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71.
Susan L. Donoghue Alan S. Palmer Elizabeth McClelland Kate Hobson Robert B. Stewart Vincent E. Neall Jèrôme Lecointre Richard Price 《Bulletin of Volcanology》1999,61(4):223-240
The ca. 10,500 years B.P. eruptions at Ruapehu volcano deposited 0.2–0.3 km3 of tephra on the flanks of Ruapehu and the surrounding ring plain and generated the only known pyroclastic flows from this
volcano in the late Quaternary. Evidence of the eruptions is recorded in the stratigraphy of the volcanic ring plain and cone,
where pyroclastic flow deposits and several lithologically similar tephra deposits are identified. These deposits are grouped
into the newly defined Taurewa Formation and two members, Okupata Member (tephra-fall deposits) and Pourahu Member (pyroclastic
flow deposits). These eruptions identify a brief (<ca. 2000-year) but explosive period of volcanism at Ruapehu, which we define
as the Taurewa Eruptive Episode. This Episode represents the largest event within Ruapehu's ca. 22,500-year eruptive history
and also marks its culmination in activity ca. 10,000 years B.P. Following this episode, Ruapehu volcano entered a ca. 8000-year
period of relative quiescence. We propose that the episode began with the eruption of small-volume pyroclastic flows triggered
by a magma-mingling event. Flows from this event travelled down valleys east and west of Ruapehu onto the upper volcanic ring
plain, where their distal remnants are preserved. The genesis of these deposits is inferred from the remanent magnetisation
of pumice and lithic clasts. We envisage contemporaneous eruption and emplacement of distal pumice-rich tephras and proximal
welded tuff deposits. The potential for generation of pyroclastic flows during plinian eruptions at Ruapehu has not been previously
considered in hazard assessments at this volcano. Recognition of these events in the volcanological record is thus an important
new factor in future risk assessments and mitigation of volcanic risk at Tongariro Volcanic Centre.
Received: 5 July 1998 / Accepted: 12 March 1999 相似文献
72.
Lewis J. Alcott Alexander J. Krause Emma U. Hammarlund Christian J. Bjerrum Florian Scholz Yijun Xiong Andrew J. Hobson Lesley Neve Benjamin J. W. Mills Christian Mrz Bernhard Schnetger Andrey Bekker Simon W. Poulton 《Geostandards and Geoanalytical Research》2020,44(3):581-591
The development and application of geochemical techniques to identify redox conditions in modern and ancient aquatic environments has intensified over recent years. Iron (Fe) speciation has emerged as one of the most widely used procedures to distinguish different redox regimes in both the water column and sediments, and is the main technique used to identify oxic, ferruginous (anoxic, Fe(II) containing) and euxinic (anoxic, sulfidic) water column conditions. However, an international sediment reference material has never been developed. This has led to concern over the consistency of results published by the many laboratories that now utilise the technique. Here, we report an interlaboratory comparison of four Fe speciation reference materials for palaeoredox analysis, which span a range of compositions and reflect deposition under different redox conditions. We provide an update of extraction techniques used in Fe speciation and assess the effects of both test portion mass, and the use of different analytical procedures, on the quantification of different Fe fractions in sedimentary rocks. While atomic absorption spectroscopy and inductively coupled plasma‐optical emission spectrometry produced comparable Fe measurements for all extraction stages, the use of ferrozine consistently underestimated Fe in the extraction step targeting mixed ferrous–ferric minerals such as magnetite. We therefore suggest that the use of ferrozine is discontinued for this Fe pool. Finally, we report the combined data of four independent Fe speciation laboratories to characterise the Fe speciation composition of the reference materials. These reference materials are available to the community to provide an essential validation of in‐house Fe speciation measurements. 相似文献
73.
Evidence for herbivorous cave bears (Ursus spelaeus) in Goyet Cave,Belgium: implications for palaeodietary reconstruction of fossil bears using amino acid δ15N approaches 
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75.
J. D. McEwen M. P. Hobson A. N. Lasenby D. J. Mortlock 《Monthly notices of the Royal Astronomical Society》2006,369(4):1858-1868
Many of the current anomalies reported in the WMAP text ( WMAP ) one-year data disappear after 'correcting' for the best-fitting embedded Bianchi type VII h component, albeit assuming no dark energy component. We investigate the effect of this Bianchi correction on the detections of non-Gaussianity in the WMAP data that we previously made using directional spherical wavelets. We confirm that the deviations from Gaussianity in the kurtosis of spherical Mexican hat wavelet coefficients are eliminated once the data are corrected for the Bianchi component, as previously discovered by Jaffe et al. This is due to the reduction of the cold spot at Galactic coordinates ( l , b ) = (209°, −57°) , which Cruz et al. claimed to be the sole source of non-Gaussianity introduced in the kurtosis. Our previous detections of non-Gaussianity observed in the skewness of spherical wavelet coefficients are not reduced by the Bianchi correction. Indeed, the most significant detection of non-Gaussianity made with the spherical real Morlet wavelet at a significant level of 98.4 per cent remains (using a very conservative method to estimate the significance). Furthermore, we perform preliminary tests to determine if foregrounds or systematics are the source of this non-Gaussian signal, concluding that it is unlikely that these factors are responsible. We make our code to simulate Bianchi-induced temperature fluctuations publicly available. 相似文献
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77.
Paul F. Scott Pedro Carreira Kieran Cleary Rod D. Davies Richard J. Davis Clive Dickinson Keith Grainge Carlos M. Gutiérrez Michael P. Hobson Michael E. Jones Rüdiger Kneissl Anthony Lasenby Klaus Maisinger Guy G. Pooley Rafael Rebolo José Alberto Rubiño-Martin † Pedro J. Sosa Molina Ben Rusholme ‡ Richard D. E. Saunders Richard Savage An&#;e Slosar Angela C. Taylor David Titterington Elizabeth Waldram Robert A. Watson § Althea Wilkinson 《Monthly notices of the Royal Astronomical Society》2003,341(4):1076-1083
78.
Maximum-entropy image reconstruction using wavelets 总被引：1，自引：0，他引：1
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80.
We investigate the power of wavelets in detecting non-Gaussianity in the cosmic microwave background (CMB). We use a wavelet-based method on small simulated patches of the sky to discriminate between a pure inflationary model and inflationary models that also contain a contribution from cosmic strings. We show the importance of the choice of a good test statistic in order to optimize the discriminating power of the wavelet technique. In particular, we construct the Fisher discriminant function, which combines all the information available in the different wavelet scales. We also compare the performance of different decomposition schemes and wavelet bases. For our case, we find that the Mallat and a ` trous algorithms are superior to the 2D-tensor wavelets. Using this technique, the inflationary and strings models are clearly distinguished even in the presence of a superposed Gaussian component with twice the rms amplitude of the original cosmic string map. 相似文献