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RE: Rodinia Supercontinent
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A lone granite boulder found against all odds high atop a glacier in Antarctica may provide additional key evidence to support a theory that parts of the southernmost continent once were connected to North America hundreds of millions of years ago.
Writing in the July 11 edition of the journal Science, an international team of U.S. and Australian investigators describe their findings, which were made in the Transantarctic Mountains, and their significance to the problem of piecing together what an ancient supercontinent, called Rodinia, looked like. The U.S. investigators were funded by the National Science Foundation (NSF).

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Title: A Positive Test of East AntarcticaLaurentia Juxtaposition Within the Rodinia Supercontinent
Authors: J. W. Goodge, J. D. Vervoort, C. M. Fanning, D. M. Brecke, G. L. Farmer, I. S. Williams, P. M. Myrow, D. J. DePaolo

A glacial boulder in Antarctica, and other data, confirm that East Antarctica and Australia were linked to western North America in a supercontinent 1 billion years ago.

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 favour 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 ~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 uraniun-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.

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