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Glacial movements shaped vast northern parts, offering critical insights into glacial dynamics in a changing climate. Located on the island of Rügen in NE Germany, the Jasmund Glacitectonic Complex (JGC) is a key area to study the dynamics of past glaciations. Previous reconstructions focused primarily on the onshore realm, resulting in some areas remaining unexplored. Here we use more than 140 high‐resolution marine multi‐channel seismic profiles to map the erosional unconformity surrounding the JGC for the first time. Submarine glacial features match features observed onshore, allowing a consistent land‐to‐sea reconstruction of the evolution of the JGC. Our results indicate a single SW‐directed Weichselian glacier advance, suggesting that the JGC formed through three distinct glacier lobes exerting pressure from multiple directions. The ice advance encircled the Jasmund peninsula and overthrusted Cretaceous sediments on the JGC perpendicularly and laterally. Plain Language Summary: The Jasmund Glacitectonic Complex on Rügen island, northeast Germany, is a popular tourist destination and a key area for studying how deformations and erosion by former ice sheets shape our landscapes. Previous studies were limited to the onshore area and suggested that the complex formed in three separate phases. Our study uses marine seismic imaging techniques that suggest an alternative development. By creating detailed maps of the proposed glacial erosional surface from seismic data, we discovered depressions of different shapes that were carved by glaciers moving southwestwards during the last ice age. The erosional feature is 100 m deep and matches earlier predictions of the ground's response to glacial movement. The mapping indicates that the glacial traces on the seabed extend onto the land. We propose that a single glacier movement was responsible for shaping the entire area in one dynamic phase. This shows that the sediments were compressed and displaced in varying directions during the ongoing (single) ice advance. Key Points: Seismic mapping, offshore channels and depressions, thrust‐fault structures, ice advance dynamics, Jasmund Glacitectonic Complex, Rügen Island and surrounding Baltic Sea, NE Germany [ABSTRACT FROM AUTHOR]

The southern Baltic Sea is a peculiar area, where the Sorgenfrei-Tornquist Zone (STZ), stretching from Bornholm into the North Sea, connects to the Teisseyre-Tornquist Zone (TTZ) that continues SE up to the Black Sea. In this study, we show the structure and evolution of this controversially debated area, both on crustal and basin scale, by using three seismic reflection profiles combined with 2-D potential field data. The results demonstrate that the southern Baltic Sea is underlain by a thick crust of the East European Craton with a Moho depth in the range of 38-42 km. The overall crustal architecture is shaped by three phases of localized stretching in the early Paleozoic, Devonian-Carboniferous, and Permian-Mesozoic. The most spectacular feature of the southern Baltic Sea is a zone of thick-skinned compressional deformation produced by Late Cretaceous-early Paleogene inversion, including a system of thrusts and back thrusts penetrating the entire crust in an 80-90 km wide inversion zone. ENE-vergent thrusts are traced from the top of the Cretaceous down to the Moho and they are accompanied by back thrusts of opposite vergence, also reaching the Moho. Inversion tectonics resulted in the uplift of a block of cratonic crust as a pop-up structure, bounded by thrusts and back thrusts, and the displacement of the Moho within the STZ and TTZ. The similar mechanism of intra-cratonic inversion was recognized for the Donbas Foldbelt in eastern Ukraine, and it may be characteristic of rigid cratons, where deformation is localized in a few preexisting zones of weakness. [ABSTRACT FROM AUTHOR]

Located on the Hellenic Arc, the Christiana‐Santorini‐Kolumbo (CSK) rift zone represents one of the most active and hazardous volcano‐tectonic systems in the Mediterranean. Although this rift zone has been intensively studied, its tectonic evolution and the interplay of volcanism and tectonism are still poorly understood. In this study, we use high‐resolution reflection seismic imagery to reconstruct the opening of the rift basins. For the first time, we relate the activity of individual faults with the activity of specific volcanic centers in space and time. Our analysis shows a pre‐volcanic NNE‐SSW‐oriented paleo basin underneath the CSK volcanoes, representing a transfer zone between Pliocene ESE‐WNW‐oriented basins, which was overprinted by a NE‐SW‐oriented tectonic regime hosting Late Pliocene volcanism that initiated at the Christiana Volcano. All subsequent volcanoes evolved parallel to this trend. Two major Pleistocene tectonic pulses preceded fundamental changes in the volcanism of the CSK rift including the occurrence of widespread small‐scale volcanic centers followed by focusing of activity at Santorini with increasing explosivity. The observed correlation between changes in the tectonic system and the magmatism of the CSK volcanoes suggests a deep‐seated tectonic control of the volcanic plumbing system. In turn, our analysis reveals the absence of large‐scale faults in basin segments affected by volcanism indicating a secondary feedback mechanism on the tectonic system. A comparison with the evolution of the neighboring Kos‐Nisyros‐Yali volcanic field zone and Rhodos highlights concurrent regional volcano‐tectonic changes, suggesting a potential arc‐wide scale of the observed volcano‐tectonic interplay. Plain Language Summary: How do regional tectonic movements and large volcanoes interact? Seismological studies indicate complex volcano‐tectonic feedback links, but, so far, information on the long‐term interactions between tectonics and volcanism is rarely available. The Christiana‐Santorini‐Kolumbo (CSK) rift zone lies in the Aegean Sea and is notorious for its devastating volcanic eruptions, earthquakes, and tsunamis. This region offers the opportunity to study volcano‐tectonic interactions over several million years. In this study, we use high‐resolution seismic imagery to reconstruct the evolution of the rift basins and the CSK volcanoes. We find that all volcanoes lie in a Pliocene transfer zone connecting extensional basins. Volcanism initiated as this older tectonic regime was intersected by a NE‐SW‐directed fault system. Subsequently, all volcanoes evolved parallel to this trend. Several distinct tectonic reorganizations occurred in the Pleistocene, which had a pronounced influence on the CSK volcanoes. In turn, our analysis indicates that the emergence of volcanism also impacted the tectonic evolution of the rift system hindering the evolution of large‐scale normal faults in the volcanic basins. The observed tectonic reorganizations seem to reflect major changes in the stress regime of the Hellenic Arc, potentially also affecting adjacent volcanic centers whose volcano‐tectonic evolution is only poorly constrained so far. Key Points: We reconstruct the volcano‐tectonic evolution of the Christiana‐Santorini‐Kolumbo rift zone using multichannel seismic dataThe overprint of a Pleistocene NE‐SW striking fault system on a Pliocene E‐W oriented system initiated the emergence of volcanismRegional tectonics had a primary control on the volcanic plumbing system, while magmatism had a secondary influence on the tectonic system [ABSTRACT FROM AUTHOR]

