Thin-skinned fold-and-thrust belts (FTBs) have been extensively studied through both field examples and modelling. The overall dynamics of FTBs are, therefore, well understood. One less understood aspect is the combined influence of across-strike changes in the detachment properties and the basement topography on the behaviour of an orogenic wedge. In this paper, we use field data together with reflection seismic interpretation from the External Zones of the Central Betics FTB, S Spain, to identify a significant increase in the wedge basal dip (a basement "threshold") coinciding with the pinch-out of a weak substrate. This induced both changes to the wedge geometry and to the basal friction, which in turn influenced the wedge dynamics. The changing dynamics led to a transient “stagnation” of the FTB propagation, topographic build-up and subsequent collapse of the FTB front. This in turn fed an important Langhian depocenter made up of mass transport deposits. Coevally with the FTB propagation, extension took place both parallel and perpendicular to the orogenic trend. This case study illustrates how across-strike changes in wedge basal properties can control the detailed behaviour of a developing FTB front, but questions remain regarding the time-space interaction and relative importance of the basal parameters.

Hydrological functioning of wetlands must to be improved. We perform a 22-years hydrological modelling of seven playa-lakes located in a semi-arid region of southern Spain, including dry and wet periods. To do that, we applied a hydrological balance model to reconstruct past lake water levels. In addition, we investigated the hydrochemistry of the water, the basin bathymetry, and the geological setting of the watersheds, acquiring new lithology and active structures data. Once the models were constrained, scenarios considering increases on temperature and human management were implemented, and discussed. The water balance is simplified to precipitation (water input) and basin discharge (evapotranspiration), as the lakes are disconnected from groundwater because of the low-permeability substrate. In addition, unlike in previous studies, we add overflows to the modelling. The results of the model agree with actual lake water monitoring data (R² > 0.8). We observed that the hydroperiods of some of these lakes vary from permanent lakes to ephemeral, depending strongly on the basin bathymetry. Lakes with steeply margins show longer hydroperiods, whilst it is shorter for low-lying floor playa-lakes. In addition, we observed that steeply lake margins respond to active faults and/or lithological changes. To forecast the effects of climate change on the lake hydroperiods, we applied a 1 °C increase in average temperature in our hydrological modelling. The hydroperiod is significantly reduced for ephemeral playa-lakes, whilst is barely affected in permanent lakes. Moreover, we detected the high sensitivity of ephemeral playa-lakes to the anthropogenic management, including siltation, plant colonization and changes on watershed surface.

The foreland relief of alpine orogenic belts is often rejuvenated due to the intraplate propagation of orogenic deformation. Thus, in these long-lived areas, the localisation of relief rejuvenation may be largely controlled by the reactivation of previous mechanical discontinuities. In this regard, we explored the relationship between the relief rejuvenation pattern and the distribution, geometry, and kinematics of faults in a wide segment of the Betic foreland (Sierra Morena, southern Spain). Specifically, we focused on the forebulge, a WSW–ENE flexural relief that formed, paired to the Betic foreland basin, in response to orogenic load. For this purpose, we applied both qualitative and quantitative geomorphological tools, including geomorphic indices and knickpoint pattern modelling in χ space. We found that the pattern of relief rejuvenation responds to large-scale flexural uplift coupled with the tectonic activity of two groups of faults that often show evidence of reactivation, namely overall WSW–ENE faults contributing to both regional NNW–SSE relief segmentation and vertical extrusion of the forebulge, and NW–SE reverse faults associated with an outstanding WSW–ENE topographic segmentation in the west of the study area. In addition, our knickpoint modelling suggests that the faults related to the southernmost Sierra Morena mountain front have been particularly active in recent times, although their activity span and the relative uplift that they accommodate differ along the Sierra Morena/foreland basin limit. The knickpoint pattern also suggests a significant reorganisation of the analysed drainage basins. The strain partitioning accommodated by the structures involved in relief rejuvenation suggests the intraplate propagation of the transpressional deformation reported from the Betic external fold and thrust belt.

The timing and kinematics of the different types of structures and the associated vertical-axis rotations that permit an arcuate external wedge to acquire progressively its curved shape throughout its deformation history—known as progressive arcs—are key questions in natural cases of arcuate fold-and-thrust belts that we want to address through analog modeling. We present laboratory models of fold-and-thrust belts formed with a backstop that deforms in map view to simulate progressive arcs in a thin-skinned tectonic regime. Our setup makes use of a deformable backstop rigid enough to push from behind the initial parallelepiped but deformable in map view. This innovative design permits us to increase the amplitude of the arc indenting in the model as its radius of curvature decreases, that is, it simulates a progressive arc. Taking the Gibraltar Arc external wedge situated in the western Mediterranean to scale our models in terms of rheology, velocities, and sizes, four types of experiments were made. We varied the type of substratum (sand or silicone), the silicone thickness, and the width and length of the initial analog pack in order to test the influence of each of these parameters on the resulting fold-and-thrust belts. All experiments led to the formation of arcuate wedges where strain was partitioned into: (a) arc-perpendicular shortening, accommodated by thrusts which main structural trend is broadly subparallel to the indenter shape and with divergent transport directions, and (b) arc-parallel stretching, accommodated by normal and conjugate strike-slip faults. The normal and strike-slip faults contributed to the fold-and-thrust belt segmentation and the formation of independent blocks that rotated clockwise and counterclockwise depending on their position within the progressive arc. Our experiments allow to simulate and understand the finite deformation mode of the external wedge of the Gibraltar Arc. Accordingly, they shed light on how an arcuate fold-and-thrust belt can develop progressively in terms of structural trend and transport directions, types and distribution of the structures accommodating strain partition, and timing of vertical-axis rotations.

In recent decades, many wetlands in the Mediterranean watershed have dried up. We forecast the impact of climate change on the hydrology of three permanent lakes in a semiarid areo of the southwestern Mediterranean region. To achieve this, we applied daily water balance models to calculate variations in water levels and validated our approach using actual lake level measurements spanning over 20 years. To delve into groundwater/lake interactions, we calculated several hydrological indices and compared evaporation with the water level drop during extremely dry periods. After validating the three hydrological models, we applied the RCP 4.5 and RCP 8.5 climate change scenarios. We found Zóñar Lake highly resilient to climate changes because of groundwater contributions, resulting in minimal lake level oscillations even during periods of low rainfall. However, spring management and/or groundwater extractions may affect the lake hydroperiod. The Amarga and Grande lakes have weaker lake/groundwater interactions and show significant water lake level fluctuations, making them more sensitive to climate change. Indeed, our model predict that these lakes will transition into semipermanent or seasonal playa-lakes by mid-21th century. We found that deep and spring and/or groundwater-fed lakes are less vulnerable to climate changes. These results highlight the importance of developing robust hydrogeological models in such water bodies, focusing on the climate changes vulnerability of wetlands in semiarid regions, in order to formulate an integrated strategy for water resources management.