Quantifying trends and transitions in a Miocene benthic δ ¹⁸ O stack

<jats:p>Abstract. Marine isotopic records from benthic foraminifera are central to understanding Miocene climate, but developing reliable Miocene age models that are consistent across sites has been challenging due ambiguities in biostratigraphy and magnetostratigraphy. Detailed chemostratigraphic alignment of globally distributed marine records can assist in comparing paleoclimate proxy records and their proposed forcing mechanisms. We present a continuous benthic δ18O stack (average) across the Miocene based on alignment of published records from 24 sites. Stack estimates of global mean benthic δ18O changes may improve reconstructions of Miocene ice volume change and deep-sea cooling and help distinguish between causal mechanisms. We estimate the rate of change in the global stack’s benthic δ18O throughout the Miocene as well as the amplitude of abrupt transitions associated with the onset of the Miocene Climatic Optimum (MCO) and the Middle Miocene Climatic Transition (MMCT). We find that the global stack’s change in benthic δ18O across the abrupt onset of the MCO at ~16.9 Ma is 0.27 ‰, which is about half the amplitude recorded in the deep Eastern Equatorial Pacific (EEP) and in the CENOGRID splice (Westerhold et al., 2020). We additionally find the total change in stack benthic δ18O across the Miocene is 0.82 ‰, which is 15 % less than in the CENOGRID splice.</jats:p>