Routing of terrestrial organic matter from the Congo River to the ultimate sink in the abyss: a mass balance approach André Dumont medallist lecture 2017

1. Introduction The riverine systems that extend from terrestrial drainage basins, across the continental margins, to the deep sea are major actors of the Earth's sedimentary cycle. They have also a fundamental role for the long-term carbon cycle regarding burial of terrestrial organic carbon in marine sediments (Schlunz & Schneider, 2000; Burdige, 2005; Galy et al., 2007; Hilton et al., 2008; Leithold et al., 2016) and hence for climate regulation. The annual global terrestrial organic matter burial is estimated between 40 and 60 Tg C with almost 75–85% deposited in the large-river deltas and the adjacent shelves (Berner, 1989; Hedges & Keil, 1995; Burdige, 2005). Nevertheless, a significant fraction of terrestrial organic carbon entering the ocean bypasses shelves and is transferred to the deep sea through submarine canyons (Monaco et al., 1990; Canals et al., 2006; Heussner et al., 2006; Sanchez-Vidal et al., 2012). However, it is still not clear to what extent the fraction of terrestrial organic carbon carried over to the deep-sea basin is buried and trapped on geological timescales. The organic carbon routing in present-day riverine systems is studied from the areas of its production to the areas of its burial, through mass balances, in the so-called source to sink (S2S) approaches. The efficiency of the transfer to the deep sea and subsequent trapping of terrestrial organic particles has been studied for small river systems with a direct connection to submarine canyons