The late Quaternary deep-sea depositional system in the Gulf of Papua: linking source, dynamic sedimentation process and depositional architecture

Abstract

This study was undertaken to explore interactions among eustatic sea level change, fluvial sediment supply, oceanic processes, and seabed morphodynamics, and their controls on delivery of terrestrial sediments to the deep sea, using the Gulf of Papua (GoP), between New Guinea and Australia, as a natural laboratory. The GoP is a 500 km wide embayment that contains excellent examples of adjacent passive and active terrestrial-oceanic margins with multiple sources of terrestrial and neritic carbonate sediments. This work examines source to sink sediment delivery from river systems to the slope and deep-sea basins of the GoP, over the last ~40 ky, at millennial temporal resolution and finer. The results offer new insights into the development of sedimentary successions in deep-sea basins, and also into approaches for provenance analysis. Mapping and integration of acoustic facies with core physical properties, sedimentary fabric, and chronostratigraphy allows placement of seafloor evolution into a well-defined temporal framework. Chronological constraints permit an assessment of changes in sediment supply and depositional environments across time and space, from marine isotope stage (MIS) 3 to MIS 1. Sand provenance provides additional insights regarding sediment sources and routing. In summary, the study yields a narrative of sediment delivery along a ~500 km basin margin that is more complex than initially imagined. The sediment delivery to and conduit connectivity between deep-sea basins evolves over time due to the combined effects of eustasy, oceanic processes, and dynamic seabed morphology. Multiple terrestrial sediment sources along a ~500 km basin margin initially converge to form one continuous deep-sea system of channels and two major basins prior to 30 ky BP, that become bathymetrically separated by a large mass-transport deposit. Subsequent sea-level fall approaching the late glacial maximum (LGM) initially drives re-partitioning of sediment sources to create multiple compositionally distinct depocentres, presumably due to migration and incision of individual rivers across the newly exposed coastal plain. Multiple separate deep-sea channels then regain compositional similarity near the end of the LGM, due to regional erosion into compositionally similar catchment rocks. Furthermore sand transport shuts down, except for one depocentre (MV22), fed by local volcanic, that remains active at least into the Middle Holocene.