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During the orogenic development of the Hellenides, the "Frontal Thrust of Internal Zones" (FTIZ) localised tectonic superposition of the Internal Zones over the External Zones. The belt was subsequently subject to a major extensional deformation responsible for a negative tectonic inversion of the FTIZ, along a major detachment called here "Main Pelagonian Detachment" (MPD). The along-strike changes in the geometry and the kinematics of the MPD suggest different tectonic configurations largely inherited fromthe flat-ramp-flat initial geometry of the thrust. The distribution of the recent basins, mainly located within the Internal Zones, illustrates the major role of the FTIZ reactivation in the overall collapse of Internal Hellenides. [ABSTRACT FROM AUTHOR]

Since the Pliocene, rift basins have developed in the North Evia region at the south-western extension of the North Anatolian Fault. North Evia, therefore, is a key area for investigating Plio-Quaternary deformation within the diffuse Anatolian-Aegean–Eurasian plate boundary. In this study, we present a detailed map of offshore faults in the North Evia region based on three seismic reflection surveys: an airgun (2004) and two very high-resolution Sparker (2017 and 2021) single-channel surveys. Careful and systematic interpretation of these datasets revealed i) the identification of a new basin (Skiathos Basin) located at the western extension of the North Anatolian Fault and ii) two main fault sets striking oblique to the active N–S-directed extension. The seismicity analysis of the study area reveals pure strike-slip displacements along faults previously identified as normal. The NW–SE-striking faults bordering the North Evia Gulf rift are characterised by left-lateral displacements, and the NE–SW faults present dextral focal mechanisms, following the kinematic character of the North Anatolian Fault. We show that dextral strike-slip deformation recently occurred (in the late Quaternary) in the south-western extension of the North Anatolian Fault, suggesting the significant role of this fault system in the complex structural development of the North Evia region. • New seismic profiles in the western extension of North Anatolian Fault. • Mapping offshore fault networks in the North Evia region, Central Greece. • Evidence for a new basin between Sporades Islands and North Evia: Skiathos Basin. • Active strike-slip displacements along NW-SE and NE-SW striking faults. [ABSTRACT FROM AUTHOR]

In the 60s, the Hellenic belt was taken as the "Geosyncline model". Here we take a modern look at this Hellenic/Aegean region which as a concentrate encompasses all the main geodynamic processes known in orogens. This region documents the fundamental characteristics of the geodynamic processes related to mountain building, namely continental rifting, oceanic spreading, oceanic then continental subduction, collision i.e., closure of oceanic basins. In particular, the Mesozoic obduction events in northern Hellenides, and the effects of a still ongoing major extension linked to the active subduction under the Aegean domain. [ABSTRACT FROM AUTHOR]

Abstract: Detailed analysis of the stratigraphic architecture and deformation of lower trench-slope sedimentary basins permits the tectonic evolution of subduction margins to be constrained. This study utilises offshore seismic reflection profiles and onshore outcrop data to examine the entire lower trench-slope of the Hikurangi subduction margin in the eastern North Island, New Zealand. Our results constrain the main spatial and temporal changes of facies and sedimentary units since about 25Ma. We demonstrate that the geometries and locations of Miocene to Quaternary sedimentary basins are controlled by tectonic activity and reflect stages of subduction wedge development. Four types of sedimentary basins have been recognized: 1) flysch basins with local olistostromes at the front of seaward propagating thrust sheets; 2) 5–10km wide turbidite-rich trench-slope basins between uplifting structural ridges (i.e. anticlines) associated with shortening within 100km of the subduction front at the seafloor; 3) 30–40km wide trench-slope basins associated with an upslope increase in thrust and ridge spacing; and 4) mixed siliciclastic-carbonate shelves formed in association with margin uplift after filling of the wider (30–40km) trench-slope basins. The lateral and vertical successions of basin geometries and sedimentary infill are consistent with the overall progressive uplift of the subduction wedge. Formation of some of the wide trench-slope basins may be accompanied by significant local subsidence and normal faulting synchronous with active shortening at the subduction front. Margin-wide normal faulting during the Middle–Late Miocene may have formed due to upslope collapse related to tectonic erosion. All of the basins studied contain major unconformities at their base and top, with basin strata deposited over about 2–8Myr. The short life span of these lower trench-slope sedimentary basins is consistent with a succession of short paroxysmal tectonic episodes rather than continuous deformation for the duration of subduction. Stratigraphic discontinuities within basins (e.g., facies changes and reversal of paleo-currents) also record short-term tectonic events (c. 1–2Myr) on the basin-bounding structures and attest to the episodic nature of upper-plate deformation in response to continuous subduction beneath the active margin. [Copyright &y& Elsevier]

