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1.
札达盆地及周缘高山区的第四纪冰川遗迹分布广泛,类型齐全、发育连续.特征的冰碛及冰水堆积地貌有:冰水堆积平原或冰水堆积平台、冰碛丘陵等.挤压构造遗迹有:褶皱、断裂表皮构造、压坑、压裂构造、变形砾石等.ESR年代测定结果表明,冰碛形成的最大年龄为2.33Ma.依据冰碛、冰水堆积的特征、分布和形成年代等,区域冰川发育由老到新可划分出:7次冰期、6次间冰期、1次冰缘期、1次新冰期.该区是目前所知青藏高原第四纪冰川遗迹发现最多、保存最全和发育最连续的地区,为青藏高原地区的第四纪冰川演化研究、冰期的划分和对比、古气候古环境的研究,提供了重要的实际资料和依据.   相似文献   

2.
1 Introduction Hexigten is situated at the eastern part of the Inner Mongolian Plateau, south of the Da Hinggan Mountains and northwest of Chifeng City, Inner Mongolia, China. It is also at the junction of the Da Hinggan Mountians, Inner Mongolian Plateau and Yanshan Mountains. It is about 650 km north of Beijing. The geographic coordinates are 116?30'?118?20'E and 42?20'?44?10'N (Fig. 1). The elevation range is from 1100 m to 1700 m, and the highest peak (2029 m) of the Da Hinggan…  相似文献   

3.
黑沟源于东天山最大现代冰川作用中心博格达峰的南坡. 在第四纪冰期与间冰期旋回中,该流域的冰川均发生过多次规模较大的进退,在谷中留下了较为完整的冰川沉积序列. 这些冰川地形包含有重要的古气候变化信息,对其研究可重建黑沟流域的冰川演化史. 应用OSL对该流域的冰川沉积物进行定年,测定结果表明冰水沉积物（沙质透镜体）比冰碛物更适宜应用单片再生剂量（SAR）测年技术进行测定. 基于测得的年龄并结合地貌地层学原理可初步得出：晚第四纪期间,黑沟流域共发生了5次规模较大的冰川作用,分别为全新世期间的小冰期（16世纪以来冷期的冰进）与新冰期（距今3~4 ka的冰进）,末次冰期晚冰阶（MIS 2）与早冰阶（MIS 4）以及倒数第二次冰期（MIS 6）.  相似文献   

4.
Xu, X., Kleidon, A., Miller, L., Wang, S., Wang, L. & Dong, G. 2009: Late Quaternary glaciation in the Tianshan and implications for palaeoclimatic change: a review. Boreas, 10.1111/j.1502‐3885.2009.00118.x. ISSN 0300‐9483. The Tianshan mountain range has been extensively and repeatedly glaciated during the late Quaternary. Multiple moraines in this region record the extent and timing of late Quaternary glacier fluctuations. The moraines and their ages are described in three sub‐regions: eastern, central and western Tianshan. Notable glacial advances occurred during marine oxygen isotope stages (MIS) 6, 4, 3, 2, the Neoglacial and the Little Ice Age (LIA) in these sub‐regions. Glaciers in western Tianshan advanced significantly also during MIS 5, but not in eastern and central Tianshan. The local last glacial maximum (llgm) of the three sub‐regions pre‐dated the Last Glacial Maximum (LGM) and occurred during MIS 4 in eastern and central Tianshan, but during MIS 3 in western Tianshan. The spatial and temporal distribution of the glaciers suggests that precipitation (as snow at high altitude) is the main factor controlling glacial advance in the Tianshan. The late Quaternary climate in the Tianshan has been generally cold–dry during glacial times and warm–humid during interglacial times. Between neighbouring glacial times, the climate has had a more arid tendency in eastern and central Tianshan. These palaeoclimatic conditions inferred from glacial landforms indicate important relationships between the mid‐latitude westerly, the Siberian High and the Asian monsoon.  相似文献   

