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The Bajgan Complex in the North Makran Domain (Makran Accretionary Prism) comprises disrupted meta-ophiolitic sequences originating from oceanic crust protoliths. They include ultramafic and mafic cumulates, isotropic gabbros, plagiogranites and basalts. Ultramafic–mafic cumulates and plagiogranites exhibit compositions akin to rocks formed in mid-ocean ridge settings. Isotropic gabbro and basalt protoliths can be subdivided into three distinct geochemical types. Type-1 rocks are sub-alkaline (Nb/Y < 0.1) with low Th, Nb and Ta contents and LaN/YbN ratios <1, resembling those of normal mid-ocean ridge basalts (N-MORB). Type-2 rocks display slight enrichment in Th, Ta, Nb (Nb/Y = 0.36–0.45) and LaN/YbN = 2.12–3.20, resembling the chemistry of enriched (E-) MORB. Type-3 basalts show an alkaline nature (Nb/Y = 0.88–1.82), significant Th, Ta and Nb enrichment, and high LaN/YbN ratios (7.01–20.08), resembling the chemistry of alkaline basalts (ocean island basalts, OIB). Petrogenetic modelling indicates that N-MORB protoliths originated from a depleted MORB mantle source, whereas E-MORB and OIB protoliths were generated from partial melting of sub-oceanic depleted sources that underwent varying degrees of OIB-type enrichment. The Bajgan meta-ophiolitic protoliths were formed within a Late Jurassic to Cretaceous oceanic basin influenced by mantle plume activity and plume–ridge interaction. Supplementary material: Field photographs, micrographs, rocks sampled, analytical methods and results, and supplementary tables are available at https://doi.org/10.6084/m9.figshare.c.7193937 Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists [ABSTRACT FROM AUTHOR]

We have investigated the geology, geochemistry and geochronology of various plagiogranite intrusions that are spatially associated with ophiolitic subunits in a mélange terrain exposed within the Nain–Baft fault zone along the western boundary of the Central–East Iranian Microcontinent (CEIM). One group of plagiogranites is intrusive into foliated amphibolites, whereas the plagiogranites of the other group are intrusive into gabbros, dyke swarms and pillow lavas that are tectonically juxtaposed. U–Pb zircon dating of the first group of plagiogranites has revealed near-concordant crystallization ages of 176.94 ± 0.71, 179.84 ± 0.92 and 190.40 ± 2.1 Ma, indicating the early Jurassic timing of their emplacement. U–Pb zircon dating of the second group of plagiogranites has revealed a weighted average age of 92.34 ± 0.38 Ma, indicating that they were emplaced in the early Late Cretaceous. The Early Jurassic plagiogranites are low-K, sub-alkaline rocks with negative Eu anomalies, low Ti and high La and Ce contents. They display elevated ratios of large ion lithophile elements to high field strength elements. They were part of a magmatic system that facilitated the earliest rift–drift stages of a Neotethyan seaway development, and their magmas were produced by fractional crystallization of a mafic melt associated with asthenospheric upwelling beneath a rift system. The Late Cretaceous plagiogranites are low-K, sub-alkaline rocks with negative Eu anomalies, high Y and low Ta contents. They show light REE depletion relative to flat heavy REE patterns, and high Ba/Th ratios. Magmas of these plagiogranites were the products of partial melting of amphibolites in the subducting oceanic lithosphere in the same Neotethyan seaway. Thus, we posit that plagiogranite rocks in suture zones can be excellent trackers of geochemical, geochronological and magmatic evolution of various types of oceanic crust through rift–drift, seafloor spreading and subduction initiation stages within the same ocean basins in the past. Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists [ABSTRACT FROM AUTHOR]

