- 1Carl von Ossietzky University of Oldenburg , Institute for chemistry and Biology of the Marine Environment, Marine Isotope Geochemistry, Oldenburg, Germany (anjana.gireesh.sandhya@uni-oldenburg.de)
- 2Department of Geography and Environmental Sciences, Northumbria University Newcastle, Newcastle-upon-Tyne, NE1 8ST, UK
- 3Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK
- 4Department of Ecology and Environmental Science, University of Umeå, Linnaeus väg 4–6, 907 36 Umeå, Sweden
The Paleocene Eocene thermal Maximum (PETM) was a rapid global warming event, which occurred ~ 56 million years ago and lasted for ~200 ka. It is characterized by a massive rapid input of 13C-depleted carbon into the atmosphere and ocean, causing a 2-7‰ negative carbon isotope excursion (CIE). As a result of high atmospheric CO2 levels, high temperatures, and an enhanced hydrological cycle during the PETM, increases in physical and chemical weathering intensity have previously been reconstructed across the globe. Chemical weathering of silicate rocks predominates in humid climates and significantly influences the major and trace element composition of resulting sediments. Numerous studies suggest that the intensified chemical weathering of silicate rocks occurred during the PETM, driven by the warm conditions and enhanced hydrological cycle.
Here we present the first results of elemental geochemical analysis of sediment samples collected from the mid-Norwegian margin during IODP Expedition 396. Our initial results focus on variations in chemical weathering across the PETM as inferred from geochemical proxies.
In the samples examined here, chemical index of alteration (CIA), a proxy for chemical weathering intensity, values show a sharp drop from pre-PETM to mid-PETM. In contrast to other locations, these observations suggest a shift in the intensity of weathering from intermediate to weak and indicates chemical weathering was not intensified during the PETM in our study region. As this is opposite to previous studies, we consider whether changes in sediment provenance may explain these data. However, the provenance discrimination plots (La-Th-Sc ternary diagram Th/Co vs. La/Sc bivariate plot) shows mixed source with no clustering regardless of the time period. This indicates that the sediment source of the Vøring basin did not change at the PETM onset and we suggest that our CIA data truly represent a decrease in the intensity of chemical weathering during the PETM in the Vøring Basin.
How to cite: Sandhya, A. G., Pahnke, K., Longman, J., Frieling, J., and Jones, M. T.: Low chemical weathering intensity in the Vøring Basin during the Paleocene-Eocene Thermal Maximum, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9334, https://doi.org/10.5194/egusphere-egu25-9334, 2025.
