Constraining the early diagenetic alteration of non-marine ostracodes and assessing its impact on paleoenvironmental reconstructions

• Applicant: Professorin Dr. Claudia Wrozyna
• Subject Area: Palaeontology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547770304

Our knowledge on past climatic and environmental changes greatly benefited from the development of geochemical proxies analyzed on biogenic carbonates, in both marine and continental realm. However, primary environmental signals can be altered by various diagenetic processes occurring contemporaneously or soon after sediment deposition. While this is well-documented for marine carbonates, only few studies examined diagenetic overprinting of pristine geochemical signatures of lacustrine carbonates. Despite various differences in, e.g., fluid composition, mineralogy of skeletons and shells of metabolizing organisms, and habitat conditions it is generally assumed that early diagenetic processes have no effect on (isotope) chemical signatures of lacustrine carbonates. This is, however, not verified by field and/or laboratory experiments. In lacustrine environments, ostracodes (Arthropoda, class Crustacea) represent one of the most important skeletal carbonate-forming organisms. As a result, analyses of isotopic and elemental compositions of ostracode valves of low-Mg calcite became a standard method in paleolimnological investigations within the last decades. However, limitations for their utilization as geochemical archive have not yet been investigated systematically. The main aim of the project is to identify the influence of syn – and post-sedimentary conditions on the preservation of geochemical compositions of non-marine ostracodes. An important task represents the identification of the relationship between valve preservation and geochemical alteration features. Our integrated experimental and field-site approach is focused on identifying and assessing potential constraints of ostracode calcite to be used as geochemical archive for reconstructions of paleolimnological and climatic changes. To achieve these goals, we suggest investigations of the structural and geochemical characteristics of modern and fossil ostracode valves by using different imaging techniques and analyses of δ18O, δ13C and trace elements. A better understanding of the processes involved in diagenetic alteration of lacustrine ostracode calcite will be achieved by the laboratory alteration of modern ostracode valves under controlled conditions. Using different set-ups, these experiments aim to constrain the role of the substrate in its role to be reactive (i.e., carbonate minerals, organic matter) or less-reactive (clay minerals), e.g. to seal ostracode calcites. Additionally, investigations of fossil valves will provide a reference set of features with which the experimental results can be compared.

• DFG Programme: Research Grants
• International Connection: Austria
• Co-Investigator: Professor Dr. Laurence Noel Warr
• Cooperation Partner: Professor Dr. Martin Dietzel