Sensitivity of gravity and magnetic data to basalt and subbasalt structures – A case study from the Møre margin, mid-Norway

This study investigates the feasibility to use gravity and magnetic inversion to image basalts and sub-basalt structures in sedimentary basins affected by volcanism. Multiple gravity and magnetic data sets are available fro the Møre margin, mid-Norway, which are flown at different altitudes and with different line spacing. Previously, a 3D model was constructed for study area based on a wealth of seismic and petrophysical information, but the resolution of the regional 3D model prevented detailed imaging of the basalts and sub-basaltic structures. While it is difficult to identify the lateral extend of the volcanic features (at depth of 6 km) in the gravity and magnetic data, as well as in Full Tensor Gravity (FTG) data, the sub-basaltic basement architecture can be identified. The gravity gradients provide valuable information on the vertical and lateral extent below the basalts, despite the small density contrast to the surrounding, if the basalts are located in depth of less than 4 km. In such cases, inversion of the gravity and magnetic residuals, gives a better insight into the extent and thickness of the basaltic and sub-basaltic layer.