Browsing Radiocarbon, Volume 53, Number 2 (2011) by Authors
Evidence for a Solar Flare Cause of the Pleistocene Mass ExtinctionLaViolette, Paul A. (Department of Geosciences, The University of Arizona, 2011-01-01)The hypothesis is presented that an abrupt rise in atmospheric radiocarbon concentration evident in the Cariaco Basin varve record at 12,837 +/- 10 cal yr BP, contemporaneous with the Rancholabrean termination, may have been produced by a super-sized solar proton event (SPE) having a fluence of ~1.3 x 1011 protons/cm2. A SPE of this magnitude would have been large enough to deliver a lethal radiation dose of at least 3-6 Sv to the Earth's surface, and hence could have been a principal cause of the final termination of the Pleistocene megafauna and several genera of smaller mammals and birds. The event time-correlates with a large-magnitude acidity spike found at 1708.65 m in the GISP2 Greenland ice record, which is associated with high NO-3 ion concentrations and a rapid rise in 10Be deposition rate, all of which are indicators of a sudden cosmic-ray influx. The depletion of nitrate ions within this acidic ice layer suggests that the snowpack surface at that time was exposed to intense UV for a prolonged period, which is consistent with a temporary destruction of the polar ozone layer by solar cosmic rays. The acidity event also coincides with a large-magnitude, abrupt climatic excursion and is associated with elevated ammonium ion concentrations, an indicator of global fires.