Radiochemical dates obtained by alpha spectrometry on fossil mollusk shell from the 5e Atlantic shoreline of the High Atlas, Morocco

The reported radiochemical results obtained on 77 samples collected from Moroccan fossil beaches assumed to be deposited during the above present sea-level high stands corresponding to 5e climatic stage, and on 12 present and Holocene samples, are discussed in order to judge the age validity. Contrary to the Holocene shells where 238U contents are low and 234U/238U are in agreement with sea–water ratio, the 5e results vary considerably irrespective of species and calcite content of samples. Because of the open-system possibility, the 230Th/234U ages based on shell samples should be interpreted as minima for any studied shoreline discussed in the light of geological data and several shells analyses.