Fine sediment mineralogy as a tracer of latest Quaternary sediment delivery to a dynamic continental margin: Pandora Trough, Gulf of Papua, Papua New Guinea

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Sediment cores and geophysical data from the shelf and slope in the Pandora Trough and Gulf of Papua (GoP; Papua New Guinea, northern Coral Sea) have been studied to evaluate timing, pathways, and sources of sediment delivery to a muddy shelf-slope depositional system that developed during the late Quaternary marine transgression. Cores were analyzed for 14C geochronology, clay and bulk mineralogy, grain size, sedimentary fabric, and physical properties. Observations reveal a shelf-edge depocenter and adjacent middle-to-upper slope sediment wedge that each developed at different times from different sedimentary sources, despite close proximity along a down-slope gradient. Clay mineralogy of modern shelf sediments reveals strong longitudinal gradients that appear related to fluvial source composition. Similar gradients in source composition reveal heterogeneous and shifting sediment sources to the shelf and slope through time. From the Bølling-Allerød interstadial (14.5-12.5kyr BP), and the Younger Dryas (12.5-11.5kyr BP), fluvial sediments accumulated in a muddy inner shelf, forming a shelf-edge depocenter (core MV-41) with high kaolinite/chlorite values that are indicative of a local volcanic source, consistent with the geology of the nearby Lakekamu and Vailala river catchments. Shelf-edge sediment accumulation decreased from the time of Meltwater Pulse 1B (MWP-1B) to the present due to shelf flooding and inshore trapping of sediment. During MWP-1B, and possibly earlier, sediment transport west of MV-41 was steered obliquely offshore to the northern Pandora Trough continental margin upper/middle slope (MV-46 and MV-49). This transport has persisted nearly to the present, and has allowed for the development of a Holocene upper/middle slope sediment wedge (cores MV-46 and MV-49) that differs strongly in clay composition (and so source) from the adjacent up-slope shelf-edge depocenter (MV-41). Slope deposits have intermediate illite/smectite values similar to the central GoP, which differ from the very low illite/smectite values at MV-41. Such heterogeneous dispersal patterns oblique to seabed gradient are likely due to complex interactions of shelf processes with dynamic shelf morphology along the flooding GoP shelf, rather than a response solely due to rising sea-level and down-slope transport. © 2014 Elsevier B.V.

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Marine Geology

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