Two virtually undisturbed cores collected by using the crust-freezing technique revealed the occurrence of varved sediments in the Kalix River estuary. Sedimentation rates were determined by super(137)Cs measurements, varve-counting and also by sediment traps. Each varve consists of a grey, predominantly clastic spring flood layer and a brown layer relatively rich in Fe (III) oxides, deposited during the rest of the year. The varve thickness is 5-13 mm, corresponding to a sedimentation rate of 96-227 mg dry sediment/cm super(2)/yr. Fall-out from the Chernobyl accident resulted in a 7-10 fold increase of super(137)Cs in the layer deposited during the summer and autumn of 1986. During the period 1975-1991, one or two major resuspension events occurred in the estuary