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1.
A reconstruction of the palaeohydrological conditions of a flood‐plain: a multi‐proxy study from the Grabia River valley mire,central Poland 
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下载免费PDF全文 Dominik Pawłowski Grzegorz Kowalewski Krystyna Milecka Mateusz Płóciennik Michał Woszczyk Tomasz Zieliński Daniel Okupny Wojciech Włodarski Jacek Forysiak 《Boreas: An International Journal of Quaternary Research》2015,44(3):543-562
This study investigated the Grabia River valley mire in central Poland to reconstruct its palaeoenvironmental conditions from the Younger Dryas to the present. We analysed sedimentological, biological and geochemical data from the palaeo‐oxbow lake and valley mire to identify the principal hydrological trends, especially episodes of high water level. During the Lateglacial and Holocene, the Grabia River had a meandering channel, and its hydraulic parameters and the channel dimensions changed in response to climatic oscillations and vegetation development. We identified phases of high flood intensity and high groundwater level that correlate with regional and supraregional climatic events. The frequency and timing of palaeohydroclimatic oscillations show strong similarities to records from other sites in Poland and the rest of Europe. We show that various analytical methods, namely, pollen, plant macrofossils, Cladocera, Chironomidae, sedimentological, geochemical and radiocarbon data, can be effective tools for reconstructing past hydroclimatic changes in palaeo‐oxbow lakes and investigating the effects of past climate changes on river environments. The high sensitivity of the biota, especially Cladocera, to changes in water level permits the reconstruction of palaeoecological changes, especially flood episodes that occurred in the river valley. In particular, the increase in the proportion of sediment‐associated Cladocera and pelagic taxa was closely correlated with floods. Through comparisons with the palaeobiological data, geochemical data allowed the identification of humid phases within the fen associated with a rising groundwater table, direct fluvial activity (floods) and alluvial deposition. We also discuss the limitations of palaeohydrological reconstructions based on these proxies, especially on fossil aquatic invertebrates. 相似文献
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Dr. M. Bariss 《GeoJournal》1987,15(2):167-172
The stabilization of side-slopes in the small valleys of two major loess regions, the American Midwest and E Transdanubia in Hungary, were studied based upon the field measurements of 224 relatively stabilized slope profiles; for comparison, 97 profiles were also measured in non-loessic areas near the American loess region. Data from the field measurements were then subjected to frequency distribution analyses according to various groupings and the mean values were compared in terms of slope declivity and angularity.The effect of lithology on slope development is demonstrated by the finding that the valley side-slopes in loess are steeper by 6° and more angular by about 7° than those in non-loess. Also, the valleys in loess tend to be more symmetrical than those in non-loess. A comparison of the upper and lower sections of the valleys that were subjected to a double-cycle of erosion into the same sediment within the same region, i.e., into loess in the American Midwest, indicate the effect of time. The lower, which are also younger, sections of these valleys are steeper by 10° and more angular by 9° than their upper ones; thus the model of reclining slope retreat seems to be confirmed here. A moderate effect of exposure on slope development is indicated by the slightly steeper and more angular (by 1° – 2°) slopes exposed to the N-NE-E versus those exposed to the S-SW-W.Because of the complex and interrelated dynamic processes involved in slope evolution there are probably many factors which are responsible for the stabilization of the valley side-slopes of the study areas; some explanations are offered in this paper. It was also found that differences in lithology, time and exposure influence primarily the youngest, which are also the relatively least stable, components of the slope.Most of the results of this research were presented at the XI INQUA Congress in Moscow, USSR, 1982. 相似文献
