Multiproxy paleoceanographic study from the western Barents Sea reveals dramatic Younger Dryas onset followed by oscillatory warming trend

The Younger Dryas (YD) is recognized as a cool period that began and ended abruptly during a time of general warming at the end of the last glacial. New multi-proxy data from a sediment gravity core from Storfjordrenna (western Barents Sea, 253 m water depth) reveals that the onset of the YD occurred as a single short-lived dramatic environment deterioration, whereas the subsequent warming was oscillatory. The water masses in the western Barents Sea were likely strongly stratified at the onset of the YD, possibly due to runoff of meltwater combined with perennial sea-ice cover, the latter may last up to several decades without any brake-up. Consequently, anoxic conditions prevailed at the bottom of Storfjordrenna, leading to a sharp reduction of benthic biota and the appearance of vivianite microconcretions which formation is favoured by reducing conditions. While the anoxic conditions in Storfjordrenna were transient, the unfavorable conditions for benthic foraminifera lasted for c. 1300 years. We suggest that the Pre-Boreal Oscillation, just after the onset of the Holocene, may have been a continuation of the oscillatory warming trend during the YD.

Environmental Assessment of Trace Metals in San Simon Bay Sediments (NW Iberian Peninsula)

A gravity core (220 cm depth) was collected to investigate the geochemistry, enrichment, and pollution of trace metals in anoxic sediments from San Simon Bay, an ecosystem of high biological productivity in the northwest of Spain. A five-step sequential extraction procedure was used. The Cu, Pb, and Zn contents decreased with depth, with maximum values in the top layers. Ni and Zn were bound to pyrite fractions, while Cd and Pb were associated with the most mobile fractions. The analyzed metals were associated with the fractions bound to organic matter, mainly with the strongly bound to organic matter fraction. High Cd and Cu values were observed. The fractionation showed a high mobility for Cd (28.3–100%) and Pb (54.0–70.2%). Moreover, the pollution factor and the geoaccumulation index reflected a high contamination for Pb and a moderate contamination for Cu and Zn in the superficial layers, pointing to a possible ecotoxicological risk to organisms in San Simon Bay.

Exploring diversity of marine eukaryotes across 385 ka old gravity core using sedaDNA

<p>In the last ten years, sedimentary ancient DNA (sedaDNA) becomes a new proxy for paleoceanographic analyses that provide information about large range of non-fossilized taxa. Usually, the sediment samples destinated for sedaDNA study are immediately frozen after collection or stored in special buffer to preserve the DNA. However, there are many cores that have been collected long time before the advent of paleogenomics and that are commonly refrigerated and stored at 4°C. Here, we test whether such cores can be used as a source of ancient DNA, by analysing the sedaDNA samples from 36 meters long marine gravity core that was stored during 14 years at 4 °C. The core MD05-2920 was retrieved during the MD148/PECTEN – Images XII cruise, in Bismarck Sea, off New Papua Guinea, and records the past 385 ka. We analysed samples from 20 layers spanning the interval from 1.6 ka to 384 ka, where isotopic measures of ∂<sup>18</sup>O showed significant paleoceanographic changes. We started by analysing a universal eukaryotic marker, the V9 (170 bp) region of the 18S rRNA. However, the obtained datasets were dominated by sequences belonging to species of fungi and amoebae that probably originated from post-collection storage. More data were obtained by using markers specific to selected marine taxa, such as foraminifera, radiolaria, and diatoms. The analysis of these data show clearly that the DNA is preserved in marine sediment down to 385 ka old layers. Our study also shows a possibility to exploit the sedaDNA from refrigerated material stored in cores repositories.</p>

The use and beauty of ultra-high-resolution seismic reflection imaging in Late Quaternary marine volcaniclastic settings, Napoli Bay, Italy

Very high-resolution, single channel (IKB-Seistec™) reflection profiles acquired offshore the Napoli Bay, complemented with geological and geophysical data from the literature, provide unprecedented, superb seismic imaging of the Latest Pleistocene-Holocene stratigraphic architecture of the submerged sectors Campi Flegrei and Somma-Vesuvius volcanic districts. Seismic profiles were calibrated by gravity core data and document a range of depositional systems, volcanic structures and hydrothermal features that evolved after the onset of the Last Glacial Maximum (ca. 18 ka BP) over the continental shelf on the Campania coastal zone.Seistec profiles from the Pozzuoli Bay yield high-resolution images of the shallow structure of the collapse caldera-ring fault - resurgent dome system associated with the eruption of the Neapolitan Yellow Tuff (NYT) (ca 15 ka BP) and support a working hypothesis to assess the timing and the styles of deformation of the NYT resurgent structure throughout the Latest Quaternary. Seismic images also revealed the nature of the fragile deformation of strata along the NYT ring fault system and the occurrence of hydrothermal fluids and volcanic/sub-volcanic intrusions ascending along the ring fault zone. Seismic data acquired over the continental shelf off the Somma-Vesuvius stratovolcano, display evidence of gravitational instability of sand wave deposits originated by the underwater modification of pyroclastic flows that entered the seawater after destroying the Roman city of Herculaneum during the 79 CE eruption of Vesuvius.At the Banco della Montagna, a hummocky seafloor knoll located between the Somma-Vesuvius and the Pozzuoli Bay, seismic profiles and gravity core data revealed the occurrence of a field of volcaniclastic diapirs formed by the dragging and rising up of unconsolidated pumice, as a consequence of fluid overpressure at depth associated with active degassing and fluid venting at the seafloor.

Seismic and lithofacies characterization of a gravity core transect down the submarine Tuaheni Landslide Complex, NE New Zealand

The southern Tuaheni Landslide Complex (TLC) at the Hikurangi subduction margin displays distinctive morphological features along its distribution over the Tuaheni slope offshore Gisborne, New Zealand. We here present first analyses of a gravity core transect that systematically samples surficial sediments from the source area to the toe of this landslide complex, thus providing important new insight into shallow lithological variation in the slide complex. Geophysical and geochemical core logs and core descriptions form the basis for a characterization of representative sediment successions that are indicative of the respective slope segment of recovery. Our results show that the lithology of surficial sediments varies significantly along the length of the landslide complex. Depending on the slope segment observed, this variation includes post-Last Glacial Maximum (LGM) outer-shelf sediments, and hemipelagic drape and near-surface reworked debris avalanche deposits, as well as multiple intercalated thinner turbidites and tephra layers at the distal end of the profile. Lithological downslope variability suggests ongoing mass transport events through the late Holocene that were likely to have been limited to small mud-turbidite flows. Integration with acoustic sub-bottom imagery reveals the presence of multiple stacked mass-transport deposits at depth, contrasting with previous interpretations of a single parent failure.

Preliminary results of high resolution paleoceanography and paleoclimatology during sapropel S1 deposition (South Limnos Basin, North Aegean Sea).

The paleoenviromental conditions during the depositional interval of sapropel S1 in the northeastern Aegean (gravity core M-4, length 2.53 m; south Limnos basin) are studied based on quantitative micropaleontological (benthic and planktonic foraminifera) and geochemical (OC, δ13Corg) analyses. Special feature of core M-4 is the thickness of S1 layer (96 cm). Our study points that sapropelic layer S1a has been deposited in more dysoxic and warmer conditions in respect to S1b. Both primary productivity and preservation of organic material are more intense during the lower part of S1. An interruption of the sapropelic conditions at 8.0 Ka BP which is mainly characterized by the increase of agglutinated foraminiferal forms confirms both higher oxygen bottom conditions and freshwater input.