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51.
Depositional processes of the Suwolbong tuff ring, Cheju Island (Korea) 总被引:11,自引:0,他引:11
The Suwolbong pyroclastic sequence in the western part of Cheju Island, Korea, comprises partly preserved rim beds of a Quaternary basaltic tuff ring whose vent lies about 1 km seaward of the present shoreline. The sequence consists of breccia, lapillistone, lapilli tuff and tuff. Eighteen sedimentary facies are established and organized into six lateral facies sequences (LFS) and seven vertical facies sequences (VFS). The LFS 1, 4 and 5 begin with massive lapilli tuff which transforms downcurrent into either planar-bedded (LFS 1), undulatory-bedded (LFS 4) or climbing dune-bedded (LFS 5) (lapilli) tuff units. They are representative of relatively ‘dry’ base surge whose particle concentration decreases downcurrent with a progressive increase in both tractional processes and sorting. The LFS 2 begins with disorganized and massive lapilli tuff and transforms into crudely stratified units downcurrent. It results from relatively ‘wet’ base surge in which sorting is poor due to the cohesion of damp ash. The LFS 3 comprises well-sorted lapilli tuff and stratified tuff further downcurrent, suggestive of deposition from combined fall and surge of relatively ‘dry’ hydroclastic eruption. All seven vertical facies sequences generally comprise two facies units of coarse-grained fines-depleted lapilli tuff and an overlying fine-grained tuff. These sequences are suggestive of deposition from base surge that consists of a turbulent head and a low-concentration tail. Depositional processes in the Suwolbong tuff ring were dominated by a relatively ‘dry’ base surge. The base surge comprises turbulent and high-concentration suspension near the vent whose deposits are generally unstratified due to the lack of tractional transport. As the base surge becomes diluted downcurrent through fallout of clasts and mixing of ambient air, it develops large-scale turbulent eddies and is segregated into coarse-grained bedload and overlying fine-grained suspension forming thinly stratified units. Further downcurrent, the base surge may be either cooled and deflated or pushed up into the air, depending on its temperature. The Suwolbong tuff ring comprises an overall wet-to-dry cycle with several dry-to-wet cycles in it, suggestive of overall decrease in abundance of external water and fluctuation in the rate of magma rise. 相似文献
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53.
EMILY YOUNG 《Geographical review》1999,89(3):364-390
ABSTRACT. It is increasingly clear that local participation in conservation endeavors is not only critical but also highly problematic. El VizcaÍno Biosphere Reserve in Baja California Sur, Mexico, is examined to study the difficulties involved in translating community-based conservation rhetoric into on-the-ground nature-protection efforts. This case illustrates how inhabitants of a reserve are marginalized by the very conservation process meant to engage them as key actors in promoting natural-resource protection. It also highlights recent attempts to enhance local participation in reserve endeavors through collaborative efforts among field staff, nongovernmental organizations, and area residents. 相似文献
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55.
VON C.C.YOUNG 《地质学报》1931,(1)
Ⅰ. VORBEMERKUNG. Die Ordnung Nagetiere umfasst sehr viele Arten und ist die verbreitetste Tiergruppe innerhalb der Saeugetiere. Sie macht mit ihren etwa 2800 Species mehr als ein Drittel der heutigen Landsaeugetiere aus. Die Nagetiere sind auf der ganzen Welt bis zu den Polen und dem vereisten Hochgebirge an- 相似文献
56.
PAUL A. WALKER MICHAEL D. YOUNG 《International journal of geographical information science》2013,27(7):619-632
The potential of geographical information systems for strategic policy analysis is examined and demonstrated by example. One of the necessary conditions for this potential to be realised is the development of integrated data sets that combine economic, production and physical data sets at similar scales. The paper illustrates this potential using examples from a State-wide Resource Information and Accounting System developed by CSIRO. 相似文献
57.
Abstract The helium concentrations have been measured in the groundwaters of the Sabarmati basin. Gujarat, and the Jaisalmer district, Rajasthan. The observed helium concentrations show localized anomalies. The magnitude of the excess helium is shown to be approximately inversely proportional to the square of the thickness of the sedimentary strata between the sampled aquifer and the Basement Trap surface in the Sabarmati basin. 相似文献
58.
RAYMOND M. RICE 《水文科学杂志》2013,58(3):315-321
59.
ANTHONY YOUNG 《The Geographical journal》2005,171(1):83-95
Attitudes to population policy taken by major international institutions display a lack of symmetry. Population-based institutions forcefully set out the effects of population on development and human welfare. In contrast, institutions and lobbies concerned with hunger, poverty and environment, brought together at the 2003 World Summit on Sustainable Development in Johannesburg, treat population growth as a given, independent, variable. This paper gives a land resources viewpoint. It includes a case study of Malawi and cross-country statistical comparisons. Official estimates of the extent of spare land, cultivable but not presently cultivated, are challenged. It is concluded that in low-income, food-deficit countries population increase has reduced, in some areas nullified, advances in agricultural development. Following the 1994 UN Conference on Population and Development in Cairo, a set of ethically acceptable measures for reducing population growth received general acceptance. All concerned with poverty, hunger and environment should follow the policy road from Cairo to Johannesburg. If greater efforts are not made to reduce rates of population increase, the targets of the Millennium declaration will not be met, and the suffering which these cause will continue. Statements about agriculture, food security, poverty and sustainability should recognize that population is not an external variable but an integral part of development. 相似文献
60.
正 In the past few years, a number of fossil footprint have been noticed by members of the National Geological Survey of China. At least in three localities 相似文献