Showing papers by "Colin J. N. Wilson published in 1998"
TL;DR: The Whakamaru group ignimbrites are widespread voluminous welded ignimrites which crop out along the eastern and western margins of the Taupo Volcanic Zone (TVZ), New Zealand as discussed by the authors.
109 citations
TL;DR: In this article, the authors developed a mathematical model which predicts the time required for a pumice clast to saturate is proportional to the square of its radius, which can be used to predict the timescales over which certain rapid post-eruptive sedimentary processes operate.
76 citations
TL;DR: In this article, a detailed componentry, density and petrology of lithic fragments from three ignimbrites (Rangatira Point, Oruanui, and Taupo) are used to reveal aspects of the sub-Taupo caldera geology, including the evolution of the Taupo volcanic centre, to assist in ignimbrite correlation and to evaluate structures within the Tauranga volcanic complex.
48 citations
TL;DR: Hybrid fall deposits in the Bishop Tuff show features common to both archetypal fall and surge deposits as discussed by the authors, and they are interpreted as fall material contemporaneously redeposited by strong (up to 40 m/s) swirling winds, comparable to firestorm whirlwinds, generated by air currents associated with coeval emplacement of pyroclastic flows.
Abstract: Hybrid fall deposits in the Bishop Tuff show features common to both archetypal fall and surge deposits. Like normal-fall deposits, they have an overall plane-parallel bedding and flat-lying pumice clasts but also, like surge deposits, they show variable development of cross-bedding, some crystal and pumice sorting, and some rounding of pumice clasts. All variations exist from normal-fall deposits, through streaky material with incipient development of cross-bedding, to the hybrid fall deposits with well-developed cross-bedding. The streaky and hybrid deposits are interpreted as fall material contemporaneously redeposited by strong (up to 40 m/s) swirling winds, comparable to firestorm whirlwinds, generated by air currents associated with coeval emplacement of pyroclastic flows. Recognition of hybrid fall deposits is important in interpreting the dynamics of explosive eruptions and correctly assessing volcanic hazards. However, although such deposits may be commonly produced by explosive eruptions, especially where pyroclastic flows accompany fall activity, they are likely to be overlooked, or wrongly interpreted as surge deposits or secondary, reworked material.
39 citations
TL;DR: The Mangakino Volcanic Centre is the westernmost and oldest rhyolitic caldera volcano in the Taupo Volcanics Zone, North Island, New Zealand.
Abstract: The Mangakino Volcanic Centre is the westernmost and oldest rhyolitic caldera volcano in the Taupo Volcanic Zone, North Island, New Zealand. The largest eruptions from Mangakino occurred in two periods of caldera‐forming activity during 1.68–1.53 Ma (Period I), and 1.21–0.95 Ma (Period IIA), producing several voluminous widespread welded and nonwelded ignimbrites and minor fall deposits. Other activity from Mangakino generated fall deposits and rhyolitic lava domes. Lithic fragments are common in all Mangakino ignimbrites (1–10 modal %), and consist of diverse lithologies including: rhyolite, dacite, andesite, and basaltic andesite lava, welded ignimbrite, tuff, volcanic breccia, biotite granite, granodiorite porphyry, siltstone, sandstone, greywacke, metagreywacke, metaconglomerate, biotite and hornblende‐biotite schist. Lithic populations in Period I ignimbrites are dominated by andesite lavas, suggesting that there was a pre‐existing andesite volcano in the Mangakino area, geochemically distin...
24 citations