Provenance of Pleistocene–Holocene deepwater sediments in the Gulf of Papua (National Science Foundation Source to Sink Focus Area) has been studied to understand sediment sources and glacioeustatic influences on sedimentary routing and to better understand processes controlling sediment sources and delivery. We show how diverse processes operate in a complex deep-sea environment over time to control sediment routing and accumulation. Quantitative detrital analyses were conducted on 53 turbidite sand and 3 terrestrial samples with scanning electron microscopy and mineral liberation analysis, which yielded a broader and more insightful classification than manual point counts. We determined that (1) multiple terrestrial sediment sources along an approximately 500-km (300-mi) basin margin converged to form one continuous deep-sea system in two major basins (>30 cal [calibrated] ka); (2) subsequent sea level fall near the last glacial maximum (LGM) (18–22 cal ka) drove repartitioning of sediment sources to create multiple distinct depocenters, presumably caused by migration and incision of individual rivers across the newly exposed coastal plain; and (3) multiple separate deep-sea channels then regained compositional similarity near the end of the LGM. In the subsequent Holocene, deepwater sand transport shut down, except for one locality where delivery continues because of a combination of narrow shelf–slope setting, oceanographic processes, and additional volcanic supply. These findings highlight the diverse processes that must be considered for the development of deepwater petroleum systems, in terms of sediment delivery, deposition, and provenance that may affect the reservoir geometry and quality.