Controls on sediment transport from rivers to trenches in passive and active continental margins

Active and passive continental margins exhibit significant differences in sediment transport. However, opportunities to quantify these specific sedimentary processes remain limited. The northeastern South China Sea hosts both active and passive continental margins, offering a distinct opportunity to compare the relative contributions from a large passive continental margin with those from a smaller but more dynamic active margin. We present detrital zircon U-Pb ages from marine sediments in the northeastern South China Sea to decipher their provenance and reveal the control of transport processes in the margins. Our results show varied provenance of sediments from the shelf to the trench. In the continental shelf, sediments were primarily derived from the Jiulong and Gaoping rivers, controlled by the topography and ocean currents in the passive margin. In contrast, the sediments in the submarine canyons predominantly originated from the Gaoping and Zhuoshui rivers in western Taiwan Island. Quantitative results indicate that the Gaoping submarine canyon provided approximately 86.2% of sediments to the Manila Trench by directly linking to the Gaoping River in the active margin. Based on the provenance results, we propose a distinct sedimentary process in the active and passive margins. In passive margins, sediments from drainage systems enter the shelf and are transported by ocean currents, but topographic highs often block these sediments, preventing them from reaching the deep sea. In contrast, active margins feature narrow shelves, which facilitate direct connections between submarine canyons and river mouths, allowing gravity flows to carry sediments directly to the trenches. Our study provides an understanding of the sediments transported from rivers to trenches in the northeastern South China Sea and highlights the controls (ocean currents, dramatic topography, and gravity flows) during the sediment transport in the continental margins.