川西沙鲁里山第四纪冰川及与邻区之对比

沙鲁里山是研究第四纪冰川的最佳场所之一。可划分四个冰期,第一冰期为大陆冰盖,第二、三期及现代冰川为山岳冰川;整体反映第四纪地壳不断抬升,气候不断变暖,冰川不断向高山退缩的过程。     

季风亚洲末次冰期的古冰川遗迹

季风亚洲末次冰期可统一称为大理冰期,古冰川首次出现于东亚海岸山地,内陆高山高原则冰川规模缩小。早期大理冰期冰川规模大于晚期,是季风亚洲的特色。古雪线在亚洲东海岸形成向南弯曲的大槽,是大理冰期夏季风衰弱、海陆的干湿对比加剧以及东亚大槽南移的结果。53000—27000aB.P.之间为萨拉乌苏-卡尔金斯克大间冰段,气候冷暖多变,西伯利亚冻土融化,华北平原为喜冷云杉林占据,内陆湖水面普遍升高。构造运动对古冰川发育有明显影响。青藏高原大冰盖是不存在的。     

障壁岛—潟湖沉积特征及模式:以美国普拉姆岛上更新统—全新统为例*

普拉姆岛(Plum island)是美国东北部缅因湾最大的障壁海岸,岛内向陆一侧为新英格兰地区最大潟湖和沼泽区,它们是晚第四纪末次冰期冰川作用和冰后期海岸作用的沉积响应。通过普拉姆岛研究区上更新统—全新统160个钻孔描述,识别出8种沉积物: 泥炭、冰川黏土、黏土、粉砂、细砂、中粗砂、砾、坠石。根据沉积物类型及其组合特征,结合沉积环境,共划分出8种沉积微相: 障壁沙丘、滨岸沙、水下临滨沙、河道、潮汐水道、潟湖、潮坪、沼泽。研究区在晚第四纪末次冰盛期(MIS2)被劳伦斯蒂德冰盖(Laurentide Ice Sheet)覆盖,发育冰川地貌,冰川泥覆盖在基岩之上,形成底层沉积; 冰后期(MIS1),冰盖消融,海平面发生变化,在冰川地貌鼓丘附近形成沙坝,最终沉积演化为障壁岛—潟湖环境,潟湖通过潮汐水道与广海相连通。     

末次冰期以来中国自然环境变迁及其与全球变化的关系

末次冰期我国西部的冰川长度比现代冰川长2—5倍,雪线低300—1080m;东部多年冻土区南界在33°20′—33°40′N,青藏高原多年冻土区东北部的下界在海拔2200—2600m 处;黄、东海海平面下降130—155m;经向环流加强,北方冷空气增强。末次冰期以后冰川阶段性退缩,多年冻土区阶段性缩小,海平面间歇性上升;8000—6000aB.P.为高温期,出现2—5m 高海面,5600—5000aB.P.气温短暂下降,海平面突然回落,冰川有所前进;3000aB.P.的新冰期和15—19世纪的小冰期,气候、冰川和海平面都有显著变化。哺乳动物的绝灭和迁徙是自然和人为双重影响的结果。这些变化都是全球变化的表现。     

天山末次冰期以来干旱化过程的冰川证据

依据天山7个有确切年代学资料的典型地区进行冰川面积和平衡线高度等重建,揭示天山地区末次冰期以来冰川经历的扩张和收缩过程。冰川规模在MIS 4~MIS 3大幅度扩张,形成大规模的复合型山谷冰川和山麓冰川;MIS 2冰川扩张显著,但远不及MIS 4~MIS 3,许多山区形成大型山谷冰川;全新世新冰期NG和小冰期LIA都略有扩张,冰碛垄分布在现代冰川外围,冰川类型与现在一致。冰川平衡线高度的降幅亦表现为MIS 4~MIS 3最大,MIS 2以后降幅递减。MIS 4~MIS 3天山冰川大规模扩张与欧亚冰盖演化,巨大冰前湖泊、广阔的湿地的形成为西风提供更多水气带到天山有关;MIS 2至今,随着欧亚冰盖减小到消失,西风带来的水气渐少,干冷的蒙古高压逐渐加强,制约了冰川规模扩张。     

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.     

