Abstract

The Phú Khánh Basin is filled up with thick Cenozoic sediments, deposited in varied environmental conditions. The Eocene (?) S1 sequence is formed mainly in high energy condition, consisting of predominated alluvial fan - fluvial lithofacies. The Oligocene S2 sequence is deposited in low energy lacustrine environment, composed mainly of fine-grained lithofacies of mudstones, coaly mudstone, coal and minor siltstone and sandstone, which may be an important hydrocarbon source rocks of the basin. Early Miocene S3 sequence is characterized by the transition from dominated continental condition to marine environment, with wide development of shallow shelf clastics and carbonate lithofacies, possibly becoming a significant hydrocarbon reservoir. Middle-Upper Miocene and Pliocene-Quarternary sequences are dominated by sediments in shallow shelf condition in the western part and eastward transition to major sediments of shelf slope and basin floor environments, which may play the role of reservoir and seal rocks of the basin.