Bể Phú Khánh nằm trên vùng biển miền Trung Việt Nam giới hạn trong khoảng kinh tuyến 109 độ-112 độ 30’E và vĩ tuyến 10 độ 30’-15 độ N. Khu vực bể Phú Khánh có một lịch sử phát triển địa chất trong Miocen rất phức tạp với 3 chu kì trầm tích: Miocen sớm (N1^1), Miocen giữa (N1^2) và Miocen muộn (N1^3). | VNU Journal of Science: Earth and Environmental Sciences, Vol. 35, No. 1 (2019) 71-93 Original article Evolution of Geological Structural and Sedimentary Environment Change in Miocene of Phu Khanh Basin Tran Thi Dung*, Tran Nghi, Chu Van Ngoi, Nguyen The Hung, Nguyen Thi Huyen Trang Faculty of Geology, VNU University of Science, 334 Nguyen Trai, Hanoi, Vietnam Received 13 February 2019 Revised 11 March 2019; Accepted 11 March 2019 Abstract: Phu Khanh basin located in the central Vietnam and bounded by the longitude of 109 o112oE and the latitude of 11o-15oN. The geological evolution history of the basin in Miocene is a very complicated, included three sedimentary cycles of Early Miocene (N 11), Middle Miocene (N12) and Late Miocene (N13). Each of these sedimentary cycles was generated and deformed by a general rule as follow: subsidence, sedimentary filling to be buried deeply and unconsolided sediments being become sedimentary rocks by diagenesis process and then continuously changed by catagenesis process. At the end of each cycle, the secondary basins were uplifted over the water surface and eroded to creat the angle or stratigraphic unconformities. Three strong deformation factors are faults, compressions, and volcanic activities. The study also demonstrated that the depositional formation of Phu Khanh basin in Miocene is existed three typical eroded surfaces as: (1) The top of early Miocene is an angle unconformity in the age of 16 million years, equivalent to the age of seafloor spreading in the East Vietnam Sea; (2) The top of middle Miocene is also an angle unconformity in the age of 11 million years and (3) The top of late Miocene is million years and this surface is both angle unconformity and stratigraphic boundary between Late Miocene and Pliocene - Quaternary sedimentary formations. The present geological structure of Phu Khanh basin is considered as the one of Pliocene - Quaternary dued to the control of East Sea Western fault system 1090-1100E
