Deformation styles and exhumation patterns in a long-lived orogen: Insights from the Albanides-Hellenides

Accretionary orogens grow through frontal accretion and crustal underplating, that contribute to crustal thickening by scraping slices of continental crust from the downgoing plate. Although geophysical data provide insights into the deep structure of these orogens, understanding the modes of crustal accretion in retreating subduction systems and the surface responses to these processes, remains challenging.

This study focuses on the Albanides-Hellenides, a long-lived subduction orogen in the Mediterranean resulted from the eastward subduction of the Adria plate beneath Eurasia since the Late Cretaceous. In the orogenic front, modes of crustal accretion have been influenced by along-strike variations in basal coupling, associated with the increasing thickness of Triassic evaporites toward the south. In the hinterland, extensional tectonics, associated with the retreating slab, led to the development of graben and half-graben structures. This geological setting provides an ideal framework to investigate the combined effect of different tectonic processes on the spatial and temporal patterns of exhumation from the foreland to the orogenic interior. By integrating tectono-stratigraphic and structural data with new and existing low-temperature thermochronological data, we aim to clarify the relationships between cooling patterns, major tectonic structures, and variations in the thickness of the evaporitic décollement level.

In the northern part of the orogen, high basal coupling resulted in crustal-scale structures that confined middle/late Miocene-Pliocene exhumation to the foreland. In contrast, toward the south, low basal coupling conditions limited exhumation related to frontal accretion, while deep crustal-scale structures focused late Miocene–Pliocene exhumation more toward the orogenic interior. In the hinterland, existing data show extension-related exhumation that progressively rejuvenated toward the foreland, from middle Miocene to Pliocene, suggesting slab rollback as dominant geodynamic driver.

Overall, our results demonstrate that from the middle/late Miocene to Pliocene crustal accretion through deep crustal-scale structures occurred at the same time as hinterland extension triggered by slab rollback. This tectonic phase likely marks the most recent stage of a long-term accretionary cycle that has driven orogenic growth by accreting slices of continental crust, contributing to significant crustal thickening in an orogen with retreating subduction boundaries.