Tracking lithospheric delamination and surface processes across the Messinian salinity crisis

Domain: earth_science
Published: 2025-05-08
Editorial outcome: minor_revision

Abstract
Lithospheric delamination involves short-lived crustal and surface responses, alkaline magmatism, high heat flow and extension. In the Western Mediterranean, delamination is hypothesized to have triggered uplift at the origin of the Messinian Salinity Crisis (MSC). But delamination as the primary cause of uplift is questioned due to the insufficient temporal resolution. We report new U-Pb ages and clumped isotope analyses from calcite veins formed in an eastern Betic intramontane basin. They reveal a brief fluid event from 8.5 to 5 Ma linked to extension and retreating delamination. After extension, shortening and uplift began at 4.5–3 Ma across the boundary between the Cabo de Gata arc basement and the Iberia margin. We show that the MSC occurred before shortening and during delamination. Slab detachment caused the demise of the MSC, the formation of a new plate boundary fault and tectonic escape between Africa and Iberia around 5 Ma.

Introduction
Delamination is a process by which the lithospheric mantle or/and lower crust are detached and lost in the asthenosphere1,2. It provides an efficient mechanism to recycle crust and mantle into the convective mantle3,4, and it also explains the differentiation of the continental crust in an arc setting5,6 and in early Earth without involving two-plate subduction processes7,8. In late-/post-collision settings, continental delamination reflects the sinking of a negatively buoyant thickened or intrinsically dense lithosphere9–11 or accompanies slab rollback by decoupling the mantle lithosphere from the overlying orogen as illustrated in the Western Mediterranean, such as the Apennines12,13 and the Betic-Rif arc14–17. Eventually, the delaminated slab detaches (lithospheric tearing or break-off) leading to the development of new plate boundary faults, tectonic escape, and uplift, e.g., Anatolian Plateau uplift and the formation of North and East Anatolian Faults18–21. As delamination involves the replacement of the lithosphere by the asthenosphere, it leads to complex and short-lived crustal and surface responses, including uplift, alkaline magmatism, high heat flow, and extension. The rapid succession in time of these processes is a major difficulty in distinguishing between the causes and effects of delamination.

In the Betic-Rif arc (Fig. 1), it has been suggested that delamination, witnessed in the eastern Betics through post-collisional mantle-derived magmas at 6.3 Ma, caused the uplift of the Alboran continental margin15. This triggered the Messinian Salinity Crisis (MSC, 5.97–5.33 Ma) by closing the marine gateways between the Atlantic and the Mediterranean in the Betic Corridor (Spain) and the Rifian Corridor (Morocco)15,22. Delamination is, however, not the unique mechanism invoked for pre-MSC uplift, as it is synchronous with the onset of shortening presented as the major driver of pre-MSC late Tortonian uplift of the Betics (<7.8–7.3 Ma) and in the Rifian Corridor (7.0–7.2 Ma)23,24. Alternatively, both mechanisms can be at play. For instance, numerical models have suggested that the westward propagation of slab tearing, and detachment following delamination, stalled by around 8 Ma, resulting in resisting forces in the mantle that can explain uplift and the current tectonic activity25, notably the formation of a new convergent plate boundary between Iberia and Africa26. Other numerical scenarios have linked the pre-MSC uplift to lithospheric rebound induced by lithospheric tearing modulated by the obliquity of the convergence relative to the Iberian paleomargin27. Additional processes like the emplacement of a thick buoyant arc in the Eastern Alboran Basin (EAB) contributed to the emergence of the Alboran domain before the MSC from 10 to 6.2 Ma, and a land bridge might have persisted between Africa and Iberia during and after the MSC from 7 to 3 Ma28.

The exact relationships between uplift, onset of indentation, and mantle-derived process have not yet reached sufficient temporal resolution to allow a clear distinction between delamination, detachment, and shortening as the main drivers of the uplift and exhumation that led to the MSC. Here, we investigate the case of the eastern Betics where the continental basement of Alboran, now accreted to the southern Iberia paleomargin and intruded by mantle-derived magmas, is indented by the magmatic arc of the EAB, represented by the Cabo de Gata Volcanic Province (CGVP), and the rotated and sheared units of the Alboran basement in the Águilas Arc (Fig. 1a,b). Geodetic data shows that indentation is accommodated by the extrusion of the Alboran block bounded to the north by a broad zone of East-West right-lateral transtensional shear in the Betics, and by the left-lateral movement of the Carboneras Fault (CF) and Palomares Fault (PF) to the south-east, which continues as transpressional left-lateral shear in the Rif29,30. These fault segments are part of the Trans-Alboran Shear Zone (TASZ), a 400-km-long left-lateral fault network crossing the whole Alboran basin (Fig. 1b). The current tectonic context is the result of a complex geodynamic evolution of the Betic-Rif arc that began with subduction in the Eocene. Details of plate kinematics are debated but a consensus exists on the fact that from around 20 Ma, the Betic orogenic belt collapsed leading to the opening of the Alboran basin controlled by the westward retreat of the Gibraltar slab and delamination31. The different motion between the retreating slab domain (Alboran) and the upper plate (Iberia) caused highly oblique crustal thinning in the continental basement of the Alboran Basin throughout the Langhian to Tortonian (16-8 Ma), which led to the exhumation of E-W metamorphic domes and subsidence in intermontane basins of the Internal Betics32. The Gibraltar slab is now imaged resting at 600 km below the Alboran Sea22, and its northern edge, forming part of the Iberia continental lithosphere, is detached over 400 km (Fig. 1b) below the Betics from the Lorca basin to the region of Malaga33.

As a result of extension, the internal intramontane basins (Fortuna-Lorca, Guadix-Baza, Huercal-Overa, and Almanzora basins) and external basins (Tabernas, Sorbas, Vera, Alicante-Cartagena, Nijar-Carboneras basins) are distinguished according to their position on the margin, proximal and distal, respectively (Fig. 1a–c). Within the more distal margin, the external Tabernas basin represents an E-W-trending basin filled by Serravallian-Tortonian continental to late Tortonian deep marine deposits34 resting at ~400 m above sea level between the metamorphic domes of Sierra de Alhamilla and Sierra de los Filábres (Fig. 1a–d).

Key unknowns include the duration of extension in the Tabernas basin and its relationship to transitions with uplift, mantle-derived magmatism, slab detachment, and initiation of contraction in the eastern Betics, specifically the onset of the Carboneras plate boundary fault. To resolve these issues, we analyze new U-Pb dates tied to clumped-isotope temperatures of syn-extension calcite-filled fractures from the Tabernas basin, with a view to constraining the transition in intramontane basins from extension to compression and uplift, along with lithosphere thermal conditions. Results are compared to key transitions resolved by the analysis of the cooling evolution of the CGVP and the continental basement using apatite (U-Th-Sm)/He (AHe) thermochronology. We examine the relationships between the lithosphere structure, the thermal state in the mantle and analyze the isostatic/dynamic support of the topography. The comparison with existing age constraints on exhumation and short-lived phases of magmatism enables us to more accurately identify the mechanisms that were active before and during the Messinian Salinity Crisis, likely contributing to the onset of Mediterranean isolation.

Results
Carbonate U-Pb dating of syn-extension fractures
Carbonate samples in syn-extension fractures (veins, faults) (Supplementary Data 1) were selected along a section comprising the metamorphic basement of the Tabernas basin, exposed on the flank of the Sierra de los Filábres, and Tortonian-Messinian sediments, in the center of the basin, for in-situ Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICPMS) U-Pb geochronology. Basement samples comprise high-grade schists of the Nevado-Filábride (NF) complex (TA38, TA44) and Triassic marbles of the Alpujárride complex (TA41) that yield carbonate U-Pb ages of 7.22±0.79 Ma (TA38, n=51, 2σ), 5.05±0.27 Ma (TA44, n=112, 2σ) and 8.54±0.21 Ma (TA41, n=25, 2σ) (Figs. 1d and 2). Calcite from veins collected in lower Tortonian continental deposits (TA45, TA24) yield U/Pb ages of 5.37±0.25 Ma (TA45, n=124, 2σ) and 7.23±0.60 Ma (TA24, n=84, 2σ). Note that TA24 was sampled in lower Tortonian conglomerates exposed in the Tabernas topographic ridge, a structure interpreted as a strike-slip fault (Fig. 1d). The carbonate U-Pb date in the upper Tortonian marine turbidites (TA36) is 5.47±0.23 Ma (n=75, 2σ).

