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1.
钻探证实,镇江市谏壁镇长江北岸高桥镇北部埋藏硬粘土层,之上为冰后期松散沉积物。沉积物主要为粉砂、粘土质粉砂、砂泥互层,中部局部夹含细砾中细砂,顶部见淤泥质粘土;夹数十层植物炭屑层;以水平纹理为主,局部见小型交错层理、波状层理。表明冰后期以来该地处于水动力较弱的河湖环境,为多期湖沼相沉积夹汉道河流相沉积,局部有海相沉积物加入。根据碳化植物碎屑^14C年龄,推测冰后期底界年龄约13000aBP,海侵到达该地的时间约为9000aBP,海侵最高位时间约为6500aBP。冰后期平均沉积速率约为4．9m／ka,湖沼相3．4～6m／ka,河流相10～15m／ka。对全新统的底界年龄和海相层的埋藏深度进行了讨论。 相似文献
2.
内陆干旱区柴达木盆地苏干湖年纹层的发现及其意义 总被引：5，自引：0，他引：5
柴达木盆地北缘苏干湖若干钻孔岩芯发现, 水深大于3.0 m的沉积物均具有裸眼可分辩的由深色层和浅色层组成的纹层层理. 以湖泊中心SG03I孔上部5.5 m具有纹层结构的沉积岩芯为研究对象. 基于沉积物收集装置的现代过程研究发现, 苏干湖夏秋季以浅色的单水方解石为主, 冬半年以深色有机质为主, 现代湖泊能够形成冬半年深色层和夏半年浅色层的纹层沉积. 岩芯中有四种类型的纹层沉积: 单水方解石-有机质纹层、白云石-有机质纹层、碎屑-硅藻(碎屑)纹层与文石-有机质纹层, 均具有季节特征, 属可靠的年纹层, 且顶部纹层计年与210Pb测年结果一致. 根据纹层计年, 年纹层沉积形成于距今2670 a以来. 苏干湖纹层沉积是中国西部干旱区发现的第一个能够确认为是年纹层的湖泊沉积, 4种不同类型的年纹层指示了不同气候类型及其季节差异, 具有重建高分辨率气候变化的重要意义. 相似文献
3.
《地震地质》2016,(4)
晚更新世以来地层的形成受气候、构造活动的影响,并记录其过程。因此,建立晚更新世以来的地层序列,对于气候变化、活动构造、地貌成因等研究十分重要。若尔盖盆地位于青藏高原的东部边缘,中国季风区和青藏高原区的交会地带,对气候变化敏感,构造活动也很强烈,建立盆地晚更新世以来的地层序列可以促进气候变化、构造活动研究。根据若尔盖盆地的湖相钻孔、泥炭矿、河流阶地和探槽等揭露的26个典型地层剖面,结合14C和OSL等测年方法获得的200多个同位素年龄,对晚更新世以来的地层进行对比和划分,得到地层综合柱状。晚更新世中期以来划分6个沉积韵律(75~55kaBP,55~33kaBP,33~20kaBP,20~11kaBP,11~4kaBP,4~0kaBP)和6个标志层(75~55kaBP和22~20kaBP的粉细砂层,13~9kaBP的青灰色粉细砂或灰—青灰色砾石沉积,5~4kaBP、3.5~2kaBP、0.5~0.3kaBP的黑色含炭质砂质黏土沉积)。沉积序列和构造-气候关系紧密,一方面沉积韵律与气候旋回基本吻合,与深海氧同位素阶段有较好的对应关系;另一方面,沉积层岩性特征也受到北侧的东昆仑断裂带和西侧的龙日坝断裂带新构造期持续活动的影响,沉积过程主要受气候控制,地层厚度及其空间分布的差异也受到构造活动影响。 相似文献
4.
