A plume of oil some 700 feet thick and at least 22 miles long has been detected deep beneath the Gulf of Mexico. It originated at the Deepwater Horizon blowout and consists of hydrocarbons from the well, according to measurements released Thursday.

The survey, conducted by US and Australian scientists during a 10-day research cruise in late June, represents the most detailed picture yet of undersea plumes of oil and methane from the Gulf oil spill. The researchers were surprised by the plume's relative stability as well as by an apparent lack of activity on the part of microbes to break down the oil.

The continuous plume appeared some 3,000 feet below the surface, according to data published Thursday afternoon in the journal Science's online outlet, Science Express.