have spewed poisonous levels of sulphur and carbon dioxide into the atmosphere and caused the mass extinction through the resulting global warming and ocean acidification.
The findings are the latest volley in an ongoing debate over whether an asteroid or volcanism killed off the dinosaurs about 65 million years ago in the mass die-off known as the K-T extinction, the 'Live Science' reported.
"Our new information calls for a reassessment of what really caused the K-T mass extinction," said Gerta Keller, a geologist at Princeton University, who conducted the study.
For several years, Keller has argued that volcanic activity killed the dinosaurs.
However, proponents of the Alvarez hypothesis argue that a giant meteorite impact at Chicxulub, Mexico, around 65 million years ago released toxic amounts of dust and gas into the atmosphere, blocking out the Sun to cause widespread cooling, choking the dinosaurs and poisoning sea life.
The meteorite impact may also have set off volcanic activity, earthquakes and tsunamis.
The new research "really demonstrates that we have Deccan Traps just before the mass extinction, and that may contribute partially or totally to the mass extinction," said Eric Font, a geologist at the University of Lisbon in Portugal.
In 2009, oil companies drilling off the Eastern coast of India uncovered eons-old lava-filled sediments buried nearly 3.3 kilometers below the ocean surface.
Keller and her team found they contained plentiful fossils from around the boundary between the Cretaceous-Tertiary periods, or K-T Boundary, when dinosaurs vanished.
The sediments bore layers of lava that had travelled nearly 1,603 km from the Deccan Traps.
The volcanic region, today, spans an area as big as France, but was nearly the area of Europe when it was active during the late Cretaceous period, said Adatte Thierry, a geologist from the University of Lausanne in France.
Within the fossil record, plankton species got fewer, smaller and maintained less elaborate shells immediately after lava layers, which would indicate it happened in years after the eruptions.