S tructural, sedimentological and isotope-geochemical investigations on thick, carbonate formations in the Uppermost Allochthon of the Norwegian Caledonides have provided the first direct indications of the Laurentian origins of these shelf and slope/rise successions.Chemostratigraphical ages for marbles mostly range from Vendian to Cambrian. The earliest tectonic deformation, involving NW-vergent thrusts and folds in one of the nappes, is considered to relate to Taconian orogenic development along the margin of Laurentia. Subsequently, during Siluro-Devonian, Baltica-Laurentia collision, these thick successions, and plutonic complexes farther south, were detached from their Laurentian roots and retransported into the higher levels of the Scandian orogenic wedge.