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冰川冻土, 2021, 43(3): 735-746 doi: 10.7522/j.issn.1000-0240.2021.0015

西藏东南部末次冰期早阶段冰川作用及其古气候意义

谢金明,1, 周尚哲,2, 许刘兵2, 杨太保,1

1.兰州大学 资源环境学院,甘肃 兰州 730000

2.华南师范大学 地理科学学院,广东 广州 510631

Glacial activity during early stage of Last Glaciation in southeastern Tibet and its paleoclimate implication

XIE Jinming,1, ZHOU Shangzhe,2, XU Liubing2, YANG Taibao,1

1.College of Earth and Environmental Sciences,Lanzhou University,Lanzhou 730000,China

2.School of Geography,South China Normal University,Guangzhou 510631,China

通讯作者: 周尚哲,教授,主要从事地貌与第四纪环境变化研究. E-mail: szzhou@scnu.edu.cn杨太保,教授,主要从事冰冻圈及全球变化研究. E-mail: yangtb@lzu.edu.cn

编委: 武俊杰

收稿日期: 2021-05-22   修回日期: 2021-06-07   网络出版日期: 2021-07-29

基金资助: 国家自然科学基金项目.  41771065.  41271024

Received: 2021-05-22   Revised: 2021-06-07   Online: 2021-07-29

作者简介 About authors

谢金明,博士研究生,主要从事第四纪冰川研究.E-mail:xiejinming666@163.com , E-mail:xiejinming666@163.com

摘要

西藏东南部的“古乡冰期”和“白玉冰期”是划分中国第四纪冰期的蓝本。其中,白玉冰期即末次冰期,分为早阶段和晚阶段,相对应的冰川沉积广泛分布于本区的波堆藏布谷地。已有的冰川数值年代结果显示,末次冰期晚阶段的冰川作用发生于海洋氧同位素阶段(MIS)2。然而,关于早阶段的冰进记录,目前却未有确切的年代学证据,此次冰川作用究竟发生于MIS 4还是MIS 3,是一个悬而未决的问题。在前人研究及野外地貌调查的基础上,运用光释光测年手段对波堆藏布谷地疑似形成于末次冰期早阶段的冰碛垄进行测年,年代结果介于(56.4±4.2)~(65.9±3.9) ka之间,相当于MIS 4。藏东南地区MIS 4冰期冰川作用年代与青藏高原及其周边山地具有可比性,表明该阶段冰川作用发生的普遍性。通过对比北半球低纬度地区夏季太阳辐射及亚洲季风区古气温与古降水指标记录,认为藏东南地区MIS 4冰期冰川作用可能是对北半球低纬度地区夏季太阳辐射减弱及气温下降的响应,与季风降水无关。

关键词: 西藏东南部 ; 末次冰期早阶段 ; 光释光测年 ; MIS 4冰期

Abstract

The “Guxiang Glaciation” and “Baiyu Glaciation”, originated from Bodui Zangbo Valley, southern slope of eastern Nyainqêntanglha Range in southeastern Tibet, are the representative periods of Quaternary glaciations in Tibetan Plateau. Among them, Baiyu Glaciation (Last Glaciation) can be divided into early and late stages, and their corresponding glacial sediments are widely distributed in Bodui Zangbo Valley. Numerical dating of glacial deposits has suggested that the glacier advance during the late stage occurred in marine oxygen isotope stage 2 (MIS 2). However, the earlier glacial event has been lacking of effective chronology. Furthermore, whether this glaciation happened during MIS 4 or MIS 3 remains an open question. Based on previous researches and detailed field investigation, this study used optically stimulated luminescence (OSL) technique to date the moraines which have been suspected to construct during the early stage of Last Glaciation. The OSL ages range from (56.4±4.2) to (65.9±3.9) ka, corresponding to MIS 4. The ages could compare to other dated glacial advances in Tibetan Plateau and its surrounding mountains, suggesting this glacial event ever commonly occurred. Compared with summer insolation at 30° N and paleo-temperature and precipitation proxy records from regions dominated by India summer monsoon, it is likely that the reduced summer insolation at 30° N and decreased temperature caused the glacier expansion during MIS 4 in southeastern Tibet, not related to the summer monsoon and moisture.

Keywords: southeastern Tibet ; early stage of Last Glaciation ; OSL dating ; MIS 4 glaciation

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本文引用格式

谢金明, 周尚哲, 许刘兵, 杨太保. 西藏东南部末次冰期早阶段冰川作用及其古气候意义[J]. 冰川冻土, 2021, 43(3): 735-746 doi:10.7522/j.issn.1000-0240.2021.0015

XIE Jinming, ZHOU Shangzhe, XU Liubing, YANG Taibao. Glacial activity during early stage of Last Glaciation in southeastern Tibet and its paleoclimate implication[J]. Journal of Glaciology and Geocryology, 2021, 43(3): 735-746 doi:10.7522/j.issn.1000-0240.2021.0015

