Svartfjella, Eidembukta, and Daudmannsodden lineament: Tertiary orogen-parallel motion in the crystalline hinterland of Spitsbergen's fold-thrust belt

Within metamorphic basement rocks of the hinterland of Spitsbergen's Tertiary fold-thrust belt, a 35-km-long zone of notably deformed Carboniferous strata and Cretaceous intrusives forms a major orogen-parallel lineament from Svartfjella to Eidembukta to Daudmannsodden (SEDL). Orientations and geometries of map-scale fault duplexes and associated fault plane-striae populations, of folds and associated cleavage, and of tension gashes all indicate orogen-parallel motion occurred along the SEDL. Structural analyses indicates three phases: 1) ENE-directed overthrusting, 2) sinistral motion with a backthrust component, and 3) dextral strike-slip motion. This history indicates a change from orogen-perpendicular to orogen-parallel movements. Orogen-parallel movement was likely coeval with orogen-perpendicular fold-thrust transport to the ENE in the foreland. A model where dextral transpressive motion between Greenland and Svalbard was decoupled explains the hinterland-foreland difference. Basement fabric aligned with Carboniferous carbonates on the steep foreland face of an antiformal stack provided a through-going weak surface, a prerequisite for decoupling. Sinistral orogen parallel motion is explicable by short-lived episode of sinistral plate motion or by local wedge extrusion during dextral transpression. The evolution of decoupling patterns has significant implications for deducing plate motions from local kinematic and paleostress studies.