共查询到20条相似文献，搜索用时 233 毫秒
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新疆古尔班通古特地区的土壤结皮及其保护 总被引：1，自引：0，他引：1
生物土壤结皮对于荒漠地区生态环境、土壤形成、防沙固沙等起到积极作用,因此对其进行保护和研究在中国北方荒漠化地区具有重要意义。在阐述生物土壤结皮的生态功能、性质及主要干扰因子的基础上,考虑到其特殊性质及主要的聚集分布区域和受到的潜在干扰,建议在中国新疆古尔班通古特沙漠地区建立生物土壤结皮国家级自然保护区,并提出了拟设立自然保护区的具体区域及相应的建议和措施,以促进生物土壤结皮和荒漠生态系统的研究和荒漠化地区生态环境的恢复与重建。 相似文献
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On the thermomechanical evolution of compressional orogens 总被引：1，自引：0，他引：1
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Exploring some relationships between biological soil crusts, soil aggregation and wind erosion 总被引：5，自引：0，他引：5
A portable wind tunnel was used to test the contribution of biological and physical elements to overall soil aggregation on a soil dominated by biological soil crusts in south-eastern Australia. After moderate disturbance and simulated wind erosion, 90% of surface aggregates on the loamy soil and 76% on the sandy soil were dominated by biological elements (cryptogams). Lower levels of biological bonding were observed on the severely disturbed treatment. Linear regression indicated a significant positive relationship (r2=0·72) between biological soil crust cover and dry aggregation levels greater than 0·85mm. To maintain sediment transport below an erosion control target of 5gm−1s−1 for a 65kmh−1 wind at 10m height, a crust cover of approximately 20% is required. When a multiple regression model which sequentially fitted biological crust cover and dry aggregation greater than 0·85mm was applied to the data, dry aggregation accounted for more of the variation in sediment transport rate than biological crust cover. These data were used to develop a conceptual model which integrates crust cover and dry aggregation, and provides a useful framework within which to predict the likely impacts of changes in soil crust cover and aggregation. 相似文献
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C. J. Greenroyd C. Peirce M. Rodger A. B. Watts R. W. Hobbs 《Geophysical Journal International》2007,169(3):964-987
Geophysical data from the Amazon Cone Experiment are used to determine the structure and evolution of the French Guiana and Northeast Brazil continental margin, and to better understand the origin and development of along-margin segmentation. A 427-km-long combined multichannel reflection and wide-angle refraction seismic profile acquired across the southern French Guiana margin is interpreted, where plate reconstructions suggest a rift-type setting.
The resulting model shows a crustal structure in which 35–37-km-thick pre-rift continental crust is thinned by a factor of 6.4 over a distance of ∼70 km associated with continental break-up and the initiation and establishment of seafloor spreading. The ocean–continent boundary is a transition zone up to 45 km in width, in which the two-layered oceanic-type crustal structure develops. Although relatively thin at 3.5–5.0 km, such thin oceanic crust appears characteristic of the margin as a whole.
There is no evidence of rift-related magmatism, either as seaward-dipping sequences in the reflection data or as a high velocity region in the lower crust in the P -wave velocity model, and as a such the margin is identified as non-volcanic in type. However, there is also no evidence of the rotated fault block and graben structures characteristic of rifted margins. Consequently, the thin oceanic crust, the rapidity of continental crustal thinning and the absence of characteristic rift-related structures leads to the conclusion that the southern French Guiana margin has instead developed in an oblique rift setting, in which transform motion also played a significant role in the evolution of the resulting crustal structure and along-margin segmentation in structural style. 相似文献
The resulting model shows a crustal structure in which 35–37-km-thick pre-rift continental crust is thinned by a factor of 6.4 over a distance of ∼70 km associated with continental break-up and the initiation and establishment of seafloor spreading. The ocean–continent boundary is a transition zone up to 45 km in width, in which the two-layered oceanic-type crustal structure develops. Although relatively thin at 3.5–5.0 km, such thin oceanic crust appears characteristic of the margin as a whole.
There is no evidence of rift-related magmatism, either as seaward-dipping sequences in the reflection data or as a high velocity region in the lower crust in the P -wave velocity model, and as a such the margin is identified as non-volcanic in type. However, there is also no evidence of the rotated fault block and graben structures characteristic of rifted margins. Consequently, the thin oceanic crust, the rapidity of continental crustal thinning and the absence of characteristic rift-related structures leads to the conclusion that the southern French Guiana margin has instead developed in an oblique rift setting, in which transform motion also played a significant role in the evolution of the resulting crustal structure and along-margin segmentation in structural style. 相似文献
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Regional phases in continental and oceanic environments 总被引：1，自引：0，他引：1
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Lithospheric thickness beneath the Dabie Shan, central eastern China from S receiver functions 总被引：7，自引：0，他引：7
P and S receiver functions obtained from a portable array of 34 broad-band stations in east central China provide a detailed image of the crust–mantle and lithosphere–asthenosphere boundaries (LAB) in the Dabie Shan and its adjacent areas. Clear S -to- P converted waves produced at the LAB show a thin lithosphere beneath the whole study area. Based on our results, the thickest lithosphere of 72 km is observed beneath the southern part of the area within the Yangtze craton, whereas beneath the North-China platform, the lithosphere is only 60 km thick. S receiver functions also reveal, in good agreement with P receiver functions, a maximum depth of the Moho beneath the Dabie Shan orogen at approximately 40 km. Furthermore, we interpret the structural difference at 32° latitude as the probable location of the mantle suture formed between the Yangtze and the Sino-Korean cratons. 相似文献
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Crustal structure of the Lofoten continental margin, off northern Norway, from ocean-bottom seismographic studies 总被引：2，自引：0，他引：2
S. Kodaira A. Goldschmidt-Rokita J. M. Hartmann H. B. Hirschleber T. Iwasaki T. Kanazawa H. Krahn S. Tomita H. Shimamura 《Geophysical Journal International》1995,121(3):907-924
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广东省花岗岩出露区面积大,不同侵蚀风化壳岩层为母质的土壤侵蚀过程和侵蚀类型区域差异明显,因此依据不同侵蚀土壤类型的特点进行治理显得十分必要.该省德庆县花岗岩风化壳土壤侵蚀非常严重.在对该地区花岗岩风化壳特性与侵蚀过程关系调查基础上,对花岗岩风化壳剖面分带特征及其物理化学垂直分异特点进行了分析,探讨了花岗岩区侵蚀土壤的发生机理,对花岗岩区主要侵蚀土壤类型、特点及其治理对策进行了讨论. 相似文献
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Fractal structure and characteristic scale in the distributions of earthquake epicentres, active faults and rivers in Japan 总被引：3，自引：0，他引：3
Using a box-counting method, we examined the fractal structures of the spatial distributions of three geological systems in Japan, namely those of earthquake epicentres, active faults, and rivers. Our results show that, in the scale range from 1 to 100 km, all geological systems have a common characteristic scale of ~13 km, which divides the spatial distribution into two bands: a smaller scale r < 13 km and larger scale r > 13 km (where r is the box size). In both bands, the three systems obey a power law distribution, and therefore it is proposed that all geological systems have a band-limited fractal structure. Since the characteristic scale of ~13 km is in agreement with the depth of the brittle–ductile transition zone of the crust, we suggest that it is a common feature of the heterogeneity of the crust. 相似文献