Bypassing and diachronous deposition from density currents: Evidence from a giant regressive bed form in the Poris ignimbrite, Tenerife, Canary Islands

Research Article| May 01, 2004 Bypassing and diachronous deposition from density currents: Evidence from a giant regressive bed form in the Poris ignimbrite, Tenerife, Canary Islands R.J. Brown; R.J. Brown 1Geology Department, University of Leicester, University Road, Leicester LE1 7RH, UK Search for other works by this author on: GSW Google Scholar M.J. Branney M.J. Branney 1Geology Department, 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 1Geology Department, University of Leicester, University Road, Leicester LE1 7RH, UK M.J. Branney 1Geology Department, University of Leicester, University Road, Leicester LE1 7RH, UK Publisher: Geological Society of America Received: 09 Sep 2003 Revision Received: 13 Jan 2004 Accepted: 18 Jan 2004 First Online: 02 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2004) 32 (5): 445–448. https://doi.org/10.1130/G20188.1 Article history Received: 09 Sep 2003 Revision Received: 13 Jan 2004 Accepted: 18 Jan 2004 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation R.J. Brown, M.J. Branney; Bypassing and diachronous deposition from density currents: Evidence from a giant regressive bed form in the Poris ignimbrite, Tenerife, Canary Islands. Geology 2004;; 32 (5): 445–448. doi: https://doi.org/10.1130/G20188.1 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 SocietyGeology Search Advanced Search Abstract Exceptional longitudinal exposure through an ignimbrite sheet on the southern flanks of Las Cañadas volcano, Tenerife, Canary Islands, reveals a giant regressive bed form, >520 m long. It comprises sourceward-dipping diffuse lenses, ∼50 m long, of massive and diffuse-bedded lapilli tuff. Its architectural relationships indicate that at any one moment in time, deposition was restricted to an ∼50-m-long longitudinal depositional zone, bounded both upslope and downslope by extensive bypassing zones. The regressive architecture shows that the zone of deposition gradually migrated sourceward as the current passed. Nonpersistent scours indicate that the current was locally and momentarily erosive, although at many locations there is little evidence for substantial erosion or deposition, and most of the pyroclastic load seems to have entirely bypassed subaerial slopes to enter the Atlantic Ocean, ∼20 km from the source. The ignimbrite is diachronous, and any single vertical section through it represents only a short phase of the current's protracted depositional history. Similarly protracted and complex flow histories elsewhere may be easily overlooked at typical field exposures of ignimbrites, turbidites, and lahar deposits, leading to significantly underestimated flow durations and volumes. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.