Guillermo Booth-Rea

Slab tearing strips the lithospheric mantle beneath orogenic arcs, driving extension, magmatism and subsequent topographic uplift, as recorded in the eastern Betic basins. We combine structural analysis with detrital zircon U-Pb dating of basement units and basin fill to reconstruct the tectonic evolution and source-to-sink dynamics of the Lorca and Sorbas-Vera basins over the slab tearing interval (15 to 4 Ma). The upper-crustal extension direction changed repeatedly and, together with a migrating dynamic topography, reshaped sediment routing and basin fill. Pre-slab-tearing upper-crustal NW-SE extension (15 to 10.5 Ma) coincided with Nevado-Filabride underplating and shortening in the Foreland Thrust Belt (FTB), with sediment sourced from the Malaguide-Alpujarride complexes. In the early Tortonian (ca. 11 Ma) garnet schist and amphibolite clasts record the onset of Nevado-Filabride unroofing. During slab tearing (10.5–7 Ma), extension shifted to NE-SW, with maximum subsidence and Si-K-rich magmatism. In the post-slab-tearing phase (7–6 Ma) extension changed to NW-SE, preceding regional tectonic inversion. Flexural rebound and mantle upwelling drove topographic growth over the delaminated region, uplifting structural blocks that disrupted earlier northward drainage patterns, sourcing a new zircon-poor Almagride basement. Since 6 Ma, topographic gradients reversed, shifting the sediment source northward to the Betic-FTB crust, which retained its orogenic root. Transcurrent inversion drove localized basin uplift and zircon reworking, including Alpine 14-20 Ma and volcanic 8 Ma zircons. FTB shortening, shifts in extensional directions, arc-delamination magmatism, dynamic topography and tectonic inversion together shaped the source-to-sink evolution of the southeastern Betics.

Slab detachment strips the lithospheric mantle beneath orogenic arcs, driving extension, magmatism, and subsequent topographic uplift—a tectonic evolution exemplified in the eastern Betic basins. We investigate the tectonic evolution and source-to-sink dynamics of the basins using fault analysis and detrital zircon U-Pb dating covering the slab detachment period (15 to 4 Ma). The direction of extension rotated repeatedly with evolving dynamic topography, altering sediment transport patterns and basin fill. Pre-detachment upper-crustal NW-SE extension (14 to 10 Ma) coincided with crustal underplating and WNW-directed shortening in the Foreland Thrust Belt (FTB). In this context sediment was sourced from the underlying hinterland-domain. This pattern changed around 11 Ma with contributions from the uplifted northern FTB and deposition of Tertiary zircons from the subducted south-Iberian paleo-margin, sourced from the south. During slab detachment (10–7 Ma), the extension direction shifted to NE-SW, accompanied by maximum subsidence and intense magmatic activity. The extension direction changed again to SE-NW in the post-detachment phase (7–6 Ma), immediately preceding regional transpressive tectonic inversion. Post-detachment extension was driven by flexural rebound and mantle upwelling, resulting in significant topographic growth over the delaminated region. Uplifted structural blocks disrupted earlier northward drainage patterns. During the Pliocene, topographic gradients reversed, and the main sediment source shifted northward to the thicker Betic-FTB crust, which had retained its orogenic root. Transcurrent inversion drove localized basin uplift and zircon reworking. The interplay among FTB shortening, shifts in extensional directions, magmatism, dynamic topography and tectonic inversion repeatedly redefined the source-to-sink evolution in the southeastern Betics.

