西藏终碛湖溃决形式研究

西藏终碛湖众多,一旦发生溃决,将造成巨大损失。冰湖溃决机制的研究对冰湖溃决预测和溃后灾害评估是十分必要的。将冰湖终碛堤视为天然堆石坝,用水力学和土力学理论研究冰湖溃决的力学机制。重点研究溢流型溃决形式和管涌型溃决形式,根据野外观测数据和前人的研究,发现溢流型溃决的溃口多呈梯形或圆弧状形,对比真实数据发现溃口顶宽与坝高的关系,并且所有冰川终碛堤都表现为局部溃决。通过实地考察、取样分析,判断光谢措终碛堤的可能渗透破坏形式。     

海螺沟现代冰碛物中的宇生核素10Be浓度分析

尽管许多学者都意识到继承性宇生核素对冰碛物暴露年代测量可能会带来一定的误差,然而影响究竟有多大,还缺乏对现代冰碛物宇生核素浓度的研究。对采自贡嘎山海螺沟冰川现代冰碛物碎屑和冰碛砾石的本地生宇生核素 10 Be 浓度的分析表明,即使是海洋性冰川(暖底冰川),其冰碛物碎屑和冰碛砾石都残留一定量的本地生宇生核素; 即使是具有明显磨蚀痕迹的现代冰碛砾石表面,也残留一定量的本地生宇生核素。因此,进行宇生核素测年时要给予充分的重视。当然,其冰碛物基质和具有明显磨蚀痕迹的现代冰碛砾石表面的本地生宇生核素 10 Be 浓度比较低,一般不大于2×104atoms/g。对暴露年代的影响一般不大于0.61ka。尽管其适用范围还有待于更多的研究结果的进一步证实,但是却为残留影响的研究提供了一个研究的实例和一组可以参考的数据。     

北极新奥尔松全新世冰碛物物理化学特征及环境意义

冰碛物是全球的一个主要粉尘源,联系着全球气候、大气气溶胶、海洋元素和生产力的变化。过去对粉尘,特别是沙漠、黄土的研究主要集中在中纬度地区,但对来自高纬度的冰川粉尘研究较少。为了解现代高纬度冰缘环境下冰川作用、搬运作用和化学风化对冰碛物的物理化学性质的影响,本文以北极新奥尔松Austre Lovénbreen冰川（简称A冰川,下同）深度小于5cm的冰碛物（包括小冰期冰碛物和冰沼土）≤2mm组分为对象,测定了小冰期（Little Ice Age,简称LIA）冰碛物和冰沼土的粒径、磁化率以及元素组成。研究表明：1）A冰川冰碛物粒径组成以砂级为主（>63μm）、粉砂级次之（2~63μm）、粘粒最少（ < 2μm）。A冰川冰碛物大部分呈双峰或多峰特征,LIA冰碛物典型双峰峰值为10~30μm和100~200μm;冰沼土为30~60μm和300~450μm。近岸LIA冰碛物和冰沼土相对冰川末端LIA冰碛物具有较粗的平均粒径及较高的正偏度,表明其在沉积之后受搬运作用影响损失了细组分。2）A冰川冰碛物磁化率介于5.5×10^-8~11.4×10^-8m³/kg之间,平均值为7.7×10^-8m³/kg。LIA冰碛物磁化率与总铁含量呈正相关,主要受母岩和搬运作用制约,未受成壤作用影响。3）A冰川冰沼土与LIA冰碛物相比,富Si,但贫Al、Fe、K、Ca、Mg等元素;LIA冰碛物平均化学组成与洛川黄土和上部大陆地壳（Upper Continental Crust,简称UCC）非常接近。A冰川冰碛物CIA平均值为58.57,反映冰缘环境较弱的化学风化条件。A冰川冰碛物CIA值集中分布在UCC至黄土的平均化学组成风化趋势线上,证明了黄土粉尘起源于由一系列的冰川和高山作用产生的沉积物的可能性。分析结果表明,在弱风化的冰缘环境下,CIA值能从整体上反映LIA冰碛物和冰沼土的化学风化差异,但对沉积年龄小的LIA冰碛物而言,搬运作用引起的粒度组成差异和相应的不同矿物类型和含量的改变或是CIA值变化的主要原因。

     

CRITICAL HYDROLOGIC CONDITIONS FOR OVERFLOW BURST OF MORAINE LAKE

1OVERFLOWBURSTOFMORAINELAKEFloodwater and debris flow caused by glacial lake burst is an important land process and a serious moun-tain disaster in glacial area. Glacial lakes with burst can divided into the glacier-obstructed lake (ice dam lake) and the terminal moraine lake (XU and FENG, 1988). Typical burst of ice dam lake happens in the modern glacier area of the upper reaches of the Kele-qing River in Uygur Autonomous Region of Xinjiang (WANG, 1990). But most of burst gla…     

祁连山摆浪河全新世冰量变化初探

采用祁连山老虎沟12号冰川2009年RTK测量生成的数字高程模型(DEM), 建立现代冰川表面横截面拟合的二次方程, 结合差分GPS测量的冰碛垄形态, 运用于祁连山摆浪河上游14号冰川和16号冰川全新世以来冰量变化的估算. 结果表明: 新冰期以来冰储量减少0.38 km³, 小冰期以来14号冰川和16号冰川的冰储量分别减少0.016 km³和0.047 km³; 根据祁连山全新世各个时期最大冰川范围的时间, 估计了全新世以来14号和16号冰川冰储量的减少速率, 新冰期以来为12.2×10^-5~15.0×10^-5 km³·a^-1, 小冰期以来分别为4.0×10^-5~5.3×10^-5 km³·a^-1, 11.75×10^-5~15.7×10^-5 km³·a^-1.     

