BEIJING, July 17 (Xinhuanet) -- Research published Thursday said it was the violent volcano eruptions that caused a shift in ocean circulation and preceded the extinction of marine life nearly 93 million years ago.

    The extinction was so spectacular that the remains of the tiny victims littered the sea bed in thick layers, and over geological time became transformed into oil.

    The team estimates that it took up to 23,000 years for the pulse of volcanic activity to have its effects.

    Two theories, which are not mutually exclusive, emerge to explain the chemistry of what happened next.

    One is that the volcanoes spewed out metal-rich fluids that provided food for the phytoplankton in the upper level of the ocean. The phytoplankton stored up carbon and then sank to the sea floor and decayed, stripping the ocean of oxygen.

    The other is that the volcanoes disgorged clouds of carbon dioxide to the atmosphere, which made the ocean suddenly starved of oxygen, wiping out swathes of marine life.

    Figuring out the post-volcanism scenario could help scientists wrestling with unknowns about global warming today, said Tim Bralower, a geologist at Pennsylvania State University, who reviewed the paper.

    (Agencies)