The deep offshore portion Tarakan Basin is relatively under-explored. Only a few wells have been drilled that resulted in 3 hydrocarbon discoveries. The basin has been filled by a large deltaic and associated deep marine systems that began to develop during the Paleogene with extension and rifting, followed by Neogene subsidence and accumulation of up to 10000 meters of deltaic to deep-marine sediment. Well logs, cores, 2D and 3D seismic and biostratigraphic data have been used to reconstruct

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... e structural and depositional evolution of the deep water portion of the basin, where the recent Tarakan's deep water discoveries are located. As result, it was recognized that a series of rapid sea level drops occurred in Middle Miocene to Pliocene in relation with the exposure and erosions of the western part of the basin. This events lead, in the eastern deep offshore portion of the basin, to the deposition of sand-rich turbiditic deposits along the slope and the basin floor.