An international crew of 40 scientists in June gathered the deepest sediment samples ever taken from underneath the Bay.

Researchers on the Marion Dufresne drilled up to 77.5 feet below the bottom of the Bay to collect the samples, which reveal how climate changes affected it over the last 11,000 years. Using the data, scientists said, they hope to predict how future climate changes and the use of surrounding land will affect the Chesapeake.

Crews drilled so deeply, they churned past layers of sediment that formed the earliest bed of the Bay, scientists said. They set a record by reaching layers of the bed of the ancient Susquehanna River—the ancestor of the Chesapeake Bay. The yards-long tubes of sediment, called “cores,” are cut into pieces 1.5 meters long and sliced in half for research.

“You’re basically reading a history book,” said Tom Cronin, one of seven U.S. Geological Survey scientists on the French ship. “The sediment may not look like much, but there are dozens and dozens of fossils and microscopic organisms to study.”

The Marion Dufresne has been traveling since May 5, collecting cores off the coasts of Brazil and Jamaica, in the Cariaco Basin near Venezuela and the Gulf of Mexico. The mission, led by Carlo Laj of France’s National Center for Scientific Research, aims to understand how oceans affect global climate change. It will be a year before geologists have preliminary results of their Chesapeake Bay cores, said USGS scientist Debra Willard.