Fig. 1: Location maps of the North Atlantic Igneous Province (NAIP) and sediment cores sites analysed in this study.

The simplified NAIP main map shows the estimated ranges of its various components⁶¹. ‘Seaward dipping reflectors’ are well-defined seismic reflectors beneath the uppermost basalt, interpreted as large subaerial sheet lava flows associated with rifting⁶¹. Other lava flows are thought to be a combination of subaerial and submarine, and sills were considered as intruded into the upper crust^4,12,61. The insert map is a Mollweid projection of modern continents (lines) on a palaeogeographic reconstruction, generated from (ref. ⁶²), of continental plates (grey) centred at 56 Ma.