# Plio-Quaternary Tectonic Activity in the Northern Nubian Belts: The Main Driving Forces
## 1 Introduction  
The northern margin of the Nubian plate consists of the Tell-Rif and Atlas belts and the internal Sahara platform (Figure 1). The Atlas system includes an eastern (Tunisian) sector, a central (Algerian Sahara) sector and a western (Moroccan) sector, usually referred to as the Middle and High Atlas. It also encompasses the Tunisian Pelagian domain (Sahel), the Algerian High Plateau and the Moroccan Meseta, which are remnants of Paleozoic belts often covered by Mesozoic carbonate platforms, only slightly deformed by the Atlas orogen (e.g., [1]). The Atlas system was thrust over the Sahara platform foreland along the South Atlas Front and primarily deformed during two key tectonic phases. The first developed between the Middle Eocene and Early Miocene (Aquitanian) and the second since the Pleistocene, involving the entire Nubian margin (e.g., [2, 3, 4, 5]). The Tell system, comprising the Algerian-Tunisian sectors of the Maghebides, consists of metamorphic units (Kabylides or internal Tell) and an accretionary belt (external Tell), formed by the trench arc-back arc process that created the Balearic basin (e.g., [2; 5; 6; 7; 8; 9; 10; 11]). This process concluded around the Serravallian-Tortonian, when the southward migrating arc (Kabylides-Tell) collided with the Nubian continental domain, leading to the suture of the consuming boundary and the subsequent disruption of the related slab [2; 5; 12]. This suture was followed by a phase of tectonic quiescence in both belts until the Pleistocene, when the entire northern Nubian margin underwent a new tectonic phase, involving the thrusting, uplifting and inversion of normal faults [2; 5; 12; 13; 14; 15; 16; 17]. Compressional deformation continues along the northern Nubian belts, as evidenced by onshore and offshore geometric features and seismic activity (e.g., [18; 19; 20; 21; 22; 23; 24; 25]). The active faults indicate ongoing underthrusting of the Neogene oceanic domain beneath the Algerian margin (e.g., [2; 26; 27]). The driving force behind the Pleistocene tectonic phase remains a topic of debate. The location of the Atlas-Tell system has strongly supported the hypothesis that the deformation of these belts was driven by the Nubia-Eurasia convergence (e.g., [28; 29; 30; 31; 32] and references therein). However, a significant issue with this interpretation is explaining why this presumed force had minimal effects during the preceding extended time period. Such scenario would imply a rather discontinuous motion of Nubia, which is not supported by the deformations that occurred along other plate boundaries. Additionally, it raises questions about how the supposed plate convergence accounts for the complex spatio-temporal distribution of the Plio-Quaternary tectonic processes in the central Mediterranean area [7; 8; 9; 10; 11], including the development of major discontinuities in the Ionian and Pelagian zones, the marked northward displacement of the Maghebian belt, the southeast extrusion of the southern Apennines and Calabrian wedges and the formation of the Campidano trough in Sardinia. Some have attempted to address this issue by proposing additional driving forces, such as slab-pull and other subduction-related mechanisms (e.g., [33; 34; 35; 36]). However, these geodynamic interpretations struggle to account for major pieces of evidence (e.g., [8; 9; 11]). Regarding the current tectonic setting, the focal mechanisms and neotectonic structural data in the Atlas and Tell belts indicate that this zone is experiencing dextral shearing, thrusting and uplifting (e.g., [37; 38; 39]). This regime further challenges the notion that the zone is simply stressed by the Nubia-Eurasia plate convergence. In the next section, it is argued that the geodynamic context that can plausibly account for the central Mediterranean tectonic processes (e.g., [9]) may also explain the Plio-Quaternary deformation observed in the northern Nubian belts.