Toshimori Sekine  Thomas S. Duffy  Allan M. Rubin  William W. Anderson  Thomas J. Ahrens 《Geophysical Journal International》1995,120(2):247-261

  相似文献   

    

Yann Sonzogni  Georgiana Y. Kramer  Allan H. Treiman 《Meteoritics & planetary science》2016,51(1):31-55

Clast 100 in regolith breccia 15295 could be a key to resolving the relationship(s) between mare basalts and lunar picritic glasses. The clast is basaltic, with texture, mineralogy, mineral compositions, and calculated bulk composition suggesting that it crystallized in a thick lava flow or shallow intrusive body from a very‐low‐titanium (VLT) basaltic magma. The estimated bulk composition of clast 15295,100 is primitive (i.e., magnesian) compared to those of known VLT basalts, and is very close to those of VLT picritic green glasses, especially the Apollo 14 A green glass. From these similarities, we infer that clast 15295,100 is a crystalline product of a picritic magma similar to the Apollo 14 A glass. Clementine and M³ remotely sensed data of the lunar surface were used to find areas that have chemical compositions consistent with those of clast 15295,100, not only near the Apollo 15 site, but in a broad region surrounding the site. Two regions are consistent with clast's 15295,100 compositional data. The larger region is in southern Mare Imbrium, and a smaller region is in the eastern half of Sinus Aestuum. These locations should be considered as candidates for future missions focusing on sample science.  相似文献   

    

Peter Whetton  Robert Allan  Ian Rutherfurd 《Climatic change》1996,32(1):103-109

  相似文献   

    

M. Dominik †  N. J. Rattenbury  A. Allan  S. Mao  D. M. Bramich  M. J. Burgdorf  E. Kerins  Y. Tsapras  &#;. Wyrzykowski 《Monthly notices of the Royal Astronomical Society》2007,380(2):792-804

  相似文献   

    

Augusto César Coelho Dias da Silva  Jaqueline Comin de Castilhos  Erik Allan Pinheiro dos Santos  Luciana Sonnewend Brondízio  Leandro Bugoni 《Ocean & Coastal Management》2010,53(9):570-576

The neritic waters of the state of Sergipe in Northeastern Brazil is adjacent to the main nesting area of the olive ridley sea turtles (Lepidochelys olivacea) in the Western Atlantic Ocean and an important area for shrimp trawl fishery. To address the problem of incidental mortality of sea turtles captured during trawling and reduce the risk of overexploitation of shrimp stocks, Projeto TAMAR/ICMBio, a Brazilian sea turtle conservation program, has adopted two main strategies: (1) the implementation of a marine monitoring program and (2) active participation in local forums. This paper describes the conflicts among stakeholders, the arrangements and established mechanisms of negotiation aimed to protect sea turtles and shrimp grounds, and strategies to reduce conflicts between user groups. The analysis of this co-management process highlights the importance of stakeholder participation in resource management decision-making through a cooperative process, the role assumed by non-governmental organizations as mediators, and the factors that influence this system. The key factors and actions learnt from the current study include clear identification of the conflicts, identification of stakeholders – both local and external, and local leaders, encouragement of actors and leaders to participate, support and strengthening of local groups, legitimization of the discussion forums through involvement with government, formalization of decisions taken through legislation, and monitoring of the management efficacy.  相似文献   

    

J.A. Allan 《Geoforum》1983,14(3):243-247

The development of agriculture is recognised to be an essential preliminary and on-going element in the economic development strategies of most developing countries. The contribution of agricultural production to gross domestic product, food self-sufficiency and export income are amongst the major development goals exercising the governments of such countries. In addition, in many countries the agricultural sector is regarded as one with a potential for generating a surplus to sustain other economic activities and to have an important stabilising role in reducing the movement of population from rural areas. This article discusses renewable natural resources, soil and water, as the basis for agricultural development and especially of irrigated farming. A number of case studies will be referred to which illustrate the idea that many national governments attribute quite unreal qualities to soil and water resources. Once development schemes were launched appropriate rhetoric was mobilised to invest the reclamation of ‘virgin lands’ and ‘new lands’, with the character of ‘green revolutions’. These ventures have been sustained not because of their success but because the ‘fantasies’ have been circulated amongst ill-formed urban populations, remote from the arduous realities of land reclamation. Case studies in the Soviet Union and the Middle East are discussed.  相似文献   

