by Andy May, November 4, 2017

¹⁸O is a rare isotope of oxygen. The ratio of ¹⁸O to the normal ¹⁶O in foraminifera fossils (“forams”) can be used to estimate paleo-ocean temperatures. Higher values mean lower temperatures. A recent article on geologypage.com (here) led me to Bernard, et al., 2017, which has experimental data that suggest ¹⁸O concentrations can be altered in fossils by solid-state diffusion after fossilization. This can corrupt the measurement and the resulting calculated temperature