Carbon 14 dating of carbonate rocks in arid zones: corrections and uncertainties

The validity of the Munnich-Vogel model for carbon-14 dating is questioned, even for the temperate zone. In the arid zone, extra difficulties arise such as soils with low humus content, lakes which are merely exits of very 'old' groundwaters, and water-mixing which occurs in large aquifers (e.g. Tibesti, Syrtes Basin, 'albienne' groundwater). The case of areas without limestone is discussed and they also need minor correction. A Munnich-Vogel type correction is suggested, but it must be made to vary in agreement with the river basin, and be accompanied by a large uncertainty bandwidth. (author)