An unsuccesfull attempt at U/Th dating of soils calcretes from Doukkali area (western Morocco) and environmental implications

A large number of calcrete samples from topsoils of the Doukkali area, western Morocco, were studied by U-disequilibrium series methods. The 230Th/234U ages are rather uniformly distributed between4350 and 2ka BP. Homologous samples for occurrence and structure display quite different ages, the 230Th/ 234U ages are considered apparent. This is explained by repeated deposition of secondary calcite in the calcrete pores, which caused lowering of the original ages. However, the apparent ages may be considered minimum ages of the calcrete formation, indicating that calcium carbonate mobilization and deposition has been taking place repeatedly since4350ka. The age range obtained is quite comparable with that of calcretes from southern Spain, suggesting similar conditions for the calcrete formation in the two areas.