青藏高原东部当子沟末次冰期冰川演化光释光测年   总被引：1，自引：0，他引：1  

欧先交  张彪  赖忠平  周尚哲  曾兰华 《地理科学进展》2013,32(2):262-269

青藏高原东部横断山脉沙鲁里山北支雀儿山北麓的当子沟, 保留了4 组末次冰期冰碛垄, 每组冰碛垄由若干道小冰碛垄组成, 是末次冰期多次冰川波动的理想地貌证据。为恢复该地末次冰期冰川演化历史, 从这4 组冰碛垄中采集了7 个光释光测年样品进行年代测定。等效剂量采用单片再生法(SAR)和标准生长曲线法(SGC)进行测试。年代结果显示:第1~3 组冰碛垄形成于22.4-16.5 ka BP, 属深海氧同位素2 阶段(MIS-2), 大致与全球末次盛冰期(LGM)相当。第4 组冰碛垄形成于MIS-3。MIS-3 冰川规模大于MIS-2。第1~3 组9 道次一级小冰碛垄表明, 约在22.4-16.5 ka BP期间当子沟冰川经历了9 次小波动。冰川在稍早于22.4 ka BP达到MIS-2 的最大范围, 此后规模在波动中逐渐萎缩, 可能是冰川对MIS-2 后期太阳辐射增强、气温回升的响应。最里侧冰碛垄形成于16.5 kaBP, 可能标志着该地冰消期的开始。此后, 当子沟冰川大幅快速退缩。冰川融水在最里侧冰碛垄里侧低洼谷地汇集并被阻塞形成当子错。  相似文献   

末次冰期冰碛垄系列的形态特征及其形成探讨 ——以帕隆藏布江谷地为例   总被引：1，自引：0，他引：1  

陈仁容  周尚哲  邓应彬 《冰川冻土》2012,34(4):836-847

冰碛的形态特征是气候变化的标记.以往的野外考察发现末次冰期的冰碛具有近乎统一的发育模式.选取藏东南帕隆藏布江流域的10条冰川, 研究其前方末次冰期冰川堆积特征, 以揭示其所反映的气候变化过程. 结果表明: 末次冰期MIS2形成最高大的冰碛垄, 我们称之为主冰碛垄, 这套冰碛垄示意当时冰期气候持续稳定时间最长.为主冰碛垄所部分覆盖而由其底部延伸出来的, 尚有至少两套范围更大、 但规模较小的冰碛垄, 表明MIS2之前冰期气候可能曾更加严酷, 但持续时间相对要短, 可能反映MIS4和/或MIS3的冰期气候特点.主冰碛垄内侧一直到现代冰川相当长的河谷段, 通常呈现多道冰碛垄, 规模均较主冰碛小, 它们有的不排除作为后退冰碛(recessional moraine)的可能性, 但晚冰期(YD)、 抑或H1事件应当是值得注意的.临近现代冰川末端, 一般能够辨别新冰期和小冰期冰碛垄. 因此, 藏东南这样一系列的冰川堆积, 以其形态、 范围和规模特征, 辅之以高精度的系统测年, 几乎可恢复出气候变化曲线来, 了解与全球氧同位素曲线之间的齿合关系.  相似文献   

玉龙雪山冰川沉积序列OSL定年   总被引：3，自引：3，他引：0  

何则  何元庆  张志刚  和丽华  齐翠姗  刘婧 《冰川冻土》2016,38(6):1544-1552

位于青藏高原东南缘的玉龙雪山分布有欧亚大陆纬度最低的海洋型冰川,其主峰及周边地区保存了大量清晰完整的第四纪冰川遗迹。研究该区第四纪冰川作用遗迹及其冰川作用史,具有重要的理论与实际价值。应用光释光（OSL）测年技术对玉龙雪山冰川沉积物进行了定年,结合前人研究资料,重建玉龙雪山冰川作用史。研究结果表明：玉龙雪山东麓的末次冰期冰碛物主要形成于晚更新世末次冰期最盛时期,其平均年代约在25ka,西麓末次冰期冰碛物形成年代约为50ka,对应于深海氧同位素3阶段中期（MIS3b）。而倒数第二次冰期的年代在240ka左右,处于中更新世晚期,对应于MIS8阶段,当时玉龙雪山存在多条复式山谷冰川。该研究可为玉龙雪山第四纪冰川作用历史的重新认识以及光释光测年技术在该区的应用提供基础资料。  相似文献   