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重力场数据处理涉及的内容一般有场的延拓、方向导数以及局部场、背景场分离提取等,它们均属于重力异常分离问题的范畴。而重力场视密度三维反演技术是根据重力异常求取和确定场源体视密度的三维分布,其视密度分布图与地层岩性、地质构造以及地下矿体直接关联。对姚家岭地区重力场视密度三维反演技术的应用结果表明,视密度分布图对区内不同岩性地层的分布、褶皱和坳陷构造的分布特征等地质现象取得了良好的应用效果。 相似文献
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The isotopic composition of meteoric water in Sicily, Italy was investigated from May 2004 until June 2006. Samples were sampled monthly from a network of 50 rain gauges. During the same period 580 groundwater samples were collected from springs and wells to obtain insight into the isotopic composition of the water circulating in the main aquifers of the area. The mean weighted precipitation values were used to define the weighted local meteoric water line for five different sectors of Sicily. The use of Geographical Information System tools, coupled with isotopic vertical gradients, allowed designing an isotopic contour map of precipitation in Sicily. The defined meteoric compositions were highly consistent with most of the groundwater samples in each sector. However, in some areas fractionation processes occurring during and after rainfall slightly modify the isotopic composition of the groundwater. The obtained data set defines the present day isotopic composition of meteoric water in the central Mediterranean area and provides baseline values for future climatic and/or isotope-based hydrology studies. 相似文献
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Wuzhen Huiwen Zhang Shiyin Liu Junyin Chen Dachen Tan 《Journal of the Geological Society of India》2018,91(4):457-466
Landslides commonly occurs in hilly areas and causes an enormous loss iof life and property every year. National highway-1D (NH-1D) is the only road link between the two districts (Kargil and Leh) of Ladakh region that connects these districts with Kashmir valley. The landslide failure record of the recent past along this sector of the highway is not available. The present study documents landslide susceptible zones and records occurrence of 60 landslides during the last 4 years showing an increasing trend in the occurrence of landslides over these years in this sector. The landslide susceptibility zonation map has been prepared based on the numerical rating of ten major factors viz. slope morphometry, lithology, structure, relative relief, land cover, landuse, rainfall, hydrological conditions, landslide incidences and Slope Erosion, categorised the area in different zones of instability based on the intensity of susceptibility. The landslide susceptibility map of the area encompassing 73.03 km2 is divided into 150 facets. Out of the total of 150 facets, 85 facets fall in low susceptibility zone covering 43.56 km2 which constitute about 59.65% of the total area under investigation with a record of 5 landslides; 40 facets fall in the moderate susceptibility zone covering 16.94km2 which constitutes about 23.19% of the study area with a record of 20 landslides; and 25 facets fall in the high susceptibility zone covering 12.53 km2 which constitute about 17.15% of the study area with a record of 35 landslides. Most of the facets which fall in HSZ are attributed to slope modification for road widening. 相似文献
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Hugues‐Alexandre Blain César Laplana Paloma Sevilla Juan Luis Arsuaga Enrique Baquedano Alfredo Pérez‐González 《Boreas: An International Journal of Quaternary Research》2014,43(1):107-120
