Geology of the southern Mesa Central of Mexico: recording the beginning of a polymodal fault system

Abstract

The Mesa Central (MC) of Mexico presents a noticeable feature as is the three-dimensional (3D) deformation of Cenozoic volcanic rocks. To figure out when this unusual deformation began, we constructed a geological map at 1:100,000 scale, with detailed stratigraphy, and thirteen new U-Pb ages in the southern MC. The mapped area is dominated by silicic volcanic rocks with ages from ca. 34.4 Ma to ca. 23.5 Ma affected by coeval normal faulting. An angular unconformity evidences a shift in the deformation style that occurred around 30 Ma, from an NW-trending fault system in domino-style to a polymodal fault system, which also temporally coincided with the emplacement of lava dome complexes. The structural and stratigraphic data give new insight for understanding how the polymodal fault system developed in the southern MC, suggesting that the change in the deformation and volcanism regime played an important role.

Development of a Brittle Triaxial Deformation Zone in the Upper Crust: The Case of the Southern Mesa Central of Mexico

“…Tectonics DEL PILAR-MARTÍNEZ ET AL. Del Pilar-Martínez et al, 2020;Labarthe-Hernández et al, 1982;Nieto-Samaniego et al, 2016;Suárez-Arias, 2019;Xu et al, 2004) indicates that it was diachronous, being slightly older in the south with respect to the north (Figure 9a).…”

“…Stratigraphical references: (1) Del Pilar‐Martínez et al (2020), (2) Echegoyén‐Sánchez et al (1970), (3) Labarthe‐Hernández et al (1982), (4) Quintero‐Legorreta (1992), and (5) Botero‐Santa et al (2015). Geochronological references: [1] Del Pilar‐Martínez et al (2020), [2] Nieto‐Samaniego et al (2016), [3] Nieto‐Samaniego et al (1996), [4] Botero‐Santa et al (2015), and [5] this study. The age from sample J2 was recalculated using the isotopic data from Manzano‐López (2011).…”

“…The intrusive rocks comprise minor outcrops of gabbroic (Arperos Gabbro in Martínez‐Reyes, 1992) and quartzmonzodioritic composition (Duraznillo Intrusive in Del Pilar‐Martínez et al, 2020), exposed at adjacent areas of the southern Villa de Reyes Graben (Figure 2). The intrusive contact of the Duraznillo Intrusive has not been observed in the field, but it is discordantly overlain by the Chichíndaro Rhyolite.…”

“…The Panalillo Ignimbrite is a thin pyroclastic deposit dated at 28 Ma, which distributes in the top of the ignimbrite plateaus and fills grabens (Figure 2) (Del Pilar‐Martínez et al, 2020). From two samples, collected inside the Villa de Reyes Graben (SF‐89) and the Santo Domingo Graben (SF‐32), the ages (U‐Pb in zircon) of 28.83 ± 0.21 Ma and 28.39 ± 0.21 Ma were obtained, respectively (Table 1 and Figure 3).…”

“…These deposits have a major volcanic component coming from the adjacent shoulders of the grabens. Del Pilar‐Martínez et al (2020) assigned a maximum depositional age of ~16.5 Ma (U‐Pb in detrital zircons) for these deposits.…”