One summer?
So many strand-lines, so many sediment layers...IF there are 45-50 does that suggest the entire 'ice-age' lake was created in less than half a century?
The summers must have been incredibly hot...;-)
There's no gradualist explanation for glaciation that works, which is why people have churned out so many (mostly) incompatible models. But regardless, the melting happened over a fairly short period of time. :')