The coal-bearing strata of Argentina, Bolivia, and Chile crop out along the flanks of the Andes Mountains. Carboniferous coals are known in Argentina from the provinces of San Juan, Mendoza, Neuquén, and Chubut. The Middle and Upper Carboniferous coals are anthracite. Permian coals are known from the provinces of Córdoba, San Juan, Mendoza, and Chubut in Argentina; from the vicinity of Lake Titicaca in Bolivia; and from La Ternera and Quilacoya in Chile. The Permian coals also are anthracites. However, numerous faults and folds, a high ash content, and the limited extent of the coal-bearing basins make these Paleozoic coals of little economic interest. The same is true of the Mesozoic coals that are known from Argentina in the provinces of San Juan, Mendoza, and Neuquén.
The only important and commercial coal deposits from this three-country region are Tertiary coals in Argentina and Chile. In Chile the proved and probable bituminous coal resources total about 100 million metric tons, most of which is in the Eocene Arauco basin, which contains the best-quality coal in Chile. The calorific value of the best of this coal is 13,500 Btu/lb. The Oligocene subbituminous coals of the Magallanes basin in Chile are considered to be one of the largest reserves in South America — calculated to be 5,400 million metric tons. This is in addition to the 380 million metric tons of reserve in the Argentine Río Turbio coal deposits. The Magallanes and Río Turbio coals have a high ash content and a calorific value of 8,500 Btu/lb.