ABSTRACT

Dr. Ola Kwiecien,
Institute for Geology, Mineralogy & Geophysics, Ruhr-Universität Bochum, Germany

Due to their natural occurrence in a wide spectrum of environmental settings (marine, lacustrine, terrestrial) carbonates constitute one of the most widely used archives of (paleo)environmental information. Still, the accurate reconstruction of past environmental parameters is highly dependent on our understanding of the strengths and interpretational limits of applied proxies. The geochemistry of lacustrine biogenic (skeletal) and authigenic carbonates is a well-established archive of hydrological changes. Its use, however, is often obscured by multiple controls on preserved signals; detrital contamination and/or diagenetic alteration. Lacustrine carbonate-based proxy data (stable isotopes d¹⁸O, d¹³C) may indicate reliably the timing, direction or the amplitude of environmental changes but rarely explain the underlying mechanisms in an unambiguous manner. Similarly, interpretation of new data often pays tribute to outdated assumptions. 

The challenge here consists in decoding different aspects of information, which can be teased out of the studied archive. The presentation will focus on two examples of puzzling lacustrine carbonate d¹⁸O data. The Black Sea and the Lake Van time series cover 26 and 340 ka, respectively. Comparing and contrasting isotopic information from the same stratigraphic horizon but carried by different hosts provide great opportunities to test our assumptions about particular lacustrine environment but also to examine strengths and limitations of carbonate-based isotope proxies in general.