0 引言

西藏东南部念青唐古拉山东段,地貌特征主要表现为海拔6 000 m以上的夷平面以及深切的河谷。本区由于临近雅鲁藏布江大拐弯,南亚季风带来的暖湿气流可以伸入河谷,使之成为青藏高原上降水量最多的地区之一。丰沛的降水加之高大的地形,也使本区成为高原上现代海洋性冰川及第四纪冰川规模最大的地区之一。早在20世纪70年代,李吉均等1考察本区波堆藏布谷地古冰川遗迹,提出了“古乡冰期”和“白玉冰期”两次冰川作用。其中,白玉冰期(即末次冰期)分为早期和晚期两个阶段,相应的冰川沉积在波堆藏布主要支沟沟口(白玉沟、珠西沟等)保存最为完整,地貌上可划分为外冰碛垄和内冰碛垄,推测其形成年代分别对应于海洋氧同位素阶段(marine oxygen isotope stage, MIS)4和2。周尚哲等2应用宇宙成因核素(terrestrial in situ cosmogenic nuclide, TCN)10Be暴露测年手段,证实白玉冰期晚阶段冰碛垄的年代对应于MIS 2。目前,随着测年技术手段的发展及冰川数值年代的增加,波堆藏布流域的冰川演化序列日益完善,发生于MIS 12(甚至更早)3、末次冰消期4-5、新冰期以及小冰期6等时期的冰川作用也相继得到年代学的证实。然而,末次冰期早期的冰川作用年代还处于推测阶段,此次冰川作用究竟发生于MIS 4还是MIS 3,这一问题尚存在争议。因此,本文在野外地貌考察的基础上,运用光释光(optically stimulated luminescence, OSL)测年技术,对波堆藏布流域疑似形成于末次冰期早阶段的典型冰川/冰水沉积物进行定年,以期探讨末次冰期早阶段冰川作用时间及其古气候意义。

1 研究区概况

波堆藏布江发源于念青唐古拉山东段南坡,自西北向东南流100 km后汇入帕隆藏布江,流域面积约1.46×105 km2图1)。帕隆藏布江自东向西,至通麦汇合易贡藏布江,南流注入雅鲁藏布江。来自孟加拉湾的强大水汽,沿着雅鲁藏布江谷地深入帕隆藏布流域,带来丰沛的降水。根据波密气象站(29.87° N、95.77° E,海拔2 736 m)的观测数据,研究区年降水量约890 mm,其中6—9月的降水量占比超过了80%(1981—2011年,http://data.cma.cn),而平衡线附近的降水量可达1 000~3 000 mm7。充沛降水加之高大地形的抬升作用为本区海洋性冰川发育提供了优越的条件。波堆藏布流域共有现代冰川482条,总面积974 km2[8图2)。流域内最高峰则普峰,海拔为6 364 m,其上发育了规模最大的现代冰川则普冰川,长达19.2 km,面积76.2 km2[9。则普冰川同其他支沟冰川在第四纪期间多次进退于波堆藏布谷地,留下了丰富的古冰川作用遗迹。

图1

图1   研究区地理位置及其DEM

Fig.1   Location of the study area and its DEM


图2

图2   波堆藏布江流域现代冰川与古乡冰期和末次冰期冰碛垄分布

Fig.2   Modern glaciers and moraines constructed during Guxiang Glaciation and Last Glaciation in the Bodui Zangbo River catchment


测年研究表明,流域内最早的冰川作用为尼通冰期,相当于MIS 12甚至更早,典型冰碛物主要遗存于波堆藏布主谷3处已相当残破的高谷肩上3。古乡冰期冰碛垄在主谷中表现得蔚为壮观,从上游育仁乡至白玉村沿着谷坡断续分布,另在波堆藏布汇流处卡达桥附近也保存了一处相对完好的高大侧碛垄(图2)。根据冰碛垄的保存位置,当时支谷冰川都汇入了主谷,形成长约100 km、规模为现代冰川6~8倍的复合型山谷冰川1。末次冰期最盛期时,波堆藏布主谷和亚龙藏布谷地均被古冰川所占据,冰川末端分别到达白玉村和达龙村附近,冰川规模为现代的4~7倍1。末次冰期时,白玉冰川和珠西冰川均前进至沟口,在沟口处留下了规模宏大的终碛垄(图2)。形成于末次冰期晚阶段的内终碛垄,可分为2~3道,冰碛垄形态相对完好,拔河高度介于200~350 m之间。周尚哲等2、Ou等5对白玉沟内冰碛垄进行了测年,其中漂砾的TCN 10Be暴露年代介于(11.1±1.9)~(18.5±2.2) ka之间,冰碛物及冰水沉积物的石英单颗粒OSL年代则处于(8.0±2.5)~(14.4±4.2) ka之间,认为内冰碛垄为MIS 2期间冰川作用的产物。推测形成于末次冰期早阶段的外终碛垄,其形态大多残破,垄脊相对平缓,高度也大为降低,拔河约100~200 m(图2)。

除主要支沟外,疑似形成于末次冰期早阶段的冰碛垄在亚龙藏布谷地中也有保存(图2~3),李吉均等1推测冰期最盛时的古冰川长达75 km直到沟口附近。野外考察发现,亚龙藏布谷口南岸和北岸均保存有高低两套侧碛垄,其中,北岸高侧碛垄的规模最大。波堆藏布江于谷口处将冰碛垄切割成一个高达150 m的典型三角面,突起的垄脊从谷口往上游延伸约4.5 km,与松龙沟高大终碛垄相接,最后消失于谷坡上。相应地,冰碛垄的拔河高度则由200 m递增至320 m。南岸高侧碛垄因受冲沟的侵蚀作用,断续分布于谷坡上,垄脊的形态不明显。与高侧碛垄一样,低侧碛垄在北岸连续分布,而在南岸间断保存。北岸低侧碛垄垄脊形态明显,上游与松龙沟终碛垄相接,向下游延伸约4 km,末端高出地面不到2 m,最后尖灭于河流阶地沉积物中。保存于南岸的低侧碛垄,受河流改造作用明显,垄脊相对平坦,顶部最宽处可达70 m。野外调查发现,高低侧碛垄在上游也有相当程度的保存。高侧碛垄向上游一直断续分布,直到海拔约3 700 m处,此处拔河高度约500 m,而低侧碛垄仅在松龙沟上游附近有所保存(图2)。

图3

图3   亚龙藏布江与波堆藏布江汇流处附近的冰川地貌、河流阶地及采样点位置(a)和野外照片(b,c,d)

Fig.3   Glacial landforms, river terraces, sampling sites (a) and field photos of moraines (b,c) and terrace T2 (d) near the confluence of the Yalong Zangbo and Bodui Zangbo Rivers


