Cylindrical samples of sediments are obtained from 4 sea areas next to the Mirs Bay to the South China Sea. An N-type high purity germaium low background gamma spectrometry system has becn employed to measure the Pb-210 and the Cs-137 contents in the layered sam- plees.The sedimentation curves of Pb-210 and Cs-137 are acquired using the least squares fit method.The sedimentation rata at the four sampling sites are evaluated.our results show that the sedimentation rate decreases when the sampling sites are farther away from the Mirs Bay into the South China Sea

In particular

the rate calculated using the Pb-210 activities decreases from 0.46 to 0.27 cm/a

and that using the Cs-137 method from 0.38 to 0.10 cm/a

The Cs-137 method vields resuIts which are subiected to external disturbance to a greater extent

and is thus less reliable than the Pb-210 method.