Publications

Paleogene sediments of the North Sumatra Basin (NSB) contain important source rocks. The current widely understood paleogeographic model delineates that the sediments originated from the Malacca Platform. Meucampli Formation is one of the Paleogene Sediments derived from the Sumatra continent and was widely distributed within the basin prior to the uplift of Barisan Mountains. This phenomenon is contrary to the current model and implies that the Sumatra continent was the sediment provenance since its occurrence in the Mesozoic. Besides paleogeographic models, the complex geological setting of the NSB is characterized by north-south trending grabens that were formed during the Eocene. The initiated extensional force however, remains uncertain. In this study, the evolution of NSB since Paleogene is analyzed based on a systematic review of publications, outcrop study, free-air gravity data, and detailed structural lineaments from geological maps, subsurface maps, and ALOS PALSAR satellite images. From geological map, overall normal faults at northern part of the basin are observed to show two trends of lineament: NW-SE in the onshore and N-S in the offshore. The southern part of the basin has NNW-SSE trend in the onshore and N-S trend in the subsurface. Fold structures in the southern part exhibit NW-SE trend, while the northern part is dominated by E-W trend. It is difficult to trace the diapiric anticline in the north. This implies the insignificant role of strike-slip fault in northern part of the basin. Analysis of structural lineament using ALOS PALSAR Images reveal that NSB can be divided into four regions. Area 1 to Area 3 structural lineaments cover the same area with Eocene paleo–highs and lows. The N-S trend is only well preserved in the low areas, as in Area-2. This signifies the Eocene structure had experienced structural overprinting and rotation due to the Sumatran Strike-slip Fault. It is believed that the initiation of North Sumatra grabens was greatly affected by the pre-existing N-S trending basement structure. During the Eocene roll-back of the Sumatran Trench, the rifting phase of the North Sumatra Basin was aligned with the pre-existing N-S structures (Khlong Marui & Ranong Fault). It is also concluded that Eocene rifting occurred without involving strike-slip faults. In this paper, we propose some new underexplored plays, such as: Transgressive sandstone of Bampo and Belumai Formation, Middle Baong and Keutapang Sandstone pinching to mud diapir, Tampur Carbonate, and Pre-Tertiary Play.