Pollen‐ and diatom based environmental history since the Last Glacial Maximum from the Andean core Fúquene‐7, Colombia     

Maria Isabel Vélez  Henry Hooghiemstra  Sarah Metcalfe  Ignacio Martínez  Herman Mommersteeg 《第四纪科学杂志》2003,18(1):17-30

The late Pleistocene–Holocene ecological and limnological history of Lake Fúquene (2580 m a.s.l.), in the Colombian Andes, is reconstructed on the basis of diatom, pollen and sediment analyses of the upper 7 m of the core Fúquene‐7. Time control is provided by 11 accelerator mass spectrometry (AMS) ¹⁴C dates ranging from 19 670 ± 240 to 6040 ± 60 yr BP. In this paper we present the evolution of the lake and its surroundings. Glacial times were cold and dry, lake‐levels were low and the area was surrounded by paramo and subparamo vegetation. Late‐glacial conditions were warm and humid. The El Abra Stadial, a Younger Dryas equivalent, is reflected by a gap in the sedimentary record, a consequence of the cessation of deposition owing to a drop in lake‐level. The early Holocene was warm and humid; at this time the lake reached its maximum extension and was surrounded by Andean forest. The onset of the drier climate prevailing today took place in the middle Holocene, a process that is reflected earlier in the diatom and sediment records than in the pollen records. In the late Holocene human activity reduced the forest and transformed the landscape. Climate patterns from the Late‐glacial and throughout the Holocene, as represented in our record, are similar to other records from Colombia and northern South America (the Caribbean, Venezuela and Panama) and suggest that the changes in lake‐level were the result of precipitation variations driven by latitudinal shifts of the Intertropical Convergence Zone. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

High‐resolution record of environmental changes and tephrochronological markers of the Last Glacial–Holocene transition at Lake Lautrey (Jura,France)     

Boris Vannire  Gilles Bossuet  Anne‐Vronique Walter‐Simonnet  Pascale Ruffaldi  Thierry Adatte  Michel Rossy  Michel Magny 《第四纪科学杂志》2004,19(8):797-808

This paper presents the results of a multiproxy investigation including volume magnetic susceptibility (κ), mineral and pollen analyses of Late Glacial sediments from Lake Lautrey (Jura, France). Small‐scale lithological variations have been identified with high stratigraphic resolution in order to establish lithostratigraphic correlations between cores. κ measurements, combined with mineralogical analyses, provide information on past sedimentary processes. This combined approach reflects major changes in terrestrial habitats and soil processes which may relate to the climatic events characterising the Late Glacial climatic warming and cooling phases. During warm intervals, the record indicates increased lake productivity via carbonate precipitation and decreased input of detrital material. In contrast, cooler intervals show reduced lake productivity, catchment area instability and increased detrital inputs. Several short interruptions in reforestation and in soil stabilisation can be identified and linked with abrupt colder events occurring through the Bølling. A general trend of warming is recorded from the coldest part of the Younger Dryas. Three tephra layers were also detected. The mineral composition analyses show that the upper tephra layer corresponds to the Laacher See eruption (Eifel, Germany) while the lower ones may relate to the volcanic activity of the Chaîne des Puys (Massif Central, France) around 13 000 cal. yr BP. These two events, recognised for the first time outside the Massif Central region, may provide additional chronostratigraphic markers for the Late Glacial sedimentary records of the Jura mountains and northern Alps. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

地质内、外力作用形成的堰塞湖     

季泰 《城市地质》2008,3(3):49-50

该文简要介绍了地震堰塞湖、火山堰塞湖、冰碛堰塞湖的形成原因及特点。  相似文献   

Production of Potash and N-Mg Compound Fertilizer via Mineral Shoenite from Kunteyi Salt Lake: Phase Diagrams of Quaternary System(NH_4)_2SO_4-Mg SO_4-K_2SO_4-H_2O in the Isothermal Evaporation and Crystallization Process     