黄土高原北缘中部末次冰期冰楔假型的发现及意义     

王建勇  张绪教  何泽新  赵秋晨  何祥丽  盛余应 《现代地质》2015,29(4):816-824

冰楔假型是反映古气候环境的重要标志,其蕴涵的气候地层信息对地貌演化过程具有重要的指示意义。通过对黄土高原北缘中部环江T1阶地上新发现的冰楔假型群特征的研究和光释光(OSL)测年,结果显示这些发育在冲积砂砾石中的冰楔假型的充填砂体的年代为 (30.01±3.31) ka B.P.,形成环境推测当时的年平均地温比现今要低17.7 ℃。该冰楔假型的发现也为末次冰期阶段性冻土南界的位置和变迁提供了证据。另外,据冰楔与阶地冲积物的关系推测,在冰楔形成的冰冻期河流阶地的堆积缓慢甚至停滞,在(28.64±3.13) ka B.P.之后的气候温暖期河流快速下切、T1阶地形成。这为河流阶地成因机制的探讨提供了依据,反映了气候波动对阶地发育的控制。  相似文献   

Climatic change in Western North America during the last 15,000 years: The role of changes in the relative strengths of air masses in producing the changing climates     

Stuart A. Harris 《寒旱区科学》2010,2(5):0371-0383

In the Cordillera of western North America, the influence of the Pacific Interdecadal Oscillation only affects coastal areas west of the Coast Range and the lowlands of western and southern Alaska. The rest of the area is subject to a climate controlled by the relative strengths of three distinct air masses, viz., the cold cA/cP air that is dominant in winter, the mP air bringing cool moist air over the mountains throughout the year, and the dry hot cT air from the deserts of the southwestern United States. The Arctic Front marks the boundary between the cA/cP air mass and the other two. Changes in the relative strengths of these air masses appear to explain the climatic changes documented throughout the region. Thus, in the last 30 years, the average position of the Arctic Front has moved north from about 53°N to 58°N, causing the warming in northern British Columbia and cooling south of Calgary, Alberta. This concept of changing positions of the air masses also appears to explain the mechanism behind the past climatic changes in this region. During the last Neoglacial event （c.1400-1900 A.D.）, it appears that the cA/cP air mass had strengthened enough to push the Arctic Front south of the 49th parallel. Incursions of mP air increased with localized areas of short-term heavy snowfalls resulting in small-scale advances of glaciers in these regions. This accounts for the variability in timing and extent of these glacial advances, while the resulting increased Chinook activity produced the development of a sand sea between Medicine Hat and Regina on the southern Prairies. The cT air mass was relatively weak, permitting these changes. During the maximum of the Altithermal/Hysithermal warm event （6,000 years B.P.）, the Arctic Front had retreated into the southern Yukon Territory as the cT air mass became stronger. The mP air could not move inland as easily, resulting in drier climates across the region. Prairie plants mi- grated into the southern Yukon Territory, and land snails from the eastern United States were able to migrate up the Saskatchewan River system as far as Lake Louise, Alberta. On the southern Prairies, the many small sloughs and lakes dried up. During the maximum of the Late Wisconsin Glacial event （15,000 years B.P.）, the Arctic Front had moved south to the vicinity of 30°N, while there had been a southward movement of the Zone of Intertropical Convergence from the equator to about 10°S. The mP air was also very strong and dumped enormous quantities of snow in the glaciated Canadian Cordillera, but it does not appear to have moved south any distance into the northern United States, witness the limited glaciation and widespread permafrost that developed there. Instead, there is evidence for buffering of the climatic changes in the closed basins in the northern Cordillera of the contiguous United States. The source of the cT air mass had moved south into the northern part of South America, permitting an exchange of savannah biota between the two continents. An extensive area of white dune sands inundated both savannah and forest along the inland hills in Guyana. This parallels the massive changes in African climatology during the last Ice Age （Fairbridge, 1964）. If these changes occurred each time there was a major glaciation in the Northern Hemisphere, this would explain the movement of biota from all terrestrial environments between the two American continents in the last 2 million years. A similar northward movement of climatic belts occurred in South America, with the cA air from Antarctica expanding northwards into southern Argentina and Chili. However paucity of data and the potential effects of El Ni o and the Southern Oscillation make it difficult toprovide details of the changes there in the present state of knowledge. This technique of studying the mechanisms of present-day climatic changes and applying the results to past climatic events has considerable potential for elucidating past climatic changes elsewhere in continental regions. This may prove particularly valuable in studying the Siberian anticyclone that is the main cause of the distribution of permafrost, but this will need international cooperation to be successful.  相似文献   

