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Grain-size distribution of volcaniclastic rocks 2: characterizing grain size and hydraulic sorting


Jutzeler, M and McPhie, J and Allen, SR and Proussevitch, AA, Grain-size distribution of volcaniclastic rocks 2: characterizing grain size and hydraulic sorting, Journal of Volcanology and Geothermal Research, 301 pp. 191-203. ISSN 0377-0273 (2015) [Refereed Article]

Copyright Statement

Copyright 2015 Elsevier B.V.

DOI: doi:10.1016/j.jvolgeores.2015.05.019


Quantification of the grain size distribution of sediments allows interpretation of processes of transport and deposition. Jutzeler et al. (2012) developed a technique to determine grain size distribution of consolidated clastic rocks using functional stereology, allowing direct comparison between unconsolidated sediments and rocks. Here, we develop this technique to characterize hydraulic sorting and infer transport and deposition processes. We compare computed grain size and sorting of volcaniclastic rocks with field-based characteristics of volcaniclastic facies for which transport and depositional mechanisms have been inferred. We studied pumice-rich, subaqueous facies of volcaniclastic rocks from the Oligocene Ohanapecosh Formation (Ancestral Cascades, Washington, USA), Pliocene Dogashima Formation (Izu Peninsula, Honshu, Japan), Miocene Manukau Subgroup (Northland, New Zealand) and the Quaternary Sierra La Primavera caldera (Jalisco State, Mexico). These sequences differ in bed thickness, grading and abundance of matrix. We propose to evaluate grain size and sorting of volcaniclastic deposits by values of their modes, matrix proportion (< 2 mm; F-1) and D16, instead of median diameter (D50) and standard deviation parameters. F-1 and D16 can be uniformly used to characterize and compare sieving and functional stereology data. Volcaniclastic deposits typically consist of mixtures of particles that vary greatly in density and porosity. Hydraulic sorting ratios can be used to test whether mixed clast populations of pumice and dense clasts are hydraulically sorted with each other, considering various types of transport underwater. Evaluation of this ratio for our samples shows that most studied volcaniclastic facies are deposited by settling from density currents, and that basal dense clast breccias are emplaced by shear rolling. These hydraulic sorting ratios can be applied to any type of clastic rocks, and indifferently on consolidated and unconsolidated samples.

Item Details

Item Type:Refereed Article
Keywords:pyroclastic, grain size, stereology, Ohanapecosh
Research Division:Earth Sciences
Research Group:Geology
Research Field:Volcanology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Jutzeler, M (Dr Martin Jutzeler)
UTAS Author:McPhie, J (Professor Jocelyn McPhie)
UTAS Author:Allen, SR (Dr Sharon Allen)
ID Code:105878
Year Published:2015
Funding Support:Australian Research Council (CE0561595)
Web of Science® Times Cited:8
Deposited By:IMAS Research and Education Centre
Deposited On:2016-01-18
Last Modified:2017-10-30

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