During the Messinian Salinity Crisis (MSC), the entire Mediterranean Basins underwent dramatic canyon incision along their margins due to fluctuating sea levels and rapidly increasing salinity, with decades of research debating the question of whether the Mediterranean Sea desiccated during the crisis. However, the specific processes and water sources responsible for such profound landscape transformations have yet to be quantitatively demonstrated. In this study, we combine high-resolution 3D seismic reflection data with paleo-stream network geomorphic analyses to reveal two distinct phases of fluvial activity within the Messinian Ebro Valley. The first phase is marked by an exceptional discharge which rapidly carved a 700-m-deep valley. This intense incision was followed by a period of more moderate flow, during which the newly formed valley developed alluvial terraces. Our findings suggest that regressive erosion during the MSC lowstand breached the previously endorheic Ebro Basin, triggering a catastrophic outburst flood and the formation of an extensive drainage network. This event marks the transition from a broad, erosive system to a more confined, meandering river. By refining the timing of this outflow event to the MSC, our study challenges earlier models that positioned the Ebro Basin's opening at an earlier time. This most likely represents the first documented case of the complete drainage of an endorheic basin due to an MSC-induced regressive erosion, providing new insights into the dynamics of this major geological period.

The Snow Mountain Volcanic Complex (SMVC; northern California, USA) is a well-preserved example of a coherently-exhumed subducted seamount. This study reappraises the genesis and evolution of this complex and surrounding units through detailed field, petro-structural and geochronological analyses. This work demonstrates that the SMVC (a) erupted at similar to 166 Ma as a hotspot volcano on the Farallon Plate, (b) entered the Franciscan subduction trench at similar to 118 Ma, and (c) was subsequently subducted to a depth of similar to 20 km (within the seismogenic zone), as shown by local blueschist-facies assemblages formed at 0.6 GPa, 240 degrees C. Transient subduction interfaces are preserved above, within, and below the SMVC, making it an exceptional target to study seamount subduction dynamics. Like other seamounts, the subduction-related deformation was mainly accommodated along kilometer-scale internal thrust zones lubricated by serpentinite/metasediments, and within centimeter-thick crack-seal veins recording pulsed fluid flow near peak metamorphism. No unequivocal proof of seismic activity was found. The integration of other seamounts (some potentially belonging to a former seamount chain) in the Franciscan Complex suggests that exhumed seamounts are more abundant than previously thought. Moreover, pressure-temperature-time estimates of subduction metamorphism for the surrounding units, combined with previous work constrain the thermal maturation of the subduction zone through time and the in-sequence emplacement of the SMVC. Rapid changes in age of the subducted oceanic plate when subducted additionally hint to the subduction of large-offset transform faults on the former Farallon plate. Such a process might have been linked to changes in accretion dynamics and magmatic flare-ups in the arc. The Snow Mountain Volcanic complex is a former hotspot volcano subducted to the seismogenic zone High-pressure fabrics and veins capture mixed brittle-ductile behavior of rocks and episodic fluid pulses in the seismogenic zone Thermal maturation of the subduction is achieved in similar to 10 My, subducting plate characteristics governs later accretion and arc activity

Fragments of ancient oceanic lithosphere preserved in mountain belts, though volumetrically subordinate, provide essential insights into past geodynamics and formation and destruction of oceanic lithosphere. This contribution shows how the two types of oceanic fragments, blueschists and eclogites, on one hand, and ophiolites on the other, preserve crucial information on the dynamics of oceanic convergence, that is, subduction and obduction. Their mutual relationships, as well as the similarities and differences in the mechanisms leading to their preservation, allow tracking the evolution of the subduction process through time, from the onset of intraoceanic subduction to the cessation of continental subduction, and, in some cases, to the obduction of ophiolites. Fragments located at the base and immediately below unmetamorphosed (true) ophiolites represent witnesses of intraoceanic subduction initiation and reveal, in particular, initial mechanical resistance to subduction, subsequent cooling, and gradual strain localization. Subducted fragments of oceanic lithosphere metamorphosed as blueschists and eclogites, scraped off the downgoing slab episodically, at shallow or great depths, provide direct access to the composition, structure, and rheology of rocks at the plate interface. Both types reflect the mechanical behavior and "hiccups" of the subduction plate boundary, during subduction initiation and mature subduction, respectively.

