The Pannonian basin: Dynamic modelling of the transition from passive to active rifting

Abstract

Abstract. We examine a number of first order features of Pannonian basin evolution in terms of the feedback relation between passive far-field induced extension and active Raleigh-Taylor instable upwelling of the asthenosphere. We show that active mantle upwelling following a phase of passive extension are viable mechanisms explaining the Pannonian basin formation. The dynamic interplay between far-field driven passive extension and active thinning of the mantle lithosphere by convective upwelling beneath the rift zone is modelled using thermo-mechanical finite element methods. Our modelling results predict a first phase of passive lithospheric thinning which is followed by a second phase of late syn-rift to post-rift active mantle lithosphere thinning due to buoyancy induced flow beneath the rift zone. The pattern of coeval extension in the thinning region and compression in the flanking regions, predicted by the numerical model, may be explained by the buoyancy forces due to lithosphere thinning. It is demonstrated that time scales of and stresses generated by both processes are comparable. The model might also explain the occurrence of late shallow mantle related decompression melts in the Pannonian region and late regional doming.

Middle to late Miocene sequence stratigraphy of the Transylvanian Basin (Romania)

“…Middle to Late Miocene compressional structures are widespread in the basin, and are also indicated by microtectonic (Ciulavu, 1999;Huismans, 1999) and seismic data (De Broucker et al, 1998;Ciulavu, 1999; our data). However, most faults stop in the salt-layer, indicating that the salt represented a major decoupling horizon, between the pre-salt and post-salt succession.…”

“…Several contrasting data have been published. Huismans et al (1997), Huismans (1999), and Ciulavu (1999) support the existence of a small scale, east-west oriented, early Mid-Miocene tensional phase in the Transylvanian Basin. However, no major regional faults have been identified so far.…”

“…By Late Sarmatian, the end of the subduction (Săndulescu, 1984;Sanders, 1999;Huismans, 1999) was accompanied by a regional uplift of the Transylvanian Basin borderlands, together with the Carpathians. This was one of the most important rising moments of the Apuseni Mountains, which did not represent an important sediment source for the basin until that time.…”

“…The regional compression generated a high rate of subsidence of the Transylvanian Basin during the late Mid to Late Miocene. There are at least three mechanisms of subsidence proposed: roll-back of the subducted plate and various associated processes (Royden, 1988;Gîrbacea, 1997;Huismans, 1999), sag basin (Tari et al, 1999) and retro-foreland (Sanders, 1999). Regardless of the proposed mechanisms, at that time the basin subsidence was very high, several times higher than during the early Mid-Miocene, or during the whole Mid-Miocene of the Pannonian Basin.…”

“…The tectonic regimes of the Middle to Late Miocene in the Transylvanian Basin indicate an overall west to east or northeast to southwest oriented compressional stress field (Ciulavu, 1999;Huismans, 1999). The compression was related to the beginning of the final collision between the Tisa-Dacia unit and the East European Platform (Săndulescu, 1984(Săndulescu, , 1988, which triggered the progressive uplift of the Carpathians (Sanders, 1999) and the emplacement of latest Outer Carpathian nappes (Maţenco, 1997;Zweigel, 1997).…”