Volcanism and erosion during the past 930 k.y. at the Tatara–San Pedro complex, Chilean Andes

Abstract

Research Article| February 01, 1997 Volcanism and erosion during the past 930 k.y. at the Tatara–San Pedro complex, Chilean Andes B. S. Singer; B. S. Singer 1Départemente de Minéralogie, Université de Genève, 1211 Genève 4, Switzerland Search for other works by this author on: GSW Google Scholar R. A. Thompson; R. A. Thompson 2U.S. Geological Survey, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar M. A. Dungan; M. A. Dungan 1Départemente de Minéralogie, Université de Genève, 1211 Genève 4, Switzerland Search for other works by this author on: GSW Google Scholar T. C. Feeley; T. C. Feeley 1Départemente de Minéralogie, Université de Genève, 1211 Genève 4, Switzerland Search for other works by this author on: GSW Google Scholar S. T. Nelson; S. T. Nelson 3Woodward-Clyde Federal Services, Las Vegas, Nevada 89109 Search for other works by this author on: GSW Google Scholar J. C. Pickens; J. C. Pickens 4Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003-5820 Search for other works by this author on: GSW Google Scholar L. L. Brown; L. L. Brown 4Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003-5820 Search for other works by this author on: GSW Google Scholar A. W. Wulff; A. W. Wulff 4Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003-5820 Search for other works by this author on: GSW Google Scholar J. P. Davidson; J. P. Davidson 5Department of Earth and Space Sciences, University of California, Los Angeles, California 90024 Search for other works by this author on: GSW Google Scholar J. Metzger J. Metzger 1Départemente de Minéralogie, Université de Genève, 1211 Genève 4, Switzerland Search for other works by this author on: GSW Google Scholar Author and Article Information B. S. Singer 1Départemente de Minéralogie, Université de Genève, 1211 Genève 4, Switzerland R. A. Thompson 2U.S. Geological Survey, Denver, Colorado 80225 M. A. Dungan 1Départemente de Minéralogie, Université de Genève, 1211 Genève 4, Switzerland T. C. Feeley 1Départemente de Minéralogie, Université de Genève, 1211 Genève 4, Switzerland S. T. Nelson 3Woodward-Clyde Federal Services, Las Vegas, Nevada 89109 J. C. Pickens 4Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003-5820 L. L. Brown 4Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003-5820 A. W. Wulff 4Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003-5820 J. P. Davidson 5Department of Earth and Space Sciences, University of California, Los Angeles, California 90024 J. Metzger 1Départemente de Minéralogie, Université de Genève, 1211 Genève 4, Switzerland Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1997) 109 (2): 127–142. https://doi.org/10.1130/0016-7606(1997)109<0127:VAEDTP>2.3.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 B. S. Singer, R. A. Thompson, M. A. Dungan, T. C. Feeley, S. T. Nelson, J. C. Pickens, L. L. Brown, A. W. Wulff, J. P. Davidson, J. Metzger; Volcanism and erosion during the past 930 k.y. at the Tatara–San Pedro complex, Chilean Andes. GSA Bulletin 1997;; 109 (2): 127–142. doi: https://doi.org/10.1130/0016-7606(1997)109<0127:VAEDTP>2.3.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 Geologic mapping, together with 73 new K-Ar and 40Ar/39Ar age determinations of 45 samples from 17 different volcanic units, plus paleomagnetic orientations, geochemical compositions, and terrestrial photogrammetry are used to define the chronostratigraphy of the Tatara–San Pedro complex, an eruptive center at 36°S on the volcanic front of the Andean southern volcanic zone. The Tatara–San Pedro complex preserves ≈55 km3 of lavas that erupted from at least three central vent regions. Remnant, unconformity-bound sequences of lavas are separated by lacunae that include significant periods of erosion. Quaternary volcanism commenced ca. 930 ka with eruption of voluminous dacitic magma, followed 100 k.y. later by the only major rhyolitic eruption. From 780 ka onward, more than 80% of the preserved volume is basaltic andesite (52%–57% SiO2), but petrographically and geochemically diverse dacitic magmas (63%–69% SiO2) erupted sporadically throughout this younger, dominantly mafic phase of activity. A few basaltic lavas (49%–52% SiO2) are present, mainly in portions of the complex older than 230 ka. The number of vents, the petrologic and geochemical diversity, and the temporal distribution of mafic and silicic lavas are consistent with emplacement of many separate batches of mafic magma into the shallow crust beneath the Tatara–San Pedro complex over the past million years.Nearly two-thirds of the preserved volume of the Tatara–San Pedro complex comprises the two youngest volcanoes, which were active between ca. 188–83 ka and 90–19 ka. Repeated advances of mountain glaciers punctuated growth of the complex with major erosional episodes that removed much of the pre-200 ka volcanic record, particularly on the south flank of the complex. Dating the inception of a glaciation on the basis of preserved material is difficult, but the age of the oldest lava above a lacuna may be used to estimate the timing of deglaciation. On this basis, the argon ages of basal lavas of multiple sequences indicate minimum upper limits of lacunae at ca. 830, 790, 610, 400, 330, 230, 110, and 17 ka. These are broadly consistent with global ice-volume peaks predicted by the oxygen isotope-based astronomical time scale and with age brackets on North American glacial advances. Estimated growth rates for the two young volcanoes are 0.2 to 0.3 km3/k.y.; these are three to five times greater than a growth rate estimated from all preserved lavas in the complex (0.06 km3/k.y.). Removal of up to 50%–95% of the material erupted between 930 and 200 ka by repeated glacial advances largely explains this discrepancy, and it raises the possibility that episodic erosion of mid-latitude frontal arc complexes may be extensive and common. 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.