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ABSTRACT: Evolution Of the Kutei Basin, East Kalimantan, Indonesia

Hickman, Robert G., Charles Stuart, and Tim Seeley , Unocal Corp, Sugar Land, TX

Tectonism and sedimentation were linked during development of the Kutei basin. In the Eocene and Oligocene, rift basins with non-marine to marine sediments developed above a Cretaceous accretionary prism in the region from E. Kalimantan to S. Sulewesi. In the late Oligocene and earliest Miocene, subsidence led to formation of carbonate banks and reefs flanking shale-prone basins.

In the late early Miocene, collision of micro-plates with E. Sulewesi and subduction beneath N. Borneo, related to c-clockwise rotation of Borneo produced regional compression and formation of opposing thrust belts in Borneo and Sulawesi. In Kalimantan, Paleogene rifts were inverted. The uplifts supplied sediment to deltas that prograded to the present coast by early middle Miocene time. Continued regional shortening caused thrust decollements to extend eastward folding the overlying Miocene deltaics. The center of deltaic activity was near the present-day Mahakam delta, with episodes during which sedimentation shifted to the north or south.

The offshore Kutei basin lies between the Pater Noster Platform (PNP) and the Mangkalihat Peninsula and is characterized by detached deformation. Depositional patterns caused a tri-partite structural division of the basin. In the Mahakam depocenter a series of large, low relief detached folds developed successively at former shelf breaks. North and south of the depocenter, linked growth faults and toe thrusts developed. The driving force of this deformation was deltaic loading, but faults join the regional decollement. The linked fault systems die out toward the central fold belt. In the S. zone, the linked faults terminate to the south against the Adang fault zone. To the north, the thrusts are uplifted along the deformed zone of the right-lateral Sangkulirang Bay fault, which accommodates shortening between Borneo and Suluwesi.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia