# Plio-Quaternary Tectonic Activity in the Northern Nubian Belts: The Main Driving Forces
## 5 Discussion  
The spreading of opinions about the Plio-Quaternary geodynamics of the northern Nubian belts is mainly conditioned by two assumptions commonly adopted in investigating this problem. The first is based on the idea that the deformation pattern in the central and western regions has not been influenced by the westward escape of the Anatolian wedge. This belief is largely supported by the kinematic field inferred from space geodetic data, which indicates a much faster motion of the Aegean zone with respect to Anatolia, and by the speculative hypothesis that this pattern also relates to the Plio-Quaternary evolution. However, this view overlooks the possibility that such a pattern can represent a transient stage of the post-seismic relaxation that was triggered by the major activation of the NAF since 1939. The second main assumption postulates that in the Plio-Quaternary evolution, the Nubia-Eurasia convergence trend was oriented SE-NW. This trend, however, is inconsistent with the major tectonic features across the whole Mediterranean area. In particular, with the north-northeastward motion of the Adriatic plate and the configuration of the Hellenic arc (e.g., [9,72]). Furthermore, the methodology underpinning this kinematic interpretation relies on an oversimplified plate mosaic. The SE-NW Nubia-Eurasia convergence trend is also derived from the interpretation of geodetic data in some central (Hyblean-Pelagian domain) and western Mediterranean zones (northern Nubia). However, this interpretation may be misleading if these zones do not move in close connection with Nubia (Figures 1 and 3c). Tentative support for the SE-NW Nubia-Eurasia convergence is also based on the orientation of stress indicators in Iberia and the Alboran wedge (e.g., [144]). Nevertheless, this evidence could be compatible with the SSW-NNE convergence, when considering the complex kinematics of the various structures involved in the western Nubia-Alboran-Iberia-North Atlantic-Eurasia collision zone (e.g., [72]). An example of evidence that can provide important insights into the motion trend of Nubia is the orientation of the Transmoroccan fault system. Since this discontinuity was generated to allow western Nubia to decouple from its northwestern edge (Morocco), it is very difficult to reconcile the trend of that fault with an almost perpendicular motion of Nubia. Thus, it becomes clear that starting from the above speculative assumptions, many attempts to identify the driving force of the Pleistocene tectonic activity in the northern Nubia margin have finally proposed the Nubia-Eurasia convergence as the main factor responsible, even though this choice must face major problems. For instance, it is not easy to explain why tectonic activity in the Nubian belts reactivated after a period of reduced deformation. To explain this peculiar evolution one should presume a very unlikely discontinuous motion of Nubia. A critical feature that may impose significant constraints on the geodynamics of the northern Nubia margin, is the transpresional regime recognized in the Tell. This stress field is difficult to interpret solely as a result of a simple plate convergence. Explaining such a strain pattern as an effect of the two driving forces proposed here, i.e., the SSW-NNE Nubia-Eurasia convergence and the westward motion of the Adriatic-Pelagian domain, is much easier. This dynamic solution also provides a coherent framework for understanding the very complex Plio-Quaternary deformation pattern in the central and western Mediterranean regions (e.g., [72]). Moreover, the hypothesis that seismotectonic activity in the Tell can be influenced by the extrusion of Anatolia could explain why seismic activity in that zone has undergone a marked increase in the past decades, just when one can expect the most important effects of the post-1939 westward jump of Anatolia. Tectonic activity in the Moroccan zone has been mainly driven by the collision of western Nubia with the Alboran wedge and the Iberian block.