MIOCENE-PLIOCENE TECTONIC EVOLUTION OF THE SLOVENIAN PERIADRIATIC FAULT - IMPLICATIONS FOR ALPINE-CARPATHIAN EXTRUSION MODELS

The Periadriatic Line (PAL) is a remarkable, several hundred kilometer long fault system of the Alpine orogen. Its dextral character was doc umented by several authors using diverse criteria, but detailed kinema tics and timing of movements had not been investigated along its whole length. Structural and paleomagnetic measurements, mapping, and strat igraphic and sedimentological studies have helped to unravel the Mioce ne-Pliocene evolution of the Slovenian segment of the PAL. Brittle def ormation was characterized by NW-SE to N-S compression and perpendicul ar tension. Deformation has resulted in dextral strike-slip faulting, folding, and tilting of beds. The first transpressional event correspo nds to the first phase of lateral extrusion of the East Alpine-Western Carpathian-Northern Pannonian block in the early Miocene (24-17.5 Ma) . After a short period of transtension during the Karpatian (17.5-16.5 Ma), dextral transpression reoccurred during the middle Miocene to Pl iocene and lasted up to the Quaternary. Middle Miocene dextral slip ca n he connected to the second phase of extrusion. The highly deformed r ocks within the dextral shear zones show variable clockwise, sometimes counterclockwise, rotations. The mechanism of rotation seems to be co mplex, ranging from regional relation to local folding due to pure or simple shear (domino-type rotation).