Publications

A new regional paleogeography of the Kutai Basin during Tertiary is reconstructed based on the wealth of new field data and scattered updated publications to better understand the interaction amongst sedimentary provenance of different Tertiary basin substrate types, sedimentation styles, and stratigraphy architecture within the basin as a response to tectonic events. Data and information used are derived from published maps of gravity, magnetic, isopach, geologic, and significantly supported by outcrops and well information accompanied by biostratigraphic data. Kutai Basin is divided into Upper Kutai, Lower Kutai, and North Makassar Sub-basins. Their corresponding substrates are now perceived as the Northeast Schwaner Complex in the west, the North Meratus accreted mix continental-oceanic terrane in the middle, the North Makassar micro-continent in the east, and the Mangkaliat micro-continent in the northeast. The initial riftings of Kutai Basin were mostly the results of slab roll-back of the three subductions, e.g.: the northern continuation of Meratus subduction into the east of the Northeast Schwaner followed by docking of North Makassar micro-continent, the proto South China-Sea subduction into the Northeast Schwaner, and Banggai-Sula subduction into the North Makassar micro-continents. The timing of rifting was as early as Paleocene (60 Mya) and not later than Middle Eocene (45 Mya), depending of the relative position of the area within the basin to the respective plate interaction. * ETTI ** GDA Consulting, Jakarta There are five northeast-southwest trending highs and lows bounded by series of northwest-southeast transform faults making the architecture of overall Kutai Basin. The highs consist of: Teweh – Sampirang – Bangun Sari – Muyup Highs, Kahala – Kutai Lake – Kedang-Kepala Highs, Jonggon – Samarinda Highs, Balikappan – Mahakam High, and Makassar Highs. The first two highs have also been identified by several publications previously, but the last three highs are basically newly developed based on integrated method applied in this research. While during Middle to Late Eocene the Kutai basin experienced rifting and during Early Oligocene to early Late Oligocene the basins experienced sagging, paleogeography of the Upper and the Lower Kutai Sub-basins radically reshaped during late Late Oligocene to Early Miocene. Some the isolated highs were uplifted and formed the Kutai Island bounded by the marginal sea which separated it from the uplifted Paleogene sediments of the Upper Kutai Sub-basin. As consequences, sedimentologically, the provenance of the proto Mahakam Delta was derived from the Kutai Island, while the uplifted areas of the Embaluh and the Selangkai Groups and the Schwaner Complex were supplying sediment to the marginal seas in the Upper Kutai Sub-basin, surrounding the Kutai Island. During Middle miocene to Late Miocene, the Kutai Island was connected to the Upper Kutai Sub-basin, allowing sediment supply from the Embaluh and the Selangkai Groups, the Schwaner Complex and the Meratus Suture deposited in the Middle to Late Miocene coast of the Lower Kutai Sub-basin. Several implication related to the unexplored hydrocarbon plays are: 1) the Paleocene syn rift play in North Makassar Sub-basin, 2) the Eocene syn rift play in the Upper Kutai Subbasin, 3) the Oligocene reefal carbonates in the periphery of the Lower Kutai Sub-basin, 4) post rift shale gas on the western edge of the Lower Kutai Sub-basin, and 5) prograding Miocene deltas in the southern and northern borders of the basin.