A Reassessment of of the geochemical and isotopic fidelity of biogenic carbonates

Oxygen isotope compositions of calcite foraminifera tests are considered to be a robust palaeotemperature proxy at earth-surface conditions, where diffusion is slow. Recrystallization of tests during diagenesis may be optically identified and is often the basis for excluding such samples from paleotemperature calculations e.g. “glassy” vs. “frosty” foraminifera. However, biogenic and abiogenic calcite can isotopically reequilibrate and recrystallize in calcite-saturated fluids, even at low temperatures (