Subsurface Sediment Deposits of Tanjung Berikat Coast, Bangka, Determined from GPR Interpretation

Abstract

Tanjung Berikat Coast in Central Bangka, is a part of the Southeast Asian tin belt. We conducted four Ground-Penetrating Radar (GPR) survey lines and 13 hand auger coring to understand sediment deposition and composition. Two similar units were determined from GPR lines BLG 01-BLG 03: Unit A at the top part, reflected by parallel and continuous reflector configuration, weak-strong electromagnetic wave. Underneath Unit A is Unit B, characterized by subparallel configuration, not continuous-chaotic, weak-medium electromagnetic wave. Unit B is absent in BLG 04. We identify another two units from BLG 04 and BLG 03, Unit C, characterized by subparallel reflector configuration, not continuous- chaotic, weak-strong electromagnetic wave. It exhibits distinctive modulating contact with Unit D. Unit D is characterized by chaotic reflector configuration, relatively stronger electromagnetic wave that might be correlated to the granite intrusion Tanjung Klabat. Sediment deposit is composed of fine-coarse sand, consisting mostly of clastic plutonic and clastic biogenic (coral and mollusk fragments), which increase downward. This indicates marine-fluvial influence, which suggests that sea-level changes strongly influence sedimentation process. Unit A from GPR is correlated to these sediment deposits, the other three units might be correlated to weathering of older insitu deposit.