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1.
U-Th ages have been obtained by TIMS on the growth periods of a stalagmite from the “Grotte des Puits de Pierre-la-Treiche” (northeastern France), during the middle part of the “Weichselian glaciation” (Marine Isotope Stage 3), between 55.36 ± 0.95 and 53.34 ± 0.49 ka and around 45.85 ± 0.49 ka. These episodes are contemporaneous with abrupt climatic variations recorded in Greenland ice cores (Greenland interstadials 12, 14 and 15) that have been previously recognized in European speleothems. They also coincide with two interstadials, known as “Goulotte” and “Pile” in the Grande Pile pollen sequence (eastern France), which have been correlated with the Moershoofd complex in the Netherlands. Such evidence of speleothem deposition related to temperate episodes gives a strong indication of the absence of continuous shallow permafrost during the middle part of MIS 3 in northeastern France. 相似文献
2.
JEAN SOMMÉ RÉ-V. MUNAUT ANNE-FRANCOISE EMONTSPOHL NICOLE LIMONDIN DAVID LEFÈVRE NICOLE CUNAT-BOGÈ JACQUES MOUTHON ÉTIENNE GILOT 《Boreas: An International Journal of Quaternary Research》1994,23(3):231-243
A deep boring (30 m), carried out at Watten (Nord, France) in 1990, has provided an opportunity to undertake palaeoecological studies based on stratigraphy, sedimentology, palynology, malacology and 14 C datings on Early Weichselian and Holocene deposits. The location of the site in the inner zone of the coastal plain, extending in the Aa valley from the southernmost shores of the North Sea upstream to Watten, allows the comparison between interstadials recorded in a pure fluvial environment and the overlying Holocene sediments, in which alternation of marshy, fluvial and marine deposits are observed. The Early Weichselian sequence can be correlated with the Brørup and Odderade interstadials described in northwestern Europe, and belongs within the same palaeogeographical area. At that time the conditions were already continental at Watten. However, the last (Holocene) interglacial has been characterized, at least since the Boreal chronozone, by an oceanic climate and a progressive invasion of the sea, sometimes interrupted by stillstands and withdrawals. 相似文献
3.
MARTINA HÄTTESTRAND ANN‐MARIE ROBERTSSON 《Boreas: An International Journal of Quaternary Research》2010,39(2):296-311
Hättestrand, M. & Robertsson, A.‐M. 2010: Weichselian interstadials at Riipiharju, northern Sweden – interpretation of vegetation and climate from fossil and modern pollen records. Boreas, 10.1111/j.1502‐3885.2009.00129.x. ISSN 0300‐9483. The most complete records of Weichselian ice‐free conditions in northern Sweden have been retrieved from kettleholes in the Riipiharju esker. In an earlier study, the Riipiharju I core was described as containing two Weichselian interstadials and Riipiharju was chosen as type site for the second Weichselian interstadial in northern Sweden. Here, we present a palynological investigation of two new sediment cores (Riipiharju II and III) retrieved from Riipiharju. Together, the new cores comprise a late cold part of the first Weichselian interstadial recorded in northeastern Sweden (Tärendö I, earlier correlated with Peräpohjola in Finland) as well as a long sequence of the second Weichselian interstadial (Tärendö II, earlier named Tärendö). The results indicate that the climate during deposition of the Tärendö II sequence was more variable than earlier suggested. According to the present interpretation it was relatively warm in the early part of Tärendö II; thereafter a long cold phase persisted, and finally the climate was warmer again in the late part of Tärendö II. The warm phases are characterized by Betula‐dominant pollen assemblages, while the cold phase is characterized by high percentages of Artemisia and Gramineae pollen. Since there is still no firm chronology established of the interstadials in northeastern Sweden, two possible correlations are discussed; either Tärendö I and II are correlated with Brörup (MIS 5c) and Odderade (MIS 5a), or, perhaps more likely, they are correlated with Odderade and early Middle Weichselian (MIS 3) time. 相似文献
4.
