云南千湖山第四纪冰川发育特点与环境变化

千湖山(4249 m) 是横断山脉中段保存确切第四纪冰川遗迹的山地,受西南季风影响强烈。对于研究青藏高原边缘山地冰川发育与气候和构造之间的耦合关系具有十分重要的科学意义。在千湖山海拔3500 m以上保存着古冰川侵蚀与堆积地貌,冰川发育依托海拔4000~4200 m的夷平面及其支谷地形。冰川形态类型为小型的冰帽以及由冰帽边缘溢流进入山谷的山谷冰川。应用相对地貌法,光释光(OSL) 年代测试,本文确定千湖山地区的冰进系列:末次冰盛期(LGM,22.2±1.9 ka BP)、末次冰期中期(MIS3b,37.3±3.7 ka BP、45.6±4.3 ka BP45.6±4.3 ka BP)、末次冰期早期(MIS4)。千湖山冰川前进规模是MIS3b 阶段大于末次冰盛期,主要原因是末次冰期中期(MIS3b) 时本区气候相对湿润,而在末次冰盛期(MIS2) 时气候条件比较干燥。在总体相似的气候背景下,与横断山其它存在多期次冰川作用的山地相比,千湖山只发育末次冰期的冰川作用,其差异性说明该地区冰川发育主要受山体构造抬升控制。     

东亚沿海山地末次冰期冰川与环境

对东亚沿海山地末次冰期冰川发育的气候条件、构造背景、冰进时序、发育规模等研究表明,台湾山地保存着3期冰川作用遗迹,冰川的最大前进规模发生在MIS3b阶段,其规模大于MIS2阶段;日本山地冰期系列齐全,包含了末次冰期的早(MIS4)、中(MIS3)、晚(MIS2)3个阶段的冰进,其规模是MIS4/3阶段大于MIS2阶段;而长白山存在2期冰川作用的遗迹,即末次冰盛期(MIS2)和晚冰期.在相似的冬雨(雪)型季风影响区,冰川发育的时序与规模也有一定不同,反映出在大气候背景下的区域性差异,在东亚季风影响范围内,末次冰期的环流变化在各地也很不一致.最新推算的现代理论雪线自北(日本)向南(台湾)依次递增,范围是2750～4245 m,除日本北部的高纬地区雪线降低值400 m之外,末次冰盛期(LGM)的雪线降低值在800～1300 m之间,平均值1000 m左右.东亚沿海山地冰川发育与新构造运动密切相关,更新世山体的快速抬升为冰川发育的内因,如台湾山地在末次冰期的MIS3b阶段,山体的抬升量约为250 m,对山体的高度和雪线变化有很大影响.     

他念他翁山中段第四纪冰川沉积物时空分布特征与环境

他念他翁山中段位于横断山脉西部,保留着良好的第四纪冰川遗迹,论文以该地区第四纪冰川沉积物为主要研究对象,通过光释光(Object-source lighting, OSL)测年、粒度、磁化率、矿物及化学元素分析等方法,探讨研究区第四纪冰川沉积物在不同时期的沉积学、矿物学、环境磁学以及元素地球化学特征,结合相关环境指标分析该区的环境特点。研究表明：① 冰川沉积物总体沉积特征是大小混杂、无层理、无分选、风化程度由倒数第二次冰期到新冰期依次减弱。② 研究区冰川沉积物细粒部分在粒度频率曲线上主要呈现双峰或多峰,反映出沉积物的物质来源复杂、形成动力多样。冰碛物的平均粒径在空间上表现出距冰川作用源头越远粒径越小的规律,主要是受冰川作用强度和风化时间长短的影响。③ 冰川沉积物的磁化率值为8.72×10^-8~298.00×10^-8 m³·kg^-1,其中冰水沉积物磁化率的平均值(178.51×10^-8 m³·kg^-1)和波动幅度(17.43×10^-8~298.00×10^-8 m³·kg^-1)要大于冰碛物(平均值19.82×10^-8 m³·kg^-1,波动幅度8.72×10^-8~42.95×10^-8 m³·kg^-1),反映出磁铁矿集中分布的粒级与冰水沉积物组成的粒级相似。④ 地球化学和矿物学指标反映青古隆地区古气候的总体特征为寒冷干燥,其中在末次冰盛期时气候最为干旱,末次冰期中冰阶时气候较为干旱、降水量相对于末次冰盛期有所增加,倒数第二次冰期降水量相对于末次冰盛期和末次冰期中冰阶较多,但气温较低。     