长白山现代理论雪线和古雪线高度

根据冰川地貌和地形特征、岩性、冰川沉积物的风化程度以及OSL测年结果,认为长白山地区发育两期冰川作用,即末次冰盛期和晚冰期,测年结果分别为20.0±2.1ka和11.3±1.2ka。根据平衡线（ELA）处6～8月多年平均气温（T）和年降水量（P）的关系,计算长白山现代理论雪线高度为3380±100m。通过积累区面积比率AAR（accumulation-arearatio）、冰川末端到山顶高度TSAM（the terminal to summit altitudinal）,冰川末端至分水岭平均高度Hofer（the terminal to average elevation of the catchment area）、末端至冰斗后壁比率THAR（toe-to headwall altitude ratios）、冰斗底部高程CF（cirque-floor altitudes method）、侧碛堤最大高度法MELM（maximum elevation of lateral moraines）等方法计算该区末次冰盛期雪线高度为2250～2383m,平均值2320±20m。考虑到末次冰盛期后地壳上升20m,当时雪线的实际高度为2300±20m,冰盛期的雪线降低值为10⁸0±100m。晚冰期北坡和西坡的雪线高度分别为2490m和2440m,平均值2465m,考虑新构造运动后的雪线实际高度2454m,降低值926±100m。长白山新构造运动（LGM上升约20m,晚冰期上升约11m）在末次冰盛期以来对冰川发育的影响不明显。     

念青唐古拉山脉西段第四纪冰川作用

在念青唐古拉山脉西段南北两麓及切割山脉的各沟谷中,分布着3套更新世冰川沉积物。在本区最长的现代冰川———西布冰川的前端,也分布着3组全新世冰川沉积物。根据这些冰川沉积物的地层层序和冰川与湖泊沉积物的电子自旋共振(ESR)、U系等时线和光释光(OSL)年龄测定结果,本文将念青唐古拉山脉西段所发生的3次更新世冰川作用,分别命名为宁中冰期、爬然冰期和拉曲冰期,并与青藏高原的邻近地区进行了对比。各次冰期的冰川性质分别为大型山麓冰川、中小型山谷冰川和小型山谷冰川。全新世时期,现代冰川也有新冰期和小冰期的两次冰川前进。近期冰川则发生了明显的后退。本文还根据念青唐古拉山脉两麓冰前期、历次冰期和现代砾石层的砾石岩性及其与山脉各构造层岩性组成的对比,讨论了山脉的剥蚀与隆升问题     

东北地区末次冰期以来气候地貌的若干特征

末次冰期,长白山天池周围有冰斗发育,高2200m左右,东北的广大地区为冰缘环境。许多冰缘形态至今控制着地貌景观。冰后期,长白山的冰川地貌受到冰缘环境的控制,广大地区的冰缘地貌则受到温暖环境的改造。作为气候地貌界限的冰雪线,由末次冰期的44—45°N移至今日的51°N附近。末次冰期以来,气候地貌带表现出沿经度和纬度平行移动的特点     

季风的发展与冰川的消失——从台湾高山末次冰期冰川发育特征说起

台湾高山有无第四纪冰川之争,经历60a后终于得到澄清．此次查明台湾雪山主峰区有3套 不同时期的冰川遗迹．如冰斗湖、冰坎、大型磨光面和擦痕以及冰碛垄等,分别命名为山庄冰阶(末 次冰期早期．44.25±3.72ka BP)、黑森林冰阶(末次冰期最盛,18.26±1.52 ka BP)、雪山冰阶(末次冰 期晚期,10.68±0.84 ka BP)尤其以早期冰川规模大为特征．澄清了地学界近65a来的怀疑,将为 全球变化研究增添新内容．     

A critical review and re-investigation of the Pleistocene deposits between Cranfield Point and Kilkeel,Northern Ireland: Implications for regional sea-level models and glacial reconstructions of the northern Irish Sea basin

The coastline of County Down includes sites that are pivotal to understanding the history of the last glaciation of the northern Irish Sea Basin in relation to relative sea level and regional glacial readvances. The cliff sections display evidence that has been used to underpin controversial models of glaciomarine sedimentation in isostatically-depressed basins followed by emergent marine and littoral environments. They also provide crucial evidence claimed to constrain millennial-scale ice sheet oscillations associated with uniquely large and rapid sea-level fluctuations. This paper reviews previous work and reports new findings that generally supports the ‘terrestrial’ model of glaciation, involving subglacial accretion and deformation of sediment beneath grounded ice. Deep troughs were incised into the till sheet during a post Late Glacial Maximum draw-down of ice into the Irish Sea Basin. Ice retreat was accompanied by glaciomarine accretion of mud in the troughs during a period of high relative sea level. The trough-fills were over-ridden, compacted, deformed and truncated during a glacial re-advance that is correlated with the Clogher Head Readvance. Grounding-line retreat accompanied by rapid subaqueous ice-proximal sedimentation preserved a widespread subglacial stone pavement. Raised beach gravels cap the sequence. The evidence supports an uninterrupted fall in relative sea level from c. 30?m that is consistent with sea level curves predicted by current glacio-isostatic adjustment modelling. Critical evidence previously cited in support of subaerial dissection of the troughs, and hence rapid fall and rise in relative sea level prior to the deposition of the glaciomarine muds, is not justified.     

