- Home
- MARUM Research Seminar 2023
- Marta Marchegiano
The ostracod clumped-isotope thermometer: a novel tool to reconstruct quantitative continental climate changes
In many modern and ancient lakes, ostracod shells constitute the only carbonates capable to record climatic and environmental changes at high-resolution. Ostracods are small aquatic crustaceans (mostly 0.3-5 mm) with a stable low-Mg calcite shell mineralogy, which makes them ideally suited for targeted geochemical analyses. Therefore, ostracods represent the best candidate to develop a new carbonate clumped isotope (∆47) lacustrine paleothermometer able to disentangle the effects of global climate changes at regional scale. The relationship between ∆47 and the temperature at which ostracod shell crystallized, is determined by measuring ∆47 on different species grown under controlled temperatures in both natural environments (4 ± 2°C; 12 ± 1°C) and lab cultures (23 ± 0.5°C).
Clumped analyses were performed at the Vrije Universiteit Brussel (AMGC-VUB lab) using a Nu Instruments Perspective-IS stable isotope ratio mass spectrometer in conjunction with a Nu-Carb carbonate sample preparation system. The strong agreement between ostracod data and previous published calibrations demonstrate that clumped-isotopes technique can be applied to ostracod shells. No consistent offset between the two species originating from the same environment and precipitated at the same temperature is reported, suggesting the absence of a vital effect in ostracod ∆47. A first application made on a record from the shallow Lake Trasimeno (Italy), that cover the last ca. 43’000 years, allowed to identify warmer/colder and humid/dryer conditions during Greenland Interstadial and Greenland Stadial respectively. The ostracod-∆47 thermometer constitutes a reliable tool for continental palaeoclimate reconstructions. It can be applied to all ostracod species, facilitating the recovery of the required carbonate amount, and can be widely used in freshwater systems in all climatic belts.