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1.
A study of detrital zircon age populations in Namurian–Westphalian (Carboniferous) sandstones in the southern Central Pennine Basin of the UK has revealed considerable complexity in their provenance history. The Pendleian–Marsdenian Morridge Formation, which is known to have been derived from the Wales‐Brabant Massif to the south on the basis of palaeocurrent and petrographic information, is dominated by zircons ultimately derived from the Caledonian belt to the north. These zircons were recycled from sandstones of northern origin that had been previously deposited over the massif during Middle to Late Devonian times. The Morridge Formation also includes Late Neoproterozoic zircons of local Wales‐Brabant Massif origin. The south lobe of the Yeadonian Rough Rock has been previously interpreted as having a complex provenance including sediment of northern origin interbedded with sediment ascribed to a Wales‐Brabant Massif source. However, the zircon spectrum lacks a Late Neoproterozoic component that would have been diagnostic of input from the Wales‐Brabant Massif, and the provenance history of the Rough Rock south lobe therefore remains enigmatic. The Langsettian Ludgbridge Conglomerate is dominated by Late Neoproterozoic zircons of Wales‐Brabant Massif origin, but even in this evidently proximal deposit, the provenance is complex since the main zircon group (ca. 640 Ma) cannot be matched with known local Neoproterozoic basement sources. The data either indicate the presence of hitherto‐unknown magmatic rocks of this age adjacent to the South Staffordshire coalfield or indicate that the zircons were recycled from sediment with a more distal origin. Finally, the Duckmantian Top Hard Rock contains zircons that can be reconciled with a source in the Irish Caledonides, consistent with the palaeocurrent evidence, supplemented by zircons derived from the Wales‐Brabant Massif, possibly including the Monian Composite Terrane of Anglesey. The study reinforces the important message that failure to recognize the presence of recycled zircon could lead to erroneous reconstructions of sediment provenance and transport history. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

2.
This paper provides a detailed account of the landslide that took place between 09:00 and 10:00 am on April 25, 2009, near the village of Rampac Grande in northern Peru (department of Ancash). Lives were lost and property destroyed during the event. Archive information, remotely sensed data, and detailed field investigations including sampling were applied to describe the events. Historically, landslides have been a common problem in this region with recorded events dating as far back as the 1800s. The landslide is considered as a deep-seated composite rotational–translational earth slide–earth flow. The local community suspected that a mining company had triggered the landslide as it prospected for precious metals. No evidence was found to suggest that anthropogenic activity caused the landslide. Instead, it was likely caused by the considerable amount of cumulative precipitation during the annual rainy season. Several possible sources of future landslide reactivation have been identified. Finally, a poster has been produced for the local community providing basic information about the event and how to manage the potential future landslide hazard. It is hoped that this simple method of knowledge dissemination will provide a fundamental bridge between the efforts of research scientists and the needs of the local community.  相似文献   

3.
Precisely how Upper Palaeolithic human ecology was shaped by changing climate during the Pleniglacial remains a matter of debate, for while this generally cold period is now understood to include complex and often rapid flux in climate, there are still considerable difficulties in resolving climatic variations at particular times and places — derived from various lines of proxy evidence — with the high-resolution proxy record of temperature changes from oxygen isotope analysis of the Greenland ice-cores.In this paper we apply the methodology of large-scale flotation to newly excavated contexts from the Upper Palaeolithic (Gravettian) site of Dolní V?stonice II, Czech Republic, to explore the potential of charcoal — as a natural archive of environmental information — to offer information on environmental change towards the end of the middle pleniglacial during Oxygen Isotope Stage 3, between c. 32,500 and 31,200 Cal yr BP. The results of an analysis of ring widths and other anatomical features — interpreted alongside micromorphological data — indicate that this charcoal may capture a higher-resolution record of the changing climatic conditions during which humans were first expanding into these hitherto marginal ecologies and, consequently, shed new light upon the complexity of the lifeways that enabled them to do so.  相似文献   

