldest extraterrestrial Earth impact site. At 1.85 billion years old, these Paleoproterozoic ejecta are three times older than the previous oldest dated ejecta linked to a specific impact (Acraman, Australia, 0.59 billion years old). It is also larger than the well-known Chicxulub, Mexico (0.065 billion years old) impact linked to the extinction of the dinosaurs and many other species. The debris (ejecta) studied here, landed 650 km west northwest of Sudbury near Thunder Bay, Ontario, Canada, and 875 km west of Sudbury near Hibbing, Minnesota, United States. This huge impact likely deposited debris all around Earth, but it is very difficult to find because so much of the evidence has been destroyed in the recycling of Earth's crust by plate tectonics. Life at the time of the Sudbury impact was confined to the oceans and consisted of unicellular and colonial unicellular organisms.Also noted:
A Jurassic-Cretaceous boundary age and mid-ocean-ridge¡Vtype mantle source for Shatsky RiseJ.J. Mahoney,et al. Geology 15:185-188.
Basalt sills were cored recently in Ocean Drilling Program Hole 1213B in the southern part of the rise. Dating of the basalic sills in the Shatsky Rise, a large oceanic plateau in the northwest Pacific.provides an important new age estimate of the boundary between two geological periods, the Jurassic and the Cretaceous; this age is 144.6 +/- 0.8 million years before present.
