Shape-invariant multibeam backscatter data of the eastern slope of the Porcupine Seabight (50 m grid size)

In this study multibeam angular backscatter data acquired in the eastern slope of the Porcupine Seabight are analysed. Processing of the angular backscatter data using the 'NRGCOR' software was made for 29 locations comprising different geological provinces like: carbonate mounds, buried mounds, seafloor channels, and inter-channel areas. A detailed methodology is developed to produce a map of angle-invariant (normalized) backscatter data by correcting the local angular backscatter values. The present paper involves detailed processing steps and related technical aspects of the normalization approach. The presented angle-invariant backscatter map possesses 12 dB dynamic range in terms of grey scale. A clear distinction is seen between the mound dominated northern area (Belgica province) and the Gollum channel seafloor at the southern end of the site. Qualitative analyses of the calculated mean backscatter values i.e., grey scale levels, utilizing angle-invariant backscatter data generally indicate backscatter values are highest (lighter grey scale) in the mound areas followed by buried mounds. The backscatter values are lowest in the inter-channel areas (lowest grey scale level). Moderate backscatter values (medium grey level) are observed from the Gollum and Kings channel data, and significant variability within the channel seafloor provinces. The segmentation of the channel seafloor provinces are made based on the computed grey scale levels for further analyses based on the angular backscatter strength. Three major parameters are utilized to classify four different seafloor provinces of the Porcupine Seabight by employing a semi-empirical method to analyse multibeam angular backscatter data. The predicted backscatter response which has been computed at 20° is the highest for the mound areas. The coefficient of variation (CV) of the mean backscatter response is also the highest for the mound areas. Interestingly, the slope value of the buried mound areas are found to be the highest. However, the channel seafloor of moderate backscatter response presents the lowest slope and CV values. A critical examination of the inter-channel areas indicates less variability within the estimated three parameters.

Geochemical analysis of minerals from sediment core CRP-2 in the Ross Sea, Antarctica

Distribution patterns, petrography, whole-rock and mineral chemistry, and shape and fabric data are described for the most representative basement lithologies occurring as clasts (granule to bolder grain-size class) from the 625 m deep CRP-2/2A drillcore. A major change in the distribution pattern of the clast types occurs at c. 310 mbsf., with granitoid-dominated clasts above and mainly dolerite clasts below; moreover, compositional and modal data suggest a further division into seven main detrital assemblages or petrofacies. In spite of this variability, most granitoid pebbles consist of either pink or grey biotite±hornblende monzogranites. Other less common and ubiquitous lithologies include biotite syenogranite, biotite-hornblende granodiorite, tonalite, monzogranitic porphyries (very common below 310 mbsf), microgranite, and subordinately, monzogabbro, Ca-silicate rocks, biotite-clinozoisite schist and biotite orthogneiss (restricted to the pre-Pliocene strata). The ubiquitous occurrence of biotite±hornblende monzogranite pebbles in both the Quaternary-Pliocene and Miocene-Oligocene sections, apparently reflects the dominance of these lithologies in the onshore basement, and particularly in the Cambro-Ordovician Granite Harbour Igneous Complex which forms the most extensive outcrop in southern Victoria Land. The petrographical features of the other CRP-2/2A pebble lithologies are consistent with a supply dominantly from areas of the Transantarctic Mountains facing the CRP-2/2A site, and they thus provide further evidence of a local provenance for the supply of basement clasts to the CRP-2/2A sedimentary strata.

Composition of Fe-Mn micronodules, nodules and host bottom sediments from the Northeast Pacific Basin

