冲绳海槽中段表层沉积物中稀土元素组成及其物源指示意义   总被引：7，自引：0，他引：7  

刘娜  孟宪伟 《海洋地质与第四纪地质》2004,24(4):37-43

冲绳海槽中段表层沉积物主要是由陆源、火山源和生物源物质按不同比例组成的混合物。研究表明,陆源物质(长江和黄河沉积物)稀土总量最高,轻稀土明显比重稀土富集;火山物质(冲绳海槽火山玻璃)具有较明显的正Eu异常且重稀土相对富集;生物源物质(冲绳海槽有孔虫壳)中稀土富集。3种端员物质的稀土元素组成特征存在显著差异,因此,选择合适的稀土元素特征参数——∑LREE／∑HREE、Eu／Sm及MREE／(LREE HREE)可以分别刻画出冲绳海槽沉积物中陆源、火山源及生物源物质的组成特征。通过与前人对研究区物源定性、定量分区的结果对比,验证了利用稀土元素特征参数刻画冲绳海槽混合沉积物物质来源组成的有效性。  相似文献   

广西钦州湾晚全新世红树林演变及对海平面变化的响应   总被引：2，自引：0，他引：2  

夏鹏  孟宪伟  李珍  支鹏遥  赵蒙维  王恩康 《海洋学报(英文版)》2019,38(11):111-120

Mangroves, widely distributed along the coasts of tropical China, are influenced by Asia monsoon, relative sea level change and enhanced human activity. To predict the impacts of future climate change on mangrove ecosystems, it can be understood by reconstructing past mangrove dynamics using proxies preserved in coastal sediments. In this study, we quantitatively partitioned buried organic matter(OM) sources, collected from a vulnerable mangrove swamp in the Qinzhou Bay of northwestern South China Sea, using a ternary end-member mixing model of δ~(13)C and C:N values. Mangrove-derived OM(MOM) contribution was used as a tracer for mangrove development since 2.34 cal ka BP. This information, together with paleoclimate records(i.e.,speleothem δ~(18)O values, sea level change, grain size parameters) and human activity, was used to divide mangrove development into three stages during the late Holocene: relative flourish(2.34–1.13 cal ka BP), relative degradation(1.13–0.15 cal ka BP) and further degradation(0.15–0 cal ka BP). Before 1.13 cal ka BP, mangroves flourished with a high MOM contribution((88.9±10.6)%), corresponding to stable and high sea level under a warm and humid climate. After 1.13 cal ka BP, rapid fall in relative sea level coupled with the strengthening of the Asian winter monsoon, resulted in mangrove degradation and MOM reduction((62.4±18.9)%). Compared with air temperature and precipitation, the relative sea level fall was the main controlling factor in mangrove development before entering the Anthropocene(the time of the Industrial Revolution). After ～150 cal a BP, reclamation of mangrove swamps to shrimp ponds is the main factor causing mangrove degradation and MOM reduction.  相似文献   

中国西南广西英罗湾红树林近130年来演化指标——沉积物中的红树叶片亚化石     

王万祝  孟宪伟  王湘芹  李珍 《海洋学报(英文版)》2019,38(8):27-34

Located in the intertidal zone of the tropical and subtropical coasts, mangrove forests are an important ecosystem in the global carbon cycle and serve as a protector of local seashores. Under the double impacts of climate change,especially sea-level rise, and human activity, mangrove forests around the world have faced degradation, against which the reconstruction of the historical development of mangrove forests using an effective indicator has been regarded as a necessary strategy for designing a predictable model. As the primary product of mangrove forest, it is reasonable that the content of leaf fragments of mangrove(CLFM) buried in sediments in the form of sub-fossils potentially has the same indicative function for the development of mangrove forests as that of widely-used mangrove pollen. In this study, the leaf fragments of mangrove in two sediment cores(YLW02 and YLW03) drilled in the Yingluo Bay in Guangxi, Southwest China were picked out and weighted for calculation of CLFM, which was used as an indicator of mangrove development after examination of parallelism and a statistical correlation of the CLFM with the concentration of mangrove pollen. The results clearly show that the vertical distribution of the CLFM for the core taken from the landward margin of mangrove forests(YLW03) only parallels that of the local mangrove species(Rhizophora. stylosa) with a significantly positive correlation(R=0.56, P=0.05), while the vertical distribution of the CLFM for the core taken from the interface between seaward margin of mangrove forest and the trunk of tidal creeks of the bay(YLW02) parallels the summed concentration of mangrove pollen(SCMP) with a more positive correlation than that of YLW03(R=0.85, P=0.01), indicating that the trunk outlet of tidal creeks must have been the site where mangrove production gathered from the overall forest rather than from local production. The variations in the CLFM of both cores indicate that overall the mangrove forests in the Yingluo Bay have increasingly flourished over the last 130 years except for the interval of 1940–1950 AD in response to an increase in air temperature and decrease in rainfall, which would have resulted in an increase in seawater salinity;while the coupled extreme increases in air temperature and in rainfall in summer, which would have resulted in extreme decreases in seawater salinity, would be responsible for the relative degradation of mangrove forests in the interval of 1940–1950 AD.  相似文献   

