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A south‐east Australian speleothem stable isotope record displaying an apparent cooling synchronous with the northern hemisphere Younger Dryas climate event (12.9–11.7 ka) has significantly influenced scientific thinking on the climatic response of the southern hemisphere following the Last Glacial Maximum. This is one of very few records displaying such a response, and yet the cooling was inferred from substantial extrapolation between just three uranium‐series ages. Technological advances since then have produced major improvements in both the spatial resolution and the accuracy of uranium‐series geochronologies. Re‐analysis of this sample has yielded ages of 7.96 ± 0.36 to 7.69 ± 0.33 ka for the interval previously inferred to span the Younger Dryas, and reveals a substantial hiatus in deposition from 6.93 ± 0.64 to 1.83 ± 0.16 ka. These data not only refute the original evidence for an inter‐hemispheric synchroneity of the Younger Dryas but also reject any evidence for neoglacial conditions at 3 ka. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Caroline A. Canham Clément Duvert Leah S. Beesley Michael M. Douglas Samantha A. Setterfield Fiona L. Freestone Steven Clohessy Robyn C. Loomes 《水文研究》2021,35(5):e14180
Riparian trees play a critical role in the ecological function of rivers, yet are threatened by anthropogenic change to the hydrological cycle. Identifying the sources of water used by riparian trees can inform sustainable water policy. We used isotopic analysis complemented by measurements of plant water relations to assess water sources for riparian trees at two sites with contrasting hydrogeological processes; one with an alluvial aquifer overlaying an aquitard, and one where fault-induced preferential pathways in the aquitard allowed the flow of deeper, older groundwater from a regional aquifer to the alluvium. At both sites, plant water potential, stomatal conductance, and plant water isotope composition in the xylem sap of riparian trees were collected from two landscape positions, the riverbank and floodplain. We used a Bayesian mixing model (MixSIAR) to assess differences in the proportion of water sources for sites and landscape positions. We found that xylem water isotope values differed between the two sites in line with their hydrogeological characteristics, with trees at the regional aquifer site using water sourced from the regional groundwater and trees at the site with only an alluvial aquifer present using a mixture of water sources, with no dominant source identified. Higher plant predawn water potential values at the regional site indicated greater water availability and support the inference that plants were using more groundwater at the regional site compared to the alluvial site. Trees closer to the river had higher isotope values, indicative of surficial water sources i.e. shallow soil water and river water. Our findings show that the water sources used by riparian trees reflect local hydrogeology and resource availability. Water managers should identify and protect plant water sources to ensure maintenance of riparian trees. 相似文献
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Microgeographies of Retailing and Gentrification 总被引:2,自引:0,他引:2
It has long been argued that gentrification is a process of consumption as well as production but, in the main, analyses of consumption and gentrification have only tangentially or anecdotally considered the retail spaces of gentrified neighbourhoods. In this paper we investigate the nature of the retail landscapes of gentrification, using empirical evidence from Sydney, Australia. We point to micro retailscapes that differ between gentrified neighbourhoods that suggest a divergence of consumption practices between different groups of gentrifiers. These consumption practices are considered both in terms of their relations to identity (through food and the conception of the body) and to the spaces of the city. The paper concludes by drawing out the implications for future research on the consumption practices of the new middle class and the working class in an international context . 相似文献
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Three upper Miocene calc-alkaline volcanic centers are spaced about 100 km apart in the northeast-trending transition zone between the Columbia Plateau and Basin and Range geologic provinces. These centers are transverse to contemporaneous andesitic vents of the western Cascades Sardine Formation. Some of the Miocene volcanic features in northeast Oregon resemble those of linear volcanic belts that are associated with subduction, but structural patterns do not support the existence of an upper Miocene subduction zone in northeast Oregon. Major east-trending fold axes and northwest-trending faults indicate that north-south compression and east-west extension were the dominant deformational events in this region. It is suggested that the origin of these calc-alkaline rocks is related to their particular tectonic setting and not to subduction. 相似文献
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Abstract: ‘Place matters’ in the production of knowledge. This article examines the production of feminist geographical knowledge at a particular place – the Department of Geography, Tourism and Environmental Planning at the University of Waikato. Feminist geography at Waikato represents a nexus of international, national, regional, and local politics. It represents the efforts, personalities, political and personal motivations of particular individuals, at particular times, in a particular space. While international trends are important, they can also mask the unfolding of events in different ways in ‘other’ places. 相似文献
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Heat Wave Hazards: An Overview of Heat Wave Impacts in Canada 总被引:1,自引:2,他引:1
Extreme heat events are natural hazards affecting Canada and many other regions of the world. This paper presents an overview of the issues involved in defining heat waves and harmful hot weather events, followed by a spatial and historical overview of heat waves across Canada, and an assessment of heat wave adaptation potential in selected cities. The Prairies, Southern Ontario, and areas in the St. Lawrence River Valley of both Ontario and Quebec demonstrate the highest temperatures and most frequent occurrences of heat waves, with minimal effects in the North, Pacific Coast, and Maritimes. Montreal frequently experiences extreme heat, and based on its low air conditioning rates and older, high-density housing, it demonstrates limited potential for adaptation to heat events. A scientific assessment was done to identify the effects of heat waves on various sectors of Canadian life including agriculture, livestock, fisheries, construction, transportation, utilities, the environment, and human health. Heat stress has been linked to excess human mortality and illness, violent behaviour, drought, forest fires, tornadoes, decreased agricultural and livestock productivity, construction and transportation difficulties, and reduced electrical power supply. Despite limited research on heat waves in Canada, this study demonstrates that the impacts of heat are profound and far-reaching. 相似文献