I did a quick check, and I see that you are correct. I did not think that the time line had extended that far back yet, but I see that in Europe, it has been extended back to over 12,000 years. Do you know if it has been applied to the Agassiz event?
Can’t say. The melting of the N America glacial cap happened in stages over about 4000 years, each stage raising the world ocean level 100-200 feet suddenly due to collapse of ice dams. These events were roughly 9000, 11000, and 13000 years ago. The story in this article doesn’t fit this sequence well if at all.