The Dom João de Castro seamount in the Hirondelle Basin (Azores) is a central volcano on the ultraslow diverging Terceira Rift axis. The combination of structural and geochemical data provides insights into the evolution of central volcanoes in oceanic rift systems above the Azores melting anomaly. The orientation of fault scarps and volcanic structures at D. João de Castro and the adjacent Castro fissure zone indicate that the regional SW‐NE extending stress field dominates the morphology of the NW Hirondelle Basin. The regional tectonic stress field controls the crustal melt pathways and leads to dike emplacement along fissure zones and the prevalent eruption of mafic lavas. The occurrence of mafic to felsic lavas at D. João de Castro gives evidence for both a deep and a shallow crustal melt reservoir generating a subordinate local stress field at the seamount. New Sr‐Nd‐Pb isotope data along with incompatible trace element ratios indicate that D. João de Castro and the Castro Ridges originated from similarly heterogeneous mantle source but did not form simultaneously. Our new model implies that central volcanoes along the Terceira Rift form by the growth of volcanic ridges and transitioned into circular edifices after magmatic systems generate local changes in the regional lithospheric stress field. The geometry of D. João de Castro and other magmatic systems along the Terceira Rift combined with the alkaline nature of the erupted lavas, and the large lithosphere thickness indicates that young oceanic rifts are more similar to continental rifts rather than mid‐ocean ridges. Plain Language Summary: Dom João de Castro seamount is a large submarine volcano located in the submarine Hirondelle Basin in the Azores archipelago. The Hirondelle Basin is formed as a result of extensional forces in the oceanic crust along the Azorean Terceira Rift that causes rifting of the Eurasian and Nubian plates. The presence of the D. João de Castro volcano and several elongated volcanic ridges inside the basin shows that the extensive magmatic activity in the Azores contributes to the opening of the basin. By quantifying the orientations of the tectonic and volcanic structures in the basin, it can be shown that the formation is controlled by a dominant SW‐NE directed extensional stress combined with extensive magmatic activity. Based on combined structural and geochemical observations, we conclude that the D. João de Castro seamount formed from the growth of elongated volcanic ridges and transitioned into a circular edifice after a magma system generates a local change in the crustal stress field. The geometry and geochemical composition of volcanic rocks from the D. João de Castro magmatic system, as well as other magmatic systems along the Terceira Rift are more similar to continental rift systems rather than oceanic spreading centers. Key Points: D. João de Castro seamount in the Terceira Rift, Azores is influenced by a SW‐NE regional transtensional and a local radiating stress fieldStructural, seismic, and geochemical data imply formation by the growth of volcanic ridges along with local stress field changesThe geometry, chemistry, and rifting rates of the Terceira Rift are more comparable to continental rifts rather than mid‐ocean ridges [ABSTRACT FROM AUTHOR]

A vast majority of marine geological research is based on academic seismic data collected with single‐channel systems or short‐offset multichannel seismic cables, which often lack reflection moveout for conventional velocity analysis. Consequently, our understanding of Earth processes often relies on seismic time sections, which hampers quantitative analysis in terms of depth, formation thicknesses, or dip angles of faults. In order to overcome these limitations, we present a robust diffraction extraction scheme that models and adaptively subtracts the reflected wavefield from the data. We use diffractions to estimate insightful wavefront attributes and perform wavefront tomography to obtain laterally resolved seismic velocity information in depth. Using diffraction focusing as a quality control tool, we perform an interpretation‐driven refinement to derive a geologically plausible depth‐velocity model. In a final step, we perform depth migration to arrive at a spatial reconstruction of the shallow crust. Further, we focus the diffracted wavefield to demonstrate how these diffraction images can be used as physics‐guided attribute maps to support the identification of faults and unconformities. We demonstrate the potential of this processing scheme by its application to a seismic line from the Santorini Amorgos Tectonic Zone, located on the Hellenic Volcanic Arc, which is notorious for its catastrophic volcanic eruptions, earthquakes, and tsunamis. The resulting depth image allows a refined fault pattern delineation and, for the first time, a quantitative analysis of the basin stratigraphy. We conclude that diffraction‐based data analysis has a high potential, especially when the acquisition geometry of seismic data does not allow conventional velocity analysis. Plain Language Summary: The active seismic method is a standard tool for studying and imaging the Earth's lithosphere. Proper imaging of complex geological targets requires seismic data of excellent quality, which are typically only acquired with expensive industrial surveys. Academic surveys, however, are often restricted to marine seismic equipment with limited illumination, which compromises imaging and interpretation. While most of the contemporary processing and interpretational routines are tailored to the reflected wavefield, recent research suggests that the often overlooked diffracted wavefield might help to overcome the gap between academic and industrial seismic imaging. Wave diffraction is the response of the seismic wavefield to small‐scale subsurface structures and allows to estimate velocities even from single‐channel seismic data. In this study, we use an academic seismic profile from the southern Aegean Sea and extract a rich diffracted wavefield from the data. We utilize these diffractions to estimate a velocity model that permits a reconstruction of the subsurface in depth and specifically highlight discontinuous features related to past dynamic processes. Such depth images allow us to reliably measure thicknesses and fault angles. We conclude that diffraction‐based data analysis has a high potential for academic research and strongly encourage its application in future studies. Key Points: Based on waveform similarities, we surgically extract a detail‐rich diffracted wavefield from zero‐offset seismic data from the Aegean SeaFully driven by data, we infer a laterally resolved velocity model from zero‐offset information through diffraction wavefront tomographyAfter interpretation‐guided refinement, we derive depth‐migrated reflection and diffraction images which we use for interpretation [ABSTRACT FROM AUTHOR]

In this study, we investigate the impact of Late Cretaceous to Neogene plate tectonics and Pleistocene ice load on the post-Jurassic strata above the Waabs salt wall within the Eastern Glückstadt Graben by integrating reflection seismic, parametric sub-bottom profiler and well data. Previous studies showed that a collapse graben developed above the salt during several tectonic pulses. However, due to the lack of age constrains, the relationship between local salt tectonics and variations of the regional stress field caused by plate tectonics was just little constrained. Here, we introduce an inter-Cenozoic stratigraphy enabling us to infer and date three major salt tectonic phases. During the Late Cretaceous to Eocene, Africa–Iberia–Europe convergence and subsequent Pyrenean orogeny strata above the salt wall were pushed upwards and faulted. Thickness variations of the Upper Cretaceous and Eocene strata imply at least two pulses for this upward push. The second phase includes the major graben collapse in the Neogene, when the stress regime changed from a compressional to an extensional regime. The third phase is a period of locally differing tectonic reactivation likely caused by ice sheet loading and unloading during the Quaternary. Based on time-isochore and time-structure maps, we elucidate how this last glacial phase of salt tectonic movement likely formed the present day Mittelgrund shoal within the Eckernförde Bay. The spatial correlation between shallow faults and freshwater seepage implies further a causal relationship between fluid migration and faulting. [ABSTRACT FROM AUTHOR]

During R/V Meteor cruise 141/1, pore fluids of near surface sediments were investigated to find indications for hydrothermal activity in the Terceira Rift (TR), a hyperslow spreading center in the Central North Atlantic Ocean. To date, submarine hydrothermal fluid venting in the TR has only been reported for the D. João de Castro seamount, which presently seems to be inactive. Pore fluids sampled close to a volcanic cone at 2,800‐m water depth show an anomalous composition with Mg, SO4, and total alkalinity concentrations significantly higher than seawater and a nearby reference core. The most straightforward way of interpreting these deviations is the dissolution of the hydrothermally formed mineral caminite (MgSO4 0.25 Mg (OH)2 0.2H2O). This interpretation is corroborated by a thorough investigation of fluid isotope systems (δ26Mg, δ30Si, δ34S, δ44/42Ca, and 87Sr/86Sr). Caminite is known from mineral assemblages with anhydrite and forms in hydrothermal recharge zones only under specific conditions such as high fluid temperatures and in altered oceanic crust, which are conditions generally met at the TR. We hypothesize that caminite was formed during hydrothermal activity and is now dissolving during the waning state of the hydrothermal system, so that caminite mineralization is shifted out of its stability zone. Ongoing fluid circulation through the basement is transporting the geochemical signal via slow advection toward the seafloor. Plain Language Summary: Hydrothermal vents are a common phenomenon in oceanic spreading centers worldwide. During Meteor cruise 141/1 we sampled sediments and extracted pore fluids to find the first indications for hydrothermal activity in the Terceira Rift. The results indicate that a hydrothermal vent close to a major volcanic cone formed in the past and seems to be in a waning state at present. Sampled fluids are enriched in total alkalinity, Mg and SO4. We found that the most straightforward explanation for this unusual finding is the dissolution of the hydrothermally formed mineral caminite, a magnesium‐sulfate‐hydroxide‐hydrate. Caminite is a rare mineral but suggested to be abundant under specific conditions in hydrothermal recharge zones. We propose that caminite formed in the Terceira Rift is now dissolving as temperatures decline, and fluids enriched in Mg and SO4 are transported along deep‐rooted faults to the seafloor. Key Points: Anomalously high Mg and SO4 pore fluids in sediments of the Terceira Rift, AzoresIndication for abundant caminite (Mg‐sulfate‐hydroxide‐hydrate) formation and dissolution in a hydrothermal recharge zoneFirst indication for a deep submarine hydrothermal system in the slow‐spreading Terceira Rift [ABSTRACT FROM AUTHOR]

