Alpine-Carpathian-Pannonian Geodynamics: McKenzie and Royden, how far?

Abstract

<p>Since the 1980s’ the geodynamic evolution of the Alpine-Carpathian-Pannonian (ACP) region has been clearly dominated by two models: McKenzie (1978) and Royden (1984). The model of McKenzie was the first numerical model to explain the continental extension in terms of lithospheric stretching and following thermal subsidence. The model has envisaged that these two processes are recorded by the intervening sedimentary processes: the initial syn-rift phase characterized by extensional growth sequences and the subsequent thermal phase best described in terms of tectonic quiescence with no, or little deformation of the sedimentary cover. Its first application to the North-Sea has brought serious breakthrough in the understanding of its geodynamic evolution, and became a strong predictive tool for the oil and gas exploration community. Further on, the model has been tested on the Pannonian Basin by Sclater et al (1980). The results were ambiguous, and Bally and Snelson (1980) have highlighted that the syn-rift phase is not responding properly to the model. In spite of these early concerns, the McKenzie model has been widely accepted for the coming decades. Evidences from reflection seismic data coupled with well data, however were to confirm that the style and timing of extensional deformation is indeed out of the reach of model predictions. Shortly afterwards, Royden has proposed that the extension of the Pannonian Basin System area would be coupled with the compressional tectonics of the Carpathians. Royden et al.  has proposed that the motor behind the two concurrent processes would be the subduction roll-back which they thought to be represented by the Vrancea Seismic Zone (VSZ). This model was simple and elegant, to that extent that has been unanimously adopted by the whole geoscientific community without reserves for the coming four decades. While it is clear, that the VSZ is a well-documented geodynamic entity, it is problematic to pursue how far can be applied to the whole Intra-Carpathian Region (ICR). There is a growing evidence coming from a variety of regions from the ICR, such as the Transylvanian Basin, Apuseni Mountains, East-Carpathians and ultimately from the Pannonian Basin suggesting that the subduction roll-back model cannot be retained anymore as the sole and only viable solution to explain the Miocene-Pannonian geodynamics of the ACP region. Moreover, possible alternative interpretation(s) of the VSZ is calling for a full revision of the mechanisms of basin and orogenic evolution.</p>