Terrane evolution of the paratectonic Caledonides of northern Britain

A stratigraphically constrained re-evaluation of terrane amalgamation in th e Caledonides of northern Britain allows the development of a new orogenic scenario which accounts for many of the outstanding problems in the paratec tonic Caledonides and includes a new terrane template which correlates well with that proposed for Newfoundland. The Arenig Grampian Orogeny resulted from the accretion of two ale terranes to Laurentia: the Midland Valley (=N otre Dame Are in Newfoundland) and a terrane of probable Avalonian/Gondwana n origin, here termed 'Novantia' (= Annieopsquotch Accretionary Tract parti m), now hidden beneath the Southern Uplands allochthon. The Tyrone and Ball antrae ophiolites mark the northern boundary of Novantia within the composi te Midland Valley Terrane, The Popelogan-Victoria Arc-Grangegeeth Terrane a ccreted to the amalgamated Midland Valley Terrane during the late Ordovicia n and initiated the Southern Uplands thrust duplex. A brief period of north ward subduction during the Silurian followed. is ascribed to the northerly drift of the amalgamated Avalon-Baltica plate. and a final Wenlock (Scandia n) collision and caused underplating of the Midland Valley Terrane. Caledon ian deformation had ceased by the Emsian, the age of the undeformed Cheviot lavas that overlie the uplifted and peneplaned Southern Uplands.