Integrated Study of the Tectonic Evolution of the Mid-Norwegian Passive Margin

This thesis investigates the brittle tectonic evolution of the Mid-Norwegian Passive Margin (MNPM) in time and through space. A multidisciplinary and multiscalar workflow has been conceptualised and applied to collect data at several scales of observations to characterise the complex brittle evolution of the margin. The thesis first presents a high-resolution structural-geochronological study of a regional fault zone, the Lærdal-Gjende Fault in southwestern Norway. Then it presents an integrated reconstruction of the polyphase brittle evolution of the MNPM. The applied approach relied on remote sensing detection of lineaments, meso- and microstructural analysis of representative faults, paleostress inversion and K-Ar dating of fault gouges and altered rocks coupled with their mineralogical characterisation. The proposed structural-geochronological model of the MNPM includes six time-constrained tectonic events. In addition, this thesis tested an innovative research theme, by providing the first clumped isotopic constraints on calcite from basement rocks and faults and by proposing their interpretation through time and in space in the context of the polyphase evolution of the margin. Clumped isotope thermometry has been applied on calcite veins associated with brittle structures. The variable geochemical results indicate that calcites derive from highly mixed meteoric and marine fluids, locally circulating within paleosols in surficial environments, during a polyphase evolution. Lastly, this thesis contains the results of the 3D modelling of the petrophysical properties and fracture distribution of fractured, weathered, dated basement outcrops, which are analogues of the offshore, fractured and weathered, structural highs that host the main hydrocarbon reserves of unconventional plays in Norway. Analysis of Virtual Outcrop Models integrated with Discrete Fracture Network modelling assisted the investigation of the relationships between sub-seismic and seismic-resolution fractures and the bulk permeability of the fractured and weathered basement volumes.