极地深层冰川微生物研究的现状与意义   总被引：5，自引：0，他引：5       下载免费PDF全文

张晓君  姚檀栋  马晓军 《极地研究》2000,12(4):269-274

极地冰芯的研究对于揭示过去环境的变化规律和预测未来气候环境具有重要意义 ,我国科学家在此领域取得了一系列丰硕成果 ,跨入了国际领先行列。冰芯微生物的研究在国外近年来才刚刚开始 ,并且日益受到重视。南北极和低纬度地区高山冰川深层冰芯中封藏着几千年甚至几十万年的微生物 ,对它们的研究将为微生物多样性研究、过去环境的变迁、生物基因的进化甚至生命起源的研究开辟新的途径  相似文献   

Rapid Ice Margin Fluctuations during the Younger Dryas in the Tropical Andes     

Donald T. Rodbell  Geoffrey O. Seltzer 《Quaternary Research》2000,54(3):328

Radiocarbon dated lacustrine sequences in Perú show that the chronology of glaciation during the late glacial in the tropical Andes was significantly out-of-phase with the record of climate change in the North Atlantic region. Fluvial incision of glacial-lake deposits in the Cordillera Blanca, central Perú, has exposed a glacial outwash gravel; radiocarbon dates from peat stratigraphically bounding the gravel imply that a glacier advance culminated between 11,280 and 10,990 ¹⁴C yr B.P.; rapid ice recession followed. Similarly, in southern Perú, ice readvanced between 11,500 and 10,900 ¹⁴C yr B.P. as shown by a basal radiocarbon date of 10,870 ¹⁴C yr B.P. from a lake within 1 km of the Quelccaya Ice Cap. By 10,900 ¹⁴C yr B.P. the ice front had retreated to nearly within its modern limits. Thus, glaciers in central and southern Perú advanced and retreated in near lockstep with one another. The Younger Dryas in the Peruvian Andes was apparently marked by retreating ice fronts in spite of the cool conditions that are inferred from the ∂¹⁸O record of Sajama ice. This retreat was apparently driven by reduced precipitation, which is consistent with interpretations of other paleoclimatic indicators from the region and which may have been a nonlinear response to steadily decreasing summer insolation.  相似文献   

The fossil oribatid mite fauna (Acari: Oribatida) in late-glacial and early-Holocene sediments in Kråkenes Lake, western Norway   总被引：2，自引：0，他引：2  

Ingrid Wunderle Solhøy  Torstein Solhøy 《Journal of Paleolimnology》2000,23(1):35-47

The oribatid mite assemblages found in late-glacial and early-Holocene sediments in Kråkenes Lake, western Norway, consist of 38 species within 24 genera. In accordance with known present habitat distribution we distinguish 4 true aquatic species, 6 species associated with wetland, 2 with mesic grassland, 12 with dry grassland and heathland, 3 with saxicolous and arboricolous lichens, 7 widely distributed species, and 4 with uncertainly known habitat preferences. The sediments from the pioneer phase (12,300-11,700 ¹⁴C BP) contain 7 species, among them the 2 typical pioneer species Limnozetes ciliatus and Tectocepheus velatus.The sediments of the warmer Allerød interstadial (11,700-10,900 BP) contain 18 species, the cold Younger Dryas (10,900-10,000 BP) 9 species, and the early Holocene (10,000-9,000 BP) 36 species.The oribatid fossils of the pioneer phase indicate habitats and climate similar to the mid-alpine zone in western Norway today, the Allerod interstadial that of the low- to mid-alpine zone. L. ciliatus is the aquatic pioneer species in the Allerod. In the Younger Dryas the climate was more arctic, 60-70% of the species had presumably disappeared, and no aquatic species were found. In the early Holocene, 4 true aquatic species colonised the lake and showed a high productivity. The terrestrial oribatid fauna in this period contained a high diversity of more boreal species, while the alpine species declined or became extinct.  相似文献   

冰后期最大海侵以来长江,钱塘江河口湾发育过程的沉积动力学研究   总被引：2，自引：0，他引：2  

朱玉荣 《海洋地质与第四纪地质》2000,20(2):1-6

利用二进流数学模型对冰后期最大海侵以来５期古岸线与现在岸线条件下古长江河口湾、古钱塘江河口湾及其邻近海域的主要水动力Ｍ２潮流场进行了数值模拟;在此基础上,分别计算了进入不同时期潮流场的７种粒径泥沙的潮平均单宽悬移输沙率与扒移输沙率及其相应的输沙率散度,据此得出不同粒径泥沙在当时潮流场中的悬移与推移输过趋势,划分了海 淤积区与冲刷区 同时期的潮流场作用下,长江入海泥沙除最大限度地沉积在古长江河口湾（  相似文献   

基于MapInfo的古文化遗址保护与监控方案     

曹建农 《测绘与空间地理信息》2000,23(4):22-24

对古文化遗址的文化重要性所覆盖的内涵加以揭示 ;概述了MapInfo的技术特征 ;提出了基于MapInfo的古文化遗址保护与监控方案。  相似文献   

Tree-ring based summer temperature reconstruction for the source region of the Yangtze River on the Tibetan Plateau   总被引：6，自引：1，他引：6  

