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Landscapes Developed on Ignimbrites
2017This paper analyses the landforms and landscapes developed on ignimbrites outcropping in different regions of Argentina: Portezuelo (province of Mendoza), Lihuel Calel (province of La Pampa), Pilcaniyeu (province of Rio Negro), Barda Colorada (province of Chubut) and Chon Aike (province of Santa Cruz). Some of these localities show clear resemblance to
Aguilera, Emilia Yolanda +2 more
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Sheathfolds in rheomorphic ignimbrites
Bulletin of Volcanology, 2004Structural reappraisal of several classic rheomorphic ignimbrites in Colorado, Idaho, the Canary Islands and Italy has, for the first time, revealed abundant oblique folds, curvilinear folds and sheathfolds which formed during emplacement. Like their equivalents in tectonic shear-zones, the sheathfold axes lie sub-parallel to a pervasive elongation ...
Branney, MJ, Barry, TL, Godchaux, M
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Nature, 1980
Conventionally1, three important characteristics of ignimbrites are that they show a very pronounced tendency to pond in topographic depressions, possess a flat, horizontal or gently sloping upper depositional surface, and have a thickness generally between 10 and 1,000 m. The youngest major ignimbrite, that of 1912 in the Valley of Ten Thousand Smokes
G. P. L. Walker +2 more
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Conventionally1, three important characteristics of ignimbrites are that they show a very pronounced tendency to pond in topographic depressions, possess a flat, horizontal or gently sloping upper depositional surface, and have a thickness generally between 10 and 1,000 m. The youngest major ignimbrite, that of 1912 in the Valley of Ten Thousand Smokes
G. P. L. Walker +2 more
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Somers Ignimbrite Formation: Cretaceous high-grade ignimbrites from South Island, New Zealand
Journal of Volcanology and Geothermal Research, 1997The Somers Ignimbrite Formation, part of an Upper Cretaceous calc–alkaline volcanic association dated at 89±2 Ma, forms the summit area of Mt. Somers, mid-Canterbury, New Zealand. It is the eroded remnant of a succession of 12 high-grade to extremely high-grade ignimbrite sheets each of which are designated as members.
T.R Smith, J.W Cole
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Nature, 1962
F. J. FITCH1 has criticized a new hypothesis proposed by me2 on the origin of ignimbrites of Pliocene to Pleistocene Age, from the North Island of New Zealand. The new petrogenetic concept is based on the presence of two contrasting glasses and their textural relationship, which suggest liquid immiscibility.
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F. J. FITCH1 has criticized a new hypothesis proposed by me2 on the origin of ignimbrites of Pliocene to Pleistocene Age, from the North Island of New Zealand. The new petrogenetic concept is based on the presence of two contrasting glasses and their textural relationship, which suggest liquid immiscibility.
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Journal of Volcanology and Geothermal Research, 2013
Abstract Rheomorphic structures in welded ignimbrites are commonly associated with deposition from hot pyroclastic flows on inclined topography or by tractional shear on aggrading agglutinate by the pyroclastic density current. We describe a type of rheomorphic deformation involving the formation of diapirs in ignimbrite following the re ...
F. Mundula, CIONI, RAFFAELLO, M. Mulas
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Abstract Rheomorphic structures in welded ignimbrites are commonly associated with deposition from hot pyroclastic flows on inclined topography or by tractional shear on aggrading agglutinate by the pyroclastic density current. We describe a type of rheomorphic deformation involving the formation of diapirs in ignimbrite following the re ...
F. Mundula, CIONI, RAFFAELLO, M. Mulas
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The ignimbrite source problem: Significance of a co-ignimbrite lag-fall deposit
Geology, 1977A co-ignimbrite lag-fall deposit is one that forms at or near the site of eruptive column collapse and consists mainly of pyroclasts that are too large and too heavy to be carried away in the resulting pumice flows. An example from Mexico is identified as such because it shows the same compositional zoning from rhyolite to andesite as the associated ...
John V. Wright, George P. L. Walker
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Nature, 1983
The Cerro Galan caldera, north-west Argentina, is one of the world's largest resurgent calderas but was not recognized as such until the advent of spacecraft imagery1,2. Here we present some initial results of the first scientific expedition to the caldera that was formed during a major eruption 2.5 Myr ago during which 1,000 km3 of ignimbrite was ...
P. W. Francis +8 more
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The Cerro Galan caldera, north-west Argentina, is one of the world's largest resurgent calderas but was not recognized as such until the advent of spacecraft imagery1,2. Here we present some initial results of the first scientific expedition to the caldera that was formed during a major eruption 2.5 Myr ago during which 1,000 km3 of ignimbrite was ...
P. W. Francis +8 more
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, 2014
The age of the Emeishan lavas in SW China remains poorly constrained because the extrusive rocks are (1) thermally overprinted and so represent an open system unsuitable for 40 Ar/ 39 Ar geochronology and (2) in most cases devoid of zircon so that it is ...
Yuting Zhong +3 more
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The age of the Emeishan lavas in SW China remains poorly constrained because the extrusive rocks are (1) thermally overprinted and so represent an open system unsuitable for 40 Ar/ 39 Ar geochronology and (2) in most cases devoid of zircon so that it is ...
Yuting Zhong +3 more
semanticscholar +1 more source
Crystal concentration in ignimbrites
Contributions to Mineralogy and Petrology, 1972A comparison of the crystal contents of selected sieve grades from 9 ignimbrites, with the yield of crystals from crushed pumice, shows that on average a tenfold concentration of crystals has taken place in the ignimbrites. This is explained by the selective loss of pumice by an amount equal to at least the present bulk of the samples studied.
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