Authigenic ferromanganese manifestations in bottom sediments from two horizons (0-10 and 240-250 cm) located in the low/high bioproductive transitional zone of the Pacific Ocean were studied. In addition two compositionally different types of micronodules, crusts and ferromanganese nodules were detected in the surface horizon (0-1 cm). Three size fractions (50-100, 100-250, and 250-500 µm) of manganese micronodules were investigated. In terms of surface morphology, color, and shape, the micronodules are divided into dull round (MN1) and angular lustrous (MN2) varieties with different mineral and chemical compositions. MN1 are enriched in Mn and depleted in Fe as compared with MN2. Mn/Fe ratio in MN1 varies from 13 to 14. Asbolane-buserite and birnessite are the major manganese minerals in them. MN2 is mainly composed of vernadite with Mn/Fe ratio from 4.3 to 4.8. Relative to MN1, fraction 50-100 µm of MN2 is enriched in Fe (2.6 times), W (1.8), Mo (3.2), Th (2.3), Ce (5.8), and REE (from 1.2 to 1.8). Relative to counterparts from MN1, separate fractions of MN2 are characterized by greater compositional difference. For example, increase in size of micronodules leads to decrease in contents of Fe (by 10 rel. %), Ce (2 times), W (2.1 times), Mo (2.2 times), and Co (1.5 times). At the same time one can see increase in contents of other elements: Th and Cu (2.1 times), Ni (1.9 times), and REE (from 1.2 to 1.6 times). Differences in chemical and mineral compositions of MN1 and MN2 fractions can be related to alternation of oxidative and suboxidative conditions in the sediments owing to input of labile organic matter, which acts as the major reducer, and allochthonous genesis of MN2.

Bedform measurements from the San Francisco Bay Coastal System

The morphology of ~45,000 bedforms from 13 multibeam bathymetry surveys was used as a proxy for identifying net bedload sediment transport directions and pathways throughout the San Francisco Bay estuary and adjacent outer coast. The spatially-averaged shape asymmetry of the bedforms reveals distinct pathways of ebb and flood transport. Additionally, the region-wide, ebb-oriented asymmetry of 5% suggests net seaward-directed transport within the estuarine-coastal system, with significant seaward asymmetry at the mouth of San Francisco Bay (11%), through the northern reaches of the Bay (7-8%), and among the largest bedforms (21% for lambda > 50 m). This general indication for the net transport of sand to the open coast strongly suggests that anthropogenic removal of sediment from the estuary, particularly along clearly defined seaward transport pathways, will limit the supply of sand to chronically eroding, open-coast beaches. The bedform asymmetry measurements significantly agree (up to ~ 76%) with modeled annual residual transport directions derived from a hydrodynamically-calibrated numerical model, and the orientation of adjacent, flow-sculpted seafloor features such as mega-flute structures, providing a comprehensive validation of the technique. The methods described in this paper to determine well-defined, cross-validated sediment transport pathways can be applied to estuarine-coastal systems globally where bedforms are present. The results can inform and improve regional sediment management practices to more efficiently utilize often limited sediment resources and mitigate current and future sediment supply-related impacts.

Relative abundances and microbial numbers of organisms from water sample station GeoB15704-2

Due to sampling difficulties, little is known about microbial communities associated with sinking marine snow in the twilight zone. A drifting sediment trap was equipped with a viscous cryogel and deployed to collect intact marine snow from depths of 100 and 400 m off Cape Blanc (Mauritania). Marine snow aggregates were fixed and washed in situ to prevent changes in microbial community composition and to enable subsequent analysis using catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH). The attached microbial communities collected at 100 m were similar to the free-living community at the depth of the fluorescence maximum (20 m) but different from those at other depths (150, 400, 550, and 700 m). Therefore, the attached microbial community seemed to be "inherited" from that at the fluorescence maximum. The attached microbial community structure at 400 m differed from that of the attached community at 100 m and from that of any free-living community at the tested depths, except that collected near the sediment at 700 m. The differences between the particle-associated communities at 400 m and 100 m appeared to be due to internal changes in the attached microbial community rather than de novo colonization, detachment, or grazing during the sinking of marine snow. The new sampling method presented here will facilitate future investigations into the mechanisms that shape the bacterial community within sinking marine snow, leading to better understanding of the mechanisms which regulate biogeochemical cycling of settling organic matter.

