NEOGENE TO QUATERNARY STRUCTURAL EVOLUTION IN THE OFFSHORE TANIMBAR REGION IN THE SOUTHERN BANDA OUTER ARC: IMPLICATIONS FOR PETROLEUM SYSTEM IN EASTERN INDONESIA

摘要

The Banda Outer Arc in Eastern Indonesia is characterized by a complex fold-thrust-belt composed largely of Australian passive margin sequences. The area covered by this study is the offshore Tanimbar region in the Southern Banda Outer Arc including the Babar Selaru block. The structural framework in this area consists of multiple normal fault trends and thrust complexes resulting from a complex structural evolution history. This paper aims to make clear the mechanism and kinematics of the structural evolution, particularly fold-thrust-belt development from the Neogene to the Quaternary, using recently acquired INPEX Babar Selaru (IBS) 3D broadband seismic data and 2D/3D structural restoration in the study area. The structural framework in the study area mainly consists of the following five fault families: 1. Northeast-southwest trending normal faults are dominant in the southern area of the IBS 3D seismic data coverage, mainly formed by flexural bending of the Australian Plate in an extensional stress regime. 2. A south-verging thin-skinned thrust system is widely distributed with west-east axes throughout the northern area of the IBS 3D seismic data coverage, formed in a compressional stress regime. 3. West-east trending decollement separates the northern thrust system and the southern northeast-southwest trending normal faults that cut across the Cenozoic sequences in the south and deepen to the north into the Mesozoic sequences in the Southern Banda Outer Arc. 4. West dipping north-northeast to south-southwest trending normal faults with a sinistral strike-slip component cut across the thrusts and the northeast-southwest trending normal faults. 5. Reactivated north dipping west-east trending normal faults beneath the decollement and the Timor-Tanimbar Trough that are interpreted to have developed originally during the Late Palaeozoic to Mesozoic. These were activated or reactivated as a result of oblique collision between the Australian continental margin and the Banda Arc during the Pliocene to Quaternary, a part of them is considered to be activated or reactivated simultaneously. This complex structural evolution during the Neogene to Quaternary substantially affects the present day seabed topography and the petroleum system in this area.