Clumped-isotope temperatures of fluids
Among these U-Pb dated samples, five (TA24, TA36, TA38, TA41, TA45) were jointly analyzed for clumped isotope temperatures (T47) and oxygen isotopic values of the mineralizing fluids (Fig. 3) (see also Supplementary Data 2). Samples from the Nevado-Filábride (TA38) and Alpujárride complexes (TA41) show similar precipitation temperatures T47 of 66.9±4.4 °C (n=3) and 63.7±4.2 °C (n=3) (°C ± 95%), corresponding to equally close values of δ18Owater of 0.7±0.7‰ VSMOW and −0.9±0.7‰ VSMOW, respectively. Lower Tortonian continental deposits (TA45, TA24) yield higher T47 of 76.2±4.8 °C and 84.5±5.0 °C, and the fluid composition also show contrasted δ18Owater of −4.6±0.7‰ VSMOW (TA45) and 3.1±0.7‰ VSMOW (TA24). Upper Tortonian marine sediments (TA36) indicate a precipitation temperature of 76.7±4.8 °C and isotopic composition of fluids δ18Owater of 0.3±0.7‰ VSMOW. The TA31 sample for which we have no U-Pb date was collected in the upper Tortonian channelized turbidites, south of the Tabernas topographic ridge, in a stratigraphic level only slightly younger than TA36. It yields a T47 of 56.4±3.9 °C and δ18Owater of −5.2±0.7‰ VSMOW.

Apatite (U-Th)/He dating of volcanic and metamorphic rocks
Five AHe ages from apatites with aliquots that replicate well were obtained in CGVP rhyolite (MOJ1.3, n=4), dacite (MOJ.1.4, n=4) and andesite (MOJ1.1, n=4; MOJ1.2, n=5; MOJ1.5, n=3) (Supplementary Data 3). Results show single-grain alpha-ejection corrected AHe ages between 10.8±0.9 Ma and 3.1±0.2 Ma. Mean AHe ages range in andesites from 4±0.2 Ma (2σ) for MOJ1.1, 9.1±0.3 Ma for MOJ1.2 and 6.1±0.3 Ma for MOJ1.5, and consistent AHe ages of 7.0±0.3 Ma for dacite MOJ1.4 (n=4) and 5.9±0.2 Ma for rhyolite MOJ1.3 (n=4). West of the Carboneras fault, only one sample out of five originally collected in the NF metamorphic basement yielded enough apatite grains suitable for AHe analyses. MOJ2.1 (n=3) sampled at 520 m in NF micaschists east of the Sierra de los Filábres yielded the youngest mean AHe age of 2.6±0.1 Ma. The scarcity of apatite in NF micaschists and their low Uranium content (0.5-1.4 ppm for MOJ2.1) has already early been noticed35. We note that in the region of the NF micaschists (Sierra Alhamilla) where these previous apatite-fission track analyses have been successful, apatite yielded slightly older ages of 5.7±1.1 Ma and 6.1±1.2 Ma. An AHe age of 15.2±0.8 Ma was obtained close to MOJ2.1 (elevation 2000 m) but it is more problematic considering it is similar to its apatite-fission track age of 15.6±1.9 Ma36. The eU-age and (U-Th)/He age relationships of our AHe-dated apatite samples show a positive correlation that agrees with the expected increase of closure temperature as a function of radiation damage37.

Time-temperature histories
Reconstruction of time-temperature histories of CGVP have been reconstructed based on simple thermal inputs assuming that published 40Ar/39Ar ages16,38 faithfully represent the timing of magma cooling below 350±50 °C (Tc350 °C on biotite), and that the timing of cooling at surface temperature (20±20 °C) is indicated by the deposition of Tortonian-Messinian marine limestones on top of sampled CGVP lavas (Fig. 4). These deposits attest to emersion as early as 10–9 Ma (lower Tortonian) while other stratigraphic contact suggests later emersion until the Messinian39,40. As the sampled dacite, andesite, and rhyolite from CGVP were emplaced at the surface, cooling is expected to be instantaneous on the geological timescales. However, the large majority of AHe ages (closure temperature of 70-50 °C) in CGVP are younger than the 40Ar/39Ar ages of their parental volcanic rocks (11±1 Ma) by 7 to 2 myrs. The delay between magma crystallization of calc-alkaline suites and AHe cooling ages reveals a complex cooling history caused by subsequent punctual thermal events. This may represent the effect of pyroclastic eruptions or lava flow, doming or caldera collapse, circulation of hydrothermal fluids linked to Cu–Au mineralization well documented during the CGVP formation41 and burial heating by Tortonian-Messinian to Pliocene deposits. Modeling results show that all volcanic rocks cooled below 350±50 °C at different rates between 12 and 8 Ma, which marks the end of the volcanic phase. After 8 Ma, samples variably recorded the deposition of the upper Tortonian-lower Messinian carbonate platform. Samples from the southern half of CGVP MOJ1.2 to MOJ1.5 show no significant heating or cooling, or it is within the uncertainties of surface temperature, hence indicating no measurable exhumation (Fig. 4). By contrast, in the north, where lower Messinian and lower Pliocene marine deposits are preserved, MOJ1.1 thermal evolution shows burial heating below sediments followed by cooling at ca. 4.5 Ma. For thermal history modeling of the MOJ2.1 micaschist sample, we have used published AHe and AFT data from a sample collected nearby. Model shows that MOJ2.1 resided at 120-80 °C (Tc AFT) and possibly 70-50 °C (Tc AHe) at 15±1 Ma, and cooled at ca. 3 Ma (Fig. 4). We infer that both CGVP volcanic rocks (MOJ1.1) and metamorphic basement (MOJ2.1) north of CF cooled between 4.5 and 3 Ma, clearly after the MSC, at a rate between 36 °C/Myr (MOJ1.1) and 48 °C/Myr (MOJ2.1).

Impact of mantle-derived processes on topography
The mean elevation of the Central-Eastern Betics (Fig. 5a) region is 868 m with the highest elevation of 3467 m in the Sierra Nevada. Receiver functions and reflection seismic data42 reveal a bimodal distribution of crustal thicknesses ranging from 35 km in the north to 25 km in the south and east (Figs. 1a and 5a), expressing crustal and lithospheric thinning south of the Sierra Nevada, Sierra de los Filábres and Sierra de las Estancias, linked to the oblique opening of the Alboran basin43. Crustal thinning onshore is reflected in the topographic decrease down to 176 m south of Sierra de los Filábres and in Cabo de Gata (Fig. 5a). The crustal thickness offshore reduces to 15 km in the EAB (Fig. 1a). To compare current topography with predictions using isostatic calculations, the lithosphere thickness across the eastern Betics was inferred from various seismic tomography models SL2013sv44, LITHO1.045, and Mean model46 (Fig. 5a). From these models, upper and lower bounds for the lithosphere thickness fall between 65 km and 50 km. The value of 65 km fits both SL2013sv and Mean models. It is also consistent with maximum depths for the lithosphere of about 60 km (1.8 GPa) independently determined from thermobarometric calculations on Neogene mantle-derived K-rich basalts (MgO > 8 wt.%, SiO2 > 45 wt.%)47. This value is within the range of thicknesses <100 km for fertile and hot phanerozoic sub-continental lithosphere48, a feature characteristic of the European lithosphere49. Elevation is calculated for a column of continental lithosphere with respect to the depth of a standard mid-ocean ridge, assuming pressure-temperature dependent densities and chemical depletion for the lithospheric mantle50 (Supplementary Discussion). Results show that for a lithosphere thickness of 65 km, the calculated elevation is negative (−250 m), assuming a crustal thickness of 25 km (Moho depth below Tabernas Basin), an average crustal density of 2.7 based on EP crust model51, and a reference density for the lithospheric mantle of 3.3 (Fig. 5b); it is null for lithosphere thickness of 50 km and −500 m for a 70 km-thick lithosphere (Fig. 5c). The lithosphere below the eastern Betics is therefore not in isostatic equilibrium unless we assume a mantle density decrease of 80-100 kg/m−3. Studies of rifted margins show that the formation of light mineral phases such as plagioclase during extension and shallowing of the lithospheric mantle can produce a density decrease of mantle rocks down to 3.2 at 60 km for temperatures above 800 °C52. This is likely to have occurred in the Betics during the Mesozoic extension as the lithospheric mantle was refertilised by tholeiitic MORB-like melts53. Alternatively, elevation can also be well reproduced by the upwelling of hot asthenosphere, likely with a fraction of melt as indicated by low S-wave velocity domain of 4.2 km.s−1 around 100 km (Fig. 5a). Based on the parametrization of shear wave velocity-temperature54 we determine anomalously high sub-lithospheric temperatures of 1550 °C. Such a low viscous channel could easily explain the observed mean topography of 500 m around Tabernas Basin (see “Methods” section and Supplementary Discussion). We infer that the compositional variations in the mantle lithosphere and asthenospheric upwelling likely acted together and contributed to the support of the eastern Betic topography.

