[meteorite-list] Large Asteroid Impact 200 Million Years Ago May Have Helped Dinosaurs Dominate The Earth

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sun Oct 8 21:08:09 2006
Message-ID: <200610090108.SAA03114_at_zagami.jpl.nasa.gov>

http://www.timesonline.co.uk/article/0,,2087-2394026,00.html

T Rex was born in the Irish Sea, say scientists
Roger Dobson
The Sunday Times (United Kingdom)
October 8, 2006

A HUGE meteorite that hit the Irish Sea and left a crater the size of
Surrey may have helped giant dinosaurs come to dominate the planet,
scientists have claimed.

The researchers, who have analysed rock formations in the British Isles
and France, believe the impact caused a tsunami that swamped large parts
of Europe.

They argue the meteor strike 200m years ago and others like it may have
led to changes in the Earth's climate that caused some species to die
out and others to dominate.

It has long been argued that the extinction of the dinosaurs 65m years
ago was caused by a massive asteroid strike.

But scientists have wondered why dinosaurs, which had previously been
relatively puny, began to develop into giants such as Tyrannosaurus rex
about 200m years ago.

One theory is that increases in carbon dioxide in the atmosphere led to
bigger plants, which encouraged the development of bigger herbivores and
then a growth in the size of predators.

Other scientists claim an impact by a meteor may account for the
relative suddenness of the change.

"There was a relatively sudden increase in the size of dinosaurs around
the time we have dated this impact," said Michael Simms, curator of
paleontology at the Ulster Museum in Belfast who led the research. "This
impact may well have been a factor in the changes that were going on."

Simms' team found evidence of the shock probably caused by a meteorite,
which may have been up to two miles wide and hit at 18,000mph, in data
from boreholes and rock formations covering 100,000 square miles.

They have not found the crater itself, but they believe the meteor may
have hit what is now St George's Channel, between Pembrokeshire and the
Irish coast. Much of western Britain and Ireland was under water at the
time.

The crater may have been more than 30 miles wide but would now be deeply
buried beneath the sea floor.

In the research, published in an academic journal, Simms looked for
signs of impact rippling out from the crater in sediment that would have
been affected by the shockwave. He analysed rock and borehole data and
found the same unique pattern at every site he looked at, from Northern
Ireland to Yorkshire and Dorset.

Paul Barrett, a paleontologist at the Natural History Museum in London,
said Simms' theory was "an interesting idea".

"This is the first geological suggestion that there was an impact at
this time. What we really want to back this up is a crater of the right
age."
Received on Sun 08 Oct 2006 09:08:06 PM PDT