Early Tertiary structural evolution of the border zone between the Pannonian and Transylvanian Basins

Abstract

Abstract The Mid-Hungarian Lineament is the most important tectonic feature of the Intra-Carpathian area. Its evolution is closely related to the Early Tertiary (Palaeogene-Early Miocene) episodes of basin formation. This paper attempts to explain the structural relationships between the Transylvanian Palaeogene Basin and the Mid-Hungarian Lineament. Microtectonic data collected on the field, combined with the available geological and geophysical data point to the following conclusions. (1) The first compressional event is probably Early Oligocene in age, and is characterized by σ1 oriented ENE-WSW. We assume that the Oligocene basin is flexural in origin. (2) The second phase of compression occurred during Early Miocene times with σ1 oriented NNW-SSE. The last thrust emplacement accounts for the Ottnangian-Karpatian overthrusting of the Alcapa block on top of the Tisza-Dacia block. This deformational phase could have induced large-scale block rotations in both units. (3) Late Miocene left lateral faulting occurred along the Dragos-Voda fault system, the effects of which can be traced as far as Hungary. This event most probably corresponds to an eastward escape of the Tisza-Dacia block with respect to surrounding terranes.