Abstract

The Cenozoic sediments of the eastern Kutai Basin, East Kalimantan, are composed of several deposystems that can be distinguished by their lithic successions and separated by disconformities evident on seismic records.

Five deposystems are separated into the following Groups with their subdivisions: the Pleistocene to Recent Mahakam Group, divided into the deltaic Handil Dua Formation to the west and the marine Attaka Formation to the east; the middle Miocene to Pliocene Kampong Baru Group, consisting of the deltaic Tanjung Batu Formation to the west and the marine Sepinggan Formation to the east; the middle Miocene Balikpapan Group, containing the uppermost carbonate to marine clastic Klandasan Tongue of the marine Gelingseh Formation and the paralicdeltaic beds of the Mentawir Formation; the early to middle Miocene Bebulu Group divided into a carbonate Maruat Formation and a deeper water clastic and carbonate Pulau Balang Formation, and the late Oligocene to early Miocene Pamaluan Formation.

These Groups and their subdivisions are described at their type and reference localities, and their inter-relationships and boundaries are discussed with vertical and horizontal sections.