石场－中楼盆地位于郯庐断裂带中段的沂河－沭河地区。郯庐断裂左旋切割了秦岭－大别－胶南造山带及前中生代地层,研究区内沂河－沭河断裂切割了年龄为１３６．２Ｍａ（４０Ａｒ／３９Ａｒ法）的胶南造山带北缘剪切带,并被时代为１１９Ｍａ（Ｋ－Ａｒ法）的青山群地层不整合覆盖,显示郯庐断裂在早白垩世曾发生了明显的走滑运动。石场－中楼盆地受沂河－沭河断裂的控制,整体为长６０ｋｍ、宽３０ｋｍ,长宽比近于２∶１的“菱型”构造盆地。盆地内早白垩世莱阳群的沉积厚度大于６２６３．７１ｍ,沉积速率大于０．４ｍｍ／ａ;沉积相特征反映盆地具有深而窄,沉积速度快、沉积相变剧烈的特点。盆地沉积中心的迁移方向与边界断裂的左旋走滑效应一致,“边走滑边沉积”的特征明显。根据构造背景、构造格架及沉积特征,确定石场－中楼盆地为郯庐断裂早白垩世左旋走滑过程中形成的拉分盆地 相似文献
5.
C油田钻后揭示砂体横向变化快,需利用地震沉积学刻画储层平面展布,进一步落实储层.通过地震沉积学技术,识别了曲流河、辫状河、三角洲前缘及平原三类沉积体,理清了花上段垂向沉积演化规律.垂向上由三角洲平原演变为三角洲前缘、辫状河,最后演变为曲流河.研究区发育薄层、厚层及互层三类储层,不同类型的储层需采用不同策略去刻画.对于薄层,要小时窗提取属性,同时多属性融合刻画;对于厚层,要大时窗提取属性刻画;对于互层,要抓重点层合并刻画,反演地震和常规地震相结合分析.在落实储层的基础上,对C油田进行潜力搜索.H4层在C-A1井西侧储层上倾尖灭,具备发育岩性圈闭的条件,是下一步挖潜的主要方向. 相似文献
6.
在等时层序格架建立的基础上,利用地震资料研究各体系域内部沉积体的空间展布、叠置样式和沉积演化过程,进而预测各体系域中砂体的分布,是层序地层学应用于勘探实践的重要内容.OpendTect系统在三维地震倾角扫描的基础上,①以地震采样点空间信息为导向,实现了层序界面控制下的地震小层自动追踪,可以精细刻画出体系域内部沉积体地震反射结构和空间展布;②通过对各层序单元内部地震小层追踪结果进行层拉平,实现了时间域到Wheeler域的自动变换,可以更加直观地分析地层沉积演化历史;③通过沿沉积体内部小层面提取地震属性,实现了等时地层切片的提取,减少了地震属性多解性,提高了预测精度.OpendTect系统提供了一种新的基于层序地层的地震综合解释技术和思路. 相似文献
7.
全新世以来珠江三角洲的地层层序和演变过程 总被引：2，自引：0，他引：2
本文基于对90个拥有全新世14C年代数据的钻孔进行详细的沉积物特征和年代地层分析,讨论了全新世珠江三角洲的地层特征及全新世以来的充填过程.全新世珠江三角洲沉积物覆盖在末次冰期冰盛期形成的风化侵蚀面与底砾层之上.最大海侵面位于松软海相淤泥层位.在受潮汐冲刷区域,最大海侵面表现为侵蚀面.全新世沉积层序自下向上在古河谷为河流相、河漫滩-河口湾相、河口湾-三角洲相,在古河间地为滨海相、河口湾相和三角洲相.全新世沉积层垂向堆积序列绝大部分表现为下粗上细的正向序列,且不具有典型Gilbert三角洲的前积层、顶积层等沉积层序.受控于独特而复杂的地貌边界,古珠江河口湾在高水位体系域的演变模式不同于世界其他大型三角洲,而是一个多源复合、不同尺度河流沉积体独立并行发展,最后复合成的三角洲.全新世以来珠江三角洲的演变可以分为5个阶段：第一阶段12~8kaBP,全新世海侵未达三角洲中部地区,直至约9kaBP以后,南部一些地势较低的地区才开始受海进影响,出现一些海陆交互相沉积;第二阶段8~6kaBP,海面快速上升,珠江三角洲大部分地区接受海进沉积;第三阶段6~4kaBP,全新世海侵达到盛期,古珠江三角洲地区大面积为河口湾,且受系列岛屿的阻隔分为两部分,上部是与河流相接的半封闭的内古海湾;下部是与海洋相接的外古海湾,两部分仅由若干峡口相通,河流沉积物主要在内古海湾中堆积充填;第四阶段4~2kaBP,在复杂边界对河流与海洋动力的重塑和改造作用下,内古海湾各区域的沉积同时进行,独自发展;第五阶段2kaBP至今,该阶段三角洲的演变已不再是单纯的自然过程,而是自然和人类共同塑造的过程. 相似文献
8.
