On the Trail of the Earth’s History with EDXRF - Katharina Wien, Prof. Dr. Horst D. Schulz, Martin Kölling I, Dirk Wissmann

Sedimentary accumulations on the seabed provide information about the earth’s most recent geological past, the Quaternary period. The properties of these sediments were affected by a variety of factors. Climatic and oceanographic conditions at the time played an important role in their formation. After formation of the sediment, however, the material is further affected by diagenetic modifications (biogeochemical processes), or by shift and transport processes. Stratigraphy, or subsurface geology, is concerned with describing the sequence of sediment layers, and provides a timescale for dating geological events. Element stratigraphy is one approach to the geochemical characterization of sediment sequences. The concentration of different elements, and the variations in their concentration, permit conclusions to be drawn both as to their origins and to the processes that lead to the enriched or depleted element levels.

For the first time, much of the geochemical investigation of the sediments was carried out while still on board during an expedition with the research ship METEOR in the waters off the South African coast. The data collected was used to generate an element stratigraphy soon after the samples were removed from the sea bed by the sediment corer. The analytical technique used was energy-dispersive X-ray fluorescence analysis with polarization excitement (EDPXRF). The simple and rapid sample preparation, and the high-performance of the SPECTRO XEPOS instrument used, allowed analysis for the elements Si, Ti, Al, Fe, Mn, Mg, Ca, K, Sr, Ba, Rb, Zn, S, Cl and Br to be carried out on more than 200 individual samples from one sediment core within 24 hours of taking the sample. The element profile could be interpreted immediately, and used for short-term decisions intended to optimize sample extraction, even as the expedition proceeded.