COMPASS

Radiocarbon (14C) is a powerful tool that has paved the way for major scientific breakthroughs in geochronological research and studies of the carbon cycle. Most commonly, bulk phases (e.g., particulate or dissolved organic matter) of environmental samples have been analyzed, even though they may comprise organic carbon derived from various sources. The presence or admixture of pre-aged components in a sample and/or the lateral transport or reworking of sample material within a stratigraphic sequence may further complicate the interpretation of measured 14C. A more precise and detailed level of understanding of the 14C age can be achieved by analyzing specific components from such heterogeneous mixtures, such as individual compounds or small organic or inorganic particles of well-defined origin, a challenge that has so far been hampered by analytical limitations, mainly due to the low availability of selected sample materials.
A very fruitful and long-lasting collaboration between the Biogeoscience group and the Laboratory of Ion Beam Physics has previously demonstrated that even smallest amounts of carbon can be analyzed precisely for 14C. Based on this we will develop two new analytical methods that will permit analyses of specific compounds and particles:

• Isolation of specific compounds via chromatographic methods (HPLC, GC) in combination with micro-sublimation
• Separation of specific particles (pollen, coccoliths) via flow cytometry

These methods will then be applied to

• Comparison of proxy-specific 14C chronologies in laminated sediments
• Age-relations of different proxy-carriers (foraminifera, alkenones, coccoliths) in ocean sediments

These advances will allow for more secure 14C dating, which is the backbone for any paleo-climatic work covering the last 45’000 years.

Project member

• Caroline Welte