5.
Glacier sediment–landform associations are commonly used as interpretive and predictive tools to reconstruct the nature of past glacial events. Here we provide a regional-scale study of the sediments and landforms around the temperate North Patagonian Icefield, an area with outlet glaciers that terminate in the full range of environments possible in a temperate glacier setting (land-terminating, lake-terminating and tidewater-terminating). We present a regional-scale geomorphological map and sedimentological data collected at 11 outlet glaciers of the icefield. Key sediments and landforms include large tracts of ice-scoured bedrock, extensive sandar, terminal moraines, ice-contact glaciofluvial landforms and evidence of paraglacial slope adjustment following glacier recession. The sediments and landforms developed around the North Patagonian Icefield contrast with those previously identified at other temperate outlet glaciers in Iceland and Alaska, and we argue that this is largely a result of topographic controls on glacier terminal environment (e.g. local relief, topography and geomorphological setting).  相似文献   

6.
Quaternary glacial history of the Central Karakoram   总被引：3，自引：0，他引：3  
The Quaternary glacial history of the world's highest mountains, the Central Karakoram, is examined for the first time using geomorphic mapping of landforms and sediments, and 10Be terrestrial cosmogenic nuclide surface exposure dating of boulders on the moraines and glacially eroded surfaces. Four glacial stages are defined: the Bunthang glacial stage (>0.7 Ma); the Skardu glacial stage (marine Oxygen Isotope Stage [MIS] 6 or older); the Mungo glacial stage (MIS 2); and the Askole glacial stage (Holocene). Glaciers advanced several times during each glacial stage. These advances are not well defined for the oldest glacial stages, but during the Mungo and Askole glacial stages glacial advances likely occurred at 16, 11–13, 5 and 0.8 ka. The extent of glaciation in this region became increasingly more restricted over time. In the Braldu and Shigar valleys, glaciers advanced >150 km during the Bunthang and Skardu glacial stages, while glaciers advanced >80 km beyond their present positions during the Mungo glacial stage. In contrast, glaciers advanced a few kilometers from present ice margins during the Askole glacial stage. Glacier in this region likely respond in a complex fashion to the same forcing that causes changes in Northern Hemisphere oceans and ice sheets, teleconnected via the mid-latitude westerlies, and also to changes in monsoonal intensity.  相似文献   

7.
中国东部（105o E以东）第四纪冰川及其演化可为中国东部乃至东亚地区古气候环境重建提供基础信息及关键证据,正确认知冰川发育条件及正确运用冰川遗迹判别标准又是重建中国东部第四纪冰川及其演化的关键。中国东部中低山地第四纪期间冰川发育与否,即泛冰川论与有限冰川论的争议由来已久。近年来,山东与周边地区中低山及沿海丘陵带的“第四纪冰川”研究波澜再起。在系统地回顾中国东部第四纪冰川研究历史及新近出现争议的基础上,结合冰川发育条件、山地冰川地貌组合、判别原则与识别依据、中国东部数座中高山地存在无争议且形态清晰的冰川地形及其测年资料以及东亚古气候环境演化记录等得出：中国东部仅有台湾山地、长白山、贺兰山与太白山等数座主峰海拔超过2 500 m的中高山地保存有晚更新世以来的冰川作用地形。其余山地及海拔更低的丘陵带在第四纪期间任何一次冰川作用中均未达到与当时冰期气候相耦合的高度,不存在泛冰川作用。已报道的“冰川遗迹”皆为各种形似地质地貌现象的系统误判,其确切成因及环境意义有待深入探讨。  相似文献   

8.
Three kinds of end moraines, depending most probably on climatic conditions affecting depositional environments, are characterized: (1) fluvioglacial end moraines - built of gravels and sands froming fans superimposed on one another, and accumulated by abundant melt water during intense melting of an ice front in a comparatively warm environment; (2) 'Glacial' end moraines - built of flow tills accumulated during slow melting in a comparatively cold environment; and (3) fluvioglacial-and-glacial end moraines, the most widespread ones in Polish lowlands – built of fluvioglacial stratified gravels and sands and of glacial 'flow' deposits; zones of considerable prevalence of glacial deposits over fluvioglacial ones may probably point to comparatively cold stages during deposition, and vice versa. The question of deposition of end moraines in distal and proximal direction, and their geological and geomorphological features is also briefly discussed.  相似文献   

