Chronostratigraphic framework at sites GeoB14403 and GeoB14414 from the Gela Basin, Sicily Channel

A multi-proxy chronological framework along with sequence-stratigraphic interpretations unveils composite Milankovitch cyclicity in the sedimentary records of the Last GlacialeInterglacial cycle at NE Gela Basin on the Sicilian continental margin. Chronostratigraphic data (including foraminifera-based eco-biostratigraphy and d18O records, tephrochronological markers and 14C AMS radiometric datings) was derived from the shallow-shelf drill sites GeoB14403 (54.6 m recovery) and GeoB14414 (27.5 m), collected with both gravity and drilled MeBo cores in 193 m and 146 m water depth, respectively. The recovered intervals record Marine Isotope Stages and Substages (MIS) from MIS 5 to MIS 1, thus comprising major stratigraphic parts of the progradational deposits that form the last 100-ka depositional sequence. Calibration of shelf sedimentary units with borehole stratigraphies indicates the impact of higher-frequency (20-ka) sea level cycles punctuating this 100-ka cycle. This becomes most evident in the alternation of thick interstadial highstand (HST) wedges and thinner glacial forced-regression (FSST) units mirroring seaward shifts in coastal progradation. Albeit their relatively short-lived depositional phase, these subordinate HST units form the bulk of the 100-ka depositional sequence. Two mechanisms are proposed that likely account for enhanced sediment accumulation ratios (SAR) of up to 200 cm/ka during these intervals: (1) intensified activity of deep and intermediate Levantine Intermediate Water (LIW) associated to the drowning of Mediterranean shelves, and (2) amplified sediment flux along the flooded shelf in response to hyperpycnal plumes that generate through extreme precipitation events during overall arid conditions. Equally, the latter mechanism is thought to be at the origin of undulated features resolved in the acoustic records of MIS 5 Interstadials, which bear a striking resemblance to modern equivalents forming on late-Holocene prodeltas of other Mediterranean shallow-shelf settings.

Spatial compartmentalization of free radical formation and mitochondrial heterogeneity in bivalve gills revealed by live-imaging techniques, supplementary material

Live-imaging techniques (LIT) utilize target-specific fluorescent dyes to visualize biochemical processes using confocal and multiphoton scanning microscopy, which are increasingly employed as non-invasive approach to physiological in-vivo and ex-vivo studies. Here we report application of LIT to bivalve gills for ex-vivo analysis of gill physiology and mapping of reactive oxygen (ROS) and nitrogen (RNS) species formation in the living tissue. Our results indicate that H2O2, HOO. and ONOO- radicals (assessed through C-H2DFFDA staining) are mainly formed within the blood sinus of the filaments and are likely to be produced by hemocytes as defense against invading pathogens. The oxidative damage in these areas is controlled by enhanced CAT (catalase) activities recorded within the filaments. The outermost areas of the ciliated epithelial cells composing the filaments, concentrated the highest mitochondrial densities (MTK Deep Red 633 staining) and the most acidic pH values (as observed with ageladine-a). These mitochondria have low (depolarized) membrane potentials (D psi m) (JC-1 staining), suggesting that the high amounts of ATP required for ciliary beating may be in part produced by non-mitochondrial mechanisms, such as the enzymatic activity of an ATP-regenerating kinase. Nitric oxide (NO, DAF-2DA staining) produced in the region of the peripheral mitochondria may have an effect on mitochondrial electron transport and possibly cause the low membrane potential. High DAF-2DA staining was moreover observed in the muscle cells composing the wall of the blood vessels where NO may be involved in regulating blood vessel diameter. On the ventral bend of the gills, subepithelial mucus glands (SMG) contain large mucous vacuoles showing higher fluorescence intensities for O2.- (DHE staining) than the rest of the tissue. Given the antimicrobial properties of superoxide, release of O2.- into the mucus may help to avoid the development of microbial biofilms on the gill surface. However, cells of the ventral bends are paying a price for this antimicrobial protection, since they show significantly higher oxidative damage, according to the antioxidant enzyme activities and the carbonyl levels, than the rest of the gill tissue. This study provides the first evidence that one single epithelial cell may contain mitochondria with significantly different membrane potentials. Furthermore, we provide new insight into ROS and RNS formation in ex-vivo gill tissues which opens new perspectives for unraveling the different ecophysiological roles of ROS and RNS in multifunctional organs such as gills.