Late Wisconsinan glaciation and postglacial relative sea-level change on western Banks Island,Canadian Arctic Archipelago

The study revises the maximum extent of the northwest Laurentide Ice Sheet (LIS) in the western Canadian Arctic Archipelago (CAA) during the last glaciation and documents subsequent ice sheet retreat and glacioisostatic adjustments across western Banks Island. New geomorphological mapping and maximum-limiting radiocarbon ages indicate that the northwest LIS inundated western Banks Island after ~ 31 ¹⁴C ka BP and reached a terminal ice margin west of the present coastline. The onset of deglaciation and the age of the marine limit (22–40 m asl) are unresolved. Ice sheet retreat across western Banks Island was characterized by the withdrawal of a thin, cold-based ice margin that reached the central interior of the island by ~ 14 cal ka BP. The elevation of the marine limit is greater than previously recognized and consistent with greater glacioisostatic crustal unloading by a more expansive LIS. These results complement emerging bathymetric observations from the Arctic Ocean, which indicate glacial erosion during the Last Glacial Maximum (LGM) to depths of up to 450 m.     

中国西部末次冰期以来冰川、环境及其变化

晚更新世以来,由于青藏高原及其周围山地的上升,中国西部的气候愈来愈干冷,冰川发育受到抑制。末次冰期最盛时,雪线比今日低300—1500m,古冰缘下限比今日低300—1400m,高山带的气温比今日低3—7℃,高原外围地区低8—10℃。青藏高原从13000aB.P.开始气候变暖,6000aB.P.高温期时冰川强烈退缩或消失,4000—3000aB.P.气候又再次变冷进入全新世新冰期和现代小冰期。目前气候又开始变暖,大部冰川又转入后退时期。     

Multiple glaciations and sea level changes, northern Ellesmere Island, high arctic Canada

Along the northern coasts of Ellesmere Island, at least two glaciations are recognized on the basis of morphostratigraphy. The early Holocene ice limit lay only 5 to 60 km beyond present glaciers due to constraints imposed by aridity and calving. This limited ice advance likely extended beyond any Wisconsinan glacial limit. Marine limits established during, retreat from the last glacial maximum reach 148 m a.s.l. In contrast, earlier, more extensive glaciations inundated the coastlines and are associated with former relative sea levels now reaching 286 m a.s.l. Correlation of these pre-Wisconsinan glaciations is based upon amino acid ratios. However, this approach is severely limited by slow rates of racemization, a lack of in situ samples, and complex thermal histories owing to multiple transgressions. Models favoring extensive regional glaciation of northern Ellesmere Island and Greenland must include a glacioclimatic scenario recognizing the constraint that aridity places on glaciation. We suggest that the large ice volume associated with the oldest recognized glaciation relates to a period of reduced sea-ice cover, possibly >400,000 BP, and may correlate with an interglacial stage of the marine oxygen isotope record.     

The Late Devensian and Flandrian history of the Teith valley, Scotland

Two episodes of glaciation are identified in the Teith valley, central Scotland. During the earlier episode, the valley was wholly occupied by an ice sheet, but during the later episode, correlated with the Loch Lomond Readvance, ice only occupied the upper part of the valley. The deglaciation which followed each episode was marked in particular by sequences of kame and outwash terraces. A terrace related to the second episode grades into a large fan buried beneath a sequence of marine deposits in the nearby Forth valley. The latest of these, the carse clays, are related to Flandrian terraces in the Teith valley.     

