KEY POINTS:
University of Canterbury research indicating a glacial ridge in the South Island was formed by a landslide could pour cold water on evidence that climate change happened simultaneously around the world.
Professor Jamie Shulmeister, who worked on the research with Associate Professor Tim Davies and honours student Daniel Tovar, said the discovery was made as a result of a study of the Waiho Loop glacial moraine.
Professor Shulmeister said there had been huge scientific debate on the climatic implications of the Waiho Loop.
Located 100m above the plains on the foreland of the Franz Josef Glacier in South Westland, between the township and the sea, the glacial moraine had been the focus of much international research.
The Waiho Loop moraine was widely used as evidence for direct inter-hemispheric linkage in climate change.
"But these new findings suggest the loop - which sits near the South Island's Alpine fault line - was the result of a landslide, not climate change."
Professor Shulmeister said a moraine was a ridge that marked the end of an earlier glacier limit.
Scientists had believed the Waiho Loop moraine was created during a brief cold snap about 13,000 years ago that also affected Europe and North America.
The sudden climatic event had inspired the Hollywood blockbuster movie The Day After Tomorrow, he said. But no one had ever studied the Waiho Loop sediments.
"When graduate student Dan Tovar had a look, he discovered to our surprise that it was mainly made up of a rock type known as greywacke, which is different from the rocks that make up all the other moraines in front of the Franz Josef Glacier."
Professor Shulmeister said greywacke occurred about 13km up the valley from the Loop.
All the other moraines were predominantly composed of schist which outcropped near Franz Josef township.
"The greywacke was also rather more angular than the rocks in the other moraines, suggesting it had not been transported in water or at the base of a glacier."
As a result of the study, Professor Shulmeister's team believes a large landslide dumped a huge volume of rock on top of the glacier, causing it to advance and, when the advance stopped, the moraine was created.
Professor Shulmeister said the findings, to be published this week in the international science journal Nature Geoscience, were like "throwing a cat among the palaeoclimate pigeons".
