Sedimentation in the Edsviken Bay

ABSTRACT

Mono-and stereoradiographs of sediment in rectangular coring tubes are used for core correlation and for quantifying contemporary variations in rates of sedimentation in Edsviken, a bay of the western Baltic Sea with annually laminated, modern deposits. Subsamples from one of the cores are used for evaluating the Pb-210 parameters and models in relation to the sedimentological conditions in the bay. The agreement between the X-ray results and the C.R.S. Pb-210 ages is good, although there is a major discrepancy between supported Pb-210 and Ra-226. Sediment focusing is the dominant explanation of the spatial variations in sedimentation rate in Edsviken Bay. The present rate of sedimentation in the deepest part of the bay is about three times higher than the average annual value for the bay, which amounts to 30 mg/cm². About half of the present sediment accumulation in the bay is probably due to the sediment yield from the drainage area. This ought to be the main reason why the unsupported Pb-210 flux of the Edsviken Bay is found to be a factor of two higher than the average annual atmospheric flux of Scandinavia, 0.15 ± 0.05 pCi/cm².