Seismic evidence for Late Proterozoic orogenic structures below the Phanerozoic sedimentary cover in the Kattegat area, SW Scandinavia

Commercial seismic reflection profiles from SW Scandinavia image Sveconorwegian orogenic structures in the late Precambrian basement beneath the thin Phanerozoic cover. We interpret (1) pronounced west to WNW dipping reflections as Sveconorwegian localized ductile shear which overprint; (2) weaker east dipping reflections, interpreted as Gothian or early Sveconorwegian compressional structures. Folded and laminar seismic fabrics may represent F and C type crystalline thrust sheets emplaced during the Gothian and Sveconorwegian events. Some of the dipping reflections are observed to sole into (3) an interval of subhorizontal reflections at 2.5-4.5 s two-way travel time, which we interpret as a "fossil" ductile to brittle transition that was unroofed during the Gothian Orogeny. (4) NW-SE striking thrusts cutting the Sveconorwegian structures may indicate a shift in the late Sveconorwegian stress field. They may represent an early stage in the subsequent Phanerozoic basin evolution in the Danish area.