Diurnal laminations in the varved sediment of Lake Lovojärvi, south Finland

A man-induced extensive silty layer in the sediment of Lake Lovojärvi, dating back to the year 1960, contained 18 laminations due to rhythmical variations in the size classes of the mineral particles. A good agreement was found between the thicknesses of the successive laminae, and one period in a sequence of arbitrary 'wind sums' calculated from the meteorological statistics of the spring 1960 for periods of winds exceeding 3 m/s. Most of these wind pulses were diurnal; the longest one lasted for five days. The deposition of the layer in early spring was further confirmed through diatom analysis, which revealed within the laminated sequence a diatom succession typical of Lake Lovojärvi immediately after the melting of ice in spring