During Ordovician times, most of Scotland and N. Ireland were separated from England & Wales by a wide ocean called Iapetus.

Scotland and northern Ireland formed part of an ancient continent called Laurentia, now N. America while England, Wales & Southern Ireland formed part of a continent called Avalonia which was about 30 deg. south of the equator. (See diagram).

The Skiddaw Slates (or Skiddaw Group) of the Lake District consist of metamorphosed marine sediments laid down on the northern margin of Avalonia. These slates can now be seen in the northern part of the Lake District, e.g. around Blencathra and Skiddaw. Have a look at some chiastolite slate.