Detrital transport of metals by glaciers, an example from the Pinchi Mine, central British Columbia

 Abundant cinnabar (HgS) mineralization is associated with the Pinchi Fault in central British Columbia. Two formerly producing mercury mines have been developed on this fault: Pinchi and Bralorne Takla. The mercury content of till (a sediment type directly deposited by glaciers) in the area of this fault is primarily controlled by the occurrence of cinnabar mineralization in bedrock and the direction of ice flow. Cinnabar-bearing bedrock was eroded by glaciers, transported in the direction of ice flow, and deposited "down-ice" from its source. An example of such a dispersal train is documented for the Pinchi Mine area where mercury ore was transported over a distance of 12 km, as measured in the clay-sized fraction (< 0.002 mm) of till, and could have been transported over 24 km according to heavy mineral concentrates (specific gravity >3.3) of this same sediment. Antimony, chromium, and nickel dispersal trains were also detected in the region. These data indicate that natural glacial processes can result in the "mobilization" of metals in the surficial environment, a factor which has to be considered at mine sites in glaciated terrain, where mine reclamation and remediation measures are now required. Received: 31 October 1996 · Accepted: 27 May 1997     

The geomorphic impact of glaciers as indicated by tors in North Sweden (Aurivaara, 68° N)

Geomorphological investigations carried out on 15 tor-like features located on the Aurivaara plateau (North Sweden, 68° N) provide new insights in the greatly debated age of these landforms. Erratics and till trapped deep in the tor joints support a pre-Weichselian age for tor formation. Moreover, the occurrence of various weathering stages in allochtonous material, the joint width up to 1.5 m (requiring long-term weathering), and the frequent association of tors with pediment-like forms, suggest pre-Quaternary tor formation. The juxtaposition of fresh erratics and in situ old weathering features (mushroom rocks, concentrically weathered well-rounded corestones, and grus) indicates a predominantly cold-based regime for the Scandinavian ice sheet, with erratics carried by the overlying moving ice being repeatedly deposited on tor summits during deglaciation phases. The relationships between tors and ice action indicated for the Aurivaara plateau result in the proposal of a morphodynamical succession of five tor subtypes ranging from the preservation of well-rounded corestones still embedded in grus (suggesting negligible glacial erosion) to the almost complete removal of tor features by ice scouring. A comparison with tors in similar geological and topographical contexts from the unglaciated Dartmoor area allows a tentative evaluation of an average overall glacial erosion of 0–10 m on the northern Sweden plateaus, in sharp contrast with the 190 m overdeepening of the nearby Torneträsk basin. Thus, this case study of Swedish tors provides additional support to the recent interpretations of relict landscapes in previously glaciated areas and is in accordance with the classical «model» of glacial selective erosion established in the Nordic and Arctic mountains.     

祁连山冰川消融与高空气温变化的关系

利用1986年6-9月冰川实地考察资料及酒泉站的高空探测资料，分析了1986年6-9月祁连山冰川消融随高空气温的变化特征和高空气温与河西地区托来河流量之间的关系。得出两者之间存在较好的相关关系。     

The post to late glacial valley reconstruction on the Haramosh north side (Mani, Baska and Phuparash valleys)

The post to late glacial valley reconstruction is focused on the Mani- Baska and Phuparash valleys on the Rakaposhi- Haramosh Muztagh in the south Karakoram. The recently glaciated valleys join the Indus valley near Sassi at 1500 m. The knowledge of the tributary valley reconstruction can be seen in the context of the scientific discussion about the extent of glaciation along the main Indus valley. Today, the recent avalanche fed glaciers come down from high lying catchment areas with an average altitude of 6700–6800 m and terminate at 2700 m. Snow line runs at 4700–4800 m in the steep flanks which is common in the Karakoram Mountains. The postglacial extent is marked by the great lateral moraine (GLM) and reached down not more than 2.5–5 km away from the recent glaciers with a calculated snow line depression of 300 m in maximum. It can be shown that the valleys were already glaciated during the lastest Late Glacial down to the valley outlet at 1500 m. The snow line was depressed 600–700 m during that period. A high glacial ice filling of the Haramosh valley and glacial erosion of the flat top of the Darchan ridge as an intermediate valley head is strongly probable.     