亚龙藏布谷口附近广泛发育了两级冰水阶地(图3)。这两级阶地的阶地面均相对平坦,T2阶地主要分布于波堆藏布东岸和亚龙藏布北岸,面积达4 km2,拔河高度20~50 m。T2阶地在亚龙藏布南岸的分布面积较小,为0.8 km2,拔河高度30~80 m。T1阶地在亚龙藏布南岸和北岸均有分布,两处的分布面积均约为1 km2,拔河高度3~10 m。从地貌上看,阶地发育时间要晚于冰碛垄,低侧碛垄末端部分被T2阶地沉积物所覆盖。

2 研究方法

2.1 样品采集

在亚龙藏布谷地低侧碛垄采集了4个(YL01-04)光释光测年样品(图3~4)。YL01的采样剖面,砾石大小混杂,无分选,但磨圆度较好,胶结程度高。样品采自一处长约2 m,宽20~30 cm的冰水透镜体中,冰水夹层为粉砂与细砾互层,以粉砂为主。YL02的采样冰碛层,砾石无分选,但有一定磨圆度,胶结程度高。样品采自砾石和粉砂互层的粉砂层中,透镜体周边出露有直径1 m的棱角状砾石。YL03的采样剖面以直径10 cm以内次棱角和次圆状的砾石及粉砂为主,胶结较好。新鲜剖面可见粉砂和细砾互层,采样物质为粉砂。YL04也采自附近粉砂与细砾互层处的粉砂层中。以上4个样品物质均为冰水夹层中的粉砂,来源于冰面湖或冰下河道沉积。

图4

图4   采样点剖面图

Fig.4   Photos showing the sampling sections


冰川作用时代可与相应的冰水阶地的发育年代相对应,因此在T2阶地剖面采了一个光释光年代样品(YLT18),用以验证冰碛垄的形成年代。YLT18的采样剖面出露高度约4 m,砾石直径大多介于5~30 cm之间,磨圆程度高,砾石之间充填砂及细砾,有分选。出露剖面的下部夹有一处长约2 m、宽约20 cm的粗砂层,样品采自这一粗砂层中。

采样时先挖开新鲜剖面,将一端塞了黑色塑料袋和棉花的不锈钢钢管(长20 cm,直径5 cm)砸入剖面中。取出钢管,用棉花和黑色塑料袋先后套住钢管的另一端,通过遮光的管道胶带将钢管的两端密封。

2.2 前处理

在红光实验室取出钢管两端少部分可能已经曝光的样品,用于含水量和年剂量的测定。

样品前处理之前先用300 μm干筛将粗颗粒的砾石去除。将样品用10%稀盐酸和30%双氧水依次浸泡,去除样品中的碳酸盐和有机质。对于冰碛物样品,干筛提取38~63 μm组分(中颗粒组分),用氟硅酸浸泡样品2周之后,通过10%稀盐酸去除样品与氢氟酸反应过程中产生的氟化物沉淀。对于冰水阶地样品,干筛提取90~125 μm组分(粗颗粒组分),通过多钨酸钠重液分离出石英颗粒。用40%氢氟酸浸泡40 min,去除长石,随后用10%稀盐酸浸泡样品30 min,以去除氟化物。通过红外检测方法检测石英颗粒的纯度。若长石信号较高,则需再用氟硅酸或氢氟酸刻蚀样品,直到红外信号达到较低的水平(IRSL/OSL<10%)为止。将纯石英样品用硅油均匀粘贴在直径0.97 cm的不锈钢测片中,样品的粘贴直径平均约为0.6 cm。

2.3 等效剂量与年剂量测试

等效剂量(equivalent dose,De)采用单片再生剂量法(single aliquot regeneration-dose,SAR)测试10。实验在华南师范大学地质年代学实验室完成,测试仪器为丹麦Risø TL/OSL DA-20全自动释光仪,内置90 Sr/90 Y人工β辐射源用于辐照。预热温度选定为260 ℃(10 s),试验剂量的预热温度为220 ℃(10 s)。测试石英释光信号的激发光源为波长(470±30) nm的蓝光二极管(强度90%),激发温度为120 ℃(40 s)。OSL信号通过7.5 mm的HoyaU-340滤光片进入9235QA光电倍增管内被接收并记录。

年剂量率计算中的U、Th和K的含量在北京第二核工业研究所测定。样品的实测含水量均在3%以内,考虑到样品运输及储存过程中的水分损失,结合当地降水量,石英中颗粒年代样品采用(10±5)%的估计值,粗颗粒采用(5±4)%的估计值11-13。宇宙射线的年剂量贡献根据样品的地理位置、海拔高度和采样深度计算14。剂量率根据Aitken的公式和参数进行计算15

3 实验结果

3.1 释光特征

图5展示了样品YL02的光释光衰减曲线和生长曲线。从衰退曲线可以看出,OSL信号在蓝光激发下的最初几秒衰减很快,表明OSL信号以快速组分为主。该样品的循环比在0.95~1.05之间,说明试验剂量对感量变化的校正较为理想。样品的热转移值介于0.15%~0.76%之间,表明测试过程中热转移效应对等效剂量的贡献较低,对年代结果产生的影响很小。图6为所有样品的De散点图。

图5

图5   样品YL02(虚线)和标样(实线)天然剂量的衰减曲线(小图为样品YL02的生长曲线)

Fig.5   OSL decay curves of natural dose of Sample YL02 (dashed line) and standard sample (solid line) (The inserted figure shows the growth curve of Sample YL02)


