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1.
The only reported occurrence of quartz-rich sands in Jamaica is on the plains of Black River, St Elizabeth, where they outcrop in isolated pockets. The sands overlie limestones of the White Limestone Supergroup and the Coastal Group, and partly underlie Holocene peat deposits. Monocrystalline quartz, containing fluid and mineral inclusions, is the dominant mineral of the sands, with the heavy minerals. magnetite, haematite, epidote, rutile, anatase, zircon and tourmaline, occurring in minor amounts. Grain surface texture studies of the quartz grains have identified a series of mechanical and chemical features. Microtextures depicting marine, aeolian and pedological environments have been retained on the grains and represent the last three stages in the history of the grains. The petrography of the sands indicates an igneous provenance, with the major source of the detrital minerals being the Cretaceous granitoids that outcrop in the eastern half of the island. These rocks were unroofed during the uplift of Jamaica in the Late Tertiary and were subjected to extensive chemical weathering, which accounted for the breakdown of the majority of their primary silicate minerals. Fluvial transportation and deposition of detritus onto the shelf of the south coast commenced during this period and continued into the Pleistocene, providing terrigenous sand that was modified along the coast to quartz arenite by moderate to high energy marine conditions. Tidal currents, east-west longshore currents and weathering contributed to the maturity of the sand by the time it had been transported along the shelf to the vicinity of Black River. During low sea level stands in the Pleistocene, some of this sediment that became trapped on the shelf was blown inland by south-east winds.  相似文献   
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Abstract: Landslide research at the British Geological Survey (BGS) is carried out through a number of activities, including surveying, database development and real-time monitoring of landslides. Landslide mapping across the UK has been carried out since BGS started geological mapping in 1835. Today, BGS geologists use a combination of remote sensing and ground-based investigations to survey landslides. The development of waterproof tablet computers (BGS·SIGMAmobile), with inbuilt GPS and GIS for field data capture provides an accurate and rapid mapping methodology for field surveys. Regional and national mapping of landslides is carried out in conjunction with site-specific monitoring, using terrestrial LiDAR and differential GPS technologies, which BGS has successfully developed for this application. In addition to surface monitoring, BGS is currently developing geophysical ground-imaging systems for landslide monitoring, which provide real-time information on subsurface changes prior to failure events. BGS’s mapping and monitoring activities directly feed into the BGS National Landslide Database, the most extensive source of information on landslides in Great Britain. It currently holds over 14?000 records of landslide events. By combining BGS’s corporate datasets with expert knowledge, BGS has developed a landslide hazard assessment tool, GeoSure, which provides information on the relative landslide hazard susceptibility at national scale.  相似文献   
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Many environmental science research programmes now adopt community-based philosophies and designs, although there are few applications in Australian Indigenous communities. This research describes the development and testing of a framework of engagement to guide collaboration between Indigenous and non-Indigenous Australians during an environmental sciences research project. That project aimed to assess trepang (sea cucumber) stocks in Aboriginal waters, and determine the commercial harvest potential of the resource to local people. Its objectives were to undertake trepang survey and mapping, integrate Indigenous knowledge about the resource, and model the existing catch data of commercial fishers operating in the region. The framework of engagement developed to guide the research process comprised a goal, research stages, and a number of guiding principles for collaboration, which were constructed from content analysis of available guidelines and literature and from data gathered during expert interviews. Further data were gathered using participant observation, while implementing the trepang research in accordance with this framework of engagement, and these data were analysed to test and evaluate the framework. Findings indicate discursive and reflective approaches such as action research or adaptive management may better facilitate equitable research partnerships for sustainable development.  相似文献   
