Monday, March 28, 2011

Canada-US border 120 million years old

Geological record surprisingly mirrors today's Canada-U.S. border
Postmedia News: Two scientists probing the ancient foundations of the Rocky Mountains have discovered -- to their great surprise -- that today's Canada-U.S. border also marked a clear geological dividing line during a key phase of the continent's formation more than 100 million years ago.

'The modern political boundary between the United States and Canada originated roughly 200 years ago,' states the summary of a study co-authored by geologists Andrew Leier of the University of Calgary and George Gehreis of the University of Arizona. 'However, it appears that even as much as 120 million years ago, rivers and sediments in the two regions developed their own distinct characteristics.'...

'Sand grains made of the mineral zircon show that Cretaceous sediment in the United States has a clear 'American' signature, whereas that in the Canadian Rockies has a different and definable 'Canadian' signature.' observed the researchers, whose study is published in the journal Geology...

The tiny zircons used to profile strands of sandstone on either side of the border not only showed that the rocks are different in each country, Leier added. 'Rivers were flowing out of these Cretaceous mountains, from west to east,' he noted. 'The second implication of the data is that the rivers that flowed from the mountains in the United States stayed in the U.S., and those in Canada stayed in Canada... 'There is no evidence that rivers were crossing what is today the border.'
Image source here.