Figure 1. Late Cretaceous temperature and δ¹⁸O_w at Seymour Island.

(a) Δ₄₇-derived temperature and (b) δ¹⁸O_w versus age. The timing of Deccan Traps volcanism⁷,³³ (orange rectangle) and two extinction pulses¹⁰ (black/orange stars) are shown for comparison. Coloured error bars on individual points represent 1 s.e. of the mean of many replicates or the long-term reproducibility of carbonate standards, whichever is larger (see Methods). Horizon averages in a,b were calculated as the inverse variance weighted mean, to account for variable reproducibility of samples, with thick grey error bars showing the inverse variance weighted error on the mean (see Methods). Black line connecting horizon means is dashed to represent extrapolation of temperature and δ¹⁸O_w trends between measured horizons. Samples within ±3.5 m stratigraphic position of another sample were combined into a single horizon for horizon means (see Methods). Grey horizontal line in a represents the freezing point (0 °C) and in b represents the ice free, latitude-adjusted seawater value of −1.2‰ (ref. ³⁰). Vertical grey dashed line denotes the KPg boundary (labelled KPB)³⁴. Age model construction is described in Methods. Data for this figure can be found in Supplementary Data 5 and 6.