Periodic variation in natural radioactivity of lake Bouchet sediments

Low level counting of alpha and beta particles has been carried out on a 5 long sediment core from the lake La Bouchet in France, spanning the past around 24 000 years. A total of around 60 data points were spectrally analysed with the successive approximations method. Several whole or quasi-periodicities were located for the two radioactivity data sets, in different time intervals; for the alpha counting, periods of 1000–1200, 2000, 6000 and 24 000 years and for the beta counting periods of 1000, 3000, 4000, 8000 and 24 000 years were obtained. The non-stationarity nature of the obtained periods are discussed in relation to (a) palaeoclimatic fluctuations impact on mineral carrying natural radiosotopes partitioning of the sediment deposition of the last glacial and (b) other solar-terrestrial agents.