Methods
Samples
Calcite samples were collected in veins predominantly striking NW-SE and WNW-ESE opened perpendicular to the regional extension-oriented NE-SW determined from paleostress data43 and in calcite steps on faults consistent with the same regional extension. Calcite veins are present in all the stratigraphic sections both in the basement and the overlying sedimentary series (Fig. 1d). Most veins are predominantly vertical (TA31, TA36, TA45, TA38) and locally at moderate angle (TA44) with respect to bedding, and their widths range from millimeters to centimeters (Figs. 2 and 3). The calcite crystals form generally elongated blocky syntaxial to fibrous textures (Supplementary Data 1). Fourteen slabs were prepared and polished thin sections were examined by conventional and cold cathodoluminescence microscopes to detect the different generations of crystallization/recrystallization and select the in-situ rock sample for further analyses. In most veins, one continuous single calcite phase precipitation (TA31, TA24, TA45, TA38, TA44) is observed indicating coeval opening and mineralization (Supplementary Data 1). Samples TA36 and TA41 have two generations of calcite (consistent with U-Pb analyses showing secondary late U-Pb ages, Supplementary Data 1).

Sampling for (U-Th)/He analyses has focused on the most felsic lavas in CGMP (andesite, dacite, rhyolite) (MOJ1.1, MOJ1.2, MOJ1.3, MOJ1.4, MOJ1.5) and in NF metamorphic complex (MOJ2.1) for comparing cooling histories across the Carboneras fault zone (see sample information and analyses in Supplementary Data 3). An attempt was made to select CGVP samples near marine carbonates of Tortonian-Messinian and lower Pliocene ages that were deposited after magma emplacement to place thermal constraints for modeling the post-Tortonian uplift and exhumation.

Calcite LA-ICP-MS U-Pb geochronology
Calcite U-Pb analyses were performed at the Geochronology & Tracers Facility, British Geological Survey (Nottingham, UK) using a Nu Instruments Attom single collector inductively coupled plasma mass spectrometer coupled to a NWR193UC laser ablation system fitted with a TV2 cell. Laser parameters were 100 µm spots, ablated at 10 Hz for 30 s with a fluence of ~4 J cm2 (see Supplementary Data 1 for full instrumental conditions). Normalization used WC175 as a primary reference material for Pb/U ratios and NIST614 for Pb/Pb ratios76; ASH15D77 was run as a secondary reference material and the pooled result across the analytical sessions is within 2% accuracy of the accepted age. Data reduction uses the Time-Resolved-Analysis function in the Attolab software, followed by normalization offline in Excel. Age calculations and plotting use IsoplotR78. All ages are derived from lower intercept ages on Tera-Wasserburg plots (see Fig. 2 and Supplementary Data 1), quoted at 2σ and shown as ±α/β, where α and β are without and with systematic uncertainties, respectively. Several samples were analyzed but were not used in our study due to low U/Pb ratios hindering a robust age calculation, or to highly scattered analyses indicating age mixing and/or U mobility. All data are presented in Supplementary Data 1.

Clumped isotope analysis
All analyses were performed at the Laboratoire des Sciences du Climat et de l’Environnement (LSCE, Gif sur Yvette). Six samples (TA24, TA31, TA36, TA38, TA41, TA45) of homogenized carbonate powder were converted to CO2 by phosphoric acid reaction at 90 °C in a common, stirred acid bath for 15 min. The initial phosphoric acid concentration was 103% (1.91 g/cm3) and each batch of acid was used for 7 days. After cryogenic removal of water, the evolved CO2 was helium-flushed at 25 mL/mn through a purification column packed with Porapak Q (50/80 mesh, 1 m length, 2.1 mm ID) and held at −20 °C, then quantitatively recollected by cryogenic trapping and transferred into an Isoprime 100 dual-inlet mass spectrometer equipped with six Faraday collectors (m/z 44–49). Each analysis took about 2.5 h, during which analyte gas and working reference gas were allowed to flow from matching, 10 mL reservoirs into the source through deactivated fused silica capillaries (65 cm length, 110 μm ID). Every 20 minutes, gas pressures were adjusted to achieve m/z=44 current of 80 nA, with differences between analyte gas and working gas generally below 0.1 nA. Pressure-dependent background current corrections were measured 12 times for each analysis. All background measurements from a given session within ±6 hours of any given analysis were used to determine a mass-specific relationship for that analysis, linking background intensity (Zm), total m/z=44 intensity (I44), and time (t): Zm = aI44 + P(t), with P being a polynomial of degree 2 to 4. Background-corrected ion current ratios (δ45 to δ49) were converted to δ13C, δ18O, and “raw” Δ47 values as described by Daëron et al.79, using the IUPAC oxygen-17 correction parameters. The isotopic composition (δ13C, δ18O) of our working reference gas was computed based on the nominal isotopic composition of all ETH carbonate standards80 and an oxygen-18 acid fractionation factor of 1.00813. Raw Δ47 values were then converted to the I-CDES reference frame81 using a pooled regression approach as implemented by the Δ47crunch Python library. Full analytical errors are derived from the external reproducibility of unknowns and standards (Nf = 39) and conservatively account for the uncertainties in raw Δ47 measurements as well as those associated with the conversion to the I-CDES reference frame. T47 reconstructions are based on the OGLS23 calibration (see Supplementary Data 2). Temperature confidence intervals account for analytical error in Δ47 but not for calibration uncertainties, which remain below ±1 °C (95% CL) in the range 0–50 °C. The δ18O values of the mineralizing fluids (δ18Owater) are derived from T47 and the δ18O of the mineral based on the fractionation equation.

Apatite (U-Th)/He dating
Separation and selection of apatites were carried out at the GET laboratory. Each sample was crushed to obtain grains smaller than 500 μm. Two successive steps of dense liquor separation followed to recover grains with a density between 2.97 and 3.38 (apatite density 3.2). This fraction was then magnetically sorted by Frantz. The remaining fraction, non-magnetic, was finally sorted by optical microscope (picking). Apatite crystals for (U-Th-Sm)/He dating were handpicked to select inclusion-free crystals with a minimum of three aliquots. Crystal dimension and geometry were measured along two axes, considering the apatite crystals as regular hexagonal prisms, grains had in general a minimum width of 60 μm to minimize the effect of alpha particle ejection. After this first step, (U-Th)/He analyses on apatite were performed at the Noble Gas Laboratory of the Geosciences Montpellier laboratory. Each grain, packed in Pt tubes, was placed under vacuum and heated for 5 minutes with a 1090 nm fiber laser operating at 4.0 W (900 °C). After spiking (addition of a known amount to be able to quantify the real content in the minerals) with 3He, gas purification was performed by a cryogenic trap and two AP-10-NS AES getters, and the helium content was measured on a PrismaPlus QMG220 quadrupole. The 4He content was determined by the peak height method which is 10 to 10,000 times higher than typical blank levels. A second heating cycle using the same analytical procedure was routinely performed to verify that more than 99% of the 4He was extracted in the first cycle. After helium extraction, the Pt tubes were retrieved from the sample chamber and transferred to a 2 ml polypropylene conical tube. The samples were triple spiked (149Sm, 230Th, and 233U) and dissolved following the procedures described by Wu et al.82. The resulting solutions were diluted and U (233U and 238U), Th (230Th and 232Th), and Sm (149Sm and 147 Sm) were measured using ICP MS isotope dilution. For the age calculation, it is necessary to perform the alpha (4He) particle ejection correction. This correction was calculated using Ft software considering the size, and shape of each apatite83,84. Analyses are presented in Supplementary Data 3.

QTQt thermal modelling
Thermal histories were retrieved from AHe data analyses using thermal inversion QTQt modelling software85. For AHe, QTQt incorporates kinetic models for helium diffusion in apatite crystals that account for radiation damage production and annealing (see Supplementary Data 3 for reference). These two diffusion models may produce different results, depending on the integrated thermal history of each grain. The inversion procedure uses a Bayesian “Markov chain Monte Carlo” algorithm to determine the best time-temperature path reproducing our data through a large number (between 100,000 and 200,000 on average) of randomly tested solutions. In our case, we have run nearly 170,000 models. The final model is represented by a set of time-temperature histories for which we included the expected model (weighted mean model) and the maximum likelihood model (best data fitting model). A table summarizing the thermal history model input parameters and all thermal models is provided in Supplementary Data 3.

Isostatic calculation, Vs-temperature conversion, and dynamic topography correction
The topography of continents reflects the combined effects of (1) isostasy that results from the variation of age-dependent lithosphere thickness and densities and (2) a non-isostatic (dynamic) component caused by plate strength, subduction dynamics, or more broadly mantle flow driven by anomalously hot asthenosphere. The elevation, e, of a buoyant lithospheric column in Airy isostatic equilibrium, with respect to the average mid-ocean ridge depth, is given by

e = h c (ρ a − ρ c) / ρ a + h oc (ρ a − ρ oc) / ρ a + h w (ρ a − ρ w) / ρ a + (h l − h c) (ρ a − ρ m) / ρ a (1)

where ρ, ρc, ρoc, ρw, ρm, and h, hc, hoc, hw, hl are the densities and thickness of the crust, oceanic crust, water column above the mid-ocean ridge, and continental lithosphere, respectively. The calculation assumes the density of the lithospheric mantle and the effect of compressibility. Elevation is calculated for the case of thermal equilibration and the case of the instantaneous removal of the lithospheric material by delamination, assuming no thermal equilibration at the base of the original lithosphere50. An original lithosphere thickness of 100 km is consistent with the average thickness of Phanerozoic lithosphere. Equations and parameters are presented in Supplementary Discussion.

