Accumulation of barium in recent Skagerrak sediments: sources and distribution controls

Geochemical and mineralogical methods have been applied to document the Ba and barite distributions in the Skagerrak sediments. Barite, released in the central North Sea during hydrocarbon drilling as a component of the drilling mud is a principal carrier of Ba in the recent Skagerrak sediments. The systematic pattern of the surface Ba contents, displaying a generally decreasing trend from south to north is consistent with the barite transport from the North Sea towards the Skagerrak. The predominant barite grain size ranges between 10 and 20 μm. The sub-surface Ba distribution is characterised by the elevated contents within the top 5–10 cm, which downward is followed by uniformly low contents. Considering the sedimentation rate, the start of sub-surface Ba enrichment generally corresponds to the late 1960s, coinciding with the beginning of off-shore drilling in the North Sea. In addition to the primary depositional factors controlling the shallow stratigraphic Ba distribution, the influence of diagenetic processes is suggested by the dissolution features on the barite grain surfaces and the profile relationships to the interpreted diagenetic zones.