Plutons (bodies of granite and related rocks) formed by cooling of big magma chambers should be assembled and cooled in geologically short time periods (say, <1 million years). But precise uranium-lead (U-Pb) dating of Yosemite granites by Coleman and students revealed assembly and cooling times more like 10 million years. This requires that the plutons were assembled piecemeal.

These findings, published in 2004 (Glazner et al., 2004; Coleman et al., 2004) challenged many core concepts about how such systems work and were highly controversial at the time.