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利用湖泊清淤工程,对武汉东湖(官桥湖)湖泊沉积物进行了垂向样品的采集并测量了其环境磁学参数和重金属元素含量。根据其沉积物垂向磁性变化特征,以沉积速率作为时间标尺,结合东湖周边地区相关工业资料,初步建立了该"磁记录"与东湖周边地区城市化过程中环境演化的关系。结果表明,粒度较细且为准单畴颗粒、低矫顽力的亚铁磁矿物主导了沉积物的磁性特征。在深度44cm之下,磁参数量值均较低;在深度44~6cm之间,沉积物磁参数量值随深度的减小而逐步平稳增加;由深度6cm至表层,磁参数量值随深度减小而减小。沉积物的磁性变化特征与1956年以来的钢铁产量、机动车保有量和人均GDP变化均较为一致。 相似文献
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基于沧县隆起400 m ZKQ1孔沉积特征、综合测井、测年(AMS14C、光释光)以及磁性地层等综合研究,并与前期6个钻孔磁性地层对比,表明该区域前中更新世盆—山快速发育,黄骅坳陷和沧县隆起两大Ⅲ级构造单元以及次一级构造单元(里坦凹陷、天津西凹槽、板桥凹陷和港西凸起)均存在较高的沉积速率和明显的差异性沉积演化.中更新世时期,该区存在沉积间断,各构造单元差异性沉积不明显,趋于准平原化,仅局部残留少许的沉积物容纳空间,证实了该区沧东断裂、天津断裂及大城断裂等主干隐伏断裂上延至中更新世地层.晚更新世以来,该区域发育3期区域性的"面状分布"的海侵层,其层位、沉积厚度及沉积速率稳定,整体处于稳定沉降期. 相似文献
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《矿物岩石地球化学通报》2017,(3)
为了研究新安江水库过去环境变化和预测区域环境质量,选取了水库的3个代表性区域采集沉积物柱心,运用放射性核素计年技术、结合粒度变化特征,计算了水库建库以来的分段沉积速率,分析了沉积环境演化。研究发现,湖心区沉积柱在32 cm处存在明显的~(137)Cs识别峰,该峰时标为1964年。基于~(210)Pb CRS计年模型获得库区过去60年的沉积年代,32 cm处时标为1963年,与~(137)Cs计年结果一致;两者1964~2015年平均沉积速率均为0.23 g/(cm~2·a)。放射性核素计年与沉积事件研究表明,利用沉积物粒度变化指示的沉积事件能够为近代沉积计年提供可靠的依据;结合各点分段沉积速率,说明建库事件相较于大范围泄洪对沉积速率的影响更大。 相似文献
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洞穴石笋沉积特征研究--以贵州荔波董歌洞4号石笋为例 总被引：8，自引：1，他引：7
在综合研究南方20多个大型石笋纵剖面的基础上,以董歌洞4号石笋为代表,论述石笋沉积特征与气候演化的对应性.4号石笋从距今147.838±2.6 ka开始沉积以来,形成了53个沉积纹(壳)层组,组成24个亚旋回,构成9个旋回,呈现韵律式旋回性沉积特征.石笋纹(壳)层组分、结构、叠复构造呈多级次旋回性很突出,其中沉积间断具普遍性、沉积速率具多变性,间断和速率变化级次亦明显.以系统测试和测年引证沉积特征的同时揭示:①～⑨旋回间沉积间断时间累积达75.804 ka,占石笋形成时间的51.21%,①～⑨旋回实际沉积时间仅72.222 ka,占形成时间的48.79%;④旋回之前,沉积速率很小,最小仅0.36 mm/100a,比最大速率小22～24倍,自⑤旋回起,沉积速率很大,最大达39.03 mm/100a,是最小速率的3.8倍.石笋沉积特征与气候环境演化的成生关系表明,石笋沉积多旋回性的纹(壳)层组、亚旋回、旋回与气候演化的气候期、阶段和旋回彼此对应,石笋沉积的多级次旋回及其变化就是气候演化的级次及旋回性转(跃)变时间,彼此同时显示.论证了石笋沉积的多旋回性与气候演化的不稳定性,及其彼此协调的宏观、微观综合表现特征. 相似文献
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测井曲线旋回分析在碳酸盐岩层序地层研究中的应用* 总被引：4，自引：2，他引：2
在碳酸盐岩台地沉积层序的研究中,通过旋回计数和厚度测量,采用费希尔图解法解析高频米级旋回或副层序的叠置形式和空间结构,进而标定三级沉积层序的界面,是目前普遍采用的一个方法。但是,这一方法目前主要用于露头层序地层学研究,而在地下油气勘探区受到极大的限制。文中提出了一种新的计算方法,它可以根据测井资料求取任一地层段沉积旋回的个数和厚度。根据数值模拟,详细讨论了海平面变化周期和幅度与沉降速率、沉积速率的相关关系,提出高频沉积旋回的分布模式和叠加样式可以指示低频海平面变化的轨迹,这为划分三级沉积层序、标定层序界面提供了理论依据。最后,以川西北地区中三叠统雷口坡组为例,说明了应用自然伽马测井资料进行数据处理的流程和步骤,以及根据旋回厚度累积偏差曲线标定层序界面的位置、识别旋回谱系标志。 相似文献
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武昌地区街道尘埃磁学特征及其对环境污染的指示意义 总被引：1，自引：0，他引：1
对在武昌地区4个功能区域(青山、洪山、东湖风景区、东湖开发区)主要交通街道收集的尘埃样品进行详细的环境磁学测量,包括质量磁化率、频率磁化率、等温剩磁退磁系数以及典型样品的磁滞回线参数等。研究结果表明:尘埃样品中剩磁载体均以亚铁磁性矿物为主,样品中的磁性颗粒呈现低矫顽力的磁铁矿特征,软磁性的磁性矿物是样品剩余磁性的主要载体。尘埃样品χ、SIRM的区域分布特征受区域周围工业、车流量及道路状况等多种环境因素的影响,在4个功能区域中存在明显的磁性差异:青山工业区污染较重,东湖开发区、洪山、东湖风景区次之;硬剩磁(HIRM)的分布可能指示了道路交通来源的磁颗粒特征,东湖开发区和青山工业区由于行驶的货车和重型车辆较多,表现出硬剩磁量值较高。与其他城市(兰州、西安、南京、徐州等)相比,整个武昌地区街道尘埃样品的磁性含量仍较高,说明在城市环境方面还有待于进一步改善和保护。 相似文献
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对南海５个深海短柱样的磁性地层学特征进行研究后表明，在陆坡柱样沉积物中位于岩芯深约３ｍ处的反向磁性段可与蒙戈磁偏移相对比。因此，对沉积速率相对较高的陆坡碳酸盐相而言，利用反向磁偏移地层事件，可以对代表地质时限较短的深海短柱样进行等时面分析。 相似文献
