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991.
The eastern part of Qilian Mountains experienced strong tectonic uplift during the late Quaternary, and climate record there was influenced by Tibetan Plateau to some extent. Based on studies on the fluvial terrace series and eolian loess deposition, we find that the tectonic uplifts of the Tibetan Plateau had coupled with climatic changes in our studied region and others since the mid-Pleistocene. The uplift that occurred at 0.83 Ma corresponded to significant desert expansion in L6 and periodic variation since MIS16, while the 0.14Ma one to the further drying in northwest China. Those coupled events may indicate that tectonic uplift drove climatic changes, and the Tibetan Plateau has important impacts on East Asian Monsoon system. 相似文献
992.
黄河三角洲上的冰成隆丘的研究 总被引:7,自引:3,他引:7
黄河三角洲上发育了大量的冰成构造,非常引人注目,冰成隆丘便是其中的一种。冰成隆丘外观上呈丘状,以圆丘状者多见,少数呈长丘状、不规则台状、塔柱状、土堆状及火山状;规模不等,小者高数厘米,大者数十厘米,最大长度可达 1m以上;表面平滑或具有裂缝或有火山口状坑穴,或有大量豆状瘤状或根状构造。有的内部具有穹隆状层理,有的具有复杂的变形层理。冰成隆丘一般产在边、心滩上或河床上,共成因有三种:一是冰融水滴积;二是冰融陷拱隆;三是冰洞滴积。黄河特殊的水文、水动力及气侯条件使得冰层中有时含有 (大量 )泥砂或冰层之上被泥砂覆盖,当这些冰层融化时,其中或其上的泥砂便会随冰融水一道滴向地表,在地表的相应部位形成冰成隆丘;当冰层中有孔洞时,且其上又沉积了一层泥砂,那么当冰层溶化后,在孔洞的部位便会因拱隆而开成隆丘;如果边、心滩上的侵蚀坑穴中的冰层中心或其它部位有融化形成的孔洞或裂缝,那么冰层之中或之上的泥砂便会随冰融水一道沿孔洞或裂缝滴落到坑穴中,形成冰洞漏积隆丘冰成隆丘是一种暴露和低温 (± 0℃ )条件下的产物。其成因与黄河复杂的冰-水-泥砂作用有关。 相似文献
993.
广西柳州白莲洞遗址的铀系年龄 总被引:9,自引:0,他引:9
因涵盖新—旧石器过渡、出土人类化石及别具一格的石制品 ,广西柳州白莲洞遗址对古人类和石器文化的研究具有重要意义。新生碳酸盐岩铀系测年的结果表明 :该遗址新—旧石器间的过渡期不超过 3ka± ,短于基于钙板 1 4 C测年得出的 6 ka± ;西 6层钙板和石笋的 2 3 0 Th年龄为 16 0 ka± ,西 7层人牙化石的年代应大于此值 ;“白莲洞式”石片打制法呈清晰的演化脉络 ,时间跨度至少为 15 0 ka。邻近的柳江人地点和土博前洞铀系测年结果与本文一致。这些地点年代位置的大幅度前移 ,是我国晚更新世人类遗址已有年代框架被总体压缩的例证。具现代解剖特征的智人在中国出现的年代很可能比原认为的早得多 相似文献
994.
995.
Simulation study was applied in the development planning of East Unity oil field, Sudan. A grid consisting of 2 000 cells was constructed. A major challenge of the study was to evolve a full field development and future reservoir management strategy that would ensure maximum recovery of oil based on well Un51. Simulation shows that Un51 as injection well in AradiebaC would yield better oil recovery than to be production well. 相似文献
996.
The project of ‘grain for green’, to restore woodland and grass by retreating from slope farmland, as a fundamental measure
of eco-environmental rehabilitation, is being conducted in the reservoir area of the Three Gorges gradually. However, the
de-farming of slope farmland will reduce the amount of farmland in de-farmed areas, especially in the areas with concentrated
slope farmland, which would cause the problems of environmental emigration. The people who cannot regain enough farmland by
relocating farmlands within village after de-farming and have to emigrate to other places are called environmental emigrants
or ecological emigrants. In the research, a de-farming stress index model and an environmental emigration model are developed
based on GRID data, and the potential amount of environmental emigration caused by de-farming of slope farmland in the reservoir
area is simulated aided with GIS. The simulation indicates that the potential emigration amount caused by de-farming is quite
large. When the de-farming stress index reaches 40%, the amount is as large as 890,000 people, which is equivalent to the
emigrants caused by the submergence of the Three Gorges reservoir. So it should be considered as a big problem during the
eco-environmental rehabilitation in this area. Some suggestions are raised to tackle the problem. Firstly, the emigration
plan should be included in the de-farming plan. Secondly, some provinces, especially those located in the lower reaches of
the Yangtze River, should accommodate part of the environmental emigrants. 相似文献
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