Late quaternary glacial history of George VI Sound area, West Antarctica

During the last glacial maximum in West Antarctica separate ice caps developed on Alexander Island and on Palmer Land, became confluent in George VI Sound, and discharged northward from latitude 72° S. Radiocarbon (>32,000 yr) and amino acid (approximately 120,000 yr) age determinations on shell fragments (Hiatella solida) found in basal till suggest a Wisconsin age for the glaciation that incorporated them. The pattern of ice flow differed from that deduced for this area in the CLIMAP reconstruction. Following the maximum stage, there was a stadial event when outlet valley glaciers flowed from smaller ice caps into George VI Sound. More widespread recession permitted the George VI ice shelf to deposit Palmer Land erratics on eastern Alexander Island before isostatic recovery raised them to final elevations of about 82 m. The ice shelf may have been absent at about 6500 yr B.P., when large barnacles (Bathylasma corolliforme) were living in the sound. Small glaciers readvanced to form at least two terminal moraines before the ice shelf re-formed and incorporated the barnacle shells into its moraine on Alexander Island. The shells gave a ¹⁴C age (corrected for Antarctic conditions) of about 6500 yr B.P. and an amino acid ratio consistent with a Holocene age. Valley glaciers readvanced over the ice-shelf moraine before oscillations of both valley glaciers and the ice shelf led to the formation of the present sequence of contiguous ice-cored moraines, probably during the Little Ice Age. Such oscillations may represent a climatic control not yet observed in the dry valleys of Victoria Land, the only other part of Antarctica studied in detail for glacier fluctuations.     

Hawaiian glacial ages

Four glacial drifts that are interstratified with lava flows and tephra layers on the upper slopes of Mauna Kea demonstrate that an ice cap formed repeatedly at the summit of the volcano during the middle and late Pleistocene. The oldest drift (Pohakuloa Formation) probably was deposited shortly after eruption of a lava flow having a $\text{K}\text{Ar}$ age of 278,500 ± 68,500 yr. Drift of the Waihu Formation, marked by a belt of subdued end moraines, is correlated with hyaloclastite cones and associated lava flows that were erupted beneath an ice cap about 170,000–175,000 yr ago. One of four younger subglacially erupted lavas at the crest of the volcano has a $\text{K}\text{Ar}$ age of 41,300 ± 8300 yr. Tephra layers that antedate the last glaciation are about 29,700 to 37,200 ¹⁴C yr old and underlie dune sand that is believed to correlate with drift of the Makanaka Formation deposited during the last ice advance. The late Makanaka ice cap, which covered an area of about 70 km² and was as much as 100 m thick, is reconstructed from end moraines and limits of erratic stones that encircle the summit region. The ice cap disappeared from the summit before about 9080 yr ago. Postglacial lavas and tephra overlie the youngest drift on the upper south flank of the mountain and buried a widespread post-Makanaka soil on the lower south rift zone about 4500 ¹⁴C yr ago. The island of Hawaii is subsiding isostatically due to crustal loading by Quaternary volcanic rocks, with subsidence near the midpoint of Mauna Kea estimated as about 2.5 ± 0.5 mm/yr. A curve depicting an inferred long-term subsidence rate has been used to adjust equilibrium-line altitudes (ELAs) of former ice caps that are calculated on the basis of reconstructed glacier topography and an assumed accumulation-area ratio of 0.6 ± 0.05. The results indicate that ELA depression was greatest during Waihu glaciation, least during Pohakuloa glaciation, and that the ELA during late Makanaka glaciation was somewhat lower than that of the early Makanaka advance. Available radiometric dates show that late Makanaka glaciation correlates with stage 2 of the marine oxygen-isotope record, and suggest that early Makanaka, Waihu, and Pohakuloa glaciations correlate, respectively, with isotope stages 4, 6, and 8. Because ice caps could have formed on Mauna Kea only after the snowline was lowered many hundreds of meters below its inferred present level, episodes of Hawaiian glaciation probably were restricted to times of maximum ice volume on the continents. The asymmetry of the late Makanaka ice cap and the southeast-descending gradient of its equilibrium line are consistent with a southeast (tradewinds) source of precipitation during the last glaciation. Although departures of glacial-age temperature and precipitation from present values are difficult to assess quantitatively, growth of former ice caps on Mauna Kea most likely was due to enhanced winter snowfall and to reduced ablation rates brought about by lower air temperature and increased cloudiness.     

