Post by Max on Jul 17, 2007 20:58:21 GMT -3
Little piece of Sudbury found in Minnesota; But Laurentian professor skeptical of claim
Denis St. Pierre / The Sudbury Star
Local News - Tuesday, July 17, 2007 @ 09:00
A Laurentian University geologist says he is intrigued, but skeptical of a report that rock from the meteorite that created the Sudbury basin has been found 700 kilometres away in the United States.
Andrew McDonald, a geologist and professor in Laurentian's department of earth sciences, said he was surprised by Monday's report of the findings of a Minnesota geologist.
Geologist Mark Jirsa of the Minnesota Geological Survey reported he discovered the Sudbury-related rock along the Gunflint Trail in northeastern Minnesota.
Jirsa said he found an exposed rock layer containing large chunks of what he determined is debris from the meteorite impact that created the Sudbury basin 1.85 billion years ago.
"It's fairly dark rock," Jirsa told the Associated Press. "They look like concrete, but in this concrete you would (see) pieces of rock of all sizes and shapes and in all possible orientations."
The finding was made in May and was followed by weeks of analysis.
"I think the excitement for the people of Minnesota is that we are one place in the world where you can see evidence of an ancient meteorite impact," said University of Minnesota geology professor emeritus Paul Weiblen, who is studying the debris.
"This is the second-oldest and second-largest impact crater in the world," Weiblen told the AP.
McDonald said he was anxious to investigate the report, adding he would be shocked if rock from the Sudbury meteorite landed 700 kilometres away.
"With the distance to that particular site, a surface exposure of something like this might be a little dicey," McDonald said. "That's a good distance."
The so-called Sudbury breccia, the mineralized rock deposited by the meteorite, "has been found up to 60 kilometres outside Sudbury, but I'm not familiar with it being found that far away," he said.
Still McDonald said he could not absolutely discount the report from Minnesota.
"Not knowing what they've got, or how they're making the link to Sudbury, it's very difficult to say if what they have is truly related to Sudbury," he said.
"There are a lot of things that basically rely on interpretation and what one person sees is not necessarily what another person sees. So I'm not saying these fellows are wrong or they've done something incorrectly, I'm just saying the interpretation they make might not be the one other people would make, in which case it may be more debatable as to what they've actually got."
The rock found in Minnesota could be "something like a Sudbury breccia," he added.
If the Minnesota report is authenticated, "it would be a reflection of how explosive or energetic the impact was" from the Sudbury meteorite, McDonald said.
"But 700 kilometres is pretty darn far. If you think about it, you have material that is being thrown that kind of a distance. That would be quite remarkable in terms of the energy that would have been released from the impact of the meteorite.
"But I suppose if this is in fact something related to the Sudbury impact, it would clearly illustrate the enormity of the energy that was released by this impact."
The Sudbury basin is about 60 kilometres long and 30 kilometres wide. The basin is believed to be a small portion of a crater 240 kilometres in diameter created by the meteorite. As such, the crater would be second in size only to the Vredefort crater in South Africa, which has a diameter of about 300 kilometres.
The Sudbury area also features a second impact site from a meteor, McDonald noted.
"There are two impact sites side-by-side here in Sudbury," he said. "Lake Wanapitei is an impact structure. That was definitely formed by a meteorite impact, about 38 million years ago, whereas the Sudbury event was about 1.85 billion years ago.
"So they were considerably different in time, but the proximity of one to the other is quite remarkable."
Denis St. Pierre / The Sudbury Star
Local News - Tuesday, July 17, 2007 @ 09:00
A Laurentian University geologist says he is intrigued, but skeptical of a report that rock from the meteorite that created the Sudbury basin has been found 700 kilometres away in the United States.
Andrew McDonald, a geologist and professor in Laurentian's department of earth sciences, said he was surprised by Monday's report of the findings of a Minnesota geologist.
Geologist Mark Jirsa of the Minnesota Geological Survey reported he discovered the Sudbury-related rock along the Gunflint Trail in northeastern Minnesota.
Jirsa said he found an exposed rock layer containing large chunks of what he determined is debris from the meteorite impact that created the Sudbury basin 1.85 billion years ago.
"It's fairly dark rock," Jirsa told the Associated Press. "They look like concrete, but in this concrete you would (see) pieces of rock of all sizes and shapes and in all possible orientations."
The finding was made in May and was followed by weeks of analysis.
"I think the excitement for the people of Minnesota is that we are one place in the world where you can see evidence of an ancient meteorite impact," said University of Minnesota geology professor emeritus Paul Weiblen, who is studying the debris.
"This is the second-oldest and second-largest impact crater in the world," Weiblen told the AP.
McDonald said he was anxious to investigate the report, adding he would be shocked if rock from the Sudbury meteorite landed 700 kilometres away.
"With the distance to that particular site, a surface exposure of something like this might be a little dicey," McDonald said. "That's a good distance."
The so-called Sudbury breccia, the mineralized rock deposited by the meteorite, "has been found up to 60 kilometres outside Sudbury, but I'm not familiar with it being found that far away," he said.
Still McDonald said he could not absolutely discount the report from Minnesota.
"Not knowing what they've got, or how they're making the link to Sudbury, it's very difficult to say if what they have is truly related to Sudbury," he said.
"There are a lot of things that basically rely on interpretation and what one person sees is not necessarily what another person sees. So I'm not saying these fellows are wrong or they've done something incorrectly, I'm just saying the interpretation they make might not be the one other people would make, in which case it may be more debatable as to what they've actually got."
The rock found in Minnesota could be "something like a Sudbury breccia," he added.
If the Minnesota report is authenticated, "it would be a reflection of how explosive or energetic the impact was" from the Sudbury meteorite, McDonald said.
"But 700 kilometres is pretty darn far. If you think about it, you have material that is being thrown that kind of a distance. That would be quite remarkable in terms of the energy that would have been released from the impact of the meteorite.
"But I suppose if this is in fact something related to the Sudbury impact, it would clearly illustrate the enormity of the energy that was released by this impact."
The Sudbury basin is about 60 kilometres long and 30 kilometres wide. The basin is believed to be a small portion of a crater 240 kilometres in diameter created by the meteorite. As such, the crater would be second in size only to the Vredefort crater in South Africa, which has a diameter of about 300 kilometres.
The Sudbury area also features a second impact site from a meteor, McDonald noted.
"There are two impact sites side-by-side here in Sudbury," he said. "Lake Wanapitei is an impact structure. That was definitely formed by a meteorite impact, about 38 million years ago, whereas the Sudbury event was about 1.85 billion years ago.
"So they were considerably different in time, but the proximity of one to the other is quite remarkable."
