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Mississippi River
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Before the Mississippi: Ancient Rivers Flowed West

Like vacationers taking a pit stop on a long road trip, zircon mineral grains from the northern Appalachians may have stopped off in Michigan before ending up on the Colorado Plateau, a new study suggests. The finding, reported in the June Geology, is a major boost to the notion that a continent-spanning, Amazon-like river system once carried sediments west across North America.
A large proportion of the zircons found in Jurassic-era sandstones throughout a Texas-sized portion of the Colorado Plateau originated in the Appalachians (SN: 8/30/03, p. 131), previous analyses have shown. Those erosion-resistant mineral grains were carried westward by an immense river, deposited on floodplains and then stirred back up innumerable times before ending up in massive dune fields that later solidified into western sandstones, says William R. Dickinson, a geologist at the University of Arizona in Tucson.

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