[Aracelis]

That looks like a question a geologist would ask. I was thinking of it myself... Is that you?

Not this time, although the question has been on my mind.

[longshadow]

here's a thought, catalyzed in part by a comment back up the thread:

Has anyone investigated solar flare/CME activity coincident with reversal of the Earth's magnetic field as a mechanism for Mass Extinction in Earth's history?

If you were to have heavy solar activity during a period when the Earth's magnetic filed were changing polarity, I'd think there'd be a period of vulnerabilty during which the earth's surface would be bathed in x-rays from the flares and CME's.

Would there be an detectable remnant of such X-ray activity in the gelogic column, such that we could correlate such an event chronologically and compare it to instances of Mass Extinctions?

Or, be I all wet?