Palaeogeographic evolution of the eastern Southern Alps through mesozoic times

The Southern Alps consist in a non-metamorphic south-vergent thrust belt, deriving from the comparatively mild deformation of a passive continental margin of the Mesozoic Tethys Ocean. Several superimposed phases of compressional Alpine deformation affected the region, generating large overthrust and strike slip structures. Tectonic shortening was strong in the western (Lombardy) and eastern portion of the chain (Carnia, Julian Alps), whereas in the intermediate region (Dolomites, Verona-Vicenza Pre-Alps) it was weak enough to still enable a sensible palaeogeography reconstruction. The uncomplete understanding of the regional strain however presently confines the reconstruction to a non-palinspastic representation of the palaeogeographic elements. The well-constrained bio-chronostratigraphic framework however makes the tracing of accurate isochronous surfaces often possible. The chronological resolution potential is generally high in the Upper Permian-lower Upper Triassic interval, particularly so in the Middle Triassic, and it is again quite good in the Middle-Upper Jurassic and in the Upper Cretaceous. The palaeogeographic reconstruction potential is obviously also influenced by the uneven outcrop distribution, the Permian-Triassic being widely outcropping in the Dolomites, the younger Mesozoic in southener areas. The examined region is generally characterised by high values of subsidence and therefore preserves some of the most expanded and continuous successions of Tethyan Mesozoic. The palaeogeographic evolution of the region was influenced by several tectonic and magmatic events including: (a) Permian rifting and huge magmatism, (b) Middle Triassic transtensional tectonics, associated with differential subsidence and climaxing into a late Ladinian magmatic event, followed by a slowing down of the deformation, (c) continental margin rifting, starting in the Late Triassic and climaxing into the Middle Jurassic western Tethys break up. This long history of tensive deformation strongly influenced the depositional evolution of the region, characterised by a strong palaeostructural-palaeogeographic inheritance