ABSTRACT
Ionium dating or uranium series disequilibrium dating has been applied successfully to calcareous lake deposits and speleothems. The method is based on the observation that thorium and thus also ionium is rapidly removed from solution by adsorption to solid surfaces and that natural waters therefore contain dissolved uranium, but virtually none of the decay product. Organic matter, and specifically peat, is well-known to strongly adsorb uranium from solution; ‘enrichment factors’ (absorption ratios) of 10000 have, for instance, been measured on peat. The correspondence between the two dating methods is sufficiently close to warrant further investigation of the method, especially since ionium dating can provide absolute ages for palynologically investigated peat layers back to 300 000 years BP.