Ophiolitic bodies in the Dinaro-Hellenic mountain belt are among the most important ones in the Peri-Mediterranean Alpine chains. The characteristic feature of this ophiolitic belt is its Middle to Late Jurassic age of obduction. The ophiolitic bodies form two major belts on each side of the Pelagonian zone: an east Pelagonian belt in the Vardarian domain and a Supra-Pelagonian ophiolitic belt (SPO) to the west. The different hypotheses relative to the origin of the SPO present geodynamic evolution models accounting for most of the available data: a mid-Triassic episode of rifting; a Ladinian-Jurassic episode of sea-floor spreading forming notably the Maliac Ocean; a Middle to Late Jurassic convergent period with subduction and obduction episodes, and finally, a late episode of Tertiary compressional deformation responsible for the westward thrusting of the Jurassic ophiolitic nappes over the external zones. Despite many studies dating from the early 1970s, the eastern or western Pelagonian origin of these ophiolites, especially the SPO, is still under dispute. Whatever the adopted hypothesis, we consider that the main SPO bodies (N-Pindos, Vourinos, Othris, Evia, Argolis) have the same origin because of their geographic continuity and of the similarities in their geological characteristics. We propose that this ocean corresponds everywhere to the Maliac Ocean, defined in Othris from the well-preserved sedimentary (oceanic margin) and ophiolitic nappes thrust during the Late Jurassic obduction onto the Pelagonian platform. There is strong evidence for the existence of two deep basins on both sides of the Pelagonian continental ridge during Triassic-Jurassic times. They correspond, respectively, to the Vardar area to the east and the Pindos domain to the west, one of these domains being at the origin of the SPO. The hypothesis of an eastward emplacement of the SPO from the Pindos domain is based mainly on sedimentological data from the margin series and on structural analyses of ophiolitic bodies. However, we conclude the westward obduction of the Maliac Ocean, originating from the Vardar area, to be the best fitting model. This westward model is supported by paleogeographic and structural constraints on regional scale. Notably, the absence of obducted ophiolites in the Jurassic series of the Koziakas units (units attributed to the western Pelagonian margin) and of the Parnassus domain (on the eastern side of the Pindos basin) is difficult to reconcile with an eastward obduction from the Pindos domain. Other observations, such as the distribution of ophiolitic detritus in the internal and external zones, also promote the westward Late Jurassic obduction of the Maliac Ocean. Our preferred model offers a consistent explanation for the mechanism and timing of the emplacement of the SPO, as well as providing insight on the origin and emplacement of the Vardarian ophiolites. Following this hypothesis, there is no need for a clear boundary between the SPO and the west Vardarian ophiolitic bodies as they were obducted from the same oceanic basin and during the same Jurassic tectonic event. In this paper, we develop evidence in favor of the eastern Pelagonian origin for the SPO (our adopted model) and provide discussion on the data supporting the main alternative hypothesis (western origin for the SPO). [ABSTRACT FROM AUTHOR]

When interpreting marine very high-resolution (VHR) single-channel seismic reflection data, the signal in the water column is generally considered as noise and is often eliminated by a water-mute application to focus on geological information under the seafloor. Alternatively, the signal in the water column can be used to study ocean currents or gas/fluid emissions. To provide images of the sedimentary formations and tectonic structures beneath the seafloor in shallow water regions, such as continental shelves and lakes, marine seismic reflection profiles are often acquired using a single-channel streamer and sparker-type source, providing VHR data, with limited penetration depth. To exploit the full potential of these single-channel data, we propose a simple algorithm, called REWARE (Recovery of Water-column Acoustic Reflectors). This algorithm allows to extract further geological information from the water-column data using open-source codes (Seismic Un*x), adding the coherent signal from the previous shots, recorded in the water column, to the previous traces. The record length becomes longer while maintaining a very high trace-to-trace consistency. To demonstrate its efficiency, we present two examples of the REWARE processing in two different geological contexts: the East Sardinia shelf (Italy) and the North Evia Gulf (Greece). This method provides deeper images than with original data for seismic data acquired across steep slopes, such as canyons or continental shelf breaks. Thus, depending on the seafloor geometry and subseafloor structures, it is possible to image or map sediment layers and tectonic structures at depth, keeping a very high structural resolution. [ABSTRACT FROM AUTHOR]

