Evidence for a Solar Cause of the Pleistocene Mass Extinction

Paul A. LaViolette October 29, 2009, submitted for publication

Abstract An abrupt rise in atmospheric radiocarbon concentration evident in the Cariaco Basin varve record at 12,887±10 cal yrs b2k contemporaneous with the Rancholabrean termination, may have been produced by a super-sized solar proton event (SPE) having a fluence of 1.3 - 1.6 X 10^19 protons/cm2. The SPE, which was large enough to overpower the magnetopause sheath and deliver a lethal radiation dose of over 4 Sv to the Earth's surface, was likely the climactic event terminating the Pleistocene megafauna. It is registered in the GISP2 Greenland ice core record with a large magnitude acidity spike, flanked by high NO-3 ion concentrations, and accompanied by an abrupt rise in 10Be deposition rate, all indicators of an elevated influx of solar cosmic rays. The depletion of nitrate ion in the acidic ice layer and its redistribution to deeper ice suggests that the snowpack surface was exposed to intense UV for a prolonged period due to the temporary destruction of the polar ozone layer. The NGRIP ice core record shows that the event occurred synchronously with an abrupt cooling and rapid warming to Alleröd temperatures. Ice deposited in the years immediately prior to the event contains some of the highest ammonium ion concentrations of the Alleröd/Younger Dryas (AL/YD) period and ice deposited immediately after the event is unusually dark, both indicating a period of global wildfires. This period likely time-correlates with the YDB layer found in North America. But since it occurs over a century after the beginning of the YD cooling, a cometary impact induced nuclear winter and conflagration is ruled out.

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