4.
Aluminium was determined in surface and ground waters in the Alba region of NW Italy to provide information on natural and anthropogenic sources of contamination. Determinations were made by a spectrophotometric method based on the aluminium-pyrocatechol complex. The total aluminium content of waters was determined as well as the toxic form of monomeric aluminium, obtained from samples that had been passed through 0.20 μm cellulose filters to remove colloidal and particulate material. Results were correlated with mortality data associated with Alzheimer's disease. There appeared to be a correlation between mortality data and areas having the highest aluminium content of water.  相似文献   

5.
施工期间发生地质灾害常导致何种因素引发的争论。对我国北方某高速公路深路堑边坡开挖到坡顶时发生整体滑坡的案例剖析,发现该边坡是多层云母片岩构成软弱夹层的顺向坡。通过对该区工程地质调查和资料分析,认为构成边坡体的多个软弱夹层及施工期间遭遇强降水是影响该边坡稳定性的主要自然原因。对本区复杂地质条件认识不足,勘察、设计和施工过程中预防、治理对策力度不够也是造成滑坡发生的人为原因。采用层次分析法、多因素关系矩阵法、德尔菲法（专家打分法）等3种方法,计算出了自然和人为6种因素作用因子权重值,给出了基于科学计算的因素作用结果分析和责任权重划分。本文研究结果可望为其他地质条件类似工程因子筛选和责任划分,提供一定参考。  相似文献   

6.
Investigation of biogeochemistry and amino acids on a 30-m-long core from Mansar Lake has thrown light on palaeoclimate variability during the Holocene period. The C/N ratio between 6 and 10 with some deviations and δ13C mostly between −20 and −22‰ in the shallow core, as well as a C/N ratio greater than 13 reaching from 19 to 20 and correspondingly lower δ13C of –28‰ in the deeper core suggest an aquatic source of carbon in the former and a cellulose-rich land plant source in the latter. This is supported by the abrupt increase in organic carbon content in the deeper core compared to the shallow core, which indicates a hot and wet climatic regime during the early Holocene and dry and cold during the late Holocene period. The amino acid data AA-C/C% and AA-N/N% are higher in shallow sediments compared to deeper sediments, indicating an aquatic plant source in the shallow core and greater supply of land plant sources in the deeper core. The lower percentage of the non-protein amino acids β-alanine (ALA) and γ-amino-butyric acid in the shallow core compared to the deeper core indicates different sources of organic matter in the lake basin. The higher amino acid ratio Asp/β-Ala (16.99 av.) and Glu/γ-Aba (18.18 av.) in the shallow core and lower ratios (10.32 and 12.41 av.) in the deeper core, and Asp/Glu (1.52 av.) and β-Ala/γ-Aba (1.61 av.) ratios in the former, which are potential indicators of the nature of the organic matter, are higher in the shallow core relative to the deeper core (1.33 and 1.23 av.), indicating relative biodegradation of organic matter in deeper sediments. It has been observed that the organic matter associated with the dry season is relatively less biodegraded, as evidenced from their higher ratios, and is more biodegraded in the wet season as their ratios are lower in the river sediments. In the absence of a bacterial contribution of organic matter from the soil source in this lake, since Mansar Lake is a non-drainage type, it is envisaged that the climatic variation may be responsible for biodegradation in the deeper core sediments. Therefore, the C/N ratio and δ13C values supported by amino acid data, the latter being significant in revealing primary productivity and a terrestrial source of organic matter, suggest a hot and wet climatic regime during the early Holocene (ca. 7580 bp) and a dry and cold in the late Holocene period (ca. 4050 bp).  相似文献   

