SWEAT (hypothesis)

Evidence

A paper published by an international team of U.S. and Australian investigators led by John Goodge gives significant support to the theory. The team's findings were made in the Transantarctic Mountains and provide physical evidence that confirms the SWEAT hypothesis.

The team was searching in Antarctica's Transantarctic Mountains for rocks carried along by ice rivers that could provide clues to the composition of the underlying crust of Antarctica, which in most places is buried under approximately 2 mi of ice. One rock, found atop Nimrod Glacier, was later determined to be a very specific form of granite which has a particular type of coarse-grained texture (called rapakivi texture.) Chemical tests run on the rock revealed that it has a radiometric age and stable isotope ratios closely matching those of a distinctive belt of rapakivi granite in North America that stretches from California through New Mexico to Kansas, Illinois in the United States, and eventually New Brunswick and Newfoundland in Canada. This belt of rock was a part of Laurentia, thought by some geologists to be the core of Rodinia. This belt stops suddenly at its western margin, leading geologists to suspect that some piece of crust had rifted away from what is now the West Coast of the United States.

East Antarctica–Laurentia juxtaposition

The positions of Laurentia and other landmasses in the Precambrian supercontinent of Rodinia are controversial. Although geological and isotopic data support an East Antarctic fit with western Laurentia, alternative reconstructions favor the juxtaposition of Australia, Siberia, or South China. New geologic, age, and isotopic data provide a positive test of the juxtaposition with East Antarctica: Neodymium isotopes of Neoproterozoic rift-margin strata are similar; hafnium isotopes of about 1.4 billion year old Antarctic-margin detrital zircons match those in Laurentian granites of similar age; and a glacial clast of A-type granite has a uranium-lead zircon age of 1440 million years, an epsilon-hafnium initial value of +7, and an epsilon-neodymium initial value of +4. These tracers indicate the presence of granites in East Antarctica having the same age, geochemical properties, and isotopic signatures as the distinctive granites in Laurentia.

References

References

1. Hill, Josh Hill. (July 18, 2008). "Were Antarctica and North America Once Connected? A Single Boulder Says "Yes"". The Daily Galaxy.
2. (July 17, 2008). "A Single Boulder May Prove that Antarctica and North America Were Once Connected". [[National Science Foundation]].
3. (2009). "Global tectonics.". Wiley-Blackwell.
4. Thompson, Andrea. (July 28, 2008). "Senior Writer". LiveScience.com.
5. (2008). "A Positive Test of East Antarctica–Laurentia Juxtaposition Within the Rodinia Supercontinent". [[Science (journal).