唐古拉山垭口地区的第四纪冰川测年新研究

在野外综合考察的基础上,对唐古拉山垭口地区末次冰期的冰碛漂砾(或有冰川擦痕的露头)进行了宇生核素10Be暴露年龄的测定,得到(16.1±1.7)ka BP、(31.9±3.4)ka BP、(41.4±4.3)kaBP和(66.8±4.3)ka BP 4个测年数据.结合前人对本地区研究和测年的资料,确定该区更新世经历了4次较大规模的冰川作用:中更新世晚期的倒数第二次冰期、晚更新世中晚期的末次冰期早冰阶、间冰阶和晚冰阶,依次与MIS6、MIS4、MIS3和MIS2阶段对应;全新世经历了2次小的冰进:新冰期和小冰期,它们的时代与青藏高原其它地区新冰期和小冰期的时代基本一致.末次盛冰期的冰川范围十分有限,并且MIS3阶段的冰进规模远远超过了末次盛冰期.早期考察中所命名的唐古拉冰期和巴斯错冰期的时代是中更新世晚期(MIS6)和末次冰期早冰阶(MIS4),扎加藏布冰期的冰碛可能是末次冰期的冰碛叠加在倒数第二次冰期的冰碛物之上,而又经过后期作用改造而形成的一套冰碛.在该区老的冰碛物上没有测定出MIS6阶段之前的年代数据,可能是由后期的破坏或采集的样品不够充分所致,因此对本区最早冰川作用的时代还有待于进一步深入研究.     

玉龙雪山冰川沉积序列OSL定年

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。     

新疆阿尔泰山哈纳斯河流域及其邻域第四纪冰川作用

根据新疆阿尔泰山哈纳斯河流域及其邻域第四纪冰川遗迹的类型和特征,哈纳斯河流域第四纪时期至少发生过5次明显的冰川事件,即倒数第三冰期,倒数第二冰期,倒数第一冰期(末次冰期),新冰期和小冰期。其中,更新世的3次冰川作用规模巨大,倒数第三冰期的冰川呈半覆盖式,倒数第二冰期和倒数第一冰期时发育了长达96km以上的大型山谷冰川。古冰川属于冰温高、活动性大和侵蚀能力强的温冰川。从新到老,每次冰期的雪线下降幅度一次比一次大。     

贡嘎山第四纪冰川遗迹及冰期划分

在对贡嘎山现代冰川和古冰川考察研究的基础上，结合定位观测分析，对该区第四纪冰川遗迹进行了深入讨论，划分出三次冰期，即中更新世早期的倒数第三次冰期，中更新世晚期的倒数第二次冰期和晚更新世的末次冰期，以及全新世的新冰期和小冰期。提出在早更新世时，由于山体未达到当时冰川发育的雪线高度，所以未发育冰川；中更新世早期的冰期冰川为半覆盖式冰川类型，规模不大；中更新世晚期的冰期冰川是本区最大冰川作用时期，形成网状山麓冰川，东坡冰川曾达磨西台地；晚更新世冰期冰川以山谷冰川为主，以后规模逐次缩小。     

唐古拉山地区第四纪冰川作用与冰川特征

自中更新世以来,唐古拉山地区发生过3次更新世冰川作用(即昆仑冰期、倒数第二次冰期和末次错冰期)和2次全新世晚期冰进(即新冰期和小冰期冰进).昆仑冰期(最大冰期)发生在中更新世早期(0.80～0.60MaBP),不仅是本区最早的一次冰期,而且也是冰川规模最大的一次冰期,当时的冰川规模比现代冰川大16～18倍;倒数第二次冰期发生在中更新世晚期(0.30～0.135MaBP),比现代冰川大13～15倍;末次冰期发生在晚更新世晚期,应分为末次冰期早冰阶(75.0～58.0kaBP)和晚冰阶(32.0～15.0kaBP,23.0kaBP时达到极盛),但在唐古拉山地区截止目前还未找到早冰阶的冰川遗迹,因此,只对末次冰期的晚冰阶(LMG)进行了探讨.LMG时,冰川规模比现代冰川大10倍;新冰期发生在全新世高温期后,冰碛物的¹⁴C测年为(3540±160)aBP,冰川规模略大于现代冰川;小冰期发生在15～1世纪,冰川规模已接近于现代冰川.由于青藏高原的上升,对高原腹部地区引起的干旱化过程和水分严重不足,使唐古拉山地区的冰川自昆仑冰期以来,冰川规模一次比一次明显的减小.     

