Appalachians with a South American flavor.

The Appalachian mountains of the modern Earth run from Newfoundland along the eastern United States until they disappear in the deep south of Georgia and Alabama. But the present range may represent only a small stretch of a former, glorious incarnation. A team of geologists suggests that pieces of the earlier Appalachians exist in southern South America and perhaps Antarctica -- leftovers from a time 500 million years ago when the three continents may have abutted one another.

Ian W.D. Dalziel of the University of Texas at Austin and his colleagues note that a limestone formation in Argentina has a distinctive form of trilobite typical of ancestral North America rather than South America. The researchers suggest that these two continents collided a half billion years ago and then rifted apart, transferring a sliver of land (arrow) from North to South America. By this theory, the crash created an ancestral Appalachian range that continued into western South America long before the Andes formed. The early mountains may have extended even further, to Antarctica's Shackleton Range, speculate the researchers. They discussed their work at the meeting and in the December GEOLOGY.