3,192 research outputs found
Connecting and dating with tephras: principles, functioning, and application of tephrochronology in Quaternary research
Tephrochronology, the characterisation and use of volcanic-ash layers as a unique chronostratigraphic linking, synchronizing, and dating tool, has become a globally-practised discipline of immense practical value in a wide range of subjects including Quaternary stratigraphy, palaeoclimatology, palaeoecology, palaeolimnology, physical geography, geomorphology, volcanology, geochronology, archaeology, human evolution, anthropology, and human disease and medicine. The advent of systematic studies of cryptotephras â the identification, correlation, and dating of sparse, fine-grained glass-shard concentrations âhiddenâ within sediments or soils â over the past ~20 years has been revolutionary. New cryptotephra techniques developed in northwestern Europe and Scandinavia in particular and in North America most recently adapted or improved to help solve problems as they arose, have now been applied to sedimentary sequences (including ice) on all the continents. The result has been the extension of tephra isochrons over wide areas hundreds to several thousands of kilometres from source volcanoes. Taphonomic and other issues, such as quantifying uncertainties in correlation, provide scope for future work. Developments in dating and analytical methods have led to important advances in the application of tephrochronology in recent times. In particular: (i) the ITPFT (glass fission-track) method has enabled landscapes and sequences to be dated where previously no dates were obtainable or where dating was problematic; (ii) new EMPA protocols enabling narrow-beam analyses (<5 um) of glass shards, or small melt inclusions, have been developed, meaning that small (typically distal) glass shards or melt inclusions <~10 um in diameter can now be analysed more efficaciously than previously (and with reduced risk of accidentally including microlites in the analysis as could occur with wide-beam analyses); (iii) LA-ICPMS method for trace element analysis of individual shards <~10 um in diameter is generating more detailed âfingerprintsâ for enhancing tephra-correlation efficacy (Pearce et al., 2011, 2014; Pearce, 2014); and (iv) the revolutionary rise of Bayesian probability age modelling has helped to improve age frameworks for tephras of the late-glacial to Holocene period especially
Quaternary volcanism, tephras, and tephra-derived soils in New Zealand: an introductory review
This two-part article comprises brief introductions to (1) volcanism and its products in general and to the broad pattern of Quaternary volcanism and tephrostratigraphy in North Island, and (2) the ensuing tephra-derived soils of North Island. Part 1 derives mainly from Smith et al. (2006), Leonard et al. (2007), and Lowe (2008a). Other useful reviews include those of Neall (2001), Graham (2008: Chapter 7), Wilson et al. (2009), and Cole et al. (2010). Recent reviews on tephras include Shane (2000), Alloway et al. (2007), Lowe (2008b, 2011), and Lowe et al. (2008a, 2008b). A history of tephra studies in New Zealand was reported by Lowe (1990). Part 2 describes the distribution and character of the main tephra-derived soils, these being Entisols and Andisols (mostly Vitrands and Udands) and Ultisols (Lowe and Palmer, 2005). Books on these and other soils in New Zealand include NZ Soil Bureau (1968), Gibbs (1980), McLaren and Cameron (1996), Cornforth (1998), and Molloy and Christie (1998). An excellent overview is the web-based article by Hewitt (2008), and encyclopaedic reviews by Neall (2006) and McDaniel et al. (2011) include New Zealand examples. Tonkin (2007a, 2007b, 2007c) provided a history of soil survey and soil conservation activities in New Zealand. A quantitatively-based classification of New Zealandâs terrestrial environments was published by Leathwick et al. (2003)
Stratigraphy, age, composition, and correlation of late Quaternary tephras interbedded with organic sediments in Waikato lakes, North Island, New Zealand
Cores from 14 peaty lakes in the central Waikato region, northern North Island, contain a sequence of 41 well-preserved, mainly macroscopic, occasionally bedded, ash and lapilli layers ranging in thickness from c. 2 to 110 mm and interbedded with fine-grained organic lake sediment. The layers, whose field and compositional properties are described in detail, are distal airfall tephras that were erupted between c. 17000 and c. 1800 ÂčâŽC years ago from six rhyolitic and andesitic volcanic centres located c. 70-200 km from the Waikato sites: Taupo (5 tephras), Okataina (7), Maroa (1) (rhyolitic); Mayor Island (2) (peralkaline); Tongariro (11), and Egmont (15) (andesitic)
Measuring radiation in the environment following the Fukushima nuclear disaster, Japan
A group of scientists and technical staff from Toshiba Company, including Dr Hirokazu Kanai, undertook field trials at the station using a newly-developed, portable, two-dimensional gamma-ray visualization system known as a âGamma Cameraâ
Revision of the age and stratigraphic relationships of Hinemaiaia Tephra and Whakatane Ash, North Island, New Zealand, using distal occurrences in organic deposits
The stratigraphic and chronologic relationships of Hinemaiaia Tephra and Whakatane Ash are examined using distal tephras preserved in organic-rich deposits at five sites in eastern and northern North Island, New Zealand. A c. 10mm thick, unnamed white rhyolitic ash layer described at two of the sites (Tiniroto and Poukawa), and previously of disputed stratigraphic signillcance, also occurs at the other three sites (Kaipo, Rotomanuka, and Okoroire) as a primary airfall tephra. The tephra is derived from the Taupo Volcanic Centre and is correlated with Hinemaiaia Tephra (definition of Froggatt) using similarity of stratigraphic position, composition (ferromagnesian mineralogy and glass chemistry), and radiocarbon age. It stratigraphically overlies Whakatane Ash. The tephra underlying Whakatane Ash, and previously identified as Hinemaiaia Ash (definition of Vucetich & Pullar), is probably Motutere Tephra.
