Ancient Granite Links Antarctica to North America
Minnesota Connection: Antarctica's Granite Clue
A lone granite rock found atop a glacier in Antarctica may provide important additional evidence to support the theory that, hundreds of millions of years ago, parts of Antarctica were connected with North America.
A team of U.S. and Australian researchers made this discovery in the Transantarctic Mountains. This finding helps scientists better understand the ancient supercontinent known as Rodinia.
The Rodinia Connection
Previous scientific evidence led researchers to theorize that approximately 600 to 800 million years ago, a portion of Rodinia broke away from what is now the southwestern United States and migrated southward to become eastern Antarctica and Australia. The new finding provides physical evidence that confirms this well-known scenario regarding the Southwest United States and East Antarctica.
Discovery by Chance
The discovery of the rock was made by chance while investigators were collecting debris carried through the Transantarctic Mountains by flowing rivers of ice—moving at a literal glacial pace—in East Antarctica.
John Goodge (University of Minnesota-Duluth) and his team were searching for rocks that might provide clues to the composition of the Antarctic continental crust, which is buried under a layer of ice two miles thick in most places.
Analyzing the Granite
While working with clumps of rocks and glacial mud, the team identified a specific rock, small enough to be lifted with one hand, found on the Nimrod Glacier. It was later determined to be a very specific form of granite.
Chemical analysis and isotopic tests conducted in United States laboratories revealed that the rock has a chemical composition very similar to a unique belt of igneous rocks in North America. This belt runs through:
- California
- New Mexico
- Kansas
- Illinois
- New Brunswick and Newfoundland, Canada
We now know that this belt of rocks formed part of what is called Laurentia, a component of the supercontinent Rodinia.