a, As in Extended Data Fig. 1a, except the youngest calcite subsampled for δ18Oc begins 40.25 mm from the tip; a hiatus immediately above this depth results in an abrupt transition into higher-232Th calcite (not shown). Dates plotted in blue were excluded from age model construction due to high 232Th concentrations, indicating relatively abundant non-radiogenic thorium and requiring larger age corrections with uncertain initial 230Th/232Th values. b,c, As in Extended Data Fig. 1b and c. The consistent, part per billion concentrations of included ages can be contrasted with the variable, higher-232Th character of excluded ages irrespective of depth.