Double trouble: Paired ignimbrite eruptions and collateral subsidence in the Taupo Volcanic Zone, New Zealand

Abstract

Research Article| January 01, 2007 Double trouble: Paired ignimbrite eruptions and collateral subsidence in the Taupo Volcanic Zone, New Zealand D.M. Gravley; D.M. Gravley 1Geology Department, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand Search for other works by this author on: GSW Google Scholar C.J.N. Wilson; C.J.N. Wilson 1Geology Department, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand Search for other works by this author on: GSW Google Scholar G.S. Leonard; G.S. Leonard 2GNS Science, P.O. Box 30368, Lower Hutt 5040, New Zealand Search for other works by this author on: GSW Google Scholar J.W. Cole J.W. Cole 3Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand Search for other works by this author on: GSW Google Scholar Author and Article Information D.M. Gravley 1Geology Department, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand C.J.N. Wilson 1Geology Department, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand G.S. Leonard 2GNS Science, P.O. Box 30368, Lower Hutt 5040, New Zealand J.W. Cole 3Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand Publisher: Geological Society of America Received: 01 Nov 2005 Revision Received: 24 May 2006 Accepted: 17 Jul 2006 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 GEOLOGICAL SOCIETY OF AMERICA GSA Bulletin (2007) 119 (1-2): 18–30. https://doi.org/10.1130/B25924.1 Article history Received: 01 Nov 2005 Revision Received: 24 May 2006 Accepted: 17 Jul 2006 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation D.M. Gravley, C.J.N. Wilson, G.S. Leonard, J.W. Cole; Double trouble: Paired ignimbrite eruptions and collateral subsidence in the Taupo Volcanic Zone, New Zealand. GSA Bulletin 2007;; 119 (1-2): 18–30. doi: https://doi.org/10.1130/B25924.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Large explosive eruptions are generally rare, random events in the history of any particular volcano, volcanic area, or worldwide. In the Taupo Volcanic Zone, New Zealand, temporal clustering of eruptions occurs on a <1 yr to ∼300 k.y. basis, which implies that some controls lead to nonrandom eruption timing. We describe two closely paired large Taupo Volcanic Zone eruptions dated at ca. 240 ka that terminated a large-scale cluster of 7 caldera-forming and >15 smaller eruptions over a total ∼100 k.y. period. After a precursor eruption from a nearby source (and a break of years to decades), these paired eruptions in turn generated a wet ash-fall deposit and a dry pumice-fall deposit; the Mamaku ignimbrite (>145 km3 magma); a fine-grained vitric ash-fall deposit; then the Ohakuri ignimbrite (>100 km3 magma). Rotorua and Ohakuri, spaced ∼30 km apart, are the inferred collapse calderas associated with the Mamaku and Ohakuri ignimbrites, respectively. The early wet and dry fall deposits came from southerly sources, close to or within the subsequent Ohakuri caldera, while the fine-grained vitric ash is inferred to represent a co-ignimbrite ash from the Mamaku ignimbrite. At its southwest margin, the Mamaku ignimbrite overlies, but is also intercalated within and then overlain by, the pumice fall deposit, demonstrating that at least two widely spaced vents were active simultaneously for part of the eruption sequence. The post-Mamaku vitric ash-fall deposit underwent only trivial reworking prior to emplacement of the Ohakuri ignimbrite. This and other field evidence imply continuity, or time gaps of only days to months, in the whole paired sequence. Syneruptive volcanotectonic faulting may have permitted accumulation of >400 m of nonwelded Ohakuri ignimbrite through graben subsidence. Posteruptive faulting within years to decades of the eruption produced an ∼300 m extra-caldera offset of the Mamaku ignimbrite and collateral subsidence of a >40 km2 area immediately south of Rotorua caldera. Temporal linkages between ignimbrite eruptions and graben subsidence, the NNE-SSW alignment of associated faulting between the Rotorua and Ohakuri calderas, and the eruption-related subsidence indicate a tectonic control on volcanism associated with Taupo Volcanic Zone rifting processes. Statistical forecasts of the frequency of large-volume explosive events based on averages may be inaccurate because of tectonic triggering effects. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.