9.
浑善达克沙地的光释光年代序列与全新世气候变化 总被引：4，自引：0，他引：4
浑善达克沙地具有对气候变化响应敏感和生态环境脆弱的特点,是研究环境变化的理想地区．相对于黄土而言,沙质沉积是近源、在沉积期堆积速率快,有可能记录了某些时间段千年时间尺度的干旱事件．应用光释光测年技术,对浑善达克沙地东北．西南断面上具代表性的10个沙丘和沙／黄土剖面进行了年代测试,获得了35个样品的光释光年龄;结合野外地层观察分析和粒度、磁化率等测试,得到了浑善达克沙地全新世干旱事件和相对湿润期的气候变化记录：在距今9．9～8．2ka期问,沙地发育厚层粗砂层,沙丘处于活动状态,气候干燥,植被覆盖度低;在距今8．0～2．7ka期间,沙地发育有多层浅灰一灰黑色砂质土壤,沙丘总体上处于固定．半固定状态（也含有短时段的沙丘活化的干旱事件）,指示气候较之前明显湿润,植被相对茂密;2．3ka以来,沙地沉积物以粗砂堆积为主,沙丘又重新活化,气候总体上为干旱．通过对沙丘沉积记录和沉积产状的分析,发现浑善达克沙地在全新世早期、8．2ka前后以及小冰期时期,气候较为干旱,植被盖度小,沙丘活化;在“隋唐暖期”和“中世纪温暖期”,气候较湿润,植被发育良好,沙丘固定．具有绝对释光年龄控制的沙丘沉积记录表明,全新世浑善达克沙地多次千年时间尺度的气候事件可能是全球气候变化的区域响应． 相似文献
10.
湖泊是风成沉积的理想载体,利用扫描电镜分析石英砂的表面微结构特征,可以用于判断石英颗粒被风或水流搬运的相对距离和湖泊的水动力条件,从而判断其沉积环境与演化历史.库赛湖位于青藏高原北部可可西里地区,是青海省沙尘天气频发的地区之一,为进一步证实库赛湖年纹层粗颗粒层的风成成因,以库赛湖沉积年纹层为研究对象,结合青藏高原北部典型沙丘沉积、库赛湖冰面风成沉积、典型河流沉积和库赛湖湖滨相水成粗颗粒沉积样品,利用扫描电镜对上述沉积物石英颗粒表面特征进行观察研究,并统计35种特征的出现频率.结果表明:库赛湖地区典型风成物石英颗粒表面具有圆形轮廓、中低浮雕、翻板、新月型撞击坑、球根状边缘、直形阶梯、弓形阶梯、碟形坑等微形貌特征;典型水成物石英颗粒表面具有V型撞击坑、小型和中型贝壳状断口、少量溶蚀坑等微形貌特征;库赛湖年纹层粗颗粒层石英颗粒表面具有圆形轮廓、低浮雕、翻板、新月形撞击坑、球根状边缘、碟形坑等明显风成特征,与研究区风成物的石英颗粒表面特征相似,而与研究区典型水成物的石英颗粒表面特征差别很大.因此,库赛湖年纹层中的粗颗粒层是由风成作用形成的. 相似文献
11.
