The ‘Walled Basin’ Model of the Transylvanian Basin: Geodynamic Implications



In Central Asia several ‘walled basins’  (Carroll et al., 2010) exist which are recording thick lacustrine to alluvial deposits through geological times, and are actually showcasing the various types of strike-slip basins, in nature. Sedimentation is starting in some basins, like in the Junggar Basin, already in the Late Permian (Hendrix et al., 1992), in others during the Mesozoic (Fig. 28, 29). In western China strike-slip basins are contractional in origin, while in eastern China basins are younger pull-apart basins; the interior of these basins practically had stayed undeformed, only basin margins evolved into high to very high orogenic build-ups (Carroll et al., 2010). According to Carroll, many terms have been used to describe these basins ‘broken foreland’, ‘cornered foreland’,  ‘Chinese-type basin’, ‘collisional successor basin’.

If we recall, such walled basins can be seen in the Mediterranean area, as well, like in the case of the South Adriatic basin.

The Neogene Transylvanian Basin it is also a good candidate, in terms of basin mechanism, quality of sedimentary infill. It shows  very similar ‘walled basin’ margin character in all directions, a lacustrine-alluvial sedimentary infill, and it was called for a long time as a back-arc basin, assuming the Roydenian tectonic model. Herein, we propose to adopt the ‘walled basin’ model for the Neogene Transylvanian basin because many of the characteristics traditionally considered as mysterious  are getting a robust explanation, like 1) basin geometry, 2) sediment infill, 3) subsidence rates, 4) thickening of the lithosphere, 5) low heat flux, 6) uplift mechanism of the Southern Carpathians, 7) Peri-Carpathian basin geometry and many others that are going to be presented  in a separate paper.

We need to note, that the geodynamic evolution of the Southern Carpathians was generally neglected from the geodynamic models, because did not really fit into the back-arc model of the Pannonian-basin.  Secondly, it is obvious that the highest mountains of the Earth should share something in common regarding their origin, and geodynamic history. The Tian Shan Mts. are showing peaks of 7000m, the Caucasus has peaks above 5000m, the Atlas is rising above 4000m, the Alps have peaks of 3000m, and finally the highest peaks of Romania are found in the Southern Carpathians (above 2500m). All these very  high and relatively narrow mountain ranges are bounded by steep transpressional fault systems, just as in the case of the Southern Carpathian Mts.
