Flexural basin reworked by salt-related pull-apart structures: the Adony Basin

Abstract

Several main tectonic lineaments originating in the Alps and Dinarides merge in Central Hungary to form the Mid-Hungarian Shear Zone. As these structures are hidden beneath sub-basins of the Neogene Pannonian Basin, it has long been debated whether the tectonic style of the shear zone is mainly contractional or strike-slip. New 3D seismic data allowed a detailed analysis of one of these sub-basins, the Adony Basin, located south of Budapest. Its evolution is linked to the tectonics between the southern Tisza unit of European passive margin affinity, the northern ALCAPA block with Alpine affinity, and sheared remnants of Dinaric units in between. During the Oligocene and Early to Middle Miocene, a flexural basin related to the convergent thrusting of Dinaric-and ALCAPA-derived units was developed. On the southern side, N-NW verging thrust sheets were observed. On the opposite front, Triassic carbonates of ALCAPA were thrust several kilometres above Palaeogene formations to the SW. Dextral transpression is assumed for the Middle Miocene. Local deposition of Middle Miocene salt in the basin formed a detachment surface. Late Miocene sinistral strike-slip faulting resulted in a pull-apart basin above that part of the earlier flexural basin that has not been overthrust. The margins of the basin coincided with the fronts of earlier thrusts. Faults on the basin margins partly detached on the salt, decoupling the supra-salt basin fill from the underlying formations. Within the pull-apart basin, gravity sliding on the steep margins resulted in salt welds, detachment and roll-over folds.

Discovery of the Badenian evaporites inside the Carpathian Arc: implications for global climate change and Paratethys salinity

“…Also from Hungary there are some additional boreholes transecting evaporites NW of the study area in the Zsámbék Basin and nearby according to the data repository (Jámbor et al 1976;Cserepes-Meszéna et al 2000 and publications (Cornée et al 2009;Tóth et al 2010;Palotai & Csontos 2012).…”

“…A novel approach to understanding evaporites in the geological record of the CP (Fig.7) The discovery of this new, massive evaporite occurrence and the growing evidence of more occurrences in proximity (Jámbor et al 1976;Cserepes-Meszéna et al 2000Palotai & Csontos 2012) and in the CP (Túnyi et al 2005;Bukowski et al 2007;Ćorić et al 2007) has inspired a new way of thinking of evaporites in the geological record. Though the geogra phical extent (<10 km 2 ) of the evaporites discussed here is small (Fig.…”

“…Recycling of evaporites is probably a more important process then thought before as it has been recorded from the East Slovakian Basin (Bukowski et al 2007), and from the Carpathian Foredeep (Kolasa & Slaczka 1985;Cendón et al 2004;Głuszyński & Aleksandrowski 2016) repeatedly. However, recognizing any original sedimentary structures of resedimentation might be difficult as evaporites are often tectonized also in Hungary (Palotai & Csontos 2012) following the fully-marine Badenian and preceding the very low-salinity Pannonian. This has been challenged by some authors, who call Sarmatian brackishness a mere "myth" (Piller & Harzhauser 2005).…”

“…(Palotai & Csontos 2012). According to the public database 196 m of halite and anhydrite were reported (1827-2023 m) with intercalating clay in the upper part.…”

“…Evaporites from Hungary have previously been explained by emphasis on local salt tectonics (Palotai & Csontos 2012), or occurrences only listed in data repositories (Jámbor et al 1976;Cserepes-Meszéna et al 2000. It has generally been believed that the Pannonian Basin was disconnected from the evaporitic basins and thus devoid of evaporite formation, (Balintoni & Petrescu 2002;Báldi 2006;Kováč et al 2007;Piller et al 2007) although the existence of widespread thick evaporitic successions deposited during the BSC in the Carpathian Foredeep (CFD) and the Transylvanian Basin ( Fig.…”