图6

图6   样品De散点图

Fig.6   De scatter plots for the samples


3.2 预热坪与剂量恢复实验

为选择合适的SAR程序的预热温度,本文选择样品YL02进行预热坪和剂量恢复实验。对样品制备20个样品测片用于预热坪实验,测片分为5组,分别在220 ℃、240 ℃、260 ℃、280 ℃、300 ℃的条件下预热10 s,试验剂量的预热温度则为220 ℃,预热时间为10 s。每组预热温度的De平均值如图7(a)所示,结果相差不大,且各个温度条件下的循环比和热转移值都在合理范围内[图7(c)]。参考前人相关研究16-17,本文选择260 ℃作为预热温度,实验剂量的预热温度为220 ℃,预热时间均为10 s。

图7

图7   样品YL02预热坪和剂量恢复实验结果及其循环比和热转移

Fig.7   Results of preheat plateau test (a), recycling ratio, and recuperation (c) of Sample YL02, and results of dose recovery test (b), recycling ratio, and recuperation (d) of Sample YL02


对于剂量恢复实验,先准备10个样品测片,将其释光信号清除后,对每个测片给定200 Gy的辐照剂量。将测片分为5组,每组分别在220 ℃、240 ℃、260 ℃、280 ℃、300 ℃的条件下预热,测试程序如上。每组测片的De平均值介于198.78~203.59 Gy之间,与给定剂量的比值均在0.9~1.1之间[图7(b)],且各个温度条件下的样品循环比和热转移值均介于合理阈值范围内[图7(d)],说明以上测试程序可以恢复已知的剂量。

4 年代结果

OSL年代结果见表1De值采用中值年代模型(central age model,CAM)计算得出。

表1   光释光测年结果

Table 1  OSL dating results

样品编号深度/mU/10-6Th/10-6K/%含水量/%a剂量率/(Gy·ka-1测片数bOD/%古剂量/Gy年代/ka
YL016.23.64±0.4023.4±2.31.46±0.2010±5(2.3)3.77±0.2248(0)31±3212.5±9.856.4±4.2
YL025.03.32±0.3019.7±2.01.31±0.1010±5(3.0)3.33±0.1948(1)11±1200.6±3.260.3±3.5
YL035.23.74±0.4020.6±2.11.73±0.2010±5(2.5)3.88±0.2248(1)6±1255.5±2.565.9±3.9
YL045.23.22±0.3022.4±2.21.56±0.2010±5(1.9)3.72±0.2148(13)9±3116.0±3.931.2±2.1
YLT183.23.80±0.3825.3±2.52.70±0.305±4(2.9)5.30±0.3012(0)25±5346.0±25.165.2±6.0

注:a.含水量采用(10±5)%的估算值,括号内为实测样品的含水量;b.括号内的数字为年代计算过程中被剔除的测片数。

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5 讨论

5.1 测年结果分析

表1所示,冰碛物YL01-04这4个样品的CAM年代分别为(56.4±4.2) ka、(60.3±3.5) ka、(65.9±3.9) ka和(31.2±2.1) ka,河流阶地沉积物样品YLT18的CAM年代为(65.2±6.0) ka。根据野外调查及地貌地层关系,T2阶地的形成时代应该接近或稍晚于冰碛垄的建造时代,基于此,YL04的年代应当剔除。YL04年代结果偏年轻可能是由于后期曝光所致。其余3个冰碛物样品(YL01、YL02和YL03)的年代介于(56.4±4.2)~(65.9±3.9) ka之间,这一年代结果可与保存于白玉村南侧谷坡附近的侧碛垄上的8个漂砾TCN 10Be暴露年代结果相对应[(57.7±5.7)~(72.0±7.4) ka(未发表)]。这两处冰川沉积物的年代均对应于MIS 4,表明冰碛垄为MIS 4冰期冰川作用的产物。松龙沟高大冰碛垄上的漂砾TCN 10Be暴露年代位于(14.8±0.9)~(19.5±1.2) ka之间(未发表),表明其形成于MIS 2,根据地层地貌接触关系,末次冰期早阶段(MIS 4)的冰川规模要大于晚阶段(MIS 2),与波堆藏布主谷的情况一致。此外,基于以上测年结果及地层地貌关系,推测高侧碛垄可能形成于古乡冰期。

5.2 青藏高原及周边山地MIS 4冰川遗迹

冰川沉积物定量测年研究表明,MIS 4冰期冰川作用在青藏高原及周边山地广泛存在(图8)。在青藏高原东北部,东昆仑东吉康纳湖地区18和巴颜喀拉山19等地的冰碛物10Be暴露年代结果显示,MIS 4期间两地的古冰川曾大范围扩张。MIS 4冰期冰川作用遗迹在青藏高原中部的唐古拉山20-21以及南部的念青唐古拉山西段21和申扎杰岗日22等地区也有发现,这些地区冰碛物的10Be暴露年代结果揭示当时的古冰川规模要大于后续冰期冰川作用规模。在喜马拉雅山地区,如中段南坡Gorkha地区23,西段北坡纳木那尼峰地区24,南坡加瓦尔西北部25,以及西北段印度西北部地区26-29,这些地区的漂砾10Be暴露年代或冰碛物OSL年代皆证实了MIS 4冰期冰川作用的存在。形成于MIS 4期间的冰川遗迹在青藏高原西部,如阿里地区查西康米仁农坝河谷30,西昆仑31等地区也有保存。相较于以上地区,主要受西风影响的青藏高原西北部及天山等地区MIS 4冰期冰川遗迹数量较多。冰川沉积物10Be暴露年代结果表明,喀喇昆仑山南部熊彩岗日地区32,东南段拉达克山脉33、洪扎谷地34、塔什库尔干谷地35均保存有此次冰川作用的遗迹。在帕米尔高原地区,如东帕米尔瓦恰谷地36,帕米尔(塔吉克斯坦)雅什库尔湖37-39等地区也发现有MIS 4冰期冰川作用遗迹。天山地区,如东天山的博格达峰40、天格尔峰41和喀尔里克山42等地区,中天山的木扎尔特河谷43,以及西天山的阿莱山脉科克苏谷地44、特斯基阿莱太山脉45-46、阿拉巴什盆地47-48、吉萨尔山脉(塔吉克斯坦)49、伊尼尔切克谷地50等地区,这些地区冰碛物的OSL年代、ESR年代或10Be暴露年代结果也证实古冰川于MIS 4期间曾大规模扩张。此外,横断山脉东侧中段螺髻山51及横断山脉腹地白马雪山52等地区也保存有4阶段冰川作用遗迹。