Fragments of ancient oceanic lithosphere preserved in mountain belts, though volumetrically subordinate, provide essential insights into past geodynamics and formation and destruction of oceanic lithosphere. This contribution shows how the two types of oceanic fragments, blueschists and eclogites, on one hand, and ophiolites on the other, preserve crucial information on the dynamics of oceanic convergence, i.e. subduction and obduction.Their mutual relationships, as well as the similarities and differences in the mechanisms leading to their preservation, allow tracking the evolution of the subduction process through time, from the onset of intra-oceanic subduction to the cessation of continental subduction – and, in some cases, to the obduction of ophiolites.Fragments located at the base and immediately below unmetamorphosed (true) ophiolites represent witnesses of intra-oceanic subduction initiation and reveal, in particular, initial mechanical resistance to subduction, subsequent cooling and gradual strain localization. Subducted fragments of oceanic lithosphere metamorphosed as blueschists and eclogites, scraped off the downgoing slab episodically, at shallow or great depths, provide direct access to the composition, structure and rheology of rocks at the plate interface.Both types reflect the mechanical behavior and 'hiccups' of the subduction plate boundary, during subduction initiation and mature subduction respectively.

Fragments of former oceans are commonly observed in mountain belts: blueschists and eclogites, on the one hand, and ophiolites, on the other hand, are all that remains of ancient oceanic lithosphere.Though volumetrically subordinate, they provide essential insights into past geodynamics and into the processes involved in the formation and destruction of oceanic lithosphere.This contribution apprehends these two types of oceanic fragments jointly and shows the advantage of doing so for understanding the dynamics of oceanic convergence, i.e. subduction and obduction.We examine the intimate relationships between blueschists/eclogites and ophiolites, as well as the similarities and differences in the mechanisms leading to their preservation.While the extensive, unmetamorphosed true ophiolites markedly differ from fragments of oceanic lithosphere offscraped from the slab during subduction, at shallow or great depths, both types record the mechanical behavior and 'hiccups' of the subduction plate boundary.Their preservation also highlights the importance of the evolution of the subduction regime through time, from the onset of intra-oceanic subduction to the cessation of continental subduction.

The Sistan orogen (Eastern Iran) separates the Afghan and Lut continental blocks and stretches along-700 km from north to south, at a high angle with respect to other, dominantly E-W trending Alpine Himalayan orogens. This study reappraises the tectono-metamorphic evolution of the northern part of the orogen, as well as its significance within the Neotethyan realm. Detailed inspection of the Sistan ophiolite indicates that the Sistan Ocean was of a slow-spreading type and that, given its structural patterns, petrological characteristics and age, it opened in a transtensional setting-125 Ma ago. Closure of the Sistan Ocean took place through a major NE-dipping subduction zone, formed no later than 90 Ma, as shown by the location and age of bimodal juvenile arc magmatism, the SW vergence of the orogen and the location and age of subducted fragments. The discovery of a metamorphic sole at the base of the ophiolite (-750 degrees C-0.65 GPa) argues for the onset of an additional intra-oceanic thrust/subduction zone around 74-72 Ma, which resulted in the south-westward obduction and preservation of the ophiolite onto the continental Lut block. The Sistan Ocean therefore appears to have recorded two major geodynamic events that accompanied the closure of the Neotethys, i.e. the major change in kinematics at-105 +/- 5 Ma and the northward migration of India from-75 to 70 Ma onwards. Subsequent collision, likely started during the Paleocene and mostly completed by the Oligocene, was accompanied by a drastic change of the Eocene sedimentation yet by only moderate shortening (-30-50 km in total). Since the Late Miocene onwards, post-collisional deformation is dominated by far-field stresses related to the Zagros collision.(c) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

The northern Oman margin is a key area for understanding the emplacement of the Semail Ophiolite and obduction processes in general. This study uses a grid of 2D‐multichannel seismic lines tied to well data to characterize the offshore domain of the Semail Ophiolite and reappraises the obduction and post‐obduction history of the Oman margin. West of Muscat, in the Sohar basin, the late Cretaceous to Paleogene tectonic mega‐sequence records syn‐ to late‐obduction stages and the deposition of erosional products of the autochthonous Arabian sediments, including a major mass transport complex. Syn‐obduction thrusting is documented in this sector only, as a major fault emplacing a distal basement high (likely volcanic) onto Campanian sediments over >10 km. To the east, the Hatat and Tiwi basins are characterized by a less‐copious Maastrichtian‐Paleogene sequence. These basins developed above a domain characterized by the northern equivalent of the Saih Hatat dome and later extensional faults. This sector distinctively records the extensional phase associated with the exhumation and erosion of the subducted continental margin. The dichotomy between the two sectors is linked due to a structural high located offshore, in the continuation of the Semail Gap transfer fault. We propose that this transfer fault, coincident with a major Pan‐African structure, affected the architecture of the passive margin during both rifting of the Neotethys and later ophiolite emplacement, that is, during (continental) subduction and obduction.

