[meteorite-list] Forest Fire Leads to Discovery of Sudbury Impactite

From: Bob King <nightsky55_at_meteoritecentral.com>
Date: Mon, 16 Jul 2007 09:28:45 -0500
Message-ID: <99c1e91a0707160728s6aeb2ea1k5284a5de5fcbd670_at_mail.gmail.com>

Hi Sterling and list folks,
I work at a newspaper in northern Minnesota and spoke to the geologist Mark
Jirsa about this story before we ran it in our paper. He sent along some
excellent photos not only of the impactites, which looked like grey balls
about one centimeter in diameter, but also of something called tsunamite
which was also related to the Sudbury impact. Apparently the impact caused a
tsunami in a shallow sea that was around this region at the time. The
material was washed up into northern Minnesota in a brecciated jumble of
native rock plus possibly some impactites as well. These tsunamites form
local outcrops. Jirsa plans a trip to the area in early August and again
later that month. I'm going to see if I could come along.
Best to all,
Bob


On 7/15/07, Sterling K. Webb <sterling_k_webb at sbcglobal.net> wrote:
>
> Hi,
>
> Forgive me for being less sensational than the AP.
> This story had been in the news before, so I guess
> the real news is that the AP saw fit to make it a story.
> Always glad to have a meteorite make the news, even
> if it takes almost two billion years to do it.
>
> Sterling K. Webb
> -------------------------------------------------------------------
> http://www.space.com/news/070715_ap_minn_meteorite.html
>
> Forest Fire Leads to Ancient Meteorite Discovery
> By Associated Press -- 15 July 2007; 08:25 pm ET
>
>
> GRAND MARAIS, Minn. (AP) -- A forest fire has led
> to a chance discovery of debris from the impact of a
> meteorite 1.85 billion years ago, more than 450 miles
> away at Sudbury, Ontario.
>
> Geologists had scheduled a field trip in May along the
> Gunflint Trail in northeastern Minnesota, but most areas
> they wanted to explore were closed because of a wildfire
> that charred more than 118 square miles.
>
> Geologist Mark Jirsa of the Minnesota Geological Survey
> went up the trail to scout new locations and, in a spot he
> had never visited before, stumbled across debris now
> linked to the Sudbury impact.
>
> That impact created a crater more than 150 miles across,
> scattering rock and dust over nearly a million square miles.
>
> "It's fairly dark rock,'' Jirsa said. "They look like concrete,
> but in this concrete you would throw pieces of rock of
> all sizes and shapes and in all possible orientations.''
>
> Previously, material thrown out by the impact had been
> found as far from Sudbury as Hibbing, about 125 miles
> farther to the southwest from Grand Marais. However,
> the tiny fragments at Hibbing were found in core samples
> from 800 to 1,000 feet below the surface, while the rock
> layer containing larger chunks at the Gunflint site lies exposed.
>
> "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.''
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Received on Mon 16 Jul 2007 10:28:45 AM PDT