四川螺髻山清水沟冰川槽谷演化及其影响因素

螺髻山地处青藏高原东南缘,是确切存在第四纪古冰川遗迹的典型山地之一,该区冰川地貌演化对于研究环境变化具有重要的科学意义。螺髻山东坡清水沟保存两套古冰川槽谷,分别为上槽谷和下槽谷,其中下槽谷保存完整,而上槽谷在3450~3600 m的阴坡部分出现缺失。采用野外地貌调查与模型分析相结合的方法,对冰川槽谷地貌进行分析,结果表明:清水沟槽谷的抛物线模型中,|A|值在1.3101~15.2064 之间变动,B 值变化于0.9695~3.2965 之间,且随着海拔由高到低,都存在着先变小后变大的规律,A、B值同时反映出在海拔3450~3600 m处冰川槽谷的演化不符合常态。分析认为岩性差异和河流溯源侵蚀是影响上槽谷形态的主要原因。对保存在清水沟上下槽谷内的高、低侧碛进行ESR年代测定,结果显示:高侧碛形成于58-84 ka BP左右的末次冰期早期,对应深海氧同位素4 阶段(MIS4);低侧碛形成于13-17 ka BP,属于于全球末次冰盛期晚期的产物。两次冰川作用分别塑造出两套冰川槽谷,即在末次冰期早期冰川作用形成上槽谷,末次冰期晚期形成下槽谷。     

青海湖东岸末次冰期冰盛期和早全新世沙漠范围重建

基于野外沉积物调查、已报道的风成沉积物年代和重建的湖泊水位波动曲线,初步绘制了末次冰期冰盛期和全新世早期青海湖东岸的沙漠范围。初步认为,末次冰期冰盛期时青海湖大幅度萎缩,湖底沉积物暴露并遭受风蚀,在偏西风的搬运下,近岸粗颗粒砂堆积在日月山西侧和倒淌河河谷,形成流动沙丘,细颗粒沉积物被向东搬运沉积至河湟谷地和黄土高原。倒淌河源头的沙丘最晚是在末次冰期盛冰期(23~16ka BP)沙漠扩张时形成并残留至今的;青海湖东部日月山西侧山麓地带和倒淌河河谷中、晚全新世黄土、古土壤下部普遍沉积的风成砂是末次冰期冰盛期和全新世早期(11~9 ka BP)青海湖东岸地区大范围沙化的证据。     

中国第四纪冰川作用与深海氧同位素阶段的对比和厘定

随着冰期(阶)与间冰期(阶)旋回的不断细化,第四纪冰期系列与深海氧同位素阶段(MIS)对比之间所反映的问题开始逐步显现。通过中国第四纪冰期与MIS阶段对比,结合分析气候旋回与构造运动对地貌演化的控制作用,研究表明:①冰期(阶)或者间冰期(阶)发生的时段应尽可能对应于MIS的偶数或奇数阶段,有助于MIS框架下新的冰期(阶)的发现;②中更新世以来,中国第四纪冰期-间冰期旋回可能受控于100 ka轨道偏心率变化的气候大背景,昆仑冰期-倒数第二次冰期的冰川规模总体上与全球冰量变化一致。然而,末次冰期早、中期的冰川规模却与MIS所记录的全球冰量变化不尽一致,强烈显示气候与构造环境对冰川作用的影响;③目前在中国第四纪冰期划分方案中,存在着冰期系列由时间和地点双重命名的现象,建议用大理冰期、古乡冰期分别代替末次冰期和倒数第二次冰期。     

云南点苍山-罗坪山地区地貌发育与第四纪冰川作用

通过野外考察及地质地貌剖面解析,对云南点苍山的地貌发育作了分析研究,并对罗坪山丽江期古冰川作用作了初步探讨.结果认为:点苍山的地貌是一种多元化、多层次、聚变式的多层地貌组合.其地貌发育系统自山顶到坡脚分为古夷平面解体过程,古冰川与冰缘作用,流水作用,古冰川漂砾、洪积、冲积、泥石流、水石流等混杂堆积,山麓阶地与滨湖平原发育过程;点苍山发育了二次冰期,即未次冰期(大理冰期)和倒数第二次冰期(丽江冰期),是中国大陆发育古冰川的最南界;比苍山主峰海拔低800m的罗坪山发育了倒数第二次冰期,出现了复合型山岳冰川.     