Narrow Orogenic Arcs (NOA) on Earth are oftenly biodiversity hotspots, where biogeographic evolution is influenced by tectonic forcing. However, the relationships between tectonic mechanisms intrinsic to NOA, landscape evolution and speciation forming biodiversity hotspots have not been dwelt with. Different mechanisms inherent to NOA, such as slab roll back, slab tearing, edge delamination, mantle upwelling and flow around subducted slabs, basin and archipelago migration and volcanic arc growth drive a dynamic landscape evolution that fosters processes of dispersal and allopatric-speciation. Here, we show this with examples from the Western Mediterranean and Caribbean. Slab tearing drives migrating waves of tectonic uplift and subsidence at the edges of orogenic arcs, coupled with crustal thickening followed by heterogeneous extension, forming endorheic basins and marine gateways among high-elevation ranges. Furthermore, vicariant events by isolation in high-elevation mountain ranges, internal drainage basins, stranded back-arc and volcanic arc archipelagos- seem to have driven the distribution and diversification of many taxa. Dispersal events would have been promoted by- drifting forearc archipelagos, changes of river courses (captures) and land bridges between continents, where ancient lineage dispersal followed by allopatric speciation-multiple diversification resulted in the current complex biological assemblages. The characteristic time and space migration of NOA, fosters recurrent processes of dispersal and vicariance, including in situ diversification through time. In this setting, long-time emerged parts of both drifting-forearc or stranded-backarc archipelagos represent both refuge and diversification centers where insular fauna may relate to distant, previously- attached land masses or islands. This is the case of drifting islands like the late Miocene Alboran archipelago in the Gibraltar arc or the Present Margarita island in the Caribbean, bearing biota with most common recent ancestors in the Balearic islands or the Central Coastal Range of Venezuela, respectively. Insular lineages may disperse by the closure of marine gateways between the mainland continents and drifting archipelagos, a process that may also drive the isolation of confined seaways, like the Mediterranean during the Messinian Salinity Crisis. Topographic uplift closing marine gateways or restricting seaways may occur by lithospheric rejuvenation, following delamination or detachment of subducted subcontinental mantle slabs and also by the growth of a volcanic arc. The emergence of new land and islands in the forearc domain, results in speciation and less species-rich communities in the direction of slab retreat.

Mineralization processes in the Tell-Atlas of North Africa coincided with magmatism, extension, and lithospheric rejuvenation during the middle to late Miocene. This review examines the lead isotope compositions and Pb-Pb age dating of ore deposits in the region to elucidate the sources and timing of mineralization events. The data reveal a predominantly radiogenic signature in the ores, indicating that the primary component is from a crustal source, with a contribution from the mantle. Pb-Pb age dating suggests the ranges of mineralization ages, with late Miocene events being particularly significant, coinciding with proposed sub-continental mantle delamination following subduction of the African lithosphere. In this context, polymetallic mineralizations formed related to felsic magmatism, hydrothermalism driven by extensional faults, resulting in the formation of Mississippi Valley-Type, and Sedimentary exhalative deposits within associated semi-grabens and diapirism. The correlation between orogenic extensional collapse, magmatism, and mineralization underscores the importance of understanding the specific geological context of ore formation. The detachment of subducted slabs and subsequent influx of hot asthenosphere play pivotal roles in creating conducive conditions for mineralization. This study sheds light on the intricate interplay between tectonic mechanisms, mantle-crust interactions, and mineralization events in the Tell-Atlas, offering insights for further exploration in the region.

We present a characterization of a poorly studied karstic aquifer, documenting the geometry, resistivity properties and the control of structural discontinuities that affect the Ypresian limestone cropping out in the Mateur imbricated thrust zone in northern Tunisia. The karst system was produced by meteoric diagenesis. Geophysical methods and field investigations were useful in extracting geological features. First, our findings suggest that N110–N140 directions are the preferred dissolution paths orientated parallel to strike-slip and extensional faults. Second, the gravity data analysis (regional–residual separation, horizontal gravity gradient and Euler deconvolution) show a particular tectonic node as a junction of the NE–SW and NW–SE directions. Third, 2D electrical resistivity models display various karstification typologies with high (>1000 Ω m), medium (between 200 and 1000 Ω m) and low ( Ω m) electrical resistivity zones. These electrical resistivity models have contributed to the establishment of a conceptual structural model of the global karst features. Finally, 2D electrical resistivity tomography (ERT) and 1D time-domain electromagnetic analysis highlighted the presence of potential water zones integrated into the aquifer. Thematic collection: This article is part of the Karst: Characterization, Hazards & Hydrogeology collection available at: https://www.lyellcollection.org/topic/collections/karst

