Stratigraphy, age and correlation of Lepué Tephra: A widespread c. 11 000 cal a BP marker horizon sourced from the Chaitén Sector of southern Chile

Brent V. Alloway, Patricio I. Moreno, Nicholas Pearce, Ricardo De Pol-Holz, William I. Henriquez, Oscar H. Pesce, Esteban Sagredo, Gustavo Villarosa, Valeria Outes

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Abstract

We describe the stratigraphy, age and correlation of a prominent tephra marker, named Lepué Tephra, extensively distributed in north-western Patagonia. Lepué Tephra is well dated at c. 11 000 cal a BP from numerous lake and soil cover-bed sequences and its recognition is useful for assessing the rate and timing of deglaciation as well as associated environmental changes in this region during the last glacial termination and early Holocene. Lepué Tephra has attributes typical of a complex and compositionally zoned phreatomagmatic eruptive. While the initial rhyolitic phase can be readily distinguished from multiple eruptive products sourced from the adjacent Volcán Chaitén, the main erupted end member is of basaltic–andesitic bulk composition − similar to younger tephras sourced from Holocene monogenetic cones adjacent to the Volcán Michimahuida massif (tMim). Lepué Tephra can be correlated to an equivalent-aged pyroclastic flow deposit (Amarillo Ignimbrite) prominently distributed in the south-eastern sector of tMim. The source vent for these co-eruptive events is obscured by an extensive ice field and is currently unknown. The widespread radially symmetrical distribution of Lepué Tephra centred on tMim cannot be attributed solely to volcanological considerations. Reduced Southern Hemisphere westerly wind influence interpreted from climate proxies at the time of eruption are also implicated
Original languageEnglish
Pages (from-to)795-829
JournalJournal of Quaternary Science
Volume32
Issue number6
DOIs
Publication statusPublished - 03 Aug 2017

Keywords

  • Lepué Tephra
  • north-west Patagonia
  • tephrostratigraphy
  • Volcán Chaitén
  • Volcán Michimahuida

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