In the past decade, the stable isotope toolkit available to paleoclimate researchers has doubled to include clumped isotopes (Δ47) and triple oxygen isotopes (Δ17O), in addition to the traditional carbon-13 (δ13C) and oxygen-18 (δ18O) systems. In clumped isotope thermometry, our laboratory group has explored a fundamental aspect of the system for elevated temperature environments of the shallow-crust: solid-state reordering of carbon-oxygen bonds. Through theory, experiment, and empirical validation, we have determined temperature-dependent rates of reordering that allow prediction of carbonate clumped isotope compositions through heating and cooling circuits. An important application of these results is the “screening” of the Phanerozoic record of seawater temperature and δ18O from clumped isotopes. The screened record suggests tropical seawater temperatures in excess of 35 °C during intervals of the Paleozoic, general coupling of seawater temperature and carbon dioxide levels throughout the Phanerozoic, and no secular change in ocean oxygen isotope composition during this time.

Triple oxygen isotopes in terrestrial environments record aspects of evaporation and aridity, and in vertebrate biogenic carbonates also have stories to tell about deep-time carbon cycling. We have developed a novel analytical method that for the first time permits high-precision triple oxygen isotope analysis of carbonates and of the carbonate component of bioapatite. I will present preliminary results for lacustrine carbonates, bird & dinosaur eggshell, and mammalian tooth enamel, interpreted in terms of water balance ecology, climate (aridity), atmospheric O2/CO2 ratios, and global gross primary productivity.