Contents of 230Th, Fe2O3, MnO and P2O5 in bottom sediments from the Tropical Pacific

Shape of the 230Th vertical distribution curve ideally close to exponential is studied to determine isotopic age of deep-sea sediments. In practice such ideal 230Th vertical distribution curve is rarely occur; secondary maxima and minima often appear on it. It has been shown that oxyhydroxides of Fe, Mn, and also Corg and P are of prime importance for 230Th concentration. A method is offered for normalizing the vertical distribution curve of 230Th based on taking into account content of these elements in sediment.

Heavy metal contents in bottom sediments and Fe-Mn nodules and their states in bottom and interstitial waters from the Clarion-Clipperton province

Ultrafiltration with tagged atoms was used to study physicochemical states (dissolved, colloidal, suspended) of Mn, Co, Ni, Zn, and Ce in bottom and interstitial waters collected in two areas of the Pacific Ocean with Fe-Mn nodules of different size, shape, structure and origin in different abundances. Use of filters with pore diameter of 0.05 ?m allowed to identify colloidal forms of the metals in bottom sediments and interstitial waters. It was demonstrated experimentally that differences in physicochemical situation in the studied areas could result in formation of nodules by different mechanisms, producing characteristic differences that were observed.

(Appendix) Vertebral number of topsmelt, Atherinops affinis, adults and offspring from different latitudes along the North-American Pacific coast

Organisms that are distributed across spatial climate gradients often exhibit adaptive local variations in morphological and physiological traits, but to what extent such gradients shape evolutionary responses is still unclear. Given the strong natural contrast in latitudinal temperature gradients between the North-American Pacific and Atlantic coast, we asked how increases in vertebral number (VN, known as Jordan's Rule) with latitude would differ between Pacific (Atherinops affinis) and Atlantic Silversides (Menidia menidia), two ecologically equivalent and taxonomically similar fishes with similar latitudinal distributions. VN was determined from radiographs of wild-caught adults (genetic + environmental differences) and its genetic basis confirmed by rearing offspring in common garden experiments. Compared to published data on VN variation in M. menidia (a mean increase of 7.0 vertebrae from 32 to 46°N, VN slope = 0.42/lat), the latitudinal VN increase in Pacific Silversides was approximately half as strong (a mean increase of 3.3 vertebrae from 28 to 43°N, VN slope = 0.23/lat). This mimicked the strong Atlantic (1.11°C/lat) versus weak Pacific latitudinal gradient (0.40°C/lat) in median annual sea surface temperature (SST). Importantly, the relationship of VN to SST was not significantly different between the two species (average slope = -0.39 vertebrae/°C), thus suggesting a common thermal dependency of VN in silverside fishes. Our findings provide novel support for the hypothesis that temperature gradients are the ultimate cause of Jordan's Rule, even though its exact adaptive significance remains speculative. A second investigated trait, the mode of sex determination in Atlantic versus Pacific Silversides, revealed patterns that were inconsistent with our expectation: M. menidia displays temperature-dependent sex determination (TSD) at low latitudes, where growing seasons are long or unconstrained, but also a gradual shift to genetic sex determination (GSD) with increasing latitude due to more and more curtailed growing seasons. Sex ratios in A. affinis, on the other hand, were independent of latitude and rearing temperature (indicating GSD), even though growing seasons are thermally unconstrained across most of the geographical distribution of A. affinis. This suggests that additional factors (e.g., longevity) play an important role in shaping the mode of sex determination in silverside fishes.

Estimatin of roughness lengths with a ship-mounted ADCP from Knudedyb, Denmark in October 2009

The hydraulic effect of asymmetric compound bedforms on tidal currents was assessed from field measurements of flow velocity in the Knudedyb tidal inlet, Denmark. Large asymmetric bedforms with smaller superimposed ones are a common feature of sandy shallow water environments and are known to act as hydraulic roughness elements in dependence with flow direction. The presence of a flow separation zone on the bedform lee was estimated through analysis of the measured velocity directions and the calculation of the flow separation line. The Law of the Wall was used to calculate roughness lengths and shear velocities from log-linear segments sought on transect-averaged and single-location velocity profiles. During the ebb tide a permanent flow separation zone was established over the steep (10-20°) lee sides of the ebb-oriented primary bedforms, which generated a consequent drag on the flow. During the flood, no flow separation was induced by the gentle (2°) lee side of the primary bedforms except over the steepest (10°) part of the lee side where a small separation zone was sometimes observed. As a result, hydraulic roughness was only due to the superimposed bedforms. The parameterized flow separation line was found to underestimate the length of the flow separation zone of the primary bedforms. A better estimation of the presence and shape of the flow separation zone over complex bedforms in a tidal environment still needs to be determined; in particular the relationship between flow separation zone and bedform geometry (asymmetry, relative height or slope of the lee side) is unclear. This would improve the prediction of complex bedform roughness in tidal flows.

