Tectonic and exhumation history of the Albanides orogenic belt

The Earth's surface is shaped by processes operating across a range of spatial and temporal scales. Although there is awareness of the interaction among these processes, understanding exactly how orogenic processes influence each other and how this feedback affects the spatial and temporal patterns of exhumation remains a significant challenge. Orogens in a convergence setting provide an ideal environment for studying these interactions. Accretionary orogens grow through frontal accretion or deep underplating processes. Seismological and geophysical data have illuminated the deep structure of these orogens, enhancing our understanding of deep processes, and despite advancements in numerical models of surface responses to crustal kinematics, the influence of these processes on surface dynamics, as well as their respective feedback mechanisms, remains elusive. This complexity is further compounded by the interplay of various factors that can modulate these interactions. For instance, the growth of an orogenic wedge results from a delicate balance between gravitational stresses acting on the surface, shear stresses at the base, and the material flux being accreted into the wedge compared to that removed by erosion. Consequently, variations in parameters such as basal strength can significantly alter the critical taper angle, which in turn influences the spatial distribution of rock uplift, surface uplift, and patterns of exhumation. A comprehensive understanding of the interplay among various orogenic processes, such as deep crustal accretion, variations in deformation styles influenced by changes in the strength of the basal detachment, and the surface responses to these processes is essential for unravelling the tectonic history of complex orogens. The goal of this thesis is to explore the complex interplay of tectonic and surface processes in the Albanides, a subduction orogen situated within the intricate geodynamic setting of the central Mediterranean. Through an integrated approach utilizing low-temperature thermochronology, geological cross-sections, field observation, and 3D thermokinematic modeling, this research addresses critical gaps in understanding the timing and mechanisms of orogenic growth and exhumation across the orogen. Our findings reveal the underplating as the dominant process of crustal accretion in the Albanides, associated with NE-SW-oriented compression that occurred during the middle Miocene to Pliocene. However, crustal accretion exhibits different deformation styles that reflect variations in basal friction, which influence the spatial distribution of rock uplift and, consequently, exhumation. Specifically, exhumation patterns are influenced not only by the complex tectonics encompassing both contractional and extensional regimes in the external and internal sectors, respectively, but also by the mechanical properties of the décollement level. In the northern Albanides, a strong coupling between the sedimentary cover and basement rocks facilitates thick-skinned deformation, with accretion focused at the orogenic front, where middle to late Miocene to Pliocene exhumation focused. Conversely, the central and southern Albanides display a decoupling of structures, resulting in distinct deformation domains, with crustal accretion further inland, where late Miocene to Pliocene exhumation is focused. Finally, the findings elucidate the crucial role of basal friction strength in the mechanics of crustal underplating and thickening and reveal a late Miocene to Pliocene pulse exhumation associated with NE-SW compression. Considering that Africa changed its motion toward the NW during the late Miocene, the occurrence of NE-SW shortening in the Albanides represents evidence of a renewed tectonic phase within the Albanides, driven by the independent motion of Adria since late Miocene. Overall, this thesis contributes to a more nuanced understanding of the Albanides' tectonic evolution, revealing how variations in crustal deformation can lead to diverse exhumation patterns and surface responses. This emphasizes the intricate connections between deep geological processes and surface expressions in shaping orogenic systems in a context of changing geodynamic conditions across the Mediterranean.