Clay minerals and gravels of late Pleistocene interstadial coastal sediments above the current sea level, south coast of Korea

Abstract:

At nowadays, the severe greenhouse effect causes rapid sea level rise around the Korea Peninsula. Paleo-climate researches have been concentrating on hydrological activities during the mid-Holocene optimum and the last interglacial period to use the paleo-analogues data in predicting the future hydrological environments. The previous studies on the late Pleistocene interstadial coastal sediments have primarily been biased towards the terraces of the east coast in the Korean Peninsula. According to the results, the last interglacial marine terraces of the east coast were existed at 18 m in elevation. Uplift rate of them was presumed to be 0.1mm/year (Choi, 2006). Also, the stratigraphy of the Quaternary coastal deposits of the Yellow Sea has been suggested by Park et al. (1998) and Lim et al. (2003). In recent, Jang et al. (2014) reported the OSL dated Eemian marine deposit along the southwest coast of Korea. However, the age-equivalent outcrops of the south coast are not discovered yet.

The first outcrops of the late Pleistocene interstadial coastal sediment above the present sea level were discovered at IJin-ri site of Haenam, south coast of Korea. It would be very useful for calculating the rates of Eemian sea level rise and uplift of south coast of Korea. 62 cubic samples were collected at 6 cm intervals from the section (4.8-8.83m in elevation). Four sedimentary units, from Unit 1 to 4 in ascending order, are distinguished based on sedimentary textures and grain size distribution as follows: Unit 1 (sand, 4.8 m-5.32 m in elevation), Unit 2 (silty clay, 5.32 m-6.8 m in elevation), Unit 3 (gravelly sand, 6.8m-7.8m in elevation) and, Unit 4(sandy gravel, 7.8m-8.83m in elevation). The sediments which included rounded or semi-rounded gravels are thought to be transported from marine. Also, the assemblages of clay minerals from the sections are similar to those of Yellow Sea. It shows the possibility that the sediments originated from marine during high sea level stage of Eemian and/or storm surge.