Morphotectonic evolution of the Albanides through geomorphological and cosmogenic analysis

Subduction orogens of the Mediterranean offer the possibility to explore the complex interplay between deep processes and surface morphology. The Albanides, a NW-SE-oriented fold-and-thrust belt, form part of the Northern Hellenides that were shaped by the convergence and collision of the Adriatic and Eurasian plates (Burchfiel et al., 2008; Faccenna et al., 2014; Handy et al., 2019). Stretching along the eastern margin of the Adria microplate, this orogenic system mirrors the Apennine belt on the opposite side, sharing a common paleogeographic origin inherited from the ancient Tethyan orogenic system (Argnani et al., 2013. Faccenna et al., 2001; Robertson and Shallo, 2000; Stampfli and Kozur, 2006). The Albanides, like other Tethyan belts, are primarily composed of diverse rock types: limestones from carbonate platforms and deep-water basins; ophiolites, remnants of former oceanic crust; syn-orogenic siliciclastic rocks, metamorphic and volcanic rocks from the basement (Aliaj, 2012; Muceku et al., 2006). These lithologies form a stack of tectonic units, compressed within a narrow belt only a few tens of kilometres wide (Nieuwland et al., 2000; Robertson and Shallo, 2000). Alongside with the lithological and structural organisation, the Albanides share another key feature with the Apennines—the coexistence of compressional and extensional forces, with associated tectonic structures, over short distances (Aliaj et al. 1997,1998; Burchfiel et al., 2008; Muceku et al., 2008). The combined impact of lithology and tectonics is reflected in the topographic gradient, which increases sharply across the strike of the belt. Although the Albanides have a long tectonic history dating back to the Late Cretaceous (Aliaj et al. 1997,1998; Robertson and Shallo, 2000), the more recent Quaternary tectonic and topographic evolution remains poorly understood. Previous geomorphological studies in Albania have mainly focused on understanding the formation and significance of river terraces along its major rivers (Carcaillet et al., 2009; Gemignani et al., 2022; Guzmán et al., 2013; Koci et al., 2016; Lewin et al., 1991; Woodward et al., 2001, 2008; ;). These investigations reveal that climate significantly influences terrace formation, but tectonics controls the overall incision dynamics. In particular, regional tectonic uplift, reaching up to ~1 mm/yr at the transition between compressional and extensional regimes, primarily controls the general trend of river incision, while local deviations are attributed to the activity of Quaternary faults. Hence, there is a dual contribution in creating topography of deep processes and surface faulting. River terraces have provided valuable insights into the quantification of Quaternary incision rates along major valleys, where aggradation processes occur. However, in different domains of the orogen, the occurrence of narrow and steep valleys reduces the preservation potential of the terraces and hence poses a critical challenge to fully understanding the recent evolution of this orogen. Moreover, a notable gap remains in a systematic analysis of the drainage system, particularly in the quantification of denudation rates across the Albanides. This research seeks to unravel how landscape and topography in an active orogen, such as the Albanides, respond to climate, erodibility, and tectonics. Specifically, it aims to quantify Quaternary uplift rates through denudation rates, while also exploring the connection between surface processes and deep geodynamic forces on a broader scale. To achieve these goals, we performed a detailed topographic, morphotectonic and cosmogenic analysis, by employing both traditional in situ 10Be on quartz-bearing lithologies and the innovative meteoric 10Be/9Be on lithologies that do not contain quartz (here limestones and ophiolites) and have been traditionally exclude from this approach. This strategy allowed us to produce the first comprehensive landscape evolution study and the first dataset of basin-wide denudation rates for the Albanides. Denudation rates, deriving from rivers in equilibrium conditions, reflect the uplift rates in the region, and exhibit a significant spatial variability, with in situ 10Be and meteoric 10Be/9Be denudation rates ranging from 0.09 to 1.61 mm/yr. These rates indicate that the Albanian orogen is experiencing rapid denudation, and consequently uplift, with central Albania—where compressional and extensional tectonics coexist—exhibiting higher rates compared to the external regions of the orogen, which are predominantly influenced by compressional forces. In particular, we found a strong correlation between the distribution of denudation rates and the main tectonic structures, with the highest rates observed in areas where active normal faulting is superimposed on older thrust faults. Furthermore, the geomorphological analysis highlight the presence of non-lithological knickpoints bordering elevated low-relief areas, , and evidence of recent drainage reorganisation. These features, alongside the variability of denudation rates, underscores the transient nature of the Albanian landscape. We interpret these findings as the result of the interplay between deep crustal accretion, occurring at the regional scale over long periods (>106 years), and the activity of upper crust normal faults at shallower levels since the Quaternary (Guzmán et al., 2013; Pashko et al., 2020). This research also highlights that the tectonic processes active in the past, such as deep crustal accretion and surface faulting from slab rollback, appear to still be shaping the landscape today. The findings open avenues for further research into paleo-denudation rates and the long-term effects of tectonic forces on landscape morphology in the Albanides, and offer a valuable foundation for future studies into the intricate dynamics between tectonic activity and surface processes, also in other similar orogenic systems. In conclusion, this study also contributes to a more nuanced comprehension of active orogenic systems globally, further helped by the successful application of the meteoric 10Be/9Be technique in lithological heterogeneous orogens.