Abstract
The tephra dispersal mechanisms of rhyolitic glaciovolcanic eruptions are little known, but can be investigated through the correlation of eruptive products across multiple depositional settings. Using geochemistry and geochronology, we correlate a regionally important Pleistocene tephra horizon—the rhyolitic component of North Atlantic Ash Zone II (II-RHY-1)—and the Thorsmork Ignimbrite with rhyolitic tuyas at Torfajokull volcano, Iceland. The eruption breached an ice mass >400 m thick, leading to the widespread dispersal of II-RHY-1 across the North Atlantic and the Greenland ice sheet. Locally, pyroclastic density currents traveled across the ice surface, depositing the variably welded Thorsmork Ignimbrite beyond the ice margin and ~30 km from source. The widely dispersed products of this eruption represent a valuable isochronous tie line between terrestrial, marine, and ice-core paleoenvironmental records. Using the tephra horizon, estimates of ice thickness and extent derived from the eruption deposits can be directly linked to the regional climate archive, which records the eruption at the onset of Greenland Stadial 15.2.
Highlights
The stratigraphic correlation of volcanic products, tephra, is a powerful means of studying the past eruptive behavior of volcanoes and linking together disparate paleoenvironmental records (Lowe, 2011)
Pyroclastic density currents traveled across the ice surface, depositing the variably welded Thórsmörk Ignimbrite beyond the ice margin and ~30 km from source
Estimates of ice thickness and extent derived from the eruption deposits can be directly linked to the regional climate archive, which records the eruption at the onset of Greenland Stadial 15.2
Summary
The stratigraphic correlation of volcanic products, tephra, is a powerful means of studying the past eruptive behavior of volcanoes and linking together disparate paleoenvironmental records (Lowe, 2011). We use correlation methods to (1) assess the tephra dispersal mechanisms of rhyolitic glaciovolcanic eruptions, and (2) precisely integrate glaciovolcanism-derived paleoenvironmental data with the regional climate record. Current knowledge of the behavior of rhyolitic glaciovolcanic eruptions is drawn from proximal deposits only (e.g., Stevenson et al, 2011; Owen et al, 2013a). Without any established correlations between glaciovolcanic rhyolites and distal tephras, it is not known whether these eruptions have produced widespread tephra deposits (Tuffen et al, 2002, 2007; McGarvie, 2009)
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