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论扬子地区上奥陶统五峰组观音桥段的深海成因 总被引：9，自引：0，他引：9
通过对沉积速率与现代深海沉积速率的比较及古生态学、生物古地理学、海平面变化以及沉积特征综合的分析 ,认为观音桥段形成于深海环境中 ,且属深海等深流沉积。奥陶 -志留系之交广泛发生的高频火山事件可能是生物灭绝的主要和直接原因 ,而火山事件、铱和碳同位素异常事件与志留纪初期缺氧事件在奥陶 -志留系之交的耦合作用可能是 H irnantia- Dalmanitina动物群的灭绝的主要原因。 相似文献
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2013年我国首次在南海东北部东沙陆坡实施天然气水合物钻探,并获取块状等可视天然气水合物样品.为了解钻区地层、天然气水合物产出带(the zone of gas hydrate occurrence)或天然气水合物储层的地层时代和沉积速率特征,对其中5个站位(GMGS05、GMGS07、GMGS08、GMGS09和GMGS16) 的岩心沉积物进行钙质超微化石、有孔虫生物地层学和沉积速率变化的研究.钻孔取心最大深度为213.55 m.共识别出第四纪中更新世以来3个钙质超微化石事件和2个有孔虫事件,确定了钻探区所钻达最老地层为中更新统;天然气水合物产出带的地层时代为中更新世-全新世约0.44 Ma以来.钻区0.12 Ma以来的沉积速率介于36.9~73.3 cm/ka之间,平均值高达54.2 cm/ka,0.44 Ma以来平均沉积速率为47.4 cm/ka,表明东沙海域天然气水合物钻探区位于一高沉积速率堆积体上,高沉积速率更有利于天然气水合物的成藏,该结论与前人研究结果一致. 相似文献
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柴达木盆地察尔汗古湖贝壳堤剖面粒度特征及其沉积环境 总被引：15，自引：2，他引：13
通过对柴达木察尔汗盐湖贝壳堤剖面沉积物粒度、碳酸盐和磁化率的对比,结合沉积物粒度频率曲线与多种粒度参数分析,详细讨论了研究剖面形成过程中物质搬运和沉积作用以及所反映的环境变化。结果表明沉积物粒度特征指示了湖泊水位的相对变化。在距今约38.2 ka BP（14-C年代,未校正。下同）左右,沉积记录指示古湖泊的范围和水位已达到剖面位置,之后湖泊继续扩张、水位波动上升;在距今约35.5 ka BP,粒径有一突然变细又变粗的过程,可能为一次较快速的湖面波动;在距今约35.5 ～ 33.3 ka BP之间,沉积物颗粒较粗,碳酸盐含量和磁化率值低,揭示湖泊水位较低。距今约33.3 ～ 27.1 ka BP之间,沉积物颗粒较细,碳酸盐含量较前一阶段高,表明此阶段湖泊水位相对较深,但粒度、碳酸盐和磁化率等指标也记录了三次较明显的湖泊快速但短暂的退缩过程;在距今约29.7～28.3 ka BP,沉积物颗粒最细,指示了此时期可能为湖泊水位最高期。从距今约27.1 ka BP开始,沉积积物颗粒明显变粗,揭示湖泊进入到退缩期,距今约18.1 ka BP,粒度指标的变化和上层的盐壳指示湖泊进入快速盐化阶段,之后湖泊退出剖面所在的位置,此后研究区湖泊水位再也没有达到这个高度。 相似文献
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柴达木盆地察尔汗盐湖CH0310钻孔沉积物磁化率及其影响因素分析 总被引：2，自引：1，他引：1
通过对长为523 m的柴达木盆地察尔汗盐湖CH0310钻孔沉积物岩性、磁性特征、高频质量磁化率、低频质量磁化率、频率磁化率和总有机碳（TOC）的实验分析,结果表明:CH0310钻孔中磁铁矿是沉积物磁化率的主要贡献者;由于受气候和环境的影响与控制,以弱氧化环境为主CH0310钻孔中沉积物的磁化率与粗砂粒级含量成正相关与粘土级含量反相关关系;进一步对磁化率和TOC的相关性分析发现,在不同的沉积层磁化率和TOC的相关性表现出正负差异,这反映了磁化率对气候与环境的响应模式在CH0310钻孔不同层位并不完全相同,揭示出湖泊磁化率影响因素的复杂性和它作为气候代用指标的不确定性,因此认为对于地处高原干旱区沉积速率快、沉积层特别厚的湖泊来说,如果用单一的磁化率指标来反映或恢复古气候和古环境的变化需要特别慎重。 相似文献
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Melissa A. Watchorn Paul B. Hamilton R. Timothy Patterson 《Environmental Earth Sciences》2013,68(7):1823-1834
Haynes Lake is a small kettle lake located on the Oak Ridges Moraine, and is within the Greater metropolitan area of Toronto, Ontario; Canada’s most populous region. Lake sedimentation, flux rates, diatoms and thecamoebians extracted from a benthic core were used as biological proxies to evaluate changes in water quality through time as a function of anthropogenic activity and changing climate. There were two periods of disturbance to the Haynes Lake ecosystem from ca 8,500 years before present (YBP) through to ca A.D. 2003, which were significant enough to cause changes in lake sedimentation, the diatom flora, and thecamoebian fauna. The first disturbance was concomitant with the decline in global temperatures following the Hypsithermal Climate Optimum (ca. 4,700 YBP). The most significant disruption to Haynes Lake over the last 8,500 years, however, was the settlement of Europeans and subsequent urban development (ca. A.D. 1875), including the construction of a road immediately adjacent to the lake. Anthropogenic disturbance of inorganic clays in the recent paleosediment record (<5 cm) is indicative of more recent eutrophication events. 相似文献