In this study we investigate the Late Cretaceous to recent tectonic evolution of the southwestern Baltic Sea based on a dense grid of seismic reflection profiles. This area covers the Baltic Sea sector of the salt influenced North German Basin and its transition to the salt free Baltic Shield across the Tornquist Zone. The Upper Cretaceous to recent structural evolution is discussed by means of individual seismic sections and derived high-resolution time-structure maps of the main horizons, i.e., the Upper Cretaceous, Tertiary and Pleistocene. The Upper Cretaceous and Tertiary layers reveal numerous significant faults throughout the study area. Several of these faults propagate upwards across the unconsolidated Pleistocene sediments and occasionally penetrate the surface. The salt influenced North German Basin reveals three major fault trends: NW-SE, N-S and NNE-SSW. Several of these faults are located directly above basement (sub-salt) faults and salt pillows. The majority of these faults are trending N-S to NNE-SSW and parallel the direction of the Glückstadt Graben faults. In the salt free Tornquist Zone, we identify two major shallow fault trends, which are NW-SE and NE-SW. The majority of these faults are located above basement faults, following the direction of the Tornquist Zone. We conclude that generally basement tectonics controls activation and trends of shallow faults. If salt is present, the ductile salt layer causes a lateral shift between the sub- and supra-salt faults. Major plate reorganisation related to the Africa-Iberia-Europe convergence and the subsequent Alpine Orogeny caused reactivation of pre-existing faults and vertical salt movement in the Late Cretaceous. The change of stress orientation from NE-SW to a NW-SE during Neogene caused another phase of fault and salt tectonic reactivation. We explain that the ice-sheet loading and/or present-day stress field may have acted in combination, causing the recent tectonics and upward extension of the faults. [ABSTRACT FROM AUTHOR]

In this study we investigate faulting above a salt wall in the Glückstadt Graben/North German Basin. Two supra-salt faults are mapped from coast to coast over a distance of 6–9 km based on offshore and onshore seismic data. These faults form a ca. 2 km wide crestal collapse graben and pierce the seafloor. Salt wall evolution started in the early Late Triassic to Early Jurassic due to regional extension and resulting sub-salt faulting. The salt wall was eroded following exposure to costal and sub-aerial erosion by the regional Mid-Late Jurassic to Early Cretaceous uplift. Late Cretaceous to Early Paleogene compressional tectonics reactivated the vertical salt movement and shortened the salt wall, creating a salt-cored anticline with the crestal collapse graben above. The supra-salt faults were reactivated between the Late Eocene and Middle Miocene when the principal horizontal stress orientation changed from a NE–SW to a NW–SE, the present-day orientation. Stratigraphic data indicate that these faults moved mainly in the Cenozoic. Several observations strongly suggest that the faults continued developing during the Pleistocene until today: (i) the Pleistocene Unconformity is concave upwards and cut by faults; (ii) growth strata within the marine Holocene deposits above the graben imply recent tectonic movements; (iii) onshore high-resolution P-wave vibroseis data of the south-eastern Eckernförde Bay suggest about 10 m of faulted Holocene strata; and (iv) marine seismic data show the faults piercing the seafloor. We suggest that the recent salt tectonics and upward propagation of supra-salt faults resulted from differential ice-sheet loading. That effect on the salt wall stopped once ice grew over the whole structure, at which time the wall subsided because of ice loading. The salt wall and faults were reactivated again once the ice front retreated so that the ice loaded only one side of the structure. [ABSTRACT FROM AUTHOR]

The Bay of Oran is part of the northern Algerian continental margin, located in the Western Mediterranean Sea between Europe and northern Africa. A regional terrace in ca. 320 m water depth described in earlier studies and a second deeper located one (∼1200 m water depth) provide an unusually vast amount of accommodation space for an observed prograding wedge. Seismo-stratigraphic interpretation of high-resolution reflection seismic data show different phases of mixed cool-water carbonate-siliciclastic deposition: (Ia) Initial aggradation with low dipping foreset deposition during early-Pliocene relative sea-level highstand. (Ib) Deposition transitions to progradation when aggradation reaches the base level. (IIa) Once progradation reaches the shelf break, terrace deposition is reduced to coarse fraction foreset deposits until it ceases entirely. (IIb) Finer sediments are bypassed and start to aggrade on the lower slope terrace until deposits reach the shelf terrace depth. (III) Due to accommodation space prolongation progradation recommences. Phase IIa and phase III deposits are separated by a hiatus. A drop in mean sea-level during the mid-Pleistocene will have caused the base level to fall below the upper strata, hence causing some reworking and redeposition. However, sea-level variations are not considered to be a main controlling factor of the depositional sequences. The evolution of this continuous Pliocene–Pleistocene mixed cool-water carbonate-siliciclastic prograding wedge is instead attributed to the controlling factor of this unusually vast amount of accommodation space. In closest proximity to the sea-floor, sparse recent sedimentation in form of 5–10 m thick sediment lobes can be observed in subbottom profiler data only. From a tectonic point of view, a prolongation of the Yusuf Fault into the survey area though expected by other authors could not be supported with the available dataset. [ABSTRACT FROM AUTHOR]

Most case studies dealing with the evolution of volcanic islands concentrate on the onshore domain. In contrast, the interplay of constructional and destructive processes in the offshore domain is often paid less attention, although they commonly represent most part of the edifice. Combining bathymetric and multi-channel seismic data, this study focuses on the impact of volcanism, erosion, tectonics, time-variant sediment supply and climatic/oceanographic conditions on the submarine sedimentation processes in the southeastern Terceira Rift (Azores Plateau). Where the major onshore volcanic systems at São Miguel Island (the largest volcanic edifice in the southeastern Terceira Rift) evolved between the last and the previous glacio-eustatic sea level minimum, an average depth value of 142 m of the corresponding shelf segments indicates a formation during the Last Glacial Maximum and a long-term subsidence of approximately 0.6 mm/a. Below the shelf edge, the western flank is characterized by submarine volcanism, while the northern slope is mostly affected by strong turbidity events favored by the north coast's exposure to North-Atlantic storm swell. These turbidity currents pass the shelf break by retrogressive canyons/gullies and follow a widespread system of channels towards the deep sea. Where gullies are not connected to channel systems or where turbidity currents overspill the channel walls, stacked lobe deposits are formed. At the southern slope, a more constant downslope sediment transport leads to the formation of cyclic steps, chutes-and-pools and, further distal, turbidity lobes. Turbidity currents follow morphological features and enter the basins via structural bottlenecks. In the basins, bottom currents are controlled/deviated by volcanic highs or fault scarps, where they cause the deposition of drift bodies. High local accumulations of sediments caused by a channelized sediment flux, bottom currents or onshore volcanism were partly remobilized resulting in slumping/sliding and a volcanic ridge partly collapsed due to tectonic stress and/or gravity spreading. [ABSTRACT FROM AUTHOR]

