Research Article| April 01, 1975 Pleistocene Tephra and Ash-Flow Deposits in the Volcanic Highlands of Guatemala ALLAN J. KOCH; ALLAN J. KOCH 1P.O. Box 5444, Denver, Colorado 80217 Search for other works by this author on: GSW Google Scholar HUGH McLEAN HUGH McLEAN 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1975) 86 (4): 529–541. https://doi.org/10.1130/0016-7606(1975)86<529:PTAADI>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 ALLAN J. KOCH, HUGH McLEAN; Pleistocene Tephra and Ash-Flow Deposits in the Volcanic Highlands of Guatemala. GSA Bulletin 1975;; 86 (4): 529–541. doi: https://doi.org/10.1130/0016-7606(1975)86<529:PTAADI>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 Twenty-six Pleistocene tephra layers, four ash-flow tuff deposits, and four fluvial-lacustrine sediment sequences, interstratified with paleosols, occur in an area of 1,500 km2 between Guatemala City and Lake Atitlán. Most of the tephra layers and one of the ash flows can be individually recognized in the field by mineralogy of Fe-Mg phenocrysts, texture, pumice color, and stratigraphic position.The texture, thickness, and distribution of the tephra layers indicate that they originated from five separate centers: the Pacaya volcanic complex, Agua Volcano, Acatenango or Fuego Volcanoes, the Lake Atitlán area, and the Laguna de Ayarza area. The exact sources of the ash flows are not known. Size of pumice clasts, pumice texture, and mineral content show that the basin-filling ash-flow tuff units are of primary origin and could not have resulted from inwash of previously deposited pumiceous tephra. Each ash-flow tuff apparently was deposited shortly after a tephra eruption.Reconnaissance work indicates that the H ash-flow tuff unit and its underlying tephra cover a major portion of the volcanic highlands — at least 16,000 km2 and 7,500 km2, respectively. Their source probably lies close to the Lake Atitlán area. These units should be extremely useful as time-stratigraphic marker horizons in other parts of the Guatemalan highlands.Radiometric dating indicates that most major tephra and ash-flow deposits were deposited between 40,000 yr and 1.84 m.y. ago. Were similar eruptions to occur today, widespread devastation and loss of life could result. 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.
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Koch et al. (1975) studied this question.