The Cueva del Camino site (Pinilla del Valle, Madrid, Spain) is located in the upper valley of the Lozoya River in the Sierra de Guadarrama, a mountain range extending NE?SW within the Central Range System. Due to its location within a mountain range on the central Iberian Peninsula at an altitude of 1114 m a.s.l. and the numerical dating of its sediments, the palaeontological site of Cueva del Camino has proved a highly relevant location for studying the ecological changes linked to the climatic fluctuations at the end of Marine Isotope Stage (MIS) 5 and the beginning of MIS 4. Environmental reconstructions suggest a rather open, patchy landscape throughout the succession, with abundant evidence of dry meadows, scrublands and rocky habitats. The climate can be considered as generally warm, reaching mean annual temperatures (MATs) of up to 13.8°C (i.e. higher than today's by up to 2.9°C). Three cooler events can be seen throughout the succession as reflected by the presence of Rana iberica, Anguis fragilis and Coronella austriaca. The first of these events may correlate with MIS 5b; the second in the Central sector may correlate with the Stadial I pollen event occurring at the end of MIS 5a; and the third event, corresponding to the coldest MAT of the entire succession with MATs 0.9°C lower than today's, may correspond to the transition from MIS 5a to MIS 4. The evolution of mean annual precipitation (MAP) is characterized by warm periods, drier and cold periods, as well as wetter periods (up to +356 mm compared to today's MAP values), similar to what occurs today in the high‐elevation areas of the neighbouring mountains. Our study gives new quantitative estimations for the climatic fluctuations in mountain environments of central Spain at the MIS 5/4 transition and their associated ecological changes. 相似文献
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Hans Petter Sejrup Berit Oline Hjelstuen Atle Nygård Haflidi Haflidason Ivar Mardal 《Boreas: An International Journal of Quaternary Research》2015,44(1):1-13
Palaeoglaciological reconstructions of the North Sea sector of the last British Ice Sheet have, as other shelf areas, suffered from a lack of dates directly related to ice‐front positions. In the present study new high‐resolution TOPAS seismic data, bathymetric records and sediment core data from the Witch Ground Basin, central North Sea, were compiled. This compilation made it possible to map out three ice‐marginal positions, partly through identification of terminal moraines and partly through location of glacial‐fed debrisflows. The interfingering of the distal parts of the glacial‐fed debrisflows with continuous marine sedimentation enabled the development of a chronology for glacial events based on previously published and some new radiocarbon dates on marine molluscs and foraminifera. From these data it is suggested that after the central Witch Ground Basin was deglaciated at c. 27 cal. ka BP, the eastern part was inundated by glacial ice from the east in the Tampen advance at c. 21 cal. ka BP. Subsequently, the basin was inundated by ice from northeast during the Fladen 1 (c. 17.5 cal. ka BP) and the Fladen 2 (16.2 cal. ka BP) events. It should be emphasized that the Fladen 1 and 2 events, individually, may represent dynamics of relatively small lobes of glacial ice at the margin of the British Ice Sheet and that the climatic significance of these may be questioned. However, the Fladen Events probably correlate in time with the Clogher Head and Killard Point re‐advances previously documented from Ireland and the Bremanger event from off western Norway, suggesting that the British and Fennoscandian ice sheets both had major advances in their northwestern parts, close to the northwestern European seaboard, at this time. 相似文献
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不同于一般的库岸变形,库盘变形、谷幅变形是水库蓄水引起的新的工程地质问题,直接关系到水库大坝的安全运行。监测发现,已建的多座水库在蓄水过程中库盘出现下沉或抬升变形。本文以库盘变形较为典型的溪洛渡、铜街子、江垭、锦屏一级、小湾几个水电站为例,基于水电站所处的地质环境,从水库蓄水引起的区域水文地质条件变化角度分析库盘变形的地质成因条件。研究发现,地形地貌、地层岩性、地质构造和水文地质条件是发生库盘、谷幅变形的内在因素,而水库蓄水位、蓄水过程是诱发库盘、谷幅变形最重要的外在因素,外因通过内因而起作用。研究成果将为在建、待建水电工程建立正确的库盘变形、谷幅变形物理模型,准确计算、分析、预测可能发生的库盘、谷幅变形提供科学依据。 相似文献
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下切谷是陆地上一种常见的侵蚀地貌,古今均十分发育,但是不同盆地、不同时代发育的下切谷,无论是在沉积充填特征还是平面展布形态等多个方面都大相径庭。为此,作者依据曼宁公式进行理论推导,再结合分析北海盆地维京地堑发育的典型下切谷实例以及前人进行的相关水槽实验结果总结认为: 地形坡度、基准面下降速率及幅度与下切谷所侵蚀地层的岩性是影响下切谷发育模式的最主要因素。这些因素共同控制了: (1)下切谷的弯度指数及宽深比,(2)下切谷平面上发育密度及其规模,(3)与下切谷伴生的陆棚三角洲、陆棚边缘三角洲沉积厚度及展布范围。海侵过程中下切谷的沉积充填类型及岩性,受平均基准面上升速率及沉积物供应量的共同控制,根据沉积充填类型及岩性的不同可将其划分为富砂型陆棚三角洲充填及富泥型河口湾充填两类。 相似文献
11.
