THE EASTERN MARGIN OF GLACIATION IN THE BRITISH ISLES DURING THE YOUNGER DRYAS: THE BIZZLE CIRQUE, SOUTHERN SCOTLAND

ABSTRACT. Geomorphological and sedimentological evidence of former glaciation in the Bizzle valley in the Cheviot Hills of northern England and southern Scotland was used to reconstruct the dimensions of a small topographically constrained glacier with an equilibrium line altitude (ELA) of 535 m. This was interpreted as having formed during Younger Dryas cooling; this is the only glacier to have been described from the area and is the most easterly site of Younger Dryas glaciation in the British Isles. Whilst glaciation at this time was extensive in the Lake District to the southwest, the restricted nature of Cheviot ice cover suggests that a steep west–east precipitation gradient existed in this region during the Younger Dryas.     

In situ cosmogenic 10Be dating of the Quaternary glaciations in the southern Shaluli Mountain on the Southeastern Tibetan Plateau

It is generally considered that four-times ice age happened during the Quaternary epoch on the Tibetan Plateau. However, the research on the chronology of the four-times ice age is far from enough. The Shaluli Mountain on the Southeastern Tibetan Plateau is an ideal place for plaeo-glacier study, because there are abundant Quaternary glacial remains there. This paper discusses the ages of the Quaternary glaciations, based on the exposure dating of roche moutonnée, moraines and glacial erosion surfaces using in situ cosmogenic isotopes ¹⁰Be. It is found that the exposure age of the roche moutonnée at Tuershan is 15 ka, corresponding to Stage 2 of the deep-sea oxygen isotope, suggesting that the roche moutonnée at Tuershan is formed in the last glacial maximum. The exposure age of glacial erosion surface at Laolinkou is 130–160 ka, corresponding to Stage 6 of the deep-sea oxygen isotope. The oldest end moraine at Kuzhaori may form at 421–766 kaBP, corresponding to Stages 12–18 of the deep-sea oxygen isotope. In accordance with the climate characteristic of stages 12, 14, 16 and 18 reflected by the deep-sea oxygen isotope, polar ice cores and loess sequence, the oldest end moraine at Kuzhaori may form at stage 12 or stage 16, the latter is more possible.     

第四纪中期青藏高原冰冻圈的演化及其与全球变化的联系

文章给出了冰冻圈的含义与组成,新生代４２Ｍａ前南极冰盖出现至中更新世,是地球上冰冰圈发展的漫长过程,青藏高原在早更新世只在个别高峰有冰川作用,直到１．１～０．６ＭａＢＰ的昆（仑）黄（河）运动,将高原面抬升至３５００ｍ左右高度的降温作用和同时期地球接受日射的轨道转型＊（由４．１万年周期的轨道倾斜率过渡为１０万年周期的轨道偏心率控制）及相伴的降温作用相耦合。形成了测年数据在０．６～０．８ＭａＢＰ间的倒     

北美东部威斯康星中、晚期古环境与气候变化的甲虫化石证据

北美Laurentide冰盖于末次冰期的大部分时间在北美东北部一直存在，冰盖的活动对北美东部冰期时的环境和气候有很大的影响。甲虫分析表明，北美东部中纬度地区在威斯康星中、晚期的气候以寒冷为主，中间分别在42000aB.P.,34000aB.P.和28000aB.P.出现3次明显的气候变暖。此区威斯康星中期气候冷暖波动的幅度和出现的时间可以与同期的格陵兰冰芯记录及北大西洋Heinrich事件对比。     

对青藏大冰盖目前存在的一些“凝问”,“质凝”及“误解”的答复

西伯利亚含盐地位于西伯利亚地台。含钾盐系属下寒武统安加拉组，岩盐层总厚６００余米，钾盐层厚７０－１５０ｍ，共有钾石盐岩和钾石盐－光卤石岩６层。钾石盐层中ＫＣｌ含量达３５％－４５％，ＭｇＣｌ２和水下溶物含量均小于１％，含盐盆地四周以堡礁带和陆岛与广海相隔，含钾坳陷处于地台上坳陷最深部位。     

庐山东南麓冰川作用表皮构造特征及其意义

庐山东南麓第六阶地基座上,发现了早更新世冰川作用表皮构造。按其形态与成因可分为巨砾压入基岩、小型倒转构造与不协调褶皱、逆冲-贯入构造、大型片麻岩包裹体等四种类型。早更新世初期之庐山,确实多次发生过山麓冰川作用。     

Dating fluvial terraces by Th/U on pedogenic carbonate, Wind River Basin, Wyoming

