LAUSR

Abstract Sedimentary organic carbon in the Arctic, including the continental shelf and fjords, has been relatively well investigated, whereas much less is known about sedimentary inorganic carbon (carbonates) in fjords. The distribution and provenience of both carbon fractions in a high-Arctic fjord (Kongsfjorden, 79°N) was the subject of this study. Sediment cores and suspended particulate matter were analyzed for total, organic, and inorganic carbon as well as calcium, magnesium, and strontium. The sediments were dated using the radiolead method. Sedimentation rates ranged from 1.3 mm (fjord mouth, FM) to several cm (close to the glacier front, GF) year−1. Organic carbon contents were higher at the FM (~ 20 mg g−1) than at the GF (~ 1 mg g−1), while contents of inorganic carbon were lower at the FM (16.8 mg g−1) than at the GF (45 mg g−1). Suspended particulate matter concentrations were highest, and carbonates most abundant close to the GF. The data suggest that organic carbon is mostly produced in situ, with glaciers serving as only a minor source. Calculated dependences indicated that carbonates close to the GF are of terrigenous origin and those at the FM almost exclusively biogenic. Carbonates originating from these two sources differ in their composition.