The structural evolution of the South Aegean Sea is little explored due to the lack of marine seismic data. Our present day understanding is mainly based on some island outcrops and GPS measurements. In this study we discuss the rather incremental opening of the Anydros Basin in the Pliocene during six major tectonic pulses and the subsequent basin fill processes by interpreting seismic data and derived time isochore maps. Between the active pulses basin floor tilting persisted on a much lower rate. Seismic data illustrate the depositional processes in the emerging Anydros Basin. The observation of onlap fill strata, divergent reflection pattern, moat channels and contourite drifts imply that deposition was controlled by turbidity and contour currents as well as the tilting basin floor. The metamorphic Attico–Cycladic basement shows a rise that aligns along an NW–SE directed axis crossing Anydros island. This axis marks a structural change of the Santorini–Amorgos Ridge and thus represents a major structural boundary. Dip angles of NE–SW trending major faults, like the Santorini–Amorgos Fault, indicate normal faulting to be the superior mechanism forming the present horst and graben environment. Hence, the area is likely to be in a state of NW–SE directed extensional stresses forming the asymmetric graben structure of Anydros. Secondary fault clusters strike the same direction but show much steeper dip angles, possibly indicating strike-slip movement or resulting from deformational stresses along the hinge zones of the normal faults. The majority of the faults we discovered are located in the area of earthquake clusters, which is another indication of recent faulting. Ring faults around Kolumbo submarine volcano, result from caldera collapse and mark the diameter of the magma chamber approximately to 20 km. [ABSTRACT FROM AUTHOR]

In 2010, a wide-angle seismic reflection/refraction profile was acquired along the Hecataeus Rise, an area of shallow seabed immediately south of Cyprus in the eastern Mediterranean. The profile crossed from the Hecataeus Rise, through the Cyprus Arc to the Levantine Basin beyond. Due to the short length of the profile and the corresponding lack of deep ray coverage, velocity modelling was complemented by gravity modelling to gain constraints on deep crustal structure. The resultant model reveals velocities for the Hecataeus Rise that show no evidence of shallow ophiolites like those seen on mainland Cyprus, and the velocities are not diagnostic of a unique crustal affinity. Low-velocity sediments make up at least 7 km of the upper structure of Hecataeus Rise and these sediments overlie a two-layered crust. From the gravity modelling, the combined sediments and crust of Hecataeus Rise appear to be thinner than the Eratosthenes Seamount block to the southwest. A high-velocity lower crustal block is modelled under the seaward edge of Hecataeus Rise and, based on the gravity modelling, is inferred to extend landwards beneath the Rise. Similar high-velocity blocks were identified on the southwestern edge of Hecataeus Rise along nearby refraction lines and were interpreted as remnant Tethyan oceanic crust, foundered in the Cyprus Arc, along which subduction has ceased in this area. Given the thin two-layered crust beneath a thick accumulation of sediments modelled for Hecataeus Rise, we interpret that Hecataeus Rise represents a collage of oceanic fragments, accreted together within the failed subduction zone. Outboard of the crust of Hecataeus Rise, a 5-km deep low-velocity basin, possibly an accretionary wedge, is imaged that appears to correspond with the Cyprus Arc deformation zone imaged on both coincident and along-strike seismic reflection lines. A similar and wider feature is observed on seismic refraction lines to the west and combined, these may be revealing an eastward tapering zone of crustal deformation. To the south of the profile, the Levantine Basin appears undisturbed by the collision to the north and exhibits a uniform and homogeneous velocity structure. [ABSTRACT FROM AUTHOR]

Morphologic studies with sonar data and in situ observations of modern eruptions have revealed some information suggesting how submarine volcanic cones develop, but the information only addresses the modern surfaces of these features. Here, we describe a study combining morphological data with high-resolution seismic reflection data collected over cones within the southeastern Terceira Rift — a succession of deep basins, volcanic bathymetric highs and islands (e.g. São Miguel) representing the westernmost part of the Eurasian–Nubian plate boundary. The cones (252) are distributed in depths down to 3200 m and exhibit an average diameter of 743 m, an average slope of 20° and heights mainly between 50 and 200 m. The cones are here classified into three different categories by physiographic or tectonic setting (we find no particular morphometric differences in cone shapes between these areas). First, numerous cones located at the submarine flanks of São Miguel's Sete Cidades and Fogo Volcano are considered to be parasitic structures. Second, in the southeast of the island, they form a superstructure possibly reflecting an early submarine stadium of a posterior subaerial stratovolcano. Third, some cones are controlled by faults, mostly in a graben system southwest of the island. High-resolution multichannel seismic data indicates that the graben cones evolved synchronously with the graben formation. Bottom currents then probably removed the surficial fine grain-size fraction, leaving rough surface textures of the cones, which backscatter sonar signals strongly in the data recorded here. However, a young cone investigated in detail is characterized by a smooth surface, a marked increase of internal stratification with increasing distance from the summit and upwards concave flanks. Others exhibit central craters, suggesting an explosive than an effusive evolution of these structures. The morphological characteristics of these submarine cones show that they have similar sizes and shapes to cinder cones onshore São Miguel. [ABSTRACT FROM AUTHOR]

The eastern Azores Archipelago with São Miguel being the dominant subaerial structure is located at the intersection of an oceanic rift (Terceira Rift) with a major transform fault (Gloria Fault) representing the westernmost part of the Nubian–Eurasian plate boundary. The evolution of islands, bathymetric highs and basin margins involves strong volcanism, but the controlling geodynamic and tectonic processes are currently under debate. In order to study this evolution, multibeam bathymetry and marine seismic reflection data were collected to image faults and stratigraphy. The basins of the southeastern Terceira Rift are rift valleys whose southwestern and northeastern margins are defined by few major normal faults and several minor normal faults, respectively. Since São Miguel in between the rift valleys shows an unusual W–E orientation, it is supposed to be located on a leaky transform. South of the island and separated by a N120° trending graben system, the Monacco Bank represents a N160° oriented flat topped volcanic ridge dominated by tilted fault blocks. Up to six seismic units are interpreted for each basin. Although volcanic ridges hamper a direct linking of depositional strata between the rift and adjacent basins, the individual seismic stratigraphic units have distinct characteristics. Using these units to provide a consistent relative chrono-stratigraphic scheme for the entire study area, we suggest that the evolution of the southeastern Terceira Rift occurred in two stages. Considering age constrains from previous studies, we conclude that N140° structures developed orthogonal to the SW–NE direction of plate-tectonic extension before ~ 10 Ma. The N160° trending volcanic ridges and faults developed later as the plate tectonic spreading direction changed to WSW–ENE. Hence, the evolution of the southeastern Terceira Rift domain is predominantly controlled by plate kinematics and lithospheric stress forming a kind of a re-organized rift system. [ABSTRACT FROM AUTHOR]

Advancing ice sheets have a strong impact on the earth's topography. For example, they leave behind an erosional unconformity, bulldozer the underlying strata and form tunnel valleys, primarily by subglacial melt-water erosion and secondarily by direct glacial erosion. The conceptual models of the reactivation of faults within the upper crust, due to the ice sheets' load, are also established. However, this phenomenon is also rather under-explored. Here, we propose a causal link between ice-load induced tectonics, the generation of near-vertical faults in the upper crust above an inherited deep-rooted fault and the evolution of tunnel valleys. The Kossau tunnel valley in the southeastern Bay of Kiel has been surveyed by means of high-resolution multi-channel seismic and echosounder data. It strikes almost south to north and can be mapped over a distance of ca 50 km. It is 1200-8000 m wide with a valley of up to 200 m deep. Quaternary deposits fill the valley and cover the adjacent glaciogenic unconformity. A near-vertical fault system with an apparent dip angle of >80°, which reaches from the top Zechstein upwards into the Quaternary, underlies the valley. The fault partially pierces the seafloor and growth is observed within the uppermost Quaternary strata only. Consequently, the fault evolved in the Late Quaternary. The fault is associated with an anticline that is between 700 and 3000 m wide and about 20-40 m high. The fault-anticline assemblage neither resembles any typical extensional, compressional or strike-slip deformation pattern, nor is it related to salt tectonics. Based on the observed position and deformation pattern of the fault-anticline assemblage, we suggest that these structures formed as a consequence of the differential ice-load induced tectonics above an inherited deep-rooted sub-salt fault related to the Glückstadt Graben. Lateral variations in the ice-load during the ice sheet's advance caused differential subsidence, thus rejuvenating the deep-rooted fault. As a result, the inherited fault propagated upwards across the Zechstein and post-Permian overburden and further grew during the ice sheet's retreat. The developing fault and anticline system under the ice sheet created a weakness zone that facilitated erosion by pressurized glacial and subglacial melt-water, as well as by the glaciers themselves. Near-vertical faults cutting through the post-Permian are abundant in the southwestern Baltic realm, which implies that the ice-load induced tectonic activity described above was not an isolated incident. [ABSTRACT FROM AUTHOR]

