Bulletin of the Marine Geology, Vol. 27, No. 1, June 2012, pp. 7 to 18 Seafloor Sediment Characteristics and Heavy Mineral Occurences at Betumpak Cape and Adjacent Area, Bangka Strait, Bangka Belitung Province Karakteristik Sedimen Permukaan Dasar Laut dan Keberadaan Mineral Berat di Tanjung Betumpak dan Sekitarnya, Selat Bangka, Provinsi Bangka Belitung Edi Rohendi and Noor Cahyo Dwi Aryanto* Marine Geological Institute, Jl. Dr. Junjunan No. 236 Bandung-40174, Indonesia Email: *
[email protected] (Received 30 January 2012; in revised form 8 May 2012; accepted 21 May 2012) ABSTRACT: Thirty seafloor of sediment samples have been taken by using gravity corer and grab sampler at Betumpak Cape, and adjacent area of Bangka Belitung. The result of grain size analyses show that there are four sediment units: gravelly sand, gravelly muddy sand, silt and silty sand. Identification of Scanning Electron Microscope (SEM) image on several samples shows the presence of clay mineral such as smectite, alunite, chlorite etc., may resulted from plagioclase weathering of granite. Based on heavy mineral analyses, its highest content is found at MTK-27 (northwest of Betumpak Cape). High content of apatite (0.94% wt and 1.07% wt) is found on coarse sand fractions (115-170 mesh) at MTK-29 (northeast Ular Cape) and MTK-30 (north of Ular Cape). Generally, the heavy mineral accumulation is occurred on medium sand fraction (60-80 mesh) as magnetite (7.86% wt), ilmenite (4.9% wt) and zircon (1.32% wt). Based on these data, it shows that heavy mineral is accumulated on medium to coarse sand. Key words: sea floor sediment, grain size analysis, heavy minerals, and Betumpak Cape, Bangka strait.