EOCENE-MIDDLE MIOCENE STRUCTURAL RECONSTRUCTION OF THE DURI ANTICLINE, CENTRAL SUMATRA BASIN, INDONESIA

摘要

There are at least four different structural events that formed the Central Sumatra Basin throughout its development. It consist of basement development (Pre-Tertiary), rifting (Eocene-Oligocene), strike-slip (Middle Miocene), and compression (Middle Miocene-Recent). Each of its products is overlapping one to another and, some of the next deformation has reactivated the previous structural product resulting in a new structural pattern. Therefore, it is important to recognize the pattern that has been formed in each event to obtain a complete comprehension of the geological development in the Central Sumatera Basin, especially of the Duri Anticline by reconstructing each period of the deformation event. This paper will try to reconstruct the deformation that formed during Eocene-Middle Miocene by using available seismic data. The method used in this paper is flattening method provided by IESX program from Geoframe, Schlumberger. By using this method, all of the event beneath the flatten line is pulled up by the same distance as the chosen horizon been flattened from its original position. The reconstruction is made base on assumption that the end of sedimentation in each period of deformation is flatted; therefore, the flattening method is able to reconstruct the condition back to its deformation time. The top of Pematang Group was flattened to reconstruct the rifting phase (Eocene-Oligocene) and the top of Sand 240' (Duri Fm., Sihapas Group) to reconstruct the strike-slip phase in Duri Anticline. The flattening method enabled the determination of which faults were active during each period of deformation, to recognize the reactivated faults and the pattern that was caused by the reactivation, and finally to propose a reconstruction of the structural event in each period of deformation.