ALBERT

Description: The basement of the Vera and Huercal Overa basins (southeastem Betics) is fonned by rocks ofthe Alboran Crustal Domain; a terrain which collided with the South-Iberian and Maghrebian continentalmargins in the Lower Miocene, resulting in the fonnation of the Gibraltar Are mountain chain. The Alpuja1Tide complex which occupies an intermediate structural position within the Alboran Domain, above the Nevado-Filabride and below the Malaguide complexes, includes at least three tectonic units in the southeastern Betics. From bottom to top in the slTuctural sequence, these units are Almagro, Almanzora and Variegato. The metapelitic rocks of these units show significative differences in their tectonic fabrics and in their P-T metamorphic paths. The lower Almagro unit underwent low-P/low-T metamorphism (300 oc and 3-4 kbar) and its metapelites are slates with no differentiated metamorphic fabric, which show two sets of spaced axial-plane cleavages. The intennediate Almanzora unit has two differentiated metamorphic fabrics. The oldest foliation (S,) preserved in quartz-rich domains of a crenulation cleavage (S ce) grew during high-P/low-T metamorphism (between 300 °C/12 kbar and 350 oC/6 kbar). The Scc cleavage deyeloped after an isobaric heating to 475 oc at 5 kbar and registers an initial isothennal decompression to 475 oc at 3 kbar followed by cooling to 300 oc at 2 kbar. A brittle spaced cleavage axial plane to N-vergent asymmetric folM cuts the S ce fabtic. At the top ofthe Alpujarride tectonic pile the Variegato unit, includes up to tlu·ee imbrications formed from top to bottom by gamet schists, fine"grained schists and Triassic carbonates. The main Scc foliation in the gamet schists grew during a nearly isothennal decompression between 500 oc at 8 kbar and 525 oc at 2 kbar. In the Variegato dark schists, the spaced crenulation cleavage associated to Nvergent folds is defined by muscovite and chlorite lepidoblasts and is overprinted by the growth of andalousite porphyroblasts. This assemblage equilibrated at 450-460 oc at 2 kbar. The Variegato fine-grained schists include a high-P/low-T Mg-carpholite-bearing assemblage, within pre-Scc quartz veins equilibrated at 8-10 kbar and approximately 400 °C. Furthermore, a chlorite + phengite + quartz assemblage defining the se relic foliation in lenticular domains of the scc cleavage shows local equilibria at 11 to 9 kbar at 400 °C. The superposition ofthese units was related with N-directed compressional brittle-ductile shear zones and associated N-vergent asymmetric folds, which were active at a late stage of the metamorphic evolution after coaxial ductile flattening of the Variegato and Almanzora units. The thrust pile that resulted from this late compressional event was later thinned by two consecutive brittle extensional systems with northward and southwestward tectonic transport. Final! y, these metamorphic rocks were exhumed to the surface in the core of E-W oriented anticlinal ridges, which developed during the Upper Neogene and the Quaternary. Folding and strike-slip faulting of the Miocene Alboran basin produced the present basin and range morphology of the southeastern Betics, which is characterised by the formation of isolated sedimentary basins in the synclines.

Description: We have analysed the thermobarometric equilibrium conditions reached during local equilibria among phengite + chlorite + quartz + water ± chloritoid ± garnet assemblages found in metapelites of the Ragua unit, the structurally-lowest tectonic unit outcropping in the Betics hinterland (southern Spain). Porphyroblast- deformation relationships show that lenticular domains preserved within the main foliation in the metapelites grew during a HP/LT prograde metamorphic event with thermal conditions of 320-450 °C and 12-14 kbar pressure. Hence, the Ragua unit subducted in a continental accretionary-wedge context, undergoing a tectonic evolution parallel to the one followed by the two other overlying Nevado-Filabride units.

