Evolution of fluvio-estuarine system in response to sea-level changes since MIS 6, southeastern Korea

The MIS 6 deposits in coastal regions are important in determining evolution of depositional systems over one cycle in response to sea-level changes. It is known to be the most extensive glaciation with weathering and erosional processes since about 400 ka. However, it is difficult to preserve whole deposits, despite weathering and erosional processes during the glacial periods. We carefully conducted core analyses of sedimentary facies, grain size, and age dating from two cores. This study reconstructed the development of an incised-valley fill in response to sea-level changes since the late Pleistocene. Seven facies associations are defined in the cores: braided river, tributary channel and land swamp, mud flat to marsh, fluvial channel and floodplain, central basin to bayhead prodelta, bayhead delta front, and bayhead delta plain. Stratigraphy and evolution of the Nakdong incised-valley fill can be divided into five stages since the Penultimate Glacial Maximum. Over all sedimentary analyses indicate that depositional environments of each stage are corresponding to relationships between sediment supplies and accommodation spaces in response to the sea-level changes in the Nakdong incised-valley system. The Nakdong incised-valley fills also note that fluvial environments occurred in an incised-valley system during Last Glacial Maximum periods. It can be possible to reveal a fully depositional history more than one cycle through two glacial traces. Additionally, the biased geomorphology influenced the architecture and preservation of the Nakdong incised-valley deposits characterized by asymmetric development of depositional successions since the Penultimate Glacial Maximum.