Remnants of coeval Devonian oceanic and continental foreland rocks are preserved in the basement of the North Patagonian Andes. Our previous studies of the igneous rocks here have shown that the primitive oceanic and continental igneous rocks are coeval and belong to a marginal basin that opened and closed over 50 Myr. A structural study and four new U–Pb SHRIMP ages and zircon Hf–O determinations allowed the identification of three metamorphic episodes, the first one of which, M1(D1-S1), is coeval with Andean-type granite intrusion in the foreland (405–380 Ma). This activity was simultaneous with the development of an oceanic ridge and a marginal basin, at the outer edge of which a primitive granitic oceanic arc formed (380–385 Ma; zircon δ 18O 3.6–5.2‰). The extinction of this ridge initiated under-thrusting of the oceanic crust below the continent and an important mid- to high-grade metamorphic event, M2(D2-S2) at 375–360 Ma, its peak dated by metamorphic zircon rims in migmatite at 365 ± 3 Ma. Basin closure occurred after the intrusion of S-type granites (357 ± 2 Ma; zircon δ 18O 7.4–10.4‰) in the foreland and the accretion of gabbros, cumulate gabbros and trondhjemites at the proto-Pacific margin. Compression prevailed for 20 Myr in the foreland, causing a mylonitic medium-grade M3(D3-S3) event. Supplementary material: Datasets are available at https://doi.org/10.6084/m9.figshare.c.6989873 [ABSTRACT FROM AUTHOR]

Ophiolite obduction, the process during which part of the oceanic crust overlaps the continental margin, presents a challenge in geodynamic reconstructions of lithospheric processes. The difference in buoyancy between the dense oceanic crust and the relatively buoyant continental crust makes obduction of the oceanic crust difficult, if not impossible, if we only consider the buoyancy forces. The initial configuration of the oceanic basins must have specific thermal and geometric constraints to overcome the difficulties posed by the negative buoyancy. Here, we present a systematic investigation of the geometric and geodynamic parameters controlling the process of ophiolite emplacement. We show which parameters are the most important during ophiolite emplacement and the optimum geometries favouring this emplacement. We focus on 'Tethyan' ophiolites, which are characterized by a relatively small inferred basin size and are commonly found in the Mediterranean region. Based on a combination of parameters, we identify the configurations most susceptible to ophiolite obduction. Our models, in agreement with the geological data, show that to achieve ophiolite obduction, the obducted lithosphere must be young and the length of the ocean–continent transition zone must be relatively sharp. Supplementary material: Supplementary figures S1–S5, that are mentioned in the main text, are available at https://doi.org/10.6084/m9.figshare.c.6922526 Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists [ABSTRACT FROM AUTHOR]

Chemostratigraphy of lavas in extrusive sequences of modern and ancient forearc environments provides significant information on oceanic crust formation through progressive stages of melt evolution from subduction initiation magmatism (SIM) to arc infancy, and arc maturation-related magmatism. We present here new trace element and radiogenic Sr–Nd–Pb isotopic data from a Late Cretaceous ophiolite in the Outer Zagros Belt of southern Iran and discuss its magmatic development through SIM in a Neotethyan forearc setting. Initial volcanism produced the stratigraphically oldest boninitic (BON) lavas in the Haji-Abad ophiolite whose trace element ratios as well as Pb isotopic signatures indicate a refractory mantle source, which was contaminated by subducting slab-derived fluids. The BON lavas change structurally upwards into island-arc tholeiitic (IAT) lavas and their fractionated felsic derivatives that display isotopic evidence for the contribution of sediment-derived melts in their magmatic source(s). This melt evolution pattern of the Haji-Abad ophiolite marks a major difference from the progressive melt evolution trends reported from the Izu–Bonin–Mariana (IBM) forearc lava sequence, which starts at the bottom with forearc basalts (FAB) phasing up-section into BON and IAT affinity lavas. IAT lavas in the IBM are in turn overlain by calc-alkaline (CAL) lavas. Our geochemical modelling points to a probable existence of a less depleted, pre-subduction mantle whose partial melting probably generated primary magmas before the eruption of boninitic lavas, although the record of such magmas is missing in the Haji-Abad ophiolite. Our comparison of the chemostratigraphy of the Outer Zagros ophiolites with the documented record of subduction initiation generated volcanic rocks in the other Neotethyan ophiolites in the region and the IBM forearc setting strongly suggests that there is no single rule or template for SIM. Supplementary material: Details of analytical procedures and supplementary figures and tables are available at https://doi.org/10.6084/m9.figshare.c.6837597 Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists [ABSTRACT FROM AUTHOR]

