Repeated inversion and collapse in the Late Cretaceous–Cenozoic northern Vøring Basin, offshore Norway

Abstract

The Norwegian Atlantic margin, although frequently described as passive, has seen several significant and highly variable deformation events prior to and after early Cenozoic break-up. This chronology is strongly exemplified in the northern Voring Basin, where deformation resulted in significant vertical motions, including deep erosion and sediment reworking. Post-break-up compressional deformation is well documented in the NE Atlantic margins, and is represented in the north Voring Basin by the Vema and Naglfar domes. A prominent Maastrichtian–Paleocene pre-break-up phase of compression inverted the northern prolongation of the latest Turonian Vigrid Syncline. This syncline was the fairway for the approximately 1 km-thick Santonian–Campanian Nise Formation sandstone, shed from NE Greenland and/or the western Barents Sea margin. The inversion focused on the Vigrid Syncline axis, forming an anticline here referred to as the Vema–Nyk Anticline. The anticline may have been a major trap but was breached by erosion prior to collapse due to Late Paleocene extension. The remnant eastern half of the anticline is the Nyk High. The associated flanking syncline, the Nagrind Syncline, also remains preserved. The collapsed side of the anticline is the Hel Graben, which itself was inverted in the Middle Miocene time forming the Naglfar and Vema domes. More speculatively, the development of the Vigrid Syncline and its bounding structural highs, the Gjallar Ridge and Utgard High, may also represent folds, marking the onset of compressional buckling in the mid-Norwegian–NE Greenland rift system. The repeated compressional deformation, as well as the extensional collapse, was focused on the area subjected to Early Cretaceous hyperextension. Compressional buckling under relatively low stress levels is proposed to have been due to significant lithosphere weakening caused by the hyperextension, whereby both high attenuation of the crystalline crust and serpentinization of the upper mantle contribute to the weakening. The Late Cenozoic compression post-dated the hyperextension by approximately 110 Ma, which suggests that the weakening is long-lived and that lithosphere has not been strengthened significantly through time.