图8

图8   青藏高原及其周边山地有测年数据的MIS 4冰川遗迹分布

注:1.螺髻山51,2.白马雪山52,3.念青唐古拉山东段(本研究),4.喜马拉雅山中段南坡Gorkha地区23,5.东昆仑东吉康纳湖地区18,6.巴颜喀拉山19,7.唐古拉山20-21,8.念青唐古拉山西段21,9.申扎杰岗日地区22,10.纳木那尼峰地区24,11.加尔瓦西北部地区25,12.印度西北部喜马拉雅山西北段26-272941,13.阿里地区查西康30,14.熊彩岗日地区32,15.拉达克山脉33,16.洪扎谷地34,17.塔什库尔干谷地35,18.西昆仑31,19.东帕米尔瓦恰谷地36,20.帕米尔(塔吉克斯坦)雅什库尔湖地区37-39,21.喀尔里克山[42],22.博格达峰40,23.天格尔峰41,24.木扎尔特河谷[43],25.伊尼尔切克谷地50,26.特斯基阿莱太山脉45-46,27.阿拉巴什盆地47,28.阿莱山脉科克苏谷地44,29.吉萨尔山脉(塔吉克斯坦)49

Fig.8   Dated glacial landforms formed during MIS 4 on the Tibetan Plateau and its surrounding mountains: 1. Luoji Mountain51, 2. Baimaxue Shan52, 3. eastern Nyainqêntanglha Range (this study), 4. Macha Khola Valley, Gorkha Himal23, 5. Lake Donggi Cona, eastern Kunlun Shan18, 6. Bayan Har Shan19, 7. Tanggula Shan20-21, 8. western Nyainqêntanglha Range21, 9. Mount of Jaggang, the Xainza Range22, 10. Gurla Mandhata (Naimon’anyi)24, 11. NW Garhwal, Central Himalayas25, 12. NW Himalaya of north-west India26-272941, 13. Miren Nongba Valley, Chaxikang30, 14. Mawang Gangri Range32, 15. Ladakh Range33, 16. Hunza Valley, Karakoram Mountains34, 17. Tashkurgan Valley, southeast Pamir35, 18. West Kunlun, Karakax31, 19. Waqia Valley, Chinese Pamir36, 20. Lake Yashilkul, Pamir, Tajikistan37-39, 21. Karlik Range, easternmost Tian Shan42, 22. Bogeda Peak area, Tianshan Range40, 23. Ala Valley of the Tianger Range, eastern Tian Shan41, 24. Muzart River Valley, central Tianshan Range, China43, 25. Inylchek Valley, eastern Kyrgyz Tian Shan50, 26. Teskey Ala-Too Range, Kyrgyz45-46, 27. Ala Bash Basin47, 28. Koksu Valley of the Alay Range47, 29. Gissar Range, Tajikistan49


综上,无论是西风区还是季风区,MIS 4期间古冰川均曾大规模扩张,表明4阶段冰川作用在青藏高原及其周边山地的出现具有普遍性。前人研究认为,青藏高原及其边缘山地MIS 4期间的冰川活动主要受控于中纬度西风334253-54,冰期时西风带来的低温和降水增加了冰川物质积累量,进而驱动冰川前进。特别是在中纬度西风为主要水汽来源的地区,如天山414749、帕米尔地区3544,MIS 4冰期为末次冰期最盛期,冰川作用范围为末次冰期以来最大。

5.3 藏东南MIS 4冰期冰川作用发生的气候条件

从MIS 5a开始,北半球低纬度太阳辐射持续减弱,至71 ka左右达到最低值55图9(b)]。青藏高原东部若尔盖盆地RM孔140 ka以来的湖泊碳、氧同位素记录显示,MIS 4期间气候较冷56,表明随着太阳辐射减弱,青藏高原季风区的气温也逐渐降至低值。根据云南腾冲青海湖泊沉积岩中所揭示的低纬陆地高分辨率年均温记录,MIS 4期间气温要比MIS 5a低2~3 ℃,而这样的温度变幅基本达到了季风区冰期-间冰期的变幅57图9(e)]。因此,藏东南地区山地冰川于MIS 4期间大范围扩张正是对冰期气温下降的响应,与青藏高原及其边缘山地的部分研究结果相符424953-54。深海钻孔中的δ18O记录也表明,MIS 4时期是大陆冰量最大时期之一58图9(c)]。

图9

图9   西藏东南部MIS 4冰期冰川作用与亚洲季风区的古气候记录对比

Fig.9   Climatic archives relative to the glacial activities during MIS 4 across the monsoonal Asia: probability density estimate of the OSL ages (Black dots show age of moraine, and the blue one indicates that of river terrace) (a), summer (June-July-August) mean isolation at 30°N55 (b), benthic δ18O records58 (c), speleothem δ18O data from Dongge, Hulu, and Sanbao Caves in China59 (d), reconstructed annual air temperature at Lake Tengchongqinghai57 (e)


这一时期的石笋δ18O记录指示了偏弱的季风强度59图9(d)],表明藏东南地区在该时期由西南夏季风带来的降水减少,此阶段增强的中纬度西风可能成其主要水汽来源3353-54。到了MIS 3时期,太阳辐射量的增加及季风的增强导致冰川开始后退3353。随着冰后期降水量及冰川融水量的增多,河流流量增加及搬运能力增强,大量的冰水沉积物首先堆积在河谷中,后期河流下切形成T2阶地。

