Some earlier threads have been dedicated to the Younger Dryas and a possible connection to an impacter. Here is the full paper about it. Firestone et al 2007, Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling, PNAS Vol 104, no 41, 9 Oct, pp16016–16021 Firstly I'm interested in the dating ~12,9 ka: That's pretty clear. Open and shut case? Let's have a look here. This picture clearly shows this transition. Consequently: Lücke, A.; Brauer, A. 2004 Biogeochemical and micro-facial fingerprints of ecosystem response to rapid Late Glacial climatic changes in varved sediments of Meerfelder Maar (Germany),Palaeogeography, Palaeoclimatology, Palaeoecology, 211, 1-2, 139-155 p. So what is it? 12,9 ~ 0.1 Ka or 12,690-12,670 counted years BP and what are those relatively warm YD summer temperatures doing there?