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.

Abstract Most of the hydrocarbon reserves in the Cuyo basin are contained in 15 oil fields that are mainly structurally controlled. They include several pools in the 40 million m3 range. Tectonic analysis based on seismic data tied to well control suggests that most closures relate to folds and reverse faults that are genetically associated with an earlier extensional fault system that developed during the early Mesozoic collapse of a late Paleozoic orogenic belt. Reconstruction of the source rock (Middle Triassic Cacheuta Formation) and reservoir paleogeography (Triassic-Tertiary Potrerillos, Rio Blanco, Barrancas, and Papagayos formations) indicates that synsedimentary extension and differential subsidence were key factors that induced an irregular distribution of organic-rich strata and porosity development. Cenozoic contraction linked to Andean orogenesis inverted the Triassic half-grabens and created structural closures. This resulted in local reservoir enhancement and access to effective charge after late Cenozoic regional migration. Prospective closures consist of elongate, irregularly spaced to en echelon anticlines and plunging noses. Axial surfaces display eastward or westward vergence, and shallow folds are replaced at depth by faulted structures (e.g., Tupungato, Barrancas, La Ventana, and Río Tunuyán fields). The roots of the structural highs involve Stratigraphie depocenters and high-angle faults that show normal separation at depth and reverse separation at intermediate levels (e.g., Vizcacheras field). The amount of inversion decreases from west to east, and in the most deformed areas, the cores of the folds were penetrated by faulting and popped up structures shaped as bivergent thrust wedges bounded by master faults and converging back-thrusts.

Abstract Middle to Late Triassic turbidite sequences are exposed in the states of Zacatecas and San Luís Potosí in central Mexico. These strata, assigned mostly to the Zacatecas Formation, accumulated in continental slope, toe-of-slope, and basin-plain environments along the passive continental margin of western Pangea. Strata of the Zacatecas Formation are age equivalent to rocks of the Antimonio Formation and Barranca Group in Sonora, the La Boca Formation in Tamaulipas and Nuevo León, and unnamed strata in Baja California. Based on their age, the Zacatecas turbidites correlate with a drop in sea level during the Permian-Triassic assembly of Pangea. The Triassic paleogeographic setting of Mexico is complex and poorly understood, because only dispersed Triassic outcrops exist across Mexico. However, the biogeographic affinities of the faunas from the Zacatecas Formation in central Mexico with those from equivalent strata in Baja California and Sonora suggest that these three regions were connected through the eastern Pacific, and that the Atlantic Ocean did not exist during the Ladinian-Carnian. The Zacatecas sequences underwent three periods of compressive deformation: one during their obduction onto the continental margin at some time during the latest Triassic-earliest Jurassic (?); a second during the Middle to Late Jurassic (Oxfordian) (?), apparently related to transpression; and a third during the Late Cretaceous to Tertiary Laramide orogeny.