PhD in Geographical & Earth Sciences: Clumped Isotopes as a Climate Proxy in Ecologically Important Scottish Tufas

Co-supervisors: Robert McCulloch (University of Stirling); Adrian Boyce (SUERC); Vanessa Kirkbride (Scottish Natural Heritage)

Tufas are terrestrial carbonate deposits that precipitate at ambient temperatures when CO2 outgasses from water, often at a spring or at some obstruction in a stream which causes water turbulence. Tufas are an important palaeoclimatic and palaeoenvironmental archive where seasonal temperature variation can be reconstructed through their δ18O. Palaeotemperature reconstruction through δ18O measurements can be hampered, particularly in fossil tufas, by having to make an assumption on the δ18O value of the spring water from which the fossil tufa precipitated. Recent work has shown that ‘clumped’ isotopes may be a viable climate proxy in tufas which avoids this assumption.

The main goal of this project is to test clumped isotopes as a seasonal temperature proxy in temperate climates through investigation of both active and fossil Holocene Scottish tufas.

Tufas (both active and fossil) are common but poorly documented in Scotland and so where they do occur they are often designated, ecologically important sites. Many rare, lime-loving (calcicole) species live in the moss carpet, particularly arcticalpine species, such as bird’s-eye primrose Primula farinosa, Scottish asphodel Tofieldia pusilla, alpine bartsia Bartsia alpina and false sedge Kobresia simpliciuscula. If tufas were to stop precipitating, for example due to climate change, these rare species would be threatened. It is therefore important to investigate these temperate Scottish tufas and better understand their precipitation histories relative to temperature changes.