S-wave velocities from model SL2013sv are then used to calculate temperatures in the mantle using the parametrization of ref. 54. Vs (P, Θ, a) is dependent on pressure P (depth, z), temperature Θ in °C and a which is a variable describing the activation process. Vs is given by

Vs = (1 − b(z − 50)) mΘ + c + A exp (−E − PVa / RT) (2)

where empirical constants are b = 3.84 × 10−4 km−1, m = −0.28 m.s−1 C−1, c = 4720 m.s−1, A = −1.8 × 1016 m.s−1, E = 409 × 103 J.mol−1, Va = 10 × 10−6 m3.mol−1 and R the gas constant is 8.3145 (see Supplementary Discussion). The highest temperature obtained is 1550 °C at 100–125 km below the Tabernas basin and to the south where Vs decrease to 4.2 km.s−1. Dynamic uplift U created by the temperature anomaly is then calculated assuming thermal expansivity from background temperature and Airy isostasy86 using the following equation:

U = H α T' / (1 − α T0) (3)

where H is the layer thickness, α is the thermal expansivity, T0 is the background temperature, and T' is the average temperature in the low viscous asthenospheric channel produced by the excess in temperature (parameters are provided in Supplementary Discussion). For an average thermal anomaly of 100 and 200 km the predicted uplift ranges between 500 m and 1 km. Considering the elevation of −250 m predicted by isostasy assuming pressure-temperature dependent densities and chemical depletion for the lithospheric mantle, the range of dynamic uplift can produce the elevation of 500 m observed around Tabernas Basin.

Temperature of continental lithosphere and heat flux estimates
The continental geotherm Tcont is given by

Tcont(z, age, Hs) = Tstd(z, Hs) + T(age) (4)

It is calculated using the stationary part of the geotherm Tstd and contribution due to the radiogenic heat production Hs in the crust, and T(age) due to transient cooling of the lithosphere that depends on the age of the last major plate-scale thermal event. Temperature T at Moho depth, h, is used for calculation of temperature at depths below the Moho and is given by:

Tm = T0 + qm h + Tr (5)

where T0 and qm correspond to the temperature at the surface and the mantle heat flux calculated at the Moho depth. Tr is the radiogenic contribution that is dependent on the thickness of the crust hc, density ρ, radiogenic production Hs, radiogenic production decay depth hr, and thermal conductivity coefficient k according to the following equation:

Tr = ρc Hs hr2 / k (1 − e −hc/hr) (6)

