  Understanding the details of how the red sequence is built is a key question
in galaxy evolution. What are the relative roles of gas-rich vs. dry mergers,
major vs. minor mergers or galaxy mergers vs. gas accretion? In Wild et al.
2009 we compare hydrodynamic simulations with observations to show how gas-rich
major mergers result in galaxies with strong post-starburst spectral features,
a population of galaxies easily identified in the real Universe using optical
spectra. Using spectra from the VVDS deep survey with z~0.7, and a principal
component analysis technique to provide indices with high enough SNR, we find
that 40% of the mass flux onto the red-sequence could enter through a strong
post-starburst phase, and thus through gas-rich major mergers. The deeper
samples provided by next generation galaxy redshift surveys will allow us to
observe the primary physical processes responsible for the shut-down in
starformation and build-up of the red sequence.