黑龙江团结沟金矿外围1：5万金矿地球化学异常的圈定与筛选     

孟宪伟 《有色金属矿产与勘查》1993,2(5):298-303

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全新世大暖气广西钦州湾红树林衰退的红树林源有机质贡献示踪及其对亚洲季风的响应     

孟宪伟  夏鹏  李珍  刘乐军 《海洋学报(英文版)》2016,35(2):95-100

The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum(HCO), using proxies preserved in coastal sediments. The total organic matter in sediments of a segmented core, with calibrated age ranges between 5.6 and 7.7 cal. ka BP and corresponding to the HCO, from the Qinzhou Bay in Guangxi, China, is quantitatively partitioned into three end-members according to their sources: mangrove-derived, terrigenous,and marine phytoplanktonic, using a three-end-member model depicted by organic carbon isotope(δ13Corg) and the molar ratio of total organic carbon to total nitrogen(C/N). The percentage of mangrove-derived organic matter(MOM) contribution is used as a proxy for mangrove development. Three visible drops in MOM contribution occurred at ca. 7.3, ca. 6.9, and ca. 6.2 cal. ka BP, respectively, are recognized against a relatively stable and higher MOM contribution level, indicating that three distinct mangrove forest degradations occurred in the Qinzhou Bay during the HCO. The three mangrove forest degradations approximately correspond to the time of the strengthened/weakened Asian winter/summer monsoon. This indicates that even during a period favorable for the mangrove development, such as the HCO, climatic extremes, such as cold and dry events driven by the strengthened/weakened Asian winter/summer monsoon, can trigger the degradation of mangrove forests.  相似文献   

晚第四纪南海北部陆坡沉积物常量元素比值对气候变冷事件的指示意义   总被引：2，自引：1，他引：1  

张俊  孟宪伟  王湘芹 《海洋学报》2013,35(4):106-111

南海北部陆坡柱状沉积物的常量元素统计分析表明, 沉积物中的Ti、Al、Fe、K、Mn、Mg代表了陆源元素组合;而消除粒度效应的陆源元素比值Al/Ti、Fe/Ti和K/Ti等的变化曲线与浮游有孔虫氧同位素曲线对比表明, 在气候变冷事件(Heinrich事件、Younger Dryas事件、PME斜室普林虫低值等事件)期间, 陆源常量元素比值明显降低。这一对应特征, 一方面体现了气候变冷事件的发生对陆源区化学风化强度的制约, 另一方面也说明与指示长时间尺度气候相似, 陆源元素比值对短时间尺度的气候变化也具有明显的指示作用。  相似文献   

冲绳海槽中段沉积地球化学分区及其物源指示意义   总被引：15，自引：1，他引：15  

孟宪伟  王永吉 《海洋地质与第四纪地质》1997,17(3):37-43

通过对冲绳海槽中段表层沉积物５１个样品的３０个元素的地球数据的Ｒ型因子分析计算，确定了以８个因子为代表的元素组合，在综合、对比因子得分的基础上，把研究区分为１０个组合区。根据元素组合的成因专属性，把研究区分为火山源区，热液源区，陆泊、生物源和自生源区。  相似文献   

太平洋CC区多金属结核Ce同位素组成——幔源Ce证据   总被引：3，自引：0，他引：3  

孟宪伟  刘娜  韩贻兵 《海洋学研究》2003,21(1):13-18

利用对太平洋多金属结核资源调查取得的多金属结核样品,对太平洋CC区多金属结核的Ce同位素组成特征进行了研究,结果表明:太平洋CC区多金属结核的Ce同位素组成.138Ce/.142Ce较低,εCe为负值,与大西洋多金属结核的同位素组成正好相反,但与洋中脊玄武岩(MORB)和太平洋0～500 m上层海水的Ce同位素组成相似.Ce、Nd的单一源模式和Ce-Nd同位素体系模式都不能解释太平洋多金属结核的这种负εCe和εNd特征,表明太平洋CC区多金属结核中的Ce、Nd可能具有不同的来源,前者来源于地幔,后者来源于大陆,幔源Ce的光致还原作用是太平洋CC区多金属结核中负εCe形成的又一因素.  相似文献   

海底天然气水合物资源预测技术     

孟宪伟  杜德文 《海洋地质》2001,(2):7-8

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黄海沉积物地球化学的粒度效应   总被引：15，自引：0，他引：15  

杜德文  石学法  孟宪伟  程振波  陈志华  熊应乾 《海洋科学进展》2003,21(1):78-82

分析了最近在南黄海获取的283个站位的表面沉积物样品，获取了粒度、元素含量等多项指标。对粒级含量、元素含量做了相关分析，得出如下结论：并非所有元素分布都受沉积物粒度控制；具有粒度效应的元素不受所有粒级控制；元素含量与各粒级的含量呈“＼”、“／”、“N”、反“N”4种关系。这些发现对剔除元素分布的粒度效应，为利用元素分布来识别沉积物物源提供了基础性认识。  相似文献