He has a website with some maps, and the longitudinal features mapped out. (about a quarter of the way down the page).
Looks like two loci for two separate events.
http://www.georgehoward.net/cbays.htm
Oddly, I last week took a bit of a fascination with this stuff, stirred up a bit by Yellowstone.
“Looks like two loci for two separate events.”
Actually, it looks as if there were 4 subevents in Canada, and 3 near Lake Michigan. Also if you go down further in the article there is a chart of temperature changes in Greenland. There you can see a profound and long dip that is the YOunger Dryas, but coming down from the temperature high around 15 thousand years ago (15KYA) there are three downward spikes that might represent less lethal events of the same type. So, given the 7 sub-loci, perhaps several occurred at each of these drops in temperature, until at the third one the Gulf Stream circulation was permanently disturbed for a thousand years.
Since bays overlap each other in several cases, if some can be found where the orientation is somewhat different, it might be very interesting to analyze material to determine if there was a different date for each.