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ABSTRACT. This article contributes to a recent and growing body of literature exploring the nature of fieldwork in human geography. Specifically, we critically examine the role of gatekeepers in providing access to “the field,” based on existing conceptualizations of gatekeepers in the literature and on our own experiences with gatekeepers. We argue that the concept of gatekeepers has been oversimplified, in that relationships between researchers and gatekeepers are often assumed to be unidirectional—with gatekeepers controlling or providing access by researchers—and predominantly static in form and time. Although we accept the necessity and advantages of working through gatekeepers, our experiences suggest that relationships with them are highly complex and evolve over time, with sometimes unexpected implications for research. In gathering and analyzing data, researchers become gatekeepers themselves, what we are calling “keymasters.” Reconceptualizing the gatekeeper‐researcher relationship will contribute to ongoing efforts to more fully understand field‐workers as undertaking a practice inherently political, personal, and linked to the production of knowledge.  相似文献   
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In its cationic,trivalent form,Chromium(Cr)it is a micronutrient,and exhibits low environmental mobility.In hexavalent form,however,it is a human carcinogen and also highly mobile.Climate is a key environmental factor controlling weathering rates and stability of primary and secondary Cr-bearing minerals.Knowledge of Cr oxidation state and mineral residence is therefore essential to estimating the risk posed by Cr in serpentinites,chromite mine wastes,and soils developed on these parent materials.X-ray absorption spectroscopy(XAS)is currently the best available technique for determination of the relative abundance of Cr(III)and Cr(VI)in situ(that is,without digestion of solid phases).A brief review of relevant XAS studies of is presented below,focusing on studies in tropical climates1,as they will be most relevant to eastern Cuba’s extensively serpentinized ophiolite belt.Cr(III)-bearing spinels are usually the dominant and most refractory Cr host in ultramafic rocks.Previous XAS studies2 indicate that in tropical climates,Cr-spinels weather rapidly to form Cr(III)-bearing secondary Fe(III)(hydr)oxides(goethite,hematite).Manganese(Mn)is also enriched in ultramafic rocks2;as Mn(IV),it can also co-precipitate with Fe(III)(hydr)oxides,or form its own secondary(hydr)oxides.A previous study found up to 20%Cr(VI)in in a tropical,serpentine soil that contained substantial Mn,and a strong correlation between the*amounts of Cr(VI)and Mn(IV)in the soil profile2.Theresults of several XAS studies suggest that a close association of Mn(IV)and Cr(III)in secondary Fe(hydr)oxides is necessary for oxidation of Cr(III)to Cr(VI)via electron transfer reactions with Mn(IV);however,additional XAS studies have shown that organic matter3and Cr-bearing aluminosilicates4 may also be important sources of Cr(III)to the environment under specific conditions.The stability and fate of Cr has not been studied in detail for these two host phase types,to the best of our knowledge.Access to XAS facilities to perform Cr geochemical experiments is limited and will only become more so in the future.We are working to develop and apply(micro)Raman spectroscopy to evaluate Cr oxidation state and mineral residence(in crystalline and amorphous materials).In addition to standard Raman scattering,we are employing resonance Raman(785 nm laser)to enhance signal from Cr(VI)-bearing phases and laser-stimulated photoluminescence to identify Cr(III)associated with Al-rich alteration products  相似文献   
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ABSTRACT. The city of Amarillo, Texas, is unusual in that more than 5,000 art objects in the form of signs are displayed on individual properties. These signs represent a unique partnership between the public and a wealthy individual, Stanley Marsh 3, who subsidizes them. Through a field survey of 723 signs and a questionnaire mailed to 98 residents with signs in their yards, we explored use of the signs for communal and individual expression. The field survey found a higher concentration of signs in low‐ and moderate‐income neighborhoods and in Hispanic areas than in high‐income and non‐Hispanic neighborhoods. The questionnaire revealed that residents used signs for both individual and communal expression and that most residents with signs liked them. Dissatisfaction among a small percentage of residents with signs suggested that the vast number of signs may have compromised their initial uniqueness.  相似文献   
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MODELING EPHEMERAL GULLY EROSION FOR CONSERVATION PLANNING   总被引:9,自引:0,他引:9  
1INTRODUCTIONEphemeral gully erosion,which is caused by concentrated flow within cultivated farm fields,is distinct from rill erosion.Ephemeral gully erosion is also distinct from gully erosion in permanent,deep,incised channels,formed by headcuts moving upstream.Ephemeral gully erosion is often overlooked.It is not estimated with rill-interrill erosion prediction technology such as the Revised Universal Soil Loss Equation(Renard et al.,1997),and it is often not measured in field survey…  相似文献   
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