Holocene alluvial environments at Barking,Lower Thames Valley (London,UK)     

C.P. Green  C.R. Batchelor  P.J. Austin  A.D. Brown  N.G. Cameron  D.S. Young 《Proceedings of the Geologists' Association. Geologists' Association》2014

Deposit modelling based on archived borehole logs supplemented by a small number of dedicated boreholes is used to reconstruct the main boundary surfaces and the thickness of the main sediment units within the succession of Holocene alluvial deposits underlying the floodplain in the Barking Reach of the Lower Thames Valley. The basis of the modelling exercise is discussed and the models are used to assess the significance of floodplain relief in determining patterns of sedimentation. This evidence is combined with the results of biostratigraphical and geochronological investigations to reconstruct the environmental conditions associated with each successive stage of floodplain aggradation. The two main factors affecting the history and spatial pattern of Holocene sedimentation are shown to be the regional behaviour of relative sea level and the pattern of relief on the surface of the sub-alluvial, Late Devensian Shepperton Gravel. As is generally the case in the Lower Thames Valley, three main stratigraphic units are recognised, the Lower Alluvium, a peat bed broadly equivalent to the Tilbury III peat of Devoy (1979) and an Upper Alluvium. There is no evidence to suggest that the floodplain was substantially re-shaped by erosion during the Holocene. Instead, the relief inherited from the Shepperton Gravel surface was gradually buried either by the accumulation of peat or by deposition of fine-grained sediment from suspension in standing or slow-moving water. The palaeoenvironmental record from Barking confirms important details of the Holocene record observed elsewhere in the Lower Thames Valley, including the presence of Taxus in the valley-floor fen carr woodland between about 5000 and 4000 cal BP, and the subsequent growth of Ulmus on the peat surface.  相似文献   

Climate change mitigation on tropical peatlands: A triple burden for smallholder farmers in Indonesia     

《Global Environmental Change》2021

The agricultural use and conversion of tropical peatlands is considered a major source of land-based greenhouse gas emissions. Thus, the protection and restoration of tropical peatlands has recently turned into an important strategy to mitigate global climate change. Little research exists that has investigated the impacts and dynamics that such climate mitigation efforts evoke in local communities living in and around peatlands. We present insights on this from Sumatra, Indonesia and use a climate justice lens to evaluate local outcomes. We show how an increasingly transnational network of state and non-state actors has become involved in developing new laws, policy programs and land-use agreements on Sumatra’s coastal peatlands, aiming at supposedly win–win low-carbon development pathways. We argue that such efforts are open to much of the same criticism that has been raised regarding previous policies and projects aimed at reducing GHGE from deforestation and forest degradation. These projects disregard local perspectives on development, fail to deliver the promised benefits and, through a reconfiguration of local land-use rights, reduce the capabilities of smallholder farmers to benefit from their land. In sum, our analysis suggests that recent policies and projects aimed at mitigating GHGE from tropical peatlands contribute to a redistribution of the global climate mitigation burden onto smallholder farmers in Indonesia. This occurs through their threefold assignment to protect forests, prevent fires and help restore degraded peatlands.  相似文献   

贵州雷公坪山地沼泽泥炭年代学和沉积速率研究     

张辉  李松  司云云  刘蕊  罗璇  何严华 《贵州地质》2021,38(4):382-386

通过对贵州东南部雷公坪泥炭进行年代学和有机碳同位素测定,雷公坪泥炭剖面底部150 cm处年龄为13 360±40 a BP,在中部70 cm处年龄为4 570±30 a BP,顶部10 cm处年龄为420±30 a BP,建立了雷公坪泥炭沉积的年代学序列,计算出泥炭层堆积速率由上至下分别为2381 cm·ka-1、1446 cm·ka-1、910 cm·ka-1。获得泥炭层泥炭有机碳同位素δ13C分别为-275‰、-288‰、-285‰,结合其他区域气候记录推断,说明研究区泥炭发育于相对温暖湿润的气候环境。  相似文献   

Bridging the gap between ancient metal pollution and contemporary biogeochemistry     

Richard Bindler  Ingemar Renberg  Jonatan Klaminder 《Journal of Paleolimnology》2008,40(3):755-770

