SVARTFJELLA, EIDEMBUKTA, AND DAUDMANNSODDEN LINEAMENT - TERTIARY OROGEN-PARALLEL MOTION IN THE CRYSTALLINE HINTERLAND OF SPITSBERGENS FOLD-THRUST BELT

Within metamorphic basement rocks of the hinterland of Spitsbergen's T ertiary fold-thrust bell, a 35-km-long zone of notably deformed Carbon iferous strata and Cretaceous intrusives forms a major orogen-parallel lineament from Svartfjella to Eidembukta to Daudmannsodden (SEDL). Or ientations and geometries of map-scale fault duplexes and associated f ault plane-striae populations, of folds and associated cleavage, and o f tension gashes all indicate orogen-parallel motion occurred along th e SEDL. Structural analyses indicates three phases: 1) ENE-directed ov erthrusting, 2) sinistral motion with a backthrust component, and 3) d extral 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 t he ENE in the foreland. A model where dextral transpressive motion bet ween Greenland and Svalbard was decoupled explains the hinterland-fore land 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 pa rallel motion is explicable by short-lived episode of sinistral plate motion or by local wedge extrusion during dextral transpression. The e volution of decoupling patterns has significant implications for deduc ing plate motions from local kinematic and paleostress studies.