Pleistocene raised marine deposits on Wrangel Island, northeast Siberia and implications for the presence of an East Siberian ice sheet

Two previously undocumented Pleistocene marine transgressions on Wrangel Island, northeastern Siberia, question the presence of an East Siberian or Beringian ice sheet during the last glacial maximum (LGM). The Tundrovayan Transgression (459,000–780,000 yr B.P.) is represented by raised marine deposits and landforms 15–41 m asl located up to 18 km inland. The presence of high sea level 64,000–73,000 yr ago (the Krasny Flagian Transgression) is preserved in deposits and landforms 4–7 m asl in the Krasny Flag valley. These deposits and landforms were mapped, dated, and described using amino acid geochronology, radiocarbon, optically stimulated luminescence, electron spin resonance, oxygen isotopes, micropaleontology, paleomagnetism, and grain sizes. The marine deposits are eustatic and not isostatic in origin. All marine deposits on Wrangel Island predate the LGM, indicating that neither Wrangel Island nor the East Siberian or Chukchi Seas experienced extensive glaciation over the last 64,000 yr.     

Revision of the NW Laurentide Ice Sheet: implications for paleoclimate,the northeast extremity of Beringia,and Arctic Ocean sedimentation

For the past half-century, reconstructions of North American ice cover during the Last Glacial Maximum have shown ice-free land distal to the Laurentide Ice Sheet, primarily on Melville and Banks islands in the western Canadian Arctic Archipelago. Both islands reputedly preserve at the surface multiple Laurentide till sheets, together with associated marine and lacustrine deposits, recording as many as three pre-Late Wisconsinan glaciations. The northwest corner of Banks Island was purportedly never glaciated and is trimmed by the oldest and most extensive glaciation (Banks Glaciation) considered to be of Matuyama age (>780 ka BP). Inside the limit of Banks Glaciation, younger till sheets are ascribed to the Thomsen Glaciation (pre-Sangamonian) and the Amundsen Glaciation (Early Wisconsinan Stade). The view that the western Canadian Arctic Archipelago remained largely ice-free during the Late Wisconsinan is reinforced by a recent report of two woolly mammoth fragments collected on Banks and Melville islands, both dated to ～22 ka BP. These dates imply that these islands constitute the northeast extremity of Beringia.A fundamental revision of this model is now warranted based on widespread fieldwork across the adjacent coastlines of Banks and Melville islands, including new dating of glacial and marine landforms and sediments. On Dundas Peninsula, southern Melville Island, AMS ¹⁴C dates on ice-transported marine molluscs within the most extensive Laurentide till yield ages of 25–49 ka BP. These dates require that Late Wisconsinan ice advanced northwestward from Visount Melville Sound, excavating fauna spanning Marine Isotope Stage 3. Laurentide ice that crossed Dundas Peninsula (300 m asl) coalesced with Melville Island ice occupying Liddon Gulf. Coalescent Laurentide and Melville ice continued to advance westward through M'Clure Strait depositing granite erratics at ≥235 m asl that require grounded ice in M'Clure Strait, as do streamlined bedforms on the channel floor. Deglaciation is recorded by widespread meltwater channels that show both the initial separation of Laurentide and Melvile ice, and the successive retreat of Laurentide ice southward across Dundas Peninsula into Viscount Melville Sound. Sedimentation from these channels deposited deltas marking deglacial marine limit. Forty dates on shells collected from associated glaciomarine rhythmites record near-synchronous ice retreat from M'Clure Strait and Dundas Peninsula to north-central Victoria Island ～11.5 ka BP. Along the adjacent coast of Banks Island, deglacial shorelines also record the retreat of Laurentide ice both eastward through M'Clure Strait and southward into the island's interior. The elevation and age (～11.5 ka BP) of deglacial marine limit there is fully compatible with the record of ice retreat on Melville Island. The last retreat of ice from Mercy Bay (northern Banks Island), previously assigned to northward retreat into M'Clure Strait during the Early Wisconsinan, is contradicted by geomorphic evidence for southward retreat into the island's interior during the Late Wisconsinan. This revision of the pattern and age of ice retreat across northern Banks Island results in a significant simplification of the previous Quaternary model. Our observations support the amalgamation of multiple till sheets – previously assigned to at least three pre-Late Wisconsinan glaciations – into the Late Wisconsinan. This revision also removes their formally named marine transgressions and proglacial lakes for which evidence is lacking. Erratics were also widely observed armouring meltwater channels originating on the previously proposed never-glaciated landscape. An extensive Late Wisconsinan Laurentide Ice Sheet across the western Canadian Arctic is compatible with similar evidence for extensive Laurentide ice entering the Richardson Mountains (Yukon) farther south and with the Innuitian Ice Sheet to the north. Widespread Late Wisconsinan ice, in a region previously thought to be too arid to sustain it, has important implications for paleoclimate, ice sheet modelling, Arctic Ocean ice and sediment delivery, and clarifying the northeast limit of Beringia.