Origin of accretionary lapilli within ground-hugging density currents: Evidence from pyroclastic couplets on Tenerife

Abstract

Research Article| January 01, 2010 Origin of accretionary lapilli within ground-hugging density currents: Evidence from pyroclastic couplets on Tenerife R.J. Brown; R.J. Brown † 1Volcano Dynamics Group, Department of Earth and Environmental Sciences, Open University, Walton Hall, Milton Keynes, MK7 6AA, UK †E-mail: [e-mail] Search for other works by this author on: GSW Google Scholar M.J. Branney; M.J. Branney 2Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK Search for other works by this author on: GSW Google Scholar C. Maher; C. Maher § 2Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK §Present address: Neftex Petroleum Consultants, 115BD Milton Park, Abingdon, Oxfordshire OX14 4SA, UK. Search for other works by this author on: GSW Google Scholar P. Dávila-Harris P. Dávila-Harris 2Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK Search for other works by this author on: GSW Google Scholar Author and Article Information R.J. Brown † 1Volcano Dynamics Group, Department of Earth and Environmental Sciences, Open University, Walton Hall, Milton Keynes, MK7 6AA, UK M.J. Branney 2Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK C. Maher § 2Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK P. Dávila-Harris 2Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK †E-mail: [e-mail] §Present address: Neftex Petroleum Consultants, 115BD Milton Park, Abingdon, Oxfordshire OX14 4SA, UK. Publisher: Geological Society of America Received: 09 Apr 2008 Revision Received: 24 Oct 2008 Accepted: 06 Nov 2008 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2010 Geological Society of America GSA Bulletin (2010) 122 (1-2): 305–320. https://doi.org/10.1130/B26449.1 Article history Received: 09 Apr 2008 Revision Received: 24 Oct 2008 Accepted: 06 Nov 2008 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation R.J. Brown, M.J. Branney, C. Maher, P. Dávila-Harris; Origin of accretionary lapilli within ground-hugging density currents: Evidence from pyroclastic couplets on Tenerife. GSA Bulletin 2010;; 122 (1-2): 305–320. doi: https://doi.org/10.1130/B26449.1 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 Aggregation of airborne particles is an important way in which the atmosphere is cleansed of fine dust particles, such as following explosive eruptions and meteorite impacts. We identify successive stages in the growth history of particle aggregates based upon well-preserved ash aggregate–bearing pyroclastic layers on Tenerife. The layers are persistently organized into couplets made up of a lower ignimbrite layer and an upper, widespread coignimbrite ash-fall layer. The upper part of each ignimbrite contains whole and fragmented concentric-laminated accretionary lapilli, whereas the overlying coignimbrite ash-fall layer lacks accretionary lapilli and is composed of framework-supported smaller and nonlaminated ash pellets, sometimes slightly deformed or partly disaggregated. The pellets resemble the cores of the larger accretionary lapilli in the underlying ignimbrite layer. These field relations are repeated numerous times in several different successions, and they indicate that ash pellets, not accretionary lapilli, form within the coignimbrite ash plumes. Some pellets fell directly to the ground, producing coignimbrite ash-fall layers, but others settled into pyroclastic density currents, where they accreted successive concentric laminations of fine ash as they circulated through the variously turbulent levels of the stratified current, and heat of the lower part of the current dried and partly lithified them into brittle accretionary lapilli. The fully formed whole and broken accretionary lapilli were then deposited from the current along with ash and pumice lapilli. Numerous ignimbrite veneers on Tenerife have the form of ash layers, a few centimeters thick, that drape topography and locally contain matrix-supported accretionary lapilli. Most volcanoes lack laterally continuous field exposure, and such accretionary lapilli–bearing layers might be mistaken for ash-fall deposits. We highlight the value of careful distinction between different types of ash aggregate facies when interpreting the origin of pyroclastic deposits, for example, during hazard assessments. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.