Early diagenetic cycling, incineration, and burial of sedimentary organic carbon in the central Gulf of Papua (Papua New Guinea)
Article first published online: 12 JAN 2008
Copyright 2008 by the American Geophysical Union.
Journal of Geophysical Research: Earth Surface (2003–2012)
Volume 113, Issue F1, March 2008
How to Cite
2008), Early diagenetic cycling, incineration, and burial of sedimentary organic carbon in the central Gulf of Papua (Papua New Guinea), J. Geophys. Res., 113, F01S09, doi:10.1029/2006JF000689., , and (
- Issue published online: 12 JAN 2008
- Article first published online: 12 JAN 2008
- Manuscript Accepted: 31 MAY 2007
- Manuscript Revised: 23 MAR 2007
- Manuscript Received: 15 SEP 2006
- early diagenesis;
- carbon remineralization;
- carbon burial
 The clinoform complex of the Gulf of Papua represents a major deltaic system in Oceania. Two seasons largely control seafloor dynamics and sedimentary C cycling: the relatively quiescent NW monsoon, and the SE trades, characterized by remobilization and reoxidation of topset deposits. Surface sediments (∼20 cm) are reactive with ΣCO2 production fluxes ∼35–42 mmol m−2 d−1 at mangrove channel and topset sites during the monsoon, and ∼10–20 mmol m−2 d−1 on the foreset-bottomset (>40 m). Fluxes decrease by a factor of ∼0.3 on the topset during the transition period and trades. The 13,14C isotopic compositions of pore water ΣCO2 reveal diagenetic fractionation, with dominant utilization of young (Δ14C = 1.4–31.1‰), terrestrial C substrates inshore (channels, topset δ13C = −29 to −25‰) and a progressive increase of young marine C sources seaward (outer topset, foreset; bottomset δ13C = −22.2 to −19.5). Remineralization patterns of terrestrial and marine Corg demonstrate cross-shelf exchange. Multiple tracers show that a suboxic, mobile mud layer, ∼10–60 cm thick (usually ∼10–30 cm), characterizes the central gulf topset and Umuda Valley off the Fly River and unconformably overlies methanic deposits releasing old ΣCO2 (Δ14C = −159 to −229‰). Residual terrestrial Corg delivered to the bioturbated foreset continues to be remineralized slowly, generating ΣCO2 having net Δ14C = −270 within sediments deposited 100–200 years ago. The reactivity of Corg below ∼0.5 m in the foreset is ∼10–20 times lower than expected based on accumulation rates, reflecting loss of >50% of sedimentary Corg on the topset, which functions as a suboxic incinerator.