LI Cheng  CHEN Xueqing  GUO Hongfei  ZHOU Xue  CAO Jilin 《《地质学报》英文版》2021,95(3):1016-1023

Based on the requirement of the new technology for producing potassium sulfate and N-Mg compound fertilizer,boussingaultite,by the reaction of the mineral shoenite from Kunteyi Salt Lake,Qinghai province,and the industrial byproduct ammonium sulfate,the solubilities of the quaternary system (NH_4)_2SO_4-Mg SO_4-K_2SO_4-H_2O at 25.0oC in the isothermal evaporation and crystallization process were measured using the isothermal evaporation method,and the corresponding phase diagrams were plotted.According to the diagram,this system contains six saturation points and six solid phase fields of crystallization,which correspond to (K_(1-m),(NH_4)_m)_2SO_4,(NH_4)_2SO_4·Mg SO_4·6H_2O,K_2SO_4·Mg SO_4·6H_2O,Mg SO_4·6H_2O,(K_(1-n),(NH_4)_n)_2SO_4·Mg SO_4·6H_2O and Mg SO_4·7H_2O,respectively.By analyzing and calculating the isothermal evaporation and dissolution phase diagram of this quaternary system at 25.0oC,K_2SO_4 and (NH_4)_2SO_4·Mg SO_4·6H_2O can be separated via K_2SO_4·Mg SO_4·6H_2O and (NH_4)_2SO_4 as raw materials.Theoretical calculations about the proposed process were carried out and verified by experiment,which indicated that the yield of potassium sulfate was improved and the magnesium resources were fully utilized.  相似文献   

1995-2015年全球不同气候带典型冰川补给型湖泊动态变化          下载免费PDF全文

刘吉平  金晶  李晟铭  宋开山 《水科学进展》2021,32(1):1-9

基于1995年、2005年和2015年3期Landsat影像数据,利用遥感和地理信息系统技术,分析全球不同气候带典型冰川补给型湖泊面积、数量及其对气候变化的响应。结果表明:①1995-2015年全球典型冰川补给型湖泊面积增加了2.32%,数量减少了2.26%,其中以小型湖泊（< 1 km2）和大型湖泊（>50 km2）面积变化最为剧烈,中型湖泊（1~50 km2）面积则相对稳定,1995-2005年冰川补给型湖泊面积与数量的变化速率相比2005-2015年较快。②1995-2015年热带、亚热带、温带冰川补给型湖泊面积与数量均在增加,其中以热带冰川补给型湖泊变化最为剧烈,其面积上升了20.62%,数量上升了25.32%,亚寒带与寒带冰川补给型湖泊面积与数量均减少,其中以寒带冰川补给型湖泊变化最为明显,其面积减少了11.3%,数量下降了18.97%。可为全球典型冰川补给型湖泊的变化及其影响因素的后续研究提供依据和参考。  相似文献   

湖泊沉积对地震动的响应特征与古地震序列重建     

李德文  李林林  马保起  张健 《地学前缘》2021,28(2):232-245

湖泊沉积因其对地震动的敏感而被认为是“天然地震仪”,湖泊沉积古地震研究有机会重建长时间尺度的地震(动)序列,对认识区域发震孕震环境和地震复发规律具有潜在优势,是当前古地震学研究的重要方向之一。本文旨在总结现今湖泊沉积古地震研究的主要进展、存在的问题和未来展望。首先通过与传统古地震研究关注的记录对比,扼要介绍了湖泊沉积地震动记录在形成和保存潜力、空间分布以及感应能力等方面的相对优势。然后从过程角度总结了湖泊沉积对地震动响应的主要机制,着重剖析了液化、流化和沉积物再悬浮等不同机制在控制因素、过程特点、响应阈值等方面的异同。再结合湖泊沉积对地震动响应的过程特点和研究现状,总结了不同类型的湖泊沉积地震动记录,对比分析了变形构造、块体运动堆积、浊流堆积和再悬浮沉积等4种类型记录的沉积学和动力学特征;对不同类型记录的古地震学含义和研究手段进行了梳理。再总结了地球物理勘探、结构构造和理化代理指标等现阶段流行的方法在不同尺度湖泊沉积古地震识别和古地震序列重建中的适用性和局限性,后者主要缘于湖泊沉积系统本身的复杂性和外部扰动过程的多样性。最后指出,当前湖泊沉积古地震研究面临的主要问题是缺乏普适性的响应模式、判别依据和甄别准则;今后工作应致力于对湖泊沉积地震动响应过程的深入理解,积极引进数字或试验模拟等理论工具与方法,从二维观察扩展到三维重建;数据解释力求宏观结合微观,由单一指标转向综合性组合式指标,为最终建立普适性的诊断指标和判别依据服务。  相似文献   