Description: Highlights • We review the knowledge on modern high-latitude planktic foraminifers. • Subpolar species currently invade higher latitudes. • Climate change affects phenology, seawater pH, and carbon turnover. • Modern planktic foraminifers are briefly discussed for their paleoceanographic significance. Abstract Planktic foraminifers can be sensitive indicators of the changing environment including both the Arctic Ocean and Southern Ocean. Due to variability in their ecology, biology, test characteristics, and fossil preservation in marine sediments, they serve as valuable archives in paleoceanography and climate geochemistry over the geologic time scale. Foraminifers are sensitive to, and can therefore provide proxy data on ambient water temperature, salinity, carbonate chemistry, and trophic conditions through shifts in assemblage (species) composition and the shell chemistry of individual specimens. Production and dissolution of the calcareous shell, as well as growth and remineralization of the cytoplasm, affect the carbonate counter pump and to a lesser extent the soft-tissue pump, at varying regional and temporal scales. Diversity of planktic foraminifers in polar waters is low in comparison to lower latitudes and is limited to three native species: Neogloboquadrina pachyderma, Turborotalita quinqueloba, and Globigerina bulloides, of which N. pachyderma is best adapted to polar conditions in the surface ocean. Neogloboquadrina pachyderma hibernates in brine channels in the lower layers of the Antarctic sea ice, a strategy that is presently undescribed in the Arctic. In open Antarctic and Arctic surface waters T. quinqueloba and G. bulloides increase in abundance at lower polar to subpolar latitudes and Globigerinita uvula, Turborotalita humilis, Globigerinita glutinata, Globorotalia inflata, and Globorotalia crassaformis complement the assemblages. Over the past two to three decades there has been a marked increase in the abundance of Orcadia riedeli and G. uvula in the subpolar and polar Indian Ocean, as well as in the northern North Atlantic. This paper presents a review of the knowledge of polar and subpolar planktic foraminifers. Particular emphasis is placed on the response of foraminifers to modern warming and ocean acidification at high latitudes and the implications for data interpretation in paleoceanography and paleoclimate research.

Description: Highlights • Deep-sea mineral exploration and exploitation licenses have been issued recently. • Mining will modify the abiotic and biotic environment. • At directly mined sites, species are removed and cannot resist disturbance. • Recovery is highly variable in distinct ecosystems and among benthic taxa. • Community changes may persist over geological time-scales at directly mined sites. Abstract With increasing demand for mineral resources, extraction of polymetallic sulphides at hydrothermal vents, cobalt-rich ferromanganese crusts at seamounts, and polymetallic nodules on abyssal plains may be imminent. Here, we shortly introduce ecosystem characteristics of mining areas, report on recent mining developments, and identify potential stress and disturbances created by mining. We analyze species’ potential resistance to future mining and perform meta-analyses on population density and diversity recovery after disturbances most similar to mining: volcanic eruptions at vents, fisheries on seamounts, and experiments that mimic nodule mining on abyssal plains. We report wide variation in recovery rates among taxa, size, and mobility of fauna. While densities and diversities of some taxa can recover to or even exceed pre-disturbance levels, community composition remains affected after decades. The loss of hard substrata or alteration of substrata composition may cause substantial community shifts that persist over geological timescales at mined sites.