Cenozoic extension in the Western Mediterranean has been related to the dynamics of back‐arc domains. Although, in most of its orogenic belts extension propagated into the fore‐arc nappe domains. Here we revisit the structure, metamorphism and radiometric ages of the Tunisian Tell, where HP/LT rocks (350°C at 0.8 GPa), were exhumed by the sequential activity of extensional detachments after heating and decompression (410°C–440°C at 0.6–0.3 GPa) in a plate convergent setting. Normal faults thinning the Tunisian Tell detached at two different crustal levels. The shallower one cuts down into the Atlas Mesozoic sequence, involving Tellian Triassic evaporites in the hanging‐wall forming halokinetic structures in the Mejerda basin late Miocene. The deeper‐detachment bounds metamorphic domes formed by marbles and metapsammites from the Atlas domain. Illite crystallinity on Triassic rocks shows epizonal to anchizonal values, at deep and intermediate structural depths of the Tell‐Atlas nappe belt, respectively. New U‐Pb 49.78 ± 1.28 Ma rutile ages from Tellian metabasites, together with existing phlogopite 23–17 Ma K‐Ar ages in Atlas marbles from the footwall of the deepest detachment, indicate a polymetamorphic evolution. The Tell rocks underthrusted the Kabylian flysch in the early Eocene. Further, early Miocene shortening thrusted the metabasites over lower‐grade sediments, producing HP/LT metamorphism and ductile stretching at the base of the Atlas belt. The exhumation of midcrustal roots of Western Mediterranean nappe belts after tectonic shortening is a common feature related to tearing at the edges of the subduction systems and inboard delamination of their subcontinental lithospheric mantle.

Paleogeographic reconstructions of the Western Mediterranean are often based on the present location of sedimentary outcrops. However, most geodynamic and biogeographic models for the region have highlighted the importance of up-to-hundreds of km of horizontal displacements of the terrains forming the western Mediterranean orogenic arcs since the early Miocene until the Pliocene. Here we update the known paleogeographic evolution for the westernmost Mediterranean, considering published biogeographic and recent new geological constraints, including paleontological, stratigraphic, tectonic kinematic data, seismic reflection lines, low-temperature thermochronological dating, detrital zircon age populations, among others. During the Burdigalian to Langhian the rocks of the Betic hinterland, corresponding to the Alboran domain, where exhumed in a forearc setting as far East as Mallorca, now located 450 to 700 km of their present outcrops. Those exhuming rocks floored sedimentary basins among an island archipelago. The land connection between Mallorca and Alboran domains continued until the Serravallian as attested by the shared fossils of vertebrate insular fauna and biogeographic data of different taxa including trap-door spiders, beetles and fresh-water planarians. The westward migration of the Alboran forearc archipelago and its overlying basins (currently forming the Betic intramontane and western Alboran basins) was concomitant to the Langhian to Tortonian opening of the Algero-Balearic back-arc basin and the retreat of the Betic-Rif subducted slab. At a smaller scale, the Granada supra-detachment intramontane basin moved > 100 km between the Tortonian and Present, implying that previously interpreted, emerged domains, like the Sierra Nevada island where either inexistent or in a different location during the Tortonian. Sediment interpreted to represent marine gateways around and through the Alboran archipelago in the westernmost Mediterranean, may have being partially deposited as far East as Mallorca, and probably migrated westwards from the Langhian to the late Pliocene in the Gibraltar straits. Of particular interest, is the Late Messinian to Late Pliocene westward migration of the Gibraltar straits documented by sedimentary onlap over erosive channels in the Western Alboran basin and marine terraces along its Betic and Rif shores. The above proposals are evolving questions concerning the Neogene paleogeographic evolution of the Western Mediterranean that may be tested by future work and drilling.

Cenozoic extension in the Western Mediterranean is related to the dynamics of back-arc domains. However, extension propagated into the external Foreland Thrust Belts (FTB) of the region. Here we revisit the structure, metamorphism and radiometric ages of the Tunisian Tell FTB, where HP/LT blastomylonitic rocks (300-370ºC at 0.9-1.0 GPa), were exhumed by the sequential activity of extensional detachments. Normal faults thinning the Tunisian Tell FTB detached at two different crustal levels. The shallower one cuts down into the Atlas Mesozoic sequence, involving allochthonous Triassic evaporites at the base of the hanging-wall that form halokynetic structures intruding the Mejerda basin Late Miocene infilling. Meanwhile, the deeper-detachment level bounds metamorphic domes formed by marbles and metapsamnites. Illite crystallinity of Triassic rocks in the region shows epizonal to anchizonal values, at deep and intermediate structural depths of the Tell-Atlas FTB, respectively. New U-Pb 49.78 ± 1.28 Ma rutile ages together with existing K-Ar ages in marbles at the footwall of the deepest detachment, indicate a polymetamorphic evolution. The Tell Triassic rocks underwent Cretaceous extensional metamorphism, followed by crustal thickening and rutile growth in the Early Eocene. Further, Early Miocene thickening thrusted the metadolerites over lower-grade sediments, producing HP/LT metamorphism overprinting the base of the FTB. The exhumation of midcrustal roots of western Mediterranean FTBs after the tectonic shortening phase is a common feature of other FTB´s, like the Betics and Rif, which underwent a late-stage tearing at the edges of the subduction system together with delamination of their subcontinental lithospheric mantle.

