Lake District hillslopes

The Lake District is a region of great scenic beauty in north‐west England that has inspired artists and poets alike, and which comes high on the list of classic geological localities in Great Britain in terms of both bedrock and geomorphological features. With its inspiring views, the Lake District is often portrayed as the product of repeated glaciation, mainly because of the clarity of the erosional and depositional features that can be seen there. But since the last glaciers disappeared other processes have been modifying the landscape, processes that have superimposed their own signatures on to the glacial features. Hillslopes in particular have undergone significant changes, as a result of slope failures in both bedrock and superficial sediments. Although these landforms are not unknown, they have not received the same level of investigation as the glacial features, resulting in a limited appreciation of their spatial distribution and significance in reshaping the landscape. This article outlines the characteristics and origins of some slope failure types, and demonstrates that there is still much to learn about the Lake District landscape.     

Lipid Biomarkers of Bottom Sediments in Gusinoe Lake (Lake Baikal Basin) as Indicators for Lake Sedimentogenesis Paleoreconstruction

Doklady Earth Sciences - Small lakes, being less stable systems as compared to large lakes, are sensitive to climate variations and are characterized by high sedimentation rates, and thus, they...     

Comparative analysis of Lake Urmia and Lake Van water level time series

Recent decline in Lake Urmia water level makes it crucial to consider this issue more seriously. For this purpose, comparison of water level in Lake Urmia with Lake Van in Turkey, which is in relatively similar geographic and climate conditions, can be an effective approach. To follow this objective, trend analysis, regime shift, and coherency analyses are implemented. The results showed negative trend in Lake Urmia water level for the past 20 years, while in Lake Van, the trend is positive. Moreover, correlation of the lake level variations versus the basin rainfall during three common periods, identified by the regime shifts analysis, illustrated a decreasing trend in the correlation. These changes can be attributed to non-climatic factors such as different allocation disciplines in two lake’s catchments. Finally, the coherency analysis showed significant annual and inter-annual frequencies common between the two lake levels. Herein, the short-term period relations are associated with lags, while in long term, they act simultaneously.     

Rejuvenation of Lake Erie

The positive ecological changes that have occurred in Lake Erie since the mid-1970, demonstrate that an extensively degraded aquatic ecosystem can be rejuventated. This rejuvenation should provide encouragement to other who are attempting to save such habitats as the Aral Sea. This paper summarizes the problems of Lake Erie, the meassures instituted to correct the problems and the result of remediation efforts.     

湖泊三角洲研究的回顾与展望

本文以中国陆相含油气盆地为例,简要地回顾了湖泊三角洲的研究史、研究现状和存在的主要问题。认为高分辨率层序地层学理论在湖泊三角洲不同级次的等时成因地层单元划分对比中的应用,可将单井的一维信息转化为油田范围至盆地范围的三维信息,从而为储层预测和油气藏精细描述提供更可靠的依据,为油气勘探带来广阔的前景。     

Upwellings in Lake Baikal

Based on shipboard and satellite observations, the characteristics of upwelling in Lake Baikal in the period of direct temperature stratification have been determined for the first time. Coastal upwellings appear annually under the effect of run-down and alongshore winds and are traced along the coast to a distance of up to 60–100 km and up to 250 km in North Baikal. Analogous to the way it occurs in seas, water rises from the depths of 100–200 m (350 m as a maximum) at the velocity of 0.1 × 10⁻²−6.5 × 10⁻² cm/s. Divergence in the field of intràbasin cyclonic macrovortices produces upwelling in the Baikal pelagic zone and downwelling in the vicinity of shores; this lasts from 7 to 88 days and covers the depth interval of 80–300 m in August and up to 400–800 m in early-mid November. The area of upwellings occupies up to 20–60% of the separate basins of the lake. Vertical circulation of water in the field of pelagic upwellings leads to intensification of coastal currents and to formation of the thermobar with a heat inert zone in the central part of the lake in November, and this thermobar is not observed in other lakes, at that.     

Status of glacial Lake Columbia during the last floods from glacial Lake Missoula

The last floods from glacial Lake Missoula, Montana, probably ran into glacial Lake Columbia, in northeastern Washington. In or near Lake Columbia's Sanpoil arm, Lake Missoula floods dating from late in the Fraser glaciation produced normally graded silt beds that become thinner upsection and which alternate with intervals of progressively fewer varves. The highest three interflood intervals each contain only one or two varves, and about 200–400 successive varves conformably overlie the highest flood bed. This sequence suggests that jökulhlaup frequency progressively increased until Lake Missoula ended, and that Lake Columbia outlasted Lake Missoula. The upper Grand Coulee, Lake Columbia's late Fraser-age outlet, contains a section of 13 graded beds, most of them sandy and separated by varves, that may correlate with the highest Missoula-flood beds of the Sanpoil River valley. The upper Grand Coulee also contains probable correlatives of many of the approximately 200–400 succeeding varves, as do nearby parts of the Columbia River valley. This collective evidence casts doubt on a prevailing hypothesis according to which one or more late Fraser-age floods from Lake Missoula descended the Columbia River valley with little or no interference from Lake Columbia's Okanogan-lobe dam.     

