Younger Dryas Impact Hypothesis Confirmation Work

09-01-2014 • arclein

Firestone et al. (1) (hereafter Firestone et al.) proposed that a cosmic impact event occurred at the onset of the Younger Dryas (YD) cooling episode at about 12,900 calendar years Before Present (12.9 ka B.P.). Evidence cited to support their hypothesis includes elevated levels of iron- and silica-rich magnetic spherules, magnetic grains, iridium, and other materials such as nanodiamonds and high temperature melt glass, in association with proxies indicative of biomass burning (1⇓⇓⇓?5). Also reported were charcoal, carbon spherules, aciniform soot, and glass-like carbon. The group further proposed that the impact event may have contributed to the YD cooling episode, the near-contemporaneous extinction of approximately 36 species of megafauna, and triggered significant population declines among some surviving species including human regional populations. The absence of one or more associated impact