WEST COAST COAL AND POLLEN SHED LIGHT ON GLOBAL CATASTROPHE
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
(GNS), 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 microscopic pollen grains within the coal 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 ground.
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 for 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 rocks in eastern
Marlborough.
" Whether the forest destruction was caused by prolonged darkness and freezing conditions associated with an 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.
ENDS
Contact: Chris Hollis, Paleontologist, GNS, Ph: 04-570-4868 or John Callan, Communications Co-ordinator, GNS, Ph:
04-570-4732 or 025-402-571
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 1100km closer to the
South Pole than it is today, but 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.