Characteristics of geological structure of deep sea area in the Vietnamese East Sea based on seismic interpretation

Nguyễn Thế Tiệp, Trần Đăng Hùng, Nguyễn Thế Hùng, Trần Hữu Thân

 Deep-water sea area of the East Sea belongs to the Exclusive Economic Zone (EEZ) of Việt Nam, therefore its study has a very important significance on the sovereignity and marine economic development planning. It is also the principal constituent of Vietnamese East Sea with a very complex tectono-structural characteristic and undergone various tectonic stages during Cenozoic.

The study area is composed of different structural zones with the distribution, thickness, sedimentary composition, faulting and folding characterizing the extentional zone of passive marginal sea. Cenozoic sedimentary formations of great thickness were formed in diversified in time and space environments. Tectono-sedimentary evolution controled the hydrocarbon system of deep-sea region. Eocene(?)-Oligocene syn-tectonic sequences distributed mainly in graben and half-graben structures were deposited mainly in dominant lacustrine medium, favoring the occurrence of organism-rich fine-grained facies, regarded as important hydrocarbon source rocks. Lower-Middle Miocene sequences are characterized by transitional facies from dominant continental conditions to marine medium with wide development of carbonate platform and reefal facies, which may become a significant reservoir. Fine-grained facies of Upper Miocene - Pliocene post-rift sequences formed in transgressive and high system tracts may play the role of regional seals.

The results of seismic interpretation allows us to divide the deep-water region of East Sea into 10 different tectono-structural zones. These zones were formed and developed through three extensive tectonic stages, such as Cretaceous-Paleocene pre-rift, Eocene(?)-Middle Miocene syn-rift and Late Miocene-Quaternary post-rift stages.   


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