《Boreas: An International Journal of Quaternary Research》2018,47(1):80-105
Using extensive data sets from three separate areas in the German North Sea sector, consisting of seismic grids, cores and in‐situ cone penetration tests (CPT), we have established a revised stratigraphical framework for the mid to late Quaternary deposits of the German North Sea sector. This framework consists of four regional unconformities and 15 other local unconformities derived from seismic profiles. Using these unconformities, along with lithological and geotechnical data, it was possible to define and correlate 14 major units and 21 subunits within the framework. The Quaternary cover in the area is characterized by a variety of environmental settings ranging from glacial terrestrial and fluvial to lacustrine as well as brackish and marine environments with associated erosion, reworking and deposition. The complexity of Quaternary deposits within the area is explained by its history of repeated ice advances interrupted by marine transgressions and exposed periglacial landscapes. Within the framework, eight buried tunnel valleys and two shallow buried river valleys are identified from seismic profiles with four phases of tunnel valley generation inferred. These phases of tunnel valley generation are associated with the Elsterian (three) and Saalian (one) glacial stages. Infill of these tunnel valleys consists of glaciofluvial sands, thick sequences of marine and lacustrine fine‐grained sediments and some reworked till remnants. Elsewhere, extensive tabular units have formed consisting of marine and fluvial sediments. We compare this new stratigraphy with previous stratigraphies for the German North Sea sector, attribute informal stratigraphical names and offer preliminary correlations with established stratigraphies from other sectors of the North Sea. 相似文献
12.
A. Rosi V. Tofani L. Tanteri C. Tacconi Stefanelli A. Agostini F. Catani N. Casagli 《Landslides》2018,15(1):5-19
In this paper, the updating of the landslide inventory of Tuscany region is presented. To achieve this goal, satellite SAR data processed with persistent scatter interferometry (PSI) technique have been used. The updating leads to a consistent reduction of unclassified landslides and to an increasing of active landslides. After the updating, we explored the characteristics of the new inventory, analysing landslide distribution and geomorphological features. Several maps have been elaborated, as sliding index or landslide density map; we also propose a density-area map to highlight areas with different landslide densities and sizes. A frequency-area analysis has been performed, highlighting a classical negative power-law distribution. We also explored landslide frequency for lithology, soil use and several morphological attributes (elevation, slope gradient, slope curvature), considering both all landslides and classified landslide types (flows, falls and slides). 相似文献
13.
Incised valleys are canyon‐like features that initially form near the highstand shoreline and evolve over geological time as rivers erode into coastal plains and continental shelves to maintain equilibrium‐gradient profiles in response to sea‐level fall. Most of these valleys flood during sea‐level rise to form estuaries. Incised‐valley morphology strongly controls the rate of creation of sediment accommodation, valley‐fill facies architecture and the preservation potential of coastal lithosomes on continental shelves, and affects coastal physical processes. Nonetheless, little is known about what dictates incised‐valley size and shape and whether these metrics can be used to explain principal formation processes. The main control on alluvial channel morphology over human time scales is discharge; this is based on numerous empirical studies and is well‐constrained because all variables are easily measured at this short time scale. Knowledge of long‐term river evolution over a complete glacio‐eustatic cycle, on the contrary, remains largely conceptual, experimental and based on individual systems because variables that are thought to drive morphological change are not easily quantified. In spite of this difficulty, existing models of incised‐valley formation at the coast suggest that valley evolution is driven largely by downstream forcing mechanisms, highlighting sea‐level and shelf gradient/morphology as the dominant controls on valley incision. Although valleys are cut by rivers, whose channels are a direct reflection of discharge, little empirical data exist in coastal areas to address the degree to which valley evolution is governed by upstream controls. The late Quaternary is the best time period to examine because it provides the most complete sedimentary record and many variables, including sea‐level, tectonics, substrate lithology and drainage network characteristics, are accurately constrained. Here, 38 late Quaternary valleys along the coast of two different passive continental margins are compared, which suggests that valley shape and size are governed primarily by upstream, intrinsic controls such as discharge. Valley width, depth and cross‐sectional area are found to be predictable at the highstand shoreline and are scaled with the size of their drainage basin, which has important implications for estimating sediment discharge to continental shelves and deep water environments during periods of low sea‐level. 相似文献
14.
三峡库区滑坡的时空分布特征与成因探讨 总被引：22，自引：7，他引：15
三峡库区地质灾害频繁发生,地质历史上大型滑坡广泛发育。近年库区滑坡灾害有逐年增加趋势。这些滑坡形成的堆积体成因复杂,不能单纯从传统的外动力或内动力作用来解释,给库区灾害的防治工程带来了很大困难。三峡库区大型古滑坡主要沿长江干流和支流的深切河谷两岸分布,与河流发育演化史密切相关。15万年以来,长江三峡地区经历了新构造期以来抬升速率最快的一次构造幕,山原期夷平面上升了100m,河流强烈下切,形成高陡岸坡,卸荷效应显著;同时,该时期三峡地区的气候受到青藏高原环境变化的影响,在间冰期可能存在相似的暖湿古气候环境,降水极为丰富。三峡库区的大型古滑坡在新构造快速抬升时期广泛发育,并且与暖湿多雨期相对应,表明库区滑坡的发育演化是新构造运动和气候变化内外动力耦合作用的结果。 相似文献
15.
