Source to sink sedimentary systems are important settings of carbon cycling, serving as sites of carbon transfer between terrestrial and marine reservoirs, and as the primary locations for organic carbon burial on Earth. The age and character of the carbon that is buried at the terminal ends of these systems reflects the sources and transformations of the organic carbon (OC) throughout their linked terrestrial andmarine segments. Profound differences are observed between large passive and small active margin systems. Large passive margin systems are characterized by large floodplains and relatively broad shelves where OC has protracted exposure to oxidants. Rapid burial in prograding, subaqueous deltaic clinoforms or bypass to submarine fans, however, leads to high burial efficiency of terrestrial biospheric OC in some passive margin settings. The OC in small active margin systems, in contrast, follows relatively short pathways from headwaters to seabed. This rapid transit, facilitated by the important role of storm-driven transport in such settings, can lead to high OC burial efficiencies. The study of OC sources and transformations in contemporaneous source to sink sedimentary systems informs interpretations about the systems inwhich OCwas buried in the geologic past, their stratigraphic records of environmental change, and their potential to produce petroleum resources.