| dc.description.abstract | The topographic evolution of the present-day mountains of western Norway is not completely resolved. Long after the breakup of the Caledonides, the mountains along the passive continental margin of Norway remain high, with deep incising valleys and low relief surfaces at the top. The origin of this post-Caledonian landscape is cause of controversy. The ongoing debate revolves around two endmember hypotheses, where the established hypothesis suggests peneplanation at the end of the Mesozoic, with subsequent uplift. A newer hypothesis argues that the same observations can be explained by simply long-term slow erosion, glacial flattening and isostatic rebound. Both these hypotheses are founded on observations ranging from offshore sedimentary depositions, structural analysis, geophysical models and thermochronological data. Despite the multi-disciplinary approach, the interpretations of evidence remain ambiguous and there is increasing evidence that the evolution of the passive continental margin might even be more complex than either hypotheses leave to believe. This study presents the first steep vertical profile from the poorly surveyed inner Nordfjord area and provides new apatite fission track data and evidences for active fault displacement, even on less fractured mountain flanks, as well as new insights into post-Caledonian topographic evolution. The timing of faulting is closely tied to the North Sea Rifting and the development of brittle features have been affected by intrabasement ductile precursor structures. Inverse modelling of time-temperature paths indicate a low relief surface at the end of the Mesozoic. However, it remains unclear at which elevation said surface resided. During the Cenozoic this surface was further worn down and deep valleys were carved out. The results from this study indicate that the passive continental margin of western Norway tells a very complex story that most likely cannot be fully explained by either of the two endmember hypotheses. The methods used in this study and especially the steep profile allow detailed insights into the thermal and structural evolution of the upper most crustal level. Higher resolution in sampling, together with combining multiple thermal dating techniques, would increases our understanding of the Norwegian passive continental margin even further. | |
