The stratigraphy and emplacement of welded and lava-like ignimbrites of the Las Cañadas Caldera, Tenerife

Campbell, Pamela Louise (2021) The stratigraphy and emplacement of welded and lava-like ignimbrites of the Las Cañadas Caldera, Tenerife. PhD thesis, University of Glasgow.

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Lava-like and welded pyroclastic deposits are commonly associated with vent-proximal, high-temperature explosive eruptions, and due to the nature of welding of these deposits, evidence of the depositional and sedimentological aspect of the deposit is often absent. As a result, the dynamics and mechanisms of deposition and welding processes in high-temperature eruptions are poorly understood and this has often led to the misinterpretation of such welded deposits. This limited understanding can lead to misleading interpretations and underestimations of the potential hazards associated with active volcanic environments. This project is an investigation into the behaviour and emplacement of the welded and lava-like deposits belonging to the Ucanca and Guajara Formations of the southern flank of the Las Cañadas Caldera, Tenerife.

Six individual eruptive packages are described and documented, representing explosive, destructive and constructive stages of the Ucanca and Guajara caldera-forming episodes. A systematic field campaign involving mapping and detailed stratigraphic logging of the deposits, combined with methodological sampling for petrographic, geochemical and thermal analysis, together with determination of the rocks’ physical properties, has established the emplacement dynamics of the units, as well as geochemical and welding variations throughout individual units and across the proposed members. The description and analysis of welding textures at different scales allowed for sensitive mapping of welding intensity, providing insights into the controls and depositional factors contributing to the deformation of pyroclasts, both syn- and post-emplacement.

Together these data provide the first detailed robust interpretation of the Ucanca and Guajara deposits, a key stage in the volcanic evolution of Tenerife. Extensive evidence is presented in support of their interpretation as deposits from a series of extremely high-grade pyroclastic density currents (PDCs). A variety of novel and exciting welding textures are documented, providing insight into the emplacement dynamics, thermal histories, and constraints on welding such as current interaction with variable lithic input. This work proposes a new classification system for high-grade ignimbrites, which are overly simplified and omitted in existing schemes, and may be applied to deposits in other volcanic settings.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: welded, welding, lava-like, ignimbrites, volcanology, tenerife, caldera.
Subjects: Q Science > QE Geology
Colleges/Schools: College of Science and Engineering > School of Geographical and Earth Sciences > Earth Sciences
Supervisor's Name: Brown, Dr. David
Date of Award: 2021
Depositing User: Mrs Pamela Campbell
Unique ID: glathesis:2021-82123
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 15 Apr 2021 10:56
Last Modified: 15 Apr 2021 15:51
Thesis DOI: 10.5525/gla.thesis.82123

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