A COMPARISON OF PERALS(R) TO ALPHA-SPECTROMETRY AND BETA-COUNTING - AMEASURE OF THE SEDIMENTATION-RATE IN A COASTAL BASIN

PERALS method (Photon/Electron-Rejecting Alpha Liquid Scintillation) i s given by its constructor as a quick and accurate method for alpha nu clide counting. With an adapted sample preparation, the separation and alpha counting efficiency would be close to 100%. In this study, we i ntend to assess its potential applied to recent geochronology. Using t he Po-210/Pb-210 method, we carried out the dating of two cores sample d in the Thau basin (southern France). In the aim to test the reproduc ibility and the accuracy, several types of standardized materials (art ificial tracers and natural soil samples) were previously analyzed. Th e chemical preparation of solid samples, already described by Case and McDowell [1], has been slightly adapted for our sediments. An interco mparison with the standard techniques currently used (spontaneous depo sition of Po-210 Onto silver disks measured by alpha spectrometry and beta counting of Bi-210) has allowed to confirm the potentialities of the method and the equipment. The precision of the analyses was +/-5%. Results obtained on two cores from the Thau basin allow us to measure sedimentation rates of 0.166 and 0.238 cm yr(-1).