Kettle holes - stratigraphical archives for Weichselian geology and palaeoenvironment in northernmost Sweden 总被引：1，自引：1，他引：1
ROBERT LAGERBÄCK ANN-MARIE ROBERTSSON 《Boreas: An International Journal of Quaternary Research》1988,17(4):439-468
An active search for pre-Holocene organic deposits in stratigraphically well-defined positions has proved to be a useful tool for reconstruction of glacial and non-glacial Weichselian development in northernmost Sweden. The investigations have been concentrated to kettle holes connected to eskers belonging to a morphologically prominent northwesterly glacial system characterized by extensive drumlinization. Organic deposits, radiocarbon-dated as older than the Holocene, have been found at some 25 localities. Some sites display two organic-bearing sequences separated by a till bed. The pollen flora in the lowest organic bed reflects an interstadial vegetational development: Arctic shrub and herb tundra-subarctic light birch forestherb tundra with ericaceous shrubs and dwarf birch. This interstadial is correlated with Peräpohjola in Finland. During the younger Tärendö Interstadial the vegetational development was similar, but a more continental climate is indicated hy high values of steppe plants, e.g. Artemisia and Chenopodiaceae. The Tärendö Interstadial, correlated with Odderade, wascharacterized by open, unstable soils due to periglacial processes such as cryoturbation and eolian activities. The Weichselian glaciation is divided into three glacial stades separated by ice-free interstadials in the area studied. Except for a zone with S-SW drumlinization the impact of the two later ice sheets is insignificant. 相似文献
5.
全球气候变化下青藏公路沿线冻土变化响应模型的研究 总被引：16，自引：17，他引：16
利用英国Hadley气候预测与研究中心GCM模型HADCM2预测的气温变化背景，分别提取青藏公路沿线地区在2009年，2049年和2099年的气温参数，考虑年平均气温和年平均地温的关系及年平均地温与海拔，纬度的关系模型，多年冻土下界分布模型和地温带分带，建立青藏公路沿线多年冻土下界分布的响应模型和多年冻土地温带的响应模型，研究结果表明，2009年青藏公路沿线的冻土变化较小，多年冻土极稳定带,稳定带和基本稳定带仅发生微弱的变化，基本稳定过渡带和不稳定带变化较大，多年冻土,逐渐退化，2049年青藏公路沿线多年冻土各地温带变化较大，但仍以基本稳定过渡带和不稳定带变化最大，多年冻土发生较大范围的退化；2099年后青藏公路沿线冻土发生了很大的变化，多年冻土发生大面积的退化，融区面积逐渐增大，多年冻土地温带也发生了较大的变化，其中多年冻土上带仅保留了稳定带，极稳定带全部消失，稳定带和基本稳定带全部转化为不稳定带。 相似文献
6.
JONAS SATKUNAS ALMA GRIGIENE FELIX VELICHKEVICH ANN-MARIE ROBERTSSON PER SANDGREN 《Boreas: An International Journal of Quaternary Research》2003,32(4):627-641
Eemian—Weichselian sequences, located outside the maximum limit of the Late Weichselian ice sheet, provide excellent opportunities for the discovery of continuous sedimentary records encompassing the whole Last Interglacial/Glacial cycle. Such a sequence is recorded in a borehole (117P) through the succession in a small kettlehole lake located at Medininkai, eastern Lithuania. The succession consists of peat, gyttja and silt deposited on top of a Saalian till. Pollen and plant macrofossil analysis, lithological analysis, U/Th dating and mineral magnetic measurements on the sediments have allowed 19 lithostratigraphic units and 16 local pollen assemblage zones (LPAZ) to be identified. The palaeocarpological record reveals a clear transition from the Saalian Glacial to the Weichselian stadial and interstadial phases. The mineral magnetic parameters suggest a good correlation between the concentration of magnetic minerals and stadial and interstadial periods. The Merkine (Eemian) Interglacial and two Early Weichselian Interstadials, Jonionys 1 (Brörup) and Jonionys 2 (Odderade), separated by cryomers, are identified. Intervals interpreted as analogous to the Middle Weichselian Denekamp and Hengelo interstadials are also recognized on the basis of pollen assemblages. The results show alternating periglacial and interstadial palaeoenvironments in Lithuania during the Early and Middle Weichselian and are of importance for Late Pleistocene palaeoenvironmental reconstruction of the Baltic area as a whole. 相似文献
7.
