KEY POINTS:
New Zealand is a remnant of a gigantic high plateau that collapsed as the Earth tore apart.
The rest of the plateau's remains make up one of the longest mountain chains in the world, Antarctica's Trans-Antarctic mountains, says geophysicist Michael Studinger of the Lamont-Doherty Earth Observatory at Columbia University.
Dr Studinger and his colleagues reported yesterday in the August issue of the journal Geology that the mountain range is the remnant edge of a gigantic plateau the size of France that was roughly 3km high.
The mountains run up out of the Ross Sea, immediately south of New Zealand, along the western edge of the Ross Ice Shelf, and nearly 4000km across the frozen continent to divide east and west Antarctica.
Most of the world's highest mountain ranges typically formed when massive tectonic plates crashed together, but scientists have agreed for years that the Trans-Antarctic belt apparently emerged as the Earth's crust rifted apart.
Dr Studinger said his research suggested that the original plateau collapsed like a failed souffle when its interior became too hot, leaving only the cooler and stiffer outer edges.
As the Earth's crust began pulling apart 105 million years ago, the collapsed part of the plateau sank, leaving one shoulder curving along the rim of a great plain.
"We think the other shoulder is simply no longer there," Dr Studinger said. "Antarctica was part of [the super-continent] Gondwanaland, and when it broke away during the Mesozoic [era], we think this rift shoulder simply disappeared and is part of what is now New Zealand."
But a GNS Science geologist, Stephen Bannister, said the researchers' conclusions were "controversial".
"Their described model struggles to provide an explanation for the current high elevation of the Trans-Antarctic Mountains," he said. Some are more than 4500m high.
"And there is a lack of data on the matching 'eastern shoulder' of the extension area," he said. "Their inferences will certainly not be immediately accepted by others in the field, without a lot more discussion".
Dr Bannister said the theory was of particular interest to NZ geologists and geophysicists, because of implications not only for the wider field of NZ geology, but especially for petroleum geology and the evolution of flora/fauna.
"This is because NZ was right next to the Ross Sea during Cretaceous times," he said. "Much of the primary architecture of the sedimentary basins around NZ formed at this time, with petroleum source rocks within them.
"Understanding the depositional environment and distribution of different sediment types of this age around NZ is a key part of any petroleum exploration strategy offshore from NZ."
- NZPA