Progress in Numerical Simulation of Long-Term Impact of Thermokarst Lakes on Permafrost Thermal Regime     

Feng Ling  Tingjun Zhang 《地球科学进展》2018,33(2):115-130

Thermokarst lakes are a major heat source for the adjacent permafrost and a significant source of atmospheric methane. These lakes have important impacts on the physical, chemical, biological, geomorphological and hydrological processes occurring in the ground under and around thermokarst lakes, and seriously affect the local environment and the stability of the structures constructed in permafrost regions. Numerical simulation methods provide an effective method for quantitative analysis of the long-term impact of thermokarst lakes and their evolution on permafrost surrounding the lakes, and have deepened our knowledge about the impact of thermokarst lakes immensely. Summarizing the research progresses in numerical simulation of long-term impact of thermokarst lakes on thermal regime of surrounding permafrost has an important guiding function to improve mathematical models and develop more effective models. In this study, the components, functions, advantages and defects of several typical mathematical models having developed over the past ten years or so were reviewed, such as the heat conduction model with phase change, thaw slumping model, the coupled lake-permafrost model, thaw lake expansion model combining thermal processes with mass wasting and thaw-driven subsidence, the coupled heat conduction and moisture migration model, and the moving mesh method based thermokarst lake dynamic evolution model. Several issues deserving to be paid further attention in the future researches were proposed, including creating more effective models, determining the more realistic initial condition, lucubrating thermal and physical parameters of the typical soils, consider the impact of lake water replenishment, quantitative analysis of the thermal effect of supra-permafrost water flow around the thermokarst lakes, creating the coupled governing equation of heat conduction with phase change and convective heat transfer, embed ding the effect of climate warming in the model, numerical investigation of the long-term influence of thermokarst lake drainage on the environment change in permafrost regions, analyzing the long-term joint impact of multiple lakes on adjacent permafrost, simulating the near-shore talik development process and feature beneath shallow water in expanding thermokarst lakes, and continuing to do the systemic and comprehensive field measurements.  相似文献   

Study on Environmental and Hydrological Effects of Thermokarst Lakes in Permafrost Regions of the Qinghai-Tibet Plateau     

Fujun Niu  Wei Wang  Zhanju Lin  Jing Luo 《地球科学进展》2018,33(4):335-342

Thermokarst lake is the most visible morphologic landscape developing during the process of permafrost degradation, and it is still an international hot topic in permafrost research. The climate warming, and the consequent degradation of the permafrost on the Qinghai-Tibet Plateau aggravate thermokarst lake development. The permafrost is normally considered as an aquiclude, and the permafrost degradation, especially when the permafrost is completely thawed by a thermokarst lake, might influence regional ground water. Therefore, a research program focusing on environmental and hydrological effects of thermokarst lakes in permafrost regions of the Qinghai-Tibet Plateau was started and supported by the National Natural Science Foundation of China. The work proposed by the application includes: To analysis the spatial and temporal distribution rule of thermokarst lakes in the Qinghai-Tibet Engineering Corridor (QTEC) under the climate change and engineering activities, and to evaluate the ecological environment effects through remote sensing and field investigation; to reveal the main factors influencing a typical thermokarst lake and its hydrothermal condition, and to elucidate the conversion relationship between the thermokarst lake and the groundwater with hydrological and isotope tracer tests; to make an analysis of the influences of different lake stage and size on regional permafrost, hydrological conditions and ecological environment through numerical simulation and statistical modelling, considering the relationships between the thermokarst lake and the ground water level. The research results will help to accurately assess regional permafrost ecological environment evolution and trend prediction, and to reasonably understand the impact factors of the permafrost hydrological evolution and its response mechanism to the ecological environment in the river source regions of the Qinghai-Tibet Plateau. In this paper, the research status analysis, the main research contents, research objectives and prospects were introduced so as to provide some references for related researchers and engineers.  相似文献   