祁连山区多年冻土空间分布模拟 总被引：1，自引：1，他引：0
祁连山区位于青藏高原东北边缘,是亚洲水塔重要的组成部分,多年冻土的变化对生态系统和水资源平衡有着重要影响。基于青藏高原第二次综合科学考察、道路勘察钻孔点以及前人所获得的多年冻土下界资料,回归得出祁连山区多年冻土下界统计模型,借助ArcGIS平台在DEM数据的支持下,模拟出祁连山区多年冻土空间分布图。结果表明：祁连山区多年冻土分布的下界具有良好的地带性规律,表现为随经纬度增加而降低的规律;祁连山区多年冻土在空间分布上呈现出以哈拉湖为中心向四周扩散的分布格局;祁连山区总面积约为16.90×104 km2,其中多年冻土面积约为8.03×104 km2,占总面积约47.51%。多年冻土区与季节冻土区之间存在着有不连续多年冻土分布的过渡区,过渡区面积约1.43×104 km2,占总面积约8.46%。 相似文献
8.
祁连山中东部的冻土特征(Ⅰ):多年冻土分布 总被引：8，自引：7，他引：1
祁连山地区地势高耸,气候严寒,冰缘现象广布,各类冰缘现象受地形与水分条件的控制,分布具有明显的规律性.祁连山多年冻土属青藏冻土区,阿尔金山-祁连山亚区,分布在海拔3400 m以上的高山、谷地、盆地中.多年冻土分布具有明显的高度地带性,随高度增加,冻土分布呈现出季节冻土-岛状冻土-连续冻土更替,同时,多年冻土下界高程与经度明显相关,自西向东表现出下降趋势,下降率约为每经度150 m,这一变化与降水在东西方向的变化有关.山区微气候因素复杂多变,也造成了冻土分布的复杂性,局地因素对冻土分布影响显著,对比分析了坡向,植被与水分、岩性,季节性积雪等诸因素对多年冻土分布的影响. 相似文献
9.
气候变化背景下青藏铁路沿线多年冻土变化特征研究 总被引：1，自引：0，他引：1
多年冻土是复杂地气系统的产物, 以升温为特征的气候变化不可避免地对其产生影响. 基于青藏铁路沿线8个天然场地2006-2011年的地温监测资料, 分析了气候变化背景下, 多年冻土升温特征及上限变化规律, 并对低、高温冻土的变化特征进行了对比分析. 结果表明: 2006-2011年监测期间, 铁路沿线多年冻土正在经历明显的升温趋势, 上限附近和15 m深处平均升温率分别为0.015 ℃·a-1和0.018 ℃·a-1, 其中, 低温冻土区在上述两个深度处升温均比高温冻土区显著; 多年冻土上限深度也表现出一定的增深趋势, 平均增深速率为4.7 cm·a-1, 其中, 高温冻土区增深速率大于低温冻土区. 低、高温冻土对气候变化的响应表现出了较大差异. 同时, 受局地因素的影响, 不同区域在升温和上限增深上也存在一定差异. 相似文献
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11.
Jef Vandenberghe Hugh M. French Aldar Gorbunov Sergei Marchenko Andrey A. Velichko Huijun Jin Zhijiu Cui Tingjun Zhang Xudong Wan 《Boreas: An International Journal of Quaternary Research》2014,43(3):652-666
This paper accompanies a map that shows the extent of permafrost in the Northern Hemisphere between 25 and 17 thousand years ago. The map is based upon existing archival data, common throughout the Northern Hemisphere, that include ice‐wedge pseudomorphs, sand wedges and large cryoturbations. Where possible, a distinction is made between areas with continuous permafrost and areas where permafrost is either spatially discontinuous or sporadic. The associated mean annual palaeo‐temperatures that are inferred on the basis of present‐day analogues increase understanding of the possible changes in permafrost extent that might accompany current global warming trends. Areas with relict permafrost and areas that were formerly exposed due to lower sea level (submarine permafrost) are also mapped. Mapping is mostly limited to lowland regions (areas approximately <1000 m a.s.l.). Striking features that appear from the map are (i) the narrow permafrost zone in North America, which contrasts with the broader LPM permafrost zone in Eurasia (that may be related to different snow thickness or vegetation cover), (ii) the zonal extent of former LPM permafrost (that may reflect sea‐ice distribution), which contrasts with the present‐day pattern of permafrost extent (especially in Eurasia) and (iii) the relatively narrow zones of LPM discontinuous permafrost (that may indicate strong temperature gradients). 相似文献
12.