9.
迭山西北部位于青藏高原的东缘, 属西秦岭山脉的西段. 在海拔3 700 m以上保存有类型较为齐全的冰蚀地形(冰斗、刃脊、U形谷、悬谷、粒雪盆、鲸背岩与基岩磨光面等)与冰碛地形(侧碛垄与终碛垄). 采用野外考察、遥感影像解译与填图等方法对该区的冰川地貌分布及其特征进行了探讨. 基于研究区冰川地形分布与特征, 结合青藏高原现代的抬升速率、邻近山地冰川地形的年代学资料以及其他古环境研究成果进行综合分析得出: 该区的古冰川发育于末次冰期, 末次冰期最盛期是其最主要的形成期. 冰川最盛时面积约38 km2, 为具有暖底性质的冰帽冰川.  相似文献   

10.
山东蒙山第四纪冰川组合遗迹的发现及初步研究   总被引：1，自引：0，他引：1  
本文介绍了山东蒙山地区南坡保存的丰富而清晰的第四纪冰川遗迹,重点展示了兰溪山谷的冰石河、侧碛堤组合,并对相伴产出的擦痕、磨光面、颤痕等冰川遗迹进行了调查与测量。同时对冰石河、侧碛堤的分布、规模、物质组成、岩石特征进行了介绍。根据侧碛堤的排列位置及砾石的风化程度,初步确定为末次冰期的冰碛遗迹;对山谷两侧磨光面上的擦痕进行了测量统计,显示谷壁磨光面上擦痕的长宽比具有10:1左右的比例规律;根据侧碛最大高度法(MELM),结合对于蒙山侧碛的调查,对蒙山雪线的高度进行了估算,初步估算蒙山南坡末次冰期时的雪线高度约为700 m左右。蒙山地区这些组合冰川遗迹的发现,为中国东部第四纪冰川的研究提供了直接的证据。  相似文献   

11.
Summary The last Ice Age (Würm) glacier cover was reconstructed on the basis of standard geomorphological indicators in S Tibet between the S slope and N slope of the Himalaya by way of the Tibetan Himalaya to the Transhimalaya (28° – 29° 50' N/85° 40' – 91° 10' E). At the same time, though subject to varying density of data, the process of Late and Post-Glacial deglaciation to Neo-Galacial and Recent glacier cover was considered. Evidence of an almost total glaciation of S Tibet was found in indicators like glaciated knobs, trough valleys with pronounced flank polishings and limits of glacial scouring on nunataks, as well as in findings of erratics, lateral moraines, end moraines, and terraces of outwash plains. This total glaciation took the form of an ice-stream network and attained a thickness of at least 1200 m. Ice-free to about 87° – 86° E, the Tsangpo valley with its sander deposits occupied the gap between the glacier areas of the Tibetan and High Himalayas in the S (I 3) and those of the Transhimalaya in the N (I 2). In the light of recently glaciated Late Glacial terminal moraines and ice marginal rapms it has been possible to estimate a glacio-isostatic uplift of c. 400 m during 10 x 103 years (an average of 40 mm/year) following deglaciation. It is about 3 to 8 times greater than the tectonic uplift of the High Himalaya. The post-glacially intensified uplift of the S Tibetan Plateau by comparison with the High Himalaya is attributed to the much greater glacier burden during the Ice Age.In the area under investigation a High Glacial ELA depression (equilibrium line altitude depr.) of at least 1200 (1180) m was reconstructed for a mean altitude of about 4700 (4716) m asl. Assuming constant hygric conditions and a gradient of 0.7° C/100 m, the temperature drop at the time would have been 8.4° C. Since precipitation during the Ice Age must, if anything, have been less, a drop in summer temperature of about 10° C may be regarded as probable.  相似文献   

12.
Streamlined subglacial landforms that include drumlins in three study areas, the upper Chandra valley around Chandra Tal, the upper Spiti Valley and the middle Yunam Valley of the NW Himalaya of India were mapped and studied using geomorphic, sedimentological and geochronological methods. These streamlined subglacial landforms include a variety of morphological types, including: (i) half egg‐shaped forms; (ii) complex superimposed forms; (iii) dome‐shaped forms; (iv) inverse forms; and (v) flat‐topped symmetrical forms. Sedimentological data indicate that subglacial deformational processes are responsible for the formation of the streamlined subglacial landforms in the Chandra Tal and upper Spiti Valley study areas. In contrast, streamlined landforms in the middle Yunam Valley are the result of melt‐out and subglacial erosional processes. In the Yunam Valley study area, 11 new cosmogenic 10Be surface exposure ages were obtained for boulders inset into the crests of streamlined subglacial landforms and moraines, and also for a bedrock surface. The streamlined landforms date to 8–7 ka, providing evidence of an early Holocene valley glaciation, and older moraines date to ～17–15 and 79–52 ka, representing other significant valley glacial advances in the middle Yunam Valley. The subglacial landforms in the Chandra Valley provide evidence for a ≥300‐m‐thick Lateglacial glacier that advanced southeast, overtopping the Kunzum Range, and advancing into the upper Spiti Valley. The streamlined subglacial landforms in these study areas of the NW Himalaya highlight the usefulness of such landforms in developing glacial chronostratigraphy and for understanding the dynamics of Himalayan glaciation.  相似文献   

