Whole‐Rock Geochemistry and Detrital Zircon Provenance Constraints on the Paleogene–Neogene Source‐To‐Sink Evolution of Northern Borneo (Sabah), Southern South China Sea

ABSTRACT Northern Borneo provides a key archive of how convergent‑margin processes and drainage reorganization shaped the southern South China Sea margin from the Paleogene to the Neogene. This study integrates whole‑rock major–trace element data from Rajang–Crocker and Neogene successions in Sabah with detrital zircon U–Pb age spectra to reconstruct source‑to‑sink evolution and to evaluate the relative contribution of first‑cycle and recycled sediment sources. Paleogene to Lower Miocene formations are dominated by sand and mud‐rich submarine‑fan and slope deposits associated with the sedimentation along the evolving Proto‐South China Sea (PSCS) margin and subsequently incorporated into the northern Borneo accretionary–orogenic system, whereas overlying Neogene units preserve tide‑ and storm‑influenced fluvio‑deltaic and shallow‑marine systems within successor basins. Whole‐rock geochemistry indicates predominantly evolved upper‐crustal and recycled sedimentary components, with CIA values recording variable degrees of chemical alteration and compositional maturity among formations. Zr/Sc–Th/Sc relationships reveal variable source composition and sediment maturity, reflecting differences in zircon enrichment, recycling intensity, and sediment sorting. Detrital zircon age distributions contain recurring Early Cretaceous and Permian–Triassic populations together with variable Palaeozoic and Precambrian components, indicating persistent regional source contributions and changing proportions of inherited and recycled sediment components through time. These integrated proxies support a long‐lived mixed provenance system involving Sundaland and adjacent continental terranes, Cretaceous magmatic provinces in Borneo, recycling of older Rajang–Crocker successions, and subordinate local inputs. These results demonstrate that Paleogene–Neogene basin evolution was controlled by progressive reorganization of sediment‐routing pathways, uplift, recycling, and basin development during regional tectonic change, providing new constraints on the source‐to‐sink evolution of northern Borneo and its relationship with the southern South China Sea margin.