Details on the calculation are given in Supplementary Discussion.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_2": "The manuscript presents new U-Pb ages and clumped isotope analyses from calcite veins formed in the eastern Betics. The\ndata reveal a single or multiple fluid event(s) from 8.5 to 5 Ma, which the authors link to extension and retreating\ndelamination. In addition, single-grain alpha-ejection corrected AHe ages of apatite give ages ranging from 15.2 to 3.1 Ma.\nThe data set is interesting and the U-Pb ages of calcite veins appear to be of high quality.\nThe main goal of the paper is to test if “delamination… triggered uplift at the origin of the Messinian Salinity Crises”. The\nauthors argue that there is “insufficient temporal resolution … to allow a clear distinction between delamination, detachment\nand shortening as the main drivers of the uplift and exhumation that led to the MSC.” This may well be true, but it is not clear\nhow the authors’ data (U-Pb calcite ages of 8.5-5 Ma; AHe ages of 15.2-3.1 Ma) provide greater temporal resolution\nconcerning processes related to the origin of the Messinian salinity crises. In addition, the study only considers southern\nSpain (Betic Cordillera) and not northern Morocco, where the most ages from volcanic rocks are available and where the\ndeepest marine gateway between the Atlantic and Mediterranean was located.\nLines 249-253: “Alternatively, elevation can also be well reproduced by the upwelling of hot asthenosphere, likely with a\nfraction of melt as indicated by low S-wave velocity domain of 4.2 km.s-1 around 100 km (Figure 5a). Based on\nparametrization of shear wave velocity-temperature 51 we determine anomalously high sub-lithospheric temperatures of\n1550°C. Such a low viscous channel could easily explain the observed mean topography of 500 m around Tabernas Basin.”\nIn order to derive sufficient dynamic uplift to achieve the 500 m elevation of the Tabernas Basin, they need an\nasthenospheric temperature 1550°C. This temperature is much higher than the standard asthenospheric temperature of\n~1350°C and would require the presence of a mantle plume, for which there is no evidence. Using more realistic\ntemperatures for the asthenosphere, it is difficult to explain uplift of more than 300m. Therefore, the results of the modelling in\nthe manuscript seem unrealistic.\nLines 369-374: “It has been suggested that the transition from oceanic subduction to continental delamination was\nresponsible for the change between the pre-MSC high-K calc-alkaline, shoshonitic and ultrapotassic volcanism and the\nemplacement of the most primitive magmatic rocks, comprising the isolated emission of post-MSC Na-alkaline basalts\n(hawaiite) (2.9-2.3 Ma) 71. In contrast, we argue that the 3 Myrs gap between pre-MSC and post-MSC magmatism observed\nin eastern Betics (Figure 6) is the consequence of shortening.” Certainly, shortening (compression) could be an explanation\nfor the 3 Myrs gap between silica-saturated calc-alkaline and K-rich volcanism and the silica-undersaturated Na-rich\nvolcanism, in comparison to Morocco where there is no such significant gap in the transition. Nevertheless, the manuscript\ndoes not explain the sequence of volcanism. For example, in the model (figure 7) both the calc-alkaline and K-rich silica-\nsaturated volcanism appear to come from the metasomatized SCLM and result from lithospheric delamination, so why aren’t\nboth types of volcanism produced simultaneously? In other words, why does calc-alkaline volcanism preceed the K-rich\nvolcanism? It is also not clear why the external basins subside instead of being uplifted in conjunction with lithospheric\ndelamination. Uplift should result from removal of the dense lithospheric root, such that the overall density of the overlying\nlithosphere is lower, but also to a lesser extent due to upwelling hotter asthenospheric mantle. The Na-rich volcanism\nappears to be derived from the asthenosphere in their model. Considering that delaminating lithospheric mantle will cause\nasthenosphere to upwell in its place, why isn’t there any silica-undersaturated Na-rich volcanism during the Miocene phase\nof extension? Why does the silica-undersaturated sodic volcanism first appear with breakoff of the delaminated lithospheric\nmantle in the author’s model?\nLines 374-378: “The MSC occurs during the latest stages of continental delamination retreat and extension initiated as early\nas the EAB magmatic arc formed around 11 ± 1 Ma (Figure 7). We link the MSC to the topographic uplift caused by the\ncombination of mantle lithosphere thinning, magmatism, and mantle upwelling producing dynamic topography.” How is this\ndifferent from previous models, e.g. Duggen et al. (2003)? How have the author’s constrained the timing of these events\nbetter with their data?\nIn figure 5, there is no scale relating color to seismic velocity.", "reviewer_3": "Dear Authors,\nThank you for the opportunity to review your manuscript titled \"Tracking Lithospheric Delamination and Surface Processes\nAcross the Messinian Salinity Crisis.\" I appreciate the effort and dedication you have invested in exploring such a significant\nevent in the recent geological history of the Mediterranean.\nYour research offers substantial promise and contributes valuable insights into the complex processes associated with the\nMessinian Salinity Crisis (MSC). However, after a thorough review, I believe that the manuscript would benefit from a more\ncomprehensive discussion that considers the broader regional context, particularly the role of gateways that closed before\nthe onset of the MSC. Expanding on this aspect would greatly enhance the overall impact and clarity of your work.\nThe comments provided below are intended to guide you in refining key areas of your manuscript. Additionally, I have\nincluded several minor suggestions aimed at improving readability, consistency, and overall presentation. These\nencompass corrections for incomplete sentences, clarification of complex terms, punctuation, citation styles, and spelling\nerrors. A detailed list of these minor comments is available in the attached document.\nI believe that by addressing these suggestions, your manuscript will significantly strengthen its contribution to the field and\ncould become a pivotal reference for future studies on Sr isotope analysis and the MSC. I am confident that your continued\nefforts in revising the manuscript will result in an outstanding addition to the scientific literature.\nThank you for considering these comments. I look forward to reviewing your revised manuscript.\n\nGeneral Suggestions:\nThe team does a great job in constrained extension and retreated delamination processes\nin the Betics to the 8-5 Ma interval, overlapping with the time of the MSC, followed by\nshortening and uplift in the Betics, constrained to the Pliocene times, after the MSC. This\nis matching very well the closure of the northern gateways between the Atlantic and the\nMediterranean.\nHowever, these gateways were among the first to close, long before the MSC. At this\nstage we know that the southern, Riff gateways remained open longer, but they also closed\nsome time before the MSC, and the final gateway to closed has not yet been found,\nalthough it has been hypothesized to be in the Gibraltar area or in the Alboran. My main\nconcern is that, given the delay in the gateway closure, the discussion needs to incorporate\nthe tectonic processes in the region of these final gateways (Riff, Gibraltar, Alboran) to\nconvincedly show that indeed the MSC is triggered by long-lived lithospheric thinning\nduring delamination.\nI personally am very curious if, within a broader reconstruction, it is possible to predict\nthe area(s) likely for the latest uplift, where the last gateway could have been located.\nStructure Suggestions:\nConsider adding a conclusion section that summarizes the key findings and implications\nof the study.\nLine-by-Line Corrections and Suggestions:\nLine 18: Consider rephrasing \"is thought to have triggered\" to \"is hypothesized to have\ntriggered\" for a more formal tone.\nLine 19: Clarify what \"this scenario\" refers to. Consider rephrasing to specify that it refers to\ndelamination as the cause of uplift.\nLine 25: Consider rephrasing \"was established before\" to \"occurred prior to.\"\nLine 29: The transition to \"Introduction\" is abrupt. Consider adding a transitional sentence to\nconnect the abstract to the introduction.\nLine 34: Replace \"it also explains\" with \"and it also explains\" to improve sentence flow.\nLine 35: Rephrase \"inherently dense lithosphere\" to \"intrinsically dense lithosphere.\"\nLine 38: \"Western Mediterranean, e.g., in the Apennines 12,13 and the Betic-Rif arc\" can be\nrevised to \"Western Mediterranean, such as in the Apennines 12,13 and the Betic-Rif arc \"\nLine 46-47: Revise \"in the eastern Betics by the post-collisional mantle-derived magmas\" to\n\"in the eastern Betics through post-collisional mantle-derived magmas.\"\nLine 48: Specify which \"marine gateways\" were closed, for clarity.\nLine 50: Replace \"allegedly\" with \"reported as\" to avoid the implication of doubt without\nevidence.\nLine 51: Clarify what \"the major driver\" refers to (e.g., \"the major driver of pre-MSC uplift\").\nLine 57: Revise \"may have persisted\" to \"might have persisted\" for consistency in tense.\nLine 67: Clarify the term \"Águilas Arc\" as it is first introduced, perhaps with a brief\nexplanation.\nLine 69: Replace \"a wide zone of East-West right-lateral transtensional shearing\" with\n\"a broad zone of East-West right-lateral transtensional shear.\"\nLine 80: Revise \"is detached over of 400 km\" to \"is detached over a distance of 400 km.\"\nLine 89: The references in parentheses (e.g., \"Kleverlaan 1989; Riding et al. 1998; Haughton\n2000\") should be formatted consistently, perhaps with numbered citations to match the style\nused elsewhere.\nLine 91: Replace \"Critical unknowns are\" with \"Key unknowns include.\"\nLine 96: Consider improving the sentence for clarity and readability \"Results are compared to\nkey transitions resolved by time-temperature paths...\".\nLine 101: Consider rephrasing the following statement “allow us to better constrain the\nmechanisms responsible for the Messinian Salinity Crisis” in a manner that reflects that\n\"these age constraints enable us to more accurately identify the mechanisms that were active\nbefore and during the Messinian Salinity Crisis, likely contributing to the onset of\nMediterranean isolation.\"\nLine 118: Consider adding a brief introductory sentence before \"Carbonate U-Pb dating of\nsyn-extension fractures\" to improve the flow between sections.\nLine 159: Ensure consistency in the use of abbreviations like \"AHe\" by defining them at first\nmention.\nLine 178: Replace \"Time-temperature histories\" with \"Reconstruction of Time-Temperature\nHistories\" for clarity.\nLine 268: Consider revising the subheading \"Pre-MSC uplift and subsidence induced by\nmantle delamination\" to \"Pre-MSC Uplift and Subsidence Driven by Mantle Delamination.\"\nLine 299: The sentence beginning \"The different timing of uplift...\" could be split for clarity.\nLine 317: Clarify what \"formational water\" refers to, perhaps with a brief definition.