Carbonat-free sediment components of ODP Leg 115 holes

From the equatorial Indian Ocean, carbonate-free portions of sediment samples of Paleocene to Miocene calcareous oozes and chalks from Sites 707, 709, and 711 were studied using X-ray diffraction measurements and the scanning electron microscope. Downhole variations in biogenic opal, quartz, barite, and clinoptilolite were investigated. The abundance patterns of these major mineral phases show several similarities and may be used for additional lithologic correlations. Variations in biogenic opal contents reflect biogenic silica productivity. Beside the general pattern, a succession in biogenic silica decrease through time is generally recorded since the Oligocene. This succession started earliest at northernmost Site 711 and latest at southernmost Site 707, including Site 709 within these two. Opal-A variations as well as the barite distribution may be influenced by the paleoposition of the sites in relation to the high-productivity zone, which today lies south of the equator. Authigenic clinoptilolite apparently formed in two different modes. In deeper sediment intervals, clinoptilolite was the last mineral phase formed associated with enhanced silica diagenesis. In late Oligocene to middle Miocene sediments, clinoptilolite was the only authigenic silica phase encountered where otherwise strong opal dissolution was observed. The sponge spicules showed special dissolution features probably related to microbiological activity. Silica concretions mainly composed of opal-CT and authigenic quartz occur in carbonate-rich environments and are formed during later diagenesis when burial depth causes the sediments to reach higher temperatures. Opal-CT concretions in carbonate-free siliceous oozes were found at Site 711 and are probably formed during an early stage of silica diagenesis.

Geochemistry of subducted volcaniclastic sediments from Mariana arc magmas

The phase relations of natural volcaniclastic sediments from the west Pacific Ocean were investigated experimentally at conditions of 3-6 GPa and 800-900 °C with 10 wt.% added H2O (in addition to ~ 10 wt.% structurally-bound H2O) to induce hydrous melting. Volcaniclastic sediments are shown to produce a sub-solidus assemblage of garnet, clinopyroxene, biotite, quartz/coesite and the accessory phases rutile ± Fe-Ti oxide ± apatite ± monazite ± zircon. Hydrous melt appears at temperatures exceeding 800-850 °C, irrespective of pressure. The melt-producing reaction consumes clinopyroxene, biotite and quartz/coesite and produces orthopyroxene. These phase relations differ from those of pelagic clays and K-bearing mid ocean ridge basalts (e.g. altered oceanic crust) that contain phengite, rather than biotite, as a sub-solidus phase. Despite their relatively high melt productivity, the wet solidus for volcaniclastic sediments is found to be higher (825-850 °C) than other marine sediments (700-750 °C) at 3 GPa. This trend is reversed at high-pressure conditions (6 GPa) where the biotite melting reaction occurs at lower temperatures (800-850 °C) than the phengite melting reaction (900-1000 °C). Trace element data was obtained from the 3 GPa run products, showing that partial melts are depleted in heavy rare earth elements (REE) and high field strength elements (HFSE), due to the presence of residual garnet and rutile, and are enriched in large ion lithophile elements (LILE), except for Sr and Ba. This is in contrast to previous experimental studies on pelagic sediments at sub-arc depths, where Sr and Ba are among the most enriched trace elements in glasses. This behavior can be partly attributed to the presence of residual apatite, which also host some light REE in our supra-solidus residues. Our new experimental results account for a wide range of trace element and U-series geochemical features of the sedimentary component of the Mariana arc magmas, including imparting a substantial Nb anomaly to melts from an anomaly-free protolith.

Summary of phase compositions of experimental silicate melt, un-normalised analyses

The solubility of Re and Au in haplobasaltic melt has been investigated at 1673-2573 K, 0.1 MPa-2 GPa and IW-1 to +2.5, in both carbon-saturated and carbon-free systems. Results extend the existing, low pressure and temperature, dataset to more accurately predict the results of metal-silicate equilibrium at the base of a terrestrial magma ocean. Solubilities in run-product glasses were measured by laser ablation ICP-MS, which allows for the explicit assessment of contamination by metal inclusions. The Re and Au content of demonstrably contaminant-free glasses increases with temperature, and shows variation with oxygen fugacity (fO2) similar to previous results, although lower valence states for Re (1+, 2+) are suggested by the data. At 2 GPa, and Delta IW of +1.75 to +2, the metal-silicate partition coefficient for Re (DMet/Sil) is defined by the relation LogD[met/sil][Re] = 0.50(±0.022)*10**4/T(K)+3.73(±0.095) For metal-silicate equilibrium to endow Earth's mantle with the observed time-integrated chondritic Re/Os, (and hence 187Os/188Os), DMet/Sil for both elements must converge to a common value. Combined with previously measured DMet/Sil for Os, the estimated temperature at which this convergence occurs is 4500 (±900) K. At this temperature, however, the Re and Os content of the equilibrated silicate is ~100-fold too low to explain mantle abundances. In the same experiments, much lower Dmet/sil values have been determined for Au, and require the metal-silicate equilibration temperature to be <3200 K, as hotter conditions result in an excess of Au in the mantle. Thus, the large disparity in partitioning between Re or Os, and Au at core-forming temperatures argues against their mantle concentrations set solely by metal-silicate equilibrium at the base of a terrestrial magma ocean.