Final answer:
The Deccan eruptions occurred during the late Cretaceous period and contributed to the mass extinction at the Cretaceous-Paleogene boundary alongside the Yucatan asteroid impact.
Step-by-step explanation:
The Deccan eruptions in India and the large volumes of flood basalt in southern Brazil were part of widespread volcanic activity during the late Cretaceous period. This period at the end of the Cretaceous (~66 million years ago) coincides with the Yucatan asteroid impact, which together with massive volcanic eruptions, significantly contributed to the mass extinction event at the Cretaceous-Paleogene boundary. The Deccan Traps in India are particularly notable for the large area they cover and the extensive release of volcanic gases such as sulphur dioxide, which have been implicated in causing dramatic climate changes.