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Joint 70th Rocky Mountain Annual Section / 114th Cordilleran Annual Section Meeting - 2018

Paper No. 52-1
Presentation Time: 3:35 PM

CONTINUOUS PALEOZOIC STRATIGRAPHIC AND STRUCTURAL TRENDS ACROSS SONORA INDICATE NO MAJOR OFFSET BY STRIKE-SLIP FAULTS IN NORTHWEST MEXICO


POOLE, Forrest G.1, SANDBERG, Charles A.1 and AMAYA-MARTÍNEZ, Ricardo2, (1)U.S. Geological Survey, Denver, CO 80225, (2)Geología, Universidad de Sonora, Hermosillo, 83000, Mexico

Continuous east-west trends of Paleozoic stratigraphic and structural units within the cratonic-platform, continental-shelf, and ocean-basin provinces in Sonora, negate the postulation of major strike-slip faulting, such as the hypothetical Mojave-Sonora megashear and other postulated large-scale lateral faults. The provinces in northern Mexico are continuous with those in the southern United States.

Three decades of mapping and studying Ordovician to Permian lithofacies and biofacies in Sonora reveal continuous stratigraphic and structural trends across Sonora, and into northern Baja California. These trends are a continuation of correlative strata of the cratonic-platform, continental-shelf, and Ouachita-Marathon orogenic belt of southern Laurentia.

The following constitute our studied areas. Cratonic-platform localities include Mina La Herradura and Bacoachi in northern Sonora. Continental-shelf localities include Rancho El Bísani in northwestern Sonora; Rancho Placeritos and Cerro El Carnero in west-central Sonora; Hermosillo city, Sierra Santa Teresa, Rancho Las Norias, Sobechi, Sierra Agua Verde, Cerro Cobachi, Sierra Martínez in central Sonora; and Cerro Santo Domingo and Arivechi in east-central Sonora. Ocean-basin localities include Isla Turners in the Gulf of California; La Colorada, Minas de Barita, Cerro Cobachi, and Rebeiquito in central Sonora; and Rancho San Marcos, Soyopa, Sierra El Aliso in east-central Sonora. Ordovician to Pennsylvanian ocean-basin strata are confined to the west-trending Sonora allochthon, which is the western extension of the Ouachita-Marathon orogenic belt of the southern U.S. and northern Mexico. Our studies include the west-trending foredeep-fill deposits of the Permian Mina México Formation.

Our studies demonstrate the impossibility of the postulated early Late Jurassic Mojave-Sonora megashear (MSM), which assumes a 600-1,100 km left-lateral offset of Precambrian to Middle Jurassic rocks to Sonora from California. Also, we find no evidence of large late Paleozoic left-lateral faults. If the MSM does exist, offset occurred before deposition of Phanerozoic rocks and displaced only Precambrian terranes.

Handouts
  • GSA Flagstaff talk Paleozoic copy.ppt (6.6 MB)
  • Flagstaff Pzc talk corrected.doc (549.5 kB)

    • Session No. 52

    T20. Biostratigraphy and Paleoenvironments of Western North America: Correlations across the International Border
    Wednesday, 16 May 2018: 3:30 PM-5:15 PM
    Canyon Room (DoubleTree by Hilton)
    Geological Society of America Abstracts with Programs. Vol. 50, No. 5
    doi: 10.1130/abs/2018RM-314044
    © Copyright 2018 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.
    Back to: T20. Biostratigraphy and Paleoenvironments of Western North America: Correlations across the International Border
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