The Afterlife of the Svalbard Caledonides

Traditionally, the Early Devonian Scandian collision of Baltica and Laurentia is considered to mark the dusk of the Caledonian Orogeny. However, in the High Arctic, the deformation and metamorphism continued at least into the Mississippian. The rock complexes affected by the aforementioned Late Devonian to Mississippian tectonic event, known as the Ellesmerian Orogeny, can be traced within an up to 400 km wide fold-and-thrust belt extending from the Canadian Arctic Islands through North Greenland to Svalbard. It is proposed that the Ellesmerian event resulted from the docking of the Pearya Terrane (currently northern Ellesmere Island), Svalbard, and other equivalent terranes to the northern Laurentian margin. However, until recently, a geochronological record of this event was largely obscure and based mostly on observations rather than radiometric data. This has changed since an amphibolite facies metamorphic complex in Prins Karls Forland of Svalbard was dated to c. 359–355 Ma (Kośmińska et al. 2020, JMetGeol). The latter discovery prompted further geochronological campaigns to define the extent of age-equivalent crystalline units in Svalbard and triggered a critical evaluation of all possible Middle/Late Devonian to Mississippian equivalents elsewhere in the High Arctic.

In this contribution, the current state of knowledge on the so-called Ellesmerian orogenic event in Svalbard will be presented. This synthesis is anchored in a broader High Arctic perspective, including new insights from the Pearya Terrane and the East Greenland Caledonides. The ultimate question arising from this summary is whether the dusk of the Caledonian orogeny and the dawn of the Ellesmerian orogeny merely overlap in time and space, or whether the two orogenic events form mutually connected subsystems of a much larger superorogenic cycle that ultimately led to the amalgamation of Pangea.