7.
Research on land use cover change (LUCC) has reached a mature stage and has formed a relatively complete scientific system. However, most studies analyzed the LUCC process from the view of land use types ignoring the integrality and systematicness of the land use system, which brought certain constraints to understanding the complexity and systematicness of land use process scientifically. Using the Modern Yellow River Delta (MYRD) of China as the study area, this research introduced the complex network analysis method to the study of the LUCC process by using 9 periods of land use data between 1976 and 2014 to build 8 stages of complex networks. The values of node degree, betweenness, changing proportions, and average shortest path in the networks were calculated to identify the key land use types, changing models of land use types, and the stability of land use system. Additionally, main parts of complex networks of the period from 1976 to 1995 and the period from 1995 to 2014 were selected to evaluate the changing characteristics of the LUCC process. The results indicated the area and proportion of natural wetland kept reducing, but the area and proportion of artificial wetland or non-wetland continued rising. The bare land, reed, bush, and cultivated land were the key land use types of the LUCC process. In the past 38 years, beach, bare land, reed and bush had been the output types, and the building land and salt pan had been the input types. The LUCC process has been a transfer process of natural wetland to artificial wetland and non-wetland in the past 38 years, which could be divided into land accretion process (1976 to 1995) and construction process (1995 to 2014). The land ecosystem was unstable for the period from 1990 to 2006.  相似文献   

8.
Recent sedimentary history of natural environmental change and anthropogenic influence in an ephemeral river catchment has been reconstructed using selected major and trace elements, element ratios, and their different geochemical phases (Tessier sequential extraction methods), pollen, and grain size combined with 210Pb- and 137Cs-dating method in marsh sedimentary cores. Attempts were made to use selected element ratios with different geochemical phases—residual phase of Ti, Al, V, Cr, Ni, Rb, K, Sr, and Ba; mobile Sr and Ba—combined with 210Pb- and 137Cs-chronology to interpret certain time information of environmental changes saved within the marsh sediments. Results indicate that there were two marked humid periods during 1850–1860 ad and 1890–1920 ad, and sand storm activities prevailed during 1920–1930 ad. After about 1900 ad, soil erosion has increased with the extensive agricultural activities in the Huolin River catchments, and further intensified after 1950s. After 1980, soil erosion has become even more intense, which is consistent with the reinforcement of human activities, the drastic loss of vegetation cover in the upstream lands, especially, the exploitation of the open cast coalmine in the upstream of Huolin River at that time. Influenced by the inundation of the Huolin River, the heavy metal pollution historical trends in Xianghai marsh wetland could be roughly divided into three periods by analysis of sediment enrichment factor (KSEF) and the index of geoaccumulation (I geo):1760–1880 ad, 1880–1980 ad, and 1980–now. Human activities accelerate the inputs of heavy metal, which leads to degradation of the marsh. This study also investigated on source of marsh sediments (by Ti/Al), redox condition [by V/Cr and V/(V + Ni)], and salinization indicators (by Sr/Ba and Rb/K). The results demonstrate that sources of sediments and redox conditions were partly similar for both riparian and depressional marshes. Besides, some differences in degree of salinization between two types of marsh were also identified, especially after 1880.  相似文献   

9.
Extensive nebkha areas develop mainly under the control of aeolian processes, and their sediments record information on regional environmental changes during different periods. Such areas have developed on the dry riverbeds and deserted arable lands of China’s Alaxa Plateau, Taklimakan, and Kumutage deserts. In this paper, we studied nebkhas that had developed in the Heicheng–Juyan region to determine their CaCO3 contents, particle size distributions, and creation dates. Extensive human activities have occurred in this region since at least in the late Tang Dynasty (618–907 ad). Although historical records show that most of the region’s rivers dried up around 1372, surface water persisted in some areas until the early Qing Dynasty (1644–1911 ad). After the 1600s, extensive nebkhas began to develop due to drying of the region’s rivers. The early stages of nebkha development were controlled by both the sediment supply and the regional wind regime, whereas late stages were controlled primarily by variations in wind activity. In the Alaxa Plateau, it took about 100 years for arable lands and riverbeds to evolve into gobi deserts, and during this time, several phases occurred with different levels of wind activity. The land degradation processes in this region are mainly controlled by surface water resources, and the impact of human activities such as reclamation on land degradation appear to have been overestimated in previous studies.  相似文献   

