| 利用沉积物粒度数据反演沉积水动力参数 |
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| 引用本文： | 周蒂.利用沉积物粒度数据反演沉积水动力参数[J].地质科学,1999,34(1):49-58. |
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| 作者姓名： | 周蒂 |
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| 作者单位： | 中国科学院南海海洋研究所, 广州 510301 |
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| 摘 要： | 波罗的海西部达斯浅滩海底沉积物各粒级的空间分布由物源区向外有规律变化,反映出沉积水动力条件的控制作用,反过来也为根据沉积物各粒级的空间分布反演近海底优势水流方向和速度提供了依据。利用沉积水动力经验公式及分选系数梯度、Z统计量等设计了反演优势流向和流速的方法,并应用于该海区,估计了该区海底以上1m的近海底优势水流方向及优势流速。与有限的实测及模拟资料进行对比,估计的海流模式吻合较好,但流速的数值可能总体上偏高,需要用更多实测资料来校正和标定。
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| 关 键 词： | 沉积水动力学 沉积物粒度 波罗的海达斯浅滩 |
| 收稿时间： | 1997-08-25 |
| 修稿时间： | 1997-08-25; |
THE ESTIMATION OF SEDIMENTARY HYDRODYNAMIC PARAMETERS FROM SEDIMENT GRAIN SIZE DATA |
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| Zhou Di.THE ESTIMATION OF SEDIMENTARY HYDRODYNAMIC PARAMETERS FROM SEDIMENT GRAIN SIZE DATA[J].Chinese Journal of Geology,1999,34(1):49-58. |
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| Authors: | Zhou Di |
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| Institution: | South China Sea Institute of Oceanolgy, Chinese Academy of Sciences, Guangzhou 510301 |
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| Abstract: | The Darss Sill is the southern part of a narrow outlet of the western Baltic Sea. 1340 sediment samples were collected from the sea bottom and analyzed for 8 grain-size fractions.Concentration contours of these fractions show a clear pattern of sediment dispersion from the source area outwards.This demonstrates the strong control of sedimentary hydrodynamics on grain-size distributions and provides a possibility for the estimation of sedimentary hydrodynamic parameters from grain-size data. Dominant near bottom flow directions were approximated by gradient vectors of the sediment sorting(standard deviations of grain-size distributins)and by the Z-test method proposed by McLaren and Bowles(1985).Resulting pattern agreses with each other and with that sugested by previous understanding of the area. The sharp contrast in areal distribution of various grain-size intervals indicates that an abrupt change from erosion transportation to deposition occurs between the intervals of of medium fine sand and fine sand,corresponding to the grain-size of 0.2 mm and a ratio between settling and friction velocities of 0.72. Method was devised to estimate near bottom flow velocityy from the pattern of grain transportation.For a given grain-size interval,the critical shear stress τ c for moving grains was calculated by empirical equation of Chepil(1959)or by the entrainment function of Shields(1936).Then the flow velocity at 1m above seabed was calculated from von Karman Prandtl equations(Dyer,1986).A turbulence factor T was introduced to take care of the variation of near bottom shear stress.Assuming that the shear stress is subject to a normal distribution, T =2.5 and T =2.0 correspond respectively to the 1% and 5% probability that shear stress exceeds the critical value,indicating respectively the onset and mass movement of sediment grains in the interval.Further assuming these two situations are represented roughly by 1% and 5% content contours of the interval,then maps of estimated flow velocity at 1m above seabed were constructed. The good similarity and compatibility of velocity contours given by 1% and 5% contours of various grain-size intervals,as well as the comparison of estimated pattern with limited observations suggest that the estimated flow dirction and velocity may be accepted as an approximation to the long-term flow pattern.More reliable estimation may be obtained through calibrations with more observations and experiments. |
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| Keywords: | Sedimentary hydrodynamics Sediment grain size Darss Sill of the Baltic Sea |
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