Deformation bands and alteration in porous glass-rich volcaniclastics: Insights from Milos, Greece

Deformation bands in porous volcaniclastics are little studied structural heterogeneities despite their relevance for constraining the modalities of deformation development and related fluid-rock interactions in volcanic areas. We document a dense network of normal-sense Deformation Bands (Normal-sense Compactional Shear Bands (NCSBs) affecting upper Pliocene felsic glassy tuffites in Milos, Greece. NCSBs probably formed between 300 and 500 m of burial depth, in response to NE-SW directed extension which is related to volcanic rift development in the area. They accommodate mm-to m-shear-offsets, trend either N105 ± 10° or N070 ± 10°, and show mutual cross-cutting relations. The NCSB fault rock is made of ultracataclasite in which the cataclastic mechanisms have affected both the mineral fraction and the volcanic glass. Minerals are fractured along their cleavages whereas pumices are interestingly fractured along their vesicles. The development of chemical alteration (dissolution and cementation) essentially into the ultracataclasite is expressed through glass-hosted corrosion gulfs and smectites filling the intergranular porosity. These observations support that NCSBs preferentially retained water, have been the seat of greater fluid flow, and are the locus of ongoing phyllosilicate self-sealing in the vadose zone. A significant decrease (up to one order of magnitude) in porosity is measured within the studied NCSBs

Surf zone hazards and injuries on beaches in SW France

Surf zone injuries (SZIs) are common worldwide, yet limited data is available for many geographical regions, including Europe. This study provides the first preliminary overview of SZIs along approximately 230 km of hazardous surf beaches in SW France during the summer season. A total of 2523 SZIs over 186 sample days during the summers of 2007, 2009 and 2015 were analysed. Documented injury data included date and time; beach location; flag colour; outside/inside of the bathing zone; age, gender, country and home postal code of the victim; activity; cause of injury; injury type and severity. Injuries sustained ranged from mild contusion to fatal drowning, including severe spinal injuries, wounds and luxation. While the most severe injuries (drowning) were related to rip currents, a large number of SZIs occurred as a result of shore-break waves (44.6%; n = 1125) and surfing activity (31.0%; n = 783) primarily inside and outside of lifeguard patrolled bathing zones, respectively. Victims were primarily French living more than 40 km from the beach (75.9% of the reported addresses; n = 1729), although a substantial number of victims originated from Europe (14.7% of the addresses reported; n = 335), including The Netherlands (44.2%; n = 148), Germany (26.3%; n = 88) and Belgium (12.5%; n = 49). The predominant age group involved in the incidents was between 10-25 years (54.5%; n = 1376) followed by 35-50 years (22.6%; n = 570), with the majority of SZIs involving males (69.6%, n = 1617). Despite the large predominance (74.1%; n = 33) of males involved in the most severe drowning incidents, all of which occurred outside the bathing zone, a surprisingly large proportion of females (48.0%; n = 133) experienced milder drowning incidents involving only minor to moderate respiratory impairment, peaking at 58.2% (n = 85) within the age group 10-25. The spine/cervical injury population is very young, with 58.5% (n = 313) within the age group 10-20. Specific injuries tended to occur in clusters (e.g. rip current drowning or shore-break injury) with particular days prone to rip-current drowning or hazardous shore-break waves, suggesting the potential to predict level of risk to beachgoers based on basic weather and marine conditions. This study calls for increased social-based beach safety research in France and the development of more effective public awareness campaigns to highlight the surf zone hazards, even within a supervised bathing zone. These campaigns should be targeted towards young males and females, in order to reduce the number of injuries and drownings occurring on beaches in SW France.Marier les objectifs de défense côtière avec ceux de la protection du milieu naturel grâce aux dunes sableuse

Basin tectonic history and paleo-physiography of the pelagian platform, northern Tunisia, using vitrinite reflectance data

Constraining the thermal, burial and uplift/exhumation history of sedimentary basins is crucial in the understanding of upper crustal strain evolution and also has implications for understanding the nature and timing of hydrocarbon maturation and migration. In this study, we use Vitrinite Reflectance (VR) data to elucidate the paleo‐physiography and thermal history of an inverted basin in the foreland of the Atlasic orogeny in Northern Tunisia. In doing so, it is the primary aim of this study to demonstrate how VR techniques may be applied to unravel basin subsidence/uplift history of structural domains and provide valuable insights into the kinematic evolution of sedimentary basins. VR measurements of both the onshore Pelagian Platform and the Tunisian Furrow in Northern Tunisia are used to impose constraints on the deformation history of a long‐lived structural feature in the studied region, namely the Zaghouan Fault. Previous work has shown that this fault was active as an extensional structure in Lower Jurassic to Aptian times, before subsequently being inverted during the Late Cretaceous Eocene Atlas I tectonic event and Upper Miocene Atlas II tectonic event. Quantifying and constraining this latter inversion stage, and shedding light on the roles of structural inheritance and the basin thermal history, are secondary aims of this study. The results of this study show that the Atlas II WNW‐ESE compressive event deformed both the Pelagian Platform and the Tunisian Furrow during Tortonian‐Messinian times. Maximum burial depth for the Pelagian Platform was reached during the Middle to Upper Miocene, i.e. prior to the Atlas II folding event. VR measurements indicate that the Cretaceous to Ypresian section of the Pelagian Platform was buried to a maximum burial depth of ~3 km, using a geothermal gradient of 30°C/km. Cretaceous rock samples VR values show that the hanging wall of the Zaghouan Fault was buried to a maximum depth of <2 km. This suggests that a vertical km‐scale throw along the Zaghouan Fault pre‐dated the Atlas II shortening, and also proves that the fault controlled the subsidence of the Pelagian Platform during the Oligo‐Miocene. Mean exhumation rates of the Pelagian Platform throughout the Messinian to Quaternary were in the order of 0.3 mm/year. However, when the additional effect of Tortonian‐Messinian folding is accounted for, exhumation rates could have reached 0.6-0.7 mm/year

