INVESTIGATING THE IMPACT OF VOLCANOGENIC INPUT ON REDOX PROXIES IN THE SCOTIA SEA

Specific trace metals are useful tracers to reconstruct and understand changes in oxygen conditions in marine environments. However, near active ridges, hydrothermal vent fluids and volcanic ash can potentially overprint these proxies. The focus of this study was to investigate sediments (Site PS119_48) collected from the eastern part of the Scotia Sea during Expedition PS119 on the R/V Polarstern for their trace metal abundance. The site is located between the East Scotia Ride east of segment E2 and the South Sandwich Island Arc. The different redox metals such as molybdenum (Mo), uranium (U), and vanadium (V), as well as major elements such as aluminum (Al) and iron (Fe) were analyzed via a multi-acid total digest technique followed by inductively couple plasma mass spectrometry. Additionally, to identify the amount and types of siliceous microfossils and ash layers that were deposited at this site scanning electron microscopy was applied. Our results show that the investigated sediment core is characterized by layers of volcanic ash input (dark layers) and siliceous ooze material. The amount of Fe, Al, and V present in the sediments are highest around 21-24 cm deep coinciding with dark-colored deposits. Overall, V mirrors the trend of Al and Fe suggesting mainly detrital / volcanogenic input. The amount of Mo and U present in the sediments are highest in the uppermost layers likely tied to manganese and Fe cycling. Our results indicate that in specific layers some redox-proxies (V) appear overprinted by volcanic ash and vent fluids while others such as Mo and U are mainly altered by early diagenetic changes.