玉龙山西麓更新世冰川作用及其与金沙江河谷发育的关系

在玉龙山东麓更新世冰川作用研究的基础上,对其西麓和金沙江河谷中的古冰川与冰水沉积物的分布和特征进行了调查.结合ESR测年,划分出4次冰期,即0.7～0.6MaB.P.的玉龙冰期,0.53～0.45MaB.P.的干海子冰期,0.31～0.13MaB.P.的丽江冰期和晚更新世中晚期的大理冰期,其中玉龙冰期为规模较大的山麓冰川,丽江和大理冰期为山谷冰川,干海子冰期则为山麓冰川与山谷冰川的过渡类型.来自玉龙山西坡的玉龙冰期冰碛物充填于现今金沙江谷底的事实和大具金沙江下渡口西岸早更新世金沙江砾石层的发现表明,金沙江在早更新世早期即已存在,也说明了在该段金沙江河谷中多处发现的湖相沉积物是冰川沉积堰塞河谷而成石鼓古湖的结果.在该段金沙江河谷中仅发现拔河50m左右以内的4级河流阶地,且往往以这些湖相沉积为基座的现象,则是石鼓古湖被外泄后金沙江现代河谷形成的结果.     

利用陆面岩石中生成的宇生同位素重建冰川漂砾运动历史的尝试

冰川漂砾的形成年代通常难以直接测定，并且漂砾形成以后是否被再次搬运或者移动过，更是无法知道。本文研究发现，通过测试砾石不同部位的宇生同位素，不仅可以测定砾石形成的时代，而且可以确定砾石再次被搬运或者被翻转的年代，从而恢复砾石运动的历史。本文以石英中生成的宇生同位素^10Be，对青藏高原东南部海子山的冰川漂砾进行了探讨，结果表明该砾石形成于倒数第二次冰期(186～128ka BP之间)，在末次冰期中再次被冰川搬运，使之反转。该方法不局限于^10Be和冰川漂砾，也适用于其他陆面岩石中生成的宇生同位素以及其他成因的石块或者砾石。因此为探讨冰川作用、泥石流活动、重力崩塌等过程提供了一种重要的方法和技术途径。     

贡嘎山东麓第四纪冰川作用与磨西台地成因探讨

青藏高原东部的最高峰贡嘎山（海拔7556m)东麓磨西河流域发育了三次更新世冰期，分别为雅家埂、南门关、贡嘎冰期，其中燕子沟的倒数第二次冰期（南门关冰期）的冰川一直伸到磨西镇下街磨西饭店北，古冰川阻塞主谷，在新兴与南门关沟之间的堡子坝区形成冰川阻塞湖，在磨西镇上街东，该期古冰川覆盖在谢家河坝东面山坡上，融水切形成峡谷，冰退过程中又在峡谷西基岩丘社形成该期古冰川覆盖在谢家河坝东面山坡上，融水深切形成峡谷，冰退过程中又在峡谷西基岩丘陵旁形成冰水湖，南门关冰期后的间冰期时，小湖变干发育了红色古土壤层，该期的红色古土壤层在磨用镇下街南的古冰川与冰川泥石流沉积层顶面也有保存。证明磨西台地的主体为倒数第二次冰期的冰川堆积物，其中也包括有冰水砂砾层透镜体和冰湖相等沉积，磨西台地出露地表的巨大砾石，直径在10－20m之间，多数为冰川表面的消融碛，也可能有冰川泥充夹带的大岩块，磨西台地两侧断续分布有4级冰水阶地以及磨西饭店以下的磨西台地尾部均为末次期后期至全新世的冰水沉积，其中也含有泥石流堆积物。     

