Benthic foraminiferal distribution in surface sediments along continental slope of the southern Okinawa Trough: dependance on water masses and food supply     

Xiang Rong  Li Tiegang  Yang Zuosheng  Yan Jun  Cao Qiyuan 《海洋学报(英文版)》2003,22(1):133-143

Benthic foraminiferal analysis of 29 samples in surface sediments from the southern Okinawa Trough is carried out.The results indicate that benthic foraminiferal abundance decreases rapidly with increasing water depth.Percentage frequencies of agglutinated foraminifera further confirm the modern shallow carbonate lysocline in the southern Okinawa Trough.From continental shelf edge to the bottom of Okinawa Trough,benthic foraminiferal fauna in the surface sediments can be divided into 5 assemblages:(1) Continental shelf break assemblage,dominated by Cibicides pseudoungerianus,corresponds to subsurface water mass of the Kuroshio Current;(2) upper continental slope assemblage,dominated by Cassidulina carinata,Globocassidulina subglobosa,corresponds to intermediate water mass of the Kuroshio Current;(3) intermediate continental slope assemblage,dominated by Uvigerina hispida,corresponds to the Okinawa Trough deep water mass above the carbonate lysocline.  相似文献   

Significance of carbon isotopes in carbonate sequence stratigraphy     

Qing Jianxiong  Zeng Yunfu  Chen Hongde  Tian Jingchun  Yang Zuosheng 《中国地球化学学报》1999,18(1):69-79

Based on the research on sequence stratigraphy of the Permian in Southwest China, in conjunction with the carbon isotope data from the typical sections at Ganluo, Sichuan and Tianlin and Mashan, Guangxi, the authors suggest that the genetic framework and internal architicture of different sequences possess quite different carbon isotopic characteristics. Therefore, the following problems can be solved in terms of carbon isotopic values, evolutionary curve patterns and structures of carbonate sequences: (1) to determe the nature of sequence boundary surface and related geological events; (2) to recognize various kinds of sedimentary system tracts; (3) to discuss the internal architicture and genetic framework of the sequences and their evolution; (4) to subdivide and correlate sedimentary sequences on a regional or global scale; and (5) to enhance the resolution of sequence stratigraphic analysis. Stable carbon isotopes have proved themselves to be valid in sequence stratigraphic studies of carbonate rocks, as demonstrated by our results presented in this paper.  相似文献   

长江口泥质区的季节性沉积效应   总被引：1，自引：0，他引：1  

郭志刚  杨作升  范德江  PAN Yanjun 《地理学报(英文版)》2003,13(3):348-354

1IntroductionThe continental shelf of the East China Sea (ECS) is one of the widest shelves in the world. There are several mud areas distributing like patches on a background of widespread coarser ambient sediments of silt and sand on the continental shelf of the ECS. The coastal mud area can be divided into two parts, namely, the Changjiang Estuary mud area (CEMA) in the north and Zhejiang coastal mud area in the south. Between these two parts there is a silt area (Figure 1). The CE…  相似文献   

印度洋钙质软泥和硅质软泥稀土元素组成和富集机制     

刘明  孙晓霞  石学法  张文强  范德江  杨作升 《海洋学报》2019,41(1):58-71

本文针对采自印度洋深海中最常见的两类生物成因沉积物——钙质软泥和硅质软泥，开展了全岩样和不同粒级组分中常微量元素、稀土元素和Y（REY）含量的系统分析，探讨了两类沉积物中REY的组成特征、物质来源和富集机制。研究表明，钙质软泥以富含CaO和Sr为主要特征，硅质软泥则富集SiO₂、Al₂O₃、Fe₂O₃等。钙质软泥中∑REY平均含量为40.56×10-6，轻稀土元素（LREE）略有富集，REY有向细粒沉积物中富集的特征，PAAS标准化后全岩样和不同粒级组分均表现为Ce负异常、Eu和Y正异常；REY以自生来源为主，继承了海水的组成特征，同时也受到了热液流体物质和洋底玄武岩风化产物的影响。硅质软泥中∑REY的含量为248.54×10-6，LREE相对富集，REY在4φ以细的沉积物中富集；研究站位沉积物中∑REY含量处于边界品位附近，但在细粒级沉积物中重稀土元素（HREY）含量则达到了工业品位；该类沉积物细粒组分中REY主要来自陆源或火山碎屑组分中黏土矿物和铁锰氧化物吸附作用，粗粒组分中REY来源则主要与生物作用相关；硅质软泥中REY的富集与沉积物中磷灰石等矿物相关，部分不同来源的REY可能是在沉积之后的成岩过程中再次分配向磷灰石、钙十字沸石等矿物中富集。  相似文献   