The dismantling of the Apulian carbonate platform during the late Campanian – early Maastrichtian in Albania

© 2018 Elsevier Ltd The Apulian carbonate margin is widely preserved across the Adriatic domain and has been extensively studied in the south of Italy. In Albania, Oligocene–Pliocene fold-and-thrust tectonics led to widespread exposure of the Apulian Platform and associated Ionian Basin carbonates. However, the portion linking the platform to the basin is missing, preventing a direct reconstruction of the platform margin. Syn-sedimentary folding and faulting are recognized in the uppermost part of both the platform and basinal/slope series. Mass transport deposits (MTDs) occur within the platform succession incorporated into well-bedded intertidal (stromatolites) to shallow-subtidal (rudist packstones) sedimentary sequences. They display significant lateral variability which is accompanied by both rigid and soft deformation structures. Spectacular slumps made up of sediment density flow deposits are recognized in the adjacent Ionian Basin. The lateral extent of basal shear surfaces, syn-sedimentary faults and folds evidenced in the Ionian Basin points toward multiple regional tectonic triggering events affecting the Apulian Platform margin at that time. Bio- and chrono-stratigraphic analyses suggest that the triggers occurred during the late Campanian – early Maastrichtian. Beyond the obvious interest from a stratigraphic point of view, the study of these events recording the dismantling of the Apulian carbonate platform allows for a better understanding of the triggering mechanisms and the sedimentary characteristics of MTDs and slumps at a basinal scale.status: publishe

The dismantling of the Apulian carbonate platform during the late Campanian – early Maastrichtian in Albania

The Apulian carbonate margin is widely preserved across the Adriatic domain and has been extensively studied in the south of Italy. In Albania, Oligocene–Pliocene fold-and-thrust tectonics led to widespread exposure of the Apulian Platform and associated Ionian Basin carbonates. However, the portion linking the platform to the basin is missing, preventing a direct reconstruction of the platform margin. Syn-sedimentary folding and faulting are recognized in the uppermost part of both the platform and basinal/slope series. Mass transport deposits (MTDs) occur within the platform succession incorporated into well-bedded intertidal (stromatolites) to shallow-subtidal (rudist packstones) sedimentary sequences. They display significant lateral variability which is accompanied by both rigid and soft deformation structures. Spectacular slumps made up of sediment density flow deposits are recognized in the adjacent Ionian Basin. The lateral extent of basal shear surfaces, syn-sedimentary faults and folds evidenced in the Ionian Basin points toward multiple regional tectonic triggering events affecting the Apulian Platform margin at that time. Bio- and chrono-stratigraphic analyses suggest that the triggers occurred during the late Campanian – early Maastrichtian. Beyond the obvious interest from a stratigraphic point of view, the study of these events recording the dismantling of the Apulian carbonate platform allows for a better understanding of the triggering mechanisms and the sedimentary characteristics of MTDs and slumps at a basinal scale

Tectonism and volcanism forced by glaciation and deglaciation events in southern Iceland

International audienc

Tectonism and volcanism forced by glaciation and deglaciation events in southern Iceland

International audienc

Tectonism and volcanism forced by glaciation and deglaciation events in southern Iceland

International audienc

Carbonate slope morphology revealing a giant submarine canyon (Little Bahama Bank, Bahamas)

International audienceNew high-quality multibeam data detail the morphology of the giant 135-km-long Great Abaco Canyon (GAC) located between Little Bahama Bank (LBB, Bahamas) and Blake Plateau. Knickpoints, chutes, and plunge pools mark the canyon main axis, which is parallel to the LBB margin. The canyon head covers a large area but does not represent the main source of the modern sediments. The material supplied through the LBB canyon systems originates below this head, which only shows erosive lineaments related to the pathway of currents running along the seafloor and restricted failure scars. Most of the sediment supply originates from the canyon sides. The northern canyon flank incises the Blake Plateau, which comprises contourites on top of a drowned Cretaceous carbonate platform. These deposits are susceptible to translational slides and form dissymmetric debris accumulations along the northern edge of the canyon. A large tributary drains the Blake Plateau. Two large tributaries connecting the southern flank of the GAC directly to the LBB upper slope form additional sources of sediments. Subbottom profiles suggest the presence of a sedimentary levee on the tributary canyon and of sediment gravity flow deposits. The GAC has been a permanent structure since the drowning of the Cretaceous platform, and its size and morphology are comparable to those of canyons in siliciclastic environments. The orientation of the GAC parallel to large-scale regional tectonic structures suggests a structural control. The size of the observed structures, especially plunge pools at the base of gigantic chutes, is unusual on Earth. The presence of deposits downflow of the pools suggests that the GAC results from or at least is maintained by persistent and sustained submarine gravity flows rather than by retrogressive erosion