This work analyses the tectonic evolution of Northern Tunisia from the Late Miocene to Present. Two orthogonal extensional systems with ENE- and SE-directed transport produced the extensional collapse of the Tell and Atlas Foreland Thrust Belts (FTBs) in northern Tunisia during the Late Miocene to Pliocene in a context of NW-SE plate convergence between Africa and Eurasia. These systems produced the extensional denudation of the Tunisian Atlas and Tell foreland thrust belts, which we related to deep mantle tectonic mechanisms, known as a common feature in other FTB´s in the western Mediterranean, i.e. Betics, Rif, Calabria and Apennines. Low-angle normal faults have extended and reworked the Tunisian Tell external foreland thrust belt, exhuming midcrustal lower-greenschist metapelites and marbles with Triassic protholiths, and forming Late Miocene basins. This extension was followed by later Pliocene to Present tectonic inversion, developing the active shortening structures in Northern Tunisia. The main shortening structure is formed by different reverse and strike-slip fault segments, linked forming the 130 km long Alia-Thibar fault zone. Restored Plio-Quaternary deformation observed on reflection seismic lines indicates deformation rates around 0.6-0.8 mm/yr in the studied segments and larger amounts of shortening to the West of Northern Tunisia (16%) than to the East (7%), which suggests that tectonic inversion started earlier to the West and later propagated eastwards, reaching Northeastern Tunisia in the Late Pliocene. Due to the young age of this tectonic inversion, the present relief of Northern Tunisia is characteristic of a young thrust and fold belt, with dominating axial valleys along synforms and an incipient transverse drainage development propagating from West to East.

The Mallorca Foreland Thrust Belt (FTB) is stranded in the Western Mediterranean, isolated among deep basins from its corresponding hinterland domain. Here we integrate new structural data from Mallorca with preliminary detrital zircon data and previously published stratigraphic, paleontological, biogeographic and tectonic constraints, to provide a new tectonic evolutionary model for the Western Mediterranean. Mallorca underwent two Cenozoic rifting phases in the Oligocene and Serravallian, before and after the development of its FTB structure. The first Cenozoic extensional event produced Oligocene to Early Miocene semigrabens coeval to felsic volcanism in Mallorca and the Valencia trough (»29-19 Ma). The Oligocene extension affected a major part of the Western Mediterranean, opening the Liguro-Provençal and other back-arc basins after the collapse of the Palaeogene AlKaPeCa orogen, and Mallorca, its former hinterland. Continued plate convergence inverted the Oligocene back-arc basin, and onshore grabens during the Early-Middle Miocene (19-14 Ma), producing the Mallorca FTB and nucleating a new subduction system in the Westernmost Mediterranean. Renewed subduction probably initiated through the collapse of a NW-SE trending transform fault, inherited from the Mesozoic opening of the Tethys ocean. Development of the Mallorca WNW-directed FTB and subduction of the South-East Iberian passive margin occurred at this stage, individualizing the Betic-Rif slab that initiated its westward retreat. Moreover, detrital zircon age-population data show that the Betic and Mallorca foreland basins shared the same hinterland, equivalent to rocks of the Malaguide complex, located at the top of the AlKa orogenic domain. A later, second rifting event produced the extensional collapse of the Mallorca FTB during the Serravallian (»14-11 Ma), coeval to topographic uplift of the Island. This later rifting was polyphasic, with two orthogonal extensional systems, producing first NE-SW, and then NW-SE extension that favored the development of continental internal drainage basins. These basins shared common insular fauna with those overlying the Alboran domain in the Internal Betics, probably forming part of the same emerged archipelago, which is further supported by biogeographic data indicating a Middle Miocene common ancestry for several taxa now present in the Betics and Mallorca. Serravallian extension occurred at the northern edge of the subduction system coeval to the Algero-Balearic basin opening. Extension initiated towards the SW direction of slab tearing or detachment, and later rotated to a NW-SE direction, probably in response to flexural and isostatic rebound. This tectonic response propagated to the Betics between the Late Tortonian and Present. By these tectonic mechanisms, including slab retreat, edge delamination under continental FTB areas of the orogen and slab tearing, the Mallorca hinterland was driven towards the southwest, contributing to the present isolation of Mallorca from its Betic hinterland.