Variation characteristics of heavy metals and nutrients in the core sediments of Taihu Lake and their pollution history 总被引：4，自引：2，他引：4
The sedimentary environment change, trophic evolution and heavy metals pollution history of the northern Taihu Lake in the last 100 years are studied according to the sedimentary geo-chemical proxies of the core sediments, such as grain size, nutrients, heavy metals, diatom, etc. The nutrients in the sediments depended mainly on the lake internal circulation and the heavy metals were from natural geogenic sources before the 1920s, which were not influenced by human activities generally, and grain size was one of the key factors influencing heavy metals content in the sediments. The alternation of manner and strength of human activities in Taihu Lake catchment before and after the 1920s made the lake sediments coarser, and hence heavy metals and TP content decreased contrasted with that before the 1920s. TP content in sediments and water increased from the 1950s to late 1970s due to anthropogenic pollutants discharge, and the lake belonging to mesotrophic state. TN and TOC content and C/N ratio increased due to the increasing external pollutants into Taihu Lake by human activities, TP content also increased obviously in water and sediments, and the diatom association was dominated by eutrophic species since the late 1970s, indicating the eutrophication state of Taihu Lake in this period. Meanwhile the increasing in heavy metals content, such as Cu, Mn, Ni, Pb and Zn, and their proportion of valid fractions in the sediments indicates that they all result from human pollutants since the late 1970s. The heavy metals in the surface sediments have certain potential biological toxicity due to the higher SEM/AVS ratio. 相似文献
12.
Variation characteristics of heavy metals and nutrients in the core sediments of Taihu Lake and their pollution history 总被引：1，自引：0，他引：1
The sedimentary environment change, trophic evolution and heavy metals pollution history of the northern Taihu Lake in the last 100 years are studied according to the sedimentary geochemical proxies of the core sediments, such as grain size, nutrients, heavy metals, diatom, etc. The nutrients in the sediments depended mainly on the lake internal circulation and the heavy metals were from natural geogenic sources before the 1920s, which were not influenced by human activities generally, and grain size was one of the key factors influencing heavy metals content in the sediments. The alternation of manner and strength of human activities in Taihu Lake catchment before and after the 1920s made the lake sediments coarser, and hence heavy metals and TP content decreased contrasted with that before the 1920s. TP content in sediments and water increased from the 1950s to late 1970s due to anthropogenic pollutants discharge, and the lake belonging to mesotrophic state. TN and TOC content and C/N ratio increased due to the increasing external pollutants into Taihu Lake by human activities, TP content also increased obviously in water and sediments, and the diatom association was dominated by eutrophic species since the late 1970s, indicating the eutrophication state of Taihu Lake in this period. Meanwhile the increasing in heavy metals content, such as Cu, Mn, Ni, Pb and Zn, and their proportion of valid fractions in the sediments indicates that they all result from human pollutants since the late 1970s. The heavy metals in the surface sediments have certain potential biological toxicity due to the higher SEM/AVS ratio. 相似文献
13.
《Limnologica》2014
Human activities in Lake Fuxian and its catchment have caused environmental changes that are preserved in the geochemical records of lake sediments. Human activities responsible for the environmental changes include agriculture, mining, industrial development, and fishery management. To elucidate human impacts on this deep water body during the past several decades, two short sediment cores were collected from the lake, dated by 137Cs, and analyzed for several geochemical variables (total organic carbon (TOC), total nitrogen (TN), δ13C and heavy metals). The multi-proxy geochemical and isotopic evidence can be used to divide the limnological record into a 3-part history. Although increasing inputs of chromium (Cr) had begun as early as the 1950s, human activities, including heavy metal contamination, apparently had little effect on lacustrine production, as δ13C, TOC, TN and TOC/TN were relatively constant until the 1980s. Mining and industry have generated large amounts of heavy metal elements such as Zn, Pb and Cd that have been deposited into the lake since the 1980s, increasing to their highest concentrations over the last decades. Zn, Pb and Cd probably were released by industrial processes such as the manufacture of cement. Cr concentrations increased at site FB, but declined at site FZ, most likely due to the closer proximity of site FB to the source of metal production. From the middle of the 1980s, the decreased δ13C, and increased TOC, TN and TOC/TN suggest a broad change in lake ecology. In the 1980s, a new fish species was introduced into Lake Fuxian and fish yields increased quickly, which may mark the beginning of a change in ecosystem structure. 相似文献
14.