The fill of trench-slope basins is complex, varying temporally, laterally, and longitudinally. New data from the Neogene stratigraphy of the Akitio Sub-basin, Wairarapa, are presented to investigate such fill variation. The preserved basin fill spans an area 70 km long by 10 km wide, representing deposits from a trench-slope basin. Integration of sedimentological, micropalaeoentological, and geological mapping data charts basin fill evolution. Over 15 km of strata were logged, defining 17 lithofacies associations, which were mapped across the basin; these are interpreted to represent both shallow and deep-water environments. The deep-water strata show a temporal evolution from ponded turbidite deposition, to a period of basin spill via conduits connecting to downstream basins, development of aggradational channel-levees, and finally unconfined submarine fan deposition. Shallow marine deposits mostly developed on the up-dip basin margin occur contemporaneously with basinal mass-transport deposits, and in association with the growth of basin bounding structural ridges. Comparison with the evolution of the offshore, actively filling Akitio Trough highlights controls on trench-slope basin fill: a first-order influence of external controls, e.g. tectonism to create the basin; a second-order progression from under- to overfilled; and third-order lateral variation reflecting autogenic process and the effects of local structures on seafloor gradients. These factors combine to vary sedimentation in trench-slope-basins spatially and temporally. [ABSTRACT FROM AUTHOR]

Early Miocene limestones from the Wairarapa region of New Zealand were deposited on thrust-bounded margins of trench-slope basins, and consist of two superposed stratal units, namely units A and B, interpreted as forced regressive and forced transgressive foralgal and rhodolith-bearing deposits, respectively. Unit A is floored by a regressive surface of marine erosion cut into shelfal to bathyal siliciclastic successions, and is overlain across a transgressive surface of erosion by Unit B. A drowning surface abruptly places the latter deposits in contact with deeper hemipelagites and turbidites. The succession is explainable within a tectono-eustatic based framework as follows: (1) Structurally controlled rapid relative sea-level fall, (i.e. sea-bed rise), from upper bathyal to shelfal depths promoted development of regressive ('lowstand') mixed carbonate–siliciclastic deposits. Continuation of seabed rise resulted in deposition of pure carbonate sediments, which are represented by channel-fill rhodolithic rudstones; (2) early stage of relative sea-level rise (i.e. seabed drowning) caused emplacement of transgressive glauconitic limestones, consisting of either foralgal deposits, or incised rhodolithic limestones; (3) continued relative sea-level rise terminated carbonate production. The present study documents carbonate production and termination in a tectonically active and confined intra-slope setting, reflected in the development and distribution of unusual forced regressive, and transgressive rhodolithic-heterozoan carbonates. [ABSTRACT FROM AUTHOR]

Continental shelves generally supply large-scale mass-wasting events. Yet, the origin and significance of shelf-derived mass-transport deposits (MTDs) for the tectonostratigraphic evolution of subduction complexes and their trench-slope basins have not been extensively studied. Here, we present high-resolution, outcrop-scale insights on both the nature of the reworked sediments, and their mechanisms of development and emplacement along tectonically active margins, by examining the Middle Miocene shelf-derived MTDs outcropping in the exhumed southern portion of the Hikurangi subduction margin. Results show that periods of repeated tectonic activity (thrust propagation, uplift) in such compressional settings not only affect and control the development of shelfal environments but also drive the recurrent generation and destruction of oversteepened slopes, which in turn, favour the destabilisation and collapses of the shelves and their substratum. Here, these events produced both large-scale, shelf-derived sediment mass-failures and local debris flows, which eventually broke down into a series of coalescing, erosive, genetically linked surging flows downslope. The associated MTDs have a regional footprint, being deposited across several trench-slope basins. Recognition of tectonic activity as another causal mechanism for large-scale shelf failure (in addition to sea-level changes, high-sedimentation fluxes) has implications for both stratigraphic predictions and understanding the tectonostratigraphic evolution of deep-marine fold-and-thrust belts. [ABSTRACT FROM AUTHOR]

