June 22, 2017 @2 pm
Presenter: Dr. Grit Steinhöfel (Alfred Wegner Institute for Polar and Marine Research, Bremerhaven, Germany - Marine Biogeosciences)
The analytical developments in the past 15 years have enabled high precision, routine measurements of non-traditional isotopic ratios using MC-ICP-MS, in solution or in situ by laser ablation. Here, I present my analytical developments in Fe, Si, Mg, Li, B and Sr isotope analysis and show the application of these measurements to understand changes recorded in sediment archives and modern weathering processes.
Banded Iron Formations represent an extraordinary archive of the early Earth. High resolution Fe and Si isotope analysis by laser ablation unraveled signatures of the Precambrian ocean together with digenetic processes, suggesting coupled siderite and magnetite formation by reduction of ferrihydrite and oxidation of organic carbon.
Another unique sediment record is a shale sequence covering the Paleocene Eocene Thermal Maximum (PETM), which is considered as an analog to present-day global warming: Mg, Li and Sr isotopes in the related core indicate enhanced silicate weathering. In marine cores, B isotopes in foraminifera provide a unique record of atmospheric CO2.
Weathering, and the related element cycling, is the basis for life on Earth and regulates the atmospheric CO2 content over geological time scales. Small catchments represent ideal field laboratories to isolate and quantify weathering processes.
The investigation of Li isotopes in the Shale Hills Critical Zone Observatory (USA) and Si isotopes in a shale-sandstone catchment (Black Forest, Germany) decipher sessional dynamics of clay transformation processes and depletion of elements dominated by physical erosion.
The advanced analytical methods have enabled new insight into diverse Earth system processes. It is expected that further analytical developments will continue to contribute to our understanding of fundamental questions in Earth sciences.