Structural controls on syn-rift sediments of the northern song hong basin

Abstract

The study area is located in the northern part of the Song Hong basin which is the largest basin along the western margin of the East Sea stretching from north of Hanoi underneath the Song Hong Delta (Red River Delta) into the Gulf of Tonkin (Figure 1). The rift system underneath the Song Hong basin constitutes a world-class example of how extrusion tectonics drives continental rifting and transtensional basin development.
Many factors strongly influence the structural styles of rifting of the northern Song Hong basin: rifting occurred during later Eocene - Late Oligocene time forced by ASRRSZ left lateral shearing; latest Oligocene - earliest Miocene transpression and inversion brought rifting to a halt, after which left-lateral shearing decreased. Paleogene rift systems extended along the trail of the ASRRSZ are now outlined by lower to mid-crustal metamorphic core complexes. Rift termination in the northern Song Hong basin and exhumation of the metamorphic core complexes coincided with cessation of Paleogene rifting along the western margin of the East Vietnam Sea and a common causal mechanism are speculated.
Structures within rifting affect syn-rift depositional patterns by creating sites of uplift and erosion, by controlling pathways of sediment transportation, by the accommodation space for sediment deposition and preservation. These resulting from the growth of rifting may yield a tripartite stratigraphy such as fluvial, deep lacustrine and shallow lacustrine.