Cenozoic tectonic inversion in the Naglfar Dome, Norwegian North Sea

Abstract

Extensional settings with multiple phases of rifting are often intermitted by compressional tectonics or inversion. Differentiating compressional structures/phases in such settings become difficult when magma-induced forced folds are also present. This study uses a high-quality 3D seismic data to interpret tectonic inversion structures in the Naglfar Dome of the Norwegian North Sea. Cenozoic tectonic inversion in the Naglfar Dome is clearly observed in the area as (a) snakehead reflections and (b) trains of fault propagation anticlines along inverted normal faults. These structures selectively affect strata of Early Eocene to Oligocene age, indicating that both basin-wide and localised tectonic inversion have occurred in the Naglfar Dome. Early Miocene inversion in the study area occurred along reactivated, main and boundary faults between the Hel Graben and the Nyk High. Tectonic inversion in a purely extensional domain such as the Naglfar Dome post-dated the formation of a regional magma-induced forced fold. These inversion structures are cumulative consequences of the interaction of a NW-SE compression associated with a reconfiguration of plate motion during the opening of the Norwegian-Greenland Sea in the Eocene to Oligocene, active ridge push from both the Mohns Ridge and the Iceland insular margin, and far-field plate tectonic stresses associated with late stages of the Alpine orogeny. The results presented here demonstrate the rare occurrence of contractional structures within a purely extensional domain, with further implications for understanding the dynamics and evolution of faults along continental margins.