6 结论

(1)基于前人研究和野外地貌调查,运用光释光测年技术,对西藏东南部波堆藏布流域疑似形成于末次冰期早阶段的冰碛垄进行测年,年代介于(56.4±4.2)~(65.9±3.9) ka之间,对应于MIS 4冰期。这一年代结果与青藏高原其他地区及边缘山地同时期的冰川测年结果具有可比性,表明MIS 4冰期冰川作用发生的普遍性。

(2)通过对比北半球低纬度地区夏季太阳辐射和亚洲季风区古气温和古降水指标记录,藏东南地区MIS 4期间的冰川扩张可能是对北半球低纬度地区太阳辐射减弱及气温下降的响应,与季风降水无关。MIS 4之后,印度夏季风增强,气温回升及降水增加导致冰川后退。

“白玉冰期”是李吉均先生于二十世纪七八十年代主导提出的第四纪冰川重要冰期概念,谨以此文,纪念李吉均院士!

参考文献

Li JiJunZheng BenxingYang Xijinet al. Glaciers in Tibet[M]. BeijingScience Press1986.

[本文引用: 4]

李吉均郑本兴杨锡金. 西藏冰川[M]. 北京科学出版社1986.

[本文引用: 4]

Zhou ShangzheXu LiubingColgan P Met al.

Cosmogenic 10Be dating of Guxiang and Baiyu Glaciations

[J]. Chinese Science Bulletin, 2007528): 1387-1393.

[本文引用: 2]

周尚哲许刘兵Colgan P M.

古乡冰期和白玉冰期的宇宙成因核素10Be定年

[J]. 科学通报, 2007528): 1387-1393.

[本文引用: 2]

Zhou ShangzheXie JinmingXianjiao Ouet al.

Evidence for glaciation predating MIS-6 in the eastern Nyainqêntanglha Range, southeastern Tibet

[J]. Science China: Earth Sciences, 2021644): 559-570.

[本文引用: 2]

周尚哲谢金明欧先交.

西藏东南部更早冰川作用新发现

[J]. 中国科学: 地球科学, 2021516): 982-993.

[本文引用: 2]

Yang WeiZhou ShangzheWang Jieet al.

Formation mechanism of hummocky moraine in the Bodui Zangbo Valley and its environmental significance

[J]. Journal of Glaciology and Geocryology, 2005272): 220-225.

[本文引用: 1]

杨威周尚哲王杰.

波堆藏布谷地冰碛丘陵形成机制及其环境意义

[J]. 冰川冻土, 2005272): 220-225.

[本文引用: 1]

Ou X JDuller G A TRoberts H Met al.

Single grain optically stimulated luminescence dating of glacial sediments from the Baiyu Valley, southeastern Tibet

[J]. Quaternary Geochronology, 201530314-319.

[本文引用: 2]

Jiao KeqinYao TandongJing Zhefanet al.

Variation of Zepu Glacier and environmental change in the eastern Nyainqentanglha Range since 3.2 ka BP

[J]. Journal of Glaciology and Geocryology, 2005271): 74-79.

[本文引用: 1]

焦克勤姚檀栋井哲帆.

3.2 ka BP以来念青唐古拉山东部则普冰川波动与环境变化

[J]. 冰川冻土, 2005271): 74-79.

[本文引用: 1]

Zhou S ZWang JXu L Bet al.

Glacial advances in southeastern Tibet during late Quaternary and their implications for climatic changes

[J]. Quaternary International, 20102181/2): 58-66.

[本文引用: 1]

Guo WanqinXu JunliLiu Shiyinet al.

The second glacier inventory dataset of China (version

1.0)[DS]. Lanzhou: Cold and Arid Regions Science Data Center, 2014.

[本文引用: 1]

郭万钦许君利刘时银.

中国第二次冰川编目数据集(V

1.0)[DS]. 兰州: 寒区旱区科学数据中心, 2014.

[本文引用: 1]

Mi DeshengXie ZichuLuo Xiangrui. Glacier inventory of China XI: the Ganga drainage basin and the Indus River drainage basin[M]. Xi’anXi’an Cartographic Publishing House2002.

[本文引用: 1]

米德生谢自楚罗祥瑞. 中国冰川编目XI: 恒河水系和印度河水系[M]. 西安西安地图出版社2002.

[本文引用: 1]

Murray A SWintle A G.

Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol

[J]. Radiation Measurements, 2000321): 57-73.

[本文引用: 1]

Chen R RZhou S ZLai Z Pet al.

Luminescence chronology of late Quaternary moraines and Last Glacial Maximum equilibrium-line altitude reconstruction from Parlung Zangbo Valley, south-eastern Tibetan Plateau

[J]. Journal of Quaternary Science, 2014296): 597-604.

[本文引用: 1]

Hu GYi C LZhang J Fet al.

Luminescence dating of glacial deposits near the eastern Himalayan syntaxis using different grain-size fractions

[J]. Quaternary Science Reviews, 2015124124-144.

Hu GYi C LLiu J Het al.

Glacial advances and stability of the moraine dam on Mount Namcha Barwa since the Last Glacial Maximum, eastern Himalayan syntaxis

[J]. Geomorphology, 2020365107246.

[本文引用: 1]

Lai Z PZoller LFuchs Met al.

Alpha efficiency determination for OSL of quartz extracted from Chinese loess

[J]. Radiation Measurements, 2008, 43(2/3/4/5/6): 767-770.

[本文引用: 1]

Aitken M J. An introduction to optical dating[M]. Oxford, UKOxford University Press1998.

[本文引用: 1]

Xianjiao OuZhang BiaoLai Zhongpinget al.

