[meteorite-list] Ancient Sudbury Meteorite Blasted Debris Into Michigan

From: drtanuki <drtanuki_at_meteoritecentral.com>
Date: Thu, 30 Aug 2007 11:40:28 -0700 (PDT)
Message-ID: <508500.15773.qm_at_web53203.mail.re2.yahoo.com>

Dear List Members,
  Here is an abstract of an additional recent paper by
the same investigator published on the Sudbury impact.
  The abstract mentions tektites were found.

http://www.eurekalert.org/pub_releases/2007-08/gsoa-sga082807.php

Physical and chemical evidence of the 1850 Ma Sudbury
impact event in the Baraga Group, Michigan
Peir K. Pufahl, Acadia University, Earth and
Environmental Science, Wolfville, Nova Scotia B4P 2R6,
Canada; et al. Pages 827-830.

A catastrophic extraterrestrial impact 1850 million
years ago produced the Sudbury crater, the second
largest known impact site on Earth. Pufahl et al.?s
discovery of debris in northern Michigan, USA,
produced from this impact has provided new information
regarding the nature of this event. A prominent
iridium anomaly in impact-generated tsunami deposits
containing shocked quartz, spherules, tektites, and
accretionary lapilli demonstrate that the
extraterrestrial body was a meteorite and not a comet,
as previously proposed. The Sudbury event was larger
than those responsible for later major extinction
events, and may prove important in the evolution of
early life on Earth.

Best Regards, Dirk Ross...Tokyo


--- Ron Baalke <baalke at zagami.jpl.nasa.gov> wrote:

>
>
http://www.amherstdaily.com/index.cfm?sid=58282&sc=58
>
> Ancient Sudbury meteorite blasted debris into
> Michigan
> MARGARET MUNRO
> CanWest News Service
> August 29, 2007
>
> A mountain-sized meteorite appears to have created
> Sudbury's gigantic
> crater and sent a tsunami racing though ancient
> oceans, say scientists
> who have uncovered a thick layer of debris the
> extraterrestrial
> interloper hurled all the way into Michigan.
>
> A Canadian-U.S. team says the
> two-to-four-metre-thick layer of "ejecta,"
> which they found south of Lake Superior, bears the
> clear signature of a
> meteorite.
>
> Perhaps even more intriguing, they say the "ejecta"
> appears to have been
> stirred up by a "mega-tsunami," possibly two, that
> swept through the
> ancient oceans after the space rock hit.
>
> "The material blown out of the crater was reworked
> during deposition by
> a tsunami," says Peir Pufahl, lead author of a
> report on the find in the
> September editions of the journal Geology. He says
> shock waves generated
> by the impact of the meteorite, believed to have
> been about the size of
> Mt. Everest, would have been powerful enough to
> generate giant waves in
> near-by oceans.
>
> "We also get beautiful rock preserved in tear drops
> just as you'd expect
> if you had molten rock flying through the atmosphere
> and it cooled,"
> Pufahl said in a interview.
>
> The Sudbury crater, the second largest ever found,
> was formed 1.85
> billion years ago and is much bigger than the one
> linked to the demise
> of the dinosaurs.
>
> Some have suggested a comet carved out the crater,
> which originally
> measured up to 280 kilometres in diameter. But the
> material uncovered in
> northern Michigan points to a meteorite, since it
> contains an unusually
> high concentration of iridium, which occurs in low
> amounts in icy comets
> but in high levels in space rocks.
>
> The "ejecta layer," which the geologists found
> buried a kilometre
> underground south of Lake Superior, builds on
> similar evidence uncovered
> near Thunder Bay, Ont., a few years ago. The newly
> found material not
> only contains high levels of iridium and "melt
> drops" but also "shocked"
> crystals deformed by the intense energy, and
> evidence of reworking by a
> tsunami, the team reports.
>
> The impact of the meteorite would have been felt
> globally but most of
> the evidence has eroded away over time. "It's like a
> book with 90 per
> cent of pages missing," says Pufahl.
>
> He says the huge cloud of gas and molten rock hurled
> into the atmosphere
> would have put photosynthesis on hold for an
> extended period and may be
> linked to a "long lull" in the evolution of early
> life.
>
> Computer models have estimated the space rock could
> have been close to
> 20 kilometres across and travelling 20 kilometres a
> second, or 1,200
> kilometres a minute, when it slammed into Earth.
>
> "That energy has to go somewhere," says Pufahl.
> "Some of it goes into
> deforming the rock it slams into, some of it
> obliterates the rock it
> slams into and throws it in to the atmosphere, and
> some of it is
> transmitted away from the impact as shock waves. It
> is those shocks
> waves that would impact on water to cause tsunamis."
>
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Received on Thu 30 Aug 2007 02:40:28 PM PDT