New age constraints for the limit of the British–Irish Ice Sheet on the Isles of Scilly     

《第四纪科学杂志》2017,32(1):48-62

The southernmost terrestrial extent of the Irish Sea Ice Stream (ISIS), which drained a large proportion of the last British–Irish Ice Sheet, impinged on to the Isles of Scilly during Marine Isotope Stage 2. However, the age of this ice limit has been contested and the interpretation that this occurred during the Last Glacial Maximum (LGM) remains controversial. This study reports new ages using optically stimulated luminescence (OSL) dating of outwash sediments at Battery, Tresco (25.5 ± 1.5 ka), and terrestrial cosmogenic nuclide exposure dating of boulders overlying till on Scilly Rock (25.9 ± 1.6 ka), which confirm that the ISIS reached the Isles of Scilly during the LGM. The ages demonstrate this ice advance on to the northern Isles of Scilly occurred at ∼26 ka around the time of increased ice‐rafted debris in the adjacent marine record from the continental margin, which coincided with Heinrich Event 2 at ∼24 ka. OSL dating (19.6 ± 1.5 ka) of the post‐glacial Hell Bay Gravel at Battery suggests there was then an ∼5‐ka delay between primary deposition and aeolian reworking of the glacigenic sediment, during a time when the ISIS ice front was oscillating on and around the Llŷn Peninsula, ∼390 km to the north. Copyright © 2017 The Authors. Journal of Quaternary Science Published by John Wiley & Sons, Ltd.

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末次冰期河流下切行为对气候变化的响应模式     

丁莹莹  张绪教  何泽新  胡道功  王超群 《现代地质》2017,31(2):394

末次冰期是距离人类最近的一次冰期,气候异常寒冷且存在高频高幅波动,河流系统如何响应冰期气候的变化值得关注与研究。基于河流系统对气候变化的敏感响应,传统的经典地貌理论认为河流下切在河流阶地形成过程中起着至关重要的作用,河流的下切行为发生在间冰期或者冰期向间冰期的过渡阶段,堆积行为发生于冰期,然而近年来最新的河流地貌研究成果表明,末次冰期河流下切较为普遍。首先对河流阶地形成的传统模式进行总结分析,认为单纯的构造驱动模式存在不合理性,气候也发挥着重要的调节作用;单一的气候变化无法驱动多级且高差较大阶地的形成,地壳抬升往往是必要因素;气候变化是引发河流堆积-下切行为转换形成河流阶地的关键因素。其次通过前人的研究案例总结出末次冰期河流下切行为响应气候变化的三种模式：(1)气候的高度不稳定性引发大规模的洪水事件驱动河流快速下切;(2)快速隆升区气候高频波动叠加构造抬升驱动河流下切;(3)沿海平原地区海平面大幅度下降驱动河流下切。这三种模式对于理解末次冰期河流系统对短尺度高频气候变化的响应以及对河流阶地成因的判断具有十分重要的指导意义。  相似文献   

