Environmental and Oceanographic Conditions at the Continental Margin of the Central Basin, Northwestern Ross Sea (Antarctica) since the Last Glacial Maximum

The continental margin is a key area for studying the sedimentary processes related to the advance and retreat of the Ross Ice Shelf (Antarctica); nevertheless, much remains to be investigated. The aim of this study is to increase the knowledge of the last glacial/deglacial dynamics in the Central Basin slope–basin system using a multidisciplinary approach, including integrated sedimentological, micropaleontological and tephrochronological information. The analyses carried out on three box cores highlighted sedimentary sequences characterised by tree stratigraphic units. Collected sediments represent a time interval from 24 ka Before Present (BP) to the present time. Grain size clustering and data on the sortable silt component, together with diatom, silicoflagellate and foraminifera assemblages indicate the influence of the ice shelf calving zone (Unit 1, 24–17 ka BP), progressive receding due to Circumpolar Deep Water inflow (Unit 2, 17–10.2 ka BP) and (Unit 3, 10.2 ka BP–present) the establishment of seasonal sea ice with a strengthening of bottom currents. The dominant and persistent process is a sedimentation controlled by contour currents, which tend to modulate intensity in time and space. A primary volcanic ash layer dated back at around 22 ka BP is correlated with the explosive activity of Mount Rittmann

Extant silicoflagellates from the Northeast Aegean (eastern Mediterranean Sea): Morphologies and double skeletons [Silicoflagellés actuels de la mer Egée du Nord-Est (Mer Méditerranée orientale) : morphologies et squelettes doubles]

Silicoflagellate abundance, vertical distribution and morphology were studied during spring (March 2014) at three sampling stations located in the Northeast Aegean Sea adjacent to the Dardanelles Strait and characterized by a variable influx of cold, low-salinity Black Sea water. The silicoflagellate assemblage was dominated by Dictyocha stapedia and Stephanocha speculum with minor contribution of D. aculeata and Octactis pulchra. While specimens of D. stapedia were represented by the typical morphologies described in other areas of the Mediterranean Sea, populations of S. speculum displayed peculiar characters: they were large, predominantly 7-sided, with a small apical ring as well as apical ring spines, concave basal ring sides and non-rotated apical structure. Some of these features have been described for S. speculum at high latitudes, but the combined characters make these specimens slightly different from the high latitude populations. Similar morphologies have been observed in the western Black Sea, thus we can infer that the peculiar specimens detected in the Northeast Aegean are associated with the influx of Black Sea water masses. © 2016 Elsevier Masson SA