甘孜绒坝岔古冰川演化与黄土古土壤对比研究

横断山脉绒坝岔，保留有从倒数第二次冰期到新冰期的较完整的冰川沉积序列。对冰碛物进行了ESR测年，其分别形成于5．6kaBP、新冰期与末次冰期之间、16．3kaBP、18．7kaBP、43．7kaBP以及倒数第二次冰期。TL测年结果显示，甘孜雅砻江江畔阶地黄土从末次冰期之初开始堆积，结合甘孜黄土-古土壤序列代用指标的综合分析，发现绒坝岔冰碛物形成年代与甘孜剖面黄土、古土壤沉积年代有较好的对应关系。末次冰盛期(LGM)，绒坝岔冰碛垄走向有一次接近90。的改变；末次冰期间冰段，对应于MIS3b，其冰川规模甚至超过了LGM时期。     

青藏高原唐古拉山口第四纪冰碛层划分及其地质环境意义

在对唐古拉山口现代冰川和古冰川考察研究的基础上，结合定位观测资料和TL、^10B-^26Al-^21Ne及^14C测年数据，对区内第四纪冰川遗迹进行了深入讨论，划分出二次冰期(即中更新世晚期的倒数第二次冰期、晚更新世中一晚期的末次冰期)和二次全新世冰进(即新冰期和小冰期)。提出在早更新世时，由于山体未达到当时冰川发育的雪线高度，所以未发育冰川。但在唐古拉山口地区，截止目前还未找到中更新世早期的倒数第三次冰期的冰川遗迹，由于高原隆升的滞后性和冰川发育的延滞效应及“亚洲干极”的耦合，推测仍只发育局部冰川作用。进一步研究表明，古今雪线由高原边缘向腹地升高，唐古拉山地区高出边缘1500m左右，生动表现了“亚洲干极”的作用；广泛分布的湖群说明羌塘地区是一个大江大河尚未伸入的内流地区，意味着青藏高原是个年青的高原。由于青藏高原的隆升，对高原腹地引起的干旱化过程和水分严重不足，使唐古拉山地区的冰川自倒数第二次冰期以来，冰川规模一次比一次明显地减小。     

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。     

Pleistocene sediments of the eastern Barents Sea (Central Deep and Murmansk Bank): Communication 2. Lithological composition and formation conditions

Llithology of massive diamictons was studied in two areas of the eastern Barents Sea using cores and geophysical data. These sediments dominate in the Pleistocene section as two seismostratigraphic complexes (SSC): Upper Weichselian (SSC III) and locally distributed Lower Weichselian (SSC V). Diamictons of these complexes represent tills produced by the geological activity of the Pleistocene Novaya Zemlya and Scandinavian ice sheets. The Upper Weichselian glacial sequence is laterally heterogeneous. It includes two seismic facies represented by ordinary (overconsolidated) tills (they also constitute SSC V) and a spacious moraine of the specific type with the normally consolidated sediments (they avoided compaction by the ice load) and certain lithological specifics. The last glacial sediments were formed in a specific subglacial setting similar to the sediments under fast ice streams of Antarctica. However, the specific features allow us to define these sediments as a new (Barents Sea) facies of tills related to zones of intense basal melting of glaciers.     

