31 The western equatorial Pangea: Geological, geophysical, geochronological, and paleoecological insights on the youngest supercontinent assembly and breakup on Earth (Part 1)

This session welcomes studies in Mexico, southwestern North America, and northwestern South America investigating the Pangea’s supercontinent cycle from tectonic, stratigraphic, paleoecologic, geophysical, geochronologic, and paleogeographic perspectives to offer insights into its assembly and breakup.

Friday, 24 April 2026
8:00 AM - 12:00 PM
LMH, Isla Carmen

Sedimentological and provenance insights from the upper Patlanoaya Group, southern Mexico: A Late Paleozoic record of peri-Gondwanan blocks interaction during Pangea assembly

Paper number: 31-8
Program: Technical Sessions
Time: 10:30 AM – 10:50 AM

Authors

Abstract

The assembly of Pangea represents the most significant global tectonic event of the late Paleozoic and resulted from diachronous convergence between Laurentia–Baltica and Gondwana, accompanied by the progressive closure of the Rheic Ocean from the Early Carboniferous to the Permian time. This process led to the development of an extensive orogenic system, including the Variscan, Alleghanian, and Ouachita–Marathon–Sonora belts, and involved the accretion of multiple tectonic blocks along continental margins. These accretionary processes generated regional suture zones that record major displacements and exerted a strong control on topography and sedimentation. In southern Mexico, such sutures mark the tectonic boundaries between peri-Gondwanan blocks located along the Gondwana–Laurentia collisional zone during the late Paleozoic. The Caltepec Fault Zone, which juxtaposes the Acatlán and Oaxacan complexes, represents a key remnant of this tectonic framework. However, its limited exposure has hindered a comprehensive understanding of the timing and regional implications of block collision and accretion.

The Upper Paleozoic Acatlán Complex preserves a crucial stratigraphic record of these processes. Within it, the late Paleozoic Patlanoaya Group is the only non-metamorphosed and weakly deformed unit, making it one of the most complete and best-preserved Paleozoic clastic successions in Mexico. This succession has been previously studied by several authors due to its paleontological content, leading to numerous paleoenvironmental and paleogeographic reconstructions based solely on marine fossil evidence. Nevertheless, these proposed scenarios underestimate the presence of major tectonic events in southern Mexico associated with the assembly of Pangea. Despite its tectonic meaning, detailed sedimentological and provenance data remain limited.

In this work, we present new sedimentological, petrographic, geochronological, and paleontological data from the upper Patlanoaya Group, obtained within the framework of the PAPIIT-IA103125 and IN107924 projects. Our sedimentological results allow a redefinition of depositional environments and document a transition from shallow- to deep-marine settings. Provenance, geochronological, and paleontological data suggest a Late Pennsylvanian sediment supply from the Oaxaca and Acatlán complexes, documenting that the tectonic proximity between the peri-Gondwanan blocks to which they belonged occurred earlier than suggested by existing models. This study highlights the importance of late Paleozoic successions for reconstructing the evolution of Pangea’s assembly in Mexico.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3

doi: 10.1130/abs/2026CD-410837

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