Oligocene Cyclic Sedimentation Deduced from Taphonomic Analysis of Molluscs in Lacustrine Deposits of the Pematang Group, Pesada Well, Central Sumatra Basin - Aswan, Aswan; Department of Geological Engineering, Faculty of Earth Science Technology, Institut Teknologi Bandung (ITB), Jl. Ganesha 10, Bandung, 40132, Indonesia (ITB Journal Publisher, LPPM ITB, 2016)