Tectonic-sedimentary evolution in a Palaeocene rifted Lishui Sag, East China Sea Shelf Basin

Abstract

Influenced by episodic tectonic activity and multiple sediment sources, the source-to-sink systems in rifted basins are relatively complex. Based on seismic data, well logging, cores, thin sections, and heavy mineral data, the growth and linkage of the Lingfeng fault were reconstructed and its influence on the sedimentary responses of the Palaeocene-rifted Lishui Sag in the East China Sea Shelf Basin was examined. The researchers conducted a fault throw-distance analysis on the Lingfeng fault and found that it displayed an overall weak-strong-weak evolutionary process. During the early syn-rift stage, the Lingfeng fault exhibited a segmented geometry consisting of seven fault segments with low fault activity along its strike, and small-scale source-to-sink systems developed in both the hanging wall dip-slope and footwall. As the main syn-rift stage progressed, strong fault activity induced large-scale exposure of the source area, resulting in a high sediment-supply rate and large-scale source-to-sink systems. During the late syn-rift stage, the fault weakened and evolved into a connected basin-boundary fault, and proximal source-to-sink systems in the footwall gradually disappeared. Semi-quantitative measurements of the geomorphic parameters of these source-to-sink systems indicated wide and shallow sediment transport pathways in hanging wall dip-slope areas (average width and depth of approximately 6.34 kmand 0.13 km, respectively) and narrow and deep sediment transport pathways in the footwall (average width and depth of approximately 3.75 km and 0.15 km, respectively). The semi-quantitative statistical analysis implies that the cross-sectional area of the transport channels was positively correlated with the corresponding fan/delta complexes in a rift basin.