Millions of years ago, the American Southwest sat next to East Antarctica
What a juxtaposition: About 800 million years ago, East
Antarctica, now one of the coldest regions on Earth, abutted what is now
Both locales were part of an equatorial supercontinent
called Rodinia, says John Goodge, a geologist at the
The motion of tectonic plates continually rearranges Earth’s continents, sometimes cramming most or all of them into immense groupings called supercontinents.
One of those assemblages, Rodinia, existed between 750 million and 800 million years ago. Debate has long raged about how today’s landmasses were arranged then, says Goodge. The orientation of magnetic lines locked into rocks that formed at the time — which often can be used to estimate the location and orientation of ancient landmasses — are in many cases contradictory, he notes.
In previous studies, various teams have argued that
Now, geochemical analyses of rock samples taken from the
Transantarctic Mountains hint instead that portions of East Antarctica occupied
that spot, Goodge and his colleagues report in the July 11 Science. For one thing, the ratios of neodymium isotopes in the
ancient sediments in the
Finally, the researchers note, the ratios of various
isotopes and elements in a basketball-sized chunk of granite found in
Goodge, J.W., et al. 2008. A positive test of east Antarctica-Laurentia juxtaposition within the Rodinia cupercontinent. Science 321(Jul. 11):235.