Eryuan Liang  Xuemei Shao  Ningsheng Qin 《Global and Planetary Change》2008,61(3-4):313-320

Understanding of past climatic variability over the Tibetan Plateau is still limited because of the lack of long-term climatic records. Here we reconstruct the mean summer (June–August) minimum temperature for the past 379 years based on tree-ring data in the source region of the Yangtze River. This reconstruction successfully captures recent abrupt climatic changes and agrees in general with other temperature reconstructions for the Tibetan Plateau on a decadal timescale. The cold and warm periods coincide with documented glacier advances and retreats on the east and southeast Tibetan Plateau. The interval 1816–22 is among the coldest periods in the reconstruction and may be related to the influence of the Tambora eruption in Indonesia in 1815. Comparisons with other paleoclimatic proxies imply a high degree of confidence for our reconstruction and its indicative power for a large-scale climate variability on the Tibetan Plateau.  相似文献   

中国香格里拉生态旅游区冰川旅游资源的特征及其开发   总被引：1，自引：0，他引：1  

刘巧  范继辉  张文敬 《四川地质学报》2005,25(4):242-245

位于川、滇、藏三省交界的香格里拉生态旅游区,是三省自2002年以来协商共同打造的中国的最大的高原生态旅游区.这一区域具有独特的高原雪山、湖泊、草原、森林、野生动植物等自然景观,正是举世闻名的“香格里拉”描绘的写照.冰川旅游资源是香格里拉景观的一个重要组成部分,本文对该区域的冰川资源,即冰川数量、分布及其形态特征作了一个总结,并探讨了该区域冰川旅游资源的开发策略.  相似文献   

基于CT影像的砂岩文物结构特征分析          下载免费PDF全文

王莹莹  徐金明  黄继忠 《中国地质灾害与防治学报》2020,31(1):127-134

对于砂岩文物,成分不同、结构不同,表面变化过程和变化结果也不同。以中国三处(石门山、云冈石窟、乐山大佛)砂岩文物为例,联合使用肉眼鉴定与灰度阈值法得到了砂岩文物CT图像中不同矿物成分的实际分布,分析了不同位置切片图像的成分特点与结构特点,研究了砂岩内部结构数字图像特征参数的变化规律,探讨了三处砂岩文物数字图像特征参数的区别及其与岩样外观表现的关系。结果表明,三处砂岩文物样品主要成分均为石英和长石,石英含量大小顺序是石门山砂岩>云冈石窟砂岩>乐山大佛砂岩;乐山大佛砂岩形状变化最小,云冈石窟砂岩次之,石门山砂岩形状最不规则;石门山砂岩纹理最复杂,乐山大佛砂岩最为简单;乐山大佛砂岩表面风化严重、但随深度增加变化不明显,云冈石窟砂岩距表面越深、风化越弱,石门山砂岩风化变化比较复杂。研究结果对石质文物保护具有重要的参考价值。  相似文献   

The glacial landsystem of a tropical glacier: Charquini Sur,Bolivian Andes          下载免费PDF全文

Jakub Małecki  Harold Lovell  Wojciech Ewertowski  Łukasz Górski  Tomasz Kurczaba  Beata Latos  Michał Miara  Dorota Piniarska  Jacek Płocieniczak  Tomasz Sowada  Marcin Spiralski  Anna Warczachowska  Antoine Rabatel 《地球表面变化过程与地形》2018,43(12):2584-2602

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Excavation of subglacial bedrock channels by seasonal meltwater flow          下载免费PDF全文

Flavien Beaud  Jeremy G. Venditti  Gwenn E. Flowers  Michele Koppes 《地球表面变化过程与地形》2018,43(9):1960-1972

Subglacial water flow drives the excavation of a variety of bedrock channels including tunnel valleys and inner gorges. Subglacial floods of various magnitudes – events occurring once per year or less frequently with discharges larger than a few hundred cubic metres per second – are often invoked to explain the erosive power of subglacial water flow. In this study we examine whether subglacial floods are necessary to carve bedrock channels, or if more frequent melt season events (e.g. daily production of meltwater) can explain the formation of substantial bedrock channels over a glacial cycle. We use a one‐dimensional numerical model of bedrock erosion by subglacial meltwater, where water flows through interacting distributed and channelized drainage systems. The shear stresses produced drive bedrock erosion by bed‐ and suspended‐load abrasion. We show that seasonal meltwater discharge can incise an incipient bedrock channel a few tens of centimetres deep and several metres wide, assuming abrasion is the only mechanism of erosion, a particle size of D=256 mm and a prescribed sediment supply per unit width. Using the same sediment characteristics, flood flows yield wider but significantly shallower bedrock channels than seasonal meltwater flows. Furthermore, the smaller the shear stresses produced by a flood, the deeper the bedrock channel. Shear stresses produced by seasonal meltwater are sufficient to readily transport boulders as bedload. Larger flows produce greater shear stresses and the sediment is carried in suspension, which produces fewer contacts with the bed and less erosion. We demonstrate that seasonal meltwater discharge can excavate bedrock volumes commensurate with channels several tens of metres to a few hundred metres wide and several tens of metres deep over several thousand years. Such simulated channels are commensurate with published observations of tunnel valleys and inner gorges. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献