Evidence for a Solar Cause of the Pleistocene Mass Extinction

Paul A. LaViolette March 17, 2009, submitted for publication

Abstract An abrupt rise in atmospheric radiocarbon concentration evident in the Cariaco Basin varve record at 12,887±10 calendar years before 2000 (cal yrs b2k), contemporaneous with the Rancholabrean termination, may have been produced by a super-sized solar particle event (SPE) large enough to overpower the magnetopause sheath and deliver a lethal radiation dose to the Earth's surface. This cosmic ray event, one of several to occur at the beginning of the Younger Dryas (YD), may have been the climactic episode in the Pleistocene megafaunal extinction. The earlier demise of genera could have been due to an extended period of increased solar flare activity that preceded this. The 12,887 cal yrs b2k SPE is registered in the GISP2 ice core record as a large magnitude acidity spike in association with high NO-3 ion concentrations. At the time of coronal mass ejection (CME) impact, the magnetopause collapse would have discharged the circumterrestrial dust sheath into the Earth's atmosphere, which could explain why extraterrestrial (ET) dust and magnetic spherules are present in high concentrations at the Rancholabrean termination boundary. Ammonium ion concentration peaks associated with dark bands evident in GISP2 ice several years after this event are identified with a biomass combustion episode arising during a period of excessive aridity. The Rancholabrean termination boundary is shown not coincide precisely with the beginning of the YD cooling, but to have occurred over a century later when the YD cooling trend had almost reached its maximum.

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