Hinemaiaia Tephra has a mean age of old (TÂœ) c. 4500 years, Whakatane Ash c. 4800 years. New ÂčâŽC dates, obtained on peat or gyttja adjacent to these tephras, are (old T1/2, years B.P.): 4220 ± 60 (NZ316OA), 4490 ± 70 (Wk541)( above Hinemaiaia Tephra); 4470 ± 70 (Wk542) (below Hinemaiaia Tephra); 4800 ± 50 (NZ3161A), 4490 ±60 (Wk496), 4530 ± 60 (Wk497), 4260 ± 140 (Wk662) (below Hinemaiaia Tephra and above Whakatane Ash); 5210 ± 80 (NZ3162A), 4860 ±70 (Wk501), 4850 ± 80 (Wk660) (below Whakatane Ash).
Based on the distal occurrences described here, the Hinemaiaia Tephra has a much more wide spread distribution than previously demonstrated, and may have been emplaced by a very powerful "above average" plinian eruption
INTREPID Tephra-II: - 1307F
The INTREPID Tephra project, âEnhancing tephrochronology as a global research tool through improved fingerprinting and correlation techniques and uncertainty modellingâ, was an overarching project of the international community of tephrochronologists of the International Focus Group on Tephrochronology and Volcanism (INTAV), which in turn lies under the auspices of INQUAâs Stratigraphy and Chronology Commission (SACCOM). INTREPIDâs main aim has been to advance our understanding and efficacy in fingerprinting, correlating, and dating techniques, and to evaluate and quantify uncertainty in tephrochronology, and thus enhance our ability to provide the best possible linking, dating and synchronising tool for a wide range of Quaternary research projects around the world. A second aim has been to re-build the global capability of tephrochronology for future research endeavours through mentoring and encouragement of emerging researchers in the discipline
Polynesian settlement of New Zealand and the impacts of volcanism on early Maori society: An update
Presents an overview of the timing of Polynesian settlement in New Zealand, discussing the application of tephrochronology and rat and avian bone dating to the problem. The impacts of volcanism on early Maori society are examined, including the catastrophic impacts of the Tarawera eruption of 1886
Pukekohe silt loam, Pukekohe Hill
Pukekohe Hill is an excellent starting point for the tour in various ways: it provides a commanding view of important market gardens developed within Ultisols, and associated landuse issues, and the Massey Memorial on the hilltop commemorates Irish-born, South Auckland identity William (âBig Billâ) Fergusson Massey (1865-1925), Prime Minister of New Zealand 1912-1925, after whom Massey University is named. Pukekohe town has a population of about 23,000
Connecting with tephras: principles, functioning, and applications of tephrochronology in Quaternary science
Tephrochronology is a unique method for linking and dating geological, palaeoecological, palaeoclimatic, or archaeological sequences or events. The method relies firstly on stratigraphy and the law of superposition, which apply in any study that connects or correlates deposits from one place to another. Secondly, it relies on characterising and hence identifying or âfingerprintingâ tephra layers using either physical properties evident in the field or those obtained from laboratory analysis, including mineralogical examination by optical microscopy or geochemical analysis of glass shards or crystals (e.g., Fe-Ti oxides, ferromagnesian minerals) using the electron microprobe and other tools. Thirdly, the method is enhanced when a numerical age is obtained for a tephra layer by (1) radiometric methods such as radiocarbon, fission-track, U-series, or Ar/Ar dating, (2) incremental dating methods including dendrochronology or varved sediments or layering in ice cores, or (3) age-equivalent methods such as palaeomagnetism or correlation with marine oxygen isotope stages or palynostratigraphy. Once known, that age can be transferred from one site to the next using stratigraphic methods and by matching compositional characteristics, i.e., comparing âfingerprintsâ from each layer. Used this way, tephrochronology is an age-equivalent dating method
Project 0907: INTREPID â Enhancing tephrochronology as a global research tool through improved fingerprinting and correlation techniques and uncertainty modelling
In May, 2010, the inter-congress meeting of the INQUA International focus group on tephrochronology and volcanism (INTAV) was held in Kirishima City, southern
Kyushu, Japan. INTAV was formed in 2007 at the International Union for Quaternary Research (INQUA) congress held in Cairns. It replaced SCOTAV (Sub-commission on tephrochronology and volcanism), COT (Commission on tephrochronology), and earlier tephrarelated research groups dating back to the 1960s. Previous meetings of the group in the past two decades were held in the Yukon Territory, Canada (2005), France (1998), New Zealand (1994), and USA (1990). The venue for the 2010 meeting was the main hall of the Kokobu Civic Centre in Kirishima City, which was very generously provided free of charge by the Kirishima authorities in return partly for the delivery of two public lectures, one by David Lowe (âConnecting with our past: using tephras and archaeology to date the Polynesian settlement of Aotearoa/New Zealandâ) and the other by Hiroshi Machida (âWidespread tephras originating from Kagoshima occurring in northeast Asia and adjacent seasâ), on Sunday 9 May. Participants were treated to a personal welcome by the Mayor of Kirishima City, Shuji Maeda, followed by what appeared to be a very special (and delicious) banquet. However, this spread turned out to be standard lunch and dinner fare provided by the centreâs cafeteria and was enjoyed by participants throughout the meeting
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