昆明滇池沉积速率的测定   总被引：11，自引：0，他引：11  

于银亭  李培泉  吴润  孟伟  刘玉生  邹兰 《海洋与湖沼》1996,27(1):41-45

于１９８９年１２月采用＾２１０Ｐｂ法测定昆明滇池（草海和外海）两个柱样的沉积速率，其值分别为０．２９ｃｍ／ａ和０．２８ｃｍ／ａ，平均值约为０．２９ｃｍ／ａ。在沉积柱１２ｃｍ以上，由于人为影响，其沉积速率没有规律，估计约有３０－４０年的历史。在１２ｃｍ以下，＾２１０Ｐｂｅｘ随深度的变化明显地表现出规律性，以０．２９ｃｍ／ａ的速率计算，从１２ｃｍ到４０ｃｍ这一段大约有９０年的沉积历史。  相似文献   

台湾海峡中、北部浮游有孔虫同海流和沉积环境的关系   总被引：1，自引：0，他引：1  

方惠瑛 《海洋与湖沼》1995,26(5):542-551

于１９８７年７月和８月及１９８８年５月和７月，在台湾海峡中、北部海域，利用浮游生物网和蚌式采泥器分别采集了水层中的浮游有孔虫标本和表层沉积里的浮游有孔虫遗壳样品。对活体和遗壳在数量和组成方面对比分析研究表明，调查海区暖水性最强的水域位于东南角的Ａ５站一带，海峡暖流水由此向北延伸，在海坛岛以东Ｄ１站附近，因与闽浙沿岸水交汇而减弱。遗壳高值区位于深水的盆地，活体则出现在台地上，两者分布不一致。其原因在  相似文献   

Application of a Biological Tool for Estimating Current Annual Rates of Erosion and Deposition in Modern Coastal Environments: A Case Study in the Bay of Bengal Coast     

Chirananda De 《Marine Georesources & Geotechnology》2002,20(3):209-220

The marine polychaete Diopatra cuprea (Bosc) produces tubes that protrude above the sediment surface. To the part above the sediment surface the worm attaches foreign particles. A sharp boundary separates the parts above and below the sediment surface. With subsequent erosion, part of the tube without attached particles becomes exposed and this exposed part indicates the amount of erosion. With subsequent sedimentation, the tubes are enlarged upward and the sharp boundary is found below the sediment surface indicating the amount of subsequent sedimentation. This mode of construction of tubes during an average life span of two years renders tubes as simple but excellent natural tools for precise and easy measurement of the latest annual rates of erosion and deposition in coastal areas, data that are essential for the solving of coastal engineering and geoenvironmental problems. Comparison of this tool with expensive long-term coastal profiling data in four areas in the Bay of Bengal coast indicates its correctness and high applicational value.

This revised model can be applied to modern coastal environments only for calculating latest annual rates of both erosion and deposition as correctly as latest physical techniques. Being based on the similar organosedimentary principle, it distinctively contrasts with the earlier model of Myers which provides information on the amount of sediment accumulation only without any time connotation and, it may generate erroneous results if applied to the geologic past unless some limitations evolved in the processes of dewatering, compaction, lithification and diagenesis are removed.  相似文献   

早更新世以来南海中部的沉积作用   总被引：1，自引：0，他引：1  

何良彪 《海洋地质与第四纪地质》1991,(4)

本文根据7个岩心的粒度、矿物、化学、微体古生物、氧同位素和古地磁等分析和测试资料,探讨了南海中部早更新以来沉积作用特征及其演化。自早更新世以来,研究区主要处在一种半深海的较为稳定的沉积环境,沉积了一套以陆源碎屑为主要成分,并含有较丰富的生物碎屑和火山碎屑的具有多源性特征的粘土质粉砂和粉砂质粘土沉积。但是在漫长的沉积过程中,受到区域地质构造运动、海底火山活动和全球性古气候变化的影响,使其在不同沉积区和不同沉积历史时期的沉积特征具有明显差异。  相似文献   

Deep western boundary current dynamics and associated sedimentation on the Eirik Drift, Southern Greenland Margin     

Sally Hunter  David Wilkinson  Essyllt Louarn  I. Nick McCave  Eelco Rohling  Dorrik A.V. Stow  Sheldon Bacon 《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(12):2036-2066

Growing interest in the dynamics and temporal variability of the deep western boundary current (DWBC) in the northern North Atlantic has led to numerous studies of the modern hydrography and palaeoceanography of this current system. The DWBC is fed by the two dense water-masses that spill over the Greenland–Iceland–Scotland Ridge; Denmark Strait Overflow Water (DSOW) and Iceland Scotland Overflow Water (ISOW). These overflows entrain ambient water masses, primarily Labrador Sea Water (LSW), as they cross the Iceland and Irminger Basins before merging in the vicinity of south-east Greenland. A number of studies have been performed around the Eirik Drift, located off the southern Greenland margin, downstream of this main merging point. However, the relationship between the DWBC and the associated sedimentation at this location has yet to be fully elucidated. New hydrographic data show that the current's main sediment load is carried by only one of its components, the DSOW. Seismic surveys and sediment cores confirm that Holocene sedimentation is limited to areas underlying the most offshore part of the current, where the hydrographic data show the highest concentration of DSOW. Active sedimentation through the Holocene therefore appears to have been controlled by proximity to the sediment-laden DSOW.Our interpretation of new and historic geostrophic transport and tracer data from transects around the southern Greenland margin also suggests that the DWBC undergoes significant growth through entrainment as it flows around the Eirik Drift. We attribute this to multiple strands of ISOW following different depth-dependent pathways between exiting the Charlie Gibbs Fracture Zone and joining the DWBC. Comparison of our new data with other modern hydrographic datasets reveals significant temporal variability in the DWBC, associated with variations in the position, structure and age since ventilation of the current in the vicinity of Eirik Drift. The complexity of the current dynamics in this area has implications for the interpretation of hydrographic and palaeoceanographic data.  相似文献   

