New evidence indicates comet impacts triggered extinctions in North America 12,900 yrs ago

Washington, July 22 (ANI): Researchers have found rare diamonds buried on an island near southern California, which strengthens the controversial idea that comet impacts wiped out huge beasts and an early human culture in North America about 12,900 years ago.

Similar "nanodiamonds" found in sediments across North America were presented earlier this year as proof that space rocks colliding with Earth led to the ancient mass extinction. ccording to the theory, a barrage of comet debris rained down on North America during the last ice age and sparked massive wildfires.

That initial heat and pressure formed tiny diamonds in the soil.

But, the heat also abruptly melted ice sheets, causing an influx of freshwater that shut down a key ocean current and reversed the region's thaw.

The sudden recooling killed off mammals such as saber-toothed cats, dire wolves, and mammoths and wiped out some of North America's earliest known human inhabitants, the Clovis culture.

Opponents of the theory have been skeptical of the evidence, saying that the previously found microscopic diamonds lacked crystalline structures associated with the "shock" of being struck by extraterrestrial objects.

According to a report in National Geographic News, the newfound diamonds, however, have a unique hexagonal structure that's only been found on Earth in places where known impacts have occurred.

"Therefore (the diamonds') discovery is important for this hypothesis, because it is hard to explain these away," said study co-author James Kennett, an emeritus geologist at the University of California, Santa Barbara.

The hexagonal diamonds were found in ancient sediment layers on California's Santa Rosa Island, mixed in with other types of nanodiamonds and large amounts of charcoal from wildfires.

"There was basically an inferno as far as we're concerned at this location at this time on this island," Kennett said.

Also, around the same time that large mammals vanished from the mainland, the island's fossil record suggests that pygmy mammoths disappeared and vegetation shifted to grasslands and oak trees.

All the evidence, Kennett said, points to sudden climate change caused by "some sort of cosmic impact." (ANI)