Birth and evolution of the Paleocarnic Chain in the Southern Alps: a review

The present work is aimed at reviewing the state of the art of the studies centered on the pre-collisional and collisional, Variscan evolution of the eastern Southern Alps. The main focus is on the Carnic Alps, a geologically spectacular and extremely complex area, which has been a major subject of study for structural geologists, stratigraphers, and paleontologists for more than a century. After decades of field studies aimed at unveiling the birth and evolution of this belt, the tectonic and geodynamic interpretations proposed for almost a century by two different groups of authors remain substantially different. German-speaking authors, over the decades, have consistently proposed a scenario marked by a mature, Devonian passive margin, which later on evolved into an active Mississippian continental margin; the following collisional phase resulted in an accretionary wedge that, in its evolution, might be compared to those generated by Variscan events outside the Alpine domain. On the contrary, Italian authors have mainly put forward a pre-collisional setting dominated by wrench-fault tectonics, followed by the formation of a large, collisional thrust-and-fold belt, arc-shaped in plan view. We illustrate the results accomplished so far and discuss the interpretations formulated by the two different research schools; our review provides a chance to compare the different interpretations and, at the same time, prompts the need for new and targeted data collection in the area.