At https://phys.org/print408280130.html … a new study in Science Reports (March 9th) brings the Younger Dryas Impact Theory back to life after a couple of articles in the journals criticising the analysis of samples (see http://cosmictusk.com for details of the various controversies in the background). The discovery of widespread platinum across continental USA is an interesting development. The opposition will come back with a dampener no doubt, but that is the nature of scientific agreement (I suppose). University of South Carolina archaeologists have provided further evidence to suggest the already well known incidence of the metal exists at Clovis levels at sites in different parts of the States.
… Platinum is also present in a Greenland ice core (of the Younger Dryas period), supplementing the archaeological sites in the image above. It is continental and it may be global.
The Younger Dryas coincides with the end of Clovis culture – and the extinction of 35 species of Ice Age animals (although they were already in decline). The presence of platinum represents atmospheric fall out of rare elements (perhaps as a result of an airburst rather than an impact). See also https://popular-archaeology.com/issue/winter-2017/article/discovery-of-w… … but see also http://cosmictusk.com/comet-research-group-nature-widespread-platinum-yo… … where you can read the full paper (with sources and accredidations).