Seven cores were collected from different sediment zones of tidal flats at Xin- yanggang in north Jiangsu province in August 2007. Sediment grain-size distribution and radioisotopes of ^137Cs and ^210Ppb analysis were...Seven cores were collected from different sediment zones of tidal flats at Xin- yanggang in north Jiangsu province in August 2007. Sediment grain-size distribution and radioisotopes of ^137Cs and ^210Ppb analysis were carried out for these cores. Sediment rates of the cores and radioisotopes distribution in surface sediment in different zones of the tidal flat were calculated from the ^137Cs and ^210Ppb activities in sediments cores. The results indicated that each tidal zone had experienced different evolution phases, hydrological dynamics in the tidal flats made the grain-size of the surface sediment change gradually. ^137Cs and ^210Ppb activities on the superficial layer of the cores varied spatially and the reason was discussed. On tidal flats, the fluctuation of ^137Cs and ^210Ppb activities in the cores reflected the special sedimentary characteristics. Vegetation affects the grain-size distribution and the vertical profiles of ^137Cs and ^210Ppb in the upper depths. ^137Cs and ^210Ppb chronology got the comparable average sediment rates on the tidal flat. The characteristics of ^137Cs and ^210Ppb in the cores reflected various depositional dynamical environments in different tidal zones and gave information on the different evolvement phases of the tidal zones. Based on the information of grain-size distribution, texture of the cores, sediment rates and topography, the evolution lines of the tidal flat were reconstructed.展开更多
A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above...A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above the seabed. Based upon the logarithmic-profile equation, the boundary layer parameters, i.e., u, z0 and C60, were obtained for 247 tidal flow velocity profiles. Around 90% of the profiles were logarithmic according to the critical correlation coefficient. Internal consistency analysis shows that these parameters derived by different methods are consistent with each other. In addition, the height of the bedforms observed is close to the seabed roughness lengths calculated from the velocity profiles, indicating that the boundary layer parameters obtained can reveal the conditions at the sediment-water interface on the intertidal flats. Suspended sediment concentrations were obtained from the 5 CTMS turbidity meters using laboratory and in-situ calibrations. The results show that the in-situ calibrated SSCs have a much higher accuracy than the laboratory calibrated ones. Calculation of suspended sediment fluxes on the intertidal flats, with a magnitude of 104 kg/m per spring tidal cycle, indicates that suspended sediment moves towards the northwest, which is reversal to the transport pattern controlled by the southward Northern Jiangsu Coastal Current in the sub-tidal zone and adjacent shallow waters.展开更多
对杭州湾北岸3处现代潮滩沉积物进行高精度粒度分析,查找研究区潮滩不同微相的粒度特征和差异,提取基于粒度分析的潮滩微相识别敏感指标,并将其应用到该区域的全新世钻孔潮滩沉积物中,识别钻孔潮滩沉积微相,据此建立研究区全新世早期的...对杭州湾北岸3处现代潮滩沉积物进行高精度粒度分析,查找研究区潮滩不同微相的粒度特征和差异,提取基于粒度分析的潮滩微相识别敏感指标,并将其应用到该区域的全新世钻孔潮滩沉积物中,识别钻孔潮滩沉积微相,据此建立研究区全新世早期的海平面曲线。研究表明:杭州湾北岸现代高潮滩盐沼沉积物粘土含量明显高于高潮滩下部和中潮滩,而砂含量与之相反;高潮滩盐沼平均粒径等粒度参数明显小于中、高潮滩的粒度参数;盐沼沉积物粒度频率曲线峰态宽缓,明显区别于高潮滩下部和中潮滩。上述现代潮滩微相粒度敏感指标可成功应用到钻孔潮滩沉积微相划分中,并建立了该区域全新世早期海平面曲线。曲线显示,9700~8700 cal a BP期间海平面上升约11.6 m,海平面上升速率可达1.2 cm/a。现代潮滩不同位置沉积物粒度参数的规律性差异可作为潮滩微相识别的有效指标,为古潮滩沉积微相识别和古海平面重建提供参考依据。展开更多
