Volcanic history and 40Ar/39Ar and 14C geochronology of Terceira Island, Azores, Portugal

Journal of Volcanology and Geothermal Research
By: , and 



Seven new 40Ar/39Ar and 23 new radiocarbon ages of eruptive units, in support of new geologic mapping, improve the known chronology of Middle to Late Pleistocene and Holocene volcanic activity on the island of Terceira, Azores and define an east-to-west progression in stratovolcano growth. The argon ages indicate that Cinco Picos Volcano, the oldest on Terceira, completed its main subaerial cone building activity by about 370–380 ka. Collapse of the upper part of the stratovolcanic edifice to form a 7 × 9 km caldera occurred some time after 370 ka. Postcaldera eruptions of basalt from cinder cones on and near the caldera floor and trachytic pyroclastic flow and pumice fall deposits from younger volcanoes west of Cinco Picos have refilled much of the caldera. The southern portion of Guilherme Moniz Volcano, in the central part of the island, began erupting prior to 270 ka and produced trachyte domes, flows, and minor pyroclastic deposits until at least 111 ka. The northern part of Guilherme Moniz Caldera is less well exposed than the southern part, but reflects a similar age range. The northwest portion of the caldera was formed sometime after 44 ka. Several well-studied ignimbrites that blanket much of the island likely erupted from Guilherme Moniz Volcano. The Pico Alto Volcanic Center, a tightly spaced cluster of trachyte domes and short flows, is a younger part of Guilherme Moniz Volcano. Stratigraphic studies and our new radiocarbon ages suggest that most of the Pico Alto eruptions occurred during the period from about 9000 to 1000 years BP. Santa Barbara Volcano is the youngest stratovolcano on Terceira, began erupting prior to 29 ka, and has been active historically.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Volcanic history and 40Ar/39Ar and 14C geochronology of Terceira Island, Azores, Portugal
Series title Journal of Volcanology and Geothermal Research
DOI 10.1016/j.jvolgeores.2006.03.016
Volume 156
Issue 1-2
Year Published 2006
Language English
Publisher Elsevier Science
Contributing office(s) Volcano Hazards Program
Description 13 p.
Larger Work Subtype Journal Article
First page 103
Last page 115
Country Portugal
State Azores
Other Geospatial Terceira Island
Online Only (Y/N) N
Additional Online Files (Y/N) N
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