14 Lost Oceans, Shifting Continents: Interdisciplinary Records of Paleo-Pacific Plate Histories in the American Cordilleras

This session integrates tectonics, petrology, geochronology, stratigraphy, and paleontology to illuminate how Paleo-Pacific plates drove subduction dynamics, crustal evolution, and paleogeographic reconstructions across the complex geological architecture of the American Cordilleras.

Wednesday, 22 April 2026
1:30 PM - 4:00 PM
LMH, Meeting Room

Detrital zircon U-Pb CA-ID-TIMS constraints on deposition of the Cerro Rajon Formation (Sonora, Mexico) and identification of a potential local source of volcanism

Paper number: 14-2
Program: Technical Sessions
Time: 2:10 PM – 2:30 PM

Authors

Abstract

The Terreneuvian Cerro Rajón Formation represents a significant volcanic event along the southwestern margin of Laurentia. Petrological analyses associate this volcanism with rift-related activity in continental and shallow marine settings. Constraining the age of this volcanism aids its correlation with other western magmatic events linked to the opening of the Paleo-Pacific Ocean and refining paleogeographic reconstructions of western Laurentia. LA-ICP-MS U-Pb ages of zircons from eight samples (n=3200 grains) spanning the unit fall into five recurrent age peaks: Neoarchean (2693 ± 35 Ma), Paleoproterozoic (1770 ± 12 Ma to 1751 ± 37 Ma), early Mesoproterozoic (1407 ± 15 Ma to 1438 ± 10 Ma), late Mesoproterozoic (1098 ± 36 Ma), and Ediacaran-Cambrian (561 ± 25 Ma). The dominant age populations correspond to the Yavapai, Mazatzal, and Grenville tectonostratigraphic provinces, while the less frequent Neoarchean grains likely derived from distant sources such as Grouse Creek or Wyoming. Scarce younger zircon populations may indicate local sources related to early Cambrian volcanism in Sonora and other rift-associated events in southwestern Laurentia. Four samples containing young zircons were further analyzed using CA-ID-TIMS U-Pb geochronology, yielding ages between 520.2 ± 2.4 Ma and 529.9 ± 4.3 Ma; these ages span most of Terreneuvian Stage 2. These ages are consistent with biostratigraphic and chemostratigraphic data from the succession, implying that they represent the timing of Cerro Rajón volcanism. Collectively, these findings document younger volcanic episodes associated with Ediacaran-Cambrian rifting along western Laurentia, occurring more than 200 million years after the initial breakup of Rodinia.

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

doi: 10.1130/abs/2026CD-411063

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