Abstract: The post-Permian sequence stratigraphical and structural evolution of the Northeastern German Basin and its transition onto the Baltic Shield has been studied in the Bay of Mecklenburg (SW Baltic Sea) by means of seismic interpretation. Five major sequences have been identified: Middle Triassic, Upper Triassic, Jurassic, Cretaceous and Cenozoic. Time–isochore maps allowed the identification of several phases of salt pillow growth. The contemporaneity of active salt tectonics and the well studied tectonic evolution of the Northeastern German Basin suggest a causative correlation. The E–W directed extension during the Triassic-Early Jurassic marking the beginning break-up of Pangaea is seen as the trigger process for the first period of salt movement. A fault system outside the limit of the Zechstein evaporates is understood as the consequence of thin-skinned faulting and brittle thick-skinned deformation that accompanied this extension. The observed pronounced erosion of Upper Triassic and Lower Jurassic strata is considered to result from the uplift due to the Mid North Sea Doming event in Middle Jurassic times. The seismic data show an undisturbed Late Cretaceous succession which reflects a period of rising sea level, tectonic quiescence and no salt movement. In contrast to the salt pillows which emerged above Triassic fault systems in the westernmost Baltic and western North German Basin, the Cenozoic salt movement activity is the most pronounced. This period of reactivated salt pillow growth started coevally with the onset of the Alpine orogeny at the Cretaceous/Cenozoic transition when the Africa-Arabian plate collided with Eurasia. Generally, no significant faults were identified in the overburden of the salt floored southern Bay of Mecklenburg where ductile Zechstein salt decouples deep rooted faulting from supra-salt deformation. [Copyright &y& Elsevier]

Abstract: Salt tectonics and mud volcanism in the Latakia and Cyprus Basin, eastern Mediterranean, is investigated by means of swath sounding, reflection seismics and side-scan data as well as by camera and video sledge observations. Both basins are located east of Cyprus and are associated with the collision front between the African and Anatolian plate. The Pliocene–Quaternary sediment succession is underlain by up to 1 km thick Messinian evaporites. Both thick-skinned plate tectonic and thin-skinned salt tectonic control fluid dynamics and associated mud volcanism in the Latakia and Cyprus Basin as well as at the Troodos Latacia Culmination, which separates both basins. An end-member model is proposed which explains the presence of elongated topographic highs and trenches along the Troodos Larnaca Culmination and south of it by gravity gliding of the Messinian evaporites and associated fluid migration. Thin-skinned extension in the Troodos Larnaca Culmination and boudinage, respectively, facilitate fluid flow through and out of the evaporites. The fluid or mud flow dissolutes the salt layer and creates elongated trenches. Mud intrudes into the Pliocene–Quaternary sediments above the trenches. Consequently, the overburden is thickened and forms morphological ridges. South of the culmination the evaporites and overburden are folded due to thin-skinned shortening of the evaporites. In one instance fluid extrusion out of the evaporites is inferred from seismic data interpretation. The outflow caused a volume reduction and collapse of the evaporites. Mud volcanoes and fold anticlines align above deep-rooted transpressional fault systems which are associated with the African–Anatolian collision zone. The faults may act as conduits for rising fluids. In the western part of the survey area, where the Cyprus Arc strikes almost West–East and the collision occurred more frontal and stress was highest, mud volcanoes emerged. Further to the east, where the Cyprus Arc runs SW–NE and sinistral strike-slip has been proposed, fold anticlines evolved. Particular mud volcanoes and folds emerged prior to the deposition of the Messinian evaporites. The undisturbed upper Pleistocene sequences as well as the absence of significant mud outflow on the seafloor strongly suggest that the main fluid dynamic ceased. [Copyright &y& Elsevier]

Abstract: The northern Red Sea represents a continental rift in its final stage and close to the following stage of seafloor spreading. Ocean deeps within the evaporites of the northern Red Sea seem to accompany this process and are thought to be surface expressions of first seafloor spreading cells. In 1999 during R/V Meteor cruise M44/3 a dense multichannel seismic and hydroacoustic survey was conducted in order to investigate the initial formation process of the Conrad Deep, a young northern Red Sea deep. Three seismic units were differentiated in the uppermost part of the Miocene evaporites and the Plio-Quaternary sediments. A weakness zone within the evaporites, oblique to the main extension direction of the Red Sea, led to a transtension process within the evaporites that opened the deep. Its formation is directly related to the emplacement of magmatic bodies in its vicinity and the focusing of the Red Sea extension to the axial depression. The Conrad Deep is an intra-evaporite basin that cannot be regarded as surficial expression of a basement structure as the low shear strength of the evaporites decouple the sediments from the basement. However, its position and shape in combination with the accompanying geophysical anomalies point to a strong correlation with the Red Sea rifting process. [Copyright &y& Elsevier]

Abstract: A vertical succession of five composite sequences has been identified within the upper 100 m of the outer Bengal Shelf by means of high-resolution multi-channel seismic data. Each sequence consists predominantly of up to 100 km long and some 10 m thick forced regression systems tracts. The internal reflection pattern of the regressive units show mainly prograding oblique clinoforms. Intervening transgressive systems tracts are represented by seismically transparent or chaotic layers. On the outer shelf three of the sequences cause shelf aggradation and retrogradation, and two of them cause mainly shelf progradation. Based on the hierarchy of systems tracts, their calibration by comparison with eustatic sea-level curves and reconstructed paleoshoreline positions the composite sequences are interpreted as eccentricity driven eustatic 4th order (Milankovitch) cycles with a periodicity of about 100 ky. Internal unconformities mark cycles of 5th or higher order. An average subsidence of the outer shelf is estimated to be less than 0.4 mm/year during the last 345 ky. The correlation between the shelf growth pattern and sea-level fluctuations is consistent with the enhanced deposition on the eastern Bengal submarine fan from 465 to 125 ky B.P., as was observed by other authors. [Copyright &y& Elsevier]

Abstract: New multichannel seismic and bathymetric data are presented, which clarify the Plio-Quaternary evolution of the northern Gulf of Aqaba (Elat) and the Dead Sea Transform (DST). The seismic data reveal two main seismic sequences, a lower (pretectonic) and an upper (syntectonic) unit, separated by a prominent unconformity. These units are each linked to a distinct tectonic phase in the history of the DST. Parallel horizons and an undisturbed internal structure point to a tectonic quite time or pure strike-slip without extension or compression during the first (pretectonic) phase. The second (syntectonic) phase, which begins in the early Pliocene, is characterized by a major change in the activity of the DST. The pretectonic sedimentary unit subsided and, consequently, dips southward with a supplementary inclination to the east. The coeval sedimentation of the syntectonic unit is recorded by the divergent reflection pattern and onlap terminations on the unconformity. The apparent fault system seems to be rearranged in the second phase. The stepover of the main strand of the DST from the eastern side of the Elat Deep to the western side of the northern Gulf of Aqaba was mapped in detail for the first time. The very smooth shape of the stepover and the apparent lack of extensional tectonics do not fit with the classical pull-apart basin model for the Elat Deep and point to a decoupling of the crystalline basement from the sedimentary overburden. Comparisons of the new geophysical findings with analog models support this assertion. [Copyright &y& Elsevier]