    

Allan C. Ashworth  Donald P. Schwert  William A. Watts  H.E. Wright 《Quaternary Research》1981,16(1):66-79

The Norwood site in Sibley Co., Minnesota, contains 1.6 m of silt resting on till and overlain by peat. The base of the peat has been radiocarbon dated at 12,400 ± 60 and the top at 11,200 ± 250 yr B.P. The pollen, plant macrofossils, and insect remains in the basal silt consist of boreal species inhabiting open environments, but not tundra. No modern analogue exists for the insect assemblage, which includes elements of boreal forest, tundra-forest, and western affinities. The transition from an unstable open environment to a stable coniferous forest is reflected by both plant and insect fossils and is interpreted as a successional rather than a climatic event. During this time of significant biologic change, the climate is inferred to have been relatively uniform, with temperatures similar to those presently existing in the boreal forest south of the tundra-forest transition zone. The geologic and ecologic succession at Norwood is generally similar to that presently associated with ice stagnation of the Klutlan Glacier in the Yukon Territory. Localized successional sequences similar to those at Norwood are conceived to have occurred repeatedly during the melting of the Laurentide ice, and thus the proposed model has potentially broad application to the interpretation of late-glacial sequences.  相似文献   

    

Allan W. Stoner  Holly S. Greening  Joseph D. Ryan  Robert J. Livingston 《Estuaries and Coasts》1983,6(1):76-82

A comparison of shallow water benthic macrofauna collected with hand-held cores and a suction sampler shoed that the core method provided the best estimate of macrofaunal density and composition. In a bare sand habitat, suction methods collected 72.8% fewer individuals per unit surface area of sediment. The difference was 32.6% in a seagrass (Halodule wrightii) habitat. At each site the number of species collected with the two devices was similar; however, population densities of numerically important species were underestimated with the suction device resulting in effects on community statistics. In addition to high sampling efficiency and statistical advantages associated with the use of the multiple cores, ease of operation and low construction cost make simple core tubes the preferred gear for sampling small macrobenthos in soft sediments, with or without vegetation.  相似文献   

    

R.J. Allan   《Journal of Geochemical Exploration》1978,10(3):203-218

Regional geochemical maps of a 97,000-km² area of the northwestern Canadian Shield were based on analysis of lake sediment samples collected at 5-km grid points. The maps revealed three global-scale geochemical features: (1) a major anomaly of refractory and chalcophile elements associated with a Proterozoic volcanic-plutonic belt of previously proposed Andean are affinities; (2) a dramatic increase in Ba concentrations on crossing a proposed Precambrian suture zone; and (3) another major anomaly of refractory and chalcophile elements associated with the Archean greenstone belt closest to the supposed suture zone.The regional geochemical anomaly in the Proterozoic volcanic-plutonic belt is considered to have originated during an island-arc-type evolution of the belt by intrusion of magma formed by stages of partial melting of subducted oceanic basalts contaminated by subducted ocean floor sediments. The increase in Ba concentration found on crossing the proposed Precambrian suture is attributed to exposure of deep crust by the post-collision erosion of the uplifted edge of one of the proto-continents. The multielement, geochemical signature of the Archean greenstone belt is tentatively attributed to Archean subduction of oceanic crust and ocean sediments.The regional, multielement anomalies delineated are associated with known or suspected base metal and uranium mineralization. If the geotectonic relationships proposed above are valid, routine geochemical mapping of the Precambrian Canadian Shield will not only be of use in prospecting and mineral potential evaluation but may indirectly assist in metallogenic interpretations. Further, there is a possibility that routine geochemical mapping of the Canadian Shield may define other subduction and suture zones.  相似文献   

    

Allan D. Pierce  Joe W. Posey 《Geophysical Journal International》1971,26(1-4):341-368

  相似文献