大兴安岭东坡新林林区冻土变化特征 总被引：3，自引：3，他引：0
大兴安岭处于欧亚大陆多年冻土带南缘, 其多年冻土形成、 发展和保存更多受制于植被、 水分等局地因子的影响。采用钻探、 探地雷达和冻土温度长期监测等手段研究发现, 放牧活动会影响大兴安岭东坡新林林区活动层厚度, 放牧活动比较强烈的地段, 活动层可达2.5 m, 放牧区边缘至未放牧区域, 活动层缩减至1.5 m。塔头2013年11月2.0 m处的地温仍然在0 ℃以上（0.04 ℃）, 当放牧行为终止及加漠公路改道后, 2.0 m处的温度开始逐渐恢复, 温度由-0.12 ℃降到-0.69 ℃, 1.5 m处的温度则由0.17 ℃降到-0.42 ℃, 2018年底塔头的活动层厚度已经小于1.5 m。从地表植被类型上看, 松树林、 塔头和灌丛的活动层多年平均厚度分别为0.8 m、 1.3 m和0.7 m, 近地表0.5 m处的年平均地温为0.07 ℃、 0.52 ℃和0.22 ℃, 年变化深度处（11 m）的年均温度为-1.34 ℃, -0.98 ℃和-2.19 ℃。从地温曲线类型上看, 灌丛下的多年冻土比较稳定, 地温曲线属于正梯度型。松树林和塔头下的冻土温度比较复杂, 松树林地温曲线为偏负梯度型-零梯度型-偏正梯度型, 塔头为负梯度型-扭曲型。在地表植被类型和人类活动的共同影响下, 研究区多年冻土经历了地表干扰开始退化、 干扰消除不再退化以及慢慢恢复的过程。 相似文献
13.
瞬变电磁法（TEM）在青藏高原、东北等地区的多年冻土调查中取得了较好的应用效果,但局限于松散沉积层较厚情形,在基岩埋深较浅条件下探测多年冻土基本处于空白。兰州马衔山多年冻土具有分布范围小、温度高、基岩埋深浅的特点,是应用TEM探测浅基岩埋藏条件下多年冻土分布的理想地区。以马衔山多年冻土为主要研究对象,以季节冻土为对照研究了瞬变电磁响应特征,结合区域构造特征、地层露头、钻孔岩心、地温监测数据等信息,论证并探讨了TEM应用于浅基岩埋深时对多年冻土的探测效果。结果表明：马衔山多年冻土分布受构造断裂形成的低阻带控制,下部为负温岩层,实际分布面积为0.11 km2;TEM应用于浅基岩埋深的多年冻土勘探时更多的对地下岩层做出响应,可结合地质、地貌、水文、植被等信息,利用多年冻土的特点和电阻率的变化情况来判断多年冻土的分布范围;当基岩埋深特别浅时可以与探地雷达、钻孔等其他手段联合反演,从而准确地识别多年冻土与下伏基岩。 相似文献
14.
融化作用下多年冻土隧道围岩的弹塑性解及其与支护的相互作用分析 总被引：1，自引：0，他引：1
多年冻土隧道修建中,施工活动产生的热量将导致多年冻土围岩中出现一定范围的融化圈,进而影响支护的受力以及隧道洞室的收敛。将围岩分为融化区和未融化区,将融化区围岩视为弹塑性介质,未融化区围岩视为弹性介质,建立并求解融化作用下多年冻土隧道围岩弹塑性模型,对不同的围岩条件及支护工况下多年冻土段隧道施工中围岩与支护的相互作用进行分析。结果表明,该模型表现了融化作用下多年冻土围岩与支护相互作用的特征;在较差围岩中,喷射混凝土支护的强度是控制融化作用下多年冻土围岩稳定以及隧道周边位移量的关键因素。在多年冻土隧道施工中,可采用本模型确定施工中容许的最大围岩融化深度,施工中应采取有效措施避免围岩中出现过大的融化圈。 相似文献
15.