Description and chemical composition of ferromanganese nodules from Station 123, Oneida Lake, New York

226Ra is used to document the growth histories of six manganese nodules from Oneida Lake, New York. Detailed sectioning and analysis reveal that there are discontinuous gradients in 226Ra content in these samples. These gradients result from periods of rapid growth (>1 mm/100 years) separated by periods of no growth of erosion. Although the 226Ra 'age' of the nodules approximates the age of Oneida Lake, the nodules are not sediment-covered because they occur only in areas of the lake where fine-grained sediments are not accumulating.

Sedimentology and Cd/Ca ratios of benthic foraminifera from ODP Site 172-1060 in the western Nort Atlantic

The Western Boundary Undercurrent (WBUC), off eastern America, is an important component of the Atlantic Meridional Overturning circulation and is the principal route for southward transport of North Atlantic waters and southward return of Southern Source Water (SSW). Here a direct flow speed proxy (mean grain size of the sortable silt) is used to infer the vigour of flow of the palaeo-WBUC at Blake Outer Ridge, (ODP Site 1060, depth 3481 m) during Marine Isotope Stage (MIS) 3. The overall shape of the flow speed proxy record shows a complex pattern of variability, with generally more vigorous flow and larger-scale flow variations between 35 and 60 ka than in the younger part of MIS 3 and MIS 2 (b35 ka). Six events of reduced bottom flow vigour (Slow Events, SEs) occur. These appear uncorrelated with Heinrich events, but are instead synchronous with the warming phases of Antarctic Warm Events A-1 to A-4 (with one new one, A-1a and one poorly defined, 'A-0'). This indicates that Antarctic climate exerts a stronger control on deep flow vigour in the North Atlantic during MIS 3 than Northern Hemisphere climate. The correspondence of SEs with Antarctic warming suggests a weaker WBUC flow due to reduced volume flux at SSW source or reduced SSW density. Because the variability of the lower limb of the WBUC was not connected to sharp North Atlantic changes in temperature, it is unlikely that the Dansgaard/Oeschger cycles were associated with a mode of MOC variation involving wholeocean overturn, but more likely with perturbations of only the shallow Glacial Gulf Stream-Glacial Northern Source Intermediate Water cell. Nutrient proxies (benthic carbon isotopes and Cd/Ca of Uvigerina peregrina) at this site show similar trends to the GRIP delta18O record. This correlation has previously been attributed mainly to hydrographic and flow changes but is here shown to be better explained by variations in surface ocean productivity and subsequent decomposition of 12C rich organic material on the sea floor.

Late Miocene to Pleistocene paleoceanographic records from the Feni and Gardar Drifts: Pliocene reduction in abyssal flow

Magnetic fabric analyses from two North Atlantic drift deposits provide proxies for determining relative variations in the strength of abyssal flow over the last 10 my. The data show a cessation of current-controlled sedimentation at the shallower Feni Drift (2417 m) at the time of onset of Northern Hemisphere glaciation (2.6 Ma). Drift formation ended nearly 2 my earlier (4.2 Ma) at the deeper Gardar Drift (3220 m), implying stepwise reduction in deep-water flow. Relatively light delta18O values at the deeper Gardar Drift indicate a warmer, thus also more salty, water mass site prior to 6 Ma. We interpret this as representing Mediterranean Sea water, which flowed north at depths greater than that of the Feni Drift Site. The supply of Mediterranean Water to the North Atlantic was shut off as the Gibraltar Straits closed, causing the Messinian salinity crisis, and never returned to that position in the water column after the Mediterranean opened again.