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中国是世界上地震多发的地区之一。在各省份中,处于中国西南部的云南省是地震发生最多的省份之一。云南省省会昆明以南60 km处的抚仙湖位于小江地震带和通海-石屏地震带的交汇处,该地区的地震频次又居云南省之首。如果能在抚仙湖的沉积物中找到历史地震的自然记录并解释其机理,就意味着发现了一个由抚仙湖自然形成的地震记录仪。提供了证明抚仙湖区域历史地震自然记录存在的证据---抚仙湖沉积物的磁化率。我们在抚仙湖的中心地带、水深108 m处,钻取到了170 cm长的抚仙湖沉积物剖面,经测试证明它对应着近1 000年,约公元1025年至今的沉积年代。在研究中,沉积物磁化率的峰值突变与过去1 000年中许多有历史记载的地震事件相吻合。此外,一些尚没有记载的古地震事件也通过对湖底沉积物磁化率的分析而得以发现。 相似文献
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DONG Jin GAO Rui WANG Yong ZHANG Shihong YAO Peiyi CHI Zhenqing ZHAO Zhili 《《地质学报》英文版》2013,87(1):186-196
The detailed magnetic susceptibility anisotropy study on the sediments of two sections, which are located in the lake-center and the lakeshore of the Huangqihai Lake,Inner Mongolia, revealed their hydrodynamics and sedimentary environment changes in the recent 2000 years.The results show that the sediments of two sections both display normal depositional magnetic fabrics,of which the minimum susceptibility axes（K3） are oriented perpendicular to the bedding plane and the maximum magnetic susceptibility axes（K1） lie parallel with the bedding plane.In addition,the lakeshore presents higher magnetic anisotropy degree（P）,magnetic foliation（F） and current factor （Fs） than the lake-center,showing that the lakeshore has higher flow velocity.For the west Huangqihai Lake（HQW） section in the lake-center,the magnetic matrix grain degree（Q） and the inclination of the minimum susceptibility axes sharply increased and decreased,respectively,at a depth of about 10 cm,24 cm,45 cm and 74 cm,which indicate abnormal depositional events with strong kinetic energy.Through comparative analysis,the HQW section can be divided into three stages from top to bottom.The upper stage was a stable depositional environment with strong hydrodynamic energy and low water level,which shows relatively higher Fs value and the Q value varies similarly with P and F.The middle stage was a stable depositional environment with high water level and low hydrodynamic energy,intermitted with high-energy abnormal events,which shows relatively lower Fs and the Q value was negatively correlated with P and F.The lower stage was an unstable depositional environment with low hydrodynamic energy and high water level,which shows relatively lower P,F,and Fs value. 相似文献
