Amy Gough & Robert Hall
The Eocene-Miocene deposits of the Central Sumatra Basin were deposited in similar environments to those of the South Sumatra Basin. A comprehensive study into the clastic sediments of the Pematang and Sihapas formations of the Central Sumatra Basin will allow comparisons between the basins to be drawn, as well as any connectivity to be analysed. This will be achieved through a provenance study, including classical field data, a heavy mineral study, and single-grain geochronology.
The Central Sumatra Basin sits towards the east of the Barisan Mountain Chain, which forms the ‘back-bone’ of Sumatra. Like the South Sumatra Basin, it is considered to be a ‘back-arc’ basin, despite the fact it pre-dates the development of the Sumatran Arc. Throughout the Eocene-Oligocene these eastern basins were in a ‘horst and graben’ stage of development, creating smaller depocentres for sediment accumulation. These deep-rift basins allowed for deposition of Pematang alluvial and fluvial systems shed from localised highs, which interacted with basin-centre lacustrine environments, mimicking the deposits found in the SSB.
By the Miocene the Sihapas Formation had begun being deposited. At this point, smaller sub-basins had reached a state of overfill and sediments were deposited in a series of proximal fans, braided fluvial systems, and marginal marine environments. It is possible that these depositional environments were connected to the environments found in the SSB before the uplift of the Tigapuluh Mountains.