The expedition aboard the scientific drill ship JOIDES Resolution, which ended in late October, also revealed that vast areas of the Pacific Ocean were low in oxygen for periods of up to a million years each, said Dr. Timothy Bralower. A marine geologist, Bralower is professor and chair of geological sciences at the University of North Carolina at Chapel Hill.
These ocean-wide anoxic events were some of the most radical environmental changes experienced by Earth in the last several hundred million years, he said.
Along with Dr. Isabella Premoli-Silva, a micropaleontologist and stratigrapher at the University of Milan, Bralower served as co-chief of the two-month expedition. Drilling took place on Shatsky Rise, an underwater plateau more than 1,000 miles east of Japan. Its purpose was to better document and understand past global warming.
In geologic time, episodes of warming began almost instantaneously -- over a span of about a thousand years, Bralower said.
Warming bursts may have been triggered by large volcanic eruptions or submarine landslides that released carbon dioxide and methane, both greenhouse gases, he said. Besides reducing the oceans oxygen-carrying capacity, warming also increased the waters corrosive characteristics and dissolved shells of surface-dwelling organisms before they could settle to the bottom.
In some especially striking layers of black, carbon-rich mud, only the remains of algae and bacteria were left, he said.
The sheer number of cores that reveal the critical warming events found on this expedition -- three from the 125-million-year event and 10
Contact: David Williamson
University of North Carolina at Chapel Hill