OSL dating study on the glacial evolutions during the Last Glaciation at Dangzi Valley in the eastern Qinghai-Tibetan Plateau

[J]. Progress in Geography, 2013322): 262-269.

[本文引用: 1]

欧先交张彪赖忠平.

青藏高原东部当子沟末次冰期冰川演化光释光测年

[J]. 地理科学进展, 2013322): 262-269.

[本文引用: 1]

Zeng LanhuaXianjiao OuChen Ronget al.

OSL dating on glacial sediments of the Last Glacial in headwater of Urumqi River, Tianshan

[J]. Journal of Glaciology and Geocryology, 2019414): 17-25.

[本文引用: 1]

曾兰华欧先交陈嵘.

天山乌鲁木齐河源末次冰期冰川沉积光释光测年

[J]. 冰川冻土, 2019414): 17-25.

[本文引用: 1]

Rother HStauch GLoibl Det al.

Late Pleistocene glaciations at Lake Donggi Cona, eastern Kunlun Shan (NE Tibet): early maxima and a diminishing trend of glaciation during the last glacial cycle

[J]. Boreas, 2017463): 503-524.

[本文引用: 3]

Heyman JStroeven A PCaffee M Wet al.

Palaeoglaciology of Bayan Har Shan, NE Tibetan Plateau: exposure ages reveal a missing LGM expansion

[J]. Quaternary Science Reviews, 20113015/16): 1988-2001.

[本文引用: 3]

Colgan P MMunroe J SZhou S Z.

Cosmogenic radionuclide evidence for the limited extent of Last Glacial Maximum glaciers in the Tanggula Shan of the central Tibetan Plateau

[J]. Quaternary Research, 2017652): 336-339.

[本文引用: 3]

Owen L AFinkel R CBarnard P Let al.

Climatic and topographic controls on the style and timing of late Quaternary glaciation throughout Tibet and the Himalaya defined by 10Be cosmogenic radionuclide surface exposure dating

[J]. Quaternary Science Reviews, 20052412/13): 1391-1411.

[本文引用: 6]

Dong G CZhou W JYi C Let al.

The timing and cause of glacial activity during the Last Glacial in central Tibet based on 10Be surface exposure dating east of Mount Jaggang, the Xainza Range

[J]. Quaternary Science Reviews, 2018186284-297.

[本文引用: 3]

Abramowski U.

The use of 10Be surface exposure dating of erratic boulders in the reconstruction of the late Pleistocene glaciation history of mountainous regions, with examples from Nepal and Central Asia

[D]. BayreuthGermany: University of Bayreuth2004.

[本文引用: 3]

Owen L AYi C LFinkel R Cet al.

Quaternary glaciation of Gurla Mandhata (Naimon’anyi)

[J]. Quaternary Science Reviews, 20102915/16): 1817-1830.

[本文引用: 3]

Sharma M COwen L A.

Quaternary glacial history of NW Garhwal, central Himalayas

[J]. Quaternary Science Reviews, 1996154): 335-365.

[本文引用: 3]

Taylor P JMitchell W A.

The Quaternary glacial history of the Zanskar Range, north-west Indian Himalaya

[J]. Quaternary International, 20006581-99.

[本文引用: 3]

Hedrick K ASeong Y BOwen L Aet al.

Towards defining the transition in style and timing of Quaternary glaciation between the monsoon-influenced Greater Himalaya and the semi-arid Transhimalaya of Northern India

[J]. Quaternary International, 20112361/2): 21-33.

[本文引用: 2]

Lee S YSeong Y BOwen L Aet al.

Late Quaternary glaciation in the Nun-Kun massif, northwestern India

[J]. Boreas, 20144367-89.

Saha SSharma M CMurari M Ket al.

Geomorphology, sedimentology and minimum exposure ages of streamlined subglacial landforms in the NW Himalaya, India

[J]. Boreas, 2015452): 284-303.

[本文引用: 3]

Chevalier M LHilley GTapponnier Pet al.

Constraints on the late Quaternary glaciations in Tibet from cosmogenic exposure ages of moraine surfaces

[J]. Quaternary Science Reviews, 2011305/6): 528-554.

[本文引用: 3]

Batbaatar JGillespie A RKoppes Met al.

Glacier development in continental climate regions of central Asia

[M]// Untangling the Quaternary period: a legacy of Stephen C. Porter. Boulder, CO, USAThe Geological Society of America2021119-149.

[本文引用: 3]

Amidon W HBookhagen BAvouac J Pet al.

Late Pleistocene glacial advances in the western Tibet interior

[J]. Earth and Planetary Science Letters, 2013381210-221.

[本文引用: 3]

Dortch J MOwen L ACaffee M W.

Timing and climatic drivers for glaciation across semi-arid western Himalayan-Tibetan orogen

[J]. Quaternary Science Reviews, 201378188-208.

[本文引用: 6]

Owen L AFinkel R CCaffee M Wet al.

Timing of multiple late Quaternary glaciations in the Hunza Valley, Karakoram Mountains, northern Pakistan: defined by cosmogenic radionuclide dating of moraines

[J]. Geological Society of America Bulletin, 2002114593-604.

[本文引用: 3]

Owen L AChen JHedrick K Aet al.

Quaternary glaciation of the Tashkurgan Valley, southeast Pamir

[J]. Quaternary Science Reviews, 20124756-72.

[本文引用: 4]

Hedrick K AOwen L AChen Jet al.

Quaternary history and landscape evolution of a high-altitude intermountain basin at the western end of the Himalayan-Tibetan orogen, Waqia Valley, Chinese Pamir

[J]. Geomorphology, 2017284156-174.

[本文引用: 3]

Zech RAbramowski UGlaser Bet al.

Late Quaternary glacial and climate history of the Pamir Mountains derived from cosmogenic 10Be exposure ages

[J]. Quaternary Research, 2005642): 212-220.