A. K. Dwivedi Abhinav Kumar A. K. Chaturvedi 《Journal of the Geological Society of India》2016,88(2):159-172
This research aims at integrating remote sensing data and field studies to prospect for uranium mineralisation in the Palaeoproterozoic Mahakoshal Group of rocks in the Son valley area, Central India. In present work, a revised geological map of Mahakoshal Fold Belt (MFB) bounded by Son-Narmada north fault (SNNF) and Son-Narmada south fault (SNSF) along Chorhut-Sidhi-Chitrangi sector falling in Sidhi, Rewa and Shahdol districts of Madhya Pradesh has been prepared based on interpretation of digitally enhanced satellite images. The satellite image interpretation is supported by limited field works, radioelemental measurements (eU, eTh and % K) of in-situ rocks by four channel Portable Gamma Ray Spectrometer (PGRS) and existing published geological maps of Geological Survey of India. In search for mineral potential areas, accurate and up-to-date geological maps are essential as it represent the most basic information for carrying out further exploration activities. However, available geological maps of MFB and sedimentary formations ofVindhayan Supergroup along SNNF and Chhotanagpur Granite Gneissic Complex (CGGC) and Gondwana Supergroup along SNSF available in public domain are discontinuous and multi-scaled. 相似文献
16.
D. P. Shukla C. S. Dubey A. S. Ningreichon R. P. Singh B. K. Mishra S. K. Singh 《Natural Hazards》2014,71(3):1433-1452
Alaknanda river basin is considered to be tectonically active where damaging earthquakes and landslides have occurred. The whole basin was divided into 8 sub-basins to carry out morphometric analyses, hypsometric integral (HI) analysis and valley floor width to valley height ratio (V f) factor. The sub-basins 2 and 3 show that they are highly active, because of the higher values of bifurcation ratio, stream frequency asymmetric factor, and lower values of form factor, elongation ratio and circulatory ratio. In these areas, HI values are very low indicating that the landscape is highly eroded, deeply dissected and tectonically active. The result obtained from V f was similar which classified both these basins as highly active. Morphometric analysis, HI and V f analyses along with structural map of study area are used to prepare morpho-tectonic map classifying the whole area into very high, high, moderate and low zones of tectonic activity. This map clearly indicates that the areas near MCT II (Munsiari Thrust), MCT III (Ramgarh Thrust) and North Almora Thrust are tectonically very active which fall in sub-basins 2, 3, 4 and parts of 5. Various locations such as Chamoli, Birahi, Pipalkoti, Rudraprayag, etc. are situated in these zones where many earthquakes and landslides occur every year. Moreover, the data plotted for earthquakes and landslides occurrences are consistent with morpho-tectonic map and can be used as a precursor for demarcation of natural hazard vulnerable zones. 相似文献
17.
