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91.
The recent discovery of a subfossil polar bear (Ursus maritimus) jawbone in the Poolepynten coastal cliff sequence, western Svalbard, and its implications for the natural history of the polar bear motivated an effort to better constrain the environmental history and age envelope of the Poolepynten sediment sequence. The focus of the present study is on the lithostratigraphy of the coastal cliffs and on re‐dating the sequence using the Optically Stimulated Luminescence (OSL) dating technique. We report a revised lithostratigraphy and nine new OSL ages. It is concluded that the Poolepynten sequence contains evidence of four regional glaciation events, recorded in the strata as erosional unconformities or glacial deposits followed by shallow‐marine deposition signifying transgressions and subsequent glacio‐isostatic rebound and regression. Our OSL ages refine previous age determinations (14C and IRSL) and support the interpretation that the subfossil polar bear jawbone is probably of last interglacial (Eemian) age.  相似文献   
92.
Research was undertaken to establish the present coastal dynamics of the area south of Espinho, Portugal, with special emphasis on the migration inland of beaches and the retreat of cliffs during at least the last century.
Besides the Holocene units (the Silvalde-Paramos tijuca Formation, 2310 ± 80 yr BP to 500 ± 80 yr BP, and the Cortegaca Beach Formation, 6850 ± 60 yr BP to 950 ± 80 yr BP), a Pleistocene unit (the Maceda Beach Formation, 29, 600 ± 690 yr BP to 14300 ± 160 yr BP) with trunks of Pinus sylvestris was recognized. The Cortegaca Beach Formation comprises a truncated podzol profile, the Al horizon dating from 3490 ± 60 yr BP to 950 ± 80 yr BP. The study and the dating of the Pleistocene and the Holocene formations suggest a model of evolution related to sea-level fluctuations and neotectonics, during the interval between 29,000 ± 690 yr BP and the post-XVth century (Little Ice Age).
The final purpose of the research is to apply the results to the prediction of the coastal zone evolution, and particularly to influence policy with respect to coastal zone management. This policy must take into account the inland migration of the beaches and the cliff retreat as a consequence of the natural dynamics of the earth that cannot be arrested or controlled by man.  相似文献   
93.
Like most sill fjords, Gullmar Fjord on the Swedish west coast, is subject to periods of stagnation. Deep water is usually renewed annually, but since the late 1970s several low-oxygen events have been documented in the deepest part of the fjord. These events occurred during a time when the North Atlantic Oscillation (NAO) was in a highly positive phase. We investigated how the benthic environment, in the deepest part of the fjord, has varied during the 20th century, using benthic foraminifera and an extensive history of instrumental hydrographic data. The foraminifera have undergone one major faunal change and two minor modifications during this time. The major faunal change occurred in the late 1970s to early 1980s, when the common Skagerrak-Kattegat fauna was replaced by one dominated by the opportunistic, low-oxygen-tolerant species,Stainforthia fusiformis. This major faunal change appears to be related to the severe low-oxygen event in 1979–1980. In the latter part of the 1990s the fauna changed again; the concentration ofS. fusiformis was still high, but other low-oxygen-tolerant species also became important. This minor faunal modification occurred in connection with the 2-yr stagnation period between 1996 and 1998 when a low-oxygenevent evolved, the most severe recorded in Gullmar Fjord. Between 1930 and 1980, there was little faunal variation, and a stable fjord environment is indicated. During this time, negative NAO indexes dominated and climate was more continental, with an increase in winds from the northeast and east. In connection with a climate transition indicated by the NAO index switching from positive to negative, a minor faunal change occurred in the late 1920s to early 1930s: the concentration of the Skagerrak-Kattegat fauna increased markedly in the fjord. The fauna characterizing the positive NAO phase between 1900 and the late 1920s is very different from the present positive NAO fauna. The foraminiferal record laid down between approximately 1914 and 2001 indicates that between 1930 and 1980 Gullmar Fjord was a stable fjord environment. During the last 20 yr, it experienced conditions that were more fluctuating and changing. For the most part, changes in the foraminiferal fauna are caused by changes in the deep-water renewal, their extent and frequency, which in turn are caused by climatic oscillations.  相似文献   
94.