13.
释光测年是可对冰川地貌进行直接定年的一种测年技术,已被广泛应用于冰川沉积测年中,推动了第四纪冰川研究的深入发展。但冰川沉积释光测年还没有达到标准化的程度,实际应用中仍有不少问题需要探究,其中最受关注的是冰川沉积物释光信号晒退不完全的问题,即样品在埋藏前因曝光机会有限导致信号没有归零或仅部分归零。冰川沉积释光信号晒退程度与地貌部位和沉积环境密切相关。冰川沉积释光采样需注意几个方面：（1）详细的地貌学和沉积学调查及对采样点的选择;（2）较适合释光测年的冰水沉积和冰缘风成沉积采集及其与冰川作用期次的联系;（3）冰碛夹层中的冰水砂透镜体的选取;（4）冰碛垄采样时垂直与水平方向上的考量;（5）岩石释光测年的发展使砾石成为当前第四纪冰川释光测年采样的一种选择。室内进行释光等效剂量测试时,也有几个关键的选择：（1）粗颗粒石英光释光测年是末次冰期以来冰川作用的首选方法;（2）如果样品年代老于石英测年上限,或者石英不适合测试,则可考虑钾长石后红外高温释光测年方法;（3）单颗粒、小测片和岩石释光埋藏测年技术可以鉴别样品的晒退情况,是目前最适合冰川沉积释光测年的几种选择;（4）如有条件,尝试用不同矿物、不同粒径、不同方法进行测试对比和交叉检验。要获得第四纪冰川释光测年的最佳年代学结果,地貌学、沉积学和年代学的结合是非常必要的。  相似文献   

14.
Dortch, J. M., Owen, L. A., Caffee, M. W. & Brease, P. 2009: Late Quaternary glaciation and equilibrium line altitude variations of the McKinley River region, central Alaska Range. Boreas, 10.1111/j.1502‐3885.2009.00121.x. ISSN 0300‐9483 Glacial deposits and landforms produced by the Muldrow and Peters glaciers in the McKinley River region of Alaska were examined using geomorphic and 10Be terrestrial cosmogenic nuclide (TCN) surface exposure dating (SED) methods to assess the timing and nature of late Quaternary glaciation and moraine stabilization. In addition to the oldest glacial deposits (McLeod Creek Drift), a group of four late Pleistocene moraines (MP‐I, II, III and IV) and three late Holocene till deposits (‘X’, ‘Y’ and ‘Z’ drifts) are present in the region, representing at least eight glacial advances. The 10Be TCN ages for the MP‐I moraine ranged from 2.5 kyr to 146 kyr, which highlights the problems of defining the ages of late Quaternary moraines using SED methods in central Alaska. The Muldrow ‘X’ drift has a 10Be TCN age of ～0.54 kyr, which is ～1.3 kyr younger than the independent minimum lichen age of ～1.8 kyr. This age difference probably represents the minimum time between formation and early stabilization of the moraine. Contemporary and former equilibrium line altitudes (ELAs) were determined. The ELA depressions for the Muldrow glacial system were 560, 400, 350 and 190 m and for the Peters glacial system 560, 360, 150 and 10 m, based on MP‐I through MP‐IV moraines, respectively. The difference between ELA depressions for the Muldrow and Peters glaciers likely reflects differences in supraglacial debris‐cover, glacier hypsometry and topographic controls on glacier mass balance.  相似文献   