青藏高原开发中的冻土问题 总被引：46，自引：0，他引：46
在国家决策西部大开发战略之际, 正确评价青藏高原开发中所面临的冻土问题, 为生态环境建设和国民经济持续稳定发展提供依据, 显得更为重要。多年冻土占据着青藏高原一半以上的疆土面积, 受全球气候变化和人为活动的共同影响, 在过去的几十年中已发生了不同程度的变化, 且随着人类活动增强, 变化必将加剧, 冻土问题也将显得日益突出。多年冻土的变化主要表现为多年冻土的地温升高、上限下降和面积缩减等, 进而影响到各类工程的地基稳定性, 使工程建筑受到不同程度的破坏;同时, 由于气候变化、过度放牧和工程活动的影响, 地面水热状况改变, 尤其是地表土壤层中水分含量的降低, 导致了草场退化, 生态环境恶化。在分析这些冻土问题原因的基础上, 作者预测了在未来开发中可能出现的冻土问题, 并提出了建议。 相似文献
16.
17.
依据祁连山和青藏高原气温、地温、冻土厚度与经纬度以及海拔的经验公式, 通过ArcGIS空间分析, 获得了祁连山地区年均气温、年均地温和冻土厚度的空间分布规律。祁连山多年冻土区年均气温和年均地温分别为-12~-6 ℃和-4~-2 ℃, 多年冻土厚度变化于90~140 m之间。其中, 哈拉湖地区海拔4300 m以上的高山区温度最低、冻土最厚, 年均气温和年均地温分别低于-10 ℃和-4 ℃, 多年冻土厚度大于140 m。结合祁连山烃源岩区域分布特征和木里天然气水合物钻孔的冻土厚度资料, 认为中祁连盆-山构造地貌发育区为天然气水合物成藏最有利区域。 相似文献
18.
Wolfgang Schirmer 《Central European Journal of Geosciences》2010,2(1):32-40
All younger Pleistocene interglacials form interglacial complexes. The term interglacial complex is a short term for a tight complex of interglacials, interstadials and breviglacials, separating a complex of warm periods from the long glacial periods (euglacials). In the terrestric environment the interglacial complexes are represented by soil clusters (solcomplexes). Therein which occur interglacial and interstadial soils of different types in the loess environment separated by thin beds of loess or loess derivates (breviglacials). This article considers the mutilation and simulation of solcomplexes. Frequently, fossil solcomplexes present themselves as diminished to a few soils or to one single soil. This mutilation of solcomplexes can be due to soil convergence (soils of different warm periods — interglacials, interstadials — merge to form optically one soil), syn-solcomplex erosion or post-solcomplex erosion and sometimes to soil disguise. Conversely solcomplexes may be simulated by narrowing of soils which belong to different interglacial complexes and moreover by soil divergence (splitting of a soil of one single warm period by an interlayer of rock) or by reworked soil sediment. 相似文献
19.
The design of roadbed-abutment transition part is always a challenging problem in transportation engineering, especially in permafrost distribution zone. A new type of roadbed-abutment transition part on permafrost was presented, and long-term observation was conducted for the deformation and the thermal regime of a roadbed-abutment transition part in the constructing Qinghai-Tibet Railway. In this paper, a new structure was presented and the observed settlements both in the subgrade and the base and its dependency with the thermal regime (permafrost table) were analyzed. In conclusion the roadbed-a-butment transition method for permafrost distribution zone was evaluated. 相似文献
20.
Rock glaciers in the northern Japanese Alps: palaeoenvironmental implications since the Late Glacial
Masafumi Aoyama 《第四纪科学杂志》2005,20(5):471-484
In order to determine the palaeoclimatic and palaeo‐permafrost conditions in the northern Japanese Alps in central Japan, the ages of rock glaciers were investigated by relative age dating techniques such as weathering‐rind thickness and Schmidt hammer measurements. The results of the relative age dating suggest that the formation of the investigated rock glaciers may have started during the early phase of the Late Glacial or around the onset of the Holocene. The lower limit of current discontinuous permafrost in the northern Japanese Alps, which is indicated by the terminus of the lowest active/inactive rock glacier, lies at 2530 m a.s.l., while that of discontinuous permafrost during the Late Glacial or early phase of the Holocene, which is indicated by the terminus of the lowest relict rock glacier, lies at 2220 m a.s.l. Therefore, the lower limit of discontinuous permafrost during these periods would have been at least about 300 m lower than that of the current discontinuous permafrost. Climatic and geomorphological conditions during the Late Glacial led to a change in the environment from a glacial environment to a periglacial (permafrost) environment in the current alpine zone of the northern Japanese Alps. A large number of cirques were deglaciated and several of them were occupied by active rock glaciers around the onset of the Holocene. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献