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1 This is the author s version of a work that was submitted/accepted for publication in the following source: Ferrari, Luca, Martinez-Lopez, Margarita, Orozco-Esquivel, Teresa, Bryan, Scott, Duque, Jose, & Lonsdale, Peter (2013) Late Oligocene to middle Miocene rifting and syn-extensional magmatism in the southwestern Sierra Madre occidental, : the beginning of the Gulf of California rift. In Geological Society of America Abstracts with Programs, Geological Society of America, Fresno, California. (In Press) This file was downloaded from: c Copyright 2013 Geological Society of America. c Copyright 2012 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. Notice: Changes introduced as a result of publishing processes such as copy-editing and formatting may not be reflected in this document. For a definitive version of this work, please refer to the published source:

2 Received Your abstract submission has been received Print Print this page now. You have submitted the following abstract to Cordilleran Section 109th Annual Meeting (20 22 May 2013). Receipt of this notice does not guarantee that your submission was complete, free of errors, or accepted for presentation. LATE OLIGOCENE TO MIDDLE MIOCENE RIFTING AND SYN EXTENSIONAL MAGMATISM IN THE SOUTHWESTERN SIERRA MADRE OCCIDENTAL, MEXICO: THE BEGINNING OF THE GULF OF CALIFORNIA RIFT FERRARI, Luca 1, MARTINEZ LOPEZ, Margarita 2, OROZCO ESQUIVEL, Maria Teresa 3, BRYAN, Scott 4, DUQUE, Jose 3, and LONSDALE, Peter 5, (1) Instituto de Geología, Universidad Nacional Autonoma de, Circuito Investigacion Cientifica, Ciudad Universitaria, City, 04510,, (2) Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Ensenada, Baja California, 22860,, (3) Centro de Geociencias, Universidad Nacional Autonoma de, Campus Juriquilla, Blvd. Juriquilla 3001, Queretaro, 76230,, (4) Earth, Environmental and Biological Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, 4001, Australia, (5) Scripps Institution of Oceanography, UCSD, 9500 Gilman Drive, La Jolla, CA Although Basin and Range style extension affected several areas of western since the Late Eocene, extension in the Gulf of California region (the Gulf Extensional Province GEP) is thought to have started as subduction waned and ended at ~ Ma. A general consensus also exists in considering the mid Miocene Comondú group as a supra subduction volcanic arc. Our new integration of the geology of the south east Gulf region, backed by 43 new Ar Ar and U Pb mineral ages and geochemical studies, document a widespread phase of extension in the southern GEP between latest Oligocene and Early Miocene that subsequently focused in the region of the future Gulf in the Middle Miocene. Upper Oligocene to Lower Miocene rocks across the southern Sierra Madre Occidental (SMO) (northern Nayarit and southern Sinaloa) were affected by major ~N S to NNW striking normal faults prior to ~21 Ma. Then, between ~21 and 11 Ma, a system of NNW SSE high angle extensional faults continued extending the southwestern side of the SMO. Rhyolitic domes, shallow intrusive bodies, and lesser basalts were emplaced along this extensional belt at Ma. In northern Sinaloa, large grabens were floored by huge dome complexes at ~21 17 Ma and filled by continental sediments with interlayered basalts dated at Ma, a setting and timing very similar to Sonora. Early to Middle Miocene volcanism, including the largely volcaniclastic Comondú strata in Baja California Sur, was thus emplaced in rift basins and was likely associated to decompression melting of upper mantle (inducing crustal partial melting) rather than to fluxing by fluids from the young subducting plate. Along the Nayarit and Sinaloa coast, flat lying basaltic lava flows dated at Ma are exposed just above the present sea level. Here, crustal thickness is almost half that in the unextended core of the SMO, implying significant lithosphere stretching before ~11 Ma. Our study shows that rifting began much earlier than Late Miocene and provided a fundamental control on the style and composition of volcanism from at least 30 Ma. We envision a sustained period of lithospheric stretching and magmatism during which the pace and breadth of extension changed at ~20 18 Ma to be narrower and likely more rapid, and again at ~12.5 Ma, when the kinematics of rifting became more oblique. Abstract ID#: /4

3 Password: Meeting: Cordilleran Section 109th Annual Meeting (20 22 May 2013) Session Type: Topical/Theme Selection: T10. Reconstructing the Pacific North America Plate Boundary Through Late Cenozoic Time Title: LATE OLIGOCENE TO MIDDLE MIOCENE RIFTING AND SYN EXTENSIONAL MAGMATISM IN THE SOUTHWESTERN SIERRA MADRE OCCIDENTAL, MEXICO: THE BEGINNING OF THE GULF OF CALIFORNIA RIFT Key Words: Gulf of California rift, Sierra Madre Occidental, syn extensional magmatism, Basin and Range Presentation Format: Oral Discipline Categories: Tectonics Scheduled For: Abstract Submission Fee: Paid (gsa 2013CD ) First Author Presenting Luca Ferrari Instituto de Geología, Universidad Nacional Autonoma de Circuito Investigacion Cientifica Ciudad Universitaria City, Office Phone: Confirmation Second Author Margarita Martinez Lopez Centro de Investigacion Cientifica y de Educacion Superior de Ensenada Ensenada, Baja California, Office Phone: marlopez@cicese.mx Third Author Maria Teresa Orozco Esquivel Centro de Geociencias, Universidad Nacional Autonoma de Campus Juriquilla Blvd. Juriquilla 3001 Queretaro, Office Phone: Fax Number: torozco@geociencias.unam.mx Confirmation torozco@geociencias.unam.mx 2/4

4 Fourth Author Scott Bryan Earth, Environmental and Biological Sciences, Queensland University of Technology GPO Box 2434 Brisbane, 4001 Australia Office Phone: scott.bryan@qut.edu.au Confirmation scott.bryan@qut.edu.au Fifth Author Jose Duque Centro de Geociencias, Universidad Nacional Autonoma de Campus Juriquilla Blvd. Juriquilla 3001 Queretaro, Office Phone: jduquetr@gmail.com Confirmation jduquetr@gmail.com Sixth Author Peter Lonsdale Scripps Institution of Oceanography, UCSD 9500 Gilman Drive La Jolla, CA Office Phone: plonsdale@ucsd.edu If necessary, you can make changes to your abstract between now and the deadline of Tuesday, February To access your submission in the future, use the direct link to your abstract submission from one of the automatic confirmation s that were sent to you during the submission. Or point your browser to to have that URL mailed to you again. Your username/password are / Any changes that you make will be reflected instantly in what is seen by the reviewers. You DO NOT need to go through all of the submission steps in order to change one thing. If you want to change the title, for example, just click "Title" in the abstract control panel and submit the new title. When you have completed your submission, you may close this browser window. 3/4

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