MODEL PERKEMBANGAN STRUKTUR PALEOGEN DI SUB CEKUNGAN AMAN UTARA, CEKUNGAN SUMATRA TENGAH

• Main Author: , Indrawardana
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/6281
• Institution: Institut Teknologi Bandung

North Aman sub-basin is located in the northern part of Central Sumatra basin which is separated from North Sumatra basin by Asahan arch. North Aman subbasin is interpreted as a pull-apart basin with the characteristics is similar to other Central Sumatra sub-basins. Understanding of depositional environment within Central Sumatra Basin is still having a lot of question. From previous observers about Central Sumatra Basin still have no detail study on Paleogen Pematang Group using tectonostratigraphic concept approach especially on Paleogen’s rift architecture development in North Aman sub-basin. This research is to understand Paleogen’s rift architecture development in North Aman sub-basin by using tectonostratigraphic concept. Seismic stratigraphy is a geologic approach to the stratigraphic interpretation from seismic data. Seismic reflection surfaces are represent bedding surfaces which follow chronostratigraphic correlation By identifying lateral termination of seismic reflection, depositional sequence boundaries can be recognized. Combined with other seismic appearances such as seismic reflection configuration and its geometry shapes, seismic facies can be described and mapped. Further analysis of seismic facies using available well datqa will help interpretation process to predict the depositional facies within the basin. In the research area of North Aman sub-basin is able to identified five (5) sedimentation sequences which the formation processes related to border fault activities in Pleogen’s rift sub-basin development. Early process of sub-basin formation in rift initiation period occurred sedimentation of Pematang-1 sequence. This sequence sedimentation process was caused by rapid subsidence due to active faulting of pre-existing basement structure. Following rift initiation period was sedimentation process of early syn-rift period. Sedimentation process in this period was Pematang-2 sequence sedimentation and the process was initiated by increasing tectonic activities following by quite big rapid subsidence at the end of Pematang-1 sequence period sedimentation. Following early syn-rift period was sedimentation process of middle syn-rift period. Sedimentation in this period was Pematang-3 sequence sedimentation and the process was initiated by decreasing tectonic activities following by moderated subsidence. Following middle syn-rift period was sedimentation process of late syn-rift period. Sedimentation in this period was Pematang-4 sequence sedimentation and the process was initiated by decreasing tectonic activities following by slow subsidence. Final sedimentation process in North Aman sub-basin was Pematangiv 5 sequence sedimentation process. The process of this sequence sedimentation was in the period of post rift and initiated by decreasing subsidence in all over area with low topography. From restoration calculation, extension factor (????) of North Aman sub-basin is 1,29 with strain average for sequence Pematang-1 is 3.8%, for sequence Pematang-2 is 3.1%, for sequence Pematang-3 is 3.0%, for sequence Pematang-4 is 2.8%, and for sequence Pematang-5 is 1.4%. Decreasing the activity of main fault from early rifting period to end of rifting period indicated by decreasing the average of the strain showed different response to the geometry and depocenter of Paleogen’s rift.