History of sea-level change of pak nam chumphon area, Amphoe Muang, Changwat Chumphon

Abstract

The study of coastal geomorphology at Pak Nam Chumphon area in this research is aimed to explain the historical of sea-level change in relation to coastal landform evolution. The coastal geomorphological map was constructed based on the aerial-photo interpretation. As a result, coastal landforms can be classified into 7 units as old sandy beach, old lagoon, young sandy beach, old tidal flat, upland and mountain, intertidal flat and tidal flat. The formation of beach ridges units presented in the area together with their thermoluminescence datings can be used in the construction of historical of sea-level change. The beach ridges can be divided into 3 parts as inner beach ridges, middle beach ridges and outer beach ridges. Beach ridges orientate nearly parallel to the shoreline but they reflect the difference in paleo-longshore current direction. Longshore current direction during the formation of inner ridge series was likely to northward direction ,but middle and outer ridges formed was likely in southward direction. Grain sizes from all beach ridge are fine to medium sand in general, whereas in swale (old lagoon), grain size is often characterized as sandy mud with peat fragments in some localities. Beach ridges show similarity in composition of quartz except the inner ridge its minor composition includes feldspar and ferromagnesian in greater number than those found in the middle and outer ridges. All of beach ridge sediments show high sphericity. Marine fossils indicate former tidal deposit, intertidal or mangrove environments. Based on TL dating of beach ridge sand, the three beach ridges in the study area are of the late Pleistocene to early Holocene.