Tentative reconstructions show that the development of these Late Miocene-Quaternary basin-floor fan systems was dominated by changes of sediment supply. The Xisha fan reached its largest extent during the Late Miocene, while the Pearl River fan was most active during the Late Miocene to Quaternary. During the Late Miocene, both the conduits of the Central Canyon and the Pearl River Canyon were active with abundant sediment supply, generating the two incipient fan systems. Sediment supply from the west via the Central Canyon persisted throughout the Late Miocene, being coarser-grained than that of the Pearl River fan. With the demise of the Central Canyon during the Pliocene and consequent sharp decrease in sediment supply, the Xisha fan size reduced significantly. By contrast, supply of mud-rich sediments from the Pearl River and northern slope increased through the Pliocene and into the Quaternary, leading to the modern sedimentary pattern of interdigitating basin-floor fans. Insights into the evolution of sediment supply and fan development through time derived in this study contribute to a better understanding of how source to sink systems feed marginal oceanic basins such as the South China Sea.