Plio-Quaternary deposits at the junction of Southern Alps, Dinarides and Pannonian Basin (SE Slovenia): a review and challenges

Southeastern part of Slovenia lies at the junction of three large tectonic entities: Southern Alps, Dinarides and Pannonian basin. Here the complex Cenozoic tectonics related to the formation of the Alps and Dinarides, and... [ view full abstract ]

Southeastern part of Slovenia lies at the junction of three large tectonic entities: Southern Alps, Dinarides and Pannonian basin. Here the complex Cenozoic tectonics related to the formation of the Alps and Dinarides, and eustatic sea-level changes followed by erosion, caused formation of an undulating landscape providing accommodation space for various sedimentary infills in intramountain basins. Onset of youngest terrestrial sedimentation is marked by successions of alluvial clastic sediments forming a unit traditionally called the “Plio-Quaternary”. These sediments, that locally exceed thickness of 200 m, are currently interpreted as molasse sediments deposited in shelf-edge deltas, or as terrestrial sediments deposited in intramountain basins. They are preserved in topographic depressions, as well as in highs, indicating that active tectonics played an important role after their deposition. Up to this point studies were focused mainly to gravel deposits. The gravel consists of quartz sandstone, conglomerate, siltstone, tuff, chert and andezite that indicates Southern Alps provenance. Past attempts to constrain the geochronology of these sediments have yielded a very wide array of ages (5 Ma – 200 ka), indicating the stratigraphy of the “Plio-Quaternary” sediments is poorly understood and the relative chronology has been misinterpreted in the past. Our investigation therefore focuses on composition, provenance, genesis and age of these sediments. First results suggest the “Plio-Quaternary unit” has diverse composition and genesis, ranging from fluvial deposition to in-situ weathering of bedrock. Detailed sedimentological, facies and geochronological analysis will follow in order to better understand the “Plio-Quaternary unit” as a key to interpret a paleoenvironmental, paleoclimatic, hydrographic and geodynamic evolution of the area.