Among other parameters, volcanic activity adjacent to shallow marine environments influences the development of ecosystems and their carbonate-producing communities. Volcaniclastic sediment influx in particular has potential to cause rapid and drastic environmental changes affecting biological systems in their composition and activity, and ultimately leading to changes to and breaks in carbonate sedimentation. Such sedimentary breaks that form in response to volcanic processes are rarely described in detail despite the common occurrence of carbonate platforms adjacent to active volcanoes both in the recent and past geological record. The Island of St. Bartholomew (St. Barths), French West Indies, exposes sections of middle Eocene limestones intercalated with thick volcaniclastic deposits and lavas. Theses carbonates provide an example of a low-latitude tropical platform where non-framework building biota were important, if not dominant, sediment contributors. The carbonate system records the repeated collapse and renewal of carbonate production, as a result of episodic volcaniclastic material input. The discontinuous nature of the carbonate sedimentation is reflected in contrasted depositional systems across sedimentary surfaces and gradational contacts. The studied Eocene deposits provide a sedimentary record of how volcanic events impacted warm-water carbonate factories, both in their disturbance, demise and recovery. [ABSTRACT FROM AUTHOR]

The architecture (geometry, fault network, and stacking pattern of accreted thrust sheets) of accretionary wedges influences subduction zone processes. However, it remains challenging to constrain the architectural evolution in natural accretionary wedges over geological timescales. In this study, we undertook sandbox analog modeling, with quantitative analysis of the wedge geometry and digital image correlation‐based kinematics, to delineate the wedge growth history with four décollement settings (single or double and continuous or discontinuous). The results show that the wedge is formed by repeated episodic frontal accretion with a constant cycle (i.e., the accretion cycle), and the degree of coupling between the base of the wedge and subducting plate interface appears to depend on the relative strengths of the wedge and detachment. An interbedded décollement layer in the incoming sediment facilitated wedge segmentation and rearrangement of the internal fault network, which weakened the wedge strength. A combination of a detachable high‐friction patch in the basal décollement and a continuous interbedded weak layer enabled underplating of underthrusted sediment beneath the inner wedge, which involved a low‐angle, long‐lived forethrust and multiple cycles of frontal accretion on short‐lived forethrusts at the deformation front. Our findings suggest that décollement configuration is a key factor in controlling the accretion cycle, strain distribution, fault network, and wedge strength on timescales of ∼105 yr in natural accretionary systems. This result should be considered when investigating modern subduction zones. Plain Language Summary: Accretionary wedges, which are one of the key components of subduction zones, comprise sediments scraped off from a downgoing plate. However, understanding the spatial and temporal changes of their growth and deformation patterns over geological timescales is challenging. In this study, we conducted laboratory experiments using different types of sands to quantify the deformation processes during wedge growth. We tested various layering conditions and, in particular, how single or double and continuous or discontinuous weak layers affect wedge growth. Our results show that wedge growth is achieved by repetition of a frontal accretion cycle, but the detailed nature of the cycle depends on the properties of the weak layers. In particular, an additional weak layer in the subducting sediment is critical in modifying the accretion cycle, strain distribution, and fault activity during wedge growth. Our findings suggest that weak layers are key in determining the stress–strain state in natural wedges and on the plate boundary as the wedge grows on a timescale of ∼105 yr. Key Points: An interbedded weak layer reduced the effective internal friction angle of the wedge, weakened the wedge, and formed a dense fault networkSubduction of a frictional barrier in the basal décollement resulted in out‐of‐sequence thrusting and facilitated sediment underplatingOur results contribute to an understanding of the growth processes, architectural evolution, and kinematics of natural accretionary wedges [ABSTRACT FROM AUTHOR]

