I'm not sure exactly what OP is implying though.
 light, radiation, information, etc.
 ie, reflected, or caused some reaction
The destruction of Atlantis?
You're looking at something more like 50,000 years ago, so something like the Toba population bottleneck (which probably didn't happen 70,000 years ago).
The cleansing of saidin in the previous turning of the Wheel, might work.