Abstract

The Balikpapan Formation of Middle Miocene age has been interpreted as deltaic deposits with a large extension throughout East Kalimantan's Kutai Basin. It has proven to be one of the main objectives in the basin. Previous regional geologic models show the formation deposited by the ancient Mahakam deltaic system and developed from the depocenter, around the present Mahakam Delta area, to the north and south basin margins.

New analysis of the Balikpapan Formation in the Sangatta Field of the northern Kutai Basin concludes a single development of deltaic systems, the ancient Sangatta Delta, separated from the ancient Mahakam Delta in the south. The separation is obviously emphasized by an ideal and proper fan configuration laterally bounded by coastal deposits south of the Sangatta area. The main channel direction of the system ranges from west to northwest of the Sangatta area and the distributary systems built the delta fan facing to the east. The fan configurations depicted a constructional delta influenced by fluvial and tidal processes. The ancient Sangatta Delta developed relatively continuously during the geological history of Balikpapan Formation in this area.

This ancient Sangatta Delta model was derived mainly by reanalysis of intervals in the Balikpapan Formation of the Sangatta Field and selected according to predominant facies similarity in the same prograding or retrograding event.