Project description
Understanding how the earth's timepiece is made
Geochronology, or the dating of the earth's materials and events, is essential to understanding our planet's history, including earthquakes, environmental changes, volcanic eruptions and the formation of mountains and continents. Dating is typically based on radioactive decay. The uranium-to-lead (U-Pb) decay process consists of two parallel pathways that run at different rates, providing a natural verification of results, and boundstone is often the sample of choice. A type of carbonate, it has emerged as an excellent geological 'timepiece' suited to U-Pb dating techniques, but it is a black box – we do not know much about it. The EU-funded CARBCHRON project is testing its hypothesis regarding boundstone formation. Experiments should elucidate detailed processes, leading to a better understanding and interpretation of its use as a geochronometre.
Objective
Recent analytical developments are reinvigorating the study of carbonate as a geochronometer in deep time (>1 Ma) using the U-Pb system. Boundstone, a type of carbonate rock made by the trapping and binding of carbonate sediment by microbial mats, is often sampled for use in U-Pb dating of carbonates. It has even been used as a reference material in recent studies. However, we lack a process-based understanding as to why boundstone works so well for geochronology, and which geological processes create the material we date. This work, supervised by Dr. Axel Gerdes at Goethe University Frankfurt, investigates these questions. This project tests a hypothesis, supported by early results, that microbially-induced carbonate precipitation under reducing conditions creates geochronologically viable early cements. This hypothesis will be tested by petrographically, geochemically, and geochronologically characterizing boundstones from Earth’s last 1 Ga. To test the accuracy and robustness of the boundstone chronometer, I then will compare boundstone dates with radiometric ages derived from zircon and black shales in two stratigraphic succesions: the Neoproterozoic of Oman and the Ordovician of Anticosti Island. First, boundstone samples will be characterized petrographically. High-throughput laser ablation inductively coupled mass spectrometry (LA-ICP-MS) will be used to geochemically and geochronologically characterize samples, a subset of which will advance to high-precision dating by isotope dilution (ID).
Fields of science
Programme(s)
Funding Scheme
MSCA-IF - Marie Skłodowska-Curie Individual Fellowships (IF)Coordinator
60323 Frankfurt Am Main
Germany