Active seismic investigations along the Pacific margin off Peru were carried out using ocean bottom hydrophones and seismometers. The structure and theP-wave velocities of the obliquely subducting oceanic Nazca Plate and overriding South American Plate from 8°S to 15°S were determined by modelling the wide-angle seismic data combined with the analysis of reflection seismic data. Three detailed cross-sections of the subduction zone of the Peruvian margin and one strike-line across the Lima Basin are presented here.The oceanic crust of the Nazca Plate, with a thin pelagic sediment cover, ranging from 0–200 m, has an average thickness of 6.4 km. At 8°S it thins to 4 km in the area of Trujillo Trough, a graben-like structure. Across the margin, the plate boundary can be traced to 25 km depth. As inferred from the velocity models, a frontal prism exists adjacent to the trench axis and is associated with the steep lower slope. Terrigeneous sediments are proposed to be transported downslope due to gravitational forces and comprise the frontal prism, characterized by low seismicP-wave velocities. The lower slope material accretes against a backstop structure, which is defined by higher seismicP-wave velocities, 3.5–6.0 km s−1. The large variations in surface slope along one transect may reflect basal removal of upper plate material, thus steepening the slope surface. Subduction processes along the Peruvian margin are dominated by tectonic erosion indicated by the large margin taper, the shape and bending of the subducting slab, laterally varying slope angles and the material properties of the overriding continental plate. The erosional mechanisms, frontal and basal erosion, result in the steepening of the slope and consequent slope failure. [ABSTRACT FROM AUTHOR]

The Christiana-Santorini-Kolumbo volcanic field (CSKVF) in the Aegean Sea is one of the most active volcano-tectonic lineaments in Europe. Santorini has been an iconic site in volcanology and archaeology since the 19th century, and the onshore volcanic products of Santorini are one of the best-studied volcanic sequences worldwide. However, little is known about the chronology of volcanic activity of the adjacent submarine Kolumbo volcano, and even less is known about the Christiana volcanic island. In this study, we exploit a dense array of highresolution marine seismic reflection profiles to link the marine stratigraphy to onshore volcanic sequences and present the first consistent chronological framework for the CSKVF, enabling a detailed reconstruction of the evolution of the volcanic rift system in time and space. We identify four main phases of volcanic activity, which initiated in the Pliocene with the formation of the Christiana volcano (phase 1). The formation of the current southwest-northeast-trending rift system (phase 2) was associated with the evolution of two distinct volcanic centers, the newly discovered Poseidon center and the early Kolumbo volcano. Phase 3 saw a period of widespread volcanic activity throughout the entire rift. The ongoing phase 4 is confined to the Santorini caldera and Kolumbo volcano. Our study highlights the fundamental tectonic control on magma emplacement and shows that the CSKVF evolved from a volcanic field with local centers that matured only recently to form the vast Santorini edifice. [ABSTRACT FROM AUTHOR]

Abstract The S. Jorge Island in the Azores lies on a peculiar setting, the southern shoulder of the Terceira Rift (TR), which raises a series of questions that we address in this study. We first established the main volcanic stratigraphy by recognizing, in the field, the main unconformities/discontinuities and their meaning (major erosion surfaces and faults), then we collected critical samples, and finally dated them by K/Ar to calibrate the stratigraphy and the age of inferred large-scale flank collapses. Based on field, geochronological and marine geophysical data: (1) we found much older rocks in S. Jorge than in previous studies (ca. 1.85 Ma), and established a new volcanic stratigraphy (from bottom to top): Old Volcanic Complex (ca. 1.9–1.2 Ma), cropping out in the eastern third of the island; Intermediate Volcanic Complex (ca. 0.8–0.2 Ma), cropping out in the western two thirds of the island and separated from the underlying complex by a major fault; Young Volcanic Complex (

Abstract: We present a finite element-based dynamic modeling study of the recent stress conditions within the North German Basin, which is part of the Central European Basin System, based on geological, geophysical and geomorphological data. After compilation and evaluation of existing data, thin shell modeling is applied to understand the recent structural evolution of the Central European Basin System (CEBS) and its transition towards the Baltic Shield. In contrast to previous modeling approaches, we include a complex pattern of major faults from the Alpine Front to the Sorgenfrei–Tornquist Zone (STZ) and GPS measured residual velocities to define the boundary conditions of the model. Major deviations of the stresses occur along strong contrasts in the lithospheric structure and influence the stress pattern significantly. High intraplate compression is a responsible large-scale reactivation of the faults associated with the pre-existing basin framework in northern Central Europe, with an important record on vertical motions. The modeled slip/subsidence rates of the faults in the North German Basin are in the order of 0.01 and 0.2 mm year−1, which are in accordance with field observations, because no fault exhibits large Quaternary displacement rates in the study area. [Copyright &y& Elsevier]

The tectonic plate under the eastern Mediterranean Sea shows a remarkable variability as it comprises Earth's oldest oceanic lithosphere as well as the transition towards continental lithosphere beneath the Levant Basin. Its thickness and other properties offer essential information on the lithospheric evolution but have been difficult to determine seismically due to the high heterogeneity of the region and its complex crustal structure. Here, we combine a large, new surface wave dataset with published wide-angle data in order to determine lithospheric properties in the eastern Mediterranean. Our stochastic inversions of broad-band, phase-velocity dispersion measurements resolve the crust-mantle structural trade-offs and yield robust, 1-D shear-wave velocity models down to 300 km depth beneath the Ionian and Levant Basins. The thickness of the crust beneath the two locations is 16.4 ± 3 km and 22.3 ± 2 km, respectively. The Poisson's ratio (σ) of 0.32 and V p / V s of 1.93 in the crystalline crust confirm the presence of serpentinized oceanic crust beneath the Ionian Basin. Beneath the Levant Basin, low crustal V p / V s (∼ 1.7) and Poisson's (∼ 0.24) ratios indicate continental crust. Beneath the Ionian Basin, the lithosphere is about 180 km thick. By contrast, thin, 75 km thick lithosphere is found beneath the Levant Basin. S-velocity tomography based on surface wave data also shows thick, spatially variable oceanic mantle lithosphere beneath the eastern Mediterranean. Thickness of the oceanic lithosphere increases eastwards from the Triassic Ionian towards the Permo-Carboniferous lithosphere in the Central Eastern Mediterranean. These results demonstrate that oceanic lithosphere can thicken by cooling substantially beyond the limits suggested by the plate cooling model. Beneath the eastern Herodotus oceanic Basin, lithospheric thickness is decreasing to about 180 km. Thin continental lithosphere and shallow asthenosphere are present beneath the Dead Sea Fault, demonstrating that the localization of the lithospheric deformation and crustal seismicity along the fault correlates spatially with the thinning of the underlying continental lithosphere. • Crust and mantle lithospheric structures beneath the eastern Mediterranean Sea are resolved from the joint inversion of surface wave measurements and wide-angle refraction seismics. • Vp/Vs and Poisson's ration estimates point to the presence of serpentinized oceanic crust beneath the Ionian Basin and thinned continental crust beneath the Levant Basin. • Oceanic lithosphere in the eastern Mediterranean Sea consists of three different domains: a) 180 km thick, Triassic Ionian lithosphere, b) 200 km thick, Permo-Carboniferous lithosphere beneath the Central Eastern Mediterranean and c) 180 km thick lithosphere beneath the eastern Herodotus Basin. • Thin continental lithosphere (75 km thick) beneath the Levant Basin underlain by the shallow Middle East Asthenosphere. • The spatial correlation between the shallow Middle East Asthenosphere and the Dead Sea Fault reveals focusing of lithospheric deformation in an area of thinned lithosphere. [ABSTRACT FROM AUTHOR]