基于Fluent数值模拟的冰湖涌浪分析 ——以西藏聂拉木县嘉龙错为例     

阿如汉  涂杰楠  刘红岩  童立强  郭兆成 《冰川冻土》2018,40(4):837-845

冰湖溃决洪水或泥石流（GLOF）是青藏高原主要灾害之一,其形成的灾害链对人民的生命财产安全造成了严重的威胁,其中冰崩导致的冰湖溃决是GLOF的主要灾害形式,但由于其发生位置偏远、间隔时间长、随机性强,导致实地观测资料缺乏,冰崩入湖形成的涌浪机理和过程仍不清晰,而涌浪的规模是GLOF造成下游灾害大小的最主要因素。为分析冰湖涌浪的产生、沿程传播过程和对冰碛坝的爬坡高度,以西藏聂拉木县嘉龙错为例,采用有限体积法,基于流体计算软件Fluent,模拟了嘉龙错补给冰川发生冰崩导致冰湖涌浪的过程。结果表明：数值模拟能较好地对涌浪的产生、规模、沿程传播和对岸爬坡过程进行再现,涌浪初始高度随着冰湖水深、冰体入湖速度和冰体厚度的增加而增大,涌浪高度增加趋势随着冰体入湖速度和冰湖水深的增加而增大,随着冰体厚度的增加而减小。  相似文献   

中国玛珥湖及其研究意义   总被引：4，自引：2，他引：2  

储国强  刘嘉麒 《岩石学报》2018,34(1):4-12

随着全球变化研究的深入,科学家们认识到古气候变化除轨道尺度的冰期/间冰期旋回之外还存在年代际-千年尺度的高频变化和突变事件。要认知这些变化,古气候记录的时间分辨率要达到"年-年代际"。因此,寻求时间跨度长、连续性好、信息丰富的高分辨率记录是过去全球变化研究面临的主要任务之一。玛珥湖为火山射汽喷发形成的封闭湖泊,由于其独特的形成机制及水文背景,使其能够提供数万年乃至几十万年连续稳定的沉积记录,是高分辨率古气候、古环境变化研究的重要对象。中国玛珥湖得天独厚,从热带到寒温带均有分布,为系统研究中国不同气候区各种时间尺度古气候变化规律提供了理想材料。本文基于中国玛珥湖的分布及沉积特征,探讨玛珥湖沉积记录能够为古全球变化研究做出怎样的贡献,解决什么科学问题,具体包括以下三个方面的内容:(1)在轨道尺度上,精确定位现代气候在地质历史中的位置是未来最具挑战性的科学问题之一。我国热带地区玛珥湖沉积物跨越了至少4个冰期-间冰期旋回,能够为理解冰期驱动机制、下一次冰期来临、高低纬关联等关键科学问题提供多学科数据;(2)千年尺度古气候变化,其成因可能源于不同的动力学机制,是气候系统对各种外部和内部驱动因子响应的结果,因此千年震荡可能存在明显的时空差异。集成不同气候带的玛珥湖沉积记录将为理解千年震荡规律及其驱动因子做出贡献;(3)年-年代际气候变化是预测未来气候变化的基础,PAGES、IPCC以及PAGES-Asia 2K均将过去2千年来气候变化作为预测未来几十年至百年尺度上重大全球变化的背景,并为此构建全球数据体系,玛珥湖沉积特别是纹层沉积记录能够填补某些地区高分辨率数据的空白。  相似文献