High-resolution210Pb dating of Lake Constance sediments: Stable lead in Lake Constance

Two sediment cores (BO90/13b and BO90/17b) from Lake Constance were investigated by-spectrometry for²¹⁰Pb,¹³⁴Cs,¹³⁷Cs,²⁴¹Am,²³⁴Th, and other members of the²³⁸U decay chain. The sediments were dated using the constant-flux model for²¹⁰Pb, and accumulation rates were determined. These range from 0.04 to 0.65g/cm ²/yr (BO90/13b) and 0.04 to 0.8g/cm ²/yr (BO90/17b), respectively. The mean accumulation rate amounts to 0.16g/cm ²/yr for both cores. The cores had already been dated by lamination counting and reconstruction of high-water events at the Limnological Institute at Constance, so that a very precise time scale was available. Both ages derived are in agreement within statistical error up to 1900, which means dating with the constant-flux model for²¹⁰Pb was confirmed up to that age. The position of the maxima of bomb cesium and americium confirm the stratigraphic and²¹⁰Pb datings. With²⁴¹Am a further radioactive isotope is available, which can, due to the half-life of²⁴¹Pu (t _1/2=14.4yr) be detected now by-spectrometry and can serve as an additional time indicator, the maximum being dated at 1963. By applying the various time scales, the depth profiles of stable lead and zinc of core BO90/13b were dated. Both heavy metals show a very significant maximum located beneath the layer of the maxima of bomb cesium and americium, showing that these maxima are older than those of the bomb isotopes. It is remarkable in this context that the maximum of zinc concentration occurs a little later than that of stable lead. Similar concentration profiles are observable in core BO90/17b and other, older sediment cores (CS6-CS10) on a transect across the lake. In contrast to a former assumption, the depth profile of stable lead in Lake Constance sediments does not reflect the anthropogenic gasoline lead emissions into the atmosphere for Germany, their maximum being dated at 1971.     

西藏羊卓雍错湖面遥感监测模型及近期变化

羊卓雍错作为西藏高原三大圣湖之一和藏南重要的高原特色风景旅游景区, 其水域变化受到当地老百姓和各级政府部门的关注. 应用高分辨率陆地资源卫星等遥感数据可以方便、 准确地获取湖泊面积、 周长等信息, 但是由于Landsat 等高分辨率陆地资源卫星影像受到卫星重复周期和卫星过顶时多云天气的影响, 无法实现湖泊面积变化的常规业务化连续监测. 为此, 以Landsat 等高分辨率陆地资源卫星为主要遥感信息源, 结合羊卓雍错水位观测资料, 建立了羊卓雍错湖泊面积变化与水位波动之间的相关模型. 在此基础上, 利用该湖泊面积遥感监测模型, 结合近期水位观测资料分析了羊卓雍错湖面面积变化特征与趋势.     

Baltic Ice Lake in Blekinge

Book reviewed in this article:
A stratigraphic study of Late Weichselian de-glaciation, shore displacement and vegetation history in southeastern Sweden.     

The Kirkland-Larder Lake stratiform carbonatite

The auriferous zone long known as the Larder Lake Break and more recently as the Larder Lake Exhalite is here interpreted as an exhalative kimberlitic carbonatite on the basis of its K, Ba, Sr, Mg, Fe, Cr, Ni and Co contents, and by comparison with similar younger rocks. Gold is believed to have been deposited syngenetically with this stratiform carbonatite and to be genetically related to late Archean tectonic, volcanic, petrochemical, sedimentary and exhalative processes. Rocks of the Timiskaming Series which host the carbonatite appear to represent a post-uplift graben assemblage of sedimentary and alkalic igneous rocks analagous to modern alkalic-carbonatitic complexes located in rifted upwarps. Preliminary data seems to indicate that carbonatite in general has a higher gold abundance than any other rock type, including iron formations and ultramafic rocks. Ferromagnesian carbonatites, the least common variety, may be worthy untested targets for gold exploration programs, particularly if some pyrite or other sulphide mineral is present.     

