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The Tertiary Kutei and Northwest Borneo basins contain more than 40,000 feet of clastic and carbonate rocks and sediments in the thickest part. Isopachous mapping indicates that the Kutei basin and the Melawi- Ketungau area were connected during the Paleogene and that the Melawi-Ketungau area was open to the Northwest Borneo basin at that time. The Schwaner Block of southwest Kalimantan and the Kuching A.rch/High of central Borneo yielded sediments at varying rates throughout the Tertiary to the Kutei and Northwest Borneo basins.Paleogene deposition was predominantly transgressive except in the Melawi-Ketungau area where it was regressive. The greatest development of carbonate in Kalimantan during the Paleogene was centered on the Barito and Paternoster platforms. During the Neogene regressive deposition from deltaic complexes filled much of the Kutei and Northwest Borneo basins while carbonate deposition continued on the Paternoster platform. The Meratus graben, which received sediment from Eocene through Middle Miocene, was uplifted, folded and faulted during Middle to Late Neogene.The eastern part of Sundaland was rifted into several microcontinental masses during the latest Cretaceous to Early Paleogene and the intervening rifts were filled with clastic sediments derived from the uplifted highs. Obduction in the area that is now Sabah accompanied northwesterly rotation which uplifted the Kuching High and resulted in deposition of second generation regressive sediments to the north and south. This uplift also provided the impetus for gravitational folds to develop in the flanking basins. It is these gravitational folds which contain the bulk of oil in the Northwest Borneo and Kutei basins. This counter-clockwise rotation was essentially accomplished by the Middle Tertiary.A subsequent obduction in the Late Neogene which overthrust oceanic crust onto east Sulawesi, partially closed the Meratus graben.