10.
Land degradation is one of the most common issues in the eastern part of the Nile Delta area that threatens the ongoing agricultural activities and prohibits further reclamation expansions. The different degradation types and the associated risk assessment of some soils types of western Suez Canal region during the period from 1997 to 2010 is discussed. The assessment of the different degradation degrees in the investigated area has been carried out through integrating remote sensing, GIS and GLASOD approaches. Results revealed that the salinization, alkalization, soil compaction and water logging are the main types of land degradation in the area. The main causative factors of human induced land degradation types are; over irrigation, human intervention in natural drainage, improper time use of heavy machinery and the absence of conservation measurements. Low and moderately clay flats, gypsifferous flats, have high to very high risk in both salinization sodication and physical degradation. Values such as EC, ESP, and ground water level reach 104.0 dS/m, 176? % and 60 cm, respectively. These results will be of great help and be basic sources for the planners and decision makers in sustainable planning. The spatial land degradation model was developed based on integration between remote sensing data, geographic information system, soil characteristics and DEM.  相似文献   

11.
Knowledge of the natural background content of metals is important, but can be difficult to establish because the concentrations of substances dissolved in ground waters vary considerably with time and space. The main objective of the paper is to assess the natural background of five selected elements: As, Al, Cd, Pb and Hg. Each of these elements, with the exception of Al, is included in the Minimum list of pollutants and their indicators for which the EU Member States should establish threshold values (Daughter Groundwater Directive). The data of the Czech Hydrometeorological Institute which contains analyses obtained by regular monitoring of the quality of ground waters at intervals of 6 months has been used as the source information. This system incorporates ca. 450 monitoring sites which provide information about water in all the types of rocks penetrated by individual boreholes. Because of the low concentrations of certain elements (Hg, Pb and Cd in particular) a significant number of analytical results lie below the quantification limit of the analytical methods used. Therefore, conventional statistical methods for processing data were not applicable and alternative procedures were used. The Kaplan–Meier procedure was used within the NADA module for statistical analysis of data sets containing values below the quantification limit. The concentrations of monitored elements that can be considered natural background are suggested to be values of the third quartile, i.e. values that are less than or equal to 75% of analytical results in the assessed dataset. The remaining 25% of analytical results that exceed the proposed limit can be considered to be anomalies which may be natural or anthropogenic. Based on the statistical analysis of data specific values for the natural background content of elements in ground waters within particular types of lithology have been proposed. These can be considered the natural background values that apply within the whole of the territory of the Czech Republic.  相似文献   

12.
王治华  徐起德 《现代地质》2008,22(2):281-287
2004-06-22滑坡位于我国西藏自治区的最西端,中印边界附近的帕里河流域中部。以多时相高分辨率卫星图像为信息源,以Orbview立体像对制作的高精度DEM为地理控制,采用数字滑坡技术研究和监测该滑坡自滑坡前至2007年7月的活动。遥感解译表明,滑坡前该处为由弧形裂缝与山体分割的滑前危岩,2004-06-22发生的堵河事件为一高速顺层基岩滑坡,基于RS+GIS求得滑坡体积为63。7万m3。遥感监测显示自2004年9月至2007年7月共35个月内,滑坡边界及滑面各细部均没有明显变化,期间该处未见发生过任何新的滑坡活动。该滑坡是一次在新构造活动强烈的高山峡谷区自然形成的重力侵蚀活动过程,能量释放充分,近期除原滑体四周有一些泄荷及调整活动外不会有大的活动。  相似文献   