The Azores Plateau is an active magmatic region in the Central North Atlantic Ocean. In this study, we present a comprehensive data set of major element compositions and 87Sr/86Sr ratios of pore waters from surface sediments (0–9 mbsf) of the Azores Plateau. Based on distinct geochemical signatures we can separate normal marine from hydrothermally affected sediments. Normal marine sediments can further be differentiated by their ash content. Pore waters of ash rich gravity cores (GCs) do not show any deviations from seawater values except of a minor increase in Sr. In contrast, ash poor GCs generally show a trend for decreasing Ca with increasing depth, accompanied by a minor SO 4 decrease and a more pronounced Sr increase. We suggest that these deviations are caused by processes such as anaerobic oxidation of methane and carbonate recrystallization. At four additional sample locations we observed a decrease in Mg and SO 4 accompanied by a Ca increase in the pore waters, a pattern typical for hydrothermal fluids. The existence of hydrothermal systems in this region are corroborated by multi-channel seismic data, suggesting that sill or dyke intrusions are present in the subsurface close to the core locations. Overall, our observations offer preliminary indications for the existence of submarine hydrothermal systems on the Azores Plateau away from the Mid- Atlantic Ridge. • Overview on geochemical composition of pore water and solid phase of sediments on the Azores Plateau. • Evidence for deep marine hydrothermal activity on the Azores Plateau. • Pore water data suggest ongoing anaerobic oxidation of methane and carbonate recrystallization. [ABSTRACT FROM AUTHOR]

To investigate the history of the Aare Glacier and its overdeepened valley, a high-resolution multibeam bathymetric dataset and a 2D multi-channel reflection seismic dataset were acquired on perialpine Lake Thun (Switzerland). The overdeepened basin was formed by a combination of tectonically predefined weak zones and glacial erosion during several glacial cycles. In the deepest region of the basin, top of bedrock lies at ∼200 m below sea level, implying more than 750 m of overdeepening with respect to the current fluvial base level (i.e. lake level). Seismic stratigraphic analysis reveals the evolution of the basin and indicates a subaquatic moraine complex marked by high-amplitude reflections below the outermost edge of a morphologically distinct platform in the southeastern part of the lake. This stack of seven subaquatic terminal moraine crests was created by a fluctuating, “quasi-stagnant” grounded Aare Glacier during its overall recessional phase. Single packages of overridden moraine crests are seismically distuinguishable, which show a transition downstream into prograding clinoforms with foresets at the ice-distal slope. The succession of subaquatic glacial sequences (foresets and adjacent bottomsets) represent one fifth of the entire sedimentary thickness. Exact time constraints concerning the deglacial history of the Aare Glacier are very sparse. However, existing 10 Be exposure ages from the accumulation area of the Aare Glacier and radiocarbon ages from a Late-Glacial lake close to the outlet of Lake Thun indicate that the formation of the subaquatic moraine complex and the associated sedimentary infill must have occurred in less than 1000 years, implying high sedimentation rates and rapid disintegration of the glacier. These new data improve our comprehension of the landforms associated with the ice-contact zone in water, the facies architecture of the sub- to proglacial units, the related depositional processes, and thus the retreat mechanisms of the Aare Glacier. [ABSTRACT FROM AUTHOR]

New bathymetric and seismic reflection data from the Santorini–Amorgos Tectonic Zone in the southern Cyclades have been analysed and a description of the morphology and tectonic structure of the area has been presented. The basins of Anhydros, Amorgos and Santorini–Anafi have been distinguished together with the intermediate Anhydros Horst within the NE-SW oriented Santorini–Amorgos Tectonic Zone which has a length of 60–70 km and a width of 20–25 km. The basins represent tectonic grabens or semi-grabens bordered by the active marginal normal faults of Santorini–Anafi, Amorgos, Ios, Anhydros and Astypalaea. The Santorini–Anafi, Amorgos and Ios marginal faults have their footwall towards the NW where Alpine basement occurs in the submarine scarps and their hangingwall towards the southeast, where the Quaternary sediments have been deposited with maximum thickness of 700 m. Six sedimentary Units 1–6 have been distinguished in the stratigraphic successions of the Santorini–Anafi and the western Anhydros Basin whereas in the rest area only the upper four Units 3–6 have been deposited. This shows the expansion of the basin with subsidence during the Quaternary due to ongoing extension in a northwest-southeast direction. Growth structures are characterized by different periods of maximum deformation as this is indicated by the different sedimentary units with maximum thickness next to each fault. Transverse structures of northwest-southeast direction have been identified along the Santorini–Amorgos Tectonic Zone with distinction of the blocks/segments of Santorini, Anhydros/Kolumbo, Anhydros islet and Amorgos. Recent escarpments with 7–9 m offset observed along the Amorgos Fault indicate that this was activated during the first earthquake of the 7.5 magnitude 1956 events whereas no recent landslide was found in the area that could be related to the 1956 tsunami. [ABSTRACT FROM AUTHOR]

In the vicinity of Lake Thun at the front of the Bernese Alps (Switzerland), we performed a multidisciplinary neotectonic study combining onshore and offshore geological data and geophysical measurements in order to identify potentially active fault structures. Paleoseismic reconstructions on the northern margin of the Alps have documented several strong earthquakes with moment magnitudes ≥6 during the Late Quaternary, which have long recurrence intervals of 1,000 to 2,000 years. Such earthquakes are expected to produce surface ruptures. In this light, we investigated the study area located near Lake Thun primarily for on-fault evidence, to date still a shortcoming in Switzerland. We detected several features indicating potential fault activity, such as aligned subaquatic morphological depressions, offset horizons observed in reflection seismic profiles of lake sediments and in ground-penetrating radar images, all delineating a fault trace. Observations of fluvial deposits in a nearby gravel pit in the prolongation of the inferred structure supports these findings. A narrow zone with rotated long axes of pebbles (inclining at ∼60°) is clearly distinguishable and crosscuts the original bedding with predominantly horizontal orientation of pebble axes. This zone further shows an apparent 1.1 m offset of oxidized horizons and is therefore considered as a potential fault plane in a normal faulting regime. A dated radiocarbon age of ∼11,000 years BP of the gravel deposits hence suggests a younger fault activity during the Holocene. The Einigen Fault Zone (EFZ), proposed on the basis of these observations, is considered as a complex fault system with a combination of dextral strike-slip and normal faulting, as suggested by GPR images. Observations in the gravel pit and radar data independently show that it includes at least two fault strands. However, while five earthquakes with epicentral intensities I 0 ≥ VI and numerous smaller seismic events are known within less than 30 km epicentral distance to Lake Thun over the past 400 years, none of these seem to coincide with the location of the EFZ. [ABSTRACT FROM AUTHOR]

