Martin Smellie et al_2018_BV_Spatter-rich pdc deposit Mason Spur_COMPLETE mock up version.pdf (2.48 MB)
Formation of a spatter-rich pyroclastic density current deposit in a Neogene sequence of trachytic-mafic igneous rocks at Mason Spur, Erebus volcanic province, Antarctica
journal contributionposted on 2018-04-06, 08:12 authored by A. P Martin, John. L Smellie, A. F Cooper, D. B Townsend
Erosion has revealed a remarkable section through the heart of a volcanic island, Mason Spur, in the southwestern Ross Sea, Antarctica, including an unusually well-exposed section of caldera fill. The near-continuous exposure, 10 km laterally and > 1 km vertically, cuts through Cenozoic alkalic volcanic rocks of the Erebus volcanic province (McMurdo Volcanic Group) and permits the study of an ancient volcanic succession that is rarely available due to subsequent burial or erosion. The caldera filling sequence includes an unusual trachytic spatter-rich lapilli tuff (ignimbrite) facies that is particularly striking because of the presence of abundant black fluidal, dense juvenile spatter clasts of trachytic obsidian up to 2 m long supported in a pale cream-coloured pumiceous lapilli tuff matrix. Field mapping indicates that the deposit is an ignimbrite and, together with petrological considerations, it is suggested that mixing of dense spatter and pumiceous lapilli tuff in the investigated deposit occurred during emplacement, not necessarily in the same vent, with the mixed fragmental material emplaced as a pyroclastic density current. Liquid water was not initially present but a steam phase was probably generated during transport and may represent water ingested during passage of the current as it passed over either wet ground, stream, shallow lake or (possibly) snow. Well-exposed caldera interiors are uncommon and that at Mason Spur is helping understand eruption dynamics associated with a complex large island volcano. The results of our study should help to elucidate interpretations of other, less well exposed, pyroclastic density current deposits elsewhere in Antarctica and globally.
CitationBulletin of Volcanology, 2017, 80 (13)
Author affiliation/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/School of Geography, Geology and the Environment
- AM (Accepted Manuscript)
Published inBulletin of Volcanology
NotesThe file associated with this record is under embargo until 12 months after publication, in accordance with the publisher's self-archiving policy. The full text may be available through the publisher links provided above.
Science & TechnologyPhysical SciencesGeosciences, MultidisciplinaryGeologyExplosive volcanismIgnimbriteLapilli tuffMcMurdo Volcanic GroupPyroclastic density currentTrachytic spatterMORNING ERUPTIVE CENTERSOUTHERN VICTORIA LANDLITHOSPHERIC MANTLECALDERA COLLAPSEIGNIMBRITEFRAGMENTATIONEMPLACEMENTDYNAMICSFLOWPETROGENESIS