Thirty years of research, and especially the refinements of many geological, geochemical and geophysical techniques, have uncovered many new facets of the geology of the Scandinavian Caledonides, also correcting some fundamental misconceptions. Our present understanding is that of a sequence of allochthons, some derived from Baltica, but others of probably exotic origin, in part from the Laurentian margin that collided with Baltica, but perhaps also from other parts of Rodinia. The present paper summarizes the main features of the Scandinavian Caledonides, proposing some rethinking of the traditional schemes, which were developed lacking a substantial amount of the information we have today, and discusses the main advances since the last major synthesis in 1985.

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Isotope dilution thermal ionization mass spectrometry U-Pb dating and coupled Lu-Hf solution inductively coupled plasma mass spectrometry analyses of zircon were acquired from magmatic rocks along two transects across the Scandinavian Caledonides in the TromsOfoten region of Norway to explore possible correlations and gain insight into the evolution of far-travelled nappes within the Upper and Uppermost Allochthons. One pulse of magmatic activity was recorded at c. 489 Ma in the Tromsø Nappe. In the underlying Nakkedal Nappe, a magmatic pulse was recorded at c. 450 Ma, being contemporaneous with eclogite facies metamorphism in the area. Tonalites in the structurally underlying Lyngen and Gratangseidet ophiolitic complexes, both forming the substratum to carbonate -schist-quartzite sequences (Balsfjord and Evenes groups, respectively), yielded ages of 481 and 474 Ma. Obtained 1 Hf(t) values are, however, distinctly different and indicate a juvenile origin for the Gratangseidet tonalite (1 Hf(474) ¼ + 9.57) and the presence of Palaeoproterozoic source material for the Lyngen tonalite (

[1] This study documents the structural and metamorphic evolution of middle to lower crust along an oblique convergent curved continental margin during a time span of ∼60 Myr. Our study documents the importance of variable obliquity during convergence which led to the development of overprinting fabrics and distinct exhumation histories along strike of the margin. We present structural analyses, 40 Ar/ 39 Ar, Rb/Sr, and zircon fission track ages from middle to lower crust exposed along the southern Alaskan margin in the Chugach Metamorphic Complex. Together with the metamorphic history and additional geochronology from the literature we derive the following tectonic evolution for this area: accretion of sediments during dextrally oblique convergence led to strain-partitioned D 1 structures and greenschist-facies metamorphism prior to circa 55 Ma. At ∼55-51 Ma, a margin-parallel stretching phase with vertical thinning (D 2 ) affected the margin and led to andalusite-sillimanite grade metamorphism and the onset of partial melting. A switch back to dextral transpression (D 3 ) shortly after D 2 led to rapid cooling of the western and central parts of the complex associated with exhumation of parts of the core of the complex until circa 46 Ma. The southeastern part of the complex cooled and exhumed regularly and slowly until circa 5 Ma due to its highly oblique orientation relative to the convergence direction. An increase in cooling and exhumation occurred after circa 5 Ma in the entire southeastern part of the complex, associated with the Neogene collision of the Yakutat terrane.