## 6 Conclusions  
To investigate the patterns of sedimentary evolution in the Nakdong River delta related to Holocene sea-level change, we analyzed the sedimentary facies, grain size, and ages of ND-3 drill core sediments, and interpreted the sedimentary environment at each stage.  
1. A total of six sedimentary units (A, B, C, D, E, and F) were identified in the ND-3 core (46.60 m long) sediments. These classifications suggested that the Nakdong River delta contains a typical progradational sedimentary facies, starting from the late Pleistocene paleosol in the lowermost core sediments and migrating into the Holocene sediments characterized by shallow marine, prodelta, delta front, and the delta plain deposits toward the upper part of the core sediments.
2. For the study of different sediment distribution among the Nakdong River delta cores, we compared the ND-3 sediments with KND-3, and ND-2 core sediments, which are located at the same elevation as the ND-3 core sediments. We found that the sedimentary facies and grain size distributions are similar between the three cores. However, the ND-3 samples were found to be older than the ND-2 sediments. We also realized a relief in paleo-geomorphology between the ND-2, KND-3, and ND-3 cores through different paleosol observation levels. Unlike the muddy estuary sediments of the ND-2 and KND-3 core, the ND-3 core sediments contain a large amount of sandy sediments. The reason is that ND-3 core sediments were probably deposited at a bayhead delta environment.
3. The periodic growth process of the Nakdong River delta was reconstructed by referring the previous studies. At 10 cal ka BP, when transgression occurred because of a rapid increase in sea level up to 30 m below the current level, the coastline was located at the lower part of the present Nakdong River delta and the estuary's settings were formed at the ND-1, 2, 3, and KND-3 drilling sites. At 8-6 cal ka BP, sea-level rose abruptly and most of the current delta plains became submerged by seawater, changing into a continental shelf environment. After 6 cal ka BP, when the sea level was similar to the present level, most of the Gimhae Plain was located in a shallow marine environment and the terrestrial sediments supplied by the Nakdong River were prograded and deposited to form the initial Nakdong River delta system. After 2 cal ka BP, the delta sediments were prograded and deposited, and most of the delta was formed in the present shape of the delta and the delta plain environment.  
Conceptualization, E.J.J. and S.S.; methodology, E.J.J., J.C.K. and H.S.L.; formal analysis, E.J.J.; resources, D.C. and S.S.; writing--original draft preparation, E.J.J. and S.S.; writing--review and editing, D.C., S.S., J.C.K. and H.S.L.; visualization, E.J.J.; supervision, D.C.; funding acquisition, E.J.J. and D.C. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2019 RIA6A1A03033167). The study was also partly supported by Korea Environment Industry & Technology Institute(KEITI) through Measurement and Risk assessment Program for Management of Microplastics Program (or Project), funded by Korea Ministry of Environment (MOE) (2020003110010).  
Not applicable.