Erratum.
As published, figure 2 in the report "Disruption of the terrestrial plant ecosystem at the Cretaceous-Tertiary boundary, western interior" by R. H. Tschudy et al. (7 Sept., p. 1030) contained two errors. The break in the stratigraphic column should have been 3 m, and the iridium concentration should have been in parts per trillion. The correct figure is reproduced below. [see figure in source PDF].