From the Radiocarbon Article:

CONCLUSION
Spurts of 14C production evident in the Cariaco Basin varve record spaced at 22-yr solar cycle intervals
likely record times of super-sized solar proton events (SPEs), some of which may have been
intense enough to overpower and penetrate the magnetosphere. The largest of these 14C spurts,
which dates at 12,837 ± 10 yr BP in the Cariaco Basin record, is shown to correlate in time with a
prominent short-duration acidity spike found in the Summit, Greenland ice-core record, which is
positioned in the midst of prominent nitrate ion concentration maxima indicative of substantial
atmospheric ionization by cosmic rays. Extrapolations based on the 14C data suggest that the 12,837
cal yr BP SPE had about 125 times the fluence of the February 1956 SPE and was strong enough to
deliver a ground-level radiation dose exceeding 3 Sv over a 2-day period. Radiation doses in excess
of 6 Sv are projected if the associated solar storm main phase decrease had induced a collapse of the
magnetosphere. This super SPE is proposed to have been the cause of the final disappearance of the
Pleistocene megafauna. A super SPE occurring around 12,819 yr BP may have also contributed to
the megafaunal demise. Smaller mammals and birds unprotected from the particle radiation would
also have been at risk. Elevated levels of UV radiation resulting from destruction of the ozone layer
would have posed an additional hazard. Cosmic dust from the circumterrestrial dust sheath injected
into the stratosphere at the time of super SPE impact could account for the sporadic reports of ET
indicators in early YD sediments and Greenland ice.
A definitive test of the solar super SPE hypothesis could be made by analyzing Greenland ice in the
vicinity of the 1708.65-m acidity spike to determine whether a large increase in 10Be concentration
occurred at that time. Additional analysis of platinum group elements in this portion of the ice core
could check whether the proposed SPE may have been sufficiently strong to cause a collapse of the
circumterrestrial dust sheath.