The 10Be and Be contents of 22 of solid and solution) and that the equilibrium samples taken from seven locations in the Maurice constant is grain-size dependent. Manskaya and River-Union Lake system of southern New Jersey Drozdova [1968] speculate that the high Be are reported. Bulk 10Be contents range from 0.05 contents of certain coals may result from the to 2.7 dpm/kg and Be from<0.1 to 2 ppm. Silicate minerals separated from Union Lake sediments appear to have a constant surface concentration of 45 x 10 5 atom 10Be/cm2. Organic material is greatly enriched in Be: Hand-picked samples contain over 10 dpm/kg of 10Be and 5 ppm of Be.The deposition rate of 10Be in Union Lake is 41 atom/cm2s. •

We report the "Be and Be contents of 22 sediment samples of lacustrine silt from the Wilson Creek section of Mono Lake, California. The section spans about 20-35 kyr B P and contains a record of a geomagnetic excursion for which the relative palaeointensity is estimated from the ratio of natural remanent magnetization to anhysteretic remanent magnetization. The "Be contents of the excursion samples are somewhat higher than the average. of non-excursion samples (0.24 +_ 0.02 versus 0.15 * 0.02 dpm kg-'). It is clear however that geomagnetic effects are not the sole cause of the observed variations.