The objective of this paper is to demonstrate that accurate and reliable in situ stress measurements can be performed in soft rocks. A quick overview of the mechanical behaviour of soft rocks is presented. After reviewing stress measurement techniques that have been used in soft rocks, the modified doorstopper technique is presented and the advantages it has over other techniques in soft rocks are underlined. Results from laboratory simulations in controlled conditions show that the technique is reliable and accurate. It is then shown, through field applications in a potash mine in Brazil, in an underwater tunnel in shales in Canada and in an exploratory drift in molassic rocks of the French Alps, how the technique yields results that can sometimes be confirmed by field observations.  相似文献   
95.
Late Neoproterozoic (ca. 580 Ma), high-K, mafic-intermediate rocks represent voluminous bimodal magmatism in the Borborema Province, northeast Brazil. These rocks show the following chemical signatures that reflect derivation from a subduction-modified lithospheric mantle source: (1) enrichment in large ion lithophile elements (Rb, Ba, K, Th) and light rare-earth elements (REE) (La/YbCN=11–70), (2) pronounced negative Nb anomalies, and (3) radiogenic Sr (0.71202–0.7059) and unradiogenic Nd (Nd from −9.3–−20.1) isotopic compositions. TDM model ages suggest that modification of the lithospheric mantle source (metasomatised garnet lherzolite) may have occurred in the Paleoproterozoic during the Transamazonian/Eburnean tectonics that affected the region. Interaction with asthenospheric fluids is believed to have partially melted this enriched source in the Neoproterozoic, probably as a result of asthenosphere-derived fluid percolation in the Brasiliano/Pan-African shear zones that controlled the emplacement of these mafic-intermediate magmas. The involvement of this asthenospheric component is supported by the nonradiogenic Pb isotopic ratios (206Pb/204Pb=16–17.3, 207Pb/204Pb=15.1–15.6, 208Pb/204Pb=36–37.5), which contrast with the enriched Sr and Nd compositions and thereby suggest the decoupling of Rb–Sr, Sm–Nd, and U–Pb systems at the time of intrusion of the mafic-intermediate magmas in the crust.  相似文献   
96.
Russian agriculture sensitivity to changes in climate, soil and atmosphere chemistry were analyzed. Calculated data are presented on crop productivity of grain crops and grasses (C3) under arid and humid scenarios of climate taking account of one-, two-, three and four-factor natural environment impacts. All four factors under studies (climatic parameters, CO2 and tropospheric ozone concentrations, soil degradation extent) greatly impact agriculture productivity. The effect of interaction between all considered factors on agroecosystem productivity is studied. It is established that a simple additive scheme for explaining the complex effect of some factors can be much violated. In this case, not only variations in the mean crop yield levels but also variations in the degree of crop stability have been assessed in some regions, that may be more important for determining the social-economic consequences. It turned out that the recurrence of critically very low yields in steppe regions may increase two fold as a result of global warming.  相似文献   
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99.
The amount of green space in urban areas is shrinking. Densification and the introduction of new user groups in most cities today is leading to more intensive use of public spaces and the need for more space. Urban cemeteries constitute a unique type of public space: while some may consider them primarily religious and contemplative spaces, others see them as primarily recreational or as heritage sites steeped in history. The authors examine the extent to which the pressure on cities’ open green areas combined with influences from intercultural encounters is mirrored in the use and character of cemeteries today – exemplified by Gamlebyen Cemetery (Gamlebyen Gravlund) in Oslo, Norway. They used observations in combination with short semi-structured interviews with those using the cemetery. The findings of pilot study conducted in 2013 suggest that religious aspects played a minor role and that the recreational aspects were more important to most of the interviewees. Many of them considered that the cemetery provided a pleasant green walkway on their way to work, busses or city services. The cemetery offered a combination of calmness, an aesthetically pleasant environment, and ‘cultivated nature’ in an urban context, and was thus an arena that invited respect and esteem.  相似文献   
100.
The emerging chemical society and new political demands on improved ecological sustainability have put the urban water and sanitation system under pressure. It is recognised that the users need to partake in the problem solving, but to influence human practice we must understand it. A theoretical framework, founded on time-geography and cultural analysis, was developed and applied in a study on the interrelationship between changes in water and sanitation arrangements at the household level and residents’ routines. This article describes the theory cross-fertilisation and its prospect of application in studies of human environmental action.  相似文献   
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