This project began as an attempt to establish the systematics of the stable isotopes of Be and Al in the oceans with a view to using their cosmogenic radio-isotopes as geochronologic tools. There is an explicit analogy here to C- 14. Carbon is involved in the biogeochemical cycle; hence the effect of decay on the distribution of the radio-isotope is overprinted by non-radiogenic processes. However the stable isotope C-12 is affected only by the biogenic processes and hence can be used to correct for their effects on the radio- isotope. The success of this approach is greatly facilitated by the fact that the carbon isotopes share a common, well-mixed reservior, the atmosphere. The latter is known not to be the case for Be and Al. The objective of this project is to establish whether the residence time and chemical behaviours of these elements in seawater is such that isotope equilibrium is achieved in the oceanic reserviour. If this were true then direct radiometric dating of marine sediments would be feasible in the range 0 to - 15 million years. Support is requested to continue investigations of the geochemical cycles of the isotopes of Be and Al with a view to developing them as geochronometers. It is proposed to participate in the South Atlantic Ventilation Experiment expedition to extend coverage into the South Atlantic and to examine the evolution of the isotope distributions as the Atlantic water masses propagate from their northern sources areas. Support is also requested for collaboration with Raisebeck's group in Orsay in a delineation of the continental cycles of the Be isotopes using our expertise and his dedicated Be-10 accelerator.