基金National Basic Research Program of China, No.2002CB412401 Scientific Research Foundation of Graduate School of Nanjing University National Natural Science Foundation of China, No.40776023
文摘Seven cores were collected from different sediment zones of tidal flats at Xin- yanggang in north Jiangsu province in August 2007. Sediment grain-size distribution and radioisotopes of ^137Cs and ^210Ppb analysis were carried out for these cores. Sediment rates of the cores and radioisotopes distribution in surface sediment in different zones of the tidal flat were calculated from the ^137Cs and ^210Ppb activities in sediments cores. The results indicated that each tidal zone had experienced different evolution phases, hydrological dynamics in the tidal flats made the grain-size of the surface sediment change gradually. ^137Cs and ^210Ppb activities on the superficial layer of the cores varied spatially and the reason was discussed. On tidal flats, the fluctuation of ^137Cs and ^210Ppb activities in the cores reflected the special sedimentary characteristics. Vegetation affects the grain-size distribution and the vertical profiles of ^137Cs and ^210Ppb in the upper depths. ^137Cs and ^210Ppb chronology got the comparable average sediment rates on the tidal flat. The characteristics of ^137Cs and ^210Ppb in the cores reflected various depositional dynamical environments in different tidal zones and gave information on the different evolvement phases of the tidal zones. Based on the information of grain-size distribution, texture of the cores, sediment rates and topography, the evolution lines of the tidal flat were reconstructed.
文摘A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above the seabed. Based upon the logarithmic-profile equation, the boundary layer parameters, i.e., u, z0 and C60, were obtained for 247 tidal flow velocity profiles. Around 90% of the profiles were logarithmic according to the critical correlation coefficient. Internal consistency analysis shows that these parameters derived by different methods are consistent with each other. In addition, the height of the bedforms observed is close to the seabed roughness lengths calculated from the velocity profiles, indicating that the boundary layer parameters obtained can reveal the conditions at the sediment-water interface on the intertidal flats. Suspended sediment concentrations were obtained from the 5 CTMS turbidity meters using laboratory and in-situ calibrations. The results show that the in-situ calibrated SSCs have a much higher accuracy than the laboratory calibrated ones. Calculation of suspended sediment fluxes on the intertidal flats, with a magnitude of 104 kg/m per spring tidal cycle, indicates that suspended sediment moves towards the northwest, which is reversal to the transport pattern controlled by the southward Northern Jiangsu Coastal Current in the sub-tidal zone and adjacent shallow waters.
基金国家自然科学基金项目《杭州湾北岸全新世早期(10-9 cal ka BP)高精度海平面重建及沉积环境响应》(批准号:41706098)《基于微体化石识别全新世高海面阶段长江口外水团相互作用及调控机制》(批准号:42076081)。
文摘对杭州湾北岸3处现代潮滩沉积物进行高精度粒度分析,查找研究区潮滩不同微相的粒度特征和差异,提取基于粒度分析的潮滩微相识别敏感指标,并将其应用到该区域的全新世钻孔潮滩沉积物中,识别钻孔潮滩沉积微相,据此建立研究区全新世早期的海平面曲线。研究表明:杭州湾北岸现代高潮滩盐沼沉积物粘土含量明显高于高潮滩下部和中潮滩,而砂含量与之相反;高潮滩盐沼平均粒径等粒度参数明显小于中、高潮滩的粒度参数;盐沼沉积物粒度频率曲线峰态宽缓,明显区别于高潮滩下部和中潮滩。上述现代潮滩微相粒度敏感指标可成功应用到钻孔潮滩沉积微相划分中,并建立了该区域全新世早期海平面曲线。曲线显示,9700~8700 cal a BP期间海平面上升约11.6 m,海平面上升速率可达1.2 cm/a。现代潮滩不同位置沉积物粒度参数的规律性差异可作为潮滩微相识别的有效指标,为古潮滩沉积微相识别和古海平面重建提供参考依据。
