Younger Dryas “black mats” and the Rancholabrean termination in North America

Abstract

Of the 97 geoarchaeological sites of this study that bridge the Pleistocene-Holocene transition (last deglaciation), approximately two thirds have a black organic-rich layer or ''black mat'' in the form of mollic paleosols, aquolls, diatomites, or algal mats with radiocarbon ages suggesting they are stratigraphic manifestations of the Younger Dryas cooling episode 10,900 B.P. to 9,800 B.P. (radiocarbon years). This layer or mat covers the Clovis-age landscape or surface on which the last remnants of the terminal Pleistocene megafauna are recorded. Stratigraphically and chronologically the extinction appears to have been catastrophic, seemingly too sudden and extensive for either human predation or climate change to have been the primary cause. This sudden Rancholabrean termination at 10,900 ؎ 50 B.P. appears to have coincided with the sudden climatic switch from Allerød warming to Younger Dryas cooling. Recent evidence for extraterrestrial impact, although not yet compelling, needs further testing because a remarkable major perturbation occurred at 10,900 B.P. that needs to be explained.climate change ͉ extinction ͉ radio carbon ͉ stratigraphy ͉ archeology

Paleoindian demography and the extraterrestrial impact hypothesis

“…The results of our analysis are consistent with recent comments by Pinter and Ishman (13) and Haynes (14). Pinter propose between the ET impact and the extinction of the megafauna.…”

“…The dates span the period 13,000 to 8,000 14 C BP. Twenty-three of these dates were obtained from Hamilton and Buchanan (11) and Waters and Stafford (12).…”

Synchronous extinction of North America's Pleistocene mammals

“…Our results leave open the possibility for a small level of background extinctions (0-8 genera) followed by a surge in extinction rates that wiped out the remaining taxa (23-31 genera) between 12,000 and 10,000 radiocarbon years B.P. Whether or not background extinctions took place, that a catastrophic event or process occurred at the end of the Pleistocene is abundantly clear (23).…”

Charcoal in soils of the Allerød-Younger Dryas transition were the result of natural fires and not necessarily the effect of an extra-terrestrial impact

“…The supposed extraterrestrial impact should have triggered Younger Dryas cooling and megafaunal extinctions. Haynes (2008) interpreted 'black mats' of mollic paleosols, aquolla, diatomites or algae radiocarbon dated to the Allerød-Younger Dryas transition as 'stratigraphic manifestations' of the cooler Younger Dryas climate which resulted from a rise in local water tables caused by more effective recharge. He also questioned the evidence presented by Firestone et al (2007) for an extraterrestrial impact, noting that the microspherules and micrometeorites they cite are components of cosmic dust that constantly fall to earth making an 'impact' difficult to distinguish on this basis alone.…”