Lipid geochemistry of Lake Kinneret

Lake Kinneret, a relict lake from the Neogene, is characterised by the dominance among its phytoplankton of the dinoflagellate Peridinium cinctum. The lipid geochemistry of Lake Kinneret is discussed herein in terms of the biology, chemistry and hydrology of the lake. Lipids isolated from two sediment sections (surface and 15 cm deep), obtained from the deepest point of Lake Kinneret, include: (1) 4α-methyl-5α (H)-stanols and related derivatives characteristic of P. cinctum, the novel sterol 4a-methylgorgosterol, and peridinosterol and 4α-methylgorgostanol, not previously reported to occur in lacustrine sediments; (2) C₃₀ and C₃₂ alkane-1,15-diols, not previously reported to occur in contemporary lacustrine deposits, and (3) products of early diagenesis. Many similarities were observed with the more widely studied marine dinoflagellates and marine sediments with dinoflagellate input.     

Hydrodynamics in Holocene Lake Mega-Chad

Holocene Lake Mega-Chad (LMC) was the largest late Quaternary water-body in Africa. The development of this giant paleo-lake is related to a northward shift of the isohyetes interpreted as evidence for an enhanced Monsoon (African Humid Period). Numerous preserved coastal features have been described all around the LMC shore. Such features reveal the main paleo-hydrodynamical tendencies. In the context of a closed water-body like LMC, hydrodynamics are forced mainly by winds. We use a three-dimensional numerical model (SYMPHONIE) to simulate the mean hydrodynamics in LMC under both Harmattan-like (northeasterly trade winds) and Monsoon-like (southwesterly winds) forcings. The northern part of LMC displays coastal features, such as sand spits, that are consistent with the simulations forced by Harmattan-like winds. Geomorphic features related to Monsoon-driven hydrodynamics are not clearly expressed. They could have developed during the early stage of LMC but subsequently reworked. At the time of sand-spit building, Harmattan-like driven hydrodynamics prevailed and related coastal features were preferentially preserved in the sedimentary record.     

西藏扎布耶盐湖卤水演化的Pitzer模型模拟

扎布耶盐湖是西藏高原代表性的富锂硼碳酸盐型盐湖。本文利用Pitzer模型模拟计算了西藏扎布耶盐湖冬季与夏季卤水、补给河流-泉水的低温(2℃)、常温(25℃)和高温(50℃)蒸发结晶过程,结果表明,扎布耶盐湖卤水可以由现代成分的河流-泉水蒸发浓缩形成,扎布耶盐湖的沉积组合与河泉水蒸发浓缩的矿物结晶规律吻合;而冬、夏卤水蒸发模拟结果与卤水蒸发实验结果基本吻合,但对矿物结晶顺序、矿物组合规律以及温度-季节性成分变化的影响等方面,提供了更多更详细的数据与认识。说明Pitzer模型对研究西藏富锂硼碳酸盐型盐湖的地球化学成因和盐田工艺都具有重要参考价值。     

班戈错晚第四纪湖泊发育、湖面变化与藏北高原东南部末次大湖期湖泊演化

班戈错是因湖面阶段性下降而于晚更新世末期从母湖色林错东部分离出来的小离湖.2003年5-7月,我们对班戈湖沿岸进行了详细的地貌与第四纪地质调查,湖面高程及6条剖面湖岸阶地的水准测量,并采集了沿岸及邻区的湖相沉积物样品进行U系年龄测定.研究结果表明,班戈错湖岸阶地共6级,其中T1为与色林错分离后所形成,T2至T6的拔湖高...     

鄱阳湖高水还湖对水位影响的计算与分析

根据高水还湖对湖水位影响的物理机制,建立了以湖泊水量平衡方程为基础,包含高水还湖减少入湖水量、加大湖盆容积、降低湖水位、减小出湖流量等因素的湖水位效应计算模型。计算不同内涝条件下高水还湖的水位效应值,揭示了水位效应与圩区内涝的关系。     

冬季呼伦湖环境科学钻探冰上湖泊钻探平台及取样技术

针对内蒙古呼伦湖的气候特点,为保证工作安全,实施冬季冰上湖泊环境科学钻探,设计研制了冰上湖泊钻探平台系统,满足了工程施工要求。考虑到呼伦湖沉积地层特点,研制了新型活塞式取样钻具和压卡式取样钻具,实践证明,取样效果良好,取心率达到了100%。     

羊卓雍湖流域湖水稳定同位素循环过程研究

基于卓雍错流域2004年降水、河水、湖水中δ¹⁸O的监测结果,结合内陆湖水循环稳定同位素蒸发分馏模型,探讨了青藏高原南部羊卓雍湖水中稳定同位素的变化过程.研究表明:羊卓雍现代湖水中-5.9‰的δ¹⁸O平均值,相对应于当地相对湿度介于54%~58%的气候条件下,这是湖水蒸发分馏作用的最后结果.此外,入湖河水中δ¹⁸O变化也对湖水中平衡δ¹⁸O有一定的影响,而湖水温度的直接影响可以乎略.湖水中δ¹⁸O对入湖水δ¹⁸O的波动的调节能力很强,对于入湖水中δ¹⁸O大的波动,只有不到50 a的时间,湖水中稳定同位素会重新达到平衡.