洞穴石笋沉积速率研究中值得注意的几个问题   总被引：12，自引：5，他引：7  

林玉石  张美良  覃嘉铭 《中国岩溶》2001,20(2):131-136

众多大型石笋纵剖面观测、测年和纹层沉积计率(沉积速率计算)表明,速率差异是石笋沉积特征的重要数据,也是古气候环变化的重要反映,但以往诸多资料不好引用、无从对比。通过筛选石笋的全(正)心纵剖面,沿纹层轴(中)部采样,测年值和计率可信度大,具时空对比意义。为提高精度和分辨率,提倡按石笋沉积特征段,特别是纹层组测年计率。   相似文献   

Normal faulting vs regional subsidence and sedimentation rate     

C. Doglioni  N. Dagostino  G. Mariotti 《Marine and Petroleum Geology》1998,15(8):3167

Normal faults occur in a variety of geodynamic environments, both in areas of subsidence and uplift. Normal faults may have slip rates faster or slower than regional subsidence or uplift rates. The total subsidence may be defined as the sum of the hangingwall subsidence generated by the normal fault and the regional subsidence or uplift rate. Positive total subsidence obviously increases the accommodation space (e.g., passive margins and back-arc basins), in contrast with negative total subsidence (e.g., orogens). Where the hangingwall subsidence rate is faster than the sedimentation rate in cases of both positive and negative total subsidence, the facies and thickness of the syntectonic stratigraphic package may vary from the hangingwall to the footwall. A hangingwall subsidence rate slower than sedimentation rate only results in a larger thickness of the strata growing in the hangingwall, with no facies changes and no morphological step at the surface. The isostatic footwall uplift is also proportional to the amount and density of the sediments filling the half-graben and therefore it should be more significant when the hangingwall subsidence rate is higher than sedimentation rate.  相似文献   

吉林向海沼泽湿地典型剖面沉积及年代序列重建   总被引：12，自引：0，他引：12  

王国平  刘景双  汤洁  夏威岚 《湖泊科学》2003,15(3):221-228

沼泽湿地发育过程中堆积的各类沉积物真实地记录下区域环境演变与沼泽湿地发育过程。本文以无尾河下游漫流区——向海沼泽湿地为研究对象,对其典型沉积剖面结构、沉积物容重、年龄指标、沉积速率等多项沉积记录进行了综合剖析。结果表明：沼泽沉积物的层序关系可以揭示沼泽的形成途径及环境变化;溪边沼泽接受更多的矿质沉积物;1880-1885年该区域出现河道变迁的痕迹;向海沼泽湿地沉积速率与典型的河口三角洲类似,体现了河口尾端湿地的特点;近50年来,向海沼泽湿地沉积速率急剧上升,其原因可能与解放后该流域人类活动增强、植被破坏、水土流失严重有关,在时间上,与流域上游大型露天煤矿开采时段有较好的耦合性。  相似文献   

Bed-load transport rate based on the entrainment probabilities of sediment grains by rolling and lifting     

Jun-De Li  Jian Sun  Binliang Lin 《国际泥沙研究》2018,33(2):126-136

A function for the bed-load sediment transport rate is derived. This function is obtained by using the entrainment probabilities of the rolling and lifted sediment grains, and by introducing two travel lengths, respectively. The predictions from the new bed-load function agree well with experimental results over the entire experimental range and show significant improvement over the commonly used formula for the bed-load transport rate. The new function shows that, in terms of contributing to the bed-load transport rate, the total entrainment probability of the sediment grains is a weighted summation of those for the lifted and rolling grains, rather than a simple addition of the two. The function is also used to predict the total entrainment probability, saltation length, and the bed layer thickness at a high bed-load transport rate. These predictions all agree well with the experimental results. It is found that, on average, the travel length for the rolling sand grains is about an order of magnitude less than that of the lifted grains.  相似文献   

MATHEMATICAL MODEL OF SLUDGE SEDIMENTATION     

ZHOU Kezhao  + 《国际泥沙研究》1999,(3)

