Paul La Violette proposed that an active sun and increased comet bombardment triggered by a cosmic ray volley led to the mass die-off of mammoths 13,000 years ago – coinciding with the Younger Dryas boundary. His theory of cosmic ray bombardment goes back to 1983 when he did a PhD dissertation at Portland State University in Oregon. He postulated that every 10,000 years an intense volley of cosmic ray electrons bursts out of the galactic core of the Milky Way – presumably what has otherwise been known as super waves. See http://starburstfound.org/mammoth-extinction-due-supernova-explained-gia…
La Violette went on to have some samples of polar ice analysed (from ice cores) in a search for evidence of a supernova explosion. He found that on six occasions there was evidence of high dust content in the atmosphere – including the period encompassing the Younger Dryas event. This is usually attributed to the climate of the period which is thought to have been cool and dry – with dust blowing up from the tundra zone and from the desert zones. Unfortunately, this didn't lead anywhere particular and later, when he found evidence of heavy metals such as tin he could not get his paper published in mainstream journals as the referees claimed his sample was contaminated and tin was not present in the atmosphere in such a high proportion. Same old story line I suppose but we are hearing this from the aggrieved party rather than the peer review team.
Somewhat later in the sequence of events the Firestone and West team found evidence of a high concentration of irridium, nickel, tektites, fullerenes, nanodiamonds and helium 3 at the Younger Dryas boundary. Magenetic separates of the same time period also contained high levels of tin and copper which La Violette claims corroborates his earlier work.
La Violette's theory is more comprehensive than the Firestone and West proposal that a comet was involved as he claims the galactic outburst triggered the dust in the solar system and changed the orbits of comets and produced a myriad of meteor streams etc. Importantly, he visualised the galactic outburst caused the Sun to become more active creating an excess of CME explosions. Apparently, there was a 700 year plateau in C14 following the Younger Dryas Boundary event – which means a lot of C14 was injected into the earth system. If C14 infusions are caused by solar flares this implies a very active Sun. The peculiarity is that Firestone theorised that 41,000 years ago there was also a supernova event. La Violette objected to the Firestone theory in a variety of ways, mainly concerning the strength, velocity and ability of the proposed supernova to do the things Firestone required, on the basis, I suppose, that a galactic core outburst was nearer and therefore much stronger – or something like that. He also went on to claim the mass die-off took place over a couple of thousand years and not just at the boundary of the Younger Dryas. This is a notable weakness in the Firestone theory as it now stands because if a cometary impact or atmospheric explosion occurred at the Younger Dryas boundary a similar set of events must have occurred at the Older Dryas and Oldest Dryas events (aka Napier). The latter is dated 18,000-15,000 years ago and the Older Dryas separates the 2000 years intervening between the Oldest and Younger Dryas events. Likewise, La Violette also criticised Firestone regards a beryllium 10 peak at 41,000 years ago, saying that Be-10 was high over a 6000 year period. This actually reflects the likelihood, as suggested by some scientists, that there were two events between 40 and 30,000 years ago. If they were separated by around 5000 years this would agree with the time difference between the later Oldest and Younger Dryas and reflect an orbital cycle of some kind. We can therefore assume there are flaws in both theories.