Tectono-sedimentary evolution of high-displacement crustal-scale normal faults and basement highs on rifted margins: Klakk Fault Complex and Frøya High, Mid-Norwegian Margin

Abstract

Crustal-scale high-displacement (>10 km) normal faults are not captured in existing tectono-sedimentary models of rift basins. We used 2D and 3D seismic reflection and well data to perform a structural and source-to-sink analysis of the southern part of the Klakk Fault Complex and the western part of the Vingleia Fault Complex, Mid-Norwegian rifted margin. The north–south trending Klakk Fault Complex has a zig-zag to sinuous plan-view geometry, forming a series of structural recesses and salients along strike. In cross-section, the fault complex has a listric to convex-up or low-angle planar geometry with displacements above 20 km. This fault complex exhumed basement highs, the Frøya High and Sklinna Ridge, in its footwall and created a series of supradetachment basins, for example, the Rås Basin, in its hanging wall. In contrast, the northeast-southwest trending Vingleia Fault Complex has a zig-zag geometry in plan view and planar to listric geometry in cross-section and displacement of up to 5 km. This fault has the Frøya High in its footwall and the southern Halten Terrace in its hanging wall. Restoration of selected structural cross-sections shows a prominent fault-parallel ridge, up to 15 km east of the Klakk Fault Complex interpreted as a palaeodrainage divide. This divide separates steep drainages developed along the west-dipping footwall scarp to the Klakk Fault Complex, from broader, gentler east-dipping drainages up to ca. 10 km long developed on a back-tilted dip slopes along the eastern side of the Frøya High and Sklinna Ridge. Progressive headward erosion of active flank catchments was enhanced around topographically elevated structural salients to the point of capturing previous dip-slope-directed drainages during the earliest Cretaceous. A network of submarine canyons develop down-dip of the drainage catchments along the Klakk Fault Complex scarp, whose geometries and length are controlled by their location with respect to the structural salients or recesses, and the presence of fault terraces. The middle Jurassic-earliest Cretaceous synrift deposits form two seismic sequences that are filled with five distinctive seismic facies that record the evolution from a linked normal fault during rift climax to a high-displacement stage. During the high displacement stage, exhumed local continental core complexes formed structural salients, separated along strike by structural recesses at the heads of supradetachment basins. Key elements of the high-displacement fault stage include (i) the development of structural salients at sites of rift climax displacement maxima, (ii) development of supradetachment basins in rift climax displacement minima and (iii) migration of major depocentres away from the centre of rift climax fault segments. We synthesise these observations into a generic tectono-sedimentary model for high-displacement faults.