Nghiên cứu cho thấy rằng trong thành tạo trầm tích Miocen bể Phú Khánh có 3 mặt bào mòn tiêu biểu: Nóc Miocen sớm là bất chỉnh hợp góc có tuổi 16 triệu năm tương đương với tuổi dừng tách giãn đáy Biển Đông; nóc Miocen giữa cũng là bất chỉnh hợp góc có tuổi 11 triệu năm; nóc Miocen muộn có tuổi 5,5 triệu năm vừa có bất chỉnh hợp địa tầng vừa có bất chỉnh hợp góc giữa Miocen và Pliocen - Đệ Tứ. | 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 of Vietnam and bounded by the longitude of 109o-112oE and the latitude of 11o-15oN. The geological evolution history of the basin in Miocene is very complicated included three sedimentary cycles of Early Miocene N11 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 unconsolidated 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 create 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 due to the control of East Sea Western fault system 1090-1100E in the longitudinal direction and .
