An Earth-Shaking Event
26 Mar 2002
(Source: Geological Society of America)
Geological Society of America
The Manicouagan impact site in Quebec, Canada, is about 100 km or 62 miles wide and is over 200 million years old. The impact may not have had a significant effect on life, but it did trigger a powerful seismic event as Lawrence Tanner from Bloomsburg University recently discovered in a deformed zone of the Fundy Rift Basin.
"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 presented 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
Lawrence H. Tanner,
Geography and Geosciences
Bloomsburg PA 17815 USA
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
For information and help during the meeting, please see the media assistant at the GSA registration table or call 413-263-2185.