Thesis Supervisor

The Ofoten-Efjorden region of north Norway contains exposures of mid-crustal levels of the Caledonian collisional system, including the lower portions of the Caledonian nappe stack and the upper part of the structural basement onto which the nappes were emplaced. This study combines field mapping, structural/kinematic analyses, metamorphic petrology, and radiometric isotope geochronology to examine the Caledonian tectonothermal history of the region. Amphibolite facies metamorphism and strong penetrative strain occurred at deep levels of the nappe stack as it was emplaced onto the western margin of Baltica. Deformation within the rock mass reflects components of foreland-directed simple-shear and sub-vertically shortened pure-shear, a pattern of deformation consistent with spreading of the allochthon during emplacement. Peak metamorphic mineral assemblages in metasedimentary rocks beneath the basal thrust of the allochthon contain garnet + kyanite + biotite ± staurolite, indicating that amphibolite facies conditions were attained by the footwall. The coexistence of rutile + almandine-rich garnet and zoisite + kyanite in these rocks is consistent with moderatel