[meteorite-list] Did Dinosaurs Die At Hands of Meteorite Fall or Volcanic Eruption?

[Ron Baalke]

Media Relations Office
The Open University
Milton Keynes, U.K.

MEDIA CONTACT:
Gabi Nobis, Open University Media Relations Officer
01908 655026, g.nobis at open.ac.uk

4 November 2004

PR 4918

DID DINOSAURS DIE AT HANDS OF METEORITE FALL OR VOLCANIC ERUPTION?

An Open University research student will reveal her findings on what caused one 
of the world's 'Big Five' mass extinctions at the Geological Society of 
America's annual meeting in Denver, USA, this month.

PhD student Charlotte Pearce will input into the debate as to whether a 
meteorite impact or volcanic eruption caused the Cretaceous Tertiary Boundary 
(KTB) mass extinction 65-million-years-ago.

Between 50 and 60 per cent of marine and terrestrial life-forms became extinct 
during the KTB extinction, including the dinosaurs.

The cause of this mass extinction has received much attention from scientists 
over the last 25 years, since the detection of iridium-rich cosmic debris at the 
boundary layer around the world -- an element known to be rare on earth. This 
led to the theory that a meteorite impact could have been responsible for the 
debris and the mass extinction; the 180 km wide Chicxulub impact crater was 
eventually discovered in the Gulf of Mexico.

However, on the other side of the world, massive volcanic eruptions, known as 
the Deccan Traps continental flood basalt province, were simultaneously reaching 
their peak, forming a 2.5km thick pile of lava.

"Both the Chicxulub impact and the Deccan eruptions would have had the potential 
to induce detrimental environmental changes serious enough to significantly 
affect terrestrial ecosystems," says Charlotte.

"Dust-induced darkness, acid rain, wild fires and global warming would all have 
played a role in inducing biospheric trauma, but the timescales over which these 
were effective would be expected to be different, dependent on the event that 
caused them," she adds.

Charlotte used chemical and isotopic fingerprinting techniques on molecular 
fossils from North America, and more recently from New Zealand, to investigate 
patterns which would establish whether there was instantaneous change (as the 
result of a meteorite impact) or gradual change within the ecosystem (as caused 
by prolonged volcanism).

"Carbon isotopes can tell us a lot about the stability of an ecosystem and, 
together with the identification of molecular fossils, enables past variations 
in habitat, climate and biology to be investigated.

"The aim of my project is to compare and contrast samples from several 
terrestrial and marine KTB successions, at varying palaeogeographical distances 
from the locations associated with the two putative causes of end-Cretaceous 
environmental stress. In effect the project examines the effects of these two 
environmental disasters working outwards from the 'ground zero' locations," says 
Charlotte.

Results taken from samples in the Western Interior of North America show that 
the ecosystem experienced a short sharp shock at the boundary consistent with a 
meteorite impact. Early analysis of the New Zealand samples also point to a 
meteorite impact.