fourth-extinction_main FROM THE FIELD
The Fourth Extinction

Photo Essay: Unearthing the Lost World Below a Petrified Forest

by |April 29, 2014

In Arizona’s Petrified Forest National Park, researchers are scouring the fossil-rich surface and drilling deep into ancient rocks to learn more about what happened during the late Triassic, some 201 million to 235 million years ago. It was a time when the world underwent repeated climate shifts and catastrophic mass extinctions, and both early dinosaurs and mammals evolved. What the researchers learn here may not only allow them to write a precise chronology of the period, but shed light on wider questions including how climate swings work, and how they affect ecosystems. READ THE FULL SCIENTIFIC STORY or SEE A VIDEO

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One goal in the coring project is exact dating of the wavy band of rock about three feet below Olsen, a few inches thick, marking the break between reddish rocks above and whitish ones below. Composed of tangled, cylindrical strands that could be tree roots or other debris, he thinks it may be the remains of a sudden mass extinction. It could line up with a well-dated giant meteorite that hit what is now southern Canada 215.5 million years ago—but only data provided by the core will tell. Olsen and others also intend to inspect this layer for other signs of a connection, including microscopic diamonds created on impact, and the rare element iridium, carried by asteroids. If his idea proves correct, it would represent the only known biological prelude to an even larger impact believed to have wiped out the dinosaurs 149 million years later.

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