Geomorphic Development of the Kajo Basin

加祚盆地의 地形發達

Several fluvial terraces were developed in the Kajo Basin located in Kochang-gun, Kyongsangnam-do, Korea. The peat layers are formed on a fluvial terrace of them. To clarify the geomorphic development of this basin, a detailed classification of geomorphic surfaces, a soil profile study, grain size analysis, pollen analysis of the peat layers and C-14 dating were made. The main findings are as follows: 1) The Kajo Basin was formed by a differential erosion of granic rocks. The surrounding mountains are contact-metamorphosed gneiss and sedimentary rocks. 2) Seven geomorphic surfaces were recognized. They are named the H1, H2, M1, M2, T, L1 and L2 surfaces, from older to younger. 3) C-14 dating and the pollen analysis indicate that the L1 surface was formed during the Early Wurm Glacial. 4) The formation periods of the L2, M and H surfaces are supposed to be the Late Wurm, Riss and Mindel glacial, respectively, on the basis of the color of soil horizons (with or without the Red Soil) and the weathering degree of gravels. 5) Betula and Pices were dominant in the pollen of the Kajo Basin around 30,000 years B.P.

1) 加祚盆地는 花岡岩이 貫入한 地域이 侵蝕되는 과정상에서 熱接觸變質을 받은 주변 地質은 侵蝕에 저항하여 山地로 남고, 중앙의 花岡岩은 쉽게 침식을 받아 盆地底가 된 花岡岩의 侵蝕盆地이다. 2) 盆地底에는 形成시기를 달리하는 7개의 지형면을 분류할 수 있었으며, 이들은 오래된 것부터 高位1, 2面, 中位1, 2面, T面, 低位1, 2面으로 분류되었다. 3) 低位1面은 Carbon dating 및 花盆分析에 의하여 Early Wurm氷期에 형성된 것이 판명되었다. 4) 低位1面을 編年의 基準面으로 하고, 土壤의 土色(赤色土의 分布 여부), 礫의 風化度를 考慮하여 高位面은 Mindel氷期에, 中位面은 Riss氷期에, 低位2面은 late Wurm氷期에 對應하여 형성된 地形面으로 推定되었다. 5) 30,000年B.P.경에 加祚盆地의 植生은 Betula가 優占種이었으며, Picea도 높은 出現率을 보였다.