Using a GIS to Examine Changes in the Bathymetry of Borrow Pits and in Lower Bay, New York Harbor, USA   总被引：1，自引：0，他引：1  

Pace Wilber  Linda E. Iocco 《Marine Geodesy》2003,26(1):49-61

Standard analyses with geographic information systems (GIS) and the publicly available GEODAS database were used to highlight bathymetric changes in the Lower Bay complex of New York Harbor. Dredging operations have deepened much of the Lower Bay complex. Approximately 6,580 hectares, or 20% of the bay bottom surveyed in 1934, was deeper in 1979/1982 than during 1934. Half of this deepening, 3,219 hectares or 10% of the bay bottom surveyed during 1934, was deeper by at least 2 m. Surveys conducted by the U.S. Army Corps of Engineers of three borrow pits in the central part of the Lower Bay complex were used to examine sedimentation over a 16-year period from 1979 to 1995. Results were consistent with studies conducted during the 1970s and 1980s that show the pits function as sediment traps. Between 1979 and 1995, sediment accumulated at rates of 6 to 12 cm per year in many portions of the borrow pits.  相似文献   

Use of MODIS satellite images for detailed lake morphometry: Application to basins with large water level fluctuations     

《International Journal of Applied Earth Observation and Geoinformation》2016

Lake morphometry is essential for managing water resources and limnetic ecosystems. For reservoirs that receive high sediment loads, frequent morphometric mapping is necessary to define both the effective life of the reservoir and its water storage capacity for irrigation, power generation, flood control and domestic water supply. The current study presents a methodology for updating the digital depth model (DDM) of lakes and reservoirs with wide intra and interannual fluctuations of water levels using satellite remote sensing. A time series of Terra MODIS satellite images was used to map shorelines formed during the annual water level change cycle, and were validated with concurrent Landsat ETM+ satellite images. The shorelines were connected with in-situ observation of water levels and were treated as elevation contours to produce the DDM using spatial interpolation. The accuracy of the digitized shorelines is within the mapping accuracy of the satellite images, while the resulting DDM is validated using in-situ elevation measurements. Two versions of the DDM were produced to assess the influence of seasonal water fluctuation. Finally, the methodology was applied to Lake Kerkini (Greece) to produce an updated DDM, which was compared with the last available bathymetric survey (1991) and revealed changes in sediment distribution within the lake.  相似文献   

Heartbeat of a mountain: diagnosing the age of depositional events in the Karoo (Gondwana) Basin from the pulse of the Cape Orogen     

J. P. le Roux 《International Journal of Earth Sciences》1995,84(3):626-635

Careful consideration of the effects of the Cape orogeny on sedimentation in the Carboniferous-Jurassic Karoo Basin provides an indirect tool for accurately dating these rocks. Fossil and radiometric data, especially when combined with sedimentological and structural information, yield partly overlapping age brackets which can be used to correlate the successive tectonic pulses with specific depositional events. Application of these principles to associated basins in Gondwanaland can provide a firm foundation for more dependable stratigraphic correlation on a global scale. The exercise also suggests that a number of widely held opinions on the age of certain stratigraphic units in the Karoo Supergroup may be incorrect.  相似文献   

Three-dimensional numerical modeling of Late Quaternary paleoceanography and sedimentation in the northern North Atlantic     

B. J. Haupt  C. Schäfer-Neth  K. Stattegger 《International Journal of Earth Sciences》1995,84(1):137-150

Modelling of Late Quaternary paleoceanography and sedimentation in the northern North Atlantic (NNA) is achieved by coupling the ocean general circulation model SCINNA (Sensitivity and Circulation In the NNA) to the sedimentation models SENNA (Sedimentation In the NNA) and PATRINNA (PArticle Tracing In the NNA).SCINNA is based on the primitive equations with conservation of mass, momentum, energy, heat and salt. SENNA and PATRINNA are driven by temperature, salinity and velocity fields derived from SCINNA. The modelling includes three-dimensional circulation of the ocean, sediment transport in the water column and two-dimensional sedimentary processes in a thin bottom layer. SENNA calculates the erosion, transport and deposition of sediments, resulting in sedimentation patterns for specific time intervals. PATRINNA models the transport paths of single sediment grains corresponding to the ocean circulation.The NNA reacts in a highly sensitive manner to small forcing changes, as shown by our sensitivity experiments. From these experiments it is possible to model specific circulation regimes for glacial and interglacial periods, for melt water events and for the onset of glaciation. The different climatic stages in the circulation model produce different sediment patterns in the sedimentation models, which correspond closely to the sedimentary record.  相似文献   

Sedimentation within a regulated river     

Geoffrey E. Petts 《地球表面变化过程与地形》1984,9(2):125-134

Channel change induced by tributary sediment injection to a regulated, gravel-bed river is described for the River Rheidol, U.K., eighteen years after dam closure. Morphological and sedimentological data are presented for an aggrading reach. A primary lobate bar appears to have initiated flow separation and the subsequent construction of channel-side berms. Hydraulic sorting has operated to produce both longitudinal and lateral particle-size reduction, and selective particle-size dispersal appears to be an important process influencing channel change. The channel is adjusting to a lower width-depth ratio form, of smaller capacity, and with a steeper slope.  相似文献