\nLine 330: Replace \"show that these shallow crustal gradients\" with \"indicate that these\nshallow crustal gradients.\"\nLine 370: The phrase \"change between the pre-MSC high-K calc-alkaline, shoshonitic, and\nultrapotassic volcanism\" could be clearer with additional context or explanation.\nLine 391: The \"Method\" section might be better titled \"Methods\" or \"Materials and\nMethods.\"\nLine 424: Replace \"are lower intercept ages derived from\" with \"are derived from lower\nintercept ages on.\""}, "author_response": "Point-by-point responses to the reviews and editor’s comment\nReviewer#2\nThe manuscript presents new U-Pb ages and clumped isotope analyses from calcite\nveins formed in the eastern Betics. The data reveal a single or multiple fluid event(s)\nfrom 8.5 to 5 Ma, which the authors link to extension and retreating delamination. In\naddition, single-grain alpha-ejection corrected AHe ages of apatite give ages ranging\nfrom 15.2 to 3.1 Ma. The data set is interesting and the U-Pb ages of calcite veins\nappear to be of high quality.\nThe main goal of the paper is to test if “delamination… triggered uplift at the origin of\nthe Messinian Salinity Crises”. The authors argue that there is “insufficient temporal\nresolution … to allow a clear distinction between delamination, detachment and\nshortening as the main drivers of the uplift and exhumation that led to the MSC.”\nThis may well be true, but it is not clear how the authors’ data (U-Pb calcite ages\nof 8.5-5 Ma; AHe ages of 15.2-3.1 Ma) provide greater temporal resolution\nconcerning processes related to the origin of the Messinian salinity crises.\nOur new calcite U-Pb ages ranging between 8.5 and 5 Ma describe a fluid event\nassociated with extension that started before and was ongoing during the MSC. Then,\nthe thermal histories inferred from our new AHe ages reveal a regional scale cooling\nepisode at 4.5-3 Ma. When integrated with other geological data in the region\n(stratigraphic ages and depositional environments) we interpret the post-MSC 4.5-3\nMa event as due to exhumation/uplift, which we relate to the onset of shortening,\nwhich coincides with the end of extension. Shortening clearly occurred after, and\nperhaps explains how the MSC ended.\nThese data resolve for the first time in the region that the MSC occurred during\nextension in the Betics and this is associated with retreat of delaminated slab\n(as proposed independently by authors working on magmatic evolution). Therefore\nshortening is not the only process responsible for MSC as proposed earlier (see\nIntroduction). Regional shortening postdates the MSC and was likely triggered by slab\ndetachment in both the Betics and Rif. In the revised version we added details about\nthe timing of magmatism in Morocco and the closing of marine gateways.\nThe U-Pb ages of calcite in veins are as young as 5.05 ± 0.27 Ma so extension have\nlasted until the end of Messinian as the Mediterranean was dessicated and it ended\nwith onset of shortening. Ca-K magmatism associated with extension before and\nduring the MSC. Si-poor magmatism, flooding of the Mediterranean and shortening\nterminates the MSC as a result of rapid slab detachment and the migration toward\nGibraltar. We think is not made clear in the text.\nIn addition, the study only considers southern Spain (Betic Cordillera) and not northern\nMorocco, where the most ages from volcanic rocks are available and where the\ndeepest marine gateway between the Atlantic and Mediterranean was located.\nThe current database on ages of volcanic rocks comprises 41 ages (18 Ca-K, 9 High-\nK, 14 Lamproite volcanic rocks) in the Betics (plotted in Figure 6) while in Morocco\nthere are 43 ages available (Duggen et al., 2005). There is no significant difference.\nMore importantly, the transition from Ca-K series to intraplate alkali basalt relevant to\nour study ranges between 6.4 and 2.9 Ma in Spain and is between 6.6 and 4.0 Ma in\nMorocco (Duggen et al., 2005). According to our data we attribute this change to slab\ndetachment both to the north and south, and this change is reflected in the Betics by\nthe onset of shortening. In agreement we indeed think that emphasizing the\nsynchroneity of the mantle processes in Spain and Morocco strenghten our\nconclusions. We have modified the text in the revised version to include a\ncomparison with Morocco.\nLines 249-253: “Alternatively, elevation can also be well reproduced by the upwelling\nof hot asthenosphere, likely with a fraction of melt as indicated by low S-wave velocity\ndomain of 4.2 km.s-1 around 100 km (Figure 5a). Based on parametrization of shear\nwave velocity-temperature we determine anomalously high sub-lithospheric\ntemperatures of 1550°C. Such a low viscous channel could easily explain the\nobserved mean topography of 500 m around Tabernas Basin.”\nIn order to derive sufficient dynamic uplift to achieve the 500 m elevation of the\nTabernas Basin, they need an asthenospheric temperature 1550°C. This temperature\nis much higher than the standard asthenospheric temperature of ~1350°C and would\nrequire the presence of a mantle plume, for which there is no evidence. Using more\nrealistic temperatures for the asthenosphere, it is difficult to explain uplift of more than\n300m. Therefore, the results of the modelling in the manuscript seem unrealistic.\nThe temperature is a maximum and is inferred from conversion of S-wave velocities\n(SL2013sv model) to temperature using the well-established calibration of “Priestley,\nK. & McKenzie, D. The thermal structure of the lithosphere from shear wave velocities.\nEarth Planet. Sci. Lett. 244, 285–301 (2006)”. Vs are very low in the studied area and\nreveal a 150-200°C temperature anomaly. Note that this value is consistent with\ntemperature estimated at larger scale below Iberia also close to 1500°C using the\nsame approach but based on different S-wave tomographic model (Conway-Jones et\nal., 2019). See below the Figure, which is an extract from that paper. Such a sub-\nlithospheric temperature explains the dynamic support of Iberia. In conclusion, we\nconsider this temperature of 1550°C as realistic.\nNote that there is an abundant literature in the region about the temperature anomaly\nthat is considered by some authors as a related to a plume. As an example,\ntemperature independently determined in the study area in Spain and Morocco from\nthermobarometry of alkali basaltic lavas e.g. Thurner et al. (2014) cited in our study,\nestimated temperatures much higher than 1350°C , and locally above 1500°C in\nMorocco. Note that through our thermal calculation “We predict a surface heat flow of\n118 mW/m2, which agrees with the measured current heat flow of 124 mW/m2 in the\nEAB 68. Note that this value requires a high mantle heat flux of 48 mW/m2 that is 50%\nhigher than the average European mantle heat flow 48.” Our results are therefore in\nline with the thermal anomaly in the mantle.\nThurner et al. (2014) wrote “the 1400–1500°C temperatures beneath the Atlas are\nanomalously hot. High equilibration pressures suggest deep melting (60–100 km).\nThis is consistent with suggestions that hot plume material may underlie the Atlas\nMountains (Duggen et al., 2008a). Beneath the Alboran basin itself, the estimated\ntemperatures and depths of equilibration are 1350°C and 20 km, not unlike what is\nseen beneath typical mid-ocean ridges, implying a highly thinned lithosphere beneath\nthe Alboran.” See below Figure 2 of Thurner et al. (2014) indicating melting\ntemperature of Pliocene alkali basalt larger than 1500°C, which agrees with our\nestimate.\nThe presence of a plume has also been pointed out for years based on trend of low\nVs and young Plio-Pleistocene alkaline magmatism in Western Germany (Eger\nregion), Rhine graben, French Massif Central, Calatrava Volcanic Province ( 9–2 Ma)\nin central Spain , Olot–Garrotxa in Cataluna ( 10–0.01 Ma), Betics down south to\n∼\nMorocco based on velocity anomalies and. Some publications have proposed the role\n∼\nof the Acores plume (Duggen et al., 2008). Alternativley, plume-like volcanism in the\nMediterranean region has been suggested to result from shallow mantle upwelling\ntriggered by decompressional melting pockets ahead and around Ionian retreating\nslab (Faccenna et al., 2010). Occurrence of plume-related volcanism is not unknown\nalthough its role and importance are still debated. They are interpreted to indicate\nmixing of partial melts from the lithospheric and asthenospheric mantle.\nMore importantly, the reviewer seems to overlook the fact that nowhere we conclude\nthat the topography requires a plume. We only emphasize the fact that such\ntemperature anomaly likely result from mantle flow that in turn support the topography.\nThis process is proposed only to be possible: “ Such a low viscous channel could\neasily explain the observed mean topography of 500 m around Tabernas Basin (see\nMethod section and Supplementary Discussion 1).” But earlier in the text we\nindicate that we can alternatively reproduce the topography assuming mantle\ndepletion; see results of calculation shown in Figure 5b and c.\nIn this regards, we write “ The lithosphere below the eastern Betics is therefore not in\nisostatic equilibrium, unless we assume a mantle density decrease of 80-100 kg/m-3.\nStudies of rifted margins show that the formation of light mineral phases such as\nplagioclase during extension and shallowing of the lithospheric mantle can produce a\ndensity decrease of mantle rocks down to 3.2 at 60 km for temperatures above 800°C\n50. This is likely to have occurred in the Betics during Mesozoic extension as the\nlithospheric mantle was re-fertilized by tholeiitic MORB-like melts 51.” Later we\nemphasize “that compositional variations in the mantle lithosphere and\nasthenospheric upwelling likely acted together and contributed to the support of the\neastern Betic topography.” We clearly express the fact that this is a combination\nof both high mantle temperature and mantle depletion that supports the\ntopography, not a plume.\nLines 369-374: “It has been suggested that the transition from oceanic subduction to\ncontinental delamination was responsible for the change between the pre-MSC high-\nK calc-alkaline, shoshonitic and ultrapotassic volcanism and the emplacement of the\nmost primitive magmatic rocks, comprising the isolated emission of post-MSC Na-\nalkaline basalts (hawaiite) (2.9-2.3 Ma) 71. In contrast, we argue that the 3 Myrs gap\nbetween pre-MSC and post-MSC magmatism observed in eastern Betics (Figure 6) is\nthe consequence of shortening.”\nCertainly, shortening (compression) could be an explanation for the 3 Myrs gap\nbetween silica-saturated calc-alkaline and K-rich volcanism and the silica-\nundersaturated Na-rich volcanism, in comparison to Morocco where there is no such\nsignificant gap in the transition. Nevertheless, the manuscript does not explain the\nsequence of volcanism. For example, in the model (figure 7) both the calc-alkaline and\nK-rich silica-saturated volcanism appear to come from the metasomatized SCLM and\nresult from lithospheric delamination, so why aren’t both types of volcanism produced\nsimultaneously? In other words, why does calc-alkaline volcanism preceed the K-rich\nvolcanism?