Environmental changes reflected by the lake sediments of the South Hongshan Lake, Northwest Tibet 总被引：6，自引：1，他引：6
The 1.07-m long lake core with 1 cm interval cutting, which was obtained by drilling in the South Hongshan Lake of Northwest Tibet, was dated by the 210Pb and 137Cs methods, and a 150-year consecutive lake sedimentary sequence (1840─1997) with 1.4 year resolution was obtained. Some environmental proxies, such as the total organic carbon (TOC), total nitrogen (TN), ratio of TOC to TN (TOC/TN), trace chemistry elements (TCE), CaCO3, grain size, richness of ostracoda etc. showed that they are of well coincidence. These results implied that the environmental background varied from the cold-wet period in the late 19th century, to the warm-wet period from the end of the 19th century to the 1920s and to the warm-dry period since the 1920s. There were sub-variations since the 1920s: the cold-dry/warm-wet fluctuation from 1922 to 1960, the intensively warm-dry period since 1960 with a short cold-wet period in the mid-1970s to the end of the 1980s. The humid period from the mid-1970s to the end of the 1970s and the dry period beginning from the early 1980s were well documented by climatic data of the nearby weather station records while the grain size was well correlated to the annual precipitation. Compared with the records from Guliya ice core in the same area, the TOC proxy in the lake core indicating warm/cold conditions well corresponded to the ( 18O records representing temperature variations in the ice core. However, the proxies with dry/wet significance in the lake core were different from the variations of snow accumulation reflected by the ice core. It can be concluded that the chosen environmental proxies have clear environmental significance and the lake sediments can reflect climatic and environmental changes at high-resolution. 相似文献
15.
Evidence from isotopic geochemistry as an indicator of eutrophication of Meiliang Bay in Lake Taihu, China 总被引：2，自引：2，他引：2
In this paper, Lake Taihu, a large shallow freshwater lake in China, is chosen as an example of reconstruction of eutrophication through the comparison between stable isotopes from dissolved nutrients and plants and water column nutrient parameters and integration of multiple proxies in a sediment core from Meiliang Bay including TN, TP, TOC, C/N,δ15N,δ13C, etc. Differences in aquatic plant species and trophic status between East Taihu Bay and Meiliang Bay are indicated by their variations inδ13C andδ15N of aquatic plants andδ15N of NH4 . A significant influence of external nutrient inputs on Meiliang Bay is reflected in temporal changes inδ15N of NH4 and hydro-environmental parameters. The synchronous change betweenδ13C andδ15N values of sedi-mented organic matter (OM) has been attributed to elevated primary production at the beginning of eutrophication between 1950 and 1990, then recent inverse correlation between them has been caused by the uptake of 15N-enriched inorganic nitrogen by phytoplankton grown under eutrophication and subsequent OM decomposition and denitrification in surface sediments, indicating that the lake has suffered from progressive eutrophication since 1990. Based on the use of a combination of stable isotopes and elemental geochemistry, the eutrophication of Meiliang Bay in Lake Taihu could be better traced. These transitions of the lake eutrophication respectively occurring in the 1950s and 1990s have been suggested as a reflection of growing impacts of human activities, which is coincident with the instrumental data. 相似文献
16.
南四湖现代沉积物中营养元素分布特征 总被引：25，自引：2，他引：23
对南四湖不同湖区20个表层沉积物和独山湖湖区沉积岩芯中营养元素进行了分析结果表明表层沉积物中南阳湖总磷最高,独山湖次之;独山湖总有机碳和总氮含量最高,南阳湖次之;而昭阳湖总有机碳、总氮和总磷含量较低.沉积岩芯中137Cs数据表明南四湖独山湖区柱状沉积物上部(0-18 cm)沉积速率为3.5mm/a;总有机碳、总氮和总磷含量主要集中在沉积岩芯0-8 cm内,并呈现一致的垂向分布规律,具有明显的三阶段分布特征,反映了流域社会经济的发展导致营养元素的释放量增加,造成了湖泊现代沉积物中营养元素的积累.碳氮比值处于7.6-11.4之间,有机质的选择性分解不明显,指示沉积物中有机质主要来自无纤维束的陆源植物.监测数据表明济宁市的城市生活污水、工农业废水排放进入南阳湖是南四湖有机质和TP富集的主要来源. 相似文献
17.
