“There have been previous reports attempting to link paleoseismicity, as recorded by soft-sediment deformation features, to impacts,” Tanner explained. “But this is the first instance of linking the Manicouagan impact to the stratigraphic record. I made the association between the impact and paleoseismicity in the Fundy Rift Basin, a sedimentary basin 700 km away from the impact site, and went looking for shocked quartz grains. Finding them allows us to place this impact into a stratigraphic context and look elsewhere to see if there are any significant biotic effects. So far, there don't seem to be any.”
Some geologists believe that most major biotic extinctions can be explained by impact events. However, there have been a number of impact events that have no relationship with extinctions. Geologists used to think the Manicouagan impact caused the Triassic-Jurassic extinctions, but U-Pb zircon dating of the impact melt proved it happened much earlier.
Tanner will present his findings “STRATIGRAPHIC RECORD IN THE FUNDY RIFT BASIN OF THE MANICOUAGAN IMPACT: BOLIDE WITH A BANG OR A WHIMPER?” at the Geological Society of America’s Northeastern Section Meeting in Springfield, Massachusetts, on March 26.
By Kara LeBeau, GSA Staff Writer
Contact information:
Lawrence H. Tanner,
Geography and Geosciences
Bloomsburg University
Bloomsburg PA 17815 USA
E-mail: lhtann@bloomu.edu
Phone: 570-389-4142
FAX: 570-389-3028
Abstract available at: http://gsa.confex.com/gsa/2002NE/finalprogram/abstract_31805.htm.
Northeastern Section, Geological Society of America
36th Annual Meeting
March 25-27, 2002
Sheraton Springfield Hotel
Springfield, Mass.
For information and help during the meeting, please see the media assistant at the GSA registration table or call 413-263-2185.