贡嘎山海螺沟冰川沉积特征与冰下过程研究

贡嘎山海螺沟冰川是典型的海洋性冰川,粒度分析表明:冰下融出碛的细粒组分中粉砂占优势,压碎组分与磨碎组分界线在0.5 mm附近,说明其经历充分的研磨细化.与西藏枪勇冰川和天山乌鲁木齐河源冰川的矿物组成和化学成分对比,海螺沟冰川沉积物的经历的化学风化作用更强,即海洋性冰川冰下化学作用比大陆性冰川活跃.显微层理构造、正粒序层理和沉积透镜体反映海洋性冰川底部存在周期性沉积机制和明显的流水作用,显微滞碛是较常见的冰下融出碛类型.沉积物中显微褶皱和断层等反映海洋性冰川强烈滑动、剪切变形过程机制.     

青藏高原冰川底部滑动估算方法研究:进展、问题与展望

冰川底部滑动是冰川运动重要的组成部分,是冰川动力过程的底部边界条件.底部滑动速度的估算,对于研究青藏高原及周边地区冰川运动规律、冰川内部应力分布和冰川异常变化机制等具有重要意义.系统总结了冰川底部滑动速度的影响因素及其估算模型的发展现状,其模型从单纯考虑底部剪切应力与冰床特性的关系逐渐扩展到考虑底部有效压力和冰下水文过程等综合影响,剖析了现有模型的结构和功能.进而分析了现有模型存在的主要问题和挑战,为进一步完善模型提供参考.未来冰川底部滑动研究需基于遥感大数据、新技术等进一步强化观测,着重耦合冰下水文过程的影响,进而促进气候变化—冰川物质平衡—冰川动力学响应过程的集成研究.     

青藏高原东南部贡嘎山海螺沟冰川冰下沉积物形成与变形

冰岩界面的冰川动力学是冰川系统的重要组成部分, 海螺沟冰川地处温暖湿润的海洋环境, 冰川运动速度较快, 冰川底部接近压融点, 是研究冰下过程的较理想地点. 在海螺沟冰川大型磨光面上浅显侵蚀坑内发现了碎屑物质. 对碎屑物质理化特征研究表明: 粒度特征、地球化学与石英砂SEM 分析表明沉积在冰岩界面上的物质来自于冰川底部的底碛层, 而不是冰上环境的产物. 偏光显微镜下观察到的冰下沉积物呈现出一系列塑性变形(微旋转、褶皱)和脆性变形(线性结构、支撑结构、断层)微观结构和构造. 两种变形结构的存在是碎屑物质在形成过程中其含水量波动情况的反映. 冰下碎屑物质是冰下融出、滞碛作用的共同产物. 在整个冰下碎屑物质形成与变形过程中, 由于冰下水系季节性变化带来的冰岩界面上冰川融水含量的波动起了决定性作用.     

萨吾尔山木斯岛冰川厚度特征及冰储量估算

冰下地形与冰川体积的估算对冰川水资源研究具有重要意义.以萨吾尔山木斯岛冰川为研究对象,利用Landsat影像数据、探地雷达(ground penetrating radar,简称GPR)冰川厚度数据以及差分GPS数据,分析模拟了萨吾尔山木斯岛冰川横纵剖面的厚度分布特征,采用多种插值方法比较分析,得到木斯岛冰川冰舌区的厚度分布图,初步估算了该冰川的冰储量.结合数字高程模型数据及冰川厚度分布图,绘制了木斯岛冰川冰舌区冰床地形图.研究表明,两个横剖面的冰川槽谷形态存在较大的差异.横剖面B1-B2有典型的“U”型地形发育,冰川厚度可达116.4 m;C1-C2横剖面底部地形比较平缓,冰川厚度分布较均匀,平均在70~90 m.纵测线A1-A2冰下地形成阶梯状分布,纵剖面冰体平均厚度约为80.89 m,最大冰体厚度为122.67 m.木斯岛冰川的冰床地形图与该冰川的冰厚度等值线图形成明显对比.在海拔3 240 m和3 280 m处存在明显的冰斗地形地貌.初步估算木斯岛冰川冰舌区的平均厚度和冰储量分别为60.5 m和0.195 km3.与传统计算冰储量的方法相比,利用GPR测量得到的冰川厚度数据来插值计算冰储量的方法,具有更高的准确性.      

