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Timing of mid-Tertiary volcanism in the Sierra Madre Occidental between Durango City and Mazatlan, Mexico

1977; Geological Society of America; Volume: 88; Issue: 10 Linguagem: Inglês

10.1130/0016-7606(1977)88 2.0.co;2

1943-2674

Fred W. McDowell, RICHARD P. KEIZER,

Geochemistry and Geologic Mapping

Research Article| October 01, 1977 Timing of mid-Tertiary volcanism in the Sierra Madre Occidental between Durango City and Mazatlan, Mexico FRED W. McDOWELL; FRED W. McDOWELL 1Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712 Search for other works by this author on: GSW Google Scholar RICHARD P. KEIZER RICHARD P. KEIZER 1Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712 Search for other works by this author on: GSW Google Scholar Author and Article Information FRED W. McDOWELL 1Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712 RICHARD P. KEIZER 1Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1977) 88 (10): 1479–1487. https://doi.org/10.1130/0016-7606(1977)88 2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation FRED W. McDOWELL, RICHARD P. KEIZER; Timing of mid-Tertiary volcanism in the Sierra Madre Occidental between Durango City and Mazatlan, Mexico. GSA Bulletin 1977;; 88 (10): 1479–1487. doi: https://doi.org/10.1130/0016-7606(1977)88 2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The relatively flat-lying rocks of the upper volcanic supergroup exposed between Durango City and Mazatlán in western Mexico consist of two distinct sequences. Near Durango about 800 m of ignimbrites and associated lavas and tuffs were emplaced between 32.1 and 28.3 m.y. ago (23 K-Ar dates). About 100 to 200 km to the west, at least 1,000 m of ignimbrites, lavas, and tuffs were emplaced 23.3 ± 0.3 m.y. ago, as indicated by 8 K-Ar dates. The two calc-alkalic sequences have significant but slight chemical and mineralogic differences, the older and eastern one being more alkalic. In the Durango vicinity, distinctive alkali basalts were erupted during normal faulting about 12 m.y. ago. Tholeiitic basalt of Quaternary age is also widespread there. Neither the normal faulting nor the basalts are prominent to the west, except near the Gulf of California.The upper volcanic supergroup commonly rests upon an older volcanic-intrusive complex approximately 100 to 45 m.y. old. Between 45 and 32 m.y. ago little or no magmatism occurred in the Sierra Madre Occidental, but major rift-related alkalic volcanic rocks were erupted then in Trans-Pecos Texas. Voluminous rhyolitic activity occurred between 32 and 23 m.y. ago in western Mexico. Intense volcanism began in southern Baja California 20 m.y. ago. The shifting position, nature, and amount of volcanism may correspond to changes in lithospheric plate motions in the east Pacific region, and 45 m.y., 32 m.y., and 23 m.y. ago appear to be key times of plate-boundary reorganization. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.