点苍山大理冰期研究回顾、讨论与展望

大理冰期作为第四纪末次冰盛期,在了解历史环境变化方面具有很高的研究价值,多年来中国学者用各种传统研究方法对大理冰期的起源地——点苍山的末次冰期进行了研究,并获取了大量科学成果。回顾这一历史进程,重点对航空遥感、地质地貌结构、冰川地貌特征、区域尺度等方面的研究方法及结果进行了总结。并在此基础上讨论了一些存疑,分析了运用3S技术进行冰川研究和古冰川模型重建的基础问题及可行性。     

亚洲中纬度地区第四纪冰川作用差异性探讨

近年来,随着绝对年代的不断增加,第四纪冰川作用的启动时间以及演化特点日益明确,为探讨中纬度地区的冰川的形成机制提供了重要依据,同时也为研究中国第四纪冰川发育的构造与气候耦合关系奠定了重要基础。亚洲中纬度地区山地第四纪冰川的冰进时序、冰期历史和冰川规模显示出不同特点。总体来说,西部山地的冰川规模随时间逐渐缩小,冰川历史较为完整,冰川规模大于亚洲东部,东部山地的冰期历史较短,冰川作用的阶段性明显;不同地区的最大冰川扩展规模在时间上不一致,尤其是在末次冰期旋回中,MIS3/4阶段的冰川规模大于传统意义上的末次冰盛期(LGM),冰进时序和规模演化指示了不同的大气环流尤其是西风环流和季风环流对冰川发育的重要影响。此外,构造因素深刻影响着不同地区的冰期系列。     

阿尔泰山喀纳斯河谷晚第四纪冰川地貌演化过程

阿尔泰山喀纳斯河流域在第四纪期间发生过多次冰川进退,丰富的侵蚀与堆积地貌为区域地貌演化过程分析提供了重要依据,同时,该区的第四纪冰川作用对全球环境变化研究具有重要的科学意义。通过对喀纳斯湖口以下主谷内古冰川地貌的实地考察,测定不同地段多级U型谷底(台地)的海拔高度以及冰川漂砾的上限与分布位置,并对主谷内不同地段不同期次的冰碛物进行电子自旋共振(ESR)测年,研究发生在主谷内的古冰川作用系列、规模及演化过程。结果表明:喀纳斯湖到驼颈湾地区的谷地中主要发生过4次冰川作用,时代分别对应中梁贛冰期(MIS12)、MIS8/10、倒数第二次冰期(MIS6)以及末次冰期。末次冰期冰川作用又可细分为3个阶段,分别对应MIS4、MIS3中期与MIS2;根据三级U型谷的分布特征推断,古冰川作用规模呈现渐次变小的规律,自冰川站至下游接近冰川末端,中梁贛冰期时冰川厚度达50~395 m,覆盖范围包括主谷及两侧的山梁和支谷,延伸的长度和宽度都最大,MIS8/10以及倒二冰期时的厚度分别在102~199 m和88~269 m之间,冰川末端到达驼颈湾附近;鸭泽湖附近坡地上保存完好的多级台地,说明发生在河谷内的古冰川活性大,流动性和连续性较强,具有温冰川的性质;喀纳斯主谷有明显的不对称性,与局部小气候和地形对冰川的发育影响有关。     

云南东北部拱王山末次冰期

1 Introduction The Gongwang mountains constitute one of the few high m ountains of irrefutable late Pleistocene glaciation in eastern China. This area is one of the m ost extensively studied Quaternary geologicallocationsin eastern China and the interpret…     

Late Pleistocene glaciation of the Hulifang Massif of Gongwang mountains in Yunnan Province

Late Pleistocene glaciation was restricted to only a few high mountains in eastern China. The Gongwang mountains constitute one of the typical places once glaciated. Geomorphic mapping of the area and the TL dating provides evidence for at least four distinct glaciations. YJT-I glacial advance occurred about 100 ka BP and two TL absolute ages (101,100 ±7780 a BP; 104,000±8300 a BP) indicate this advance happened during the Penultimale Glaciation. The early stage glacial advance (YJT-II advance) during the last glaciation occurred about 40,920±3400 a BP. The last glacial maximum advance (YJT-III advance) about 18-25 ka BP, which sustained by two TL ages (18,230 ±1420 a BP; 25,420 ±2110 a BP). The Penultimale and the early stage glaciations were more extensive and the last glacial maximum (LGM) and the late-glacial period (YJT-IV advance, 10 ka BP) were progressively less extensive. Correlated with the other mountains in eastern China, these glacial advances in the Gongwang mountains just like the advances in the western part such as Diancang mountains, Yulong mountains of Yunnan Province and the glacier series are more complete than the adjacent mid-latitude regions such as Taibai mountain and Taiwan mountains and are roughly representative of climate changes during the last glacial cycle in Yunnan Province.     