Description: Highlights • New multiscale seismic data of the Carboneras Fault Zone (CFZ). • The tectonic architecture and depth geometry of the Carboneras Fault is examined. • We characterise fault segments and sub-segments to estimate their seismic potential. • The basement plays a key role in the actual configuration of the fault. • We explore CFZ terminations to know how strain is transferred to nearby structures. Abstract In the SE Iberian Margin, which hosts the convergent boundary between the European and African Plates, Quaternary faulting activity is dominated by a large left-lateral strike–slip system referred to as the Eastern Betic Shear Zone. This active fault system runs along more than 450 km and it is characterised by low to moderate magnitude shallow earthquakes, although large historical events have also occurred. The Carboneras Fault is the longest structure of the Eastern Betic Shear Zone, and its southern termination extends further into the Alboran Sea. Previously acquired high-resolution data (i.e. swath-bathymetry, TOBI sidescan sonar and sub-bottom profiler) show that the offshore Carboneras Fault is a NE–SW-trending upwarped zone of deformation with a length of 90 km long and a width of 0.5 to 2 km, which shows geomorphic features typically found in subaerial strike–slip faults, such as deflected drainage, pressure ridges and “en echelon” folds. However, the neotectonic, depth architecture, and Neogene evolution of Carboneras Fault offshore are still poorly known. In this work we present a multiscale seismic imaging of the Carboneras Fault (i.e. TOPAS, high-resolution multichannel-seismic reflection, and deep penetration multichannel-seismic reflection) carried out during three successive marine cruises, from 2006 to 2010. The new dataset allowed us to define a total of seven seismostratigraphic units (from Tortonian to Late Quaternary) above the basement, to characterise the tectonic architecture and structural segmentation of the Carboneras Fault, and to estimate its maximum seismic potential. We finally discuss the role of the basement in the present-day tectonic evolution of the Carboneras Fault, and explore the northern and southern terminations of the fault and how the strain is transferred to nearby structures.

Description: An important tool for deep-sea temperature reconstruction is Mg/Ca paleothermometry applied to benthic foraminifera. Foraminifera of the genus Melonis appear to be promising candidates for temperature reconstructions due to their wide geographical and bathymetric distribution, and their infaunal habitat, which was suggested to reduce secondary effects from carbonate ion saturation (Δ[CO3 2−]). Here, we make substantial advances to previous calibration efforts and present new multi-lab Mg/Ca data for Melonis barleeanum and Melonis pompilioides from more than one hundred core top samples spanning in situ bottom temperatures from −1 to 16 °C, coupled with morphometric analyses of the foraminifer tests. Both species and their morphotypes seem to have a similar response of Mg/Ca to growth temperature. Compilation of new and previously published data reveals a linear dependence of temperature on Mg/Ca, with a best fit of Mg/Ca (mmol/mol) = 0.113 ± 0.005 ∗ BWT (°C) + 0.792 ± 0.036 (r2 = 0.81; n = 120; 1σ SD). Salinity, bottom water Δ[CO3 2−], and varying morphotypes have no apparent effect on the Mg/Ca-temperature relationship, but pore water Δ[CO3 2−] might have had an influence on some of the samples from the tropical Atlantic.

Description: Complex multifault earthquake ruptures involving secondary faults emphasize the necessity to characterize their seismogenic potential better and study their relationship with major faults to improve the seismic hazard assessment of a region. High-resolution geophysical data were interpreted to make a detailed characterization of the Averroes Fault and the North Averroes Faults, which are poorly known secondary right-lateral strike-slip faults located in the central part of the Alboran Sea (western Mediterranean). These faults appear to have evolved since the Pliocene as part of a distributed dextral strike-slip shear zone in response to local strain engendered by the diverging movement of the Carboneras Fault to the north, and the Yusuf and Alboran Ridge faults to the south. In addition, the architecture of these faults suggests that the Averroes Fault may eventually link with the Yusuf fault, thus leading to a higher seismogenic potential. Therefore, these secondary faults represent a hitherto unrecognized seismogenic hazard since they could produce earthquakes up to moment magnitude (Mw) 7.6. Our results highlight the importance of the role played by secondary faults in a specific kinematic framework. Their reciprocal linkage and their mechanical relationship with the main faults could lead to future complex fault ruptures. This information could improve fault source and earthquake models used in seismic and tsunami hazard assessment in this and similar regions.