15.
Glacier thermal regime is shown to have a significant influence on the formation of ice‐marginal moraines. Annual moraines at the margin of Midtdalsbreen are asymmetrical and contain sorted fine sediment and diamicton layers dipping gently up‐glacier. The sorted fine sediments include sands and gravels that were initially deposited fluvially directly in front of the glacier. Clast‐form data indicate that the diamictons have a mixed subglacial and fluvial origin. Winter cold is able to penetrate through the thin (<10 m) ice margin and freeze these sediments to the glacier sole. During winter, sediment becomes elevated along the wedge‐shaped advancing glacier snout before melting out and being deposited as asymmetrical ridges. These annual moraines have a limited preservation potential of ～40 years, and this is reflected in the evolution of landforms across the glacier foreland. Despite changing climatic conditions since the Little Ice Age and particularly within the last 10 years when frontal retreat has significantly speeded up, glacier dynamics have remained relatively constant with moraines deposited via basal freeze‐on, which requires stable glacier geometry. While the annual moraines on the eastern side of Midtdalsbreen indicate a slow steady retreat, the western foreland contains contrasting ice‐stagnation topography, highlighting the importance of local forcing factors such as shielding, aspect and debris cover in addition to changing climate. This study indicates that, even in temperate glacial environments, restricted or localised areas of cold‐based ice can have a significant impact on the geomorphic imprint of the glacier system and may actually be more widespread within both modern and ancient glacial environments than previously thought.  相似文献   

16.
高寒地区形态独特的冰川侵蚀与沉积地形是过去冰川变化最直接的证据,包含有重要的古气候环境变化信息。根据山地冰川沉积序列,通常将分布在现代冰碛地形外围形态较完好的多列冰碛垄的形成时间推定为小冰期。小冰期冰进的时间与规模是理解与重建近千年以来古气候环境变化的基础及较准确预测未来气候环境变化的关键。本研究应用10Be暴露测年技术对唐古拉山东段布加岗日南坡拥曲河源区西（主）谷与东（悬）谷中基于地貌关系与沉积序列推定为小冰期的第一套冰碛垄MW1与ME1进行定年。测得MW1冰碛垄4个样品的10Be年龄分别为（155±23） a、（197±27） a、（218±26） a和（273±31） a;ME1冰碛垄3个样品的10Be年龄分别为（262±30） a、（186±28） a和（131±25） a。使用P-CAAT法分析得出它们的年龄为（203±52） a（n=4）和（162±58） a（n=3）。地貌关系、沉积序列、冰碛垄的形态特征、土壤发育与植被覆盖以及测年结果等共同表明拥曲河源区西谷与东谷中的第一套冰碛垄形成于小冰期。结合周边地区的研究成果及古气候环境代用指标可以推断降温是这次冰进的主因。  相似文献   

17.
This paper presents a revised glacial chronology for the Lahul Himalaya and provides the most detailed reconstruction of former glacier extents in the western Himalayas published to date. On the basis of detailed geomorphological mapping, morphostratigraphy, and absolute and relative dating, three glaciations and two glacial advances are constrained. The oldest glaciation (Chandra glacial stage) is represented by glacially eroded benches and drumlins (the first to be described from the Himalaya) at altitudes of >4300 m and indicates glaciation on a landscape of broad valleys that had minimal fluvial incision. The second glaciation (Batal glacial stage) is represented by highly weathered and disssected lateral moraines and drumlins representing two phases of glaciation within the Batal glacial stage (Batal I and Batal II). The Batal stage was an extensive valley glaciation interrupted by a readvance that produced superimposed bedforms. Optically stimulated luminescence (OSL) dating, indicates that glaciers probably started to retreat between 43400 ± 10300 and 36900 ± 8400 yr ago during the Batal stage. The Batal stage may be equivalent to marine Oxygen Isotope Stage 4 and early Oxygen Isotope Stage 3. The third glaciation (Kulti glacial stage), is represented by well-preserved moraines in the main tributary valleys that formed due to a less-extensive valley glaciation when ice advanced no more than 12 km from present ice margins. On the basis of an OSL age for deltaic sands and gravels that underlie tills of Kulti age, the Kulti glaciation is younger than 36900 ± 8400 yr ago. The development of peat bogs, having a basal age of 9160 ± 70 14C yr BP possibly represents a phase of climatic amelioration coincident with post-Kulti deglaciation. The Kulti glaciation, therefore, is probably equivalent to all or parts of late Oxygen Isotope Stage 3, Stage 2 and early Stage 1. Two minor advances (Sonapani I and II) are represented by small sharp-crested moraines within a few kilometres of glacier termini. On the basis of relative weathering, the Sonapani advance is possibly of early mid-Holocene age, whereas the Sonapani II advance is historical. The change in style and extent of glaciation is attributed to topographic controls produced by fluvial incision and by increasing aridity during the Quaternary. © 1997 John Wiley & Sons, Ltd.  相似文献   

