Onset of N-Atlantic rifting in the Hoop Fault Complex (SW Barents Sea): An orthorhombic dominated faulting?

- An orthorhombic fault system was analyzed through 3D seismics.
- The development of this system is related to the decoupling of deformation.
- The orthorhombic fault system indicates a 3D strain field at the onset of rifting.
- A transition from 3D to Andersonian planar strain during rifting was highlighted.
- Reactivation of deep structures possibly contributed to the strain field evolution.

The Hoop Fault Complex is one of the main fault systems in the south-western Barents Sea. This platform underwent a long extensional history under the influence of both the Atlantic and the Arctic rifts, which culminated in the Atlantic break-up in the Cenozoic. The object of this paper is the structural analysis of the late Mesozoic rifting in the Hoop Fault Complex area, based on a 10,000 km2 3D seismic volume.We constrained the intervals of activity of the main fault systems during the late Mesozoic rifting through the synsedimentary thickness variations, reconstructing the evolution of the strain field. In order to clarify the relationship between the strain field and the rheological layering, we compared the structures at different depths, highlighting a decoupling of shallow and deep deformations along the Triassic ductile clay-rich layers.A transition from an orthorhombic faulting, corresponding to a 3D strain field, to an Andersonian faulting, related to a planar strain field, was observed. The change of the strain field could be driven by the evolution of the regional stress field or, alternatively, by the reactivation of deep structures. In this latter case, the structural evolution of the Hoop Fault Complex could potentially represent a general process to be extended to other rifting settings with a similar mechanical stratigraphy.