The Arabian Sea in the NW Indian Ocean is a place where two major transform boundaries are currently active: the Owen Fracture Zone between India and Arabia and the Owen Transform between India and Somalia. These transform systems result from the fragmentation of the India-Africa Transform boundary, which initiated about 90 Myrs ago, when the India-Seychelles block separated from Madagascar to move towards Eurasia. Therefore, the geological record of the Arabian Sea makes it possible to investigate the sensitivity of a transform system to several major geodynamic changes. Here we focus on the evolution of the India-Africa transform system during the similar to 47-90 Ma interval. We identify the Late Cretaceous (similar to 90-65 Ma) transform plate boundary along Chain Ridge, in the North Somali Basin. From 65 to similar to 42-47 Ma, the India-Africa transform is identified at the Chain Fracture Zone, which crossed both the Owen Basin and the North East Oman margin. Finally, the transform system jumped to its present-day location in the vicinity of the Owen Ridge. These shifts of the India-Africa boundary with time provide a consistent paleogeographic framework for the emplacement of the Masirah Ophiolitic Belt, which constitutes a case of ophiolite emplaced along a transform boundary. The successive locations of the India-Africa boundary further highlight the origin of the Owen Basin lithosphere incoming into the Makran subduction zone.

The offshore north Oman margin, located north of the Hajar Mountains in the Gulf of Oman, remains a key area for understanding the evolution of the obduction Emails Ophiolite. With the help of a grid of 2D-multichannel seismic lines linked to well data, we present a new view of the obduction and post-obduction history of the Oman margin. Offshore deposits, overlying on what we interpret as being the offshore extension of the ophiolites, can be divided into two mega-sequences. The older one is comprised of late Cretaceous to Paleogene deposits mainly located in the Sohar basin and offshore of the Abat trough. In the Sohar basin, the latest stages of obduction are recorded by the deposition of the erosional products of the Autochthonous Arabian sediments and the ophiolite, in a flexural basin induced by a volcanic high. Offshore of the Abat trough, a Maastrichtian-Paleocene basin develops above a detachment fault system linked to the extension phase associated to the exhumation/expulsion of the subducted continental margin. Both sectors are divided by a structured high located offshore of the Semail Gap transfer fault. We propose that this transfer fault, likely a major Pan-African structure, impacted both the architecture of the passive margin following the rifting of the Neotethys and later ophiolite emplacement, during (continental) subduction and obduction.

Évolution tectono-sédimentaire et géodynamique de la zone de subduction du Makran et du Golfe d'Oman, du Crétacé supérieur à l'actuel La zone de subduction du Makran, situé entre les plaques Arabe, Indienne et Eurasienne est caractérisé par l’un des plus grands prisme d’accrétion au monde. D’âge cénozoïque, ce prisme présente de fortes différences dans sa morphologie d’Est en Ouest, à terre et en mer. Afin de déterminer les causes de ces disparités, des données de sismiques réflexion ont été étudiés en mer à travers le prisme et le Golfe d’Oman, nous renseignant sur l’évolution de la zone d’étude à l’échelle du bassin. Des données de tomographie sismique ont aussi été étudiés à travers la région, nous renseignant sur la structure lithosphérique de la zone de subduction. Les résultats montrent que la structure du prisme en mer est régie par la dynamique sédimentaire Plio-Pléistocène du prisme, lié à sa cannibalisation. Le secteur occidental du prisme montre une accumulation préférentielle de sédiments dans la plateforme, alors qu’un système turbiditique permet l’acheminement de sédiments à la fosse dans le secteur oriental. La structure profonde de la zone de subduction est caractérisée par un premier panneau plongeant lié à la plaque Arabe, affecté par une déchirure subhorizontale dans la partie ouest de la zone de subduction. Cette déchirure se situe à l’ouest d’une zone de transfert majeur identifié sur la marge Omanaise, indiquant une possible segmentation de la plaque subduite. Cette déchirure est potentiellement responsable de la formation d’un olistostrome dans la partie occidentale du prisme, qui est responsable de la morphologie distincte du prisme émergé dans ce secteur. Un deuxième panneau plongeant, associé à la plaque indienne, est situé dans la partie la plus à l’Est de la subduction.