The Hellenides, part of the Alpine orogeny in Greece, are rich in ophiolitic units. These ophiolites and associated units emplaced during Jurassic obduction, testify for the existence of one, or several, Tethyan oceanic realms. The paleogeography of these oceanic areas has not been precisely described. However, all the authors now agree on the presence of a main Triassic-Jurassic ocean on the eastern side of the Pelagonian zone (Vardar Domain). We consider that this Maliac Ocean is the most important ocean in Greece and Albania. Here, we limit the detailed description of the Maliac Ocean to the pre-convergence period of approximately 70 Ma between the Middle Triassic rifting to the Middle Jurassic convergence period. A quick overview on the destiny of the different parts of the Maliac Ocean during the convergence period is also proposed. The studied exposures allow to reconstruct: (1) the Middle to Late Triassic Maliac oceanic lithosphere, corresponding to the early spreading activity at a Mid-Oceanic Ridge; (2) the Western Maliac Margin, widely exposed in the Othris and Argolis areas; (3) the Eastern-Maliac Margin in the eastern Vardar domain (Peonias and Paikon zones). We established the following main characteristics of the Maliac Ocean: (1) the Middle Triassic rifting marked by a rapid subsidence and volcanism seems to be short-lived (few My); (2) the Maliac Lithosphere is only represented by Middle to Late Triassic units, especially the Fourka unit, composed of WPB-OIB and MORB pillow-lavas, locally covered by a pelagic Middle Triassic to Middle Jurassic sedimentary cover; (3) the Western Margin is the most complete and our data allow to distinguish a proximal and a deeper distal margin; (4) the evolution of the Eastern Margin (Peonias and Paikon series) is similar to that of the W-Margin, except for its Jurassic terrigenous sediments, while the proximal W-Margin was dominated by calcarenites; (5) we show that the W- and E-margins are not Volcanic Passive Margins; and (6) during the Middle Jurassic convergence period, the Eastern Margin became an active margin and both margins were affected by obduction processes. [ABSTRACT FROM AUTHOR]

In the Hikurangi subduction wedge (New Zealand), a strong relationship exists between tectonic structures and fluid migrations. In the study area, outcropping tubular carbonate concretions, corresponding to the shallow subsurface plumbing systems of paleo-cold seeps, are hosted by Miocene syn-subduction mudstones. New observations demonstrate the presence of migrated solid bitumen within the tubular concretions and in the fault gouge of a major fault zone. A multi-proxy approach was performed to determine the organic matter thermal maturity in the study area (organic matter petrography and solid bitumen reflectance (BR) R r % (R r : random reflectance)). We also used Rock-Eval pyrolysis, vitrinite reflectance (VR) R r %, and clay mineral reaction progress (illite Kübler-Index and clay mineral paragenesis) to determine the diagenesis grade of the rocks. Low T max values and clay minerals indicate a thermally immature sedimentary cover. The main source rock of the region, the Waipawa Formation is locally thermally mature (VR = 0.86 R r %) suggesting that tectonic thrust-sheet stacking isresponsible for a structural thickening causing local organic maturation. The seaward propagation of out-of-sequence thrusts at base of intra-slope basins could be responsible for the inititation of biogenic fluid flows sourced in the shallow sedimentary cover that is subjected to deformation above the blind thrusts, leading to the earlier generation of the first carbonate tubular concretions. With the continuation of blind thrusting, deep thermogenic fluids then migrated laterally through fault planes (primary migration) and finally vertically through the intrabasinal pre-existing tubular concretions (secondary migration). In this paper, solid bitumen is used for the identification of a fossil thermogenic fluid migration from the source rock, along faults and through tubular carbonate conduits within a subduction thrust-wedge. The study evidences a multi-genetic tubular concretion formation, related with the timing and style of the deformation, being therefore a potential reliable indicator for the evolution of tectonic activity. • Integrated analysis of a plumbing system of paleo-cold seeps on an active margin. • Samples from SR, faults and tubular concretions to determine thermal maturity, bitumen migration, clay mineral reactions. • Circulation of thermogenic fluids in cold seep systems, which correspond initially to migration of shallow biogenic gas. • Role of the shallow plumbing system of biogenic cold seeps as vertical paths for subsequent thermogenic fluid circulations. • Structural thickening due to thrust sheet stacking favor maturation, thrust faults then acting as lateral migration pathway. [ABSTRACT FROM AUTHOR]

Abstract: Multi-scale gravitational instabilities are widespread in the Coastal Ranges of the North Island of New Zealand. We document here a detailed analysis of the Waitawhiti landslide complex, located in the core of the Tawhero syncline, and investigate the potential landslides triggering factors in the area. Four contiguous large slides form the Waitawhiti complex. These slides involve fine-grained Miocene sandstones and massive fractured siltstones. Sliding occurs mostly along nearly horizontal strata. All slides are bounded laterally and/or distally by deep-incised valleys. Three gas seeps evidencing thermogenic gas release have been discovered in the vicinity of the slides. We propose that river incision, continuously removing distal buttresses, is the main destabilizing factor in the area. However, additional factors, such as tectonic activity and intense rainfall, cannot be excluded. We also propose that fluid overpressure, reducing the effective shear strength at the base of low-permeability layers, may have influenced the triggering of landslides in the Waitawhiti area. [Copyright &y& Elsevier]