Moraine chronosequence of the Donnelly Dome region, Alaska

We present ¹⁰Be exposure ages from moraines in the Delta River Valley, a reference locality for Pleistocene glaciation in the northern Alaska Range. The ages are from material deposited during the Delta and Donnelly glaciations, which have been correlated with MIS 6 and 2, respectively. ¹⁰Be chronology indicates that at least part of the Delta moraine stabilized during MIS 4/3, and that the Donnelly moraine stabilized ∼ 17 ka. These ages correlate with other dates from the Alaska Range and other regions in Alaska, suggesting synchronicity across Beringia during pulses of late Pleistocene glaciation. Several sample types were collected: boulders, single clasts, and gravel samples (amalgamated small clasts) from around boulders as well as from surfaces devoid of boulders. Comparing ¹⁰Be ages of these sample types reveals the influence of pre/post-depositional processes, including boulder erosion, boulder exhumation, and moraine surface lowering. These processes occur continuously but seem to accelerate during and immediately after successive glacial episodes. The result is a multi-peak age distribution indicating that once a moraine persists through subsequent glaciations the chronological significance of cosmogenic ages derived from samples collected on that moraine diminishes significantly. The absence of Holocene ages implies relatively minor exhumation and/or weathering since 12 ka.     

唐古拉山东段布加岗日南坡小冰期冰进的10Be暴露测年研究

高寒地区形态独特的冰川侵蚀与沉积地形是过去冰川变化最直接的证据,包含有重要的古气候环境变化信息。根据山地冰川沉积序列,通常将分布在现代冰碛地形外围形态较完好的多列冰碛垄的形成时间推定为小冰期。小冰期冰进的时间与规模是理解与重建近千年以来古气候环境变化的基础及较准确预测未来气候环境变化的关键。本研究应用¹⁰Be暴露测年技术对唐古拉山东段布加岗日南坡拥曲河源区西（主）谷与东（悬）谷中基于地貌关系与沉积序列推定为小冰期的第一套冰碛垄M_W1与M_E1进行定年。测得M_W1冰碛垄4个样品的¹⁰Be年龄分别为（155±23） a、（197±27） a、（218±26） a和（273±31） a;M_E1冰碛垄3个样品的¹⁰Be年龄分别为（262±30） a、（186±28） a和（131±25） a。使用P-CAAT法分析得出它们的年龄为（203±52） a（n=4）和（162±58） a（n=3）。地貌关系、沉积序列、冰碛垄的形态特征、土壤发育与植被覆盖以及测年结果等共同表明拥曲河源区西谷与东谷中的第一套冰碛垄形成于小冰期。结合周边地区的研究成果及古气候环境代用指标可以推断降温是这次冰进的主因。     

Exposure ages from relict lateral moraines overridden by the Fennoscandian ice sheet

Lateral moraines constructed along west to east sloping outlet glaciers from mountain centred, pre-last glacial maximum (LGM) ice fields of limited extent remain largely preserved in the northern Swedish landscape despite overriding by continental ice sheets, most recently during the last glacial. From field evidence, including geomorphological relationships and a detailed weathering profile including a buried soil, we have identified seven such lateral moraines that were overridden by the expansion and growth of the Fennoscandian ice sheet. Cosmogenic ¹⁰Be and ²⁶Al exposure ages of 19 boulders from the crests of these moraines, combined with the field evidence, are correlated to episodes of moraine stabilisation, Pleistocene surface weathering, and glacial overriding. The last deglaciation event dominates the exposure ages, with ¹⁰Be and ²⁶Al data derived from 15 moraine boulders indicating regional deglaciation 9600 ± 200 yr ago. This is the most robust numerical age for the final deglaciation of the Fennoscandian ice sheet. The older apparent exposure ages of the remaining boulders (14,600-26,400 yr) can be explained by cosmogenic nuclide inheritance from previous exposure of the moraine crests during the last glacial cycle. Their potential exposure history, based on local glacial chronologies, indicates that the current moraine morphologies formed at the latest during marine oxygen isotope stage 5. Although numerous deglaciation ages were obtained, this study demonstrates that numerical ages need to be treated with caution and assessed in light of the geomorphological evidence indicating moraines are not necessarily formed by the event that dominates the cosmogenic nuclide data.     