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With accelerated melting of alpine glaciers, understanding the future state of the cryosphere is critical. Because the observational record of glacier response to climate change is short, palaeo‐records of glacier change are needed. Using proglacial lake sediments, which contain continuous and datable records of past glacier activity, we investigate Holocene glacier fluctuations on northeastern Baffin Island. Basal radiocarbon ages from three lakes constrain Laurentide Ice Sheet retreat by ca. 10.5 ka. High sedimentation rates (0.03 cm a?1) and continuous minerogenic sedimentation throughout the Holocene in proglacial lakes, in contrast to organic‐rich sediments and low sedimentation rates (0.005 cm a?1) in neighbouring non‐glacial lakes, suggest that glaciers may have persisted in proglacial lake catchments since regional deglaciation. The presence of varves and relatively high magnetic susceptibility from 10 to 6 ka and since 2 ka in one proglacial lake suggest minimum Holocene glacier extent ca. 6–2 ka. Moraine evidence and proglacial and threshold lake sediments indicate that the maximum Holocene glacier extent occurred during the Little Ice Age. The finding that glaciers likely persisted through the Holocene is surprising, given that regional proxy records reveal summer temperatures several degrees warmer than today, and may be due to shorter ablation seasons and greater accumulation‐season precipitation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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笔者通过西藏佩枯错盆地帮荣组剖面的野外地质调查以及沉积物粒度、磁化率、碳酸盐等环境指标的分析,结合ESR法和U系测年资料,分析了晚更新世帮荣组沉积环境演化特征。分析结果表明,127～15kaB.P.的晚更新世时,佩枯错盆地进入强烈断陷阶段,佩枯错古湖经历了初始浅湖期,发展深湖期和萎缩浅湖期一个完整的湖泊演化过程。127～56kaB.P.,气候温暖湿润,湖水增加,古湖发育进入浅湖期;56～31kaB.P.,湖水波动上升,古湖进入发展深湖期;31～15kaB.P.,湖泊步入萎缩浅湖期,15kaB.P.左右出现的冻融褶皱,可能指示该区进入冰缘期。 相似文献
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Analysis of well logs of Lake Baldeney, a reservoir of the Ruhr River, yields four facies factors that reflect the effect of anthropogenic processes on the sediment. First, the sedimentation rate is directly related to the subsidence caused by mining. The extent of the subsidence was such that the sediment load of the river could not compensate for the sinking of the lake bottom. Discharged sediment filled about one-fifth of the basin within 40 years. In certain areas of the basin the sedimentation rate reached up to 10 cm per year. Second, the grain-size distribution of the sediment was influenced by long-term and short-term events. During the subsidence, grain-size distribution remained relatively constant. The destruction of the Möhne River dam during World War II resulted in the presence of an extremely large grain size as evidenced by the so-calledMöhnelage. The filling of the lake after 1961 was accompanied by a continual increase in medium grain size. Third, until 1975, the mode of the lake sediment reflects the effect of mining in the vicinity of