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Arc-rift transition volcanism in the Puertecitos Volcanic Province, northeastern Baja California, Mexico

Martín-Barajas, Arturo and Stock, Joann M. and Layer, Paul and Hausback, Brian and Renne, Paul and López-Martínez, Margarita (1995) Arc-rift transition volcanism in the Puertecitos Volcanic Province, northeastern Baja California, Mexico. Geological Society of America Bulletin, 107 (4). pp. 407-424. ISSN 0016-7606. doi:10.1130/0016-7606(1995)107<0407:ARTVIT>2.3.CO;2.

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The Neogene Puertecitos Volcanic Province of northeastern Baja California records a transition from arc-related volcanic activity to rift volcanism associated with opening of the Gulf of California. The eastern Puertecitos Volcanic Province is divided into three volcanic sequences based on mapping, petrology, and ^(40)Ar/^(39)Ar geochronology. The lowest sequence comprises early to middle Miocene (20–16 Ma) arc-related andesitic lava flows, volcanic necks, and proximal pyroclastic and epiclastic deposits up to 400 m in thickness, with minor basaltic lava flows. Following the initiation of crustal extension in the region (11–6 Ma), synrift volcanism produced two rhyolitic sequences that discordantly overlie the arc-related rocks. The older synrift sequence (6.4–5.8 Ma) is composed of rhyolite domes and a series of pyroclastic flows up to 300 m thick. The upper sequence (3.2–2.7 Ma) consists of ash-flow tuffs and pumice-lapilli pyroclastic flows, collectively up to 200 m thick. Minor andesite eruptions followed each episode of silicic synrift volcanism. Synvolcanic faults produced topographic relief that controlled deposition of the pyroclastic flows and caused gentler dips upsection. Rhyolite domes are aligned parallel to the predominant north-northwest to north-northeast fault pattern. All three volcanic sequences are calc-alkaline. However, the synrift andesite is characterized by lower K_(2)O, lower incompatible element concentrations, and less fractionation of light rare earth elements than the arc-related basalt and andesite. This suggests that the primary melts were more primitive for synrift andesite than for the arc-related rocks.

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Stock, Joann M.0000-0003-4816-7865
Additional Information:© 1995 Geological Society of America. Manuscript received by The Society December 23, 1993; revised manuscript received July 30, 1994; manuscript accepted September 14, 1994. Thanks to J. Kimbrough and M. Walawender for use of the XRF analytical facilities at San Diego State University. Special thanks to H. Delgado for fruitful discussions and for a preliminary revision of the draft manuscript. Thanks to Ch. Herzig and D. Kimbrough for multiple suggestions that also improved the manuscript, to V. Frias and G. Rendon for drafting, and to S. Augustin and G. Axen for improvement of the English usage. Special thanks to M. Sawlan and P. Weigand for their constructive reviews. A. Martín-Barajas was supported by CONACYT, Mexico, Grant 1224-T9203. J. Stock was partially supported by National Science Foundation Grants EAR-89-04022 and EAR-92-18381. Additional support for J. Stock and B. Hausback came from the Petroleum Research Fund of the American Chemical Society via Grant No. 21291-G.
Group:Seismological Laboratory
Funding AgencyGrant Number
CONACyT (Mexico)1224-T9203
American Chemical Society Petroleum Research Fund21291-G
Issue or Number:4
Record Number:CaltechAUTHORS:20140414-131946230
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Official Citation:Martín-Barajas, A., Stock, J. M., Layer, P., Hausback, B., Renne, P., & López-Martínez, M. (1995). Arc-rift transition volcanism in the Puertecitos Volcanic Province, northeastern Baja California, Mexico. Geological Society of America Bulletin, 107(4), 407-424. doi: 10.1130/0016-7606(1995)107<0407:artvit>;2
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:44930
Deposited On:15 Apr 2014 18:28
Last Modified:10 Nov 2021 16:58

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