Scientists hit pay dirt in drilling of dinosaur-killing impact crater

[Judi Lynn]

Scientists hit pay dirt in drilling of dinosaur-killing impact crater

By Eric HandMay. 3, 2016 , 3:00 AM

Scientists have reached ground zero for one of the world’s most famous cataclysms. Burrowing into the impact structure responsible for the demise of the dinosaurs, a team of researchers has achieved one of its main goals, with rocks brought up from 670 meters beneath the sea floor off the coast of the Yucatán Peninsula in Mexico. These core samples contain bits of the original granite bedrock that was the unlucky target of cosmic wrath 66 million years ago, when a large asteroid struck Earth, blasted open the 180-kilometer-wide Chicxulub crater, and led to the extinction of most life on the planet.

“We’re feeling pretty good,” said co–chief scientist Sean Gulick in an interview from the deck of a drilling platform 30 kilometers offshore in the Gulf of Mexico. “I’m not getting much sleep out here, so we’re little delirious.”

Although scientists have drilled into the buried crater before on land, this is the first offshore effort, and also the first to go after the crater’s “peak ring”—a circular ridge inside the crater rim that’s characteristic of the solar system’s largest impact craters. Astronomers see peak rings on the moon, Mars, and Mercury, but they have never been able to sample one on Earth until now. The team has already been charting the return of life after the worldwide die-off in cores from higher up in the hole. By examining peak ring rocks closely, they hope to test models of crater formation and determine whether the crater itself was one of the first habitats for microbial life after the impact.

The peak ring formed in a matter of minutes. Just after the impact, deep granite bedrock, flowing like a liquid, rebounded into a central tower as tall as 10 kilometers before collapsing into the circular ridge. Next, the peak ring was covered by a layer of jumbled-up rocks, called a breccia, that contains chunks of blasted-up rock and impact melt. Then, in the hours that followed, ocean tsunamis dumped huge amounts of sandy sediment in the giant hole in Earth. Further deposition would come slowly, as life returned to the seas, and layers of limestone were built up in the ensuing millions of years.

More:
http://www.sciencemag.org/news/2016/05/scientists-hit-pay-dirt-drilling-dinosaur-killing-impact-crater

[Ghost Dog]

1. Nice description

Just after the impact, deep granite bedrock, flowing like a liquid, rebounded into a central tower as tall as 10 kilometers before collapsing into the circular ridge. Next, the peak ring was covered by a layer of jumbled-up rocks, called a breccia, that contains chunks of blasted-up rock and impact melt. Then, in the hours that followed, ocean tsunamis dumped huge amounts of sandy sediment in the giant hole in Earth.

[Wounded Bear]

2. K & R ...... nt