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
The Permian Tuzancoa Formation, central-eastern Mexico: Provenance and tectono-magmatic implications for the final assembly of Pangea
Paper number: 31-9
Program: Technical Sessions
Time: 10:50 AM – 11:10 AM
Authors
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Juan Casas-Peña Presenting AuthorInstituto de Geología, Universidad Nacional Autónoma de México, Mexico city, Mexico
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Michelangelo MartiniInstituto de Geología, Universidad Nacional Autónoma de México, Mexico city, Mexico
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Pilar Navas-ParejoEstación Regional del Noroeste, Instituto de Geología, Universidad Nacional Autónoma de México, Hermosillo, Sonora
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Juan Valencia-GómezPosgrado en Ciencias de la Tierra, Instituto de Geología, Universidad Nacional Autónoma de México, Mexico city, Mexico
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Mildred Zepeda-MartínezInstituto de Geociencias, Universidad Nacional Autónoma de México, Querétaro, Querétaro
Abstract
Pangea was assembled during the late Paleozoic due to the diachronous, zipper-like closure of the Rheic Ocean, resulting in the collision between of Laurentia, Gondwana (including all the peri-Gondwanan terranes) and Baltica. This progressive continental collision developed a major trans-continental tectonic suture, which is presently represented by late Paleozoic orogenic belts in Europe and North Africa (Variscan belt), eastern and southern of United States, and northern of Mexico (Alleghanian-Ouachita-Marathon-Sonora orogenic belts). The continental collision also produced consumption of the Rheic Ocean, which separated Gondwana from Laurentia and Baltica. Available data indicate that the intervening oceanic plate was subducted beneath Gondwana, producing a Carboniferous-early Permian arc that is widely exposed in Mexico. The Gondwana arc is represented by large plutons and a few volcano-sedimentary successions.
The early Permian Tuzancoa Formation of central-eastern Mexico is one of the most iconic exposures of the Gondwana arc and is probably its best-preserved surficial expression. The lower part of the Tuzancoa Formation is composed of volcaniclastic turbidites interbedded with mafic to intermediate lava flows, as well as scarce calciclastic turbidites, calcareous debris-flow deposits, and shallow-marine calcareous olistostromes with early Permian fusulinids. Syn-sedimentary faults showing normal displacement occur ubiquitously in these deposits, indicating the extensional nature of the arc. Toward the top of the unit, this succession grades transitionally into a different volcano-sedimentary succession composed of fluvial volcaniclastic deposits with fossil plants interbedded with felsic rocks.
In this study, we present the first U-Pb zircon dates obtained from the Tuzancoa Formation. Our data indicate that the mafic-intermediate submarine stage of the arc is bracketed between ~290 and 285 Ma, whereas the felsic subaerial stage is more restricted (~275 Ma). The change from the mafic-intermediate submarine arc to a felsic subaerial arc match with the age of the final collision between Gondwana and Laurentia and, thus, we explore the possibility that it represents the evolution from an extensional arc formed during subduction of the Rheic Ocean to a compressive arc associated with continental collision. According to this scenario, the Tuzancoa Formation would record the final assembly of Pangea and closure of the Rheic Ocean.
Geological Society of America Abstracts with Programs. Vol. 58, No. 3
doi: 10.1130/abs/2026CD-410772
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