The Balearic Promontory (Spain) is of key importance to understand the tectonic kinematics of the westernmost Mediterranean, because its continued marine sedimentation has recorded the contrasting effects expected from competing geodynamic models proposed for the region. Near the center of this promontory, between the islands of Mallorca and Ibiza, the Miocene to Pleistocene stratigraphy of the Central Mallorca Depression presents an ideal record of the tectonic deformation that has received only limited attention. We use a widespread dataset of 2D seismic reflection profiles to identify, interpret and map the main prominent reflectors and extrapolate the thickness of the pre-Messinian and Pliocene-Quaternary sedimentary units. We then quantify the timing and style of deformation related to the various fault systems. Our results reveal for the first time a series of aligned small depressions bounded by extensional and strike-slip faults and filled with Plio-Quaternary sediment, perfectly aligned with the sub-basins of the onshore Mallorca Graben. A subsidence analysis confirms this correlation. We identify non-cylindrical deformation within the Plio-Quaternary unit that is remarkably similar to that observed onshore, suggesting continuous fault zones from the Central Mallorca Depression to Mallorca Island. We interpret an intra-PQ unconformity as the marker of a transition from extensional to strike-slip tectonic regime. The strike-slip stage is represented by both transpressional and transtensional structures, interpreted as restraining/releasing bends respectively and step overs along the faults. We show that these offshore faults in the Central Mallorca Depression overlap well with seismic epicenters and suggest major active strike-slip corridors that have an onshore continuity both until eastern Mallorca and in the southwestern Ibiza margin. The role of previous tectonic inherited structures (rifting, Betic thrusts, post-orogenic collapse) on the deformation reported here is discussed and we propose a tentative sketch that integrates our results in a Miocene to Present-day evolution at regional scale. • Post-Messinian deformation affects the Central Mallorca Depression. • Strike-slip fault systems correlate onland-offshore Mallorca and Ibiza Islands. • The systems localize extensional / compressional structures into long corridors. • Small depocenters of PQ units align onland-offshore. • Recent tectonics and important structural inheritance control local subsidence. [ABSTRACT FROM AUTHOR]

The forearc of the North-Central Peruvian Andes (FNCPA, 6–10°S) provides an exceptional opportunity to study the long-term processes that affect a convergent plate boundary. First, it shows long-term subsidence, depocenter superimposition and individualization. Second, although being mostly extensional and characterized as a typical erosive margin, the FNCPA shows complex uplifted regions. Older deformation is expressed by basement horst and grabens disposed in a complex geometry which onset may have resulted from strike-slip tectonics. A long-lived episode of regional subsidence affected the forearc and led to the relatively thick and regional deposition of the lower Miocene series coeval with a significant increase of the convergence velocity. This period was followed by an episodic uplift of trench-parallel corridors along the so-called Main Deformation Zone. Uplift ceased through the late Miocene and restarted during Pliocene and Quaternary, generating accommodation space by basin flank uplift for a forearc depocenter characterized by landward tilted strata. Significant along-strike differences in the degree of uplift resulted in either uplifting series producing sharp seaward dipping erosional surfaces or less uplifted areas covered by seawards prograding clinoforms. As a consequence of the shallow-water marine setting, the seismic strata geometry, lateral extent and thickness of the deposits for the Neogene successions in the FNCPA have been also tightly controlled by accommodation changes. Uplift is uneven along-strike independently of fault direction and closely followed the increase of the subsidence of the continental slope produced by subduction-erosion. Therefore, sediment underplating seems the most appropriate mechanism at the origin of uplift; as observed in other parts of the Peruvian and Chilean margins. Although the erosive character of the margin, the effects on basin geometry of the raised zone resemble that of typical outer forearc highs in accretionary margins such as in the Kumano basin in Japan. • Transtensional depocenters resulted from high obliquity convergence during the Paleogene. • A trench-parallel uplift affected unevenly and episodically the transtensional depocenters since middle Miocene. • Formation of an outer forearc high, similar to those of accretionary settings, individualized a depocenter during Neogene. • Formation of the outer forearc high may have been induced by sediment underplating. [ABSTRACT FROM AUTHOR]

