Paleomagnetic Study of the Late Miocene Volcanic Sequence in Sonora, Mexico: Clockwise Vertical Axis Rotation Related to the Oblique Rifting in the Pacific-North American Plate Boundary

L. A. Velderrain-Rojas, J. R. Vidal-Solano*, L. M. Alva-Valdivia

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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The evolution of oblique divergence along the Pacific-North American plate boundary during the late Miocene is well-preserved along the eastern margin of the Gulf of California. The early phase of this deformation occurred between ∼12.5 and ∼6 Ma in Sonora, NW Mexico, related to oblique rifting of the Gulf of California. The magmatic sequence for this period is exposed in the Cerro El Vigía, Guaymas region. This sequence is characterized by intrusive rocks, lava flows, and pyroclastic flows ranging in age from 12 to 10 Ma. The Cerro El Vigia has a predominant semicircular geomorphology traditionally ascribed to a volcanic caldera structure, such as large ring faults. Rock magnetic analyses of these magmatic products identify the magnetic minerals and their reliability for tectonic interpretations. The mean paleomagnetic direction from 14 sites from the Cerro El Vigia reveals up to 90° clockwise rotation about an inclined axis (65–85° axis plunge) with respect to stable North America. When interpreted in the context of the semicircular structure, these observations suggest that the structure has a tectonic, not volcanic origin. Paleomagnetic results and tectonics during the late Miocene suggest that this crustal block rotation corresponds to the development of large tension gashes deformed within a dextral transtensional system associated with continental deformation of the proto-Gulf of California rift. Based on the paleomagnetic data, reported ages, and magmatic stratigraphy, we conclude that the magmatism and associated deformation at Cerro El Vigia was synchronous with transtensional tectonics between ∼11 Ma to ∼8 Ma.

Original languageEnglish
Article numbere2021TC007183
Issue number8
StatePublished - Aug 2022

Bibliographical note

Funding Information:
This work was developed as part of Velderrain‐Rojas M.S. thesis and Postdoctoral fellowship at Universidad de Sonora. This research was supported by the CONACYT Project 180784 to J. R. Vidal Solano. L. M. Alva‐Valdivia thanks the IN101521 PAPIIT‐DGAPA‐UNAM research project. We thank Martin García for their help in the field. Special thanks to M. C. Antonio González for support during paleomagnetic measurements and analysis work. We thank all staff of the BCCT‐UNAM (head, Saúl Armendariz) for their technical assistance. Finally, we thank the editor and Peter C. Lippert and E. L. Pueyo, reviewers who helped improve this document. Supporting data are included in Tables S1, S2, S3, and S4 in Supporting Information S1 .

Publisher Copyright:
© 2022. American Geophysical Union. All Rights Reserved.


  • Paleomagnetism
  • block rotation
  • oblique rift
  • proto-Gulf of California
  • transtensional tectonics


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