18.
Accurately determining how far south Quaternary glaciers existed in eastern China has important implications for understanding global Quaternary climate. In this study, we provide evidence for a colder paleoclimate in the late Pleistocene of the Laoshan range on the eastern Shandong Peninsula at 36°05′–36°19′N latitude, through documentation of erosional and depositional landforms that were possibly formed by glaciation. We integrate field observations documenting and mapping the existence of typical glacial cirques, glacial horns, moraines, arêtes, tarn lakes, and other paleoglacial features in Mt. Laoshan, with a detailed digital elevation model (DEM) created in an ArcGIS environment, merged with Landsat ETM + imagery to document the spatial relations of these features. Other features that may or may not be glacial in origin include large boulder fields (that could be moraines or debris avalanches), and potholes (that could have formed beneath glaciers or in river systems). Additionally, some features previously interpreted as glacial features are here re-interpreted as weathering-related phenomena. Although some of these features alone provide only weak to moderate evidence for glaciation, together the suite of indicators provides strong evidence for sea-level glaciation at 36°N in the late Pleistocene of eastern China. We further integrate the evidence of glaciation with the late Pleistocene paleogeography and climate, and suggest that the glaciers formed as a result of orographic effects from moist monsoonal breezes crossing a paleolake developed in North China then rising over Mt. Laoshan and dropping their moisture there, with a wide desert formed on the leeward side of the mountains.  相似文献   

19.
The glacial geomorphology of Teesdale and the North Pennines uplands is analysed in order to decipher: a) the operation of easterly flowing palaeo-ice streams in the British-Irish Ice Sheet; and b) the style of regional deglaciation. Six landform categories are: i) bedrock controlled features, including glacitectonic bedrock megablocks or ‘rubble moraine’; ii) discrete mounds and hills, often of unknown composition, interpreted as weakly streamlined moraines and potential ‘rubble moraine’; iii) non-streamlined drift mounds and ridges, representing lateral, frontal and inter-ice stream/interlobate moraines; iv) streamlined landforms, including drumlins of various elongation ratios and bedrock controlled lineations; v) glacifluvial outwash and depositional ridges; and vi) relict channels and valleys, related to glacial meltwater incision or meltwater re-occupation of preglacial fluvial features. Multiple tills in valley-floor drumlin exposures indicate that the subglacial bedform record is a blend of flow directions typical of areas of discontinuous till cover and extensive bedrock erosional landforms. Arcuate assemblages of partially streamlined drift mounds are likely to be glacially overridden latero-frontal moraines related to phases of “average glacial conditions” (palimpsests). Deglacial oscillations of a glacier lobe in mid-Teesdale are marked by five inset assemblages of moraines and associated drift and meltwater channels, named the Glacial Lake Eggleshope, Mill Hill, Gueswick, Hayberries and Lonton stages. The Lonton stage moraines are thought to be coeval with bedrock-cored moraines in the central Stainmore Gap and likely record the temporary development of cold-based or polythermal ice conditions around the margins of a plateau-based icefield during the Scottish Readvance.  相似文献   

20.
云南省东北部拱王山第四纪冰川遗迹研究   总被引：7，自引：6，他引：7  
况明生  李吉均 《冰川冻土》1997,19(4):366-372
云南省东北部的拱王山海拔３１００ｍ以上的山地发生过第四纪冰川作用，典型的冰川遗迹集中分布在轿子山峰附近和妖精塘－牛洞坪两个地区，遗存的冰川地貌主要有冰斗，冰蚀岩盆和侧碛堤。根据冰川地貌的组合特征，以及它们生成的先后顺序，将拱王山第四纪冰川作用划分为末次冰期的倒数第二期冰期。  相似文献   

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