1　ＩＮＴＲＯＤＵＣＴＩＯＮ　Ｓｅｄｉｍｅｎｔａｔｉｏｎｉｓａｈｙｄｒａｕｌｉｃｐｒｏｃｅｓｓｏｒａｗａｔｅｒｔｒｅａｔｍｅｎｔｐｒｏｃｅｓｓｔｏｓｅｐａｒａｔｅｓｏｌｉｄｆｒｏｍｗａｔｅｒｂｙｇｒａｖｉｔｙ,ｗｉｄｅｌｙｕｓｅｄｉｎｗａｔｅｒａｎｄｗ...  相似文献   

Land Use and Lake Sedimentation on the New England Tablelands of New South Wales,Australia     

R. J. HAWORTH  S. J. GALE  S. A. SHORT  H. HEIJNIS 《The Australian geographer》1999,30(1):51-73

Lead-210 methods have been used to establish a chronology of sedimentation extending back almost 80 years in Black Mountain Lagoon near Guyra on the New England Tablelands of north-eastern New South Wales, Australia. Estimates of the direct atmospheric fallout of unsupported ²¹⁰Pb and historical records of the pattern of phosphorus input to the lake provide support for the ²¹⁰Pb chronology. The sediments in the lake record an episode of disturbance which took place prior to c .1916, but after c .1790-1860. Since then, however, the site-specific rate of minerogenic sedimentation has been maintained at a relatively low and constant level of 0.93 kg m^-2 a^-1. [Note: the following symbols are used in this paper: a = year (annum), and d min^-1 g^-1 = radioactivity (spontaneous nuclear disintegrations per minute per gram of material).] This is despite major shifts in land use and intensification of agriculture, despite the occurrence of significant floods and droughts, and in the absence until recent times of the application of soil conservation practices. These rates may be contrasted with rates of 0.023 kg m^-2 a^-1 from the period 12.3-5.6 ka. These are at least an order of magnitude lower than those of the twentieth century. The lake sediments preserve evidence of the use of agricultural chemicals on the catchment during the twentieth century. These include phosphorus, zinc, arsenic and lead. Soils and sediments may act as long-term toxic stores for such chemicals, a problem often overlooked in rural areas.  相似文献   

THE ADVERSE IMPACT OF HUMAN ACTIVITIES ON FLOOD CONTROL IN THE HUAIHE BASIN     

Hugen ZhU Associate Prof  Dept. Of Civil Eng.  Hefei University of Technology  Hefei  China Zhaoyin WANG Prof  Dr. International Research  Training Center on Erosion  Sedimentation  P.O. Box  Beijing China Dieter PRINZ Prof. 《国际泥沙研究》1997,(3)

LIN~DUCnONTheHuaiheBasinislOCatedbetWeen31"-36"llorthemlahtudeand112"-121"easternlongitude,andcoversatotalareaofabout269,000sq.kin,OfwhichthemountainousandhillyareasocCUPyl/3,theplainsandlow-iringland2/3.ThebasinelicitSsalientphysicalgeographicalfeatllTesasfollowsf(l)Thereisnoobviousmountaindividebe~ntheWatershedoftheriVerandtheYellowforerBasinaswellastheYangtZeRadBasin.MostofthetributariesinthenoalbudoftheHuaiheforertakethesouthdikesOftheYellowherasthedivide.(2)TheriVerbedofthetr…  相似文献   

云南香格里拉图姆沟组硅质岩地球化学特征及意义     

李超民  邓江红  王国芝  任小庆 《云南地质》2014,33(3):295-301

本文就香格里拉地区图姆沟组（T3t）的硅质岩岩石学和地球化学特征进行分析研究,进而揭示出晚三叠世早期研究区属于甘孜—理塘洋盆的深水盆地环境,构造相对稳定,形成具深水沉积特征的正常生物沉积硅质岩;晚三叠世中-晚期,伴随甘孜-理塘洋盆向中咱地块俯冲消减,研究区构造活动强烈,热水来源广泛,则主要形成热水沉积硅质岩.  相似文献   

Characteristics of sedimentation and channel adjustment linked to the Three Gorges Reservoir     

Xiaoya Tang  Sichen Tong  Guoxian Huang  Guangxiang Xu  Xinghua Li  Kun Lei  Shiming Yao 《国际泥沙研究》2021,36(2):177-189