Paleolimnology provides long-term data that are often essential for understanding the current state of the environment. Even though there is great potential, paleolimnology is rarely used together with process-related studies to solve issues regarding cycling of elements in the environment. Clearly, this is a drawback because the cycling of many elements, which cause great concern in the present-day environment, was altered long before the advent of monitoring programs. The pioneering work of C.C. Patterson and his colleagues emphasized the importance of a long-term perspective for understanding the current cycling of metals, with a focus on lead, and in particular for estimating background concentrations and human-related impacts in the environment. In Sweden the first traces of atmospheric lead pollution are found in lake sediments dated to about 3500 years ago. The long-term changes in the pollution lead record in lake sediments led us to consider how lead biogeochemistry has changed over time in response to this historical deposition—where has this lead gone, and how much does this lead contribute to the present-day biogeochemical cycling of lead? How was lead distributed in ‘pre-industrial’ soils or more properly in natural soils not impacted by atmospheric pollution? There are many studies that have examined the effects of increased metal concentrations on soil biota, but what are the appropriate background conditions for comparison? Using lake sediments as our foundation we have analyzed lead, including its stable isotopes, in other environmental compartments, including peat, soil, and a range of boreal forest plant species, to develop a better understanding of the fate of lead derived from long-term pollution. Three important conclusions from our studies in Sweden are: (1) atmospheric lead deposition rates during the 20th century were 100 to as much as 1000 times higher than natural deposition rates a few thousand years ago. Even with stricter emission standards during the past three decades and the resultant reductions in deposition, lead deposition rates today are still 10–100 times greater than natural rates. This increase in deposition rates modeled from sediment and peat records is of a similar scale to estimated changes in body burdens of lead in modern versus ancient humans. (2) In Europe about half of the cumulative burden of atmospherically deposited lead was deposited before industrialization. In southern Sweden the cumulative burden of pollution lead during the past 3500 years is 2–5 g Pb m^?2 and in the ‘pristine’ northern parts of the country there is about 1 g Pb m^?2. (3) Predicted recovery rates for soils are slow; in the cold climate of Scandinavia, we find that the soil surface (O horizon), where most soil biota reside, retains lead deposited over the past 150–500 years. Therefore, although lead deposition rates in Europe, as well as N. America, are only 10% of those a few decades ago, it will take several decades or longer for lead concentrations in soils to respond appreciably. The slow turnover rates for lead in the environment and gradual immobilization of lead in deeper soil mineral horizons also inhibits a loss of lead to surface waters in areas removed from point sources.  相似文献   

Determining the number of manual measurements required to improve peat thickness estimations by ground penetrating radar     

E. Rosa  M. Larocque  S. Pellerin  S. Gagné  B. Fournier 《地球表面变化过程与地形》2009,34(3):377-383

Ground penetrating radar (GPR) is often used for investigating peat thickness. The quality of GPR measurements depends on electromagnetic wave (EMW) velocity estimates. The objective of this study is to determine the number of manual measurements required to minimize EMW velocity error in peatlands. A total of 175 manually measured peat thicknesses are used with a depth‐to‐target method to assess EMW velocity in two southern Quebec peatlands. Mean measured EMW velocities are 0·040 and 0·039 m ns^–1 with standard deviations of 0·013 and 0·008 m ns^–1. Statistical analyses show that at least 30 calibration points are required to minimize the EMW velocity error, regardless of the geological setting. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Analytical solution for enhanced recharge around a bedrock exposure caused by deep-aquifer dewatering through a variable thickness aquitard     

《Advances in water resources》2014

In this study an analytical solution was developed to predict steady radially-symmetric percolation rates from an aquifer underlain by a variable thickness aquitard. The solutions consider an aquitard with constant thickness and with radial-symmetrically increasing thickness outward from the center. The solution was used to predict the percolation rate from a peat layer around a bedrock outcrop in the James Bay Lowland near the De Beers Victor diamond mine. In this case the marine sediment layer limited the direct connection between the peat layer and the bedrock as an aquitard. Our zero order solution with constant marine sediment thickness showed the best fit to the steady state water level data of June 2012. It was found that the enhanced recharge around bioherms (i.e., at rates greater than the regional average of 0.7 mm/day) will only occur in marine sediments less than 4.3 m thick, for extreme depressurization of 30 m.  相似文献   

