First cosmogenic 10Be age constraint on the timing of Younger Dryas glaciation and ice cap thickness,western Scottish Highlands     

Nicholas R. Golledge  Derek Fabel  Jeremy D. Everest  Stewart Freeman  Steven Binnie 《第四纪科学杂志》2007,22(8):785-791

We use cosmogenic ¹⁰Be surface exposure age techniques at a locality close to Rannoch Moor, western Scottish Highlands, in order to establish the age and chronology of its most recent glaciation. Glacial erratics and an in situ bedrock quartz vein sampled from this site—the summit of Beinn Inverveigh—have yielded zero‐erosion exposure ages of 12.9 ± 1.5 ka to 11.6 ± 1.0 ka, implying complete ice cover of the mountain during the Younger Dryas, or Loch Lomond Stadial. These results fit closely with published ¹⁴C dates that bracket the maximum (lateral) extent of ice cap outlet glaciers, and are the first internally consistent ages to specifically address this period of glaciation in Scotland. Furthermore, the dates imply that previous palaeoglaciological reconstructions for this area may have underestimated both the thickness of the former ice cap and, by implication, its volume. © British Geological Survey/Natural Environment Research Council copyright 2007. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd.  相似文献   

Evaporation effects on the formation of martian gullies     

Kathryn L. Bryson  Derek W.G. Sears 《Icarus》2010,210(1):72-82

In order to investigate the formation of martian gullies and the stability of fluids on Mars, we examined about 120 gully images. Twelve HiRISE images contained a sufficient number of Transverse Aeolian Ridges (TARs) associated with the gullies to make the following measurements: overall gully length, length of the alcove, channel and apron, and we also measured the frequency of nearby TARs. Six of the 12 images examined showed a statistically significant negative correlation between overall gully length (alcove, channel and apron length) and TAR frequency. Previous experimental work from our group has shown that at temperatures below ∼200 K, evaporation rate increases by about an order of magnitude as wind speed increases from 0 to ∼15 m/s. Thus the negative correlations we observe between gully length and dune frequency can be explained by formation at temperatures below ∼200 K where wind speed/evaporation is a factor governing gully length. In these cases evaporation of the fluid carving the gully was a constraint on their dimensions. Cases where there is no correlation between gully length and TAR frequency, can be explained by formation at temperatures >200 K. The temperatures are consistent with Global Circulation Model and Thermal Emission Spectrometer (TES) data for these latitudes. The temperatures suggested by these trends are consistent with the fluid responsible for gully formation being a strong brine, such as Fe₂(SO₄)₃ which has a eutectic temperature of ∼200 K. We also find that formation timescales for gullies are 10⁵-10⁶ years.  相似文献   

Observed and modelled tidal currents in the New Zealand region     

Basil R. Stanton  Derek G. Goring  Robert G. Bell 《新西兰海洋与淡水研究杂志》2013,47(2):397-415

Tidal currents derived from current meter measurements are compared with the output from a barotropic tidal model of the New Zealand region. For the semi‐diurnal constituents there was very good agreement for the M₂ tide and good agreement for the S₂ tide. For the diurnal constituents (K_l, O_l) it was found that as the amplitude of the constituents decreased so did both the model/observation agreement and the accuracy of the observed tidal ellipse parameters. Consequently it was not possible to decide whether differences arose through shortcomings in the model or in the data. However, the overall performance of the model as a prognostic tool for ocean tidal current simulation appears to be good.  相似文献   

El Niño and decadal effects on sea‐level variability in northern New Zealand: A wavelet analysis     