\nWe agree that references to ages and type of volcanism in Morocco was lacking. In\nthe discussion section of the revised version we now refer to these data to make\nthis point clearer. Data confirm that the transition from high-K, Si-rich to Si-poor\nvolcanim occurrred synchronously so the post-MSC detachment was synchronous in\nthe Betic-Rif region.\nIt is also not clear why the external basins subside instead of being uplifted in\nconjunction with lithospheric delamination. Uplift should result from removal of the\ndense lithospheric root, such that the overall density of the overlying lithosphere is\nlower, but also to a lesser extent due to upwelling hotter asthenospheric mantle.\nHere we are dealing with retreating delamination process which is different from\nclassical deblobbing model often invoked for orogenic plateau formation. In our case\ndelamination process allows compression and extension to occur at the same time\n(Central Apennines is a very nice example, see Introduction). Thus as the\ndelaminated slab retreats crustal extension occurs in the distal part of the margin (this\nextension is highly oblique in the case of the Betics) and the amount of delaminated\nlithosphere also vary. So yes the delamination leads to uplift but this is\ncompensated by crustal extension and the degree of delamination. See\ncalculation in Supplementary Discussion 1 (we take an initial lithoshere thickness of\n100 km – standard Phanerozoic lithosphere for two cases 1- thermally equilibrated; 2\nnon-thermally equilibrated). For comparision with the western margin of the Apennines\nrides below sea while less extended domains in the east are emerged.\nThe Na-rich volcanism appears to be derived from the asthenosphere in their model.\nConsidering that delaminating lithospheric mantle will cause asthenosphere to upwell\nin its place, why isn’t there any silica-undersaturated Na-rich volcanism during the\nMiocene phase of extension? Why does the silica-undersaturated sodic volcanism first\nappear with breakoff of the delaminated lithospheric mantle in the author’s model?\nDuring the first Miocene phase of retreating delamination magma come from the\nmelting of a previously metasomatized SCLM. In orther words, heating associated with\nlithospheric thinning during this first phase of delamination retreat was sufficient to\nmelt the SCLM. We write : “Evidence for delamination are brought by geochemical and\npetrological data on the mantle sources of alkaline lavas. They demonstrate that the\ntransition from calk-alkaline to high-K calc-alkaline, shoshonitic and ultrapotassic\nvolcanism is the result of variable degrees of melting of a lithospheric mantle that was\nmetasomatised by fluids prior to Paleogene collision in the Betics 68” . The silica-\nundersaturated Na-rich volcanism originated from the low-degree melting of upwelled\nsub-lithospheric mantle. We corrected the text to make this point clearer. Our model is\nsimilar to that of Duggen et al. except the initial Ca-K melting event is not related to\nthe melting of a suprasubduction mantle in our study.\nLines 374-378: “The MSC occurs during the latest stages of continental delamination\nretreat and extension initiated as early as the EAB magmatic arc formed around 11 ±\nof mantle lithosphere thinning, magmatism, and mantle upwelling producing dynamic\ntopography.” How is this different from previous models, e.g. Duggen et al. (2003)?\nThe difference is that in Duggen et al., the MSC is the consequence of delamination\nthat triggered uplift closing the marine gateways. In our model the delamination retreat\nstarted before and was ongoing during the MSC. The resulting uplift was not sufficient\nto close the Gibraltar marine gateways (see the recent literatures on the MSC). Then\nthe last slab detachment event postdates the MSC in our model but was considered\nbe the mechanism explainign the MSC by Duggen et al. We reformulated this part of\nthe conclusion to make this point clearer in the text.\nHow have the author’s constrained the timing of these events better with their data?\n1) we date extension -> related to delamination retreat, Ca-K, high-K magmatism and\nfluid events constrained by new high resolution U-Pb ages and d47 temperature of\nveins. Delamination initiated before the MSC.\nand\n2) we date the onset of compression -> based on new A(U-He) ages on Ca-K volcanic\nrocks (which is rarely possible) that are contemporaneous with detachment and onset\nof Na-rich volcanism. Slab detachment terminates the MSC.\nIn figure 5, there is no scale relating color to seismic velocity.\nThat’s right, but we think that the contours indicating the Vs speed values are sufficient\nto understand the figure. Adding a color scale would overload the figure unnecessarily.\nWe have added a description in the caption “Values of S-wave velocities are indicated\nby contour lines and interval of 0.1 km.s-1” for clarification.\nReviewer#3\nThe team does a great job in constrained extension and retreated delamination\nprocesses in the Betics to the 8-5 Ma interval, overlapping with the time of the MSC,\nfollowed by shortening and uplift in the Betics, constrained to the Pliocene times,\nafter the MSC. This is matching very well the closure of the northern gateways between\nthe Atlantic and the Mediterranean. However, these gateways were among the first to\nclose, long before the MSC. At this stage we know that the southern, Riff gateways\nremained open longer, but they also closed some time before the MSC, and the final\ngateway to closed has not yet been found, although it has been hypothesized to be in\nthe Gibraltar area or in the Alboran. My main concern is that, given the delay in the\ngateway closure, the discussion needs to incorporate the tectonic processes in the\nregion of these final gateways (Riff, Gibraltar, Alboran) to convincedly show that indeed\nthe MSC is triggered by long-lived lithospheric thinning during delamination.\nI personally am very curious if, within a broader reconstruction, it is possible to predict\nthe area(s) likely for the latest uplift, where the last gateway could have been located.\nBoth the Rifian corridor in Morocco and the Betic corridors in Spain closed before the\nMSC because of the delamination retreat that is expressed by extension in the Betics\nand shortening in the Rif. We revised the manuscript to include a description of the\ngateways. From this we infer that the Gibraltar gateway was the last connection during\nthe MSC and supplied the Mediterranean with water until the Pliocene when slab\ndetachment occurred triggering subsidence where the slab remained attached in\nGibraltar. From this time onwards, shortening and tectonic escape occurred across the\nBetic-Rif arc.\nStructure Suggestions:\nConsider adding a conclusion section that summarizes the key findings and\nimplications of the study.\nWe don’t want to make repetitions as have not much space and because we think that\nNature Communication allows to go beyond the classical structure of scientific paper.\nWe did not added a conclusion but we added a sub-section “Delamination and the\norigin and demise of the Messinian Salinity Crisis” in the discussion that emphasized\nthe relationships between the evoluton of the Betic-Rif corridors and delamination.\nLine-by-Line Corrections and Suggestions:\nLine 18: Consider rephrasing \"is thought to have triggered\" to \"is hypothesized to\nhave triggered\" for a more formal tone.\nCorrected as suggested.\nLine 19: Clarify what \"this scenario\" refers to. Consider rephrasing to specify that it\nrefers to delamination as the cause of uplift.\nCorrected as “The delamination scenario as the primary cause of uplift is questioned\ndue to the insufficient temporal resolution relative to other proposed mechanisms that\ninclude crustal shortening and slab detachment.”\nLine 25: Consider rephrasing \"was established before\" to \"occurred prior to.\"\nCorrected as suggested.\nLine 29: The transition to \"Introduction\" is abrupt. Consider adding a transitional\nsentence to connect the abstract to the introduction.\nAccording to our understanding of the structure of a typical Nature Communications\nAbstract section, it reads independently from the Introduction and by does not need a\ntransition.\nLine 34: Replace \"it also explains\" with \"and it also explains\" to improve sentence\nflow.\nCorrected as suggested.\nLine 35: Rephrase \"inherently dense lithosphere\" to \"intrinsically dense lithosphere.\"\nCorrected as suggested.\nLine 38: \"Western Mediterranean, e.g., in the Apennines 12,13 and the Betic-Rif arc\"\ncan be revised to \"Western Mediterranean, such as in the Apennines 12,13 and the\nBetic-Rif arc \"\nCorrected as suggested.\nLine 46-47: Revise \"in the eastern Betics by the post-collisional mantle-derived\nmagmas\" to \"in the eastern Betics through post-collisional mantle-derived magmas.\"\nCorrected as suggested.\nLine 48: Specify which \"marine gateways\" were closed, for clarity.\nModified as follows : “This triggered the Messinian Salinity Crisis (MSC, 5.97-5.33 Ma)\nby closing the marine gateways between the Atlantic and the Mediterranean in the\nBetic Corridor (Spain) and in the Rifian Corridor (Morocco)”\nLine 50: Replace \"allegedly\" with \"reported as\" to avoid the implication of doubt\nwithout evidence.\nCorrected as suggested.\nLine 51: Clarify what \"the major driver\" refers to (e.g., \"the major driver of pre-MSC\nuplift\").\nWe have rephrased the sentence as “Delamination is however not the unique\nmechanism invoked for pre-MSC uplift of the Betics, as it is synchronous with the onset\nof shortening presented as the major driver of pre-MSC late Tortonian (<7.8-7.3 Ma)\nuplift.”\nLine 57: Revise \"may have persisted\" to \"might have persisted\" for consistency in\ntense.\nCorrected as suggested.\nLine 67: Clarify the term \"Águilas Arc\" as it is first introduced, perhaps with a brief\nexplanation.\nCorrected as : “rotated and sheared units of the Alboran basement in the Águilas\nArc”\nLine 69: Replace \"a wide zone of East-West right-lateral transtensional shearing\"\nwith \"a broad zone of East-West right-lateral transtensional shear.\"\nCorrected as suggested\nLine 80: Revise \"is detached over of 400 km\" to \"is detached over a distance of 400\nkm.\"\nCorrected as suggested\nLine 89: The references in parentheses (e.g., \"Kleverlaan 1989; Riding et al. 1998;\nHaughton 2000\") should be formatted consistently, perhaps with numbered citations\nto match the style used elsewhere.\nRight. We replaced these references with one (reference 33 already cited) in which\nthese main results are summarized.\nLine 91: Replace \"Critical unknowns are\" with \"Key unknowns include.\"\nCorrected as suggested.\nLine 96: Consider improving the sentence for clarity and readability \"Results are\ncompared to key transitions resolved by time-temperature paths...\".\nWe improved the sentence as follows : “Results are compared to key transitions\nresolved by the analysis of the cooling evolution of the CGVP and the continental\nbasement using apatite (U-Th-Sm)/He (AHe) thermochronology.”\nLine 101: Consider rephrasing the following statement “allow us to better constrain\nthe mechanisms responsible for the Messinian Salinity Crisis” in a manner that\nreflects that \"these age constraints enable us to more accurately identify the\nmechanisms that were active before and during the Messinian Salinity Crisis, likely\ncontributing to the onset of Mediterranean isolation.