峡东南华系南沱组底部冰川底碛沉积特征及其意义

峡东地区是我国原震旦系标准剖面所在地,该地区南沱组直接覆盖莲沱组之上,中间缺失下冰期和间冰期地层,究其原因尚不清楚.通过聚焦南沱组与莲沱组接触层位,利用现代冰川沉积物研究方法开展系统沉积学研究,结果表明:九龙湾周缘南沱组和莲沱组之间存在一层紫红色混合杂砾岩层,其内部砾石定向性、形态、磨圆、岩性以及显微构造与之上南沱组典型灰绿色杂砾岩区别明显,青林口剖面南沱组底部发育微观尺度上的变形沉积构造.表明南沱组底部与莲沱组接触层位为冰川底碛成因,而南沱组主体为冰海沉积成因.证明峡东地区南沱组与莲沱组之间地层缺失是由盛冰期的冰川剥蚀所致,南沱组可能仅代表了盛冰期之后冰消期的沉积记录.      

天山乌鲁木齐河源3号冰川沿剪切面内碛的成因——据粒度分布和石英颗粒表面特征的分析(英文)

3号冰川消融区下部有4个主要的剪切面,这些剪切面伴随着5—40厘米厚的富含岩屑冰。在每个富含岩屑冰区域采集了内碛样品以便考察它的特征和来源。 冰内碛巨砾具有极其明显的棱角状,泥沙和粘土的含量低于温冰川磨蚀过程产生的冰碛的泥沙和粘土含量。用电子扫描显微镜观察到的石英颗粒表面特征表明: (1)所有颗粒都具有典型的“冰川作用”特征。 (2)5—20%的颗粒显示出在“冰川作用”特征之上附加有二氧化硅溶解沉淀物特征。 (3)水下机械作用的标志如撞击痕和磨圆现象很少观察到。(1)意味着石英颗粒是机械研磨或挤压作用的产物;(2)和(3)意味着某些颗粒在被挤压后曾在水中停留过,但颗粒并没有在湍流水流中被搬运。 这些结果暗示3号冰川内碛主要是由冰川底部挤压或拔蚀作用所产生,而不是磨蚀作用的产物。在内碛产生的冰川底部,温度一直或以前保持在融点,但水量小于温冰川底部的水量。     

A Direct Erosion Evidence of Quaternary Glaciation-Chatter Marks Found in Mt.Lushan, Shandong Province, East of China

本文首次报道了在山东鲁山南坡山谷发现混合岩表面的颤痕.颤痕是冰川底部携带的岩石碎块在下伏基岩表面刮凿而形成的一系列弧形裂隙,颤痕的弧形突出方向与冰川运动方向一致,而裂隙也是向下游方向深入基岩内部,其中突出的中间部位裂隙最深,向两端逐渐变浅直至消失.作者探讨了颤痕的形成机理,认为:颤痕相当于主剪切面上的伴生构造——R剪切面,在剖面上看就是一系列雁列式排列的R面,它不仅是冰川在基岩上运动留下的重要证据,而且还能指示冰体的运动方向.除了颤痕之外,在鲁山山麓还分布着大量的冰碛地貌:巨漂砾、冰碛堤等,在鲁山山脊上还见有典型的壶穴、冲刷槽等冰川融水侵蚀标志.这些标志与颤痕一起构成了强大的证据群,揭示了中国东部曾经发育过第四纪冰川的历史.中国东部是否发育过第四纪冰川?地学界已经争论了80多年,而颤痕的发现为进一步肯定中国东部存在第四纪冰川活动提供了最直接的证据.     

末次冰消期气候转型对青藏高原东部地震活动的影响

探讨构造和气候在地质演化过程中的耦合作用一直是地球系统科学研究的热点.通过对青藏高原东部古地震和古气候资料的收集和分析,发现18–15 ka期间湖相沉积存在大量且强烈的地震成因软沉积物变形构造或地震事件,可能是末次冰消期以来青藏高原大陆冰川(或冰帽)快速消融和冰川剥蚀卸载作用,引起中上地壳应力卸载和均衡反弹,以及冰川融水引起地下水波动,导致区域应力场变化和断层活动增强,诱发了区域频繁的地震所致.本研究为更好地理解晚第四纪青藏高原东部的地震活动、气候变化和地貌过程具有一定的启示意义.     

大别山地区存在第四纪冰川吗?

为了有效保护地质遗迹,并开展地质科普教育,避免以讹传讹,本文针对大别山南麓湖北省罗田县河铺镇与九资河镇交界处所发现的"冰臼群"进行了调查和研究。通过对"冰臼群"分布和形态特征分析,认为大别山地区河谷中的"冰臼群"系由水流侵蚀作用形成,其分布受构造(节理)控制,其改造和破坏受河流下切作用的强烈影响。因此,该"冰臼群"是流水侵蚀成因的壶穴而非冰川成因的冰臼。从目前的证据看,大别山地区并不存在第四纪冰川。     

广东揭西发现世界罕见的冰臼群

最近,著名地质学家中国地质科学院地质研究所韩同林教授,在广东省揭西县发现了世界上罕见的冰臼群．冰臼群是古冰川融化后的冰融水,携带石块对下伏基岩或一些巨大的岩块（冰川漂砾）进行强烈冲击、研磨形成的．它是古冰川存在的有力证据之一,是古气候、古环境变迁的重要见证．揭西冰臼群发现于揭西县城之东南的石肚溪内,位于北纬２３°２３′,东经１１５°５２′,海拔约３６～３００ｍ．石肚溪是当地一条名不经传的小河,溪流自西南向东北方向流动,全长２０多ｋｍ,．目前已发现的冰臼群较集中的最少有１１处,且均分布于河谷之中,…     

Lake stratigraphy implies an 80 000 yr delayed melting of buried dead ice in northern Russia

Sediment cores from lakes Kormovoye and Oshkoty in the glaciated region of the Pechora Lowland, northern Russia, reveal sediment gravity flow deposits overlain by lacustrine mud and gyttja. The sediments were deposited mainly during melting of buried glacier ice beneath the lakes. In Lake Kormovoye, differential melting of dead ice caused the lake bottom to subside at different places at different times, resulting in sedimentation and erosion occurring only some few metres apart and at shifting locations, as further melting caused inversion of the lake bottom. Basal radiocarbon dates from the two lakes, ranging between 13 and 9 ka, match with basal dates from other lakes in the Pechora Lowland as well as melting of ice‐wedges. This indicates that buried glacier ice has survived for ca. 80 000 years from the last glaciation of this area at 90 ka until about 13 ka when a warmer climate caused melting of permafrost and buried glacier ice, forming numerous lakes and a fresh‐looking glacial landscape. Copyright © 2003 John Wiley & Sons, Ltd.     

Jens Esmark's mountain glacier traverse 1823 − the key to his discovery of Ice Ages

The discovery of Ice Ages is one of the most revolutionary advances made in the Earth sciences. In 1824 Danish‐Norwegian geoscientist Jens Esmark published a paper stating that there was indisputable evidence that Norway and other parts of Europe had previously been covered by enormous glaciers carving out valleys and fjords, in a cold climate caused by changes in the eccentricity of Earth's orbit. Esmark and his travel companion Otto Tank arrived at this insight by analogous reasoning: enigmatic landscape features they observed close to sea level along the Norwegian coast strongly resembled features they observed in the front of a retreating glacier during a mountain traverse in the summer of 1823. Which glacier they observed up close has however remained a mystery, and thus an essential piece of information in the story of this discovery has been missing. Based on previously unknown archive sources, supplemented by field study, I here identify the key locality as the glacier Rauddalsbreen. This is the northernmost outlet glacier from Jostedalsbreen, the largest glacier in mainland Europe. Here the foreland exposed by glacier retreat since the Little Ice Age maximum around AD 1750 contains a rich collection of glacial deposits and erosional forms. The point of enlightenment is more precisely identified to be a specific moraine and its distal sandur at 61°53′26″N, 7°26′43″E. In memory of Esmark's travel companion who possibly was the first to realise the analogy, it is proposed to name this moraine Otto Tank's Moraine, a pendant to the already famous Esmark Moraine at Forsand by the sea.     

万州安乐寺滑坡前缘松散堆积体成因与防治对策

逐一分析了安乐寺滑坡前缘西溪铺、农机技校松散堆积体的144个勘探钻孔,根据土体物质成分进行分层并对其成因进行判断;对相邻钻孔的土层进行比较,将相同的土层连接起来,绘制工程地质剖面图;将工程地质剖面图进行综合对比分析,探讨每一土层的连续性、延伸性．按照“钻孔-剖面-成层”的研究方法,对安乐寺滑坡前缘松散堆积体的特征及成因进行详细的研究．研究结果表明：安乐寺滑坡前缘松散堆积体是以安乐寺滑坡前部的滑动解体作用为主,包括残积、坡积、冲积等共同作用形成的．前缘松散堆积体中存在多个滑动面,滑动面平直、光滑,可以分为2种类型：一类是中深层滑动面,数量较少,规模大;另一类是浅层滑动面,数量较多,规模小．滑动面的这种分布规律反映了前缘松散堆积体是一个长期的不连续的变形体．最后,考虑松散堆积体下伏卵石砂土层地质结构,对松散堆积体防治措施进行了探讨,认为安乐寺前缘松散堆积体采用抗滑桩支挡结合地表排水与护坡等措施进行治理是适宜的,但抗滑桩嵌固段必须深入到卵石砂土层以下稳定的基岩中,以避免抗滑桩随卵石砂土层产生整体位移．     

川藏交通廊道林波段冰川泥石流发育动态演化分析及监测预警方案

川藏交通廊道沿线山高谷深,地层岩性多变,新构造运动活跃,气候恶劣复杂,导致滑坡、崩塌、泥石流、冰湖溃决洪水等灾害极其发育,对铁路施工及运营带来严重影响.林芝-波密段就是典型地质灾害高发区域,常年受到冰川泥石流的影响,是川藏交通廊道重大灾害防治的难点区段.虽然目前在单沟尺度上对冰川泥石流的形成条件、影响因素、物源性质取得了一定的认识,但对于川藏交通廊道沿线不同类型的冰川泥石流诱发因素、区域发展演化规律及灾变指标的研究还较为初步,尚未构建完善的监测预警体系.借助多源长时序遥感影像、气象监测数据,结合野外实地验证和历史数据分析发现:川藏交通廊道周边区域冰川泥石流沟谷共99条,主要分布于恰青冰川-易贡乡、加拉贝垒-南迦巴瓦峰和古乡沟-嘎隆寺冰川一带;过去40年冰川经历了复杂的流动速度变化,表现为较小高海拔悬冰川活动性增强,大型沟谷冰川活动性减弱;自1973年以来,研究区冰川泥石流呈现频率增高、规模增大的特征.此外,从冰川泥石流发育沟道比降来看,发生高陡地形的滑坡、冰-岩崩诱发的泥石流频率增加.未来,冰川持续退缩,促使冰川源区冰瀑消失,发育更大规模的悬冰川,会增加这类冰川泥石流的风险;冰川泥石流形成及演化过程具有明显的灾变指标,如悬冰川裂隙密度增加、冰川速度增强、冰湖面积快速增加等.因此,基于以上认识,建议针对不同类型的冰川泥石流地建立完善的监测预警指标,并提出了融合卫星、航空遥感平台,气象、水文地面监测平台,地震动监测平台的冰川泥石流“空-天-地”立体监测框架,针对不同类型冰川泥石流进行灾变信息监测与预警判识,为川藏交通廊道安全施工运营提供技术参考.      

Genesis of the Woodstock drumlin field, southern Ontario, Canada

The Woodstock drumlin field was formed about 15,000 years ago during the Port Bruce Stadial of the Late Wisconsinan. It consists of three sections, each composed of texturally different till sheets (Tavistock A, B and C Tills) deposited during marginal oscillations of the Huron ice lobe advancing from the Lake Huron depression. A statistically significant relation between till texture and drumlin morphometry has been determined. Features composed of clayey-silt Tavistock A Till are smaller and more elongate than those built up of sandy-silt Tavistock C Till, which reflects a different susceptibility of the drumlin deposits to the moulding action of the glacier. Based on the field data it is suggested that the drumlinizing glacier was temperate all the way up to its margin and basal sliding occurred also at its outermost peripheries. In the drumlin region immediately behind end moraines the shear strength/shear stress ratio was around I and increased progressively in the upstream direction. In the proposed mechanism of drumlin formation the key factor is pore water dissipation (1) through the permeable substratum and (2) into dilatantly expanding granular deposits, both resulting in the necessary increase of the basal till strength.     

希夏邦马峰东南富曲河谷的冰川沉积和冰川构造

在希夏邦马峰（海拔８０１２ｍ）东南富曲河谷，中更新世以来有三次冰期；即聂拉木、富曲和普罗冰期。它们均可再分为两个亚阶段。聂拉木南的高冰碛平台长３.５ｍ，宽１.５ｋｍ，厚２００ｍ。属于中更新世聂拉木冰期（聂聂雄拉冰期）的巨大山谷冰川沉积，中尼公路从高冰碛平台尾端通过，形成数公里长的冰碛剖面，呈现出美丽多姿的冰川成因类型沉积和冰川构造现象，包括冰下，冰上融出碛，冰内.冰下河道沉积，冰湖沉积，坠碛，流磺等。冰川运动时造成的冰川构造，如断层、滑动面-…等也很清楚，代表了海洋型（暖冰川）冰川沉积和冰川构造特征，是中国目前研究冰川构造最理想的场所。     

河南东濮凹陷古近系沙三中亚段重力流沉积与伴生遗迹化石组合

基于对东濮凹陷97口钻井岩心的详细观察和分析,在古近系沙河街组沙三中亚段湖相沉积中识别出滑动、滑塌、碎屑流和浊流共4种类型的重力流沉积。各种类型沉积的主要判识特征如下: (1)滑动沉积以保留部分原始沉积构造、层内准同生小型断裂构造及较大角度的地层倾角(陡倾构造)发育、伴生Skolithos-Palaeophycus遗迹组合或Planolites-Taenidium遗迹组合为主要特征; (2)滑塌沉积以砂岩层顶、底面均与暗色泥岩呈突变接触以及岩层内部发育各种同生软沉积物变形构造(如包卷层理、火焰状构造、泄水构造、液化脉和各种撕裂屑等)为主要鉴别特征;(3)碎屑流沉积以砂岩呈块状构造、顶部发育漂浮砾石、底部泥岩撕裂屑发育并可见“泥包砾”现象、砂岩顶、底面均与暗色泥岩突变接触为特征;滑塌沉积和碎屑流沉积序列的上部常常伴生Mermoides-Parapaleodictyon遗迹组合; (4)浊流沉积以发育完整或不完整的鲍马序列为主要特征,浊积砂体下部见正粒序层理,底面见有冲刷痕、不规则槽模、重荷模等沉积构造,中上部发育深湖沉积中常见的Semirotundichnus-Puyangichnus遗迹组合。综合分析上述各种重力流沉积特征和伴生遗迹化石组合所体现的水深变化规律,认为遗迹化石组合随着湖水深度的增加呈分带性,与重力流沉积随水深增加而出现的滑动—滑塌—碎屑流—浊流沉积序列具有明显的一致性,且伴随重力流沉积而产生的生物扰动作用是增强的。因此,生物扰动构造(遗迹化石)的研究不仅对湖相沉积中储集层物性的分析具有重要意义,而且针对重力流沉积类型的判识还能提供重要的生物遗迹学信息。     

Gravity flow deposits associating with ichnoassemblages within the middle Member 3 of Paleogene Shahejie Formation in Dongpu sag,Henan Province

Based on the observation and analyses of 97 exploratory well cores in Dongpu sag,four types of gravity flow(including sliding,slumping,debris flow and turbidity current)deposits in lacustrine facies have been recognized within the middle Member 3 of the Paleogene Shahejie Formation. Their main identification marks are outlined as follows: (1)the sliding deposits are characterized by the partial preservation of primary sedimentary structures,the development of small penecontemporaneous fracture or fault in sandstone beds,and steep dip of strata,with Skolithos-Palaeophycus ichnoassemblage and/or Planolites-Taenidium ichnoassemblage,which commonly occurred in the shore and shallow lake environments. (2)General characteristics of slumping deposits mainly are the abrupt contact between sandstone beds(top and bottom)and dark mudstone beds,and development of all kinds of penecontemporaneous soft-sediment deformation structures such as convolution bedding,flame structure,water-escape structure,liquefied vein and tearing debris. (3)The sandy debris flow deposits are mainly marked by the massive sandstone,abrupt contact between sandstone beds(top and bottom)and dark mudstone beds,as well as developing floating gravels near the top of sandstone beds and tearing mudstone debris in the bottom of sandstone beds,sometimes with occurring the mud-coated intraclasts. Meanwhile,slumping and sandy debris flow deposits commonly associated with the Mermoides-Parapaleodictyon ichnoassemblage produced in semi-deep water lake environment. (4)The turbidity deposit is mainly indicated by the complete or incomplete Bouma sequences,normal-graded bedding,and all kinds of sole marks such as scour marks,irregular flute casts and load casts,and the Semirotundichnus-Puyangichnus ichnoassemblage frequently occurred in the middle to upper parts of the turbidite beds that formed in deep-water lake environment. After comprehensive analyses of above four types of gravity flow deposits and water-depth variation reflected by different ichnoassemblages,it can be considered that ichnoassemblage changes appear a zonation with the depth of the lake,which is consistent with variations in gravity flow deposits from sliding-slumping-debris flows to turbidity currents,and the bioturbation generated with gravity flow deposits is enhanced. Therefore,the research of bioturbation structures(ichnofossils)is not only of great significance to study the physical property of sandstone reservoir in lacustrine deposits,but also to provide important ichnological information for discerning various types of gravity flow deposits.