Late Cretaceous and Cenozoic tectono-stratigraphic development of the East Java Sea Basin, Indonesia

The East Java Sea Basin is underlain by a metamorphic basement complex. Subsidence of this basement during the Late Cretaceous resulted in accumulation of up to 3 km of marine Upper Cretaceous sediments (megasequence 1). Contraction and near peneplanation of the Upper Cretaceous sediments and underlying basement occurred before the middle Early Eocene, producing a regional unconformity which defines the base of megasequence 2. The Cenozoic East Java Sea Basin started to form during the Early Eocene by crustal extension on both planar normal faults and extensionally reactivated Cretaceous thrusts. Normal faulting was pulsed from the Early Eocene to Early Oligocene and affected a progressively larger area with time. Complex structural geometries evolved in response to local extensional reactivation of obliquely orientated pre-existing structures.

The resultant Palaeogene fault-controlled sub-basins were filled with fluvial, coastal plain and shelf clastic and carbonate sediments recording an overall transgressive evolution. Regional subsidence became dominant over fault-controlled subsidence during the Early Oligocene. Basin-fill during this time was dominated by deep marine, fine-grained clastic sediments. A regional unconformity of intra-Oligocene age is recognized and is overlain by Oligocene to lowermost Miocene deep water calcareous mudrocks and limestones which locally onlap erosionally truncated Eocene rocks. The Lower Eocene to lowermost Miocene sediment package comprises megasequence 2.

Regional inversion of Palaeogene sub-basins commenced in the Early Miocene and continues to the present day. The syn-inversion Lower Miocene to Recent sediments comprise megasequence 3. Inversion has resulted from regional contraction and resultant reverse reactivation of Palaeogene normal faults and Cretaceous thrusts. Regional subsidence has been continuous during the inversion history, resulting in a gradual reversal of depocentre location; Palaeogene depocentres became Neogene highs, whereas Palaeogene platforms became Neogene depocentres. Miocene deposition during inversion was dominated by the alternation of fine-grained carbonate-dominated and clastic-dominated cycles. Subsequent Pliocene sandstone deposition followed fluvial incision during an Early Pliocene lowstand. The depositional history, during the Pleistocene to Recent, records rapid relative sea-level changes; progradation of clastic and carbonate sediments, erosional truncation, channelling and slumping.

The Tertiary structural geometrical evolution and preserved sediment distribution can be explained by dominantly dip-slip fault movement during the extensional and contractional phases of basin development and deformation. Basin-scale cross-sectional geometries similar to classical positive flower structures have evolved by the reverse reactivation of a geometrically complex extensional fault system.