Mountain-derived versus shelf-based glaciations on the western Taymyr Peninsula, Siberia

The early Russian researchers working in central Siberia seem to have preferred scenarios in which glaciations, in accordance with the classical glaciological concept, originated in the mountains. However, during the last 30 years or so the interest in the glacial history of the region has concentrated on ice sheets spreading from the Kara Sea shelf. There, they could have originated from ice caps formed on areas that, for eustatic reasons, became dry land during global glacial maximum periods, or from grounded ice shelves. Such ice sheets have been shown to repeatedly inundate much of the Taymyr Peninsula from the north-west. However, work on westernmost Taymyr has now also documented glaciations coming from inland. On at least two occasions, with the latest one dated to the Saale glaciation (marine isotope stage 6 [MIS 6]), warm-based, bedrock-sculpturing glaciers originating in the Byrranga Mountains, and in the hills west of the range, expanded westwards, and at least once did such glaciers, after moving 50–60 km or more over the present land areas, cross today's Kara Sea coastline. The last major glaciation affecting south-western Taymyr did, however, come from the Kara Sea shelf. According to optically stimulated luminescence dates, this was during the Early or Middle Weichselian (MIS 5 or 4), and was most probably not later than 70 Kya. South-western Taymyr was not extensively glaciated during the last global glacial maximum ca. 20 Kya, although local cold-based ice caps may have existed.     

山东中低山丘陵古冰川遗迹质疑

近年来,有关山东中低山丘陵“古冰川遗迹”时有报道,使中国东部第四纪冰川问题在某种意义上再起纷争。为作澄清,通过实地考察对业已报道的“古冰川遗迹”进行质疑,指出其列举的“冰碛垄”“古冰斗”“擦痕”“颤痕”等不符合冰川地貌证据的专有属性和判别标准,冰期划分和雪线重建不符合科学发现与科学事实确证所需的充分条件,即不满足“将古论今”、地貌组合三要素系统配套、成因-环境一致性的判别原则和方法。因此认为,山东中低山丘陵不存在第四纪冰川遗迹。部分学者提出“低海拔型古冰川”的论断,是基于例外主义的泛冰川论,必然会引致“雪球地球”事件进而颠覆第四纪为灵生纪的科学基础。     

长白山现代理论雪线和古雪线高度

According to the glacial landforms and deposits with the optically stimulated luminescence (OSL) dating results, two glacial stages of the last glacial cycle (LGC) and Late Glacial were identified. The Late Glacial stage (Meteorological Station glacier advance) took place about 11 ka (11.3±1.2 ka), and the last glacial maximum (LGM), named Black Wind Mouth glacier advance, occurred at 20 ka (20.0±2.1 ka). Based on the Ohmura’s formula in which there is a relationship between summer (JJA) atmospheric temperature (T) and the annual precipitation (P) at ELA, the present theoretical equilibrium line altitude (ELA_t) in Changbai Mountains was 3380±100 m. Six methods of accumulation-area ratio (AAR), maximum elevation of lateral moraines (MELM), toe-to headwall altitude ratios (THAR), the terminal to summit altitudinal (TSAM), the altitude of cirque floor (CF), and the terminal to average elevation of the catchment area (Hofer) were used for calculation of the former ELAs in different stages. These methods provided the ELA for a range of 2250–2383 m with an average value of 2320±20 m during the LGM, which is 200 m higher than the value of previous investigation. The snowlines during the Late Glacial are 2490 m on northern slope, and 2440 m on western slope. The results show that the snowline on northern slope is 50 m higher than that on western slope during the Late Glacial, and the average snowline is 2465m. The ΔELA values were more than 1000 m during the LGM, and about 920 m lower than now during the Late Glacial stage respectively. Compared with Taiwanese and Japanese mountains in East Asia during the LGM, the effect of the uplift on ELA in Changbai Mountains during the glaciations (i.e. 20 m uplift in the LGM and 11 m in the Late Glacial) is not obvious. Foundation: National Natural Science Foundation of China, No.40571016 Author: Zhang Wei (1969–), Ph.D and Professor, specialized in Quaternary environment and climate geomorphology.