	Site Map \| FAQ in Daily Almanac for Feb 10, 2012
Skip Navigation Home Black History Month Atlas Encyclopedia Dictionary Thesaurus Features Quizzes Timelines Countries

Fact Monster Kid's reference,
games, quizzes

Editor's Favorites

| Share

Encyclopedia—petroleum

Origin and Natural Occurrence

During the past 600 million years incompletely decayed plant and animal remains have become buried under thick layers of rock. It is believed that petroleum consists of the remains of these organisms but it is the small microscopic plankton organism remains that are largely responsible for the relatively high organic carbon content of fine-grained sediments like the Chattanooga shale which are the principle source rocks for petroleum. Among the leading producers of petroleum are Saudi Arabia, Russia, the United States (chiefly Texas, California, Louisiana, Alaska, Oklahoma, and Kansas), Iran, China, Norway, Mexico, Venezuela, Iraq, Great Britain, the United Arab Emirates, Nigeria, and Kuwait. The largest known reserves are in the Middle East.

Sections in this article: