He didnt have to go far to cross back then. The subcontinent of LAurasia was composed of a zipped together area that connected the present Scandanavian countries with Greenland and Northern Canada. There was a small opening of the proto Arctic ocean but it was pretty much one big chunk of closely located islands, sort of like the Polynesia/Melanesia of today. Turtles could basically saunter and swim through small water filled basins in a warm sub Arctic tropic. The real cold area was the growing ANtarctic because there was a water passage that separated the Northern v Southern Hemispheres.
In order to see the continental drift occur through time since the Grenville Age, I recommend the Atlantic Geosciences SOciety's Special Publication no 135. called THE LAST BILLION YEARS
It was published by Nimbus Press of HAlifax in 2001. This is one of the best general texts on the splitting continental land masses that center on Appalachian/Caledonian Terranes. It uses Maritime Canada as the focii of the various sequences of continental openings and closings.
I use it in graduate courses for the students to visualize the 3D nature of LxWxTime.