The western Mediterranean late Oligocene–Miocene basins (Alboran, Valencia and Provençal basins) are a coherent system of interrelated troughs. In all basins normal faults and thermal subsidence migrated toward the east progressively moving to the Miocene‐to‐Pleistocene Algerian and Tyrrhenian basins. All those troughs appear elements of the back‐arc opening related to the eastward roll‐back of the W‐directed Apennines–Maghrebides subduction zone, similarly to western Pacific back‐arc settings.
These late Oligocene–early Miocene basins nucleated both within the Betic cordillera (e.g. Alboran sea) and in its foreland (Valencia and Provençal troughs). The N40–70° direction of grabens is oblique to the coexisting N60–80°‐trending orogen and shows its structural independence from the orogenic roots. Thus, as the extension cross‐cuts the orogen and developed also well outside the thrust belt front, the westernmost basins of the Mediterranean had to develop independently from the Alps‐Betics orogen. Therefore, the Alboran extension, considered a classic example of a basin generated by the collapse of an orogen, cannot be ascribed to the detachment or annihilation of the lithospheric root. In contrast with the eastward migrating extensional basins, the Betic‐Balearic thrust front was migrating westward producing interference or inversion structures.