Construction of large dams is attractive because of their great benefits in flood control,hydropower generation,water resources utilization,navigation improvement,etc.However,dam construction may bring some negative impacts on sediment transport and channel dynamics adjustments.Due to the effects of recent water and soil conservation projects,sediment retention in the newly constructed large upstream reservoirs,and other factors,the sedimentation in the Three Gorges Reservoir(TGR)is quite different from the amount previously predicted in the demonstration stage.Consequently,based on the measured data,characteristics of sedimentation and the related channel deformation in the TGR were analyzed.The results imply that sediment transport tended to be reduced after the Three Gorges Project(TGP).Sedimentation slowed dramatically after 2013 and indicated obvious seasonal characteristics.Due to the rising water level in the TGR in the flood season,the yearly sediment export ratio(Eratio)was prone to decrease.The water level near the dam site should be reasonably regulated according to the flow discharge to improve the sediment delivery capacity and reduce sedimentation in the TGR,and to try to avoid situations where the flood retention time is close to 444 h.The depositional belt was discontinuous in the TGR and was mainly distributed in the broad reaches,and only slight erosion or deposition occurred in the gorge reaches.Sedimentation in the broad and gorge reaches accounted for 93.8% and 6.2% of the total sedimentation,respectively.The estuarine reach located in the fluctuating backwater area experienced alternate erosion-deposition,with a slight accumulative deposition in the curved reach.Sedimentation mainly occurred in the perennial backwater area.The insight gained in this study can be conducive to directly understanding of large reservoir sedimentation and mechanism of channel adjustment in the reservoir region in the main channel of large river.  相似文献   

Efficient trapping of organic carbon in sediments on the continental margin with high fluvial sediment input off southwestern Taiwan   总被引：2，自引：0，他引：2  

Shuh-Ji Kao  Fuh-Kwo Shiah  Chung-Ho Wang  Kon-Kee Liu   《Continental Shelf Research》2006,26(20):2520-2537

Accumulation rates of marine and terrigenous organic carbon in the continental margin sediments off southwestern Taiwan were estimated from the measured concentrations and isotopic compositions of total organic carbon (TOC) and previously reported sedimentation rates. Surficial sediments were collected from the study area spanning from the narrow shelf near the Kaoping River mouth to the deep slope with depths reaching almost 3000 m. The average sediment loading of Kaoping River is 17 Mt/yr, which yields high sediment accumulation rates ranging from 0.08 to 1.44 g cm⁻² yr⁻¹ in the continental margin. About half of the discharged sediments were deposited on the margin within 120 km of the river mouth. Carbon isotopic compositions of terrestrial and marine end-members of organic matter were determined, respectively, based on suspended particulate matter (SPM) collected from three major rivers in the southwestern Taiwan and from an offshore station. All samples were analyzed for the TOC content and its isotopic composition (δ¹³C_org). The SPM samples were also analyzed for the total nitrogen (TN) content. TOC content in marine sediments ranges from 0.45% to 1.35% with the highest values on the upper slope near the Kaoping River mouth. The TOC/TN ratio of the SPM samples from the offshore station is 6.8±0.6, almost identical to the Redfield ratio, indicating their predominantly marine origin; their δ¹³C_org values are also typically marine with a mean of −21.5±0.3‰. The riverine SPM samples exhibit typical terrestrial δ¹³C_org values around −25‰. The δ¹³C_org values of surficial sediments range from −24.8‰ to −21.2‰, showing a distribution pattern influenced by inputs from the Kaoping River. The relative contributions from marine and terrestrial sources to sedimentary organic carbon were determined by the isotope mixing model with end-member compositions derived from the riverine and marine SPM. High fluvial sediment inputs lead to efficient trapping of organic carbon over a wide range of water depth in this continental margin. The marine organic accumulation rate ranges from 1.6 to 70 g C m⁻² yr⁻¹ with an area weighted mean of 4.2 g C m⁻² yr⁻¹, which is on a par with the mean terrestrial contribution and accounts for 2.3% of mean primary production. The depth-dependent accumulation rate of marine organic carbon can be simulated with a function involving primary productivity and mineral accumulation rate, which may be applicable to other continental margins with high sedimentation rates. Away from the nearshore area, the content of terrigenous organic carbon in surficial sediments decreases with distance from the river mouth, indicating its degradation in marine environments.  相似文献