FLEXURE CONTROL OF ACCOMMODATION SPACE IN A MODERN FORELAND BASIN: NW SHELF OF AUSTRALIA, TIMOR SEA

Asymmetrical flexure of the lithosphere during evolution of foreland basins results in asynchronous relative sea level fluctuations within the same basin. Local marine transgressions and regressions are found in areas where the plate is initially deflected, while eustasy remains as the primary control of marine cycles in areas with no significant deflection. Comparison between the accommodation space created by sediment and water loading, adjusted for eustasy, compaction and the stratigraphic thickness of marine cycles are used to evaluate the geodynamic evolution of the late Neogene peripheral foreland basin in Timor Sea along the North West Shelf of Australia. Seismostratigraphic data is the main constraint to evaluate marine trasgressive-regressive third order cycles and to develop flexural models that represent the deflective history of the basin. During Late Miocene to Early Pliocene times, about 500 km the Australian lithosphere in the Timor Sea was deflected. Throughout this period, four marine cycles are recognized along the Australian Platform in west Timor, however, stratigraphic records also indicate that only two marine cycles are found in east Timor. The rate of subsidence due to vertical loading is up to four times higher than the rate of eustatic fluctuations. Therefore, accommodation space in Timor Sea during the evolution of the foreland basin was primarily controlled by tectonics.