Preliminary Analysis Results of Internal Sedimentary Structures of the Coastal Frontal-Dune at the Hujeong Beach, the East Sea of Korea

Abstract

As a part of the Study of environmental variation along the middle coast of the East Sea program of KORDI, field surveys were conducted to examine internal sedimentary structures of a coastal frontal-dune with ?2 m in height at the Hujeong Beach, located at the front of the East Sea Research Institute of KORDI, the East Sea of Korea. At the field the cross-sectional profile of the fore dune was examined and nine sediment samples were collected from the bed layers of it. The cross-sectional dune profile was more in detail described combining with photo images taken at the field and grain-size analysis results of the sediment samples. As a preliminary result, Internal sedimentary structures of the dune are mainly distinguished by three facies of S1, S2 and S3 that consist of cross-bedding sand layers with different dip angles and directions: 3.0∘, -5.7∘ and 5.6∘ from the dune base to the top, respectively. The average bed thicknesses is ?4 cm at the facies S1, located at the base of the dune, and decrease to ?2 cm at the facies S2 of the middle part of the dune. The facies S3 located at the uppermost of the dune have the thinnest average bed thickness of ?1 cm. Regardless of the facies, their sands are moderately well sorted with a range of 0.2 phi to -0.1 phi in mean grain size. All the facies have a similar bedding sequence characterized by alternating very coarse sand and coarse sand beds, indicating the fore-dune bed layer forming was mainly influenced by alternation of two different physical processes. Based on the results, as a next step, our study will focus on understanding the two physical processes at the beach and the late Quaternary coastal depositional-environments of the East Sea.