Early days of carbon isotope geochemistry in paleoceanography and limnogeology - tales from Judy’s ETH Lab

 

Fundamentals of C-isotope geochemistry were established in the mid-1950s. Its use as a proxy in paleoceanography and paleoclimatology was long underestimated. While oxygen isotope geochemistry was identified early as a powerful tool in Ice Age history, carbon isotope geochemistry evolved only in the 1970s into a valuable instrument in paleoceanography and paleolimnology.  In 1976, Judy McKenzie was offered the chance to build the first stable isotope lab at ETH Zürich. Judy was, together with her team, among the first geoscientists searching for applications of C-isotope geochemistry in paleoceanography and limnogeology. Seasonal fluctuations in lake productivity were monitored in C-isotope composition of lake sediments and C-isotope records measured in pelagic carbonates served as a tracer of circulation and productivity in Cenozoic and Mesozoic oceans. In the eighties C-isotope geochemistry was recognized as a proxy of the global carbon cycle and its history was traced in C-isotope records measured in pelagic carbonates. The ETH Lab contributed with the several publications on C-isotopes and the carbon cycle to the seminal Chapman conference on “The Carbon Cycle and Atmospheric CO₂: Natural Variations Archean to Present” (Florida, 1984). An improved understanding of marine carbon fractionation processes allowed to use paired carbonate and organic carbon isotope analyses as a proxy for past atmospheric carbon dioxide concentrations. Today C-isotope geochemistry is established as a most valuable tool in paleoclimatology and paleoceanography, in sedimentology and geomicrobiology.