ALBERT

Description: We present the neodymium isotopic composition (epsilon-Nd) of mixed planktonic foraminifera species from a sediment core collected at 622 m water depth in the Balearic Sea, as well as epsilon-Nd of scleractinian cold-water corals (CWC; Madrepora oculata, Lophelia pertusa) retrieved between 280 and 442 m water depth in the Alboran Sea and at 414 m depth in the southern Sardinian continental margin. The aim is to constrain hydrological variations at intermediate depths in the western Mediterranean Sea during the last 20 kyr. Planktonic (Globigerina bulloides) and benthic (Cibicidoides pachyderma) foraminifera from the Balearic Sea were also analyzed for stable oxygen (d18O) and carbon (d13C) isotopes. The foraminiferal and coral epsilon-Nd values from the Balearic and Alboran seas are comparable over the last ~13 kyr, with mean values of -8.94 ± 0.26 (1 Sigma; n = 24) and -8.91 ± 0.18 (1 Sigma; n = 25), respectively. Before 13 ka BP, the foraminiferal epsilon-Nd values are slightly lower (-9.28 ± 0.15) and tend to reflect higher mixing between intermediate and deep waters, which are characterized by more unradiogenic epsilon-Nd values. The slight epsilon-Nd increase after 13 ka BP is associated with a decoupling in the benthic foraminiferal d13C composition between intermediate and deeper depths, which started at ~16 ka BP. This suggests an earlier stratification of the water masses and a subsequent reduced contribution of unradiogenic epsilon-Nd from deep waters. The CWC from the Sardinia Channel show a much larger scatter of epsilon-Nd values, from -8.66 ± 0.30 to 5.99 ± 0.50, and a lower average (-7.31 ± 0.73; n = 19) compared to the CWC and foraminifera from the Alboran and Balearic seas, indicative of intermediate waters sourced from the Levantine basin. At the time of sapropel S1 deposition (10.2 to 6.4 ka), the epsilon-Nd values of the Sardinian CWC become more unradiogenic (-8.38 ± 0.47; n = 3 at ~8.7 ka BP), suggesting a significant contribution of intermediate waters originated from the western basin. We propose that western Mediterranean intermediate waters replaced the Levantine Intermediate Water (LIW), and thus there was a strong reduction of the LIW during the mid-sapropel (~8.7 ka BP). This observation supports a notable change of Mediterranean circulation pattern centered on sapropel S1 that needs further investigation to be confirmed.

Description: This data set includes clay mineral assemblage, major element composition and carbonate content of Core SO18383-3 retrieved in the southern South China Sea during the cruise SO140 on R/V SONNE. The Core SO18383-3 is located at 7º38.54'N, 109º29.15'E, and is 710.6 m water depth and 9.44 m long. The clay mineral assemblage (237 samples, 4 cm resolution) was analyzed by X-ray diffraction (XRD) using a PANalytical X'Pert PRO diffractometer on oriented mounts of non-calcareous, clay-sized particles. The major element composition (166 samples, 4-8 cm resolutions) was analyzed by X-ray fluorescence (XRF) using a PANalytical Axios MAX Spectrometer on bulk sediments. The carbonate content was analyzed by the gasometric method on bulk sediments.

Description: The detrital component of marine sediment is a powerful recorder of paleoenvironmental changes in a marginal sea such as the South China Sea. This is in particular valid for the magnetic fraction that is one of the key parameters for paleoenvironmental studies in the South China Sea, although poorly used so far. We report here on the analysis of the magnetic properties of a 50 m-long sedimentary sequence retrieved from the northern South China Sea, on the continental slope off the Pearl River mouth. Magnetic minerals with different coercivities (magnetite, pyrrhotite, and hematite) are mixed. The variations in relative content of these magnetic minerals illustrate influences of various external forcing mechanisms at different timescales. The pyrrhotite content exhibits a long-term increase, which is also observed in illite+chlorite content, indicating a continuous enhancement of supply from Taiwan most likely related to active Taiwan orogeny. Glacial-interglacial fluctuations are characterized by more magnetite and pyrrhotite with coarser silt and magnetic grains during glacials than interglacials. This is attributed to sea-level changes with the enormous continental shelf exposed during glacials, in turn affecting the sediment transport distance and pathway. On a shorter timescale, larger hematite inputs in fine-grained sediments coincide with precession minima. We suggest that this periodic hematite supply change is related to the eolian dust deposited at the studied site in addition to the fluvial and oceanic transported materials.