Abstract

• The data obtained from the Oligocene Okhmintaung Formation in the Myasagaing-Shwemaungzun Area, the Minbu Sub-Basin, central Myanmar are observed, and then used to establish the depositional processes and environments, and to reconstruct depositional model of the research area. A total of fourteen lithofacies are recognized, and grouped into four facies associations: tidal channel, tidal sand bar, tidal flat and transgressive shelf. Based on studies of the facies and facies associations, the lower part of the Okhmintaung Formation may mainly be deposited in tidedominated estuarine system, which consist of a combination of tidal channel, tidal sand bar and tidal flat facies associations, and then followed by marine transgressive, resulting in deposition of alternating of transgressive shelf and tidal flat sequences in the upper part of the Okhmintaung Formation.