the lake. High coal content can be traced to its origin. The introduction of modern production processes, modernization of coal dressing, and hydraulic hauling is documented in the sediment. Finally, the heavy metal content of the sediment corresponds to the industrial development in the drainage area the Ruhr River. The accumulation of Cd reached an extreme concentration, exceeding the natural content by a thousand times. Variation in concentration reflects an increase in industrial production, as well as measures undertaken to restore water quality. 相似文献
19.
Nore Praet Maarten Van Daele Tim Collart Jasper Moernaut Elke Vandekerkhove Philipp Kempf Peter J. Haeussler Marc De Batist 《Sedimentology》2020,67(5):2332-2359
Turbidites embedded in lacustrine sediment sequences are commonly used to reconstruct regional flood or earthquake histories. A critical step for this method to be successful is that turbidites and their trigger mechanisms are determined unambiguously. The latter is particularly challenging for prehistoric proglacial lake records in high-seismicity settings where both earthquake-generated and flood-generated turbidites interrupt the background varved sedimentation. This calls for a new method to allow efficient and objective identification and classification of turbidites. This study examined turbidites in five long (9 to 17 m) sediment cores from Eklutna Lake, a proglacial lake in south-central Alaska, using standard core logging and grain-size data. A novel statistical approach is presented, in which varve-thickness distributions were first analyzed to objectively identify the thickest turbidites and distinguish them from background sedimentation. For each turbidite, a selection of variables were then measured, including: basal grain-size, thickness, magnetic susceptibility and spectrophotometric variables. Triggering mechanisms were discriminated by a combination of principal component analysis and clustering, and by calibration with historical events. Using this approach, a 2250 year long lake-wide event stratigraphy was constructed, with 94 prehistoric events, including 24 earthquake and 70 flood events. Basal grain-size and thickness variables turn out to be the most effective proxies for discrimination. This statistical approach is a powerful and new method to identify turbidites and their triggering mechanisms in long prehistoric sediment records. It opens up new prospects for palaeoseismological, palaeohydrological and palaeoclimate studies in proglacial lakes worldwide. 相似文献
20.
通过对乌伦古湖2个沉积柱样的210Pb和137Cs剖面的观测,运用210Pb过剩法和137Cs时标法估算了近几十年来的平均沉积速率。研究结果表明：210Pb过剩法的CRS模式测定的沉积速率的变化范围为0.018～0.071 g/(cm2·a),137Cs时标法测定沉积速率的变化范围为0.034～0060 g/(cm2·a),两者具有较高的一致性。20世纪60年代以前,人类活动对本区影响相对较小,湖泊的沉积速率主要受自然因素的影响;20世纪60年代以后,随着乌伦古河中、下游农业的发展和调水工程的实现,人类活动逐渐成为主导湖泊演化的因素,从而影响乌伦古湖沉积速率。 相似文献