Sedimentology on cores off the South Orkney Plateau

• Main Author: Grünig, Sigrun
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1991
• Subjects: ANT-II/3; AWI_Paleo; Giant box corer; GKG; Gravity corer (Kiel type); KL_Mk; Paleoenvironmental Reconstructions from Marine Sediments @ AWI; Piston corer Meischner small; Polarstern; PS04; PS04/254; PS04/256; PS04/257; PS04/258; PS1167-10; PS1169-1; PS1170-1; PS1170-4; PS1171-1; SL; South Orkney; Weddell Sea; Berichte zur Polarforschung; Polar Research; Polarforschung; Reports on polar research
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.860528; https://doi.org/10.1594/PANGAEA.860528

Grab samples and cores for sedimentological studies were retrieved along a N-S transect of the South Orkney Plateau margin. On the basis of morphology, the margin has been subdivided into shelf, upper continental slope, and a lower slope region cut by basins and ridges. Grain size, Sand component, and clay mineralogy were determined as well as water, organic carbon and carbonate contents. In addition, vane shear strength, magnetic intensity and the proportion of ice-rafted debris were measured, dating was done by detailed magnetic stratigraphy, the biofluctuation of the radiolarian Cycladophora davisiana and 230-Thorium analyses. Sediment facies distribution is controlled by numerous factors such as regional bathymetry and circulation, biogenic productivity, seasonal ice cover and the deposition of terrigenous detritus by ice-rafting, bottom water transport and/or slumping. The complex interrelationship between these factors results in three main categories of sediment facies. The diamict facies is interpreted as an interglacial facies. It is composed of clayey silt and silt and is characterised by a large component of coarse, ice-rafted material such as gravel and sand (IRD). This generally strongly bioturbated sediment contains radiolarian and diatom-rich layers as well as horizons of lower water and organic carbon content. Magnetic intensities, related to volcanic ash particles, glauconite, and micromanganese nodules as well as a large quantity of rock fragments, are low. The biosiliceous and IRD content decreases from north to south along the South Orkney transect because of seasonal ice margin fluctuations, thus resulting in barren and IRD-poor interglacial deposits in the southern region. Apart from ice-rafting and biogenic productivity, bottom currents also exert a strong control on the distribution of this facies. Strong and fluctuating bottom current influence is documented by the sediment structures in this facies. The homogenous clay facies was deposited during glacial periods. These silty clays are ...