Seismic Analysis of Multi-Phase Tectonism in the Central Part of the Pannonian Basin in Hungary

Abstract

The exploration area is located in the Szolnok-Maramaros flysch belt which is situated on the boundary of plates of different origin. On the basis of an integrated interpretation of seismic profiles and borehole data carried out in the Szolnok area, two conclusions can be drawn: wrench faulting was dominant in the area and it occurred in two tectonic phases. The older tectonism is linked with a wide transcurrent zone penetrating to below the Mohorovicic discontinuity (Posgay et al. 1990), which can be identified beneath the flysch. The strike-slip movement was combined with compression in a NW-SE direction perpendicular to the dominant fault strike, similar to the San Andreas Fault zone. Thus, it can be identified as a convergent wrench system. The main period of wrench tectonism was Middle Miocene but it probably began before Neogene time and its activity also continued into Late Miocene times. Wrench tectonism was renewed during the Pliocene-Quaternary but its magnitude was one order smaller than the previous movements. Wrenching of the younger tectonic phase can be proved on the basis of profile and map criteria summarized by Harding (1990). Listric faults in the sedimentary sequences suggest an extensional character for the younger tectonism.