Late Wisconsinan glaciation models of northern Maine and adjacent Canada

Surficial stratigraphic units of Aroostook County, Maine, have been mapped and formal stratigraphic names for these units are proposed. Evidence exists for at least two distinct glacial phases which are represented by three tills. Two of these tills were deposited penecontemporaneously either as the result of coalescing ice sheets or as the result of the thermal regime existing within a single ice sheet. The oldest till is named the St. Francis and is correlated with the Chaudière Till of southeastern Quebec. The other tills are named the Mars Hill and Van Buren tills, respectively, and are correlated with the Lennoxville till of southeastern Quebec. Interbedded stratified sediments associated with the St. Francis till are correlated with the Gayhurst Formation. Stratified sediments associated with Van Buren and Mars Hill tills are correlated with post Lennoxville sediments of Quebec. Granite-gneiss erratics of Canadian Shield provenance in the Van Buren till indicate advance of the Laurentide ice into northern Maine during late Wisconsinan time. Moraines in southern Aroostook County with associated outwash and eskers record general recession from coastal Maine. Recession occurred after the formation of the Pineo Ridge moraine in Maine and the St. Antonin-Highland Front moraine complex in Quebec. The Caribou-Winterville moraine complex in northern Maine marks the boundary between the penecontemporaneously deposited Van Buren and Mars Hill surface tills and is correlated with the Grand Falls moraine at Grand Falls, New Brunswick.     

玉龙雪山西麓原状冰碛土CT扫描试验研究

冰碛土是冰川行进融化过程中漂石、碎石、砂砾、粉土和黏土在毫无分选的条件下快速混杂堆积生成的一种特殊岩土材料,由其引发的工程问题日益受到岩土工程界关注。砾石颗粒细观组构是冰碛土独特沉积历史的反映,直接影响土体的岩土力学性质,但迫于原状冰碛土样极难取得,岩土工程领域迄今罕有研究。对此,采用人工精细切削的方式,成功取得了玉龙雪山西麓原状冰碛土样,并对取回的6块冰碛土原状样进行了CT扫描,首次获得了冰碛土内部真实细观组构图像。借助Matlab对CT图片进行二值化和消噪处理后,运用常规统计方法对冰碛土内砾石颗粒的面含石量、颗粒定向以及颗粒形状等剖面组构指标进行了描述。结果表明,垂直剖面之间的统计数据差异较小,但垂直剖面与水平剖面之间差异较大。     

Late Pleistocene Glaciations in the Northwestern Sierra Nevada, California

Pleistocene fluvial landforms and riparian ecosystems in central California responded to climate changes in the Sierra Nevada, yet the glacial history of the western Sierra remains largely unknown. Three glacial stages in the northwestern Sierra Nevada are documented by field mapping and cosmogenic radionuclide surface-exposure (CRSE) ages. Two CRSE ages of erratic boulders on an isolated till above Bear Valley provide a limiting minimum age of 76,400±3800 ¹⁰Be yr. Another boulder age provides a limiting minimum age of 48,800±3200 ¹⁰Be yr for a broad-crested moraine ridge within Bear Valley. Three CRSE ages producing an average age of 18,600±1180 yr were drawn from two boulders near a sharp-crested bouldery lateral moraine that represents an extensive Tioga glaciation in Bear Valley. Nine CRSE ages from striated bedrock along a steep valley transect average 14,100±1500 yr and suggest rapid late-glacial ice retreat from lower Fordyce Canyon with no subsequent extensive glaciations. These ages are generally consistent with glacial and pluvial records in east-central California and Nevada.     

北京西山灵岳寺古冰川沉积物何在?

北京西山灵岳寺附近的第四纪沉积物不是真正的古冰川沉积物。该处山腰凹地中一套以粗大砾石为主的混杂堆积是较典型的复式稀性泥石流堆积体,其时代为晚更新世之前,而不是晚更新世末期产物。所谓晚更新世末期的冰川堆积体和冰蚀地貌,实际上是不存在的。晚更新世时期,北京西山地区属冰缘环境,而非冰川环境。