The Glacial History of Landscape in the Batura Muztagh, NW Karakoram

The most recent glacial history of the Bar Valley on the Batura south side of the great Karakorum main ridge shows a marked retreat of the Kukuar and Baltar glaciers since 1915 by 8 km. This tendency is continuing. A great lateral moraine (GLM), which shows the latest, historical maximum postglacial stage, is accompanied by a higher level, which reflects a neoglacial glacier level whose ice margins no longer exist. An earth-pyramid moraine rising high above the glacier, as also occurs on the northern declivities of the Batura, does not mark a specific level, but bears witness to a valley-filling glacier, for which further indicators can be found along the valley flank. In the gorge-like narrow trough valley, the flanks of which are covered by steep debris cones originating from the postglacial, numerous former glacial characteristics contrast with the current glaciation of the far retreated Kukuar and Baltar glaciers. Moraine material found at the valley outlet at Chalt and also on the Talmutz pass demonstrates complete ice filling of the Bar valley, also supported by the Daintar glacier. From a glacial geomorphological perspective, this confirms a late to high glacial connection of the Bar glacier to a Hunza glacier, as postulated by Kuhle (2005).     

Glacial geomorphology in Utsjoki, Finnish Lapland proposes Younger Dryas fault-instability

Northern Fennoscandia has experienced high-magnitude postglacial fault (PGF) events, yet the role of seismic tremors in subglacial deformations and meltwater discharge has remained obscure. We studied glacial geomorphology in Utsjoki, Finnish Lapland, an area characterized by the Utsjoki drumlin field fanning out north and northeast to the Younger Dryas End Moraines (YDEMs) in northern Norway. Paleolandslides were common on fells (i.e. mountains shaped by Pleistocene glaciations) and were formed in nunatak position evidencing fault-instability in app. 11,900 calibrated (cal) BP. An anastomosing network of eskers was found throughout Utsjoki, and was probably generated through short-lived sliding bed stages during the discharge of subglacial lake(s). The formation of networks is different from time-transgressive evolution of single-ridged eskers in arborescent (treelike) systems. The most probable triggering mechanism for the meltwater outburst(s) was an earthquake tremor(s) associated with fault-instability during the late and post-Younger Dryas (YD). The alignment of the esker network was inconsistent with parallel-to-iceflow streamlining and the eskers erode or superimpose drumlins. Hence the esker network post-dates the streamlining. In some cases, hummocky (Pulju) moraine was observed to coexist with esker network and peculiar ‘kettle’ and ‘liquefaction’ features. We propose that glacio-seismotectonic events contributed not only to landslides but were also the primary force behind subglacial evolution of esker networks and possibly even hummocky moraine.     

Outburst mechanism of Yindapu Glacial Lake in Tibet

At present, the mechanism research on glacial lake outburst mainly focuses on the ice quake and ice landslide, etc. To some glacial lakes, the seepage deformation is the dominant factor in outburst process. Taking the Yindapu Glacial Lake in Tibet as an example, using SEEP/W module of FEM software （ GEO-STUDIO）, the authors analyzed seepage stability of terminal moraine ridge dam. The leading role of seepage deformation in some glacial lake outburst mechanism is proposed and proved.     

Occurrence,evolution and ice content of ice-debris complexes in the Ak-Shiirak,Central Tien Shan revealed by geophysical and remotely-sensed investigations

Rock glaciers and large ice-debris complexes are common in many mountain ranges and are especially prominent in semi-arid mountains such as the Andes or the Tien Shan. These features contain a significant amount of ice but their occurrence and evolution are not well known. Here, we present an inventory of the ice-debris complexes for the Ak-Shiirak, Tien Shan's second largest glacierised massif, and a holistic methodology to investigate two characteristic and large ice-debris complexes in detail based on field investigations and remote sensing analysis using Sentinel-1 SAR data, 1964 Corona and recent high resolution stereo images. Overall, we found 74 rock glaciers and ice-debris complexes covering an area of 11.2 km² (3.2% of the glacier coverage) with a mean elevation of about 3950 m asl. Most of the complexes are located south-east of the main ridge of Ak-Shiirak. Ground penetrating radar (GPR) measurements reveal high ice content with the occurrence of massif debris-covered dead-ice bodies in the parts within the Little Ice Age glacier extent. These parts showed significant surface lowering, in some places exceeding 20 m between 1964 and 2015. The periglacial parts are characterised by complex rock glaciers of different ages. These rock glaciers could be remnants of debris-covered ice located in permafrost conditions. They show stable surface elevations with no or only very low surface movement. However, the characteristics of the fronts of most rock glacier parts indicate slight activity and elevation gains at the fronts slight advances. GPR data indicated less ice content and slanting layers which coincide with the ridges and furrows and could mainly be formed by glacier advances under permafrost conditions. Overall, the ice content is decreasing from the upper to the lower part of the ice-debris complexes. Hence, these complexes, and especially the glacier-affected parts, should be considered when assessing the hydrological impacts of climate change. © 2018 John Wiley & Sons, Ltd.