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Geochronological analysis as a test of the presence of the Sonora allochthon in the Sierra Las Pintas, Baja California, Mexico

Pringle, Claire Kathleen (2021) Geochronological analysis as a test of the presence of the Sonora allochthon in the Sierra Las Pintas, Baja California, Mexico. Masters thesis, Northern Arizona University.

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Formation of the final supercontinent, Pangea, culminated in late Paleozoic time with closing of the Rheic ocean and collision of Gondwana and Laurentia. This resulted in the hypothesized 3,000-km-long Ouachita-Marathon-Sonora orogenic belt (OMS) along the southern margin of Laurentia. The Sonora allochthon, the westernmost segment of the OMS, is dominantly located in Chihuahua and Sonora, Mexico, but recent studies have suggested that the orogen continues into northern Baja California, where sedimentary rocks in the Sierra Las Pintas have been correlated to allochthon stratigraphy in Sonora. This study provides the first detrital zircon geochronological analysis of the Sierra Las Pintas to test the hypothesis that Sonora allochthon strata are present and further correlation can be made to the Sonora allochthon documented in central Sonora. Detrital zircon geochronology of the Sierra Las Pintas strata indicates major sources from the Peninsular Ranges batholith and the Permo-Triassic arc, as well as minor sources from Gondwana, the Grenville orogen, Granite-Rhyolite provinces, Yavapai-Mazatzal provinces and the Archean craton. Provenance analysis suggests that most of the detritus was derived from the Peninsular Ranges batholith to the west, the Cordilleran Permo-Triassic arc to the northeast, crustal provinces of the Laurentian craton to the north, and Gondwana to the south. A Late Cretaceous maximum depositional age is determined for Sierra Las Pintas strata and stratigraphic analysis indicates deposition in the Peninsular Ranges batholith forearc along the continental slope and ocean basin. Geochronologic analyses suggest that the Sonora allochthon is not present in the Sierra Las Pintas and the succession cannot be correlated to the Sonora allochthon in central Sonora. Provenance interpretation of strata in the Sonora allochthon of central Sonora agrees with previous literature and provides strong detrital zircon evidence of Gondwanan source, which has rarely been identified in previous studies. Although the results of this study do not support the hypothesis that the Sonora allochthon is present in the Sierra Las Pintas, the strata record a mixed provenance of Gondwanan and Laurentian source regions, as well as Cretaceous Cordilleran arc activity.

Item Type: Thesis (Masters)
Publisher’s Statement: © Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords: Detrital zircon geochronology; Peninsular Ranges batholith; Permo-Triassic arc; Sierra Las Pintas; Sonora allochthon; Tectonics; Baja California; Sierra Las Pintas
Subjects: Q Science > QE Geology
NAU Depositing Author Academic Status: Student
Department/Unit: Graduate College > Theses and Dissertations
College of the Environment, Forestry, and Natural Sciences > School of Earth Sciences and Environmental Sustainability
Date Deposited: 04 Feb 2022 21:01
Last Modified: 28 Dec 2022 08:30
URI: https://openknowledge.nau.edu/id/eprint/5653

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