Opal concentrations measured in sediment samples collected during the IN2017-V01 voyage of the RV Investigator

Brief description

Sediment cores were collected from the East Antarctic margin, aboard the Australian Marine National Facility R/V Investigator from January 14th to March 5th 2017 (IN2017_V01; (Armand et al., 2018). This marine geoscience expedition, named the “Sabrina Sea Floor Survey”, focused notably on studying the interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles. The cores were collected using a multi-corer (MC), were sliced every centimetre, wrapped up in plastic bags, and stored in the fridge.

Sediment samples were dried in an oven at 40°C and ground using a pestle and a mortar. Biogenic silica (or ‘opal’) analysis was carried out following modification of the protocol of Mortlock and Froelich (1989). About 30 mg of sediment was leached with 30 mL of 1M sodium carbonate (Na2CO3) for 5 hours at 80°C. Every hour, 1 mL of sample was removed and centrifuged at 10,000 rpm for 30 sec. A 200 µL aliquot was removed from the supernatant and diluted 50x with Milli-Q water for SiO2 determination by molybdate-blue spectrophotometry. A standard calibration was prepared by dilution of a SiO2 standard solution (sodium hexafluorosilicate, from 0 to 200 µM). The opal concentrations were calculated using the slope of the last three points of the dissolution curve (Demaster, 1981), or the changing slope part of the curve.

References
- Armand, L. K., O’Brien, P. E., Armbrecht, L., Baker, H., Caburlotto, A., Connell, T., … Young, A. (2018). Interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles (IN2017-V01): Post-survey report. ANU Research Publications.
- Demaster, D. J. (1981). The supply and accumulation of silica in the marine environment. Geochimica et Cosmochimica Acta, 45, 1715–1732.
- Mortlock, R. A., and Froelich, P. N. (1989). A simple method for the rapid determination of biogenic opal in pelagic marine sediments. Deep-Sea Research Part I, 36(9), 1415–1426.

Lineage

Progress Code: completed

Statement: Samples were typically analysed in batches of 24 and bracketed by a silicon standard (ACR standard silicon solution number: 0745), run twice every hour to correct for instrumental drift. At least one standard (typically the in-house standard ‘Chile’) was included in every analysis batch to monitor long-term reproducibility.

Notes

Purpose
These data were collected in order to determine the opal content of marine sediment from Wilkes Land margin, to reconstruct past productivity.