Description: The surface of the solid Earth is effectively stress free in its subaerial portions, and hydrostatic beneath the oceans. Unfortunately, this type of boundary condition is difficult to treat computationally, and for computational convenience, numerical models have often used simpler approximations that do not involve a normal stress-loaded, shear-stress free top surface that is free to move. Viscous flow models with a computational free surface typically confront stability problems when the time step is bigger than the viscous relaxation time. The small time step required for stability (〈2. Kyr) makes this type of model computationally intensive, so there remains a need to develop strategies that mitigate the stability problem by making larger (at least ~10 Kyr) time steps stable and accurate. Here we present a new free-surface stabilization algorithm for finite element codes which solves the stability problem by adding to the Stokes formulation an intrinsic penalization term equivalent to a portion of the future load at the surface nodes. Our algorithm is straightforward to implement and can be used with both Eulerian or Lagrangian grids. It includes α and β parameters to respectively control both the vertical and the horizontal slope-dependent penalization terms, and uses Uzawa-like iterations to solve the resulting system at a cost comparable to a non-stress free surface formulation. Four tests were carried out in order to study the accuracy and the stability of the algorithm: (1) a decaying first-order sinusoidal topography test, (2) a decaying high-order sinusoidal topography test, (3) a Rayleigh-Taylor instability test, and (4) a steep-slope test. For these tests, we investigate which α and β parameters give the best results in terms of both accuracy and stability. We also compare the accuracy and the stability of our algorithm with a similar implicit approach recently developed by Kaus et al. (2010). We find that our algorithm is slightly more accurate and stable for steep slopes, and also conclude that, for longer time steps, the optimal α controlling factor for both approaches is ~2/3, instead of the 1/2 Crank-Nicolson parameter inferred from a linearized accuracy analysis. This more-implicit value coincides with the velocity factor for a Galerkin time discretization applied to our penalization term using linear shape functions in time.

Description: Highlights • Tiburon Basin sedimentology indicates continental shelfal setting. • Sequence stratigraphy denotes periodic sea-level rise and fall. • High-resolution chronology constrains the lower section between 4.2 Ma and 2.8 Ma. • The record is controlled in part by sea level change with orbital obliquity periods. • A 3.2–2.9 Ma high-amplitude sea level fall is linked to global climatic cooling. Abstract We present new findings from Pliocene marine sediments from the Mejillones Peninsula Tiburon Basin of the northern Chile continental margin that provide constraints for the global sea level record. Sedimentologic and sequence stratigraphic studies reveal facies associations of a continental shelf setting. Textural variations indicate that coarsening and fining up of the succession are due to relative sea level rise and fall, respectively. Magnetostratigraphy was integrated with bio- and tephro- stratigraphic data to construct a record of high-resolution chronology. The age model constrains the Tiburon Basin lower section between 4.2 Ma and 2.8 Ma. The record is likely to be controlled in part by sea level change with orbital periodicities of obliquity (∼ 40 ka of frequency) and, between 3.2 Ma and 2.9 Ma a high-amplitude sea level fall is correlated to global climatic deterioration and the onset of major Northern Hemisphere glaciations.

Description: Intense human activities facilitate the successful spread and establishment of non-indigenous aquatic organisms in marine and freshwater ecosystems. In some cases such intrusions result in noticeable and adverse changes in the recipient environments. In the Baltic Sea, the discovery and rapid initial spread of the North American wedge clam Rangia cuneata represents a new wave of invasion which may trigger unpredictable changes of the local benthic communities. In this study we present a species-specific DNA-based marker developed in silico and experimentally tested on environmental samples. Marker specificity and sensitivity were assessed in vitro from water samples containing different mixtures of the target species and other five bivalves currently present in the region: the native Cerastoderma glaucum, Macoma balthica and Mytilus trossulus, the invasive Dreissena polymorpha and the cryptogenic Mya arenaria. Cross-species amplification was not found in any case. The method allows to detecting at least 0.4 ng of Rangia cuneata DNA per μl, and 0.1 g of tissue per liter of water. Finally, the marker performance was assessed in water samples from the Baltic Sea and Vistula Lagoon. The coincidence between independent visual observations of Rangia cuneata and positive PCR amplification of the marker from the water samples confirmed the efficiency of this highly reproducible, fast, and technically easy method. Rangia cuneata traces can be detected from environmental DNA even when the population is sparse and small, enabling rapid management responses and allowing to track the invasion dynamics.