Coal deposits in the state of Sonora are distributed mainly in two regions. One is the Cabullona region, in the northeast, where the coal is contained in the Cintura Formation of Early Cretaceous age; its physical and chemical characteristics place it in the hypo-bituminous rank. The other region is in La Barranca, east-central Sonora, where the coal is contained in the Santa Clara Formation of Triassic-Jurassic age; there the coal ranks as anthracite. This region has been divided into the San Marcial, San Javier, Santa Clara, and San Enrique areas.
The Cabullona region is currently in the regional exploration stage, whereas in the La Barranca region, although there has been previous exploitation, exploration has not been completed. Therefore, the coal potential of Sonora has not yet been fully determined.