Tectono-stratigraphic basin evolution in the Tehuacán-Mixteca highlands, south western México

Abstract

The morphological evolution of the basins in the Sierra Madre del Sur (SMS), southern M exico is poorly understood. This work explains for the first time the geomorphological development of the tectonic, fluviallyinterconnected SMS basins named San Juan Raya (SJRb) and Zapotitl an (ZAPb). The evolution of the SJRb and ZAPb are analysed within the context of the transformations of the well-studied Tehuac an basin (TEHb). A new interpretation of a series of tectonic features of the TEHb valley area is also presented. Published geological data and extensive field work provided the basis for our geomorphological and evolutionary interpretation of basin evolution of this part of Mesoamerica during the late Cenozoic. Stratigraphic and sedimentary records suggest that after the late Cretaceous-early Cenozoic orogeny the TEHb and ZAPb were closed basins, and that the TEHb graben system was activated during the Paleogene as a response to the dominant regional NW-SE trending faults. We propose that the ZAPb and SJRb formed sequentially during the Neogene as a result of new E-W, N-S and NE-SW faults. The continuation of the TEHb extension during the Oligocene widened its lowland area and allowed the formation of an extensive lake. No alluvial or fluvial records of this interval are found in the ZAPb and SJRb. No sedimentation rather than formation and subsequent erosion of such sediments is supported by the basin morphology and by the absence of re-worked alluvial deposits at the outlet area where both connect to the TEHb. By middle to late Miocene the TEHb lost its endorheic configuration, ending the lake-type deposition while new faults initiated the opening of the ZAPb. Intensive tectonics, alluvial deposition and the confinement of the Tehuac an lake to the north sector of this basin characterised the Pliocene. During the late Pliocene to the early Pleistocene the formation of the SJRb was initiated. Quaternary faulting related to basin extension along the north watershed of the SJRb and ZAPb is supported by independent data on the biogeography of the cactus Mammillaria pectinifera. We introduce the idea that the departure from the regional NW-SE fault alignment that formed the major Miocene basins to a more local E-W trend that formed Neogene-Quaternary basins was probably a response to the latest post-orogenic relaxation of the crust in the Mixteca terrane.

Mitochondrial DNA sequences and nuclear microsatellites reveal population genetic structure of the range-restricted hummingbirdPhaeoptila sordidain the Balsas Basin

“…Dusky Hummingbird occupies arid montane scrub, seasonally dry tropical deciduous forest and open-to-semiopen areas with scattered trees (gallery forests) from 900 to 2,200 m above sea level (Hutto 1992, Howell and Webb 1995; Figure 1). The current geographic distribution of P. sordida clearly matches the regional rain shadows (the Balsas river basin and the Tehuacán-Cuicatlán Valley and Valles Centrales) associated with the Miocene aridification (Ramírez-Arriaga et al 2014, Medina-Sánchez et al 2020). The divergence time estimated (11.2–7.6 Myr) for the split between P. sordida and the remaining lineages in the emeralds subclade (Hernández-Baños et al 2020) is consistent with the Late Miocene average age of Bursera species and its strong conservatism to SDTDF (Becerra 2005, De-Nova et al 2012).…”

“…These valleys are arid and hot, with a dry–cold climate and a mean annual precipitation of 500–800 mm and an annual average temperature of 18–22°C° (García-Mendoza et al 2004), and are especially rich in endemic plant species with very restricted distributions (Dávila et al 1993, García-Mendoza et al 2004, Sosa and deNova 2012, Ornelas et al 2018, Aguirre-Planter et al 2020). The Río Balsas Depression, Tehuacán-Cuicatlán Valley, and the Valles Centrales are located in the Mexican morphotectonic province of Sierra Madre del Sur, and together form one of the most geologically complicated regions of Mexico (Ferrusquía-Villafranca 1993, Medina-Sánchez et al 2020).…”

Evaluating the monophyly of Mammillaria series Supertextae (Cactaceae)

“…In some geographic regions, the M. ser. Supertextae species have undergone tectonic, erosive, alluvial and volcanic changes for millions of years; during the Pleistocene, these processes continued, giving rise to the current geomorphology (Siebert and Carrasco-Núñez 2002;Medina-Sánchez et al 2020). Paleontological and molecular evidence suggests that glacial climate cycles that occurred during the last 2.5 Mya affected the distribution, diversity, and genetic structure of plant and animal populations (Gámez et al 2014;Scheinvar et al 2016;Cornejo-Romero et al 2017).…”

Distribución de la cobertura vegetal y del uso del terreno del municipio de Zapotitlán, Puebla, México

“…Este bajo porcentaje que cubre la superficie agrícola está relacionado con la dominancia de un relieve conspicuo, que restringe la posibilidad de ampliar las fronteras agrícolas (Muñoz et al, 2007). Por otra parte, 10.1% del territorio no presenta cobertura vegetal, evidenciando procesos de degradación antrópica en la porción sureste, debido al aprovechamiento de los suelos arcillosos para la producción de cerámica y a las actividades agrícolas (Arias-Toledo et al, 2000); mientras que en las zonas altas, localizadas en la porción norte, se presentan rasgos de degradación natural, ocasionados por la ocurrencia de procesos erosivos y movimientos en masa (Medina- Sánchez et al, 2020;Muñoz et al, 2007). El patrón de distribución de la CV identificado para el municipio a una escala de 1:50,000, coincide de manera general con el de Pérez-Valladares et al (2019), elaborado a una escala 1:250,000, en las clases de vegetación identificadas y en el gradiente altitudinal en el que se localizan.…”

“…Numerosos estudios se han llevado a cabo en el valle de Tehuacán-Cuicatlán desde diversas áreas del conocimiento, muchos de ellos de índole biológico (Casas et al, 2014(Casas et al, , 2016Dávila et al, 2002;McAuliffe et al, 2001;MacNeish, 1992;Medina-Sánchez, et al, 2020;Muñoz et al, 2008;Valiente-Banuet et al, 2009;Vázquez, 2019). Este estudio ha permitido avanzar hacia el objetivo prioritario de identificar espacialmente la distribución de la cobertura vegetal y las actividades de origen humano del municipio de Zapotitlán, hasta un tercer nivel de agregación (tabla 1), integrando la composición de especies (apéndice), en un mapa digital conformado por 17 categorías de cobertura vegetal y uso del terreno (CVUT) en escala 1:50,000 (fig.…”