204 Paleozoic Tectonics of SW Laurentia Without Borders: Final Amalgamation of Pangea in the USA, Mexico, and South America
We invite contributions that explore the Paleozoic tectonic evolution of southwestern Laurentia during the final assembly of western Pangea. Research on Paleozoic tectonic belts in Gondwana, particularly from Mexico and South America, is especially welcome.
Tuesday, 21 October 2025
1:30 PM - 5:30 PM
HBGCC, 217B
Detrital zircon provenance records of the late Paleozoic Pedregosa Basin in Chihuahua, Mexico, and implications for the final assembly of Pangea
Paper number: 204-10
Program: Technical Sessions
Time: 4:00 PM – 4:15 PM
Authors
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Sandra Juárez-Zúñiga Presenting AuthorJackson School of Geosciences, The University of Texas at Austin, Austin, Texas
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Daniel StockliJackson School of Geosciences, The University of Texas at Austin, Austin, Texas
Abstract
The Pedregosa Basin in northern Mexico is a late Paleozoic basin in the Ouachita-Marathon-Sonora (OMS) foreland that spatially and temporally overlapped with both regional intraplate deformation and final collisional assembly of Pangea. The Sierra del Cuervo and Sierra El Pajarito in Chihuahua, northern Mexico, expose upper Paleozoic deep-water synorogenic strata of the Pedregosa Basin, representing both proximal and distal OMS foreland deposits, respectively. The Sierra del Cuervo exposes a highly deformed sequence of turbidites of the Rara Fm. that are structurally juxtaposed against Grenville-aged basement rocks. The foothills of Sierra El Pajarito preserve gently folded, carbonate-rich turbidite strata of the La Vinata Flysch. In this study, we present new detrital zircon (DZ) U–Pb data from the Rara Fm. and La Vinata Flysch to investigate the sediment provenance of the Pedregosa Basin and potential contributions from Laurentian and Gondwanan sources, as well as the timing of continental collision along this segment of the OMS belt. The Rara Fm. shows dominant Neoproterozoic–Cambrian (950–490 Ma), Grenville (1300–950 Ma), and Paleozoic (490–280 Ma) age modes, with subordinate age groups older than 1.3 Ga. In contrast, the La Vinata Flysch exhibits lower proportions of Grenville and Neoproterozoic–Cambrian ages, but higher proportions of 1800–1600 Ma and 1500–1300 Ma age modes. Rim-core age relations in the Rara Fm. reveal diagnostic Peri-Gondwanan signatures that are absent in the La Vinata Flysch. The youngest single-grain ages from both units indicate Wolfcampian maximum depositional ages (ca. 284–290 Ma). These results suggest that the proximal Rara Fm. was likely sourced from accreted Peri-Gondwanan terranes during the early Permian, with no evident Laurentian input. In contrast, the more distal Vinata Flysch appears to reflect a mixed provenance, with contributions from both Peri-Gondwanan terranes and Laurentian sources, as evidenced by Grenville, Granite–Rhyolite, Yavapai–Mazatzal, and older cratonic components, likely derived from exposed basement remnants or recycled older sedimentary units. The relative scarcity of typical Laurentian basement ages, however, suggests that these turbidites postdate late Paleozoic intracontinental basement-involved shortening in Laurentia and instead record foredeep sedimentation within the Pedregosa Basin during progressive OMS continental collision and final assembly of Pangea in the early Permian.
Geological Society of America Abstracts with Programs. Vol. 57, No. 6
doi: 10.1130/abs/2025AM-413701
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