"Geomorphological Process and Change of Fan Terraces in Jeonnam, Korea – A Case Study of the Damyang Daejeon and Jangheung Fan Terraces –"

This study analyzes and investigates geomorphological process and change of the Damyang Daejeon and Jangheung fan terraces with sedimentary facies analysis and OSL age dating. 3 levels of the Damyang Daejeon fan terrace are recognized, and fan terrace 3 consists of sandy mud sediments including angular to sub-rounded gravels with on OSL age of 91±4 ka. The Jangheung fan terrace can be divided into 2 levels, while fan terrace 2 is considered as an erosional surface of fan terrace 3 consisting of very poorly sorted sandy mud sediments including angular to sub-rounded gravels with an OSL age of 89.6±6.5 ka. These results suggest formative age of approximately 90 ka, corresponding to period of intense summer monsoon. Therefore, both fan terraces 3 can be attributed to temporary deposits of a large amount of water flow and sediments from landslide during intense summer monsoon. The Damyang Daejeon and Jangheung fan terraces 3 indicate incision rates of 0.171 m/ka and 0.111 m/ka, respectively, and these low incision rates can be attributed to geographical proximity to uplift axes. Distance from coast and elevation are considered to be responsible for difference in incision rate between fan terraces 3. Dissection rates from fan terraces 3 indicate that active dissection coincides with active incision.