Li-Be-B measurements using SIMS

Yet, the astrophysical site of ^10^Be nucleosynthesis is uncertain. We report Li-Be-B isotope measurements of CAIs from CV chondrites, including CAIs that formed with the canonical ^26^Al/^27^Al ratio of ~5x10^-5^ (canonical CAIs) and CAIs with Fractionation and Unidentified Nuclear isotope effects (FUN-CAIs) characterized by ^26^Al/^27^Al ratios much lower than the canonical value.

Our measurements demonstrate the presence of four distinct fossil ^10^Be/^9^Be isochrons, lower in the FUN-CAIs than in the canonical CAIs, and variable within these classes. Given that FUN-CAI precursors escaped evaporation-recondensation prior to evaporative melting, we suggest that the ^10^Be/^9^Be ratio recorded by FUN-CAIs represents a baseline level present in presolar material inherited from the protosolar molecular cloud, generated via enhanced trapping of galactic cosmic rays.