Structural evolution of the Billefjorden Fault

Billefjorden Fault Zone (BFZ) in Spitsbergen is a north-south striking long-lived lineament that can be traced in the outcrops over 100 km distance (Harland et al., 1974; Haremo et al. 1990; Braathen et al., 2012; Bælum et al., 2012; Smyrak-Sikora et al., 2021). Multiple deformation events have shaped the modern geometry of the BFZ over past 370 My. The influence of these events can be traced as we move from the north towards the south along the BFZ strike. In its northern parts the lineament is developed within old pre-Caledonian basement and the Devonian sedimentary succession, in Billefjorden area it is seen within the Carboniferous and Permian strata. South of Sassenfjorden the Mesozoic units display the very complex structure, however the BZ can be traced in subsurface on the seismic sections (Bælum et al., 2012). The cropping out architecture of the BFZ enables us to reconstruct the relative history of the BFZ reactivation by analyzing the relative ages of the deformed succession and syn-tectonic deposits. However, the absolute dating of the deformation is not available for the BFZ, which limits out the understanding of processes governing the long-lived evolution of structural elements. This research project is developed around a collection of field data that include sampling of rocks along the BFZ for radiometric dating. To analyse samples in the structural context for each of the sampled location I will perform structural mapping and measurements orientations of major geological structures and acquisition of photograph for drone-based digital outcrop models. To provide a good overview of different reactivation events, this study will address around 60 km long section along the BFZ from inner Billefjorden to Adventdalen.