The WATER cruise (July 24th to August 04th 2017) onboard the R/V "Tethys II" allowed to acquire 1378 km of VHR (Very High Resolution) seismic profiles in the Evia Gulf, the Maliakos Gulf and along the Oreoi Channel. This study area, within the northwestern part of the Aegean Sea (Greece), is tectonically active (Palyvos et al., 2006; Sakellariou et al., 2007; Cundy et al., 2010 and Müller et al., 2013). The Hellenic compression and the extensive tectonic induced by African slab retreat and the North Anatolian Fault (NAF) establish a complex stress field in this zone (Sakellariou D. and Tsampouraki-Kraounaki K., 2018). This region therefore constitutes a key sector at the junction between the extensional basins, the frontal thrusts of the internal Hellenic zones and the western termination of the NAF. The study of the area allows to understand the relations between inherited major structural discontinuities of the Aegean lithosphere and the Plio-Quaternary extension. The preliminary results of the analysis of the WATER seismic data show i) a strong tectonic control characterized by numerous normal faults and by the development of horsts and half-graben, ii) the development of a complex sedimentary system due to the LGM (Last Glacial Maximum, Sakellariou et al., 2007) and the active extensive tectonic, and iii) several zones where the acoustic signal is strongly disturbed, called in literature ATZ, (Acoustic Turbide Zone, Papatheodorou et al., 1993; Yoo D.G. and Park S.C., 2000 and Missiaen et al., 2002), probably representing the Pleistocene-Holocene boundary. [ABSTRACT FROM AUTHOR]

Clay minerals and organic matter occur frequently in fault zones. Their structural characteristics and their textural evolution are driven by several formation processes: (1) reaction by metasomatism from circulating fluids; (2) in situ evolution by diagenesis; and (3) neoformation due to deformation catalysis. Clay-mineral chemistry and precipitated solid organic matter may be used as indicators of fluid circulation in fault zones and to determine the maximum temperatures in these zones. In the present study, clay-mineral and organic-matter analyses of two major fault zones - the Adams-Tinui and Whakataki faults, Wairarapa, North Island, New Zealand - were investigated. The two faults analysed correspond to the soles of large imbricated thrust sheets formed during the onset of subduction beneath the North Island of New Zealand. The mineralogy of both fault zones is composed mainly of quartz, feldspars, calcite, chabazite and clay minerals such as illite-muscovite, kaolinite, chlorite and mixed-layer minerals such as chlorite-smectite and illite-smectite. The diagenesis and very-low-grade metamorphism of the sedimentary rock is determined by gradual changes of clay mineral 'crystallinity' (illite, chlorite, kaolinite), the use of a chlorite geothermometer and the reflectance of organic matter. It is concluded here that: (1) the established thermal grade is diagenesis; (2) tectonic strains affect the clay mineral 'crystallinity' in the fault zone; (3) there is a strong correlation between temperature determined by chlorite geothermometry and organic-matter reflectance; and (4) the duration and depth of burial as well as the pore-fluid chemistry are important factors affecting clay-mineral formation. [ABSTRACT FROM AUTHOR]

The METYSS project ( M essinian E vent in the T yrrhenian from S eismic S tudy) is based on high-resolution seismic data acquired along the Eastern Sardinian margin, Western Tyrrhenian Sea. The main aim is to study the Messinian Salinity Crisis (MSC) in the Western Tyrrhenian Basin, but we also investigated the thinning processes of the continental crust and the timing of crustal vertical movements across this backarc domain. Our first results shown that rifting ended before the MSC, but that crustal activity persisted long after the end of the rifting. This has been particularly observed on the proximal margin, the East-Sardinia Basin, where the Mobile Unit (MU, mobile Messinian salt) is thin or absent. In this study, we examined the distal margin, the Cornaglia Terrace, where the MU accumulated during the MSC and acted as a décollement , thus potentially decoupling the basement from the sedimentary cover. Our observations provide evidence for lateral flow and gravity gliding of the salt and its brittle sedimentary overburden along local basement slopes generated by the post-MSC tilting of some basement blocks formerly generated during the rifting. We also investigated an intriguing wedge-shaped body of MU located in a narrow N-S half graben bounded to the west by a major, east-dipping, crustal normal fault. Classically, one could think that this salt wedge is related to the syn-tectonics deposition of the MU, but we propose an original scenario, in which the post-rift vertical motion of the major fault has been cushioned by lateral flow of an initially tabular salt layer, leaving the supra-salt series apparently unaffected by the crustal motions of the basement. We tested this scenario by comparing natural data and physical (analogue) modelling data. Our results reveal that salt tectonics provides a powerful tool to understand the deep crustal tectonics of the margin and to constrain the timing of vertical motions in the Western Tyrrhenian Basin, results that can be applied to rifted salt-bearing margins worldwide. [ABSTRACT FROM AUTHOR]

