Welding and rheomorphism of phonolitic fallout deposits from the Las Cañadas caldera, Tenerife, Canary Islands

Soriano, Carles; Zafrilla, Silvia; Martı́, Joan; Bryan, Scott; Fernand, Raymond Alexander; Ablay, G. J.

doi:10.1130/0016-7606(2002)114<0883:waropf>2.0.co;2

Cited by 34 publications

(33 citation statements)

References 42 publications

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“…Coarse pumice and lithics, poor sorting and some lithics up to 2 m in diameter may indicate proximity to vent and ballistic trajectories. Gradual transition from non-welded to lava-like has been interpreted as reflecting a decrease in the explosive activity in other welded fallout deposits of the Las Cañadas caldera (Soriano et al 2002). The same type of transition is observed in the Pedro Méndez Member and our interpretation is also that explosive activity decreased during eruption.…”

Section: Description and Interpretation Of Conduit-vent Structures Ansupporting

confidence: 73%

“…Most of them show a continuous facies transition from non-welded to lava-like. They are thought to correspond to individual eruptions and have been defined according to the following criteria: deposits vented from a known structure and showing lithological differences (clast size, clast composition, sorting) with adjacent deposits; deposits separated from other deposits by erosive surfaces and sedimentary layers; cooling units as defined by Soriano et al (2002); and radiometric dating. The lack of palaeosoils between units can possibly be explained due to the extreme climate conditions at the altitude of the eruptions (~2,500 m) and the short time elapsed between eruptions.…”

Section: Stratigraphy Of the Las Cañadas Caldera Wallmentioning

confidence: 99%

“…2 and Table 1). We have grouped the three "welding sequences" described by Soriano et al (2002) at the Montaña de Pasajirón stratigraphic section into two units: la Camellita Member and Pasajirón Member. La Camellita Member corresponds to the lowermost welding sequence.…”

Section: Stratigraphy Of the Las Cañadas Caldera Wallmentioning

confidence: 99%

“…La Camellita Member corresponds to the lowermost welding sequence. It is a single cooling unit, and a significant time (>100 days) may have encompassed after cooling and starting the deposition of the overlying unit (Soriano et al 2002), while the Pasajirón Member comprises the two upper welding sequences.…”

Section: Stratigraphy Of the Las Cañadas Caldera Wallmentioning

confidence: 99%

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Conduit-vent structures and related proximal deposits in the Las Cañadas caldera, Tenerife, Canary Islands

et al. 2006

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The Las Cañadas caldera wall and the outer slopes of the caldera provide three-dimensional exposures of numerous proximal-welded fallout deposits and have been mapped in detail. As a result, some parts of the Ucanca and Guajara Formations of the stratigraphy of Martí et al. (1994) have been divided into members that correspond to individual eruptions. Mapping has also revealed the occurrence of conduit-vent structures associated with proximal-welded fallout deposits. Conduit-vent structures consist of an upper flaring area and a lower narrow conduit. Conduit-vent geometry and dimensions include cylindrical plugs and eruptive fissures steeply dipping towards the caldera depression and elongated vents. The flaring area can be rather asymmetric and is usually filled by down-vent rheomorphic flow of the proximal fallout deposit. The lower conduits are filled by lava plug, agglutination of juveniles onto conduit walls and dyke intrusion with eventual dome extrusion. The eruption dynamics of welded fallout deposits and magma fragmentation within the conduit are consistent with an evolution from explosive to effusive. In this context conduit flow regimes evolve from turbulent to annular flow in which the conduit is progressively choked, and laminar flow leading to the final conduit closure.

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Section: Description and Interpretation Of Conduit-vent Structures Ansupporting

confidence: 73%

Section: Stratigraphy Of the Las Cañadas Caldera Wallmentioning

confidence: 99%

Section: Stratigraphy Of the Las Cañadas Caldera Wallmentioning

confidence: 99%

Section: Stratigraphy Of the Las Cañadas Caldera Wallmentioning

confidence: 99%

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Conduit-vent structures and related proximal deposits in the Las Cañadas caldera, Tenerife, Canary Islands

et al. 2006

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“…Flow folds, flow foliation and flow lineation of the densely welded and lava-like rocks indicate that rheomorphism followed deposition. The succession of facies, textures and components observed from non-welded to densely welded parts of the La Grieta Member is similar to other welded fallout in the Las Cañadas caldera in which dense welding results from the extreme attenuation and coalescence of juvenile clasts (Martí and Ablay 1994;Soriano et al 2002). Welding is enhanced by an increase in the number of arrivals of hotter and less viscous juveniles that agglutinate upon landing during eruption.…”

Section: Interpretation Of Observed Structures and Texturesmentioning

confidence: 86%

Giant gas bubbles in a rheomorphic vent fill at the Las Cañadas caldera, Tenerife (Canary Islands)

et al. 2009

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During rheomorphism subsequent to fallout deposition, a portion of the densely welded fallout of the La Grieta Member flowed back into the vent from where it was erupted, while the rest of it flowed down the outer slopes of the Las Cañadas caldera in Tenerife. The welded fallout and conduit-vent structure are physically connected and constitute a rare example of this type of deposits rooted to its feeder conduit and exposed in the caldera wall. The lower part of the vent-filling rheomorphic rocks shows gas bubbles and cavities that increase in size (up to 4 m) down vent. Bubbles are deformed against other bubbles, against the steep vent walls, flattened parallel to the flow foliation planes, and elongated parallel to the flow lineation and flow fold axes. The preservation of such giant bubbles, rather than their formation, seems to be a pretty unique feature of the phonolitic products investigated here and it is likely the result of the combination of factors that acted to preserve, in the surrounding of the glass transition interval, the sealing and the late stage cooling of a pressurized system. In addition, strain drop at the base of the vent-filling rheomorphic flow caused by flow stopping against vertical vent walls may have promoted rapid gas exsolution and the formation of large bubbles.

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Geologic evolution of the Canarian Islands of Lanzarote, Fuerteventura, Gran Canaria and La Gomera and comparison of landslides at these islands with those at Tenerife, La Palma and El Hierro

Acosta¹,

Uchupi²,

Muñoz³

et al.

Geophysics of the Canary Islands

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Welding and rheomorphism of phonolitic fallout deposits from the Las Cañadas caldera, Tenerife, Canary Islands

Cited by 34 publications

References 42 publications

Conduit-vent structures and related proximal deposits in the Las Cañadas caldera, Tenerife, Canary Islands

Conduit-vent structures and related proximal deposits in the Las Cañadas caldera, Tenerife, Canary Islands

Giant gas bubbles in a rheomorphic vent fill at the Las Cañadas caldera, Tenerife (Canary Islands)

Geologic evolution of the Canarian Islands of Lanzarote, Fuerteventura, Gran Canaria and La Gomera and comparison of landslides at these islands with those at Tenerife, La Palma and El Hierro

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