SOURCES, DISTRIBUTION AND FATE OF PARTICULATE ORGANIC MATTER ALONG THE FLY RIVER-GULF OF PAPUA LAND-OCEAN CONTINUUM

The Fly River-Gulf of Papua (FR-GoP) dispersal system is a tropical, mountainous river system chosen as one of the focus areas of the recent MARGINS Source-to-Sink program. The FR-GoP includes steep highland regions characterized by intense rainfall and rapid erosion, extensive lowlands with active river floodplains, a mesotidal delta and an actively accreting clinoform. A team of researchers from different institutions is carrying out interdisciplinary studies to investigate the erosion, transport, deposition and ultimate burial of particulate organic matter in this land-ocean continuum. A combined elemental, isotopic and biomarker approach has been applied to characterize the sources and composition of organic matter deposited along the FR-GoP dispersal system. This presentation is intended to provide a summary of the current findings linking biogeochemical cycles with physical and geomorphic processes on land and the coastal ocean. Specifically, it addresses the provenance and diagenetic state of the organic matter sequestered in sedimentary sinks along the dispersal system, including colluvial and alluvial soils in the uplands, floodplain sediments from the lowlands, as well coastal sediments from the delta and adjacent clinoform. The yields of terrigenous biomarkers (lignin and cutin products) as well as elemental and isotopic data are used to differentiate contributions of vegetation-derived organic matter from those of planktonic and petrogenic sources in different depositional settings. Combining insights into the processes of sediment accumulation with measurements of organic-matter loadings, the sequestration potential of different depositional environments along the FR-GoP dispersal system are assessed and these findings contrasted to current paradigms of sedimentary carbon sinks.