13.
During the metamorphism of siliceous carbonates, decomposition of tremolite yields diopside, enstatite, quartz and H2O according to the following reaction: 1 tremolite 2 diopside + 3 enstatite + 1 quartz + 1 H2O.For the application to natural processes, it is of special interest to evaluate the equilibrium temperature of this reaction, as a function of the CO2-content of the H2O-CO2 fluid phase for several total pressures. These values were calculated for the total pressures of 1000 and 2000 bars, usingBoyd's experimentally determined univariant equilibrium data [Fig. 1 (Boyd, 1954 and 1959)]. Curves (a) and (b) of Fig. 3 give the results in a temperature-X CO 2-diagram.The decomposition curves of tremolite intersect the equilibrium curves of other reactions which also take place during metamorphism of siliceous carbonates. If the total pressure can be estimated, these points of intersection together with the appropriate field observations will give information on the temperature and composition of the fluid phase during metamorphism.  相似文献   

14.
白日其利金矿位于青海省北昆仑岩浆弧带南侧，为一典型构造蚀变岩小型金矿。区内构造-岩浆活动强烈而复杂，主要含矿构造既经历了元古代—中生代大规模岩浆上侵导致向南的推覆作用，又经历了新生代青藏高原抬升拉张环境下导致向北的滑脱作用，显示出张扭性和压扭性双重特征。结合地表观察和音频大地电磁测深反演结果，综合分析认为，研究区主要含矿构造(F1)地表产状为NE陡倾，深部为SW陡倾，金矿(化)体极可能位于低阻异常带且构造显示张扭性特征膨大部位，其深部找矿前景较大。  相似文献   

15.
A new approach to the investigation of the Sm/Nd evolution of the upper mantle directly from the data on lherzolite xenoliths is described in this paper.It is demonstrated that the model age TCHUR of an unmetasomatic iherzolite zenolith ca represent the mean depletion age of its mantle source, thus presenting a correlation trend between f^Sm/Nd and the mean depletion age of the upper mantle from the data on xenoliths.This correlation trend can also be derived from the data on river suspended loads as well as from granitoids.Based on the correlation trend mentioned above and mean depletion ages of the upper mantle at various geological times, an evolution curve for the mean f^Sm/Nd value of the upper mantle through geological time has been established.It is suggested that the upwilling of lower mantle material into the upper mantle and the recycling of continental crust material during the Archean were more active ,thus maintaining fairly constantf^Sm/Nd and εNd values during this time period. Similarly ,an evolution curve for the mean f^Sm/Nd value of the continental crust through geological time has also been established from the data of continental crust material.In the light of both evolution curves for the upper mantle and continental crust ,a growth curve for the continental crust has been worked out ,suggesting that :(1)about 30%(in volume )of the present crust was present as the continental crust at 3.8 Ga ago ;(2)the growth rate was much lower during the Archean ;and (3)the Proterozoic is another major period of time during which the continental crust wsa built up .  相似文献   

16.
Studies on Brazilian archaeofauna from prehistoric and historic sites have attempted to explain human settlement and cultural trajectories in different geographical regions. However, only since 1999 have taphonomical criteria been developed during Brazilian zooarchaeological investigations. Wide ecosystem diversity results in the differential preservation of faunal remains. Until the end of the 20th century, many zooarchaeological studies presented insufficient information on complex predator–prey interaction systems in many regions, mostly from the Amazonian lowlands and the highlands of the Central Plateau. Animal remains might have been the result of natural predation, and they are often found mixed within anthropic material that could distort interpretation of deposits. Thus, there are major problems in defining diagnostic criteria to distinguish natural from cultural marks.Taphonomic analyses are needed to explain faunal remains in order to understand the particularities of human–animal relationships in Brazilian prehistory. Zooarchaeological and taphonomical data are presented from five human occupation sites dating from 9000 to 1000 BP to verify human–fauna relationships and natural deposits in three different regions of Brazil. These sites illustrate both natural and anthropic contexts.  相似文献   