\"\nCorrected as suggested.\nLine 118: Consider adding a brief introductory sentence before \"Carbonate U-Pb\ndating of syn-extension fractures\" to improve the flow between sections.\nAccording to our understanding, the style of writing in Nature Communications paper\nis expected to be straightforward, so we think an introductory sentence is not required\nin the Results section.\nLine 159: Ensure consistency in the use of abbreviations like \"AHe\" by defining them\nat first mention.\nThe reviewer probably missed by this is indicated earlier in the text.\nLine 178: Replace \"Time-temperature histories\" with \"Reconstruction of Time-\nTemperature Histories\" for clarity.\nCorrected as suggested.\nLine 268: Consider revising the subheading \"Pre-MSC uplift and subsidence\ninduced by mantle delamination\" to \"Pre-MSC Uplift and Subsidence Driven by\nMantle Delamination.\"\nCorrected as suggested.\nLine 299: The sentence beginning \"The different timing of uplift...\" could be split for\nclarity.\nWe think the original sentence “The different timing of uplift between internal (8-7.5\nMa) and external basins (post-5 Ma) is significant and has acted at different scales.”\nis short and clear enough.\nLine 317: Clarify what \"formational water\" refers to, perhaps with a brief definition.\nAgreed. We have modified the sentence as follows : “involved a component of\nformational water (i.e. fluids trapped in the sediment during its deposition and\nlithification).”\nLine 330: Replace \"show that these shallow crustal gradients\" with \"indicate that\nthese shallow crustal gradients.\"\nCorrected as suggested.\nLine 370: The phrase \"change between the pre-MSC high-K calc-alkaline,\nshoshonitic, and ultrapotassic volcanism\" could be clearer with additional context or\nexplanation.\nCorrected as suggested.\nLine 391: The \"Method\" section might be better titled \"Methods\" or \"Materials and\nMethods.\"\nCorrected to Methods.\nLine 424: Replace \"are lower intercept ages derived from\" with \"are derived from\nlower intercept ages on.\"\nCorrected as suggested.\nPoint-by-point responses to the reviews and editor’s comment\nReviewer #3 (Remarks to the Author)\nDear Authors,\nI have reviewed the revised version of your manuscript titled \"Tracking lithospheric\ndelamination and surface processes across the Messinian salinity crisis.\" I am pleased\nto see that you have thoroughly addressed all the aspects I had previously signaled in\nmy review.\nI am satisfied with the current state of the manuscript and have no additional\ncomments or suggestions. Best wishes for the next steps in the publication process.\nThank you !\nReviewer #4 (Remarks to the Author\nThis manuscript presents new U-Pb ages and clumped isotope analyses from calcite\nveins formed in an intramontane basin (Tabernas Basin) of the external eastern Betics.\nThey reveal a short-lived fluid event from 8.5 to 5 Ma, which the authors link to\nextension and retreating delamination. The onset of shortening, coinciding with\nexhumation and uplift, is dated at 4.5-3 Ma, so post-dating the MSC (5.97-5.33 Ma).\nThe slab detachment-uplift event is therefore considered NOT to be the cause of the\nMSC as was previously proposed by Duggen et al. (2005). In the new tectonic model\nproposed here, the delamination retreat started before and was ongoing during the\nMSC, and the resulting uplift was not sufficient to close the final Atlantic gateway. What\ndoes remain, however, is the conclusion that the delamination process triggered\nsynchronous uplift of the internal basins that closed the marine gateway of the Betic\nCorridor in the late Tortonian. This can be seen as a first step towards Mediterranean\nisolation from the Atlantic. The external basins (e.g. Tabernas) are then probably not\npart of the early Messinian gateway system, and both reviewers correctly pointed out\nthat the Moroccan gateway should be discussed as well. I think the authors did a\nproper job modifying the manuscript by incorporating data from Morocco, which seem\nto indicate synchronous mantle processes in Spain and Morocco. While the\nmanuscript does not provide a clear tectonic solution for the onset of the MSC, it does\npresent an interesting and welcome new geodynamic reconstruction for the tectonic\nevolution of the eastern Betics.\nTrue, we demonstrate that slab-detachment is not the trigger of the MSC, and this is\na major result since this process is the most popular in the literature. We propose that\n“…the uplift of this marine corridor caused by lithospheric delamination and\nmagmatism.”\nIn conclusion, both the 8.5-5 Ma extension processes and the tectonic shortening\nprocesses at 4.5 Ma apparently cannot explain the onset of the MSC. I think the\nmanuscript could still be improved by accepting/explaining in a couple of sentences\nthat additional processes (e.g. global sea level lowering, regional climate forcing) are\nalso considered to play a role at the MSC onset (see our recent review (Krijgsman et\nal., 2024) for details). This to highlight that geodynamic processes certainly play a\nmajor role in the Gibraltar region, but that a fully integrated picture including multiple\nforcing factors is likely required to understand such a highly debated feature as the\nMSC.\nReference:\nKrijgsman, W., Rohling, E.J., Palcu, D.V., Raad, F., Amarathunga, U., Flecker, R.,\nFlorindo, F., Roberts, A.P., Sierro, F.J., Aloisi, G. (2024). Causes and consequences of\nthe Messinian salinity crisis. Nature Reviews Earth & Environment, 5, 335-\n350, https://doi.org/10.1038/s43017-024-00533-1\nI have modified the final paragraphe to include a sentence in which the role of other\nfactor are likley responsible for the onset of the MSC, referring to the recent paper of\nKrijgsman et al.\n“We link the MSC to the progressive uplift of this marine corridor caused by a\ncombination of lithospheric delamination and magmatism. This model agrees with the\noccurrence of an Alboran volcanic archipelago that permitted faunal exchanges before\nand after the MSC 28. While the role of geodynamic processes in the Gibraltar region\nis central, the onset of the MSC further indicates the additional impact of global sea-\nlevel lowering and paleoclimate78.”"}, {"round": 2, "reviewer_comments": {"reviewer_3": "Dear Authors,\nI have reviewed the revised version of your manuscript titled \"Tracking lithospheric\ndelamination and surface processes across the Messinian salinity crisis.\" I am pleased\nto see that you have thoroughly addressed all the aspects I had previously signaled in\nmy review.\nI am satisfied with the current state of the manuscript and have no additional\ncomments or suggestions. Best wishes for the next steps in the publication process.", "reviewer_4": "This manuscript presents new U-Pb ages and clumped isotope analyses from calcite veins formed in an intramontane basin (Tabernas Basin) of the external eastern Betics. They reveal a short-lived fluid event from 8.5 to 5 Ma, which the authors link to extension and retreating delamination. The onset of shortening, coinciding with exhumation and uplift, is dated at 4.5-3 Ma, so post-dating the MSC (5.97-5.33 Ma). The slab detachment-uplift event is therefore considered NOT to be the cause of the MSC as was previously proposed by Duggen et al. (2005). In the new tectonic model proposed here, the delamination retreat started before and was ongoing during the MSC, and the resulting uplift was not sufficient to close the final Atlantic gateway. What does remain, however, is the conclusion that the delamination process triggered synchronous uplift of the internal basins that closed the marine gateway of the Betic Corridor in the late Tortonian. This can be seen as a first step towards Mediterranean isolation from the Atlantic. The external basins (e.g. Tabernas) are then probably not part of the early Messinian gateway system, and both reviewers correctly pointed out that the Moroccan gateway should be discussed as well. I think the authors did a proper job modifying the manuscript by incorporating data from Morocco, which seem to indicate synchronous mantle processes in Spain and Morocco. While the manuscript does not provide a clear tectonic solution for the onset of the MSC, it does present an interesting and welcome new geodynamic reconstruction for the tectonic evolution of the eastern Betics.\nIn conclusion, both the 8.5-5 Ma extension processes and the tectonic shortening processes at 4.5 Ma apparently cannot explain the onset of the MSC. I think the manuscript could still be improved by accepting/explaining in a couple of sentences that additional processes (e.g. global sea level lowering, regional climate forcing) are also considered to play a role at the MSC onset (see our recent review (Krijgsman et al., 2024) for details). This to highlight that geodynamic processes certainly play a major role in the Gibraltar region, but that a fully integrated picture including multiple forcing factors is likely required to understand such a highly debated feature as the MSC.\nReference:\nKrijgsman, W., Rohling, E.J., Palcu, D.V., Raad, F., Amarathunga, U., Flecker, R., Florindo, F., Roberts, A.P., Sierro, F.J., Aloisi, G. (2024). Causes and consequences of the Messinian salinity crisis. Nature Reviews Earth & Environment, 5, 335-\n350, https://doi.org/10.1038/s43017-024-00533-1"}, "author_response": "True, we demonstrate that slab-detachment is not the trigger of the MSC, and this is\na major result since this process is the most popular in the literature. We propose that\n“…the uplift of this marine corridor caused by lithospheric delamination and\nmagmatism.”\nIn conclusion, both the 8.5-5 Ma extension processes and the tectonic shortening\nprocesses at 4.5 Ma apparently cannot explain the onset of the MSC. I think the\nmanuscript could still be improved by accepting/explaining in a couple of sentences\nthat additional processes (e.g. global sea level lowering, regional climate forcing) are\nalso considered to play a role at the MSC onset (see our recent review (Krijgsman et\nal., 2024) for details). This to highlight that geodynamic processes certainly play a\nmajor role in the Gibraltar region, but that a fully integrated picture including multiple\nforcing factors is likely required to understand such a highly debated feature as the\nMSC.\nReference:\nKrijgsman, W., Rohling, E.J., Palcu, D.V., Raad, F., Amarathunga, U., Flecker, R.,\nFlorindo, F., Roberts, A.P., Sierro, F.J., Aloisi, G. (2024). Causes and consequences of\nthe Messinian salinity crisis. Nature Reviews Earth & Environment, 5, 335-\n350, https://doi.org/10.1038/s43017-024-00533-1\nI have modified the final paragraphe to include a sentence in which the role of other\nfactor are likley responsible for the onset of the MSC, referring to the recent paper of\nKrijgsman et al.\n“We link the MSC to the progressive uplift of this marine corridor caused by a\ncombination of lithospheric delamination and magmatism. This model agrees with the\noccurrence of an Alboran volcanic archipelago that permitted faunal exchanges before\nand after the MSC 28. While the role of geodynamic processes in the Gibraltar region\nis central, the onset of the MSC further indicates the additional impact of global sea-\nlevel lowering and paleoclimate78.”"}]

Decision letter