yeah got it. i was thinking of toba 71,000 years ago, a super volcano. looks like its recorded in soil as well as ice samples.
Super Volcano Toba(75,000 Years Ago)
"Their is substantial evidence to show that within the time of the super volcano Toba's eruption in the Indonesian Pacific, the world's population of homo sapiens decreased from over one hundred thousand to less than two thousand, basically because global temperatures dropped five degrees for many years. This was within the current interglacial and at its start. "
I've read that this event can still be seen in the human genetic record.
Interestingly, recently I read about an ancient human site in Indonesia just above the Toba ash layer.