Extended Data Fig. 1: Age model constraints below 75 mbsf at Site U1521.

From left to right are: depth (metres below sea floor), core number, core recovery (black = recovered), inclination before and after 10 and 20 mT demagnetisation (black, blue and red points, successively), and corresponding polarity interpretations (black = normal, white = reversed, grey = no interpretation). Note that the polarity interpretations have been simplified compared to those in the cruise report²⁶, with small uncertainties related to core gaps removed. Note Site U1521 is in the Southern Hemisphere. The geomagnetic polarity timescale⁴⁹ is shown across the top of the plot. The orange shaded regions indicate uncertainties in our age model and the dashed line marks an alternative line of correlation for Sequence 3. The blue line indicates the age model for Sequence 2 based on our astrochronological analyses, with the light blue shading indicating the ~20 kyr uncertainty associated with the phase relationship between clast abundances and obliquity. This astrochronological anchoring agrees closely with linear interpolations between magnetostratigraphic tie points (black line).