The evolution of volcanic islands is generally marked by fast construction phases alternating with destruction by a variety of mass-wasting processes. More specifically, volcanic islands located in areas of intense regional deformation can be particularly prone to gravitational destabilisation. The island of S. Miguel (Azores) has developed during the last 1 Myr inside the active Terceira Rift, a major tectonic structure materializing the present boundary between the Eurasian and Nubian lithospheric plates. In this work, we depict the evolution of the island, based on high-resolution DEM data, stratigraphic and structural analyses, high-precision K–Ar dating on separated mineral phases, and offshore data (bathymetry and seismic profiles). The new results indicate that: (1) the oldest volcanic complex (Nordeste), composing the easternmost part of the island, was dominantly active between ca. 850 and 750 ka, and was subsequently affected by a major south-directed flank collapse. (2) Between at least 500 ka and 250 ka, the landslide depression was massively filled by a thick lava succession erupted from volcanic cones and domes distributed along the main E-W collapse scar. (3) Since 250 kyr, the western part of this succession (Furnas area) was affected by multiple vertical collapses; associated plinian eruptions produced large pyroclastic deposits, here dated at ca. 60 ka and less than 25 ka. (4) During the same period, the eastern part of the landslide scar was enlarged by retrogressive erosion, producing the large Povoação valley, which was gradually filled by sediments and young volcanic products. (5) The Fogo volcano, in the middle of S. Miguel, is here dated between ca. 270 and 17 ka, and was affected by, at least, one southwards flank collapse. (6) The Sete Cidades volcano, in the western end of the island, is here dated between ca. 91 and 13 ka, and experienced mutliple caldera collapses; a landslide to the North is also suspected from the presence of a subtle morphologic scar covered by recent lava flows erupted from alignments of basaltic strombolian cones. The predominance of the N150° and N75° trends in the island suggest that the tectonics of the Terceira Rift controlled the location and the distribution of the volcanism, and to some extent the various destruction events. [ABSTRACT FROM AUTHOR]

Abstract: The Maldives, a 900 km north-south trending paired chain of atolls that surround a ca. 100 km wide central basin (the Inner Sea) represent a giant isolated carbonate platform in the Indian Ocean. New reflection seismic, multibeam and acoustic Doppler current profiler data show that its development exhibits a distinct change from sea-level to mainly bottom current-controlled sedimentation at the end of the Middle Miocene. The post-Middle Miocene intra-basinal fill consists of 9 mega units that have been formed and shaped by strong bottom currents, entering the Inner Sea between the inter-atoll passages. At the end of the Middle Miocene the Maldives represent a rimmed platform with the Inner Sea forming an empty bucket. A connection to the Indian Ocean existed only in the northeastern part of the platform, namely the Kardiva Channel. Probably concomitant with the onset of the Indian Monsoon, the current pattern around the Maldives changed significantly resulting in the formation of channels in the rimmed platform margin. The latter process was encouraged by local drowning of large platform parts and additionally, by bottom current forced submarine erosion that widened the channels to passages disintegrating the platform into separated atolls of different sizes. The reworked material was dumped into the Inner Sea where it formed large contourite fans. Along-slope bottom currents entering the Inner Sea from the north further redistributed the material leading to a southward shift of these sedimentary bodies. In this way the Inner Sea was filled from west to east (mega units 1–5). Starting with mega unit 6 the opening of a southern gateway introduced a prominent northward flow of bottom waters in the Inner Sea. It leads to the deposition of giant elongated drifts at the eastern flank of the basin, filling it from east to west. Because the current swept away most of the material around the atolls, the system was not able to prograde and the steady subsidence was compensated by aggradation. Accordingly, a fundamental characteristic of a current-controlled carbonate system is that aggradation occurs irrespective of platform sediment export or differently worded the rate of change in accommodation is always positive and greater than the rate of sediment supply. ADCP measurements in the winter monsoon season show two water masses in the Inner Sea, one at the surface 0–150 m and a second below it that reaches its sea-floor. By the use of the grain size distribution of ODP leg 716 located in the Inner Sea as proxy for the flow intensity of the bottom water, we recognized an inverse proportional relationship to the monsoon strength from late Upper Miocene to present. Some of the current-controlled deposits form sigmoidal prograding clinoforms, preferably at the edges of the atolls adjacent to the passages, where the velocity of the current entering the Inner Sea is high. The anatomy of these prograding wedges is similar to sea-level controlled clinoforms described for large isolated carbonate platforms in the sequence stratigraphic concept; however our results document, that they are not influenced by sea-level fluctuations. Because of the high current velocities involved in their deposition, they predominately consist of coarse sand sized carbonate fragments exhibiting large pore space and high permeability. Therefore these drift deposits comprise a possible exploration target. [Copyright &y& Elsevier]

Abstract: By means of new high-resolution Parasound, multi-channel reflection seismic and multibeam swath bathymetry data, we provide new insight into the sedimentation processes at the margin of a cool-water carbonate ramp system off southwestern Mallorca Island, western Mediterranean Sea. Here, we mapped 7 depositional units which we tied to the Messinian unconformity. The oldest units (1–3) are deposited from late Messinian to late Pliocene during phases of extreme sea-level fluctuations. 2.4Ma ago with the global climate cooling, when the estuarine water mass circulation switched into an anti-estuarine pattern in the Mediterranean Sea and sea-level highstands reached the today level, bottom currents started to shape the distal deposits of the cool-water carbonate system off southwestern Mallorca, represented by depositional units 4–7. Although, sediment supply from the carbonate shelf to the slope is low due to the insignificant input of terrigenous clastics and slow reef growth, slope sediments reach thicknesses >140m. Our study displays that the accumulation of sediments at the southwestern insular margin was mainly controlled by long-lived bottom currents and giant submarine landslides. The bottom currents formed elongated mounded drifts that contemporaneously developed in alongslope and upslope direction. They are probably controlled by an isobath-parallel bottom current in a present water depth of 350–550m which we associate with the Levantine Intermediate Water (LIW); and an upslope current acting in 250–600m associated with the Algerian mesoscale gyres that enter the Balearic straits from SE. Several scarps at the present sea-floor indicate the predominance of slope failures in the study area. Additionally, mass transport deposits occur basinwards in almost all depositional units. Accordingly, giant mass wasting events took place from the Pliocene into recent times. Locally, above the alongslope drift a field of sediment waves occurs in a water depth of 170–310m. They are oriented slightly oblique to the contour lines with their steep flank facing upslope, showing wavelengths of 400–800m and heights of 10–15m. We suggest that the waves migrate in upslope direction perpendicular to the main isobath-parallel flow. Furthermore, the results of this study indicate that sea-level fluctuations have only a minor influence on drift deposition; instead submarine landslides caused the creation of new drift units. They significantly altered the relief of the sea-floor and thereby initiate the realignment of the prevailing current pattern. The fault scarps and detachment surfaces left behind were the nucleolus for the development of new drift units. [Copyright &y& Elsevier]

Abstract: High-resolution seismic data from the Middle Bengal Fan were analysed to study the architecture of the fan in the vicinity of the active channel–levee system and to evaluate channel behaviours. The upper 600m column of the fan in the study area reveal a pattern of different sized channel–levee systems and high amplitude reflection packets (HARPS) of varying thicknesses, no mass-flow deposits or hemipelagic drapes are found. Within the channel–levee systems, units of chaotic high amplitude reflectors (CHARS), which represent aggraded and migrated channel axes, as well as abandoned channel-fill deposits appear. All channels are characterised by erosional incision into underlying deposits. Within the active channel–levee system, numerous cut-off loops are found showing a broad spectrum of complex behaviours with different ratios of vertical aggradation and lateral migration. As a difference to the Amazon Fan, the floors of all cut off loops and the active channel are not elevated above the surrounding seafloor, which may lead to such a long lifetime resulting in the large number of cut-off loops. In contrast, a detailed studied buried system shows no cut-off loops and is characterised by a more simple behaviour: a first phase of lateral migration is followed by a second phase of simultaneous vertical aggradation and lateral migration, which finally elevated the channel floor above the level of the surrounding seafloor. These architectural differences between the systems indicate that different loaded turbidity currents have built up both systems. The aggrading and migrating channel floors likely have reservoir potential, but a high-resolution 3D seismic survey and drilling are necessary for final proof. [Copyright &y& Elsevier]