[meteorite-list] New Zealand Coal and Pollen Shed Light On Global Catastrophe

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:47:13 2004
Message-ID: <200111230757.XAA08409_at_zagami.jpl.nasa.gov>

Institute of Geological & Nuclear Sciences
Lower Hutt, New Zealand

Institute of Geological & Nuclear Sciences
Phone: (04) 570 1444
Fax: (04) 570 4600



A New Zealand-led group of scientists has found the first evidence for
global destruction of forests when a large asteroid hit the Earth 65
million years ago, killing off the dinosaurs.

Until now scientists believed that destruction of forests due to an
"impact winter" or impact-ignited wildfires was largely confined to the
American continent, within a radius of several thousand kilometres of
the inferred impact site on the Yucatan Peninsula, Mexico.

The New Zealand finding of a sudden death of a mixed forest and rapid
recolonisation by ferns, on the opposite side of the Earth to the
impact site, is compelling evidence that the asteroid impact caused
sudden destruction of terrestrial plants worldwide.

The study by paleontologists Chris Hollis and Ian Raine of the
Institute of Geological and Nuclear Sciences Limited, and Swedish
researcher Vivi Vadja, is published in the latest issue of the
international magazine Science.

The trio focused on pollen grains preserved in exposed coal seams in a
stream bank adjacent to the Moody Creek coal mine, north of Greymouth.

GNS scientists have a good knowledge of the Greymouth coalfield having
mapped it in detail over many years.

Working on a hunch that the coal might contain the evidence they were
looking for, Dr Raine chipped off pieces of the coal seam and brought
them to Wellington where the microscopic pollen grains were studied.

The scientists found a mixed forest community had been abruptly
replaced by a few species of fern directly after the meteorite impact.
The types of fern identified are known as early colonisers of open

Geochemical analysis of the coal showed extremely high concentrations
of the elements iridium, cobalt, and chromium. The iridium
concentration of 71 parts per billion is the highest known from
non-marine rocks anywhere in the world.

These three elements are known to be much more abundant in meteorites
than in the Earth's crust. They have been found at high concentrations
before in New Zealand, but only where the impact layer is preserved in
marine sedimentary rocks in eastern Marlborough.

"Whether the forest destruction was caused by prolonged darkness and
freezing conditions associated with the impact winter, or by global
outbreaks of wildfires, is a matter for further study by the research
team," Dr Hollis said.

"Either way, however, it is no longer difficult to explain the mass
extinction of large herbivorous dinosaurs and their predatory cousins,
especially in the southern hemisphere."

The research was supported by the New Zealand Marsden Fund, and the
Swedish Wenner-Gren Foundation and Royal Physiographic Society.


Note: Sixty-five million years ago there were at least four types of
dinosaur living in New Zealand. They included a sauropod, theropod,
hypsilophodont, and ankylosaurid. There were also numerous marine
reptiles. Bones of these creatures have been found in a stream north
of Napier. Sixty-five million years ago New Zealand was about 1000km
closer to the South Pole than it is today, and several degrees warmer
than today. The Hawke's Bay stream where the remains of New Zealand's
dinosaurs have been found is one of four sites in the southern
hemisphere where the so-called "polar dinosaurs" have been found. The
other locations are in Australia, the Beardmore Glacier Antarctica,
and the Antarctic Peninsula.
Received on Fri 23 Nov 2001 02:57:08 AM PST

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