Formation of sand dune at Ao Bang Berd, Tambon Pakkhlong, Amphoe Pathio, Changwat Chumphon

Abstract

At Bang Berd Bay, a remarkable wind blown sand dune lies almost parallel to the present coastline with its highest elevation about 20 m above the present mean sea level. This study is aimed to characterize sand dune morphology and sedimentology for explaining its formation. As a result from aerial photograph interpretation, dune morphology shows a majority of parabolic and transverse patterns; whereas star shapes were rarely and locally recognized. Most of dune shapes indicate the direction of wind blown mainly from the east to the west. Dune texture is very homogenous and characterized by fine- to medium-grained sand mainly. Very rare micro-scale sedimentary structures have been observed from dune profiles. However, result from Ground Penetrating Radar (GPR) shows some obvious macro-scale sedimentary patterns, clear boundary of dune and the underlying prograded beach ridge plain. Reflecting configuration from GPR divided the depositional environment in this area into dune deposition (coastal sand dune (D1), cover sand (D2), marine deposition (beach ridge (B1), littoral deposits (B2) and channel filled (C). Based on macro-scale sedimentary patterns, lee and stoss angles of some burial dunes ascribed mainly major directions of wind from the east to the west. This result in analyzing wind direction based on GPR signals is corresponded well with dune morphology interpreted from aerial photographs. According to the morphology, geology and texture of dune, the possible sources of sand supply are thought to come from the sedimentary rocks formed as highland locating at the western part of the area. These rocks were eroded and transported to deposit and formed as alluvium substrate throughout the offshore during the early-Holocene transgression. The majority of dune started to deposit during dry condition of the middle Holocene and continued its formation to the late Holocene based on OSL datings.