Evolución del relieve en las fallas San Marcos, El Madroño y Las Vigas, norte de la junta triple del bloque Jalisco, México

Abstract

The landscape evolution of the region of the triple junction of the Jalisco Block is the result of Pliocene and Quaternary tectonic and volcanic processes which have produced the formation of tectonic depressions now occupied by lakes. The age of faults for this zone is not known in detail. The use of morphometric indexes. proved to be useful to detect the tectonic activity in young landscapes settings, however, few studies have used such approach to constrain the landscape evolution for west-central Mexico. In this study we analize the stream long profiles of rivers incising across the strike of the faults of San Marcos, Las Vigas and El Madroño, which are located north of the triple junction of the Jalisco Block. The morphometry of alluvial fans at the base of the fault scarps is also analyzed. The knickpoint recession age is estimated as well as the analysis of rocks (n = 6) to characterize the chemical composition of different volcanic units. The age of the zircons of the ryolithic dome of La Coronilla, which was formed over of the Madroño fault, is of 0.66 ± 0.06 ka, this allows to constrain a minimum faulting age. The results obtained here indicate that the ksn and kl indexes are the best capturing the topography resulting from the thrust produced by faults. The time when the knickpoints started to migrate occurred between 0.7 and 1 Ma. The Pliocene volcanism is calc-alcaline and the composition of lavas is between basaltic-andesite to andesite. This volcanism is different to those related to faulting which tends to be more acid (dacites and rhyolites). The agreement in age of knickpoint recession, alluvial fans and Pleistocene volcanism indicates that the landscape and the erosion at the north of the triple junction of the Jalisco Block had and important activity in the Quaternary.

Respuesta del sistema erosivo fluvial en las cuencas Ameca y Santiago, centro-occidente de México, ante el control tectónico y volcánico

“…La actividad volcánica de la FVTM bloqueo drenajes prexistentes situados en las porciones orientales de la cuenca Ameca, los productos volcánicos corresponden a andesitas y basaltos de ~4 a 1 Ma concentrados al occidente del lago de Chapala (Ferrari et al, 2000). El volcanismo, además de interrumpir el aporte de materiales provenientes de la SMO hacia el área de Zacoalco, habría truncado el aporte proveniente del centro de México y generado el represamiento que actualmente corresponde al lago de Chapala (Castillo et al, 2019;Figura 11b), este represamiento y su orientación también estaría favorecido por el Graben de Chapala (RCh) (Figura 2). Posteriormente el lago de Chapala comenzaría a verter su carga al río Santiago, y con ello se conformó la nueva vía de descarga de los ríos provenientes del centro de México (Figura 11b).…”