Structure of Pliocene-Quaternary formation in the southwest subbasin of the Vietnam’s
East Sea and its significance in investigation of ferromanganese nodules and crust

Nguyễn Văn Vượng, Lê Duy Bách, Lường Thị Thu Hoài Phạm Nguyễn Hà Vũ,

Nguyễn Đ́nh Nguyên,Phan Thanh Tùng, Nguyễn Thế Hùng, Hoàng Thị Phương Thảo

Pliocene-Quaternary formations in the southwest sub-basin of the Vietnam’s East Sea were developed at the junction of tectonic units including Phan Rang shelf, Tuy Ḥa shear zone, south of Phú Khánh basin, the thinned crust of SW sub-basin, differentiated high structures of north Huyền Trân bank and Đá Lát-Đá Tây reefs, the Măng Cầu high structure and the northern part of Nam Côn Sơn basin. The thickness of the Pliocene-Quaternary formation in the study area ranges from 0 to 1.600 m. Based on the characteristics of the seismic reflection in different profiles, they are divided into 6 areas. Area 1 is filled with horizontal and parallel organic material-bearing clays and silts. Silty clay mixed with the sand of area 2 developed on the continental slope. Silty-clay and mud of area 3 were characterized by chevron fold and strike-slip minor faults. Region 4 is an area of disturbed and disordered silty clay mixed with carbonate sediment. Region 5 is the abyssal plain featured by parallel layered of silty-clays. Region 6 is abyssal plain silty-clay and mud mixed with volcanic materials.

The area of abyssal plain with parallel bedding sedimentations in the thinned crust of SW sub-basin has the potential of ferromanganese nodules. The seamounts located at the depths from -500 to -800 m and in the areas of disturbed, disordered and of folded sedimentary layers have the potential of ferromanganese crusts.

Keywords: Southwesrtern sub-basin of Vietnam’s East Sea; Tectonics; Ferromanganese crust, Ferromanganese nodules;Pliocene-Quaternary.