The Band-e-Zeyarat ophiolite (BEZO) sedimentary cover in the Makran Accretionary Prism (SE Iran) records a complex tectono-sedimentary evolution, extending from its formation at a mid-ocean ridge (MOR) setting to deformation in an accretionary prism. Stratigraphic and biostratigraphic data indicate the occurrence of a Valanginian transition zone sequence separating the volcanic sequence and pelagic sedimentary cover. The latter consists of lower Hauterivian cherty limestone passing upwards to upper Hauterivian–Barremian marl and limestone. The pelagic sedimentary cover continues with post-Barremian–Cenomanian (?) marls. Arenites are interlayered in the sedimentary cover; they are composed of rock fragments derived from volcanic-arc and continental margin settings. The BEZO sedimentary cover is intruded by dykes and sills showing enriched MOR basalt chemical affinity. Structural analysis indicates a polyphase deformation history that involved faulting and folding. Our multidisciplinary results indicate that the BEZO formed in a MOR setting and that it was subsequently overprinted by off-axis and within-plate magmatism as it spread away from this MOR. The Band-e-Zeyarat oceanic crust was incorporated into the Makran prism in the latest Late Cretaceous–Paleocene and was further deformed via strike-slip faulting along the dextral Minab-Sabzevaran fault during the Miocene–Pliocene. Supplementary material: A geological sketch map of the Band-e-Zeyarat ophiolite, photomicrographs of arenites, microphotographs of selected calcareous nannofossil taxa, a geochemical discrimination diagram, a table with semiquantitative estimation of calcareous nannofossil abundance, and a text with detailed descriptions of analytical methods, accurancy, and detection limits for whole-rock geochemical analysis are available at https://doi.org/10.6084/m9.figshare.c.6843835 Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists [ABSTRACT FROM AUTHOR]

Fluids are important media for elemental cycling in subduction zones, but the compositions of such fluids remain obscure, especially those derived from dehydration of serpentinite. To better understand the role of subduction-zone fluids in arc magmatism of the Chinese Eastern Tianshan (CET), we present Mg and B isotopic data for the arc diorites (e.g. Kalatage and Nanshankou). Our results show that the Kalatage diorites have higher δ 26Mg (−0.23 to −0.13‰) and δ 11B (−0.04 to +1.08‰) values than the corresponding mantle values, whereas the Nanshankou diorites display relatively lower δ 26Mg (−0.26 to −0.19‰) and δ 11B (−10.7 to −2.97‰) values. Because high-temperature magmatic and post-magmatic processes have limited effects on Mg and B isotope fractionation of our samples, their distinct Mg–B isotopic signatures inherited from the mantle sources should be caused by subduction-related metasomatism. Because neither altered oceanic crust (AOC) directly melting nor the incorporation of subducted sediments could induce significant Mg–B isotope fractionation in these rocks, we infer that their variable δ 26Mg and δ 11B values were probably associated with subduction fluids that were derived from different sources. Specifically, dehydrated fluids from serpentinites possess high δ 26Mg and δ 11B values, which resulted in the heavy Mg–B isotopic compositions of the Kalatage diorites, whereas mantle metasomatized by fluids from AOC and subducted sediments were responsible for the Nanshankou rocks with relatively low δ 26Mg and δ 11B values. Taking into account the different effects of serpentinite-derived and slab-derived fluids in the formation of arc magmatism, subduction-zone fluids can be probably an important factor in changing the Mg–B isotope composition of mantle sources. Supplementary material: Supplementary data tables and parameters used in models are available at https://doi.org/10.6084/m9.figshare.c.6702686 [ABSTRACT FROM AUTHOR]

The formation of oceanic crust in the southern and central Red Sea is generally accepted to have started at c. 5 Ma. However, the nature of the crust in the northern Red Sea is still debated. This paper describes the rift architecture, dynamics and evolution of the northern Red Sea and identifies domains that relate to first-order geodynamic processes. The proximal margin domain is located onshore and is characterized by latest Oligocene–Miocene half-graben basins. New seismic interpretations show that the offshore region is a necking domain dominated by low-angle, high-offset extensional faults, which led to the exhumation of lower crustal gabbros at Brothers Islands. Two-dimensional forward models suggest that the necking domain passes into a distal margin domain, where the continental crust thins to <10 km at 120 km from the coast. Sensitivity testing of interpretations for the distal domain indicates a probable scenario where exhumed lower continental crust or serpentinized mantle is present. A comprehensive rift model for the northern Red Sea in the Quseir province accounts for magmatic underplating accompanied by half-graben development at c. 25 Ma, followed by Early Miocene crustal thinning accommodated by an east-dipping detachment fault. A Late Miocene phase with a flip of the detachment geometry led to the present day configuration. [ABSTRACT FROM AUTHOR]

