Tectonostratigraphic analysis and depositional pattern of South Palembang sub-basin, South Sumatra Basin

Abstract

South Sumatra Basin is divided into several sub-basins, one of which is the South Palembang Sub-Basin. Tectonostratigraphic analysis on South Palembang Sub-Basin was conducted to determine the history of sedimentation and tectonic history. Methods consist of the integration of mudlog, well log, checkshot and seismic data. Qualitatively, litofasies analysis is done from well log data and mudlog data. Well seismic ties on seismic data used checkshot and well log data. Picking layer and faults interpretation was conducted on the seismic data to create a depth structure and isopach map in each formation. Tectonostratigraphy analysis in this research area included basement, Lemat, Talang Akar, Baturaja, and Gumai Formations. Determination of formation boundaries was based on rock characteristics and stratigraphic seismic patterns. The South Palembang Sub-Basin was formed by three tectonic phases since the Mesozoic and structural reactivation during the Plio-Plistocene. The changes in the sedimentary environment were occurring from the Lemat to the Gumai Formation and showed a deepening pattern that indicates a further shift towards the ocean occurring during a rise in sea level. The Talang Akar Formation is deposited in braided fluvial environments up to the prodelta. The Baturaja Formation is sedimented on the carbonate environment, and the Gumai Formation is precipitated in a deepwater environment. Extensional tectonic processes in the late Cretaceous to early Miocene affected the Lemat and Talang Akar formations. The structure that controls the deposition of the Lemat Formation and Talang Akar Formation is the South Palembang 1(SP1) fault, which is an inverse fault with NNW-SSE direction. The Lemat and Talang Akar Formation are syn-rift deposits, as is indicated by the thickening of the hanging-wall of SP1 fault. That thickening was not found in Baturaja and Gumai Formations, indicating the post-rift deposits.