Derek G. Goring  Robert G. Bell 《新西兰海洋与淡水研究杂志》2013,47(4):587-598

Sea‐level data from two sites in northern New Zealand, along with the Southern Oscillation Index (SOI), are analysed for interannual and decadal variability using wavelets. The analysis shows, using statistically significant wavelet power, there is a significant relationship between mean sea level (MSL) and SOI. However, the relationship is highly variable, both in magnitude and in the range of time‐scales over which it occurs. This non‐stationarity necessitates the use of techniques such as wavelets for analysis. An interdecadal response in MSL around northern New Zealand has been isolated, with shifts occurring in 1950 and the late 1970s. This behaviour in MSL appears to coincide with shifts in the Pacific Decadal Oscillation, thought previously to be largely centred in the North Pacific. A strong correlation between SOI and sea surface temperature (SST) is also demonstrated. This relationship appears to be stable in magnitude (a large change in SOI produces a large change in SST) and to occur over the same range of time‐scales. More SST and MSL data are required for other parts of New Zealand to determine whether these findings apply elsewhere.  相似文献   

Food with a visible face: Traceability and the public promotion of private governance in the Japanese food system   总被引：1，自引：0，他引：1  

Derek Hall 《Geoforum》2010,41(5):826-835

The years since 2000 have seen a constant stream of high-profile scandals relating to food safety and food labeling in Japan. One response of Japan’s Ministry of Agriculture, Forestry and Fisheries (MAFF) has been to promote food traceability as a mechanism to improve food safety and to provide reliable information to consumers about their food. MAFF’s main approach to traceability promotion, however, has not involved making traceability mandatory (as has been done in the EU) but encouraging private companies to adopt it. These actions constitute, I argue, an example of the public promotion of private governance. When viewed against the literature on the private governance of food safety and quality, MAFF’s traceability activities are surprising for three reasons: their forms and extent, the relative lack of interest the Ministry has shown in third-party certification, and the way MAFF has responded to concerns about the safety of imported food by focusing almost entirely on domestic traceability. I also argue, however, that looking at the literature from a Japanese perspective suggests that public encouragement is more central to the rise of private governance in the global agri-food system than is usually appreciated.  相似文献   

Multi-zone fusion crust formation and classification of the 2004 Auckland meteorite (L6, S5, and W0)     

James M. Scott  Marianne Negrini  Kevin Faure  Marshall C. Palmer  Derek R. Knaack  Matthew I. Leybourne 《Meteoritics & planetary science》2023,58(3):328-340

On June 12, 2004, a meteorite passed through Earth's atmosphere and landed under the television in the living room of a house in Auckland, New Zealand. Textural characteristics, the chemistry of olivine (Fa_23–24) and orthopyroxene (Fs_20.7), and the bulk rock triple oxygen isotopes (δ¹⁷O + 3.1; δ¹⁸O + 4.2‰) from the interior of the completely unweathered (W0) 1.3 kg meteorite, hereafter referred to as Auckland, suggest it to be a strongly metamorphosed fragment from the interior of a low iron ordinary chondrite (L6) parent asteroid. The occurrence of maskelynite but shock fracturing of olivine and pyroxene indicates Auckland experienced extreme shock metamorphism (S5), likely during Ordovician fragmentation of the asteroid parent. The fusion crust consists of three zones: (1) an innermost zone containing narrow Fe-Ni-S-bearing veins that migrated along pre-existing shock fractures in olivine and pyroxene; (2) a middle zone in which the meteorite partially melted to form a silicate glass and immiscible blebs of metal and troilite, and is accompanied by unmelted silicate minerals; and (3) an approximately 0.1 mm wide vesicular-rich outermost layer that largely melted, volatilizing sulfides, before quenching to form glass and olivine. Oxygen isotope values of the bulk rock and/or maskelynite of melted rim and modified substrate are 2–3‰ greater than the meteorite interior and indicate that up to 19% of terrestrial atmospheric O₂ was incorporated into the fusion crust during the formation. The fusion crust migrated inwards as ablation occurred, enabling melting, migration, and re-precipitation ± loss of sulfide and metal components, with the prominent glassy rim therefore forming from an already chemically modified zone.  相似文献   