Surface settlements at a soft soil site due to bedrock dewatering   总被引：1，自引：0，他引：1  

Debasis Roy  Keith E. Robinson   《Engineering Geology》2009,107(3-4):109-117

Construction of a 16-m deep, 55-m wide, almost square, underground structure through 8-m of soft soils and 8-m of sandstone and siltstone led to the development of widespread settlements. The affected area extended to distances of over 200 m from the perimeter of the structure. The floor slab of the underground structure was not designed for water pressure. Thus, operation of the structure requires continuous pumping of seepage water collected at a sump located at the lowermost elevation within the structure. Subsurface investigation and monitoring data obtained over 5.75-year period following the construction of the structure indicated that the settlement resulted from consolidation of soft soils due to depressurization of an aquifer within the underlying bedrock caused by continuous dewatering needed for the operation of the structure. An analytical study was undertaken to project the long term settlement. A simple analytical model could be used to simulate the complex hydrogeological problem reasonably. The details of hydrogeologic setting, subsurface investigation and monitoring activities, and the analytical model for projecting long-term settlements are presented in this paper.  相似文献   

The use of large bottomless lysimeters in the determination of water balances for a raised mire     

Julia C. Kelemen  Hugh A. P. Ingram 《水文研究》1999,13(1):101-111

  相似文献   

煤沉积学研究现状与动态   总被引：8，自引：0，他引：8  

刘光华 《地学前缘》1999,6(Z1):101-110

统计资料表明,自80年代末以来各国发表的有关煤炭地质研究的论文呈明显的下降趋势,这反映了当前国际煤炭工业的不景气。但是在过去的10年内,含煤沉积研究的进展和发展也很瞩目。对现代泥炭沼泽的大量调查结果使人们对成煤沼泽类型与成因及其各种控制因素之间的关系有了进一步的了解。沉积相分析中加强了对煤层本身的研究,冲破了以往只侧重于其顶、底板岩性分析的局限性;煤岩学的理论与方法已扩大到了石油、天然气和沉积物中分散有机质等研究领域,并取得了一系列进展。煤层甲烷气勘探和工业性开发的成功,扩大了煤炭地质学范畴。层序地层学原理和方法已广泛地应用到了煤盆地分析和全球煤炭资源评价。但在有些方面不能简单地采用层序地层学方法,因为煤系往往是以非海相沉积为主的。  相似文献   

Lake–mire ecosystem transformation and its possible forcing mechanisms in volcanic landform regions: a case study in the Gushantun peatland of northeast China     

Mingming Zhang  Zhaojun Bu  Shasha Liu  Jie Chen  Yaxin Cui  Xu Chen 《地球表面变化过程与地形》2020,45(13):3141-3154

Large numbers of peatlands were developed in volcanic landform regions, which would provide valuable long-term records of lake–mire ecosystem shifts and act as significant carbon pool in regional carbon cycle. To investigate lake–mire ecosystem transformations and driving mechanisms in volcanic landform regions, the developmental history of Gushantun peatland in northeast China was reconstructed in this study. Results indicate that Gushantun peatland initiated in the deepest portions of the basin, and subsequently experienced expansions outward. Peat initiated from approximately 12 ka cal. bp to present. The developmental patterns of Gushantun peatland can be divided into four stages: the stable stage 1 (12–10 ka cal. bp ), maximum stage (10–7 ka cal. bp ), stable stage 2 (7–4 ka cal. bp ) and stable stage 3 (4–0 ka cal. bp ). The possible forcing mechanisms for the development of Gushantun peatland were different during different periods. From 12 ka cal. bp to 10 ka cal. bp , autogenic process was probably the major controlling factor for the expansion of this peatland. From 10 to 7 ka cal. bp , flat basin morphology was the major influence factor for fast expansion. However, the development of Gushantun peatland was probably controlled by the dual effects of high moisture and autogenic process during the period of 7 to 4 ka cal. bp . From 4 ka cal. bp to present, steep basin morphology was the major influence factor, while moisture might be the secondary factor for development of Gushantun peatland. These features indicate that lake–mire ecosystem transforms in volcanic landform regions of Changbai Mountains were probably triggered by the complex effects of autogenic process, hydroclimate and underlying basin morphology. © 2020 John Wiley & Sons, Ltd.  相似文献