Coal, petroleum, and natural gas are derived from the partially decomposed remains of ancient organisms included within sedimentary rocks. For this reason, they are called fossil fuels. Fossil Fuels are the primary sources of energy for our industrial economy. Eighty-seven percent of the energy consumed in the United States is derived from the fossil fuels.
The Carboniferous contains tremendous reserves of coal, but rocks of Mesozoic age also have significant amounts of coal, as well as oil and natural gas. The Jurassic System, for example, contains workable deposits of coal in Siberia, China, Australia, Tasmania, Spitzberger, and North America.
In North America, thick seams of Jurassic coal occur in British Columbia and Alberta. Cretaceous coal underlies more than 300,000 km2 of the Rocky Mountain region [Mesaverde Formation (upper Cretaceous) near Castlegate, Utah]. Much of this coal is now being mined, particularly because of its relatively low content of envornmentally offensive sulfur.
In addition to coal, Mesozoic rocks supply large quantities of oil and gas to energy-hungry industrial nations. The oil provinces of the Middle East and North Africa contain more oil than the combined reserves of all other countries.
Middle East petroleum comes primarily from thick sections of Jurassic and Cretaceous sedimentary rocks that accumulated in shelf and reef environments bordering the Tethys seaway. Other areas of petroleum production from Mesozoic rocks occur in the western United States, Alaska, Arctic Canada, the Gulf Coastal states, western Venezuela, Southeast Asia, beneath the North Sea, and beneath the eastern offshore area of Australia.
Notwithstanding the size of some recent discoveries in rather forbidding parts of the world, it appears likely that the present rates of oil and gas consumption will cause exhaustion of the world's resources in less than a century. Therefore, oil and gas must be replaced by other energy sources in the future, especially if we are to conserve these valuable materials for the chemical industry. The time will come when petroleum may be too valuable to burn.
The oil or gas content of a single deposit is called an oil pool or gas pool. A group of pools on a single geologic feature, or otherwise closely related, is called a field.