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  • In the framework of the R/V R. Margalef (Spanish Institute of Oceanography, IEO-CSIC) field works and alongtrack navigation, a continuous singlebeam echosounder was used in order to measure the depth along its trajectory. These data were mainly held around Spanish territorial waters. During the ship trajectory, the echosounder was receiving and integrating bathymetry data and GPS position. All the data recorded were checked for quality control in a semi-automatic standard procedure and stored in MEDAR/MEDATLAS-SDN format. Important Note: This submission has been initially submitted to SEA scieNtific Open data Edition (SEANOE) publication service and received the recorded DOI. The metadata elements have been further processed (refined) in EMODnet Ingestion Service in order to conform with the Data Submission Service specifications.

  • Abstract: The 2015 VESPA voyage (Volcanic Evolution of South Pacific Arcs) was a seismic and rock dredging expedition to the Loyalty and Three Kings ridges and South Fiji Basin. In this paper we present 33 Ar/Ar, 23 micropaleontological and two U/Pb ages for igneous and sedimentary rocks from 33 dredge sites at 25-28°S in this previously little-studied part of the southwest Pacific Ocean. Igneous rocks include basalts, dolerites, basaltic andesites, trachyandesites and a granite. Successful Ar/Ar dating of altered and/or low-K basalts was achieved through careful sample selection and processing, detailed petrographic and element mapping of groundmass, and incremental heating experiments on both phenocryst and groundmass separates to interpret the complex spectra produced by samples having multiple K reservoirs. The Ar/Ar ages of most of the sampled lavas, irrespective of composition, are latest Oligocene to earliest Miocene (25-22 Ma), but two are Eocene (39-36 Ma). The granite has a U/Pb zircon age of 23.6±0.3 Ma. Ar/Ar lava ages based on dating are corroborated by microfossil ages and by detrital U/Pb zircon dating of a sandstone. In a southwest Pacific regional context, the VESPA lavas are part of a >4000 km long disrupted western belt of Eocene to Miocene subduction-related volcanic rocks. The belt includes arc rocks in Northland New Zealand, Northland Plateau, Three Kings Ridge, and Loyalty Ridge and, more speculatively, D’Entrecasteaux Ridge, West Torres Plateau and Rennell Ridge. This western belt is the product of superimposed Eocene and Oligocene-Miocene remnant volcanic arcs that were stranded along the edge of Zealandia as still-active arcs migrated east with the Pacific trench. The eastern belt of Eocene-Miocene volcanic arcs is more tectonically disrupted and less well-sampled than the western belt. Overall Eocene-Miocene SW Pacific arc development is explained in terms of west-dipping subduction and southward propagating tectonics. Plain word summary: Samples of lava from the seabed between New Zealand and New Caledonia have been dated using atomic clocks and fossils. Most lavas erupted in a big pulse of volcanic activity between 25 and 22 million years ago. They are part of a >4000 km long belt of now-extinct undersea volcanoes that lie between New Zealand and the Solomon Islands, and which were related to early subduction of the Pacific Plate under the Australian Plate. Important Note: This submission has been initially submitted to SEA scieNtific Open data Edition (SEANOE) publication service and received the recorded DOI. The metadata elements have been further processed (refined) in EMODnet Ingestion Service in order to conform with the Data Submission Service specifications.

  • We discuss vegetation and climate changes across western Europe over the last deglaciation, especially zooming on the Heinrich Stadial 1 (HS1) interval in the northern Bay of Biscay. Our study focuses on the marine palynological investigation of core MD13-3438, with new pollen analyses, here compared to a set of paleohydrographical marine proxies (including dinoflagellate cysts / dinocysts) obtained on the same core. We show that the recorded pollen signature is, at that time, tightly related to the fluvial dynamics of the ‘Fleuve Manche’ paleoriver, the latter being coupled with European Ice Sheet fluctuations, as well as influenced by fluvial deliveries from closer French rivers of the Atlantic coast. The onset of HS1 (18.2–16.7 ka BP), marked by enhanced ‘Fleuve Manche’ paleoriver seasonal runoff, is characterized by: i) two episodes of substantial fluvio-glacial input, concomitant with warmer summers and marked by increases of temperate forest pollen grain percentages; ii) and three episodes of moderate runoff, concomitant with extended colder winters and corresponding to increases of boreal forest pollen grain percentages. We suggest an important role of the variability of the North Atlantic atmospheric circulation in explaining those multidecadal changes in pollen sources recorded in the marine realm. When westerlies are deflected southward (respectively northward), they would bring higher humidity to the southern-western and closer (respectively northern-eastern and more distal) distributaries/rivers of the ‘Fleuve Manche’ paleoriver system, associated to moderate (respectively intense) runoff. Then, extreme cold and dry climate conditions are recorded at the onset of Heinrich Event 1 (16.7–15.6 ka BP) with marked occurrences of steppic pollen grains, followed by more humid conditions at the end of HS1, with mixed signatures of open-vegetation and temperate forest taxa. The wettest conditions are recorded during the Bølling-Allerød, concomitantly with the sea level rise and the advection of warm and salty waters by the North Atlantic Current to the study site. Important Note: This submission has been initially submitted to SEA scieNtific Open data Edition (SEANOE) publication service and received the recorded DOI. The metadata elements have been further processed (refined) in EMODnet Ingestion Service in order to conform with the Data Submission Service specifications.

  • New results acquired in south-Brittany (MD08-3204 CQ core: Bay of Quiberon and VK03-58bis core: south Glénan islands) allow depicting Holocene paleoenvironmental changes from 8.5 ka BP to present through a multi-proxy dataset including sedimentological and palynological data. First, grain-size analyses and AMS-14C dates highlight a common sedimentary history for both study cores. The relative sea level (RSL) slowdown was accompanied by a significant drop of the sedimentation rates between ca. 8.3 and 5.7 ka BP, after being relatively higher at the onset of the Holocene. This interval led to the establishment of a shell-condensed level, identified in core VK03-58bis by the “Turritella layer” and interpreted as a marker for the maximum flooding surface. Palynological data (pollen grains and dinoflagellate cyst assemblages) acquired in core MD08-3204 CQ argue for an amplification of the fluvial influence since 5.7 ka BP; the establishment of the highstand system tract (i.e., mixed marine and fluviatile influences on the platform) then accompanying the slowdown of the RSL rise-rates. On the shelf, the amplification of Anthropogenic Pollen Indicators (API) is then better detected since 4.2 ka BP, not only due to human impact increase but also due to a stronger fluvial influence on the shelf during the Late Holocene. Palynological data, recorded on the 8.5–8.3 ka BP interval along an inshore-offshore gradient, also demonstrate the complexity of the palynological signal such as i) the fluvial influence that promotes some pollinic taxa (i.e., Corylus, Alnus) from proximal areas and ii) the macro-regionalization of palynomorph sources in distal cores. In addition, the comparison of palynological tracers, including API, over the last 7 kyrs, with south-Brittany coastal and mid-shelf sites subjected to northern vs. southern Loire catchment areas, allowed discussing a major hydro-climatic effect on the reconstructed palynological signals. Strengthened subpolar gyre dynamics (SPG), combined with recurrent positive North Atlantic Oscillation (NAO) configurations, appear responsible for increased winter precipitations and fluvial discharges over northern Europe, such as in Brittany. Conversely, weakened SPG intervals, associated with negative NAO-like modes, are characterized by intensified winter fluvial discharges over southern Europe. Interestingly, we record, at an infra-orbital timescale, major peaks of API during periods of strengthened (/weakened) SPG dynamics in sites subjects to Brittany watersheds (/Loire watersheds) inputs. Important Note: This submission has been initially submitted to SEA scieNtific Open data Edition (SEANOE) publication service and received the recorded DOI. The metadata elements have been further processed (refined) in EMODnet Ingestion Service in order to conform with the Data Submission Service specifications.

  • The SW Pacific region contains several ridges and basins that are inferred to represent pre-Quaternary volcanic arcs and back-arc basins. The geology of these features is less well characterized than that of the active Tonga-Kermadec and Vanuatu arcs. We report new major and trace element, and Pb, Hf, Sr and Nd isotope data for 27 lavas dredged from the Loyalty and Three Kings ridges during the 2015 VESPA cruise of R/V l'Atalante. Low-K basalts were dredged from the seabed deeper than 3300 m, and high-K to shoshonitic suites from shallower ridge crests at 2000–3300 m. The samples are mainly basalts, with lesser trachybasalts, basaltic andesites, trachyandesites andesites, dacites, and one granite (anhydrous SiO2 and K2O + Na2O range from ~47 to 64 and 1.5 to 11 wt% respectively). Trace element patterns allow discrimination of three geochemical signatures, identified as i) depleted, ii) transitional and iii) enriched, based on their light to heavy rare earth element (REE) ratios (with La/Sm ranging from 0.4 to 8). Depleted and transitional samples are basalts, featuring REE concentrations similar to MORB, but with high field strength element and large ion lithophile element contents, typical of back-arc basin basalts. The most enriched samples are basaltic andesites, andesites, trachyandesites and trachytes with island arc magma trace element signatures. Pb isotope ranges are limited (208Pb/204Pb ~38 to 39.8, 207Pb/204Pb ~15.51 to 15.64 and 206Pb/~17.9 to 20.1), while Hf isotopes display more diverse compositions (eHf ranging from +7.7 to +14). Both Nd (eNd = 2.8–9.3) and Sr (87Sr/86Sr = 0.7026–0.7048) isotopes are correlated with Hf data. Trace element and isotopic compositions can be explained in terms of mixing between three distinct geochemical endmembers in the mantle resembling DMM, HIMU and EM-2 sources. Our study confirms voluminous subduction-related magmatism on the Loyalty and Three Kings ridges, mostly of Late Oligocene – Early Miocene age. The issue of polarity of subduction to generate these rocks remains open, but the composition-space-time distribution of the igneous rocks can be explained in the context of SW Pacific geodynamics using a west-dipping Pacific slab model. Important Note: This submission has been initially submitted to SEA scieNtific Open data Edition (SEANOE) publication service and received the recorded DOI. The metadata elements have been further processed (refined) in EMODnet Ingestion Service in order to conform with the Data Submission Service specifications.