San Juan Basin

For the San Juan River Watershed, see San Juan River.

The San Juan structural basin is primarily in New Mexico and the southeast corner of the Colorado Plateau.

The San Juan structural basin is generally the east portion of the San Juan River Watershed of 24,600 sq mi (64,000 km²) which extends farther west into Utah and Arizona.

The San Juan Basin is a geologic structural basin in the Four Corners region of the Southwestern United States; its main portion covers around 4,600 square miles (12,000 km²), encompassing much of northwestern New Mexico, southwest Colorado, and parts of Arizona and Utah.

The region is arid with rugged topography of plains and valleys interspersed by buttes, canyons and mesas. Its most striking features include Chaco Canyon (northwestern New Mexico, between Farmington and Santa Fe) and Chacra Mesa. The San Juan Basin also has uplands that exceed elevations of 9,800 feet (3,000 m). Drainage in the structural basin is general westward from the Continental Divide of the Americas to the Mancos River's confluence with the San Juan River. The San Juan River then continues to the Colorado River.

Geology

The San Juan structural basin is a large downwarp of sedimentary rocks of mostly Mesozoic age. As a geologic region, the San Juan Basin is noted for its large deposits of coal, uranium, and natural gas. Since the 1980s, the Fruitland Formation in the basin has been one of the major US sources of coalbed methane. In 2007, the San Juan Basin produced 1.32 trillion cubic feet of natural gas, making it the largest source of natural gas in the United States. Uranium mining in New Mexico is also performed from the San Juan Basin.

Methane cloud

In 2014 NASA researchers reported the discovery of a 2,500 square miles (6,500 km²) methane cloud floating over the Basin. The discovery was based on data from the European Space Agency’s Scanning Imaging Absorption Spectrometer for Atmospheric Chartography instrument from 2002 to 2012.

The report concluded that “the source is likely from established gas, coal, and coalbed methane mining and processing.” The region emitted 590,000 metric tons of methane every year between 2002 and 2012—almost 3.5 times the widely used estimates in the European Union’s Emissions Database for Global Atmospheric Research.