Sustained growth of the largest uninhabited alluvial island in the Changjiang Estuary under the drastic reduction of river discharged sediment     

Zhang  Xiaodong  Xie  Rui  Fan  Daidu  Yang  Zuosheng  Wang  Hongmin  Wu  Chuang  Yao  Yuhan 《中国科学:地球科学(英文版)》2021,64(10):1687-1697

The evolution of the Changjiang Delta is obviously affected by current rapidly rising sea level and drastically declining river discharge, and it is also vital for the sustainable development of Shanghai and the Changjiang River Economic Belt, which represent China's economic development leader and major national strategic area, respectively. In this paper, the growth pattern of Jiuduansha Island, the largest uninhabited alluvial island in the Changjiang Estuary, is studied in terms of the change in elevation, position and area over the past 50 years through using satellite-derived instantaneous shoreline positions and high/low tide exposure areas based on 497 satellite images from 1974 to 2020; and the influencing factors and future development patterns are further discussed by comparison with other alluvial islands or sandbars in the estuary. The results show that Jiuduansha Island has maintained a rapid or even accelerated area growth rate, although the sediment discharge of the Changjiang River has sharply decreased in recent decades. This sustained growth is mainly attributed to the existence of the estuarine turbidity maximum zone, coarsening fluvial sediment, onshore sediment replenishment by tide, cone-like geomorphology of Jiuduansha Island, and siltation promotion effect of vegetation. The growth rate of the low tide exposure area of Jiuduansha Island increased from 1.9 km~2 a~(-1) in 1974–1990 to 3.0 km~2 a~(-1) in 1990–2020, and the growth rate of the high tide exposure area reached as high as 3.7 km~2 a~(-1) in 1994–2020. The implementation of the Deep-Water Channel Project has significantly affected the evolution of Jiuduansha Island, including shifting the heads of Shangsha and Zhongxiasha from severe retreat to rapid accretion, and promoting tidal flat progradation seaward of the Jiangyanansha and Zhongxiasha, but restricting the growth of the low tide exposure area of Jiuduansha Island.  相似文献   

Major mid-late Holocene cooling in the East China Sea revealed by an alkenone sea surface temperature record     

Meixun Zhao  Ling Ding  Lei Xing  Shuqing Qiao  Zuosheng Yang 《中国海洋大学学报(英文版)》2014,13(6):935-940

Although the mid-late Holocene cold and dry event about 4000 years ago(the 4 ka event) has been observed almost globally, it was most prominent in terrestrial climate proxies from the lower latitudes. Here we evaluate the oceanic response to this event in terms of a Holocene sea surface temperature(SST) record reconstructed using the K'37U index for Core B3 on the continental shelf of the East China Sea. The record reveals a large temperature drop of about 5℃ from the mid-Holocene(24.7℃ at 5.6 ka) to the 4 ka event(19.2℃ at 3.8 ka). This mid-late Holocene cooling period in Core B3 correlated with(i) decreases in the East Asia summer monsoon intensity and(ii) the transition period with increased El Nino/Southern Oscillation activities in the Equatorial Pacific. Our SST record provides oceanic evidence for a more global nature of the mid-late Holocene climate change, which was most likely caused by a southward migration of the Intertropical Converge Zone in response to the decreasing summer solar insolation in the Northern Hemisphere. However, the large SST drop around Core B3 indicates that the mid-late Holocene cooling was regionally amplified by the initiation/strengthening of eddy circulation/cold front which caused upwelling and resulted in additional SST decrease. Upwelling during the mid-late Holocene also enhanced with surface productivity in the East China Sea as reflected by higher alkenone content around Core B3.  相似文献   

