Timing of the ethiopian flood basalt event and implications for plume birth and global change

Abstract

Continental flood basalts are often considered as fossil evidence of mantle plume heads impinging on the lithosphere and have been related to continental breakup. Many of these flood basalts erupted within a short time span-of the order of 1 Myr-and were apparently synchronous with crises in global climate and with mass extinctions. Here we present geochronological (40Ar/39Ar) and magnetostratigraphic results for the Ethiopian traps, one of the last remaining flood basalts for which few such data were available. The bulk of the traps, which have been inferred to mark the appearance of the Ethiopian-Afar plume head at the Earth's surface, erupted approximately 30 Myr ago, over a period of 1 Myr or less. This was about the time of a change to a colder and drier global climate, a major continental ice-sheet advance in Antarctica, the largest Tertiary sea-level drop and significant extinctions.