37 Cordilleran Margin Evolution and Supercontinent Tectonics: From Pangea Assembly to North American Orogenesis (Posters)

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.

Friday, 24 April 2026
8:00 AM - 5:30 PM
LMH, 5th Floor Chapel

Revisiting the forearc triad of the Cedros Island, BC, Mexico

Paper number: 37-0
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The ophiolite and mélange-related rocks of Cedros Island (BC) have been recognized as vital components of a subduction complex for several decades, following the foundational work of Kilmer in the 1970s, followed research during the 1980s and early 2000s focused on characterizing the petrology and geochronology of the mélange and upper-plate ophiolite, while also untangling the significance of the sedimentary cover—specifically the arc-related volcano-sedimentary units and the Late Cretaceous forearc deposits that postdate the mélange.

After nearly twenty years, we have revisited the island to conduct an integrated structural, petrographic, geochemical, and geochronological study of these units. To address the structural complexity of Cedros Island and provide a framework for detailed research, we reinforcement a new 1:100,000 scale geological map, which significantly improves the resolution of previous mapping efforts.

Beyond the map, we present preliminary results from various analytical studies designed to complement and reevaluate existing datasets and refine the evolutionary model of the study area. Within the mélange, new data provide tighter constraints on the grade and timing of metamorphism of exotic blocks. In the ultramafic and mafic ophiolitic rocks, we provide petrographic and geochemical evidence to further constrain their petrogenesis. In the sedimentary cover, we present new petrographic data and U-Pb detrital zircon ages from strategic stratigraphic levels, in order to compare with new ages obtained from metasedimentary units involved in the mélange.

Collectively, these preliminary data are intended to foster in-depth discussion, facilitating a broader comparison with subduction complexes, upper-plate ophiolites, and forearc sedimentary covers exposed specially along the western North American Cordillera.

 

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

doi: 10.1130/abs/2026CD-410935

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