Stable Isotope Tracking: Water Cycles and Climates of the Past

Fractionation of stable hydrogen and oxygen isotopes within the hydrological cycle is of prime importance in stable isotope geochemistry as measurements of isotope compositions can help to identify water sources, to estimate the importance of phase changes and to quantify mixing, unmixing and distillation processes. The knowledge of parameters such as estimates of water, salinity, and stable isotope compositions of water reservoirs, opens windows to the dynamics of the past water cycle and consequently to the climate modes that prevailed on the Earth's surface. Marine-origin fossils may have been altered or transformed in response to the circulation of aqueous fluids of meteoric origin, with temperature, pH and Eh resulting from water–rock interactions, which make them able to dissolve the fossil biominerals. Hydrogen and oxygen isotope compositions of water inclusions in halite can be used to identify past fluid sources and mixing processes between water masses.