NORWEGIAN JOURNAL OF GEOLOGY htps://dx.doi.org/10.1785/njg100-2-3 Permo–Triassic sedimentary flls and tectonic phases of Mid Norway: seismic investigation of the Trøndelag Platform Emily Barnabas Kiswaka 1 & Maarten Felix 1 1 NTNU Norwegian University of Science and Technology, N‒7491, Trondheim, Norway Keywords: • Sedimentary fll • sedimentary wedge • Trøndelag Platorm • Helgeland Basin • Froan Basin • Nordland Ridge • Tectonic phase • Norwegian-Greenland seaway Received: 13. December 2019 Accepted: 22. April 2020 Published online: 8. July 2020 Kiswaka, E.B. & Felix, M. 2020: Permo–Triassic sedimentary flls and tectonic phases of Mid Norway: seismic investgaton of the Trøndelag Platorm. Norwegian Journal of Geology 100, 202009. htps://dx.doi.org/10.17850/njg100-2-3. © Copyright the authors. This work is licensed under a Creatve Commons Atributon 4.0 Internatonal License. Seismic interpretaton (2D and new 3D surveys) has been used to investgate sedimentary flls and tming of tectonic actvity ofshore Mid Norway. This study was focused on upper Permian and Lower Triassic sedimentary basin flls, but a longer stratgraphic interval (Devonian–Upper Triassic) was analysed in order to get a broad understanding of what happened prior to, during and afer depositon of the upper Permian–Lower Triassic successions. The ages of the sedimentary flls were partly constrained by well tes. Seismic refectors and sedimentary successions below the upper Permian interval are of Late Devonian– mid Permian age. Six sedimentary fll geometries (fll type A – F) were identfed. These are (A) fault-ward thickening packages with internal strata thickening towards bounding faults, (B) wedge-shaped packages whose internal strata have more or less uniform thickness, (C) sedimentary flls containing fll type A over- lain by sedimentary strata with more or less uniform thickness, (D) gently dipping packages that thicken towards deeper areas of the basin, and downlap onto pre-existng topography, (E) gently dipping strata flling depressions, and (F) sedimentary wedge with rotated internal strata and folded top. These fll types were used to determine phases of actve tectonics and quiescent phases. Based on temporal changes of the fll types, fve late Palaeozoic–Triassic unconformites have been mapped: a nonconformity where the Palaeozoic strata onlap onto the basement, a mid-Permian unconformity, two Early Triassic unconformites and a Middle Triassic angular unconformity. Results show that Devonian– Permian, mid-Permian, late- Permian, Early Triassic, late Early Triassic, and Mid–Late Triassic rifs infuenced Introducton The Norwegian‒Greenland seaway opened as the result of multple tectonic episodes that started in the Carboniferous (Brekke, 2000) and ended with the fnal separaton during the late Palaeocene (Surlyk, 1990). Three main rifing episodes related to the opening have been recognised regionally; these are events during the late Carboniferous to early Permian (Blystad et al., 1995), middle Permian (Surlyk et al., 1984; Surlyk, 1990; Doré, 1992; Seidler, 2000; Ofedal et al., 2005; Guarnieri et al., 2017) and Early Triassic (Seidler et al., 2004; Müller et al., 2005). The late-Palaeozoic tectonics created the framework for the tectono-sedimentary E-mail corresponding author (Emily Kiswaka): emily.kiswaka@ntnu.no