Stable isotope and trace element ratios of bulk sediment and planktic foraminifera in ODP Hole 121-758A and IODP Hole 353-U1443A

Here we present the first long-term sub-eccentricity-resolution stable isotope (δ13C and δ18O) and trace element (Mg/Ca and B/Ca) records spanning the late Paleocene–early Eocene (~58–53 Ma) from a surface–deep transect of the northern Indian Ocean, resolving late Paleocene 405-kyr paced cyclicity and a portion of the PETM recovery.

Our new records reveal a long-term warming of ~4–5°C at all depths in the water column, with absolute surface ocean temperatures and magnitudes of warming comparable to the low latitude Atlantic and Pacific. As a result of warming, we observe a long-term increase in δ18Osw of the mixed layer, implying an increase in net evaporation. We also observe a collapse in the temperature gradient between mixed layer- and thermocline-dwelling species, potentially due to either the development of a more homogeneous water column with a thicker mixed layer, or depth migration of the Morozovella in response to warming.