## 5 Discussion
### Extensional Collapse in the Central Betic Cordillera  
Several models have been proposed to explain the extension in the central Betic Cordillera. On the one hand, it is understood as arc-parallel extension resulting from NW-SE convergence between Eurasia-Nubia [72, 74, 145], and uplift would derive from the formation of large E-W folds [24, 35, 59]. If so, the extension would be homogeneous NE-SW, orthogonal to the compression (Figure 5). In addition, a back-arc extension due to rollback has been suggested [31, 34]. Considering that the subduction is related to the westward movement of the arc, the extension would be E-W. These two models alone do not explain the heterogeneous character of the extension suggested by the data. On the other hand, it has been proposed that it could be the result of the subducting slab-tearing W of the Granada Basin [153, 154, 81]. In this case, slab tearing would be responsible for the uplift of the Sierra Nevada with respect to a subsided area in the Alboran Sea, but not directly for the extension. Following this line, the data presented here support the displacement from high-elevation zones surrounding the Sierra Nevada to more subsiding areas in the Western Alboran Basin, with a trend ranging from WSW in the Granada Basin to SSW to the south of the Sierra Nevada (Figure 6a). This trend and the structural data may indicate the extensional collapse of the upper levels of the crust in a WSW to S direction over the Mecina detachment in order to balance lateral contrasts in crustal thickness [136]. The uplift of the Nevado-Filabride Complex due to the overthickened crust related to westward ongoing slab tearing [81, 88], denudation processes [155], and/or folding and thrusting [24, 57, 156] may have activated the Miocene extensional detachments in the W and SW of Sierra Nevada, which is also supported by geomorphological data [157]. Additionally, the active subduction with rollback located in the western Betic Cordillera [34, 80, 88] has produced subsidence and crustal thinning in the western and northern Alboran basins [54, 158, 159], facilitating the west-southwest-southwards collapse. However, the influence of both arc-parallel extension and back-arc extension due to rollback cannot be ruled out, as the ENE-WSW extension is the predominant. The role of inherited structures of the Miocene evolution is important in the active gravitational collapse. In fact, the ENE-WSW to NE-SW extension is documented since the middle Miocene in the Granada Basin (Figure 6b) [27], and it is driven over the extensional detachment that exhumed the Nevado Filabride complex [20, 104, 106]. The activity of dextral faults extends up to Late Miocene in the Alpujarras Corridor located in the south of the Sierra Nevada [64]. The current activity of the western Alpujarras Corridor has also been suggested [113, 160] and related to a Subduction-Transform Edge Propagatorfault [161]. However, the mainly southward displacement with respect to the Sierra Nevada (NEMA) of the GNNS sites PALM, 960, and 940 (Figure 5) suggests that at present, the Alpujarras Corridor is dominated by a N-S extension, in agreement with the activity of E-W normal and normal-dextral faults, such as the Laujar de Andarax and Ugjjar Faults (Figure 6c) [136; 150; 151]. Figure 6: Simplified tectonic model of the central Betic Cordillera considering the Sierra Nevada (GNNS NEVA site) stable, indicated by a pushpin. (**a**) Extensional collapse in the central Betic Cordillera. Location of the (**b**,**c**) cross sections. (**b**) ENE–WSW profile from the Sierra Nevada, crossing the Granada Basin to the coast line of the western Alboran Sea. Crustal heterogeneities produce local shortening around the Sierra Tejeda. The upper crust model was modified from [PERSON] et al. [162]. The Moho was taken from [PERSON] et al. [163]. The upper limit of ultramafic  
rocks was taken from [PERSON] et al. [163] and [PERSON] et al. [164]. (**c**) NNW-SSE profile from the South Iberian Domain, crossing the Sierra Nevada to the eastern Alboran Sea coast.