Abstract
We investigate the relaxation dynamics of a dense monolayer of bidisperse beads by analyzing the experimental data previously obtained in a fluidized bed. We demonstrate that dynamical facilitation becomes less conserved and plays a lesser role for the structural relaxation when approaching the glass transition. We first show that the dynamics obeys the same elementary processes as those previously reported in a cyclic shear experiment: cage jumps aggregate on a very short time into clusters. We then show that increasing the packing fraction makes the spatio-temporal organization of these clusters evolve from a rather scattered and random distribution towards a collection of sparse and finite avalanche events.