Inverted rift-orthogonal thrust systems in the Greenland–Iceland–Faroe Ridge: implications for the nature of the crust and plate tectonics

Background The thickened character of the crust at the Greenland–Iceland–Faroe Ridge has thus far been attributed to extensive magmatism related to a mantle plume. However, the plume hypothesis does not satisfy all the available data, and more recently a continental nature has been suggested for the middle–lower crust at the Greenland–Iceland–Faroe Ridge. Methods We further test this hypothesis by using recent advances in interpreting major tectonic structures and magmatic features in the crust at the Greenland–Iceland–Faroe Ridge using seismic reflection and magnetic data. Results Seismic reflection interpretation suggests that late Paleoproterozoic (to Neoarchean?), WNW–ESE-striking thrust systems of the Laxfordian Orogen (or Badcallian–Inverian belt) extend from northern Scotland and off the Faroe Islands to Iceland and are capped by a few km thick Cenozoic lavas. These were mildly reworked into NE–SW-striking folds during the Caledonian Orogeny, which were inverted during Cenozoic rifting. Conclusions The mid–lower crust at the Greenland–Iceland–Faroe Ridge is continental and truncated of late Paleoproterozoic thrust systems of the Laxfordian Orogen–Ammassalik Belt. These thrust systems hindered the development of NE–SW-striking, rift-parallel structures during subsequent tectonic episodes, which led to a relatively inefficient thinning of the crust during rifting and delayed breakup at the Greenland–Iceland–Faroe Ridge. This elongated rift-orthogonal ribbon of thinned orogenic crust flanked by oceanic crustal domains is interpreted as an orogenic bridge. This suggests a long-lived connection between Laurentia, Baltica, and Avalonia from ca. 1.8 (up to 2.6 Gyr), thus providing a new anchor for future plate reconstructions.