TY - JOUR
T1 - The late Quaternary Diego Hernandez Formation, Tenerife
T2 - Volcanology of a complex cycle of voluminous explosive phonolitic eruptions
AU - Edgar, C. J.
AU - Wolff, J. A.
AU - Olin, P. H.
AU - Nichols, H. J.
AU - Pittari, A.
AU - Cas, R. A.F.
AU - Reiners, P. W.
AU - Spell, T. L.
AU - Martí, J.
N1 - Funding Information:
This research was supported by an ARC Small Grant to RC, and discretionary research funds from Monash University, NSF grant EAR-0001013 to JW, and MCyT REN2001-0502 / RIES and EC EVG1-CT-2002-00058 to JM. We thank Peter Larson, Jeff Grandy, Inés Galindo, Nemesio Pérez, Jill Middleton, Keith Brunstad, Janet Sumner and Charles Knaack for assistance in the field and discussion on aspects of Tenerife geology, and Jesus Garrido and the staff of the Parador de Las Cañadas for their unflagging hospitality. We take this opportunity to pay tribute to the memory of George Walker, whose genius inspired several generations of volcanologists. George first examined the plinian deposits and ignimbrites of Tenerife nearly 40 years ago, and, although never published as a complete study, his observations played a large role in the physical volcanology revolution that George almost single-handedly created from the late 1960s onwards. With his characteristic unselfishness, George gave us copies of his field notes and encouraged us to carry the work on the Bandas del Sur pyroclastic deposits closer to completion. We are honoured to have done so.
PY - 2007/2/1
Y1 - 2007/2/1
N2 - The Diego Hernandez Formation (DHF; 600-ca. 180 ka) represents the products of the most recent complete cycle of phonolitic explosive volcanism on Tenerife (Canary Islands, Spain). We provide a revised and detailed stratigraphy, new 40Ar/39Ar and (U-Th)/He age determinations for major eruptive units, a summary of new chemical data and an overview of the key characteristics of the cycle, including volume estimates, dispersal patterns, eruption styles, phreatomagmatic influences and caldera collapse episodes. The complex stratigraphy of the DHF is divided into 20 named members, each representing a major eruption, as well as numerous unnamed members of limited present-day exposure. The major eruptions are represented by the Fortaleza (370 ka), Roque (347 ka, 3 km3), Aldea (319 ka, 3 km3), Fasnia (309 ka, 13 km3), Poris (268 ka, 3.5 km3), Arafo (4 km3), Caleta (223 ka, 3.5 km3) and Abrigo (between 196 and 171 ka, 20 km3) Members. The Aldea, Fasnia and Poris Members consist of highly complex successions of plinian fall, surge and flow deposits and several of the eruptions produced widespread and internally complex ignimbrite sheets. Phreatomagmatism occurred most frequently in the opening phase of the eruptions but also recurred repeatedly throughout many of the sequences. Inferred sources of water include a shallow caldera lake and groundwater, and intermittent phreatomagmatic activity was an important influence on eruption style. Another important factor was conduit and vent instability, which frequently loaded the eruption column with dense lithic debris and occasionally triggered column collapse and ignimbrite formation. Most of the major DHF eruptions were triggered by injection of mafic magma into existing phonolitic magma bodies. Two phonolitic magma types were available for eruption during the lifetime of the DHF, but each was dominant at different times. The results presented here support a caldera collapse rather than a landslide model for the origin of the Las Cañadas Caldera, although the evolution of the caldera is evidently more complex and incremental than first thought.
AB - The Diego Hernandez Formation (DHF; 600-ca. 180 ka) represents the products of the most recent complete cycle of phonolitic explosive volcanism on Tenerife (Canary Islands, Spain). We provide a revised and detailed stratigraphy, new 40Ar/39Ar and (U-Th)/He age determinations for major eruptive units, a summary of new chemical data and an overview of the key characteristics of the cycle, including volume estimates, dispersal patterns, eruption styles, phreatomagmatic influences and caldera collapse episodes. The complex stratigraphy of the DHF is divided into 20 named members, each representing a major eruption, as well as numerous unnamed members of limited present-day exposure. The major eruptions are represented by the Fortaleza (370 ka), Roque (347 ka, 3 km3), Aldea (319 ka, 3 km3), Fasnia (309 ka, 13 km3), Poris (268 ka, 3.5 km3), Arafo (4 km3), Caleta (223 ka, 3.5 km3) and Abrigo (between 196 and 171 ka, 20 km3) Members. The Aldea, Fasnia and Poris Members consist of highly complex successions of plinian fall, surge and flow deposits and several of the eruptions produced widespread and internally complex ignimbrite sheets. Phreatomagmatism occurred most frequently in the opening phase of the eruptions but also recurred repeatedly throughout many of the sequences. Inferred sources of water include a shallow caldera lake and groundwater, and intermittent phreatomagmatic activity was an important influence on eruption style. Another important factor was conduit and vent instability, which frequently loaded the eruption column with dense lithic debris and occasionally triggered column collapse and ignimbrite formation. Most of the major DHF eruptions were triggered by injection of mafic magma into existing phonolitic magma bodies. Two phonolitic magma types were available for eruption during the lifetime of the DHF, but each was dominant at different times. The results presented here support a caldera collapse rather than a landslide model for the origin of the Las Cañadas Caldera, although the evolution of the caldera is evidently more complex and incremental than first thought.
KW - Tenerife
KW - caldera
KW - ignimbrite
KW - phonolite
KW - phreatomagmatism
KW - plinian
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U2 - 10.1016/j.jvolgeores.2006.06.001
DO - 10.1016/j.jvolgeores.2006.06.001
M3 - Article
AN - SCOPUS:33845941456
SN - 0377-0273
VL - 160
SP - 59
EP - 85
JO - Journal of Volcanology and Geothermal Research
JF - Journal of Volcanology and Geothermal Research
IS - 1-2
ER -