Mesozoic rifting and basin evolution on the Lofoten and Vesterålen Margin, North-Norway; time constraints and regional implications
pp 203-228

We constrain the Mesozoic tectono-sedimentary evolution of the Lofoten and Vesterålen Margin (LVM) by integrating seismic interpretations and the sedimentary record with regional correlations. The rift basins on the LVM evolved during multistage rifting in Mesozoic to Palaeogene times. Rifting in the Early Triassic resulted in deposition of alluvial fans onto a late Permian peneplain eroded into crystalline basement. This was succeeded by Mid/Late Triassic to Early Jurassic deltaic to shallow marine deposition during a period of tectonic quiescence. Subsequent uplift and erosion followed by transgression with deposition in shallow marine to continental basins mark the onset of a new rift episode in the Middle Jurassic (Bajocian). Rifting climaxed around Callovian times leading to rapid transgression and establishment of pro-delta/shelf conditions. The latest Jurassic – earliest Cretaceous was characterized by tectonic quiescence, uplift and erosion over most of the margin. Renewed rifting in the earliest Cretaceous (Valanginian) established thorough-going boundary faults with deposition of marine shales and turbidites in narrow basins. This marks the most pronounced rift event on the LVM during which the Lofoten Ridge and Marmæle Spur became prominent structural elements. Rifting ceased in the late Early Cretaceous (Albian) and was followed by tectonic quiescence lasting up to the latest Cretaceous, during which the remaining fault relief was progressively filled by marine shales. The last rift event on the LVM initiated around Campanian/Maastrichtian times, culminating with final separation and passive margin development in the Eocene. We show that Triassic through Early Cretaceous rifting developed under WNW-ESE directed extension, and is characterized by NNE-SSW striking, right-stepping en echelon normal faults linked by NE-SW to E-W striking soft- and hard linked transfer zones. One such E-W striking soft-linked transfer zone, here termed the Lofoten-Vesterålen Transfer Zone, accounts for the structural difference and several tens of kilometres dextral offset between the Lofoten and Vesterålen parts of the margin. A change in extension direction occurred during the Late Cretaceous, and the last rift event on the LVM developed under NW-SE directed extension. Similarities in the tectono-sedimentary evolution with adjacent and conjugate margins along the Norwegian-Greenland Sea indicate that the structural model and time constraints on rifting proposed for the LVM is applicable also to these areas.

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