We have obtained the first beryllium measurements of late F/early G–type stars in the old open cluster M67 ( 4.5 Gyr ) and in the intermediate age cluster IC~4651 ( 1.7 Gyr ) .
One member of the young cluster IC~2391 ( \sim 50 Myr ) was also observed .
Our sample stars have effective temperatures within a range of +30 – +380 K from the solar temperature .
All our sample stars , including the Sun and the young cluster star have , within the errors , the same Be abundance .
This result implies that late F/early G–type stars undergo very little ( if any ) Be depletion during their main-sequence life-time .
Since these stars have undergone some Li depletion , our finding is indicative of shallow mixing , i.e .
of a mixing process that can transport surface material deep enough for Li burning to occur , but not deep enough for Be burning .
As shown in previous studies , the Li vs. Be diagram is a powerful diagnostic of stellar interiors .
In this context , we do not find any evidence of correlated Li and Be depletion ; furthermore , a comparison with various models shows that the Be pattern of our sample stars is compatible only with models including gravity waves .
This class of models , however , can not reproduce the Li observations of M 67 .