One of the fundamental questions about Earth processes that is still outstanding is how far a moving plate can drag plume material at its base after its initial impact with the plume. The IODP-362 Expedition recovered igneous samples from drilled sites near Ninetyeast Ridge (NER) in the Indian Ocean. A detailed geochemical and isotopic (Sr–Nd) investigation of these samples found that the basement basalts of the core are typical N-MORB tholeiites, but the igneous sills intruding the upper layer of sediments are highly alkaline, with a composition equivalent to the Kerguelen plume magma. Based on biostratigraphy, the minimum age of the alkaline samples was calculated as c. 58 Ma, which is younger than the adjacent NER crust (c. 82–78 Ma). The existence of such young plume magma amidst the older blocks of the NER is unusual and contrary to its southwards-younging age pattern. We propose that the fast-moving Indian plate dragged a considerable amount of Kerguelen plume material underneath the Indian Ocean lithosphere northwards during the Cretaceous–Paleocene, covering a longitudinal distance of c. 2220 km. The reactivation of deep fractures triggered decompression melting of the underlying plume material and emplaced this as magmatic sills and lava flows near the NER at c. 58 Ma. [ABSTRACT FROM AUTHOR]

Aseismic ridges and oceanic plateaux, typically buried under thick post-rift sediments, are isolated entities of enigmatic crustal character. Limited availability of deep seismic soundings hinders their precise characterization. Here, we present new crustal images from the Comorin ridge and adjoining basins in the Central Indian Ocean. Further, we seismically characterize the oldest oceanic crust south of Sri Lanka. We observe that the NW–SE-trending Comorin ridge, having distinct topography, is bounded by crustal blocks of contrasting ages and characters. Using seismic interpretation and potential field modelling, we propose its genesis as a transverse ridge with an anomalously thick (c. 14 km) oceanic crust including considerable magmatic underplating. Additional constraints from plate reconstruction modelling suggest that a linear oceanic transform developed between India and Madagascar during their separation while the Marion hotspot remained in their close proximity. Based on several lines of evidence, we infer that shearing motion along the transform and coeval hotspot interactions are the likely emplacement mechanism for the ridge. The high-resolution seismic images demonstrate widespread crustal deformation in the form of high-angle faulting and long-wavelength folding. New findings have important implications for an improved understanding of the early Gondwana break-up, seafloor creation and subsequent compressional tectonics in the Indian Ocean. Supplementary material: Supplementary figures and tables are available at https://doi.org/10.6084/m9.figshare.c.6073139 [ABSTRACT FROM AUTHOR]

The South China Block underwent a tectonic switch from compression to extension between the Late Jurassic and Early Cretaceous, but the extension process has not been well understood. Here we report that the Meiziwo lamprophyres in northern Guangdong, formed in the Early Cretaceous (c. 136 Ma; 40Ar/39Ar dating), are characterized by ocean-island basalt (OIB)-like geochemical signatures and Pb enrichment, together with moderately high (87Sr/86Sr)i (0.70642–0.70766), positive ε Nd(t) (+4.6 to +5.1) and intermediate (206Pb/204Pb)i (18.579–18.602), (207Pb/204Pb)i (15.727–15.733) and (208Pb/204Pb)i (38.871–38.909). The lamprophyres were derived from an asthenosphere-dominated source, with contributions from recycled oceanic crust and terrigenous sediments. In contrast, the previously reported c. 154 Ma mafic dyke in eastern Guangdong and the c. 165–155 Ma A-type granite belt in southern Hunan and nearby regions show arc-like signatures and unradiogenic Nd but moderately radiogenic Pb isotopes, suggesting magma derivation from a lithospheric mantle. Hence, the change from lithospheric to asthenospheric sources may be caused by progressive lithospheric extension and thinning associated with the rollback and tearing of the palaeo-Pacific plate. The 136 Ma Meiziwo lamprophyres, together with the 140 Ma asthenosphere-derived OIB-like mafic rocks nearby, signify the petrological response to regional extension in the South China Block from c. 140 Ma onward. Supplementary material: Tables S1–S3 and Figures S1–S4 are available at https://doi.org/10.6084/m9.figshare.c.5953720 [ABSTRACT FROM AUTHOR]

