우라늄系列 非平衡 年代測定法과 韓半島 南海 上白島 現生 堆積層의 年代測定에 關한 硏究

U-series disequilibrium dating and its application to the recent sediment dating from Sangback-do, southern sea of Korean peninsula

Uranium-thorium separation technique from shallow sediment and α-source electrode-position technique are established in the present work, and uranium series disequilibrium dating method is applied to the quaternary piston core from Sangback-do, South Sea of Korean Peninsula. The age of the piston core (depth 200~300cm) sampled from Latitude 34°06′37″, Longitude 127°37′37″ was determined as ranging from 9.0±2.2 to 22.9±3.3Ky B.P, i.e., Later Pleistocene, older than Holocene which was stratigraphically known in the previous study. The sedimentation rate in the area is regularly increased according to the depth of the sedimentation layer. Except a few split sections of the piston core the sedimentation rates are avarage 7.2cm/1,000 years. Where sedimentation layer is deeper, then sedimentation rate tend to be slower. It must be pointed in age calculation that initial ²³⁰Th/²³⁴U radioactivity ratio is much influenced when detrital material was introduced in the sample. The ²³⁰Th/²³⁴U activity ratio measured in the present work is 0.06 at ²³²Th=0, and this value shows higher analytical errors because of the low-radioactivity of ²³⁰Th in the samples.