Fluvial deposits of the Patlanoaya Group in southern Mexico: the stratigraphic record of an Early Mississippian supradetachment basin formed along the margin of Gondwana during the closure of the Rheic Ocean

ABSTRACT

The Rheic Ocean closure stratigraphic record in southern Mexico is largely exposed in the Paleozoic Acatlán Complex. One of the most distinctive characteristics of the Acatlán Complex is the presence of high-pressure rocks, interpreted as remnants of the Rheic Ocean and the adjacent continental margin of Gondwana, which were subducted and then exhumed to the surface. Despite its importance in reconstructing the dynamics of the westernmost Rheic Ocean closure, the timing and mechanisms of exhumation of these high-pressure rocks remain debated. Some authors have tentatively interpreted the late Paleozoic, fluvial to marine succession of the Patlanoaya Group in southern Mexico as the sedimentary response to the exhumation of high-pressure rocks of the Acatlán Complex. Therefore, these sedimentary rocks may be particularly helpful in understanding the timing and evolution of high-pressure rocks exhumation during the Rheic Ocean closure. In this work, the tectono-sedimentary evolution of the continental deposits of the Patlanoaya Group was reconstructed, integrating sedimentologic, petrographic, and U-Pb detrital geochronological data to test the different scenarios proposed for the exhumation of the Acatlán Complex high-pressure rocks. Our data suggest that the lower Patlanoaya Group was deposited in an Early Mississippian basin with a two-stage evolution: a phase characterized by debris flow deposits derived from small-scale reliefs composed of low-grade metamorphic rocks and a subsequent phase marked by an NNE-trending fluvial system deposits sourced from low-metamorphic grade rocks of a mylonitic zone. Therefore, the lower Patlanoaya Group deposition was controlled by a major NNE-trending mylonitic shear zone associated with the development of a supradetachment basin linked to the progressive exhumation of high-pressure rocks during an Early Mississippian major extensional event. This work highlights the importance of sedimentary deposits in reconstructing the late Paleozoic history of the Acatlán Complex during the Rheic Ocean closure and the final stage of the Pangea assembly.

KEYWORDS:

• Rheic Ocean closure
• carboniferous
• patlanoaya group
• acatlán complex
• supradetachment basin

Acknowledgments

This research was funded by the CONAHCyT Frontier of Science grant 7351 and PAPIIT IN101520, both granted to Luigi Solari. The first author thanks DGAPA-UNAM for a postdoctoral fellowship grant at CGEO, UNAM. We thank Carlos Ortega-Obregón (Centro de Geociencias, Universidad Nacional Autónoma de México) for kindly performing the isotopic analysis; M.Sc. Irene Pérez Casillas for providing technical assistance during zircon grains separation and mount (Centro de Geociencias, UNAM); Juan Tomás Vázquez (Centro de Geociencias, UNAM) for preparing and staining whole-rock thin sections. We thank Mario Ramos-Arias for helpful discussions on the metamorphic rocks exposed in the Patlanoaya area. We are grateful to the people of the community of San Salvador Patlanoaya and the authorities of Izúcar de Matamoros and Ahuatlán, Puebla state, who kindly allowed us to conduct fieldwork in the surrounding area. We extend our most sincere thanks to Aurelio Isidoro Guerrero and his family for his invaluable support and confidence during the field work, which was essential for the success of our project. We are grateful to Majie Fan and an anonymous reviewer, whose constructive comments and suggestions greatly improved the manuscript.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the results reported in this paper.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2024.2324309

Additional information

Funding

The work was supported by the CONAHCyT (Consejo Nacional de Humanidades, Ciencias y Tecnologías) Frontier of Science grant [7351]; PAPIIT (Programa de Apoyo a Proyectos de Investigación e Inovación Tecnológica) [IN101520].