《地学前缘(英文版)》2020,11(4):1403-1413
The southern regions of Madagascar have the country’s lowest water supply coverage and are highly vulnerable to drought. Access to potable drinking water is a major challenge for the local population. Chronic droughts lead to annual emergency appeals to save the lives of acute malnourished children. UNICEF’s response consisting in providing potable drinking water through the drilling of boreholes has been challenged by the complex hydrogeology, the low yield of boreholes and high-level salinity of water, the lack of reliable groundwater data and the weak capacity of the drilling sector. These constraints result in a high rate of drilling failure. To improve drilling success and provide more potable drinking water to local communities, it is vital to undertake reliable groundwater investigation.UNICEF Madagascar and the European Union delegation in Madagascar collaborated on the use of satellite imagery to improve sector knowledge and access to safe and clean water for local communities in southern Madagascar. The methodology relies on produce thematic layers of groundwater potential areas. Later, these thematic layers were overlaid with ground-based hydrogeological data to map the groundwater potential zones (GWP) and identify the most suitable sites for borehole siting and drilling. Findings of this study are very encouraging, and the integrated approach used has proven its applicability in mapping groundwater potential areas in the eight drought-affected areas of south Madagascar. The groundwater potential zone map is being used by UNICEF and partners to plan water supply projects and identify the best sites for positioning new boreholes and reduce the likelihood of drilling failure. Additionally, the project developed a database of groundwater resources, which will improve knowledge of the regional hydrogeological context and strengthen the capacity of the water sector. Lessons learnt from this study show that an integration of the groundwater potential zone map with demographics and water demand information will help identifying priority areas for detailed studies. Moreover, a capacity building activity is required for knowledge/technology transfer to the Ministry of Energy, Water and Hydrocarbons (MEEH), allowing the possibility of scaling-up this integrated approach to the rest of Madagascar. Finally, strengthening the capacity of the MEEH and refining this approach as suggested above will certainly help in the pursuit to improve equitable access to safe and clean water for households located in the drought-affected areas of southern Madagascar, allowing them to be more resilient to the effects of climate change. 相似文献
18.
The erosional processes depend on various variables such as lithology, topography,drainage system, rock structure and climatic conditions. The quantitative evaluationof some of the above geological and geomorphological parameters is of primaryimportance for the purpose of developing erosion risk maps. These maps can becomeuseful tools for developing appropriate strategies on environmental protection, hazardassessment and regional planning.The island of Sifnos, in Cyclades, was chosen as a case study, where in the final map of the sub-basins of this island, erosion risk distribution is presented. 相似文献
19.
《Applied Geochemistry》2006,21(9):1482-1497
Population statistics for As concentrations in rocks, sediments and ground water differ by geology and land use features in the New England region, USA. Significant sources of As in the surficial environment include both natural weathering of rocks and anthropogenic sources such as arsenical pesticides that were commonly applied to apple, blueberry and potato crops during the first half of the 20th century in the region. The variation of As in bedrock ground water wells has a strong positive correlation with geologic features at the geologic province, lithology group, and bedrock map unit levels. The variation of As in bedrock ground water wells also has a positive correlation with elevated stream sediment and rock As chemistry. Elevated As concentrations in bedrock wells do not correlate with past agricultural areas that used arsenical pesticides on crops. Stream sediments, which integrate both natural and anthropogenic sources, have a strong positive correlation of As concentrations with rock chemistry, geologic provinces and ground water chemistry, and a weaker positive correlation with past agricultural land use. Although correlation is not sufficient to demonstrate cause-and-effect, the statistics favor rock-based As as the dominant regional source of the element in stream sediments and ground water in New England. The distribution of bedrock geology features at the geologic province, lithology group and map unit level closely correlate with areas of elevated As in ground water, stream sediments, and rocks. 相似文献
20.
Hajo Idriss Isam Salih Abdulaziz S. Alaamer M. Y. Abdelgalil Salih Ali Salih Amna M. Hasan Mohammed A. ELtahir Mustafa M. O. Ahamed 《Environmental Earth Sciences》2014,72(2):335-339
This study was conducted primarily to measure and map radon activity concentration in soil gas and to understand the effect of geology and lithology and meteorology on radon concentration. Portable radon meter has been used for the measurement of soil gas radon at 30 different locations around Uro and Korn area in eastern Nuba Mountain South Kordofan State. The results indicate that the activity concentrations of 222Rn in soil gas fall within the range of 20–1,359 Bq/m3 with geometric mean of 102.80 Bq/cm3. The obtained data show that samples around Uro have anomaly of 222Rn concentrations than the sample around Korn. The reason could be attributed to differences in the geological structure, lithology and climate parameters. GIS predicative map has shown that the elevated levels of radon concentration were measured in North study area. Upon comparing the results with global data, it was found that the obtained values are far below the reported range of India, Slovenia, Portugal and Syria. However, the range of 222Rn concentrations in the soil observed in this study is significantly high relative to similar data reported from Libya. The regression analysis has shown that no correlation was noted between radon concentrations, climatic parameters and trace element. 相似文献