AN Zhisheng WANG Ping SHEN Ji ZHANG Yixiang ZHANG Peizhen WANG Sumin LI Xiaoqiang SUN Qianli SONG Yougui AI Li ZHANG Yechun JIANG Shaoren LIU Xingqi WANG Yong 《中国科学D辑(英文版)》2006,49(8):851-861
1 Introduction in China, with an area of 4400 km2 and a drainage area With the advancement of global change study, peo- of nearly 29,660 km2[2]. Occurring at a “climatic triple ple are paying more and more attention to the conti- junction” among the East Asian monsoon, Indian nental environment (in which we reside), its evolution Monsoon and the Westerly Jet Stream, it lies in the and its future tendency. As a component of the global transitional belt of the east monsoonal humid areas sys… 相似文献
18.
《Limnologica》2021
We measured lipid biomarkers (n-alkanes [n-ALKs] and n-alkanoic acids [n-FAs]) and other components of organic matter (total organic carbon [TOC] and total nitrogen [TN]) in a sediment core from Lake Issyk-Kul, Central Asia, to infer environmental changes in and around the lake during the last ∼300 years. Stratigraphic shifts in lipid biomarkers, TOC and TN, indicate three distinct environmental stages in the lake over the past three centuries: (1) Stage I (1670s–1790s, 51–36 cm sediment depth) corresponds to a period of stable hydrology in the lake, reflected by relatively constant concentrations of n-ALKs and n-FAs and values of related indexes. The interval was a period of relatively low trophic state. Natural factors were the main controls on environmental changes in and around the lake. (2) Stage II (1800s–1970s, 35–15 cm sediment depth) was a period when human activities began to exert influence on the environment in and around the lake. Enhanced agricultural exploitation and greater regional rainfall resulted in delivery to the lake of more land-derived lipids. Logging activity around the lake altered the vegetation, as revealed by shifts in C27/C33 ratios and the average chain length (ACL27−33). A significant decline in lake level caused by excessive water consumption impacted aquatic macrophytes, as revealed by a reduction in macrophyte indicators. Lower nutrient concentrations were inferred for this period. (3) Stage III (1980s–present, 14–0 cm sediment depth) corresponds to a period of accelerating eutrophication. Before year 2000, lake level declined steadily as a result of low rainfall (drought) and high evaporation, which exerted a strong influence on the lake condition. In addition, anthropogenic activities contributed to lake eutrophication. After 2000, the lake experienced a dramatic increase in trophic state, characterized by high algal productivity, as indicated by greater TN, short-chain n-ALKs and short-chain n-FAs. The change was probably caused by flourishing tourism around the lake. In summary, environmental changes in and around Lake Issyk-Kul during the past ∼300 years were originally driven largely by natural factors such as shifts in regional precipitation amount. Human activities (e.g. logging, agriculture, water extraction, and more recently, tourism) took on increasingly important roles during the last two centuries, affecting watershed vegetation, the lake primary producer community and lake trophic status. Changes recorded in the lake sediments over the last ∼300 years are in good agreement with historical records. 相似文献
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20.
《Marine pollution bulletin》2014,78(1-2):227-236
Total organic carbon (TOC), total nitrogen (TN), δ13C and δ15N were measured in sediment cores at three sites in Sishili Bay, China, to track the impacts of anthropogenic activities on the coastal environment over the last 100 years. The increased TOC and TN in the upper section of sediment cores indicated a eutrophic process since 1975. In comparison, the TOC and TN in the sediment core near to a scallop aquaculture area displayed a much slower increase, indicating the contribution of scallop aquaculture in mitigating eutrophication. Combined information from δ13C, δ15N and TOC:TN indicated an increased terrestrial signal, although organic matter sources in Sishili Bay featured a mixture of terrestrial and marine sources, with phytoplankton being dominant. Increased fertilizer use since 1970s contributed to the eutrophic process in Sishili Bay since 1975, and increased sewage discharge from 1990s has added to this process. 相似文献