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It is a landscape of cliff exposures ~100 m high of the Los Colorados Formation (reddish layers of sedimentary rocks) of Norian age overlying toward the base more mauve-colored sedimentary beds of the Ischigualasto Formation of Carnian age. Photo was taken near the Quebrada de la Sal in the Ischigualasto Provincial Park of San Juan Province, Argentina. The Ischigualasto Formation contains the earliest documented dinosaurs and along with the Los Colorados Formation, which also contains a rich dinosaur fauna, may be representative of a southern hemisphere refugia from which dinosaurs dispersed in the Late Triassic.

The Ischigualasto formation in Argentina's Ischigualasto Provincial Park contains the earliest documented dinosaurs.

PHOTOGRAPH BY DENNIS KENT

Dan Vergano

National Geographic

Published May 20, 2014

A huge desert created by global warming likely prevented early dinosaurs from migrating out of South America for millions of years, suggests an analysis of ancient rocks. (Related: "Oldest Dinosaur Found?")

In Brief

At that time, during the Triassic period, the world's continents were bound together in a supercontinent called Pangaea, home to the first dinosaurs. But as dinosaurs spread, they didn't become evenly distributed across this landmass, suggests a team led by Columbia University geophysicist Dennis Kent. (Related "Supercontinent Pangaea Pushed Into Place.")

In a Proceedings of the National Academy of Sciences report Kent and colleagues note that there's an extraordinarily long time between when dinosaur fossils begin showing up in rocks in what is now South America, dated to 231 million years ago, and when they begin showing up in rocks in North America, dated to 218 million to 212 million years ago.

"Dinosaurs seemed to have been corralled for a long time down there, even with no obvious mountains or seaways to stop them from dispersing north over the Americas," Kent says.

Most likely, he says, there was "a vast, hyperarid Sahara-like desert across Pangea" that blocked the dinosaurs from heading north.

High levels of carbon dioxide, a greenhouse gas, had melted the Poles and led to global warming during the Triassic, the study notes. The resulting desert eventually shrank as the climate cooled heading into the Jurassic period, allowing dinosaurs to spread across the world.

Follow Dan Vergano on Twitter.

5 comments
Ray Del Colle
Ray Del Colle

"Carbon dioxide has increased about 40 percent in the atmosphere since the 1750s, due to pollution from dirty energy like coal, oil, and gas. The result is a warming climate." http://clmtr.lt/c/Hvw0cd0cMJ

Marcos Toledo
Marcos Toledo

This bring up a question of what will happen to countries in arid regions today as global warming continues.

George Pierce
George Pierce

Looks like global warming was started before humans.

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