Ultra-thick cratonic crust beneath the Varanger Peninsula, European High Arctic

Continental crust thicker than 60 km is normally confined to collisional mountain belts, yet we identify an ultra-thick (∼65 km) cratonic crust beneath the Varanger Peninsula in the European High Arctic—one of the thickest known non-orogenic crustal domains on Earth, only matched by the crust of central Finland. Our new seismological models show that the excess thickness relative to the adjacent Fennoscandian Shield is accommodated by a ∼30–35 km thick lower crust. The absence of significant topography and near-zero gravity anomalies indicates that this thick crust is unusually dense. Because the overlying Neoproterozoic sedimentary successions remain only weakly deformed, post-depositional crustal thickening can be excluded. We therefore interpret the Varanger Peninsula as the surface expression of an inherited Palaeoproterozoic cratonic block separated from the Fennoscandia Shield by the Varanger Suture. This cryptic block likely formed during a proposed Palaeoproterozoic orogeny—the Varanger Orogeny—equivalent to the Svecofennian Orogen in central Fennoscandia. This block may have later been fragmented during Neoproterozoic–Palaeozoic rifting in the Barents Sea region. Our findings highlight the long-term persistence of Precambrian lithospheric inheritance in shaping the crustal architecture of the European High Arctic.