17.
Much important information referring to fault motion （e.g., fault activities period, intensity, frequency, and even dynamic background） can be revealed by resolving fault gouge, which is the result of fault motion while extruding or grinding. The field investigation encompassed sample collecting from the Bailong River fault system of the western segment of the Qinling Orogenic Belt （QOB）; 44 samples of fault gouges were collected for quartz micro-morphology analysis. These samples were analyzed using field emission scanning electron microscopy. In addition, 14 samples were tested for thermo-luminescence dating. The results showed that most of the surface textures of quartz grains are characterized by fish scale, moss-like texture, and stalactite. However, a small amount of orange peel-like fractures and worm-hole-like shaped surface texture were observed. Moreover, a few typical conchoids or subconchoidal fractures in quartz grains can be seen. This implies that the Bailong River Fault was active repeatedly during the Quaternary period, but the main motion period is the Pleistocene. The 14 thermo-luminescence dating values showed two age groups： 343.29-184.06 ka and 92.18-13.87 ka. These study data reveal that fault movement started during the Pliocene, occurred frequently in the early-middle period of the Pleistocene, and the peak frequency of the motion was reached in the early Pleistocene. The fault motions were stopped terminated in the early Holocene. The results are significant for the natural disaster risk evaluation in the western segment of the QOB.  相似文献   

18.
Summary Chemical analyses are used by many authors to describe processes of soil development or laterite formation. In this paper some methods of balance calculations are compared by using samples of a laterite profile on granite from India as testing material. It should be proved which of these calculations of transported matter between the different layers are fitting to the mineral analyses of the laterite profile.Only the results of the method proposed byMashall by using an index-mineral as a base for comparison is confirmed by the mineral analyses.The method ofStreng differs from the above described calculation by using a chemical element as an index. FollowingStreng it is supposed that this element remains unchanged during the weathering processes. But certain chemical elements can be constituents of several minerals of a parent rock. During laterite formation all or almost all minerals of the original rock will be altered and the elements will be transported by weathering solutions. Therefore chemical elements do not serve as an index for balance calculations within a laterite complex.UsingGrossers method one cannot decide wether the abundance of a certain element is caused by accumulation of this element or by lost of other constituents and vice-versa.The use of the method developed byMillot u.Bonifas is not advisable except the structure of the original rock is preserved unaltered during laterite formation. This is not indicated in our case.  相似文献   

19.
贵州荔波第四纪晚近期石笋地质年表与气候事件   总被引：14，自引：1，他引：13  
南方岩溶区大型石笋年代地层学研究表明石笋是第四纪 (系 )研究的主要对象之一 ,石笋比其他第四纪沉积物更易高精度定年。贵州荔波地区以 6 8个TIMS U系正序平行测年 ,建立了第四纪晚近期 16 2 .3ka以来的地质年表 ,确定全新世与晚更新世以 9.36 3ka分界 ,而晚更新世与中更新世以12 8.5ka分界 ,提出距今 35 0年、2 30 0年……和新仙女木、类Heinrich等一系列冷事件的跃变年代 ,事件的冷暖转 (突 )变时限具区域对比意义。认定应以大型石笋系统测年建立第四纪地质年表 ,不宜用少数测年值按 2～ 3个沉积速率推算建年表 ,亦不宜以小型石笋“系统”测年建年表 ,以免因间断沉积造成自然的、人为的缺层和漏测 ,使年表失实。  相似文献   

20.
The mineralogy and chemistry of some analcime-rich igneous rocks — analcimites from the potassic Highwood province, Montana, and an analcime tinguaite from the Dunedin Volcanic Complex, New Zealand — have been investigated to obtain some indication of the KNa substitution in natural analcimes. The analcimes have potash-poor compositions, the K2O revealed by the rock analyses being represented in the mode mainly by Or-rich feldspar (hyalophane or sanidine). These data and the evidence afforded by other analcime compositions confirm earlier conclusions based on experimental studies (Peters, Luth and Tuttle, 1966), namely that analcime solid solutions may contain up to approximately 2% K2O. Some aspects of analcime-rich igneous assemblages are also discussed.  相似文献   

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