Abstract

The Upper Mesozoic Dương Đông synthem in Southwestern Việt Nam is an unconformity-bounded unit, which was established based on the International Stratigraphic Guide. It consist of Hàm Ninh formation (K₂hn) in the upper part (distributed on Phú Quốc island, An Thới archipelago and offshore), Thổ Chu formation (K₁tc) in the middle part (distributed on Thổ Chu and An Thới archipelagoes, Phú Quốc island and offshore) and probably clastics underline Thổ Chu formation (not exposed yet), which have parallel bedding that unconformably covered on the Upper Paleozoic - Lower Mesozoic formations. The Upper Mesozoic Dương Đông synthem had undergone compression, uplift and strong erosion, forming longitudinal and NW-SE anticlines, synclines and fault systems, and regional angular