雅鲁藏布江中游杰德秀古湖的发现及其意义     

韩建恩  孟庆伟  郭长宝  邵兆刚  王津  余佳  胥彪 《现代地质》2017,31(5):890

在雅鲁藏布江中游山南宽谷段发现了一套湖相沉积地层,形成时代为晚更新世晚期,为冰川阻江形成的堰塞湖沉积物。野外调查发现该套湖相地层在桑日县、乃东县、扎囊县等地均有出露,综合研究认为其为一个东起桑日县扎巴村、西至贡嘎机场附近的大型古堰塞湖泊,面积达700多km2。通过区域调查,该堰塞湖形成的湖相沉积地层在贡嘎县杰德秀镇出露最厚,厚10余m,主要由粉砂质黏土层、细砂层组成,水平纹层等湖相沉积特征明显,本研究称之为杰德秀古湖。杰德秀剖面顶部14C日历校正年龄为15 680～15 105 aBP,属于末次盛冰期。对比林芝古湖、格嘎古湖和松宗古湖等雅鲁藏布江下游堰塞湖的沉积物特征和形成时间,认为杰德秀古湖发育于末次盛冰期。沉积相特征和湖水库容量模拟分析表明,该堰塞湖发育时期,雅鲁藏布江中游山南宽谷段并未完全封闭,为一个湖水面积巨大的过水湖或吞吐湖,类似于现代过水水库。桑日县扎巴村雅鲁藏布江河谷两岸分布有冰碛物,其与雅鲁藏布江中游山南宽谷段的湖相沉积地层的时空关系指示杰德秀古湖与冰川阻塞河道有关,杰德秀古湖是由于冰川阻江形成的冰川堰塞湖。研究结果也进一步说明,雅鲁藏布江现代水系形成以前,其中游不存在面积巨大的众多古湖泊,雅鲁藏布江也不是溯源侵蚀疏干多个古湖泊而形成的,在古湖泊形成之前,雅鲁藏布江已经贯通。雅鲁藏布江流域内的古湖泊是由于气候变化、新构造运动或地震活动等原因造成河道堵塞形成的堰塞湖。  相似文献   

OSL dating of glacier extent during the Last Glacial and the Kanas Lake basin formation in Kanas River valley, Altai Mountains, China   总被引：2，自引：0，他引：2  

Xiangke Xu  Jianqiang Yang  Guocheng Dong  Liqiang Wang  Lee Miller 《Geomorphology》2009,112(3-4):306-317

The Kanas River originates on the southern slope of Youyi Peak, the largest center of modern glaciers in Altai Mountains, China. Three sets of moraines and associated glacial sediments are well preserved near the Kanas Lake outlet, recording a complex history and landscape evolution during the Last Glacial. Dating the moraines allows the temporal and spatial glacier shift and climate during the Last Glacial to be determined, and then constrains when and how the Kanas Lake basin was formed. Dating of the glacial tills was undertaken by utilizing the optically stimulated luminescence (OSL) method. Results date four samples from the three sets of moraines to 28.0, 34.4, 38.1, and 49.9 ka and one sample from outwash sediment to 6.8 ka. The Kanas Lake basin is a downfaulted basin and was eroded by glacier before 28.0 ka, and the glacial moraines blocked the glacier-melt water after the glacier retreat, which made the present-day Kanas Lake eventually form at least before 6.8 ka BP. In Altai Mountains, the glacier advance was more extensive in Marine Isotope Stage (MIS) 3 than MIS 2, probably because the mid-latitude westerlies shifted northward and/or intensified during the MIS 3, resulting in a more positive glacier mass balance. Nevertheless, the Siberian High dominated the Altai Mountains in MIS 2, resulting in a relative decrease in precipitation.  相似文献   

New findings concerning the Pleistocene Glaciation of the Leh Basin,Ladakh(34°03'N/77°38'E)     

Hermann Achenbach 《山地科学学报》2010,(4)

Like for most parts of High Asia,researches concerning the Pleistocene landscape evolution of the Leh Basin(34°03' N/77°38' E) have also left contradictions.To push this topic,three up to now unexplored Ladakh Range tributaries of the Leh Basin(Stagmo-,Arzu-and Nang-Valley) have been investigated.U-shaped profiles,transfluence passes,moraine mantled and glacially rounded peaks and ridges,roches moutonnées,glacial flank polishings and ground moraines document the former glaciation of the study area.The ice fillings of these tributaries reached a minimum thickness up to 540 m.Even at the valley outlets and on the orographic right side of the Leh Basin,the glaciation was more than 350 m thick.Based on these empirically extracted results,theoretical snow line considerations lead to the conclusion that the whole Leh Basin was filled up by a former Indus-Valley glacier.An ice injection limited to the nourishment areas of the Ladakh Range valleys could not have caused the reconstructed ice cover(down to 3236 m a.s.l.),which is proved by extended ground moraine complexes.Only an Indus ice stream network(most likely during the LGP),nourished by inflowing glaciers of the Ladakh-and Stok Range,explains the widespread existence of the glacial sediments at the outlets of the investigated valleys.  相似文献