Clay Mineralogy of Miocene to recent sediments collected at Site U1521 during International Ocean Discovery Programme (IODP) Expedition 374 to the Ross Sea, Antarctica

Samples were first decarbonated using 0.1N HCl and deflocculated through repeated washing using pure water. To isolate the clay-size fraction (<2 µm), differential settling was employed according to Stoke’s Law and then the sample was concentrated using a centrifuge for 40 minutes at 3500 rotations per minute. An aliquot was then placed on glass slides, before X-ray diagrams were obtained using a Bruker D4Endeavor (standard 30 kV and 30 mA). Each sample was run between 2.49 and 32.5°2θ with a step size of 0.08°2θ (total of 369 steps) and integration time of one second. Sample were run in three different ways: 1) air-dried, 2) glycolated (12 hours in ethylene glycol), and 3) heated at 490°C for 2 hours . The relative fraction of smectite, chlorite, illite and kaolinite is determined using the main X-ray diffraction peaks (layer and interlayer) on X-ray spectra according to their crystallographic characteristics (Beny et al., 2020, QSR). Illite is readily identified using its main peak at 10 Å on all three runs. Smectite is characterized by a main peak at 14-15 Å on the air-dried samples that expands at 17 Å after ethylene glycol saturation and collapses at 10 Å with increasing heating. Kaolinite and chlorite both have a dominant peak at 7-7.2 Å, with pseudo-void deconvolution of the kaolinite/chlorite doublet at 3.54/3.58 Å required to distinguish between them. All measurements and semi-quantitative estimations are processed using the MacDiff software (Petschick, 2004). To distinguish between Fe/ Mg-rich vs Al-rich illite, the Esquevin index was also employed (Esquevin, 1969), which corresponds to the ratio between the intensity of the peak of illite at 5 Å and at 10 Å (illite 5Å/10Å). The crystallinity of illite was measured using the method of integral breadth (Petschick et al., 1996, Marine Geol.), with high crystallinity implying poorly crystallized mineral.

INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology

Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services