碧口群内冰川沉积及冰期的划分与对比

碧口群内前人曾怀疑为冰碛岩的一套岩石,已取得了大量冰川证据,肯定了冰川作用的存在。其时代属早震旦世。据沉积特征、层位及上下接触关系等,将其划为长安、南沱两个冰期,南沱冰期又进一步划分为两个亚冰期,并分别与国内外有关地区作了对比。     

大庸市四都坪震旦系南沱组岩石特征及成因探讨

文中提出以砾、砂、泥作三端员成分进行陆源沉积岩结构分类的三角图解方案,并用于四都坪南沱组岩石的划分,将其划分为杂屑岩、角砾岩、杂砂岩、粉砂质泥岩等。杂屑岩在南沱组剖面中占82％,其中的砾石成分复杂,有砂岩、板岩、大理岩、花岗岩等,大砾石表面有冰川擦痕和磨光面。角砾岩中角砾成分单一,无大漂砾,具颗粒支撑,并见夹有塑性变形的含锰灰岩。杂砾岩中发育砂纹层理及冲刷构造。因此,认为南沱组在成因上与冰川活动有关,在冰浅海环境中堆积,同沉积断裂的存在提供斜坡条件,冰川重力及埋藏冰消融等引发重力流,使冰川沉积不时受颗粒流、碎屑流干扰,而在冰期末又遭冰水及海水的改造。     

A rational explanation of cross-profile morphology for glacial valleys and of glacial valley development

The fact that the cross-profile of the glacial valley could be well approximated by parabolas (Y = aX^b, b = 2.0) is explained by the variation principle, assuming that the glacier erosion works towards minimizing thefriction between ice and bedrock. The variation principle proves that the ideal or fully-developed morphology of the glacial valley should be a catenary, the curve which a chain hanging from two fixed points forms. Maclaurin's series expansion of the catenary equation shows that a parabola is a very good approximation of the catenary; hence, the good approximation of the cross-profile by parabolas. Different catenaries are generated by changing the form ratio (depth/rim width) and are then approximated by Y = aX^b by the method of last-squares. The b values obtained become only fractionally larger than 2.0 with invreasing form ratios of up to 1.0, indicating that b values would range, in practice, between 1.0 and about 2.0 Two types of trend in the relationship between b values and the form ratio were obtained from several glaciers. For one type the b value becomes larger with increasing form ratios, and for the other the opposite. The first type is called the Rocky Mountain model after its source of data and represents overdeepening of the glacial valley development. The second type is caalled the Patagonia-Antarctica model, representing a widening, instead of a deepening, process of development. These differences are attributed to the nature of the glaciers which produced these valleys, i.e. alpine glaciers and continental ice sheets.     

New age estimates and climatostratigraphic correlations for the Borrobol and Penifiler Tephras: evidence from Abernethy Forest,Scotland

The emerging tephrostratigraphy of NW Europe spanning the last termination (ca. 15–9 ka) provides the potential for synchronizing marine, ice‐core and terrestrial records, but is currently compromised by stratigraphic complications, geochemical ambiguity and imprecise age estimates for some layers. Here we present new tephrostratigraphic, radiocarbon and chironomid‐based palaeotemperature data from Abernethy Forest, Scotland, that refine the ages and stratigraphic positions of the Borrobol and Penifiler tephras. The Borrobol Tephra (14.14–13.95 cal ka BP) was deposited in a relatively warm period equated with Greenland Interstadial sub‐stage GI‐1e. The younger Penifiler Tephra (14.09–13.65 cal ka BP) is closely associated with a cold oscillation equated with GI‐1d. We also present evidence for a previously undescribed tephra layer that has a major‐element chemical signature identical to the Vedde Ash. It is associated with the warming trend at the end of the Younger Dryas, and dates between 11.79 and 11.20 cal ka BP. Copyright © 2011 John Wiley & Sons, Ltd.     

Evaluation of a numerical model of the British–Irish ice sheet using relative sea‐level data: implications for the interpretation of trimline observations

The glacial isostatic adjustment (GIA) of the British Isles is complex due to the interplay between local and non‐local signals. A number of recent studies have modelled the GIA response of the British Isles using relative sea‐level data. This study extends these previous analyses by using output from a numerical glaciological model as input to a GIA model. This is a necessary step towards more realistic GIA models, and although there have been similar studies for the major late Pleistocene ice sheets, this is the first study to do so for the British Isles. We test three reconstructions, classed as ‘minimal’, ‘median’ and ‘maximal’ in terms of their volume at maximum extent, and find it is possible to obtain good data–model fits. The minimal reconstruction is clearly preferred by the sea‐level data. The ice reconstructions tested were not constrained by geomorphological information of past ice extent (lateral and vertical). As a consequence, the reconstructions extend further than much of this information suggests, particularly in terms of ice thickness. It is notable, however, that the reconstructions produce good fits to many sea‐level data from central, mountainous regions (e.g. Scottish highlands), which lends support to the suggestion that trimlines, often used as an constraint on the palaeo ice surface location, are in fact features formed at the transition from warm‐ to cold‐based ice and so mark a minimum constraint on the ice surface altitude. Based on data–model misfits, suggestions are made for improving the ice model reconstructions. However, in many locations, the cause of the misfit could be due to non‐local, predominantly Fennoscandian ice and so interpretation is not straightforward. As a result, we suggest that future analyses of this type consider models and observations for both Fennoscandia and the British Isles. Copyright © 2012 John Wiley & Sons, Ltd.