[本文引用: 3]

Röhringer IZech RAbramowski Uet al.

The late Pleistocene glaciation in the Bogchigir Valleys (Pamir, Tajikistan) based on 10Be surface exposure dating

[J]. Quaternary Research, 2012783): 590-597.

Stübner KGrin EHidy A Jet al.

Middle and late Pleistocene glaciations in the southwestern Pamir and their effects on topography

[J]. Earth and Planetary Science Letters, 2017466181-194.

[本文引用: 3]

Zhao J DLai Z PLiu S Yet al.

OSL and ESR dating of glacial deposits and its implications for glacial landform evolution in the Bogeda Peak area, Tianshan Range, China

[J]. Quaternary Geochronology, 201210237-243.

[本文引用: 3]

Li Y KLiu G NChen Y Xet al.

Timing and extent of Quaternary glaciations in the Tianger Range, eastern Tian Shan, China, investigated using 10Be surface exposure dating

[J]. Quaternary Science Review, 2014987-23.

[本文引用: 6]

Chen Y XLi Y KWang Yet al.

Late Quaternary glacial history of the Karlik Range, easternmost Tian Shan, derived from 10Be surface exposure and optically stimulated luminescence datings

[J]. Quaternary Science Reviews, 201511517-27.

[本文引用: 5]

Zhao J DSong Y GKing J Wet al.

Glacial geomorphology and glacial history of the Muzart River valley, Tianshan Range, China

[J]. Quaternary Science Reviews, 20102911/12): 1453-1463.

[本文引用: 3]

Abramowski UBergau ASeebach Det al.

Pleistocene glaciations of Central Asia: results from 10Be surface exposure ages of erratic boulders from the Pamir (Tajikistan), and the Alay-Turkestan Range (Kyrgyzstan)

[J]. Quaternary Science Reviews, 2006259/10): 1080-1096.

[本文引用: 3]

Narama CKondo RTsukamoto Set al.

OSL dating of glacial deposits during the Last Glacial in the Terskey-Alatoo Range, Kyrgyz Republic

[J]. Quaternary Geochronology, 200721/2/3/4): 249-254.

[本文引用: 3]

Narama CKondo RTsukamoto Set al.

Timing of glacier expansion during the Last Glacial in the inner Tien Shan, Kyrgyz Republic by OSL dating

[J]. Quaternary International, 20091991/2): 147-156.

[本文引用: 3]

Koppes MGillespie A RBurke R Met al.

Late Quaternary glaciation in the Kyrgyz Tien Shan

[J]. Quaternary Science Reviews, 2008277/8): 846-866.

[本文引用: 5]

Zech R.

A late Pleistocene glacial chronology from the Kitschi-Kurumdu Valley, Tien Shan (Kyrgyzstan), based on 10Be surface exposure dating

[J]. Quaternary Research, 2012772): 281-288.

[本文引用: 1]

Zech RRöhringer ISosin Pet al.

Late Pleistocene glaciations in the Gissar Range, Tajikistan, based on 10Be surface exposure dating

[J]. Palaeogeography, Palaeoclimatology, Palaeoecology, 2013369253-261.

[本文引用: 5]

Lifton NBeel CHättestrand Cet al.

Constraints on the late Quaternary glacial history of the Inylchek and Sary-Dzaz Valleys from in situ cosmogenic 10Be and 26Al, eastern Kyrgyz Tian Shan

[J]. Quaternary Science Reviews, 201410177-90.

[本文引用: 3]

Zhang WeiLiu LiangChai Leet al.

Characteristics of Quaternary glaciations using ESR dating method in the Luoji Mountain, Sichuan Province

[J]. Quatenary Sciences, 2017372): 281-292.

[本文引用: 3]

张威刘亮柴乐.

基于年代学证据的螺髻山第四纪冰川作用研究

[J]. 第四纪研究, 2017372): 281-292.

[本文引用: 3]

Zhang WeiBi WeiliLiu Beibeiet al.

Geochronology constrainted on late Quaternary glaciation of Baimaxue Shan

[J]. Quatenary Sciences, 2015351): 20-37.

[本文引用: 3]

张威毕伟力刘蓓蓓.

基于年代学约束的白马雪山晚第四纪冰川作用

[J]. 第四纪研究, 2015351): 29-37.

[本文引用: 3]

Murari M KOwen L ADortch J Met al.

Timing and climatic drivers for glaciation across monsoon-influenced regions of the Himalayan-Tibetan orogen

[J]. Quaternary Science Reviews, 201488159-182.

[本文引用: 4]

Sharma SChand PBisht Pet al.

Factors responsible for driving the glaciation in the Sarchu Plain, eastern Zanskar Himalaya, during the late Quaternary

[J]. Journal of Quaternary Science, 2016315): 495-511.

[本文引用: 3]

Berger ALoutre M.

Insolation values for the climate of the last 10 million years

[J]. Quaternary Science Reviews, 1991104): 297-317.

[本文引用: 2]

Wu J LWang S MPan H Xet al.

Climatic variations in the past 140 ka recorded in core RM, east Qinghai-Xizang Plateau

[J]. Science in China: Series D Earth Sciences, 1997404): 443-448.

[本文引用: 1]

Zhao CRohling E JLiu Zet al.

Possible obliquity-forced warmth in southern Asia during the Last Glacial stage

[J]. Science Bulletin, 20216611): 1136-1145.

[本文引用: 2]

Lisiecki L ERaymo M E.

A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records

[J/OL]. Paleoceanography, 2005201) [2021-06-10]. .

URL     [本文引用: 2]

Cheng HEdwards R LSinha Aet al.

The Asian monsoon over the past 640,000 years and ice age terminations

[J]. Nature, 20165347609): 640-646.

[本文引用: 2]

/