In the last fifty years, the Messinian Salinity Crisis (MSC) has been widely investigated in the Mediterranean Sea, but a major basin remains fewly explored in terms of MSC thematic: the Western Tyrrhenian Basin. The rifting of this back-arc basin is considered to occur between the Middle-Miocene and the Early-Pliocene, thus including the MSC, giving a unique opportunity to study the crisis in a context of active geodynamics. However the MSC seismic markers in the Western part of the Tyrrhenian Sea have only been investigated in the early eighties and the MSC event in the Western Tyrrhenian Basin remains poorly studied and unclear. In this study, we revisit the MSC in the Western Tyrrhenian Basin, i . e . along the Eastern Sardinian margin. We present results from the interpretation of a 2400 km long HR seismic-reflection dataset, acquired along the margin during the “METYSS” research cruises in 2009 and 2011. The maps of the MSC seismic markers reveal that the Eastern Sardinian margin was already dissected in structurals highs and lows during the MSC. We also demonstrate that the MSC markers constitute powerfull time-markers to refine the age of the rifting, which ended earlier than expected in the East-Sardinian Basin and the Cornaglia Terrace. These results allow us to discuss the palaeo water-depth of the Western Tyrrhenian Basin during the MSC, as well as implications for possibles scenarios of the Messinian Salinity Crisis across the Eastern Sardinian margin. [ABSTRACT FROM AUTHOR]

In order to better constrain the chronology of the Messinian Salinity Crisis (MSC) onland and to provide new observations on the stratigraphic position of the Messinian erosional surface as well as evidence for continentalization, we have studied the Mio-Pleistocene succession of the island of Ibiza, ideally located in a strategic position between the peripheral Messinian basins of south-eastern Spain and the MSC-related gypsum of the Palma Basin (Mallorca). Five lithological units are identified and compared with those known from the island of Mallorca. The equivalent of the "reef" unit, mainly Tortonian in age, is composed of median to inner ramp facies. It is overlain by coastal alluvial fans set up under extensive tectonic control, and then by a carbonate unit rich in oolites and microbialites attributed to the Terminal Carbonate Complex (TCC) of Messinian age. The overlying red clays fossilizing paleosols express a continentalization phase at the end of the Miocene. This regressive episode is evidenced by karstification and erosion incising the pre-crisis units and shaping valleys connected to submarine canyons. The erosion surface is linked to the acme of the MSC, a major sea-level fall, and is then sealed by Pliocene coastal calcarenites or by Pleistocene eolianites. The emptying of the basin led to a global collapse, which is recorded on all the slope domains of the Mediterranean margins. We document this collapse for the first time onland by syn-MSC gravity events such as mudflows, upwelling of geothermal fluids under pressure and soft deformation of the TCC. The interweaving of these phenomena of multiple origin (baselevel decrease, climate change, geothermal activity, sediment transfer) contributes to the onland/offshore reshaping of the Mediterranean margins during the major environmental changes of the Messinian salinity crisis. • Two main regressions and transgressions control Upper Miocene sedimentation. • Extensional tectonic influence is well expressed during Tortono-Messinian interval. • The major regression with generalized emersion is recorded after TCC deposits. • The emersion is contemporaneous with gravitational instabilities and major erosion. • Major erosion is related to the MSC Margin Erosion Surface. [ABSTRACT FROM AUTHOR]

The North Anatolian Fault Zone ( NAFZ) is one of the most hazardous active faults on Earth, yet its Pliocene space-time propagation across the north Aegean domain remains poorly constrained. We use low-temperature multi-thermochronology and inverse thermal modelling to quantify the cooling history of the upper crust across the Olympus range. This range is located in the footwall of a system of normal faults traditionally interpreted as resulting from superposed Middle-Late Miocene N-S stretching, related to the back-arc extension of the Hellenic subduction zone, and a Pliocene-Quaternary transtensional field, attributed to the south-westward propagation of the NAFZ. We find that accelerated exhumational cooling occurred between 12 and 6 Ma at rates of 15-35 °C Ma−1 and decreased to <3 °C Ma−1 by 8-6 Ma. The absence of significant Plio-Pleistocene cooling across Olympus suggests that crustal exhumation there is driven by late Miocene back-arc extension, while the impact of the NAFZ remains limited. [ABSTRACT FROM AUTHOR]