Publications

The Central Sumatra Basin was formed during the Eocene - Oligocene as a series of north to northwest trending half-graben structures separated by horst blocks. These early half-graben structures were filled by non-marine clastic sediments of the Pematang Group in someparts of the deep trough. The Pematang group was divided into three formations: LowerRed Bed Formation, Brownshale Formation, with the Upper Red Bed Formation unconformably deposited on the top basement. This study aims to understand the depositional facies of the Pematang Group in the half-graben system better. Core data were used as the primary data, then well and seismic data were added to support this study. Facies description and stratigraphic analysis approaches can contribute in building a depositional facies model and in the sedimentary architecture. By integrating several existing data, the basement configuration is becoming deeper in the northwest part, represented by thicker sediment, and then becoming shallower in the southeastern part of the study area. Depositional facies model in the three formations of the Pematang Group show the crevassesplay, fan delta, floodplain, midchannelbar, transversebar, and alluvial fan facies associated with the fluvial facies that represented the Lowerand Upper Red Bed formations, while shallow and deep lacustrine deposits are representative of the Brownshale Formation.