Oral histories in meteoritics and planetary science—XXV: Vagn F. Buchwald     

Derek W. G. Sears 《Meteoritics & planetary science》2014,49(7):1271-1287

Vagn Buchwald (Fig.  1 ) was born in Copenhagen where he attended school and college. Then after 18 months of military service, he assumed a position at the Technical University of Copenhagen. A few years later, he was presented with a piece of the Cape York meteorite, which led to an interest in iron meteorites. Through a campaign of informed searching, Vagn found the 20 ton Agpalilik meteorite (part of the Cape York shower) on 31st July 1963 and by September 1967 had arranged its transport to Copenhagen. After sorting and describing the Danish collection, which included application of the Fe‐Ni‐P phase diagram to iron meteorite mineralogy, Vagn was invited to sort and describe other iron meteorite collections. This led to a 7 yr project to write his monumental Handbook of Iron Meteorites. Vagn spent 3 yr in the United States and visited most of the world's museums, the visit to Berlin being especially important since the war had left their iron meteorites in bad condition and without labels. During a further decade or more of iron meteorite research, he documented natural and anthropomorphic alterations experienced by iron meteorites, discovered five new minerals (roaldite, carlsbergite, akaganeite, hibbingite, and arupite); had a mineral (buchwaldite, NaCaPO₄) and asteroid (3209 Buchwald 1982 BL1) named after him; and led expeditions to Chile, Namibia, and South Africa in search of iron meteorites and information on them. Vagn then turned his attention to archeological metal artifacts. This work resulted in many papers and culminated in two major books on the subject published in 2005 and 2008, after his retirement in 1998. Vagn Buchwald has received numerous Scandinavian awards and honors, and served as president of the Meteoritical Society in 1981–1982.  相似文献   

Ice caps existed throughout the Lateglacial Interstadial in northern Scotland     

Tom Bradwell  Derek Fabel  Martyn Stoker  Hannah Mathers  Lanny McHargue  John Howe 《第四纪科学杂志》2008,23(5):401-407

We constrain, in detail, fluctuations of two former ice caps in NW Scotland with multibeam seabed surveys, geomorphological mapping and cosmogenic ¹⁰Be isotope analyses. We map a continuous sequence of 40 recessional moraines stretching from ～10 km offshore to the Wester Ross mountains. Surface‐exposure ages from boulders on moraine ridges in Assynt and the Summer Isles region show that substantial, dynamic, ice caps existed in NW Scotland between 13 and 14 ka BP. We interpret this as strong evidence that large active glaciers probably survived throughout the Lateglacial Interstadial, and that during the Older Dryas period (ca. 14 ka BP) ice caps in NW Scotland were thicker and considerably more extensive than in the subsequent Younger Dryas Stadial. By inference, we suggest that Lateglacial ice‐cap oscillations in Scotland reflect the complex interplay between changing temperature and precipitation regimes during this climatically unstable period (ca. 15–11 ka BP). © Natural Environment Research Council (NERC) copyright 2008. Reproduced with the permission of NERC. Published by John Wiley & Sons, Ltd.  相似文献   

Livelihoods and co-management in the Tam Giang lagoon,Vietnam     

Truong Van Tuyen  Derek Armitage  Melissa Marschke 《Ocean & Coastal Management》2010,53(7):327-335

The Tam Giang – Cau Hai lagoon is a microcosm of the complex social-ecological challenges experienced in similar systems throughout Southeast Asia. Intensification and rapid change in livelihood strategies (production and gear type) have increased conflict and placed a significant strain on aquatic resources in the lagoon. Such changes are compounded by near-shore agricultural development and urbanization. In the long-term, resolving livelihood conflicts and sustaining ecosystems will require a shift in the planning and management model from one that is top-down and enforcement driven, to one involving greater decision making and management authority at the local level. Drawing on experiences with a long-term action research process in the lagoon, this paper examines the challenges and opportunities of implementing a co-management approach. Of particular focus is the growing recognition among authorities of the value of engaging local fishers and fish farmers in participatory process to resolve complex livelihood challenges, and the development of local management bodies (newly formed Fishing Associations) as a basis for emerging co-management of aquatic resources.  相似文献   

ANNOUNCEMENT     

Derek W. G. Sears 《Meteoritics & planetary science》1991,26(3):264-264

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