Spherules and basement analyses from DSDP Hole 5-32

Lower Miocene basaltic glass spherules from DSDP Site 32 pelagic sediments in the eastern Pacific are compositionally diverse, and new analyses and interpretations have been added to those of earlier workers. The spherules are of titanian ferrobasalt which is compositionally similar to highly evolved abyssal basalts and to some oceanic island eruptives, and they were most likely shaped during intense lava fountaining during a number of separate eruptions. These eruptions tapped distinct but related magma batches in terms, for example, of distinctively high TiO2 and FeO* contents. Their age overlaps that of some of the eruptions of the Columbia River Plateau Basalts, but they are compositionally distinct from most of the latter basalts. Although about 15 m.y. old, they show little alteration. The low chlorine and sulfur contents compared to those of abyssal ferrobasalts are consistent with degassing prior to quenching during subaerial eruptions, and rule out production of the spherules by submarine fountaining. Lava fountaining alone is insufficient to account for the distance of about 100 km from even the closest possible seamount source. Instead, large phreatomagmatic eruption columns reaching at least 15 km and including lava fountaining immediately after the initial explosion are required. Alternatively, and deemed less likely, is their deposition by turbidites derived from Pioneer Seamount.

Geochemistry of samples from Valtournenche, Western Italian Alps

Slices of polycyclic metasediments (marbles and meta-cherts) are tectonically amalgamated with the polydeformed basement of the Dent Blanche tectonic system along a major Alpine shear zone in the Western Alps (Becca di Salé area, Valtournenche Valley). A combination of techniques (structural analysis at various scales, metamorphic petrology, geochronology and trace element geochemistry) was applied to determine the age and composition of accessory phases (titanite, allanite and zircon) and their relation to major minerals. The results are used to reconstruct the polyphase structural and metamorphic history, comprising both pre-Alpine and Alpine cycles. The pre-Alpine evolution is associated with low-pressure high-temperature metamorphism related to Permo-Triassic lithospheric thinning. In meta-cherts, microtextural relations indicate coeval growth of allanite and garnet during this stage, at ~ 300 Ma. Textures of zircon also indicate crystallization at HT conditions; ages scatter from 263-294 Ma, with a major cluster of data at ~ 276 Ma. In impure marble, U-Pb analyses of titanite domains (with variable Al and F contents) yield apparent 206Pb/238U dates range from Permian to Jurassic. Chemical and isotopic data suggest that titanite formed at Permian times and was then affected by (extension-related?) fluid circulation during the Triassic and Jurassic, which redistributed major elements (Al and F) and partially opened the U-Pb system. The Alpine cycle lead to early blueschist facies assemblages, which were partly overprinted under greenschist facies conditions. The strong Alpine compressional overprint disrupted the pre-Alpine structural imprint and/or reactivated earlier structures. The pre-Alpine metamorphic record, preserved in these slices of metasediments, reflects the onset of the Permo-Triassic lithospheric extension to Jurassic rifting.

Compilation of quality controlled nutrient profiles from the Mediterranean Sea

In the last decades, a striking amount of hydrographic data, covering the most part of Mediterranean basin, have been generated by the efforts made to characterize the oceanography and ecology of the basin. On the other side, the improvement in technologies, and the consequent perfecting of sampling and analytical techniques, provided data even more reliable than in the past. Nutrient data enter fully in this context, but suffer of the fact of having been produced by a large number of uncoordinated research programs and of being often deficient in quality control, with data bases lacking of intercalibration. In this study we present a computational procedure based on robust statistical parameters and on the physical dynamic properties of the Mediterranean sea and its morphological characteristics, to partially overcome the above limits in the existing data sets. Through a data pre filtering based on the outlier analysis, and thanks to the subsequent shape analysis, the procedure identifies the inconsistent data and for each basin area identifies a characteristic set of shapes (vertical profiles). Rejecting all the profiles that do not follow any of the spotted shapes, the procedure identifies all the reliable profiles and allows us to obtain a data set that can be considered more internally consistent than the existing ones.