Manuscrito
Northwestern Chilean Patagonia sediment record supports YDB cosmic impact triggering of biomass burning, climate change, and megafaunal extinctions (~12.8 ka)
Fecha
2015Institución
Resumen
Younger Dryas (YD) impact theory posits that fragments of a disintegrating giant comet
struck North America, South America, Europe, and western Asia ~12,800 years ago.
These airbursts/impacts produced the YD boundary layer (YDB), containing anomalously
high concentrations of platinum, high-temperature spherules, meltglass, and
nanodiamonds, providing an isochronous datum at 50 sites across ~50 million km² of
Earth. This event triggered extensive biomass burning, “impact winter,” the YD climatic
episode, and extinction of millions of late Pleistocene megafauna. In the first extensive
investigation south of the equator, we report a 12,800-year-old stratum at Pilauco in
northwestern Chilean Patagonia (~40° S), exhibiting peak abundances in impact-related
platinum, palladium, gold, high-temperature Fe-rich and Cr-rich impact spherules, and
native iron grains rarely found on Earth. Furthermore, a major peak in charcoal marks
an intense biomass-burning episode, synchronous with a dramatic decrease in seeds
and shift in vegetation, reflecting abrupt climatic warming at the YD onset, anti-phased
with cooling over the Northern Hemisphere. The sudden disappearance of megafaunal
bones and dung fungi (Sporormiella) at Pilauco is synchronous with megafaunal
extinction over the Americas. The Pilauco evidence is consistent with the occurrence of
local cosmic impacts, coeval with other 12,800-year-old YDB cosmic impacts on four
continents.