Geología de la región de Salamanca, Guanajuato, México

A detailed geological mapping of the Salamanca-Aldama region, Guanajuato, Mexico, reveals the complex stratigraphy and tectonic history of the area. The study identified sixteen mappable units, with the oldest exposed unit being a polymictic conglomerate correlated to the Rojo de Guanajuato Formation. Overlying this are andesites and rhyolitic domes and lavas, part of the Oligocene volcanism in the Mesa Central region, though topaz-bearing rocks were not found within the studied area. Three ignimbrite units from the late Oligocene to early Miocene, with intercalated andesites, were also mapped, covering much of the region. The study further identified two andesite-basalt units, one associated with the La Ordeña caldera and another forming widespread lava plateaus. Monogenetic volcanic apparatuses and lava flows were linked to the Trans-Mexican Volcanic Belt (FVTM). Tectonic structures include older NW-SE faults in the northeast that affect Oligocene rhyolitic rocks, NE-ENE trending faults cutting through ignimbrites, and the significant El Bajío fault, which has a NW-SE strike, ~500 m displacement, and formed the El Bajío tectonic depression—a key boundary between the FVTM and Mesa Central. Additional N-S normal faults in the south affect Pliocene-Quaternary rocks of the FVTM.

Nieto Samaniego, Á. F. (2012). Geología de la región de Salamanca, Guanajuato, México. Boletín de La Sociedad Geológica Mexicana, 64(3), 411–425. https://doi.org/10.18268/bsgm2012v64n3a10