Vollmar, Nele Manon; Baumann, Karl-Heinz; Saavedra-Pellitero, Mariem; Hernández-Almeida, Iván (2021): Relative abundances of coccolith species in surface sediment samples from Polarstern expedition PS97 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.932831

This dataset includes the relative abundances of coccolith species identified with a scanning electron microscope from surface sediment samples samples with a Multicorer during Polarstern Expedition PS97 (Lamy, 2016, doi:10.2312/BZPM_0701_2016), extending from the southern Chilean Margin towards the south across the Drake Passage. The uppermost centimetre of the multicores were sampled and prepared with a combined dilution/filtering technique following Andruleit (1996) doi:10.2307/1485964. Between 66 and 153 mg of dry bulk sediment per sample were suspended in demineralized water buffered with ammonia and ultrasonicated for up to 30 s. The suspensions were split to one-hundredth with a rotary sample divider, filtered through polycarbonate membrane filters with a pore size of 0.45 μm, and dried in an oven at 40 °C for 24 h. Out of the dried filters, a piece of approximately 1 cm² was cut out, mounted on an aluminium scanning electron microscope (SEM) stub, fixed with carbon conductive tabs and sputter-coated with gold-palladium. The filters were analysed with a Zeiss DSM 940A SEM at a magnification of 3000x. A minimum of 300 coccoliths per sample was counted in transects across the filter area, except for 5 relatively coccolith-poor samples south of the PF and one in the SAZ in which at least 100 coccoliths were counted. Datings of near-surface sediments at the southern Chilenean margin (Caniupán et al., 2011b, doi:10.1029/2010PA002049) as well as south of the PF within the DP (Vorrath et al., 2019, doi:10.1594/PANGAEA.897163) give calibrated accelerator mass spectrometry (AMS) 14C ages of 2.91 – 3.06 kyr BP and 4.83 kyr BP respectively. We therefore assume that our studied surface sediments represent relatively modern conditions, with ages ranging most likely from mid to late Holocene. Counting of coccoliths took place in 2020 in order to assess the recent to (sub-) fossil record of coccolithophores in the Drake Passage in the Southern Ocean.