Migration of volcanism in the San Francisco volcanic field, Arizona

Research Article| February 01, 1986 Migration of volcanism in the San Francisco volcanic field, Arizona KENNETH L. TANAKA; KENNETH L. TANAKA 1U.S. Geological Survey, 2255 North Gemini Drive, Flagstaff, Arizona 86001 Search for other works by this author on: GSW Google Scholar EUGENE M. SHOEMAKER; EUGENE M. SHOEMAKER 1U.S. Geological Survey, 2255 North Gemini Drive, Flagstaff, Arizona 86001 Search for other works by this author on: GSW Google Scholar GEORGE E. ULRICH; GEORGE E. ULRICH 2U.S. Geological Survey, Hawaiian Volcano Observatory, Hawaii National Park, Hawaii 96718 Search for other works by this author on: GSW Google Scholar EDWARD W. WOLFE EDWARD W. WOLFE 2U.S. Geological Survey, Hawaiian Volcano Observatory, Hawaii National Park, Hawaii 96718 Search for other works by this author on: GSW Google Scholar Author and Article Information KENNETH L. TANAKA 1U.S. Geological Survey, 2255 North Gemini Drive, Flagstaff, Arizona 86001 EUGENE M. SHOEMAKER 1U.S. Geological Survey, 2255 North Gemini Drive, Flagstaff, Arizona 86001 GEORGE E. ULRICH 2U.S. Geological Survey, Hawaiian Volcano Observatory, Hawaii National Park, Hawaii 96718 EDWARD W. WOLFE 2U.S. Geological Survey, Hawaiian Volcano Observatory, Hawaii National Park, Hawaii 96718 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1986) 97 (2): 129–141. https://doi.org/10.1130/0016-7606(1986)97<129:MOVITS>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 MailTo Tools Icon Tools Get Permissions Search Site Citation KENNETH L. TANAKA, EUGENE M. SHOEMAKER, GEORGE E. ULRICH, EDWARD W. WOLFE; Migration of volcanism in the San Francisco volcanic field, Arizona. GSA Bulletin 1986;; 97 (2): 129–141. doi: https://doi.org/10.1130/0016-7606(1986)97<129:MOVITS>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 remanent magnetization of volcanic rocks has been determined at 650 sites in the San Francisco volcanic field in the southern part of the Colorado Plateau. The polarity of remanent magnetization—combined with K-Ar age determinations, spatial and petrographic associations, stratigraphic relations, and state of preservation of the cinder cones—provides a basis for assignment to known magnetic polarity epochs of 610 mafic vents and >100 intermediate to silicic flows, flow sequences, and vents. The age assignments for basaltic rocks include 243 Brunhes (<0.73 Ma) vents, 220 Matuyama (0.73 to 2.48 Ma) vents, and 147 pre-Matuyama (2.48 to about 5.0 Ma) vents. Basaltic volcanism migrated northeastward before Matuyama time at a rate of ∼1.2 cm/yr and eastward (S87° ± 5°E) over the past 2.5 m.y. at a rate of 2.9 ± 0.3 cm/yr. Concomitant acceleration in total magma production (from 75 to 1,400 × 10−6 km3/yr) and frequency of basaltic eruptions (from 1 per 17,000 yr to 1 per 3,000 yr) occurred between 5 and 0.25 Ma. For the past 0.25 m.y., magma production (∼180 × 10−6 km3/yr) and perhaps eruption frequency have decreased. This evolutionary sequence, coupled with the lead and strontium-isotopic composition of the rocks, can be explained by magmatism caused by shear heating at the base of the lithosphere. We propose that this eastward drift of volcanic activity represents absolute westward motion of the North American plate. Our model is in agreement with a model in which the African plate is fixed to the deep mantle. 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.