The bending model of the Transdanubian Central Range (Hungary) in the light of Triassic palaeomagnetic data

In the Carpatho–Pannonian region, the Transdanubian Central Range is the second largest unit with changing strike along the SW–NE‐trending Mesozoic sequence. This structure was tested palaeomagnetically for oroclinal bending with the help of Triassic data, most of them derived from widespread platform carbonates. Based on nearly 700 samples, it was possible to obtain a statistically well‐defined overall mean palaeomagnetic direction for a Werfenian–early Carnian age group in the western part of the Range, and a different direction for a late Carnian–Rhaetian age group, extending over the whole length of the Range. These two mean directions are D =316°, I =38° ( k =70, α 95 =8°, n =9) and D =292°, I =57° ( k =31, α 95 =10°, n =10), respectively. The statistical parameters of these overall mean palaeomagnetic directions are comparable to those characterizing rigid areas. Nevertheless, an attempt was made to correlate the tectonic trend and palaeomagnetic declination, which lead to rejecting the model of oroclinal bending. However, it was possible to separate the late Carnian–Rhaetian sampling localities into a western (west of Lábatlan) and an eastern group, each of them with a statistically good overall mean direction: D =312°, I =56° ( k =139, α 95 =6°, n =5) for the western, and D =273°, I =54° ( k =51, α 95 =11°, n =5) for the eastern segment. The good agreement of the mean inclinations, together with an approximately 40° difference in mean declinations indicates that the Transdanubian Central Range east of Lábatlan has undergone a greater counterclockwise rotation than the western part; i.e. there is a ‘break’ in the Transdanubian Central Range between Lábatlan and Dorog (at the Tertiary Dorog Basin). Thus, the relative rotation between the western and eastern segments is in the opposite sense to that required by oroclinal bending.