Stable isotopes of early Eocene limestone at Branch Stream, New Zealand

Decimetre-scale limestone-marl couplets comprise the section. Several marl-rich intervals correspond to carbon isotope excursions (CIEs) representing increased 13C -depleted carbon fluxes to the ocean.

These records are similar to those at nearby Mead Stream, except marl-rich intervals at Branch Stream are thicker with a wider d13C range. Comparison to other sites indicates the section spans ~53.4-51.6 Ma, the onset of the Early Eocene Climatic Optimum (EECO). The most prominent CIE is correlated with the K/X event (52.9 Ma).