• Journal of the Korean earth science society
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• v.22 no.5
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• pp.377-387
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• 2001

In order to elucidate sedimentation processes and depositional environments in transitional area between continental shelf and coastal zone, sedimentologic study has been done with 84 surface sediments sampled in nearshore/offshore off the mid-western coast of the Korean Peninsula for 3 years (1996${\sim}$1999). The surface sediment can be classified into 4 facies (gravelly sand, sand, silty sand and sandy silt). Mean grain size, sorting, skewenss and kurtosis varies -0.39${\sim}7.82{\Phi}$, 0.36${\sim}4.68{\Phi}$, -0.38${\sim}$0.86, -1.56${\sim}$3.43, respectively. The textural parameters show a finer-grained and poorly-sorted trend shoreward, northward and southward from the central part of the study area. The positively-skewed distribution and relationship of each textural parameters indicate a tide-dominated depositional environment. According to C/M diagram, there are 3 different domains (mode A, B, C) of sediment transport mode. The northern part is characterized by bedload transport (mode A) and represents co-influence of wave and tide, whereas domain C in the southern part is controlled by uniform suspension transport (mode C), correlating with sandy-silt area. In the broad middle area, transport processes are complex (the mixture of bedload, graded suspension and uniform suspension; mode B). Hence, the subdivision depositional environments of this study area may be classified by 3 depositional environments dependent on the interplay of sediment supplies from river, relict sediments and hydrologic conditions. In results, the nearshore and offshore areas are thus characterized as a mixing zone between coastal terrigenous sediments and relict sediments in the continental shelf by complex processes (tide, wave and river flow). These sedimentation processes play an important role in producing distinct sedimentologic features in the transitional zone linking coastal and shelfal areas.