Crystals of suspended marine barite in the eastern equatorial Pacific: processes of dissolution and effects on crystal morphology     

孙晓霞  杨作升  范德江  李云海 《中国海洋湖沼学报》2015,33(1):194-203

Suspended paniculate substances were sampled in the eastern equatorial Pacific in water column from surface to near bottom in five stations in 2005,from which 868 barite crystals were recovered.The barite crystals were examined under scanning electron microscopy.About 61%of the total barites crystals contained detectable Sr by energy dispersive X-ray spectrometry.Barite crystals could be classified into four groups based on their morphology:1) bladed;2) ovoid or rounded;3) arrow-like;and 4) irregularly shaped.The arrow-like barite crystals in natural environment has never been reported before.In addition,about a half of the studied crystals showed features of dissolution as cavities or holes inside of the crystals or around their edges.We found that differential dissolution of barite crystals is consequence of heterogeneous Sr distribution in barite crystals.Our results would help in understanding the biogeochemical processes of marine barite formation and preservation in seawater and marine sediments.  相似文献   

East Asia Winter Monsoon changes inferred from environmentally sensitive grain-size component records during the last 2300 years in mud area southwest off Cheju Island,ECS   总被引：5，自引：0，他引：5  

Yoshiki Saito 《中国科学D辑(英文版)》2006,49(6):604-614

The last 2000 years are an important time span both for IGBP-PAGES and CLIVAR of WCRP. One of the main aims of these projects is to obtain high-resolution records of global change, such as that stored in ice cores, tree rings, speleothems, corals, lakes, marine records, etc., and then use these data to make sound estimates for future global change. To accomplish these projects, we first need to obtain high-resolution geological records and proxies for climatic/environ- mental changes. …  相似文献   

Formation and kinetics of porous cordierite from fly ash     

Xuebin Zhang  Zuosheng Wu  Guangyao Meng  Xingqin Liu 《中国地球化学学报》2008,27(4):395-400

Porous cordierite ceramics were prepared from a mixture of coal fly ash and basic magnesium carbonate at 1100-1350℃. Porosity, flexural strength and thermal expansion coefficient of the samples sintered at 1300℃ were estimated to be 26%, 65 MPa and 4.21×10^-6/℃, respectively. The kinetics of the formation progress was investigated by stepwise isothermal dilatometry （SID） accompanied with XRD, SEM and porosity measurement. It was found that the isothermal shrinkage data from SID could be well analyzed to get kinetic parameters according to the erapirical rate equation developed by Makipirtti-Meng, dY/dt=nk（T）Y（1-Y）（Y/1-Y）^（1/n）,where Y is the fractional shrinkage during the sintering process and n is a dimensionless component. The apparent activation energy △E values for 900-1000℃ and 1050-1 150℃ were 1294 and 1778 kJ/mol, respectively.  相似文献   

利用MAPX实现空间数据库与属性数据库的挂接   总被引：3，自引：0，他引：3  

张勇  杨作升  刘展  周晓霞 《中国海洋大学学报(自然科学版)》2003,33(1):87-94

数据库是 GIS的基础 ,而空间数据库与属性数据库的挂接则是 GIS的要点。本文以渤海区域地质信息管理系统数据为例 ,阐述了基于 GIS的海洋地学管理信息系统中数据库的组织方法 ,包括空间数据库与属性数据库数据分类、分层方案 ,命名及编码规则。在此基础上 ,重点讨论了在 VisualBasic环境下运用 MAPX实现空间数据库与属性数据库的挂接方法。  相似文献