Posted: Apr 09, 2017 12:43 am
by Macdoc
Was surprised that there was not a lot on this as it is a hard fought issue

Nice overview from NOVA on impact and other hypothesis.

Nano-diamond presence certainly offset the lower iridium concentration .....the lead researcher was overcome at seeing the nano-diamond presence they found in Greenland. Good science.

and newer material points to impact..

Heavy Metal: Comet-driven megafauna extinction?
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Posted March 13, 2017
Roughly 13,000 years ago, large ice-age mammals known as megafauna — horses, camels, mammoths, mastodons and many others — suddenly disappeared in North America. At the same time, a widespread human culture vanished. Mounting scientific evidence suggests this happened in dramatic fashion by a comet or an asteroid slamming into the Earth.

This cliff profile at Arlington Canyon on Santa Rosa Island shows platinium abundance.

New research by UC Santa Barbara geologist James Kennett and colleagues bolsters the argument for indications of such an event, which ushered in a cool period known as the Younger Dryas.

The team had previously identified, from a thin layer at the Younger Dryas Boundary (YDB) dated to 12,800 years ago, a rich assemblage of high-temperature spherules, melt glass, nanodiamonds and other exotic materials, which can be explained only by cosmic impact. Now they can add platinum to the list.

This is North America centric ...not other areas.