Reliable and precise ages of Quaternary pedogenic carbonate can be obtained with ²³⁰Th/U dating by thermal ionization mass spectrometry applied to carefully selected milligram-size samples. Datable carbonate can form within a few thousand years of surface stabilization allowing ages of Quaternary deposits and surfaces to be closely estimated. Pedogenic carbonate clast-rinds from gravels of glacio-fluvial terraces in the Wind River Basin have median concentrations of 14 ppm U and 0.07 ppm ²³²Th, with median (²³⁰Th/²³²Th) = 270, making them well suited for ²³⁰Th/U dating. Horizons as thin as 0.5 mm were sampled from polished slabs to reduce averaging of long (≥10⁵ yr), and sometimes visibly discontinuous, depositional histories. Dense, translucent samples with finite ²³⁰Th/U ages preserve within-rind stratigraphic order in all cases. Ages for terraces WR4 (167,000 ± 6,400 yr) and WR2 (55,000 ± 8600 yr) indicate a mean incision rate of 0.26 ± 0.05 m per thousand years for the Wind River over the past glacial cycle, slower than inferred from cosmogenic-nuclide dating. Terrace WR3, which formed penecontemporaneously with the final maximum glacial advance of the penultimate Rocky Mountain (Bull Lake) glaciation, has an age of 150,000 ± 8300 yr indicating that it is broadly synchronous with the penultimate global ice volume maximum.     

Glacial influence on Neoproterozoic sedimentation: the Smalfjord Formation, northern Norway

ABSTRACT There is much debate regarding the intensity and geographic extent of glaciation during the Neoproterozoic, particularly in response to recent geochemical work suggesting that the Neoproterozoic earth was at times ice covered from equator to poles (the ‘Snowball Earth’ hypothesis). A detailed sedimentological analysis of the Neoproterozoic Smalfjord Formation of northern Norway was conducted in order to determine the extent and intensity of glacial influence on sedimentation. In the Tarmfjorden area, the Smalfjord Formation consists of a stacked succession of diamictites interbedded with fine‐grained laminated mudstones containing rare outsized clasts. Diamictites and interbedded mudstones are interpreted as the product of subaqueous mass flows generated along the basin margin. In the Varangerfjorden area, chaotically interbedded diamictites, conglomerates and sandstones are overlain by a thick succession of stacked sandstone beds; onediamictite unit at Bigganjargga overlies a striated pavement. The Varangerfjorden outcrops appear to record deposition on a subaqueous debris apron. Although diamictites contain rare striated and faceted clasts, suggesting a glacial sediment source, their origin as subaqueous mass flows prevents the interpretation of ice mass form or distribution. Rare lonestones may be associated with floating ice in the basin, which may be of glacial or seasonal origin. Glacial ice may have contributed poorly sorted glacial debris to the basin margin, either directly or through fluvioglacial systems, but there is no evidence of direct deposition by ice at Varangerfjorden or Tarmfjorden. The overall fining‐upward trend identified in the Smalfjord Formation and overlying Nyborg Formation is consistent with depositional models of rift basin settings. This fining‐upward trend, the predominance of mass flow facies including breccias associated with scarps and the evidence for extensional tectonic activity in the region suggest that tectonic activity may have played an important role in the development of this Neoproterozoic succession. The Smalfjord Formation at Tarmfjorden and Varangerfjorden does not exhibit sedimentological characteristics consistent with severe glacial conditions suggested by the snowball Earth hypothesis.     

Glacial erosion and geomorphology in the northwest Sierra Nevada, CA

Pleistocene glacial erosion left a strong topographic imprint in the northwestern Sierra Nevada at many scales, yet the specific landforms and the processes that created them have not been previously documented in the region. In contrast, glaciation in the southern and central Sierra was extensively studied and by the end of the 19th century was among the best understood examples of alpine glaciation outside of the European Alps. This study describes glacially eroded features in the northwest Sierra and presents inferred linkages between erosional forms and Pleistocene glacial processes. Many relationships corroborate theoretical geomorphic principles. These include the occurrence of whalebacks in deep ice positions, roches moutonnées under thin ice, and occurrence of P-forms in low topographic positions where high subglacial meltwater pressures were likely. Some of the landforms described here have not previously been noted in the Sierra, including a large crag and tail eroded by shallow ice and erosional benches high on valley walls thought to be cut by ice-marginal channels.     

An approach to modelling the impact of snow drift on glaciation in the Cairngorm Mountains,Scotland

This paper uses a Geographical Information System (GIS) to develop a rule-based model of the effect of snow drifting on glacier growth in the Cairngorm Mountains, Scotland during the Younger Dryas interval. We develop a qualitative model of snow drift that uses a number of simple heuristics to generate a map of relative accumulation at a 50-m resolution over the massif. Relative susceptibility to snow drifting is then compared for a number of different zones under varying wind directions. We conclude that, under the conditions tested in our model, glaciation of the Cairngorms during the Younger Dryas was confined to the high corries and that the pattern of snow drifting suggested by our model points to dominant southerly winds. Copyright © 1999 John Wiley & Sons, Ltd.