| dc.description.abstract | The Friuli Alps, located in the easternmost part of the eastern Southern Alps in north-eastern Italy, represent the interference area of the Dinaric and Alpine mountain chains. There is a wide agreement on the general evolution of the eastern Southern Alps, which would consist of a poly-phase compressional evolution involving three main thrust systems. However, the amount and initiation of the total amount of shortening is still poorly constraint. In this study we investigate the kinematic evolution by means of structural fieldwork and by the balancing and reconstruction of a N-S cross-section by use of MOVE software for 2D modeling. Interpretation of the data led to the definition of five deformation phases (D1- D5), in which a clear distinction could be made between thin- and a thick-skinned phases of deformation. Prior to the compressional phases is the D1 NW-SE extensional phase, which is expressed by NNW-SSE oriented normal faults, related to the NE-SW separation of the Friuli platform during the Early-Jurassic. The D2 NE-SW to E-W directed Dinaric shortening started during the Eocene and is expressed by SW to W-vergent thrusting and folding. Dinaric deformation is largely overprinted by three Alpine phases; D3 – N-S thin-skinned Alpine shortening (Middle- to Late-Miocene), characterized by large scale S-vergent thrusting along flat-ramp-flat trajectories, which resulted in great amounts of transport of the Upper-Triassic and Jurassic platform formations along four main décollements (the Bellerophon, Raibl and Biancone Formation, and the Eocene flysch) and ultimately to tripling and folding of the sedimentary cover. The D4 – NE-SW thick-skinned Alpine shortening (Late Miocene – Pliocene), which is expressed by the reactivation and cross-cutting of thin-skinned structures and basement involved thrusting. The D5 – Transpressional phase (initiated during the Early –Miocene and is still active), which has been interpreted as the transpressional continuation of the D4 thick-skinned deformation and involves large scale strike-slip deformation and minor normal faulting. Due to the clear distinction between thin- and thick-skinned deformation, we were able to make an estimation of the total amount of N-S shortening since the Eocene. The balancing and reconstruction of the thin-skinned dominated model in MOVE indicates a minimum shortening of 57,2 km (51%) for the Friuli Alps. The maximum shortening is estimated on ~78,4 km. These newly proposed shortening estimates are significantly higher than the previously proposed 30 – 50 km of N-S shortening for the eastern Southern Alps during the Miocene and provide new insights on the plate tectonic setting below the Eastern Alps. This higher amount of shortening enhances the differentiation between the western and eastern Southern Alps even further and may indicate the horizontal decoupling of the Adriatic upper crust and underthrusting of the lower crust, associated to the subduction of the Adriatic plate beneath the Eastern Alps. | |