Magnetic stripes have long been assumed to be indicative of oceanic crust. However, continental crust heavily intruded by magma can also record magnetic stripes. We re-evaluate the nature of the Cuvier Abyssal Plain (CAP), offshore NW Australia, which hosts magnetic stripes and has previously been defined as oceanic crust. We show that chemical data from a basalt within the CAP, previously described as an enriched mid-ocean ridge basalt, could equally be interpreted to contain evidence of contamination by continental material. We also recognize seaward-dipping reflector sequences in seismic reflection data across the CAP. Borehole data from overlying sedimentary rocks suggests that these seaward-dipping reflectors were emplaced in a shallow water (<200 m depth) or subaerial environment. Our results indicate that the CAP may not be unambiguous oceanic crust, but may instead consist of a spectrum of heavily intruded continental crust through to fully oceanic crust. If the CAP represents such a continent–ocean transition zone, then the adjacent unambiguous oceanic crust would be located >500 km further offshore NW Australia than currently thought. This would impact plate tectonic reconstructions, as well as heat flow and basin modelling studies. Our work also supports the growing consensus that magnetic stripes cannot, by themselves, be used to determine crustal affinity. Supplementary material: Enlarged and uninterpreted versions of the magnetic data and seismic reflection lines are available at https://doi.org/10.6084/m9.figshare.c.5332172 [ABSTRACT FROM AUTHOR]

In the Northern Apennine (Italy), the Internal Ligurian Units consist of Middle–Late Jurassic ophiolites covered by thick sedimentary deposits whose top is represented by the Early Paleocene Bocco Shale. This formation is characterized by mass-transport deposits interlayered with thin-bedded siliciclastic turbidites. The sedimentological and structural features of these mass-transport deposits reveal a long-lived history of recycling of heterogeneous material in a subduction setting. This history started with the frontal accretion of a fragment of oceanic crust into an accretionary prism whose lower slope was subsequently affected by tectonic erosion and consequent instability, leading to the production of mass-transport deposits and the transfer of material to the lower plate. These mass-transport deposits were subsequently underthrust and then again transferred to the base of the accretionary prism by coherent underplating, before their exhumation to the surface. The Bocco Shale is thus representative of a subduction setting where both accretionary and erosive events occurred, depending on changing boundary conditions. The reconstructed history for the Bocco Shale indicates that the sedimentary and gravitational processes both at the prism front and on the prism slope, possibly induced by alternating accretion and erosion events, are the most efficient mechanisms of lithological mixing and recycling in subduction margins. [ABSTRACT FROM AUTHOR]

The late Cretaceous accretionary complex along the İzmir–Ankara–Erzincan suture zone, northern Turkey, includes various types of metamorphic rock together with radiolarite, sandstone, mudstone, serpentinite, basalt and limestone. Meta-plagiogranite blocks (up to 5 m in diameter) and a meta-gabbro slice (800 × 500 m) cross-cut by meta-plagiogranite are observed in a matrix of serpentinite, mudstone and radiolarian chert. These meta-gabbros and meta-plagiogranites show subduction-related geochemical characteristics. Laser ablation inductively coupled plasma mass spectrometry U–Pb dating of zircons from two meta-plagiogranites yielded 222.3 ± 1.5 and 227.2 ± 1.6 Ma crystallization ages. This study shows that the meta-gabbro and meta-plagiogranite from the accretionary complex are remnants of the metamorphosed equivalents of the late Triassic lower crustal rocks of the subducted Tethyan oceanic crust. They are the oldest lower crustal rocks observed in the İzmir–Ankara–Erzincan suture zone. Both the meta-gabbros and meta-plagiogranites have Na–Ca amphiboles, indicating blueschist facies metamorphism. However, phengites from a blueschist facies rock yielded an 40Ar/39Ar age of 104.3 ± 0.7 Ma, indicating that blueschist metamorphism occurred during the Albian. All these data suggest that the oceanic crust formed during the Norian, metamorphosed during the Jurassic to early Cretaceous and then dismembered during accretionary complex formation in the late Cretaceous. Supplementary material: A complete description of the analytical methods (electron microprobe, LA-ICP-MS zircon U–Pb and 40Ar/39Ar age analyses, pseudo-section modelling and THERMOCALC) are available at https://doi.org/10.6084/m9.figshare.6509984 Thematic collection: This article is part of the 'Tethyan ophiolites and Tethyan seaways collection' available at: https://www.lyellcollection.org/cc/tethyan-ophiolites-and-tethyan-seaways [ABSTRACT FROM AUTHOR]

