Towards an understanding of the Proterozoic carbon isotope curve

The carbon cycle is central to investigating Earth's past environment, particularly its oxygenation history. Past perturbations in the carbon cycle can be identified by changes in the carbon isotope composition (delta c thirteen) of ancient seawater, preserved in marine carbonate rocks. My project will involve collating unpublished and published carbonate delta c thirteen data from the Proterozoic (c. 2,500-539 Ma) to develop the first comprehensive carbon isotope curve for this Eon. New data will also be gathered via fieldwork (e.g., the Scottish Hebrides), extensive laboratory work and international collaboration. The carbon isotope curve will be supplemented with other geochemical proxies, allowing me to investigate weathering rates (Sr-isotopes), seawater redox conditions (U-isotopes) and productivity levels (Cd-isotopes) across key intervals. The geochemical data will be integrated with a biogeochemical model to predict the controls and evolution of the biotic and abiotic components of Earth's system throughout the Proterozoic, specifically across major perturbations in the carbon cycle (e.g., the Lomagundi and Shuram Excursions). The project aims to address key questions such as: 1) What were the dominant geological and/or biological drivers of the major carbon isotope excursions during the Proterozoic?; 2) Are carbon isotope excursions good indications for oxygenation events?; and 3) Was the Mesoproterozoic a time of carbon isotope stability and thus Earth system stasis?