The break-up of continents at magma-poor rifted margins is a complex yet little understood process accounting for intricate interactions between tectonic and magmatic processes. Whereas high-resolution seismic data may resolve the firstorder architecture of ocean-continent transitions (OCTs), direct access to rocks remains limited to deep-sea drilling. In this study, we combine seismic observations from the East Antarctica margin (Geoscience Australia Survey 228) with field observations from the Bracco-Levanto area (Northern Apennines, Italy), representing modern and fossil examples of ultradistal magma-poor rifted margins respectively. The combination of detailed structural mapping and petrological studies from fossil examples with architectural features observed in seismic sections from present-day OCTs enables to bridge the different observation scales. Field evidence indicates that the magmatic budget is not zero, as magma is present throughout the exhumation process. Extensional detachment faults that exhumed serpentinized mantle and deep-seated gabbro intrusions are truncated by later high-angle normal faults, which most probably acted as feeders for the emplacement of massive synextensional basalts. These observations suggest a polyphase tectonic and magmatic evolution of the ultra-distal margin prior to the formation of the first true oceanic crust, which can be studied in detail only by combining seismic and outcrop observations. [ABSTRACT FROM AUTHOR]

The crust and mantle both in ophiolites (fossil ocean lithosphere) and in modern oceans are enormously diverse. Along-axis morphology and lower crustal accretion at ultraslow-spreading ocean ridges are fundamentally different from those at faster-spreading ridges, and are critical to understanding how crustal accretion varies with spreading rate and magma supply. Ultraslow-spreading ridges provide analogues for ophiolites, to identify those that may have formed under similar conditions. Parallel studies of modern ocean lithosphere and ophiolites therefore can uniquely inform the origin and genesis of both. Here we report the results of structural and petrological studies on the Xigaze ophiolite in the Tibetan Plateau, and compare it with the morphology and deep drilling results at the ultraslow-spreading Southwest Indian Ridge. The Xigaze ophiolite has a complete but laterally discontinuous crust, with discrete diabase dykes and sills cutting both mantle and lower crust. The gabbro units are thin (c. 350 m) and show upward cyclic chemical variations, supporting for an episodic and intermittent magma supply. These features are comparable with the highly focused magmatism and low magma budget at modern ultraslow-spreading ridges. Thus we suggest that the Xigaze ophiolite represents an on-land analogue of ultraslow-spreading ocean lithosphere. Supplementary material: Single-spot analysis and average compositions for mineral major element compositions (wt.%) of the Jiding gabbro section, Xigaze ophiolite are available at https://doi.org/10.17632/dtzpmwkscp.1 [ABSTRACT FROM AUTHOR]

An extensive grid of 2D seismic reflection data imaging the non-volcanic continental margin of SW Iberia is used to investigate the post-rift compressional evolution in the transition zone between continental and oceanic crust. Tectonic compression affected the margin almost continuously since the latest Cretaceous, but was predominantly focused during the mid-Eocene and the late Oligocene-mid-Miocene. The detailed interpretation of post-rift structures and their adjacent strata shows that crustal shortening in the various sectors of the margin is neither synchronous nor similar in style. Main post-rift structures include: (1) thick-skinned transpressional deformation on the distal margin; (2) localized basin shortening on the outer proximal margin; (3) limited reverse faulting and inversion on the inner proximal margin. The location and magnitude of crustal shortening are dependent on the inherited syn-rift geometry, the existence of evaporite (or clay-rich) detachments at depth, the rheological behaviour of previously extended continental crust and the position of the ocean-continent transition zone. The mechanisms of